Browse Topic: Chassis stiffness

Items (269)

Influence of Roll Gap Control under Acceleration Conditions

2026-99-0867

7/30/2026

During the cold rolling process, when the rolling speed enters the acceleration stage, the rolling force often exhibits a linear decline accompanied by fluctuations. This leads to a decrease in the uniformity of steel strip thickness distribution, resulting in the failure of the outgoing strip to meet quality requirements in terms of shape and thickness. In this paper, a three-dimensional model of a six-high rolling mill is established using Abaqus, and the influence of gap control during the acceleration stage on strip shape is systematically investigated. By analyzing the relationship between rolling force and roll gap variations, a gap compensation strategy based on a dynamic stiffness model is proposed. Simulation results demonstrate that implementing gap compensation during the acceleration stage effectively improves the consistency of strip thickness, with significant reductions in both thickness range and standard deviation.

Tang, Yingxin, Yan, Zhuwen, Cao, Wenjun, Wu, Jiawei

Analysis of Structural Stiffness Indicators of Manned Lunar Vehicles

2026-99-1827

7/17/2026

The structural stiffness of a manned lunar vehicle is a core indicator ensuring its stable operation in the complex lunar environment. The vehicle’s body structure must meet multiple requirements, including high stiffness, lightweight design, and adaptability to lunar surface conditions. Since lunar gravity is only 1/6 of Earth’s and the terrain is rugged and dusty, the body structure must employ a high-stiffness design to withstand driving impacts and resist deformation, thereby preventing mechanical failures or safety hazards for crew members caused by excessive structural distortion. However, excessive structural stiffness would result in an overweight vehicle body, conflicting with the spacecraft’s lightweight requirements. Thus, the structural stiffness index should be optimized to a lower value while ensuring safe operation during lunar surface driving without compromising performance. This paper calculates and determines the structural bending and torsional stiffness indicators for the manned lunar vehicle’s body through simplified model calculation and the FEA method.

Shen, Zhenghui, Wu, Yingjia, Yang, Jianfeng, Wang, Weijun, Zhang, Chongfeng, Han, Liangliang

Design and Testing of a Quasi-Zero-Stiffness Vehicle-Mounted Isolation System with Additional Inerter

2026-99-0520

7/10/2026

Vehicle vibrations during precision instrument transport can cause damage and failure. Existing vibration isolators often lack reliability, mass production feasibility, and easy maintenance. In this paper, we design and analyze a quasi-zero-stiffness vehicle-mounted isolator with an inerter, decreasing dynamic stiffness while raising the effective mass. Theoretical, simulation, and experimental results show improved isolation performance, lower isolation frequency, and a broader isolation bandwidth.

Li, Kai, Lv, Sibo, Sun, Ning, Dai, Shijie

A New Correlation Approach for Body Distortion of a Complete Vehicle Using MBD and Test Results

2026-01-0680

6/20/2026

By using a fully trimmed vehicle body as flexible body, imported through a Modal Neutral File (MNF), in a complete vehicle Multibody Dynamics (MBD) analysis, the simulation setup gets considerably closer to the test conditions compared to only using a linear Finite Element Method (FEM) approach. Since the MBD analysis includes gravity, rigid body modes of the vehicle and the nonlinear behavior of the wheel suspension, it brings the correlation between simulation and test to a new and more comprehensive level. As correlation criteria, the results of the so-called Multi Stethoscope (MSS) are used. The MSS captures the time history of distortion in all body openings and cross sections and enables a detailed stiffness evaluation of the body using the so-called Opening Distortion Fingerprint (ODF). The ODF gives the quasi-static response while the Operational Deflection Shape (ODS), which is another result of the MSS measurements, reflects the dynamic response. Apart from the different individual steps of this new correlation approach, the paper highlights the importance of considering Component Mode Synthesis (CMS) when embedding and evaluating a linear FE model of the fully trimmed body in the nonlinear MBD environment through an MNF. An example of CMS using the Craig-Bampton method shows the impact of the different parameters included in the CMS. Furthermore, a new graphical feature in combination with the ODS is presented which enhances correlation capability. Finally, an example shows how this new correlation approach can improve the simulation model of a newly developed robotaxi for Waymo.

Lindkvist, Lisa, Olger, Emma, Piiroinen, Petri, Karypidis, John, Pena, Milton, Bäcklund, Jesper, Appelgren, Peter, Marberg, Henrik, Ugale, Pravin, Weber, Jens

Early-Stage BIW Design Evaluation Using Higher-Order Beam–Shell Hybrid Models

2026-01-0674

6/20/2026

Achieving favorable Noise, Vibration, and Harshness (NVH) and durability performance in vehicles requires sufficient static and dynamic stiffness of the Body-in-White (BIW). Virtual development of BIW performance targets during the early design stages is essential to minimize costly modifications in later phases. In the automotive industry, full-scale finite element models are widely used for this purpose, offering high fidelity and enabling comprehensive performance evaluations. However, their complexity and high computational cost limit their practicality for early-stage sensitivity and optimization studies. Beam-based models offer a faster alternative; however, conventional beam formulations based on Euler–Bernoulli or Timoshenko beam theories often fail to capture the complex deformation behaviors of thin-walled structures, which are typical of BIW designs. This typically results in poor correlation with detailed models unless artificial joint flexibility is introduced at structural connections. To address these limitations, this study proposes a hybrid modeling approach that combines Higher-Order Beam (HOB) elements with shell elements. HOB elements account for sectional deformation modes—such as warping and distortion—beyond standard translational and rotational degrees of freedom, enabling a more accurate representation of thin-walled member behavior. This work extends previous research by applying HOB theory to BIW modeling, including panel components such as the floor and roof. Comparative analyses with detailed 3D models demonstrate strong agreement, validating the accuracy and efficiency of the proposed method. The results highlight the potential of HOB-based hybrid models as reliable, computationally efficient tools for early-stage BIW design evaluation and layout optimization.

Kim, Jin Hong, Gang-Won, Jang

A New Approach to Identify Rigid Body Rotations When Measuring the Body Distortion of a Full Vehicle

2026-01-0682

6/20/2026

When developing a vehicle, the overall body stiffness is an important parameter to be estimated for several automotive attributes. As a complement to the traditional experimental and computational static torsional stiffness assessment, an improved method has been developed to evaluate the body stiffness when driving the vehicle on a test track. This method, valid for both test and simulation, is called Opening Distortion Fingerprint (ODF) and uses the so-called Multi Stethoscope (MSS) to measure the dynamic distortion in each body closure opening and cross section. For evaluating the distortion, from both test and Multi Body Dynamics (MBD) simulation data, the Evaluation-line (E-line) method is used. The E-line method is a linear approach. Consequently, it is only valid in the absence of large rigid body rotations of the vehicle body. Therefore, to assess the validity of the ODF method, it is crucial to identify the frequency at which the distortion results become invalid due to rigid body rotations. To identify this frequency range, in an MBD simulation the total distance output parameter can be requested and used. But for a dynamic full vehicle test, it is a major challenge to measure the total distance. Several tests have been performed without success. To calculate this frequency range from test data, this paper presents a new approach. In this methodology two different signal processing methods (E-line and Diagonal) are combined. To check the validity of the new approach, full vehicle test data has been evaluated. In addition, a simplified beam lab experiment is presented, highlighting the difference between test and MBD simulation when measuring the distortion at large rotations.

Olger, Emma, Lindkvist, Lisa, Piiroinen, Petri, Karypidis, John, Pena, Milton, Bäcklund, Jesper, Appelgren, Peter, Marberg, Henrik, Ugale, Pravin, Weber, Jens

High-Frequency Mount Characterization: A Comparison of Methodologies

2026-01-0693

6/20/2026

The rapid electrification of the automotive industry introduces new challenges in noise, vibration, and harshness (NVH). In particular, in a virtual prototyping phase of the e-vehicles development, the rubber mounts are often one of the key elements to be considered when analysing the structure borne noise contributions. Having an accurate experimental characterization of the mount dynamic stiffness curves is therefore very relevant. However, conventional mount characterization methods are often pushed to their limits, partly due to the use of stiffer bushings, and partly because the frequency range of interest is extended toward higher frequencies. When using inverse substructuring, the dynamic stiffness curves can be obtained from frequency response function measurements. The required test setup consists of excitations and responses, located on each side of the mount via dedicated fixtures. The measured frequency response functions are reduced into 6 degrees of freedom representation at the active and passive side of the mount using the classical virtual point transformation. This classical approach assumes the fixtures to behave rigidly. This assumption holds in the lower frequency range, but not anymore in the higher frequency range. In this paper, novel approaches to identify the dynamic stiffness are presented. Namely, an enhanced virtual point transformation that considers flexible fixtures modes is proposed. Those modes may be obtained via finite element modeling or from an experimental modal analysis. Alternatively, a hybrid framework leveraging high-frequency testing and simulation to develop a parametric finite element mount model is presented. The latter approach eliminates the need for fixtures. These methodologies are compared and validated on an automotive rubber mount.

Bianciardi, Fabio, Forrier, Bart, Minervini, Domenico, Barbieri, Marco, Janssens, Karl

A Novel Stiffness Prediction Model of Rolling Lobe Air Springs Considering Irregular Piston Contour Geometry: Development and Experimental Validation

15-19-02-0006

5/18/2026

An accurate air spring model is essential for the design and optimization of air suspension systems to achieve superior performance. This article presents a novel stiffness model for a rolling lobe air spring (RLAS), formulated using stiffness characteristic parameters. Prediction models for these parameters, including effective area and its change rate, as well as effective volume and its change rate, are derived through geometric analysis, based on polynomial fitting of the irregular piston contour. The local contour cone angle of the piston is determined by differentiating the polynomial function, capturing the geometry-dependent variation across the profile. Additionally, a nonlinear hysteresis model for the rubber bellows is integrated, combining a Berg friction component and a Kelvin-Voigt fractional derivative viscoelastic model to represent the amplitude- and frequency-dependent behavior of the RLAS. The proposed model is parameterized through quasi-static and dynamic bench tests under varying amplitudes and frequencies and is validated against both experimental data and an existing modeling approach. Comparative results demonstrate that the proposed model effectively and accurately predicts the static and dynamic responses of the RLAS.

Xia, Xiaojun, Zhang, Hong, Zou, Yi, Ye, Lei, Lu, Yi, Chen, Rui, Zou, Hantong, Wang, Yang

Multi-Physics Topology Optimization and Neural Network–Based Design of Experiments for Lightweight Automotive Cast Components

2026-01-0510

4/7/2026

This paper presents a hybrid optimization framework that integrates Multi-Physics Topology Optimization (MPTO) with a Neural Network–surrogated Design of Experiments (NN-DOE) to enable lightweight structural design while satisfying crashworthiness, durability, and noise, vibration, and harshness (NVH) requirements under practical casting and packaging constraints. In the proposed MPTO formulation, crash and durability performances are incorporated through equivalent static compliance measures, while NVH performance is assessed using a frequency-domain dynamic stiffness metric, allowing consistent evaluation of trade-offs among competing design requirements. The framework is first demonstrated using a mass-produced passenger-car lower control arm (LCA) as a benchmark component. In this application, MPTO achieves weight reduction under multi-physics objectives by removing non-load-bearing material. Results show that single-discipline optimization produces unbalanced topologies, while balanced crash–durability–NVH consideration yields robust load paths. The study further demonstrates that crash and durability are dominated by static compliance–based response, whereas NVH performance is governed by frequency-dependent dynamic response over the relevant frequency range. The framework is then applied to a front engine mounting bracket of a newly developed heavy-duty truck. In this second application, a two-step strategy is employed in which MPTO first establishes the global load-carrying topology under manufacturing and packaging constraints, followed by NN-DOE–based local refinement to achieve stress attenuation at non-designable regions through global structural stiffness rebalancing, rather than direct geometric modification. Final verification confirms a steel-to-aluminum material transition achieving approximately 45% weight reduction and a substantial improvement in durability fatigue life, while maintaining required crash performance.

Kim, Hyosig, Senkowski, Andres, Gona, Kiran, Saroha, Lalit, Boraiah, Mahesh

Impact of User-Adjustable Vehicle-Dynamics Tuning on Vehicle Durability

2026-01-0194

4/7/2026

Software-defined vehicles offer customers a greater degree of customization of vehicle controls and driving experience. One such feature is user-adjustable tuning of vehicle ride and handling, where customers can vary ride height, damper stiffness, front-rear torque balance, and other aspects of vehicle dynamics. While promising a great customer experience, such a feature can expose the vehicle to a wider range of structural loads than those in the nominal design condition, particularly when such tuning is extended to cover spirited “sport” mode driving, off-road driving, etc. In this paper we present a novel methodology combining Road Load Data Acquisition (RLDA) data and real-world telemetry data to estimate the impact of user-adjustable vehicle-dynamics tuning on structural durability. In doing so, the method combines the physics of damage accumulation (from RLDA data) with user behavior (from telemetry data) to present an accurate assessment of the impact on durability, moving beyond traditional durability methods that do not model a range of real-world usage behavior. The study has been conducted using one instrumented vehicle (RLDA) and de-identified telemetry data from over 20,000 Rivian customer vehicles. The study analyzes the impact of variations in ride height, damper stiffness of active dampers, and roll stiffness of the suspension on vehicle structural durability. By combining usage frequency of the different settings with the damage accrued in these settings, the methodology estimates the high-cycle fatigue pseudo-damage variation for a wide range of customers and compares real world damage risk with the damage accounted for in the baseline durability testing. Through the analysis, we recommend a way to optimize the Accelerated Duty Cycle (ADC) for Over the Road (OTR) testing to minimize real-world risk, while keeping the duty cycle simple and practical for testing, i.e., test for an optimized combination of a few dominant settings and not a wide range of settings. The approach also suggests a path to a real-time fleet monitoring system to identify high-durability-risk customers and develop mitigation strategies.

Demiri, Albion, Ramakrishnan, Sankaran, White, Dylan, Khapane, Prashant, Borton, Zackery

High Biofidelity Modification of Thoracolumbar Structure in THOR Model for Reclined Occupant

2026-01-0196

4/7/2026

With the rapid development of automated driving and the increasing adoption of “zero-gravity” seats, the crash safety of highly reclined occupants has become a critical issue. The current THOR dummy, designed for frontal impacts in the standard upright posture, exhibits limitations when directly applied to reclined seating configurations, including insufficient spinal flexion capability and excessive posterior pelvic rotation. In this study, the thoracolumbar spine kinematics of the THUMS human body model, reconstructed against post-mortem human subject (PMHS) tests, were analyzed. A two-segment linear fitting was employed to characterize a “dummy-like” spinal flexion response, yielding a virtual rotational hinge located near the thoracolumbar joint of the original THOR model. The characteristic rotation angle obtained from THUMS showed a strong linear correlation with the flexion moment of the T12–L1 vertebrae. Based on this relationship, the rotational joint of the THOR dummy was unlocked during impact and assigned a torsional stiffness of 600 Nm/rad. Additional modifications were implemented in the hip region to enhance model applicability. Comparative simulations demonstrated that the modified THOR model achieved closer agreement with PMHS responses than both the Hybrid III and the baseline open-source THOR models. In particular, the posterior pelvic tilt was reduced from approximately 20° in the baseline THOR to about 10° in the modified version. These results indicate that incorporating PMHS-based thoracolumbar flexion characteristics together with targeted hip modifications significantly improves the biofidelity of the THOR dummy for reclined-occupant crash scenarios, providing a solid foundation for future dummy development and safety assessment.

Guo, Wencheng, Kuang, Gaoyuan, Shen, Wenxuan, Tan, Puyuan, Zhou, Qing

Data-Driven Study on Chassis Suspension Performance Degradation

2026-01-0582

4/7/2026

The performance of chassis suspension mechanisms critically affects vehicle handling, ride comfort, and safety. Implementing real-time health monitoring for chassis systems contributes to preventing severe consequences such as increased body roll or loss of handling stability caused by shock absorber softening or spring stiffness degradation under deteriorating operating conditions, while circumventing the substantial costs associated with professional facility-based chassis inspections. With the rapid development of sensing and data analytics technologies, data-driven approaches are increasingly used in health monitoring. This study aims to achieve online monitoring of chassis suspension performance degradation using a deep neural network (DNN). First, a half-car model incorporating both vertical and pitch motions was established to simulate bumpy road conditions, with the aim of constructing a dataset that includes key vehicle suspension parameters and vehicle states related to their degradation characteristics. Subsequently, a DNN model comprising three hidden layers is developed to assess suspension performance degradation. To optimize model performance, the effects of different numbers of neurons and hidden layers on model accuracy are explored. Experimental results show that the maximum absolute percentage errors of the DNN model in predicting suspension stiffness and damping coefficients are less than 0.13% and 0.17%, respectively, with average absolute percentage errors below 0.046% and 0.06%. The coefficients of determination (R2) exceed 0.999. The proposed method accurately predicts the trend of key suspension parameters, providing robust data support for health management and maintenance decision-making. This is expected to reduce safety risks and maintenance costs while enhancing overall vehicle performance and reliability.

Liao, Yinsheng, Lei, Yisong, Su, Ailin, Wang, Zhenfeng, Shi, Shuai, Zhang, Lei, Zhang, Junzhi, Ma, Changye

Acoustic Improvements to a Passenger Service Unit Panel with Core Filler and Facesheet Patches using Topology Optimization

2026-01-0511

4/7/2026

Passenger comfort is becoming the forefront of luxury private jets where noise needs to be kept to a minimum. One source of structure-borne noise is the vibration of the Passenger Service Unit (PSU) panel. These vibrations originate from the outer skin, excited by turbulent boundary layer, and are transmitted through the fuselage frame to the PSU panel. This panel resides overhead of passenger seating, it is composed of a corrugated honeycomb core sandwiched between thin face-sheets. This paper presents a systematic approach to improve the vibro-acoustic performance of a honeycomb core sandwich structure by employing core filler and facesheet patches. Topology Optimization (TO) is used to determine the optimal layouts of these design modifications. The vibro-acoustic performance of the PSU panel with facesheet patches and core filler is evaluated using a frequency response analysis in the commercial finite element solver OptiStruct. The effectiveness of vibration reduction will be quantified by using the Dynamic Stiffness (DS) and velocity response of the PSU panel measured using the Frequency Response Function (FRF). Validation used excitations from 500 to 3000 Hz and indicated that using the TO interpreted layout of core filler and facesheet patches, separately improved the DS of the panel by 402% and 198%, and the velocity response by -35% and -18%, while increasing the weight by 0.1% and 4.7% respectively. Their combined effect has also been tested and found to provide an additional 445% improvement to DS and a -39% improvement in velocity response with 4.8% of additional material, though overall behavior varies depending on frequency range.

Russo, Connor, Whetstone, Isobel, Patel, Anuj, Wotten, Erik, Kim, Il Yong

Prediction of Dynamic Stiffness of Automotive Components Using Support Vector Methods

2026-01-5016

2/23/2026

In the current scenario of EV revolution in the automotive industry, NVH performance of the vehicles is one of the major points of sale to the customers. Auxiliary components play one of the predominant roles in the contribution of noise to overall vehicle interior or exterior sound pressure levels, which impact customer vehicle comfort. CAE prediction of NVH performance of automotive components involves a lot of design iterative processes, large server space utilization, and time-consuming. To reduce cost and time, data-driven technologies like AI algorithms can help CAE engineers because of their high efficiency and high precision. In the current research, a wiper motor mount stiffness prediction algorithm was designed based on the historical data using CAE analysis and AI algorithms, and improved prediction accuracy by tuning the parameters of AI algorithms using grid search methodology. High prediction accuracy of wiper motor mount stiffness has been achieved with the method of support vector machine. CAE engineers can avoid iterative processes by utilizing the optimized design parameters from the prediction results without running full finite element analysis simulations.

Paturi, Yuva Venkata Sekhar

Dynamic Stiffness Prediction in Cracked Cantilever Beams Using Enhanced ANN Techniques

2026-28-0050

2/12/2026

This research paper provides a comprehensive study on how Artificial Neural Networks (ANNs) can be deployed to predict the stiffness characteristics of a cantilever beam with a crack of various depths and positions. The most destructive source of failure is considered to be vibration, so the major focus of this paper will be on how the cracks affect the modal stiffness. This study has various applications, such as airplane wings, bridges, stadiums, and arenas. A common research gap was noticed amongst the existing studies; the position of the cracks in the cantilever wasn’t considered, but this paper discusses how the location of cracks severely affects the dynamic behaviour of the cantilever. This study was done by carrying out modal analysis on a cantilever of the same dimensions with different crack configurations. Various crack dimensions and orientations were analysed to understand the effects of the crack on the dynamic behaviour of the cantilever. From the modal analysis results, we evaluated the natural frequency of the cantilever beams with various crack depths and locations. A decrease in natural frequency was observed as the crack depth increased, from which we can infer that the cantilever will experience resonance at much lower external vibration, which makes the structure unreliable. Cracks near the support markedly lower natural frequency due to maximum shear force and bending there, whereas free-end cracks have a negligible impact compared to a reference cantilever. Simulation results feed an ANN, enabling it to accurately predict dynamic characteristics for any combination of crack depth and position. The developed ANN model achieved high prediction accuracy with a Mean Squared Error (MSE) of less than 1x10-5 and an R2 value exceeding 0.998 on the test dataset, demonstrating its robustness as a tool for structural health monitoring.

SB, Harshini, Rajkumar, Manjari, R, Krithika, K, Anusha, K, Divya, Bhaskara Rao, Lokavarapu

Refinement of Road Induced Steering Wheel Vibration in Electric Vehicle

2026-26-0337

1/16/2026

Nowadays, customers expect excellent cabin insulation and superior ride comfort in electric vehicles. OEMs focus on fine tuning the suspension system in electric vehicle to isolate the road induced shocks which finally offers superior ride quality. This paper focuses on enhancing the ride comfort by reducing the road excitation which originates mainly due to road inputs. Higher steering wheel vibration is perceived on the test vehicle on rough road surfaces. To determine the predominant force transfer path, Multi reference Transfer Path Analysis (MTPA) is performed on the front and rear suspension. Based on the finding from MTPA, various recommendations are explored and the effect of each modification is discussed. Apart from this, Operational Deflection Shape (ODS) analysis is used to determine the deflection shape on the entire steering system . Based on ODS findings, recommendations like dynamic stiffness improvements on the steering column and steering wheel are explored and the impact on the steering wheel vibration is discussed. With all the counter measures proposed, steering wheel vibration levels are reduced by ~ 7 dB . Component level modal targets are proposed to avoid the vibration concern due to road excitation.

S, Nataraja Moorthy, Rao, Manchi, Selvam, Ebinezer, Raghavendran, Prasath

Sound Quality Refinement and Vibration Reduction During Horn Application in Electric Vehicles

2026-26-0338

1/16/2026

This paper focuses on the cabin sound quality refinement and the tactile vibration reduction during horn application in the electric vehicle. A loud cracking sound inside the cabin and higher accelerator pedal vibration are perceived while operating the horn. Sound diagnosis is carried out to find out the frequencies causing the cracking noise. Transfer path analysis is conducted to identify the nature of noise and the predominant path through which forces transfer. Based on finding from TPA, various recommendations are evaluated which reduced the noise to a certain extent. Operational Deflection Shape (ODS) is conducted on the horn mounting bracket and on the body to identify the component having higher deflection at the identified frequencies. Recommendations like DPDS improvement on the horn bracket and the body is assessed and the effect of each outcome is discussed. With all the recommendations proposed, the cabin noise levels are reduced by ~ 8 dB (A) and the accelerator pedal vibration levels are reduced by ~ 40%. Sound quality parameter which needs to be considered during the horn selection is explained. The modal criteria which must be taken into account during development phase to avoid the horn cracking noise and tactile vibration is also proposed.

S, Nataraja Moorthy, Rao, Manchi, R, Ashwin sathya, S, THARAKESWARULU, Raghavendran, Prasath

Design & Optimization of CV Shaft System to Address Powertrain Induced NVH Issues

2026-26-0336

1/16/2026

The automotive industry is a crucial sector that plays a significant role globally. Government policies have a profound impact on this automotive industry in defining the regulatory standards and emission controls. Such regulations incentivized automakers to invest in research and development complying those standards towards reduction of vehicle emission which intern result in higher torsional vibrations and excitations amplitudes. To address the rising NVH related concerns in driveline system. Drive shafts (CV shafts) is an important component in power-train system in vehicle. Drive shaft’s main purpose to transfer torque from engines to wheels at multiple speeds with different articulation angles. The roughness generated by the engine follows a transfer path from engine to transaxle and transaxle to half shafts in monocoque vehicles which generates discomfort to the drivers whenever the vehicle is driven. The roughness can also be addressed by proper design of CV Shaft stiffness and tuning mass dampers. In this paper we focus on parametric changes on drive shaft torsional stiffness and tuned mass damper to address Engine roughness and driveline induced noise. Test measurement is done to measure baseline CV Shaft bending frequency without dampers. AMESIM 1D simulation model is developed to reproduce Bending frequency and mode shapes. Optimization for the convergence on stiffness and damper frequency is done. With the new stiffness shaft and tuned damper vehicle has improved on the noise pattern, magnitude of oscillations and shift in natural frequency.

M A, Abdul Azarrudin, Jayachandran, Suresh kumar, Kumar, Shivani, Bhardwaj, Kinshuk, M, Devamanalan, Kanagaraj, Pothiraj, Ahire, Manoj

Investigation and Reduction of Road Noise due to Transient Road Inputs in Electric Vehicle

2026-26-0358

1/16/2026

Higher road noise is perceived in the cabin when the test vehicle encounters road irregularities like bump or pothole in the public roads. The transfer of transient road inputs inside the body caused objectionable cabin noise. Measurements are conducted at different road surfaces to identify the patch where the objective data well correlated with the noise measured at the public road. Wavelet analysis is carried out to identify the frequency zones since the events are transient in nature. TPA is carried out in time domain to identify the nature of the noise and the dominant path through which the transient road forces are transferring inside the body. Based on the outcome of TPA, various countermeasures like reduction of dynamic stiffness of suspension bushes, TMDs on the path are proposed to reduce the structure borne noise. Criteria which need to be considered for reduction of cabin noise due to transient road inputs is also discussed.

S, Nataraja Moorthy, Rao, Manchi, Selvam, Ebinezer, Raghavendran, Prasath

Novel Approach on Material Characterization Testing of Various Wiring Harness

2026-26-0548

1/16/2026

The automotive wiring harness (length of 4-5 km) is a very important and complex system in the development of a modern car due to lot of new electric & electronic components and sensors. It is a very sensitive material unlike metals and is considered as a composite which is highly anisotropic in nature, as it consists of several different layers of copper/aluminum strands and insulation. Because of insulation, wiring harness exhibits viscous plastic behavior which is crucial in determining the durability and long-term performance of the cables. Material property has a crucial role in determining the behavior of wiring harness after assembly into the car. Wiring harness may undergo Bending, Torsion and Tension loads, causing the stress and strain in the individual electrical wires. The lack of CAE validation of the wiring harness routing may lead to extra costs for the automotive OEMs during product development. This study explains the novel method of Testing the Cables and Bundles present in cars to get the material properties of it. The procedural description is applicable to single core, multi core and Bundles containing various configurations of cables. Initial assessment tests have been carried out before confirming the methodology for this testing, to ensure the repeatability of test results among various Test samples. The findings from this testing are Bending stiffness, Torsional stiffness and Axial(Tensile) stiffness for calculating the length-independent stiffness of the wiring harness material. The result plots from this Testing contain flow curves to determine the modulus of elasticity, ultimate strength etc., and cyclic curves to determine the Visco-plastic properties of the wiring harness. Material properties from this Testing will be used in the digital development of wiring harness CAE during vehicle development.

Beesetti, Siva, Kalkala Balakrishna, Prasad, James Aricatt, John, Shah, Dipam, Tas, Onur, Krogmann, Stephan

Methodology for Optimizing the Bench Testing of Steering I-Shaft Using Vehicle Level Data to Reduce Overall Product Development Time and Cost

2026-26-0560

1/16/2026

Steering I-shaft with rubber coupling (or hardy disc) is an important part of complete steering system mainly in body on frame (BOF) vehicles. Hardy discs are used to dampen the vibrations that transmit to steering wheel through frame, steering gear and I-shaft. They also support to accommodate the variation between frame and BIW (Body in white) of body on frame vehicles. They are made up of rubber or other polymer composites, which have less torsional stiffness as compared to metals. The overall torsional stiffness of steering system reduces since the hardy disc is used in series in steering system, that impacts on the overall performance of steering system. So, during development of I shafts with different design, stiffness of hardy discs are used to optimize the steering and NVH performance of vehicle. Considering the development time and cost, each design of I-shaft cannot be validated at vehicle level. The torsional and axial force or displacement of hardy disc is measured at vehicle level on different test tracks and block cycles are made that consists of different displacement / force along with frequencies. These block cycles are then used at bench level testing of I-shafts. This paper summarizes the methodologies to measure the force or displacement of I- shaft, converting raw data to useful block cycles and test set up for bench testing of steering I-shaft.

Kabdal, Amit

Experimental Evaluation of Tyre Vertical Dynamic Stiffness and Damping for Ride Model Applications Using Flat Trac

2026-26-0607

1/16/2026

The vertical dynamic stiffness and damping of a tyre are critical to ride comfort and overall dynamics, particularly for low-frequency excitations in urban and highway driving. As the tyres are the primary interface between the vehicle and the road, absorbing surface irregularities before the suspension engagement, precise tyre parametrization is essential for accurate ride models. This study investigates an experimental methodology characterizing the vertical dynamic behavior of pneumatic tyres using a Flat Trac test machine. Contrary to the conventional approaches that depend on intricate shaker rigs or frequency dependence function models, the proposed technique uses a realistic force displacement loop-based methodology which is appropriate for ride models. Dynamic stiffness is computed from slope of a linear regression fitted to force and displacements during vertical sinusoidal excitation. Damping is derived from hysteresis energy loss per cycle. The tests were conducted under various conditions by varying vertical loads, inflation pressures (IP), excitation frequencies, and deflection amplitudes (4–8 mm). The generated stiffness and damping curves from the test results can be directly applied in quarter-car models and could potentially be extended to the full-vehicle ride simulations for ride characteristics assessment studies. Research indicates that the dynamic stiffness of a non-rolling tyre is consistently higher than that of a rolling tyre. Under rolling conditions, dynamic stiffness increases with test speed due to excitation frequency effects. Additionally, vertical dynamic stiffness correlates positively with inflation pressure (IP); increasing it from 216 to 264 kPa yields a 12–14% rise in stiffness for both rolling and non-rolling condition. The proposed framework facilitates the integration of realistic tyre vertical dynamics into vehicle ride models while maintaining minimal complexity, thereby improving simulation fidelity and supporting better design and evaluation of ride quality in early stage of vehicle development.

Duryodhana, Dasari, Sethumadhavan, Arjun, Tomer, Avinash, Ghosh, Prasenjit, Mukhopadhyay, Rabindra

High-Frequency Dynamic Stiffness Measurements of Automotive Elastomers for Electric Vehicles

2026-26-0312

1/16/2026

The increasing adoption of electric vehicles (EVs) has intensified the demand for advanced elastomeric materials capable of meeting stringent noise, vibration and harshness (NVH) requirements. Unlike internal combustion engine (ICE) vehicles, EVs lack traditional masking noise generated by the powertrain. In the automotive industry, the dynamic stiffness of elastomers in internal combustion engines has traditionally been determined using hydraulic test rigs, with test frequencies limited to a maximum of 1,000 Hz. Measurements above this frequency range have not been possible and are conducted only through computerized FE or CAE calculation models. Electric drive systems, however, generate distinct tonal noise components in the high-frequency range up to 10,000 Hz, which are clearly perceptible even at low sound pressure levels. Consequently, the dynamic stiffness characteristics of elastomers up to 3,000 Hz are critical for optimizing NVH performance in EVs. This study focuses on high-frequency dynamic stiffness testing of automotive elastomers using a specialized high-frequency test rig. According to ISO 10846-1 [1], there are two methods for determining the dynamic stiffness of elastomers: the direct method (part 2) and the indirect method (part 3). This paper presents measurements carried out using the direct method, employing an electrodynamic shaker and applying static preload conditions. The objective is to accurately determine the frequency-dependent dynamic stiffness and damping properties of elastomeric components, such as engine mounts, bushings, and isolators, which play a crucial role in mitigating structure-borne noise and vibrations.

Bohne, Christian, Gröne, Michael

Analysis of Door Seal Compression and its Influence on NVH Performance in Heavy-Duty Vehicle

2026-26-0339

1/16/2026

This study focuses on the effect of door seal compression prediction and its impact on structure borne NVH in trucks. Customer perception of vibrations are envisaged as quality criteria. It is necessary to determine the contribution of seal stiffness due to seal compression under closed condition of the door rather than considering stiffness of the door seal under uncompressed conditions. The dynamic stiffness of door seal is determined from analysis of non-linear type. The simulations are built using the Mooney - Rivlin model. The parameters influencing the compression of door seals in both two – dimension and three – dimension, are identified from the analysis. This involves contemplating the appropriate seal mounted boundary condition on the body and the door of the vehicle. The stiffness after compression of seal is extracted from this non-linear analysis which is further used to obtain the vibration modes for the doors in the truck cabin. As a part of next step, the compressed seal stiffness value is used to analyze the operational vibration and structure borne cabin noise. The simulated results for modal performance including the effects of seal are validated with the experimental test data and are noticed to be in good agreement. The simulated result of models that were analyzed with the use of both uncompressed seal data and compressed seal data are compared for operational vibration, operational noise respectively. It is observed that the compressed seal stiffness has an impact on the structure borne NVH performance of the truck cabin.

L, Kavya, Ramanathan, Vijay

Tailgate Stiffness Mitigation and Engineering Strategy for Full Width Tailgate-Mounted Tail Lamp Integration

2026-26-0494

1/16/2026

The tailgate, as the rearmost vehicle opening, plays a pivotal role in defining the rear aesthetic theme while ensuring structural durability and maximizing luggage space. Contemporary automotive design trends highlight an increasing demand for Full width tailgate-mounted tail lamp configurations, which deliver a bold and dynamic visual appeal. Enhanced by animated lighting features, these designs cater to the preferences of Gen Z customers, becoming a decisive factor in purchasing decisions. However, integrating these complex tail lamp structures introduces significant engineering challenges, including increased X-dimension lamp volume, thereby providing reduced design space, and intricate mounting schemes constrained by panel stamping limitations. These factors necessitate the development of innovative joinery strategies and structural definitions to maintain durability targets, including achieving 25,000–30,000 slam cycles without failure, while preserving luggage space. This paper presents a comprehensive design and engineering approach aimed at enhancing the modal performance of automotive tailgate systems, with a particular focus on configurations incorporating full width taillamps. The study addresses key structural challenges associated with maintaining stiffness and durability while accommodating complex styling and packaging constraints. By optimizing outer panel joinery, refining mounting strategies, and redefining inner structural reinforcements, the proposed methodology achieves significant improvements in dynamic stiffness characteristics. Experimental and simulation-based evaluations demonstrate a 12% increase in modal stiffness for conventional tailgate architectures and a 45% improvement in coupe-type liftgate configurations. The findings offer valuable insights into the co-development of structural and styling elements in modern tailgate systems, contributing to improved vehicle performance, NVH behavior, and customer satisfaction.

Beryl, Joshua, Mohanty, Abhinab, Unadkat, Siddharth, Selvan, Veera

Prediction of Trimmed Body Noise Transfer Function Based on BIW Response Using Machine Learning

2026-26-0640

1/16/2026

This work focuses on the prediction of Trimmed Body Noise Transfer Function (NTF) using Glazed BIW (body in white) structural model characteristics by leveraging Machine Learning (ML) technique. Inputs such as Glazed BIW (GBIW) attachment dynamic stiffness, Body Panel Vibration Transfer Functions (VTF) and Driver Ear level NTFs are employed to predict Trimmed Body NTF for a particular hard point. An iterative process of performing design modifications on the BIW to verify its effect on BIW performance and therefore on Trimmed body NTF is undertaken. BIW geometric parameters are varied in an organized manner to generate hundreds of data points at GBIW level which are provided as input to the train the ML model to predict the trimmed body level NTF. The outcome provides crucial insights of how the trimmed body NTF is closely related to the GBIW design characteristics. This ML approach of predicting trimmed body NTF based on GBIW characteristics provides critical insight about GBIW design during early stages of product evolution, which benefits in quick decision making rather than the conventional approach of evaluating complex trimmed body simulations.

Kulkarni, Prasad Ramesh, Bijwe, Vilas, Kulkarni, Shirish, Sahu, Dilip, Inamdar, Pushpak

Simulation Driven Design of Crank-train Systems for Elevated In-Cylinder Combustion Pressures for Existing Architecture

2026-26-0400

1/16/2026

The work demonstrating a novel approach to the optimization of crankshaft design for heavy-duty commercial vehicle engines, specifically targeting non-automotive applications with elevated power ratings. The research focuses on a 6-cylinder, 5.6-litre diesel engine, originally rated at 160 kVA and upgraded to 200 kVA, where the challenge was to enhance the crank-train system’s robustness within existing packaging constraints. By fundamentally altering the crankshaft’s geometry and structural parameters, the new design achieves higher load-bearing capacity while inherently mitigating torsional vibrations, thereby eliminating the need for viscous dampers traditionally used in place of rubber dampers. Advanced simulation tools, notably AVL Excite, employed to iterate and evaluate the balance between crankshaft balance ratio, weight, and torsional behavior. The optimized design then validated through both simulation and physical vibration trials, with sixth-order angular displacement maintained within prescribed limits. Further refinement of the simulation model achieved by optimizing the torsional stiffness of the ring gear to ensure strong correlation with physical measurements. This work demonstrates an effective alternative to viscous dampers and provides a pathway for future crankshaft design in high-power commercial engines.

Khandelwal, Meha, Kaundabalaraman, Kaarthic, Rathi, Hemantkumar

Development of a Lightweight Front-End Structure Using Injection Molding Technology

2026-26-0304

1/16/2026

This paper focuses on the development of a lightweight, functionally integrated Front-End Structure (FES) using plastic-metal hybrid injection molding technology. The objective is to achieve modularization, part consolidation, weight and cost reduction. The proposed design integrates multiple components into a single module which makes assembly faster and easier. A mounting strategy with fixation features was added into the structure, which effectively supports various components and sub-assemblies. Component-level Finite Element Analysis (FEA) was carried out which includes static strength analysis, bending and torsional stiffness analysis, modal analysis as well as latch pull test to achieve required structural strength. Ribbing structures were designed and optimized based on FEA result to provide the necessary strength and stiffness to the structure within the minimum weight. Moldflow analysis was carried out to evaluate manufacturability with focusing on gate design, minimizing warpage, and flow balance. Based on Moldflow analysis, necessary design corrections were carried out before tool development for defect-free molding. After validating all performance criteria, the part was manufactured using injection molding process. Compared to conventional sheet metal structures, the thermoplastic FEM achieved an approximate 50% weight reduction while maintaining structural integrity.

Srivastava, Sanjay, Thakoor, Shruti Ghanshyam, Sonkusare, Shailesh

Study on the Influence of Liquid Composite Swivel Arm Positioning Nodes on the Dynamic Performance of High-Speed Trains

2025-99-0255

12/23/2025

Rubber components are an important part of the suspension system of high-speed trains, and the complex nonlinear characteristics of rubber parts have a significant impact on the vehicle dynamic performance. This paper establishes a nonlinear dynamics model of the liquid composite swivel arm positioning node, which can reflect the dynamic stiffness and dynamic damping characteristics of the rubber components that change nonlinearly with the frequency and amplitude, and also has a fast calculation speed. The vehicle dynamics simulation model considering the longitudinal stiffness nonlinear characteristics of the arm node is established, and the influence of the stiffness nonlinearity of the liquid composite arm positioning node on the dynamic performance of the vehicle, such as straight-line stability and curve passing ability, is studied in depth through numerical simulation.

Cheng, Junqiang, Yang, Chen, Li, Longtao, Cong, Rilong, Hu, Tingzhou

Leaf Springs in Focus: Integrated Validation of Material, Process, and Performance in Mechanical Suspensions

2025-36-0312

8/1/2025

The continuous improvement of validation methodologies for mobility industry components is essential to ensure vehicle quality, safety, and performance. In the context of mechanical suspensions, leaf springs play a crucial role in vehicle dynamics, comfort, and durability. Material validation is based on steel production data, complemented by laboratory analyses such as tensile testing, hardness measurements, metallography, and residual stress analysis, ensuring that mechanical properties meet fatigue resistance requirements and expected durability. For performance evaluation, fatigue tests are conducted under vertical loads, with the possibility of including "windup" simulations when necessary. To enhance correlation accuracy, original suspension components are used during testing, allowing for a more precise validation of the entire system. Additionally, dynamic stiffness measurements provide valuable input for vehicle dynamics and suspension geometry analysis software, aiding in predictive modeling and optimization of suspension behavior. The implementation of this structured and comprehensive validation methodology, already adopted by companies in the mobility industry, ensures the development of reliable and high-performance products. This approach is particularly beneficial for commercial suspensions used in road transport of cargo and passengers, addressing industry challenges related to safety, durability, and efficiency. By improving validation techniques, the mobility industry strengthens its ability to innovate, comply with regulatory standards, and meet the growing demand for more robust and efficient vehicle suspension systems.

Zahn, André N., Graebin, Matheus, Malacarne, Rodrigo, Toniolo, Juliano C.

Evaluation of Static and Dynamic Stiffness of Rubber Grommet by Experimental and FEA Method

2025-01-0274

7/2/2025

Vibration control is most important in automotive applications, and generally, rubbers are used to dampen these vibrations due to their inherent nature and low-cost manufacturing methods. Now, to select a rubber material, Shore hardness is considered in engineering applications, but to additionally control the behaviour, we need to understand its static and dynamic stiffness. These values help to determine the vibration isolation obtained by these rubbers. In this paper, we will discuss methods to calculate the static and dynamic stiffness of rubber grommets using experimental methods and FEA modelling. As elastomers have non-linear material properties, various material modelling techniques in FEA are used to capture multiple phenomena like creep, fatigue, and dynamic conditions. Rubber compounding is used in order to improve the physical and chemical properties, which in turn would give desirable linear characteristics. Certain guidelines and thumb rules are used in the rubber industry for different loading conditions to have linear stiffness behaviour. Static and dynamic stiffness values obtained by experimental and FEA modelling are in a variation of below 5%.

Khamkar, Prasad Subhash, Gaikwad, Vikrant Chandrakant

Road Noise Improvement Method for Battery Electric Vehicles Based on Bushing Stiffness Optimization

10-09-04-0032

6/23/2025

The chassis bushing is one of the key components affecting the vibration isolation efficiency of a vehicle, and a comprehensive optimization method combining the experimental process and transmission path analysis (TPA) is proposed to reduce the low- and medium-frequency road noise response in the passenger compartment of a battery electric vehicle (BEV). First, the noise signals were obtained in the vehicle road noise test under two working conditions of 40 and 60 km/h at uniform speeds on rough road surfaces. Then, the excitation transmission path was analyzed based on the structural noise transmission model, and the chassis bushing parts with more considerable vibration isolation contribution were screened out. By matching the stiffness values of the chassis bushings in the optimization problem through experimental methods, the optimization scheme reduces the stiffness of the front swing arm bushing and the rear longitudinal arm bushing by 30%. Additionally, a flexible connection is adopted for the rear subframe attachment point, and the tire uniformity parameters are corrected. The results show that the optimization scheme can effectively reduce the road noise response in the low- and medium-frequency bands of BEVs and has been successfully applied to production models in the market.

Liu, Ke, Liao, Yinghua, Wang, Hongrui, Zhou, Junchao

The Accelerated Roughness Noise Optimization of One PHEV Vehicle

2025-01-0087

5/5/2025

To optimize the noise that heard like ‘kalakala’ produced by the plug hybrid electric vehicle when accelerating with a small accelerated pedal opening while in the charging state of series modal. The LMS test device was used to acquire the noise of the driver's outer ear. Through filtering and playback analysis, it was confirmed that the noise is mainly contains the frequency bands of 250-400Hz and450-700Hz. The frequency bands of the noise were used as carriers for Hilbert transform, and their envelopes were obtained for Fourier transform analysis. It was found that the modulation order of the noise is 0.5 times of the engine ignition order, and the modulation frequency is 20-30Hz, which let the customer hears like roughness. Regarding the spectral characteristics of this noise, firstly, at the excitation source, selected a reasonable moment of inertia and frequency of the Crank torsional damper, to decrease the torsional excitation of the engine. Secondly, investigated the structural propagation path of the noise systemically, and effectively reduces the propagation path of the noise by increasing the dynamic stiffness of the powertrain mount’s passive bracket and tuning a reasonable front driveshaft damper. Finally, based on the universal characteristics and the pressure rise rate map of the engine, as well as the targets of the attribute of the vehicle economy and power, different calibration strategies were attempted, and a calibration strategy that balances the three attributes was selected. By the above measures, the energy of two resonance bands of acceleration roughness sound were reduced by 9dB (A), and 3dB (A) respectively. After optimization, the noise inside the car is almost inaudible.

Shouhui, Huang, Zhongxun, Hu, Zhao, Yun, Shanyin, Ren, Ruifeng, Dong, Teng, Charlie, Changshui, Zhou, Xu, Ling

Experimental Characterization of a Steel Spring Mount Using Virtual Point Transformation

2025-01-0046

5/5/2025

The application of virtual point transformation for determining the transfer dynamic stiffness of a helical coil spring is demonstrated in this experimental study. Rigid fixtures are attached to both ends of the spring, and frequency response functions are measured using impact hammer excitations. These frequency response functions are transformed into virtual points, analogous to a node in finite element analysis, with six degrees of freedom. The six degrees of freedom transfer dynamic stiffness is then extracted using the inverse substructuring method, which eliminates the need to account for fixture dynamics. The results are validated by a direct measurement approach. Additionally, the study investigates the effect of liquid applied sprayed damping coatings on the spring's transfer dynamic stiffness, revealing that the coating significantly reduces vibration amplitudes at the surge frequencies. This suggest that the springs effective damping properties are enhanced.

Neihguk, David, Herrin, D. W., de Klerk, Dennis

Necessity of Body Torsional Rigidity of Personal Mobility Vehicles (PMVs) with an Inward Tilting Mechanism

2024-32-0013

4/18/2025

In traditional four-wheeled automobiles, the imbalance between the roll moment, which is the product of the centrifugal force during a turn acting on the center of gravity and the height of the center of gravity, and roll stiffness, which is the product of the left-right difference in tire vertical load and the tread width and commonly used among automotive suspension engineers, of the front and rear sections necessitates body torsional rigidity. However, there is a lack of specific cases and guidelines for constructing the body structure of three-wheeled PMVs (Personal Mobility Vehicles) with a tilting mechanism from the perspective of vehicle dynamics characteristics. In this paper, the basic considerations related to the dynamics of such three-wheeled PMVs are investigated. We use the term “torsional rigidity” to refer to the stiffness as the torsional deformation of the body itself, and the term “roll stiffness” to refer to the moment that counteracts the roll moment during a turn and suppresses the vehicle’s roll in accordance with the terminology commonly used among automotive suspension engineers. In this paper, “torsional rigidity” and “roll stiffness” are clearly distinguished. Through a systematic comparative analysis with conventional four-wheeled automobiles, this study theoretically formulates the concept of mechanical equilibrium for the body torsional rigidity of three-wheeled PMVs, resulting in fundamental guidelines governing their body structure. The findings that the tilting function does not seem to impose torsional loads on the body during steady turning as analyzed through static analysis, shows that torsional rigidity around the longitudinal axis may be unnecessary. However, under actual dynamic conditions, a different scenario emerges. Dynamic simulations under real-world conditions demonstrate significant torsional loads on the body, emerging the necessity of torsional rigidity around the longitudinal axis. In three-wheeled PMVs, body torsion directly influences dynamic vehicle response. Therefore, to accurately delineate the structural requirements for body design, quantitative evaluation of the necessary body torsional rigidity under dynamic conditions is essential. Future efforts will involve creating a dynamic simulation model that integrates considerations for body torsion based on these initial study outcomes. Ultimately, this research aims to bridge the gap between theoretical understanding and practical implementation, contributing to comprehensive guidelines for the body design of three-wheeled PMVs.

Haraguchi, Tetsunori, Kaneko, Tetsuya

Active Suspension System Optimal Control Strategy Considering Vehicle Ride Comfort and Road Maintenance Capability

2025-01-8277

4/1/2025

The suspension system could transmit and filter the forces between the body and road surface, which affects vehicle ride comfort and road maintenance capability. Compared to traditional passive and semi-active suspension, Active Suspension Systems (ASS) could automatically adjust the suspension stiffness, damping force, and body height according to changes in the vehicle's load distribution, travelling speed, and braking action through the addition of a power source such as a linear motor. Although the existing advanced control methods could help to effectively improve the driving quality of vehicles equipped with ASS, the conflict between ride comfort and road maintenance capacity is still a difficult problem to be solved. Therefore, an Active Suspension System optimal control strategy considering vehicle ride comfort and road maintenance capability is proposed in this paper. Firstly, a quarter ASS model and a road model are respectively developed based on the system dynamics relationship and the stochastic sinusoidal superposition method. Then, the model predictive control theory is applied to establish the execution force optimal controller of ASS, which takes into account the Sprung Mass Acceleration (SMA), Suspension Working Space (SWS), Dynamic Tire Deformation (DTD), actuator constraints, and control consumption. Thirdly, Improved Sparrow Search Algorithm (ISSA) Combining Cauchy Mutation and Opposition-Based Learning is designed to tune the built-in parameters of the ASS execution force optimal controller. Simulation results show that the control strategy proposed in this paper could help to maintain good ride comfort and road maintenance capability for vehicles fitted with ASS under various road conditions.

Zhu, Bing, Zhang, Chaohui, Sun, Jihang, Wang, Shiwei, Ding, Shuwei, Li, Lun, Chen, Zhicheng

Dynamic Performance Optimization of Double-Isolation Rubber Mounts Based on Neural Network and Genetic Algorithm Collaboration

2025-01-8266

4/1/2025

As a crucial connecting component between the powertrain and the chassis, the performance of rubber mounts is directly related to the NVH (Noise, Vibration, and Harshness) characteristics of electric vehicles. This paper proposes a double-isolation rubber mount, which, compared to traditional rubber mounts, incorporates an intermediate skeleton and features inner and outer layers of “cross-ribs”. The design parameters can be simplified to: skeleton diameter, skeleton thickness, main rib width, and main rib thickness. To comprehensively evaluate its performance, a finite element analysis (FEA) model of the proposed double-isolation rubber mount was first established in Abaqus, with static stiffness and dynamic performance analyzed separately. The results indicate that, compared to traditional rubber mounts with similar static stiffness, this design effectively controls dynamic stiffness in the high-frequency range. To expand the effective vibration isolation frequency range of the double-isolation rubber mount, an L25 (5^5) orthogonal experimental design was constructed based on the four structural parameters to assess the impact of each parameter on performance. Using static stiffness and peak frequency of dynamic stiffness as optimization objectives, and the four structural parameters as design variables, a neural network-assisted genetic algorithm was employed for dynamic performance optimization of the rubber mount. Finally, based on the obtained optimal design parameters, the dynamic performance of the double-isolation rubber mount was tested. The analysis shows that the test results align with the computational results, demonstrating the practicality of the proposed double-isolation rubber mount.

Xu, Che, Kang, Yingzi, Tu, Xiaofeng, Shen, Dongming

Analysis of Frequency at Minimum Dynamic Stiffness for a Hydraulic Engine Mount with Floating Decoupler under High Frequency Excitation

2025-01-8264

4/1/2025

The primary functions of mounts include providing structural support, sound insulation, and vibration damping. Dynamic stiffness and loss angle are critical metrics for evaluating their NVH (Noise, Vibration, and Harshness) performance. This paper examines a floating decoupler hydraulic mount featuring a long decoupler membrane track. A nonlinear lumped parameter model is developed to calculate the dynamic stiffness and loss angle. The model incorporates fluid flow in the lower chamber and variations in the support reaction force of the decoupler membrane under switching conditions. Parameters of the nonlinear lumped parameter model, including rubber stiffness, equivalent piston area, and volumetric compliance of the fluid chamber, were analyzed and calculated using the finite element method. The influence of different decoupler membrane track structures on the frequency corresponding to the minimum high-frequency dynamic stiffness was investigated based on the established model. The results demonstrate that, under high-frequency and small-amplitude conditions, increasing the decoupler membrane track length and decreasing its cross-sectional area result in a lower frequency at which the minimum high-frequency dynamic stiffness occurs. Conversely, under low-frequency large-amplitude conditions, alterations in the decoupler membrane track structure have negligible impact on the dynamic characteristics. A comparison between simulation and experimental results confirms that the developed lumped parameter model accurately represents the dynamic behavior of the hydraulic mount.

Li, Shenghao, Zhang, Shenglan, Yu, Chao, Tu, Xiaofeng, Shangguan, Wenbin

Impact of Preload and Amplitude on the High-Frequency Behaviour of Rubber Bushings in Electric Vehicles: An Experimental Study

2025-01-8254

4/1/2025

Electric vehicles (EVs) are particularly susceptible to high-frequency noise, with rubber eigenmodes significantly influencing these noise characteristics. Unlike internal combustion engine (ICE) vehicles, EVs experience pronounced variations in dynamic preload during torque rise, which are substantially higher. This dynamic preload variation can markedly impact the high-frequency behaviour of preloaded rubber bushings in their installed state. This study investigates the effects of preload and amplitude on the high-frequency dynamic performance of rubber bushings specifically designed for EV applications. These bushings are crucial for vibration isolation and noise reduction, with their role in noise, vibration, and harshness (NVH) management being more critical in EVs due to the absence of traditional engine noise. The experimental investigation examines how preload and excitation amplitude variations influence the dynamic stiffness, damping properties, and overall performance of rubber bushings under high-frequency excitation. The research methodology involves subjecting rubber bushings to various preload conditions and excitation amplitudes across relevant high-frequency domains. The findings reveal significant dependencies of dynamic characteristics on preload and amplitude, identifying critical thresholds where performance is notably affected. These insights are pivotal for optimizing rubber bushings in EVs, contributing to improved ride quality, enhanced NVH performance, and increased vehicle durability.

Hazra, Sandip, Khan, Arkadip Amitava

Computational Method of Static and Dynamic Mechanical Properties of a Rolling Lobe Air Spring

2025-01-8261

4/1/2025

To investigate the static and dynamic mechanical properties of air springs and their influencing factors, two models were established in this paper to calculate the static and dynamic mechanical properties of air springs, including a simulation model based on the finite element method and a mathematical calculation model based on thermodynamic theory. First, a performance calculation model for rolling lobe air springs with aluminum tubes was established, which considered the thickness of the bellow and the impact of the inflation and assembly process on the state of the bellow. The static and dynamic mechanical properties of air springs were calculated using this model, including static load-bearing capacity and static/dynamic stiffness. The calculation results showed that both the static characteristics of the air spring under isothermal conditions and the dynamic characteristics under adiabatic conditions were able to be calculated accurately. However, the changes in dynamic stiffness and the hysteresis phenomena caused by heat exchange during the polytropic process of the air spring are unable to be simulated by the finite element model. A mathematical calculation model was then established to analyze the mechanical properties of air spring during polytropic process. Some factors, such as heat transfer, external work and mass exchange, which cause changes in energy and temperature, were considered in the model. The dynamic characteristics of the air spring under different excited amplitudes and excited frequency were calculated using this model. The comparison of the calculation and experimental results showed that the dynamic stiffness and hysteresis characteristics of air springs across various frequencies were able to be calculated effectively by the proposed model, and the maximum relative error of dynamic stiffness and hysteresis force were less than 5%.The influence of volume, pressure, and heat exchange performance on the dynamic characteristics of the air spring were analyzed using the model. The modeling and analysis methods in this article can predict the static and dynamic mechanical properties of air springs and analyze the influence of relevant structural parameters, providing guidance and reference for designing the rolling lobe air springs.

Wang, Sirui, Kang, Yingzi, Xia, Zhao, Yu, Chao, Li, Jianxiang, Shangguan, Wen-Bin

Fixture Stiffness Impact on Spindle Coupled Multi-Axial Input Durability Test for Front or Rear Axle with Non-isolated Subframes

2025-01-8256

4/1/2025

The half vehicle spindle-coupled multi-axial input durability test has been broadly used in the laboratory to evaluate the fatigue performance of the vehicle chassis systems by automotive suppliers and OEMs. In the lab, the front or rear axle assembly is usually held by fixtures at the interfaces where it originally connects to the vehicle body. The fixture stiffness is vital for the laboratory test to best replicate the durability test in the field at a full vehicle level especially when the subframe of the front or rear axle is hard mounted to the vehicle body. In this work, a multi-flexible body dynamics (MFBD) model in Adams/Car was utilized to simulate a full vehicle field test over various road events (rough road, braking, steering). The wheel center loads were then used as inputs for the spindle coupled simulations of the front axle with a non-isolated subframe. Three types of fixtures including trimmed vehicle body, a rigid fixture with softer connections and a rigid fixture with stiffer connections are considered in the front axle simulations. The strain response on the chassis structural components is compared from the full vehicle on-field simulation to the half vehicle on-rig simulations. Results indicate that the trimmed vehicle body test is similar to the full vehicle test in strain response only for some components and events. The impact of the boundary difference (inertia-reacted in full vehicle test verses fixed-reacted half vehicle test) is substantial. It was also found that there were minor differences in strain response among the two types of rigid fixtures for most of the cases. It is concluded that the fixture stiffness impact is relatively minor if they are not able to exactly match the vehicle body stiffness. The study provides valuable insights for engineers to select the appropriate fixtures for the half vehicle spindle coupled multi-axial durability test.

Gao, Jianghua, Smith, Derek, Zhang, Xin, Yu, Xiao

Analysis and Refinement of Road Boom Noise in Electric Vehicle

2025-28-0057

2/7/2025

Customers are expecting higher level of refinement in electric vehicle. Since the background noise is less in electric vehicle in comparison with ICE, it is challenging for NVH engineers to address even minor noise concerns without cost and mass addition. Higher boom noise is perceived in the test vehicle when driven on the coarse road at a speed of 50 kmph. The test vehicle is rear wheel driven vehicle powered by electric motor. Multi reference Transfer Path Analysis (TPA) is conducted on the vehicle to identify the path through which maximum forces are entering the body. Based on the findings from TPA, solutions like reduction in the dynamic stiffness of the suspension bushes are optimized which resulted in reduction of noise. To reduce the noise further, Operational Deflection Shape (ODS) analysis is conducted on the entire vehicle to identify the deflection shapes of all the suspension components and all the body panels like floor, roof, tailgate, dash panel, quarter panel and doors at the problematic frequency. Based on ODS, the components having higher deflections at the problematic frequency is identified. Modifications are proposed to improve the dynamic stiffness of the structure at the problematic frequency and the contribution of each modification for cabin noise reduction is discussed. Solutions like tuned mass dampers (TMD) on suspension components are explored and the critical parameter which should be considered to get maximum reduction in noise with TMD is also discussed. With all the modifications, the noise levels are reduced by 5 dB (A) at problematic frequency. NVH criteria which should be considered related to suspension system to avoid boom noise concern in electric vehicle is also discussed.

S, Nataraja Moorthy, Rao, Manchi Venkateswara, Raghavendran, Prasath, Selvam, Ebinezer

A reduced-order beam modelling approach of BIW for torsional and bending stiffness optimization

2025-28-0187

2/7/2025

Noise, Vibration, and Harshness (NVH) simulations of vehicle bodies are crucial for assessing performance during the design phase. However, these simulations typically require detailed computer-aided design (CAD) models and are time-consuming. In the early stages of vehicle development, when only high-level vehicle sections are available, designing the body-in-white (BIW) structure to meet target values for bending and torsional stiffness is challenging and often requires multiple iterations. To address these challenges, this study deploys a reduced-order beam modelling approach. This method involves identifying the beam-like sections and major joints within the BIW and calculating their sectional properties (area, area moments of inertia along the plane’s independent axes, and torsion constant). These components form a simplified skeleton model of the BIW. Load and boundary conditions are applied to the suspension mount locations at the front and rear of the vehicle, and torsional and bending stiffness are calculated. The results demonstrated good accuracy compared to conventional NVH simulations. A Design of Experiments (DoE) study is also conducted on the major sections of the BIW to identify the critical beams necessary for achieving stiffness targets. Additionally, the effect of changing materials in identified sections is studied to assess potential weight reductions while maintaining target stiffness values. This approach significantly accelerates the process and proves to be highly effective in determining stiffness parameters during the conceptual stages of vehicle design.

Khan, Mohd Zishan Ali, Thanapati, Alok, Deshmukh, Chandrakant

NVH Optimization of Mounts for Reduction of Structure Borne Motor and Road Noise in Electric Vehicle

2025-28-0072

2/7/2025

Due to stringent emission norms, all OEMs are shifting focus from Internal combustion engine (ICE) to Electric vehicle (EV). NVH refinement of EVs is challenging due to less background noise in EVs in comparison with ICE vehicles. Motor whine noise is perceived inside cabin till the speed of 20 kmph. Vehicle is powered by electric powertrain (EPT). Electric powertrain is connected to the subframe with the help of three powertrain mounts. Subframe is connected to the body with the help of four mounts. With the help of Transfer Path Analysis (TPA), it is identified that the noise is structure borne and the dominant path is identified. By optimizing the stiffness of the EPT mounts, the structure borne noise levels are reduced. But reducing the stiffness of EPT mount deteriorated the road noise levels. The reason behind deterioration of road noise is investigated. The performance of double isolation of EPT is compared with single isolation of EPT with respect to both road and motor noise. Modal criteria which needs to be considered for EPT and subframe mount development in design stage with respect to road noise and structure borne motor noise is also discussed.

S, Nataraja Moorthy, Rao, Manchi Venkateswara, Raghavendran, Prasath, Selvam, Ebinezer

A Parametric Analysis of Relationship between Tyre and Braking Performances in Electric Vehicle

2024-28-0180

12/5/2024

Sports Utility Vehicles (SUVs) Braking performance is a critical parameter, and it is described by the measure of stopping distance & stability of the vehicle at a specified speed. When it comes to electric vehicles, balancing tyre performance parameters like RRc, traction, wear, ride and handling, weight and NVH is challenging due to higher axle weights, higher moment of inertia and high instant torque delivery. This study presents the braking performances of EV-intended tyres at various contact surfaces in both dry & wet conditions. Impact of tyre design attributes like tyre tread pattern, contact patch, tread compound, tyre carcass construction & characteristics studied on 3 different tyres including ultra-high-performance tyres on braking performances. This paper contains the study & analysis of 1) Footprint analysis concerning the shape of the contact patch, pressure distribution, land-sea ratio, and contact area 2)Tyre tread design such as NSD, grooves, ribs & sipes design and pitch length 3) Compound property studies like hardness, modulus, tensile strength, tear strength & elongation at break 4)Materials like polymer blend, filler ratio & new-gen materials 5)Tyre performance characteristics which are contributing to vehicle stability like lateral stiffness, longitudinal stiffness, dynamic stiffness & mu slip curves and 6) Longitudinal & lateral forces at various speed conditions with CAE Simulations. BEV requires low rolling resistance for improving vehicle range and which calls for reducing the hysteresis of tyre tread compound which affect vehicle barking performance at wet surface and it should be compensated by adjusting other design parameters. Mu slip curve very important characteristics for designing brakes system to get peak mu and programming software for ABS system.

V, Padmasri, Vellandi, Vikraman, Sundaram, Raghupathi, Singh, Ram Krishnan, P, Praveen, Chittibabu, Santhosh

Ride Comfort Efficiency of Passenger Car’s Seat Using the Structure of Negative Stiffness with Various Dynamic Models

15-18-01-0003

10/3/2024

Three dynamic models of a passenger car including the one-dimensional dynamic model, two-dimensional dynamic model, and three-dimensional dynamic model are built to evaluate the ride quality of the passenger car as well as the isolating performance of the SNS (structure of negative stiffness). The decrease of the root-mean-square (RMS) accelerations in the seat and car’s body shaking is the research goal. The investigation results indicate that under all working conditions including the various excitations of the road surface and various velocities of the passenger car, the seat’s acceleration with SNS is strongly ameliorated in comparison without SNS in all three models of the passenger car. Particularly, the RMS seat acceleration with SNS in one-, two-, and three-dimensional models is strongly reduced in comparison without SNS by 76.87%, 66.15%, and 70.59%, respectively. Thus, the seat’s SNS has a good effect in isolating the vertical vibration of the passenger car’s seat. However, in both two- and three-dimensional models, the SNS doesn’t improve the passenger car’s pitching angle. Conversely, the SNS in the three-dimensional model also has a great impact on improving the passenger car’s roll vibration. Thus, the three-dimensional model should be used to fully evaluate the isolating performance of SNS in all the vertical, pitch, and roll vibrations of the passenger car.

Zhang, Lei, Li, Tao, Yang, Guixing

Numerical Study of Application of Gas Foil Bearings in High-Speed Drivelines

2024-01-2941

6/12/2024

The commitment to environmentally friendly transportation calls for efficient solutions with the evolution of automotive industry. Turbochargers are an important part of this development. The application of Gas or Air Foil Bearings (GFB) instead of traditional hydrodynamic bearings is recently very noticed, with which the fuel consumption, and emissions can be minimized as well as decreasing the maintenance costs and increasing the reliability. However, low viscosity of gas leads to lower dynamic stiffness and damping characteristics resulting in low load carrying capacity and instability at higher speeds. Gas bearings can be enhanced by adding a foil structure commonly known as gas foil bearings whose dynamic stiffness can be tailored by modifying the geometry and the material properties resulting in better stability and higher load carrying capacity. A detailed study is required to assess the performance of high-speed rotor systems supported on GFBs, therefore in this study a bump type GFB is analyzed for its static and dynamic characteristics. The static characteristics are obtained by solving the non-linear Reynolds equation through an iterative procedure. The dynamic characteristics i.e. stiffness and damping coefficients are obtained through a perturbation method, also a direct method to evaluate the stiffness coefficients is obtained and compared. Finite difference method (FDM) is used to solve the system of equations numerically. Two methods of computing the static pressure distribution are evaluated and compared through a detailed static analysis considering the influence of different parameters i.e., eccentricity, clearance, rotor speed and foil compliance of the GFBs on the load carrying capacity. Next, the influence of different parameters of the GFBs on the dynamic stiffness and damping coefficients is also presented.

Mandapalli, Prithvi Raju, Hoefler, Dieter, Rohani, Rezvan

A Design Optimization Process of Improving the Automotive Subframe Dynamic Stiffness Using Tuned Rubber Mass Damper

10-08-02-0014

4/18/2024

Automotive subframe is a critical chassis component as it connects with the suspension, drive units, and vehicle body. All the vibration from the uneven road profile and drive units are passed through the subframe to the vehicle body. OEMs usually have specific component-level drive point dynamic stiffness (DPDS) requirements for subframe suppliers to achieve their full vehicle NVH goals. Traditionally, the DPDS improvement for subframes welded with multiple stamping pieces is done by thickness and shape optimization. The thickness optimization usually ends up with a huge mass penalty since the stamping panel thickness has to be changed uniformly not locally. Structure shape and section changes normally only work for small improvements due to the layout limitations. Tuned rubber mass damper (TRMD) has been widely used in the automotive industry to improve the vehicle NVH performance thanks to the minimum mass it adds to the original structure. Therefore, this article establishes a design optimization process utilizing the TRMD to improve the vehicle subframes DPDS more efficiently. First, the subframe critical normal modes for the DPDS issue are identified through modal participation factor analysis with the finite element (FE) model of the subframe. A lumped mass–stiffness–damper mathematical model is established by the TRMD and the identified critical modes. The parameter correlation analysis is conducted through the simple math model. Thereafter, parameter tuning is done based on the DOE study with an integrated FE model composed of the subframe and the TRMD. Furthermore, a rubber steel-type TRMD is built and verified virtually for demonstration. The proposed framework could solve the component-level DPDS problems efficiently with minimum mass and cost penalty compared to traditional methods. And it could be introduced into the subframe early design stage to ensure a lightweight final design, which meets all the component-level DPDS requirements.

Gao, Jianghua, Zhang, Xin, Yu, Xiao

Effect of Shock Absorber Friction on Vehicle Vertical Dynamics

10-08-02-0010

4/10/2024

In order to efficiently predict and investigate a vehicle’s vertical dynamics, it is necessary to consider the suspension component properties holistically. Although the effects of suspension stiffness and damping characteristics on vertical dynamics are widely understood, the impact of suspension friction in various driving scenarios has rarely been studied in both simulation and road tests for several decades. The present study addresses this issue by performing driving tests using a special device that allows a modification of the shock absorber or damper friction, and thus the suspension friction to be modified independently of other suspension parameters. Initially, its correct functioning is verified on a shock absorber test rig. A calibration and application routine is established in order to assign definite additional friction forces at high reproducibility levels. The device is equipped in a medium-class passenger vehicle, which is driven on various irregular road sections as well as over single obstacles. For all tested road sections, a linear decrease of ride comfort in terms of specific relevant vertical objective values is found by increasing the friction force. This emphasizes a definite link between suspension friction and vertical vehicle body vibration, resulting in a negative impact on vertical ride comfort. However, the longitudinal vehicle body vibration is not significantly affected. The relevance of friction in terms of transmitting the energy associated with road unevenness to the chassis in the frequency range of the chassis’ natural frequency is found to be remarkably high on smooth roads, and still considerably high on bumpy roads. The chassis and wheel resonance frequencies are significantly friction-dependent due to the damper’s slip or stick states. The results obtained from smooth road tests demonstrate the practical relevance of accurately considering friction for the given suspension type in terms of vertical ride comfort prediction.

Deubel, Clemens, Schneider, Scott Jarod, Prokop, Günther

Electric Motor Noise Reduction with Stator Mounted NVH Insert Ring

2024-01-2205

4/9/2024

Electric motor noise mitigation is a challenge in electric vehicles (EVs) due to the lack of engine masking noise. The design of the electric motor mounting configuration to the motor housing has significant impacts on the radiated noise of the drive unit. The stator can be bolted or interference-fit with the housing. A bolted stator creates motor whine and vibration excited by the motor torque ripple at certain torsional resonance frequencies. A stator with interference fit configuration stiffens the motor housing and pushes resonances to a higher frequency range, where masking noise levels are higher at faster vehicle speeds. However, this comes with additional cost and manufacturing process and may impact motor efficiency due to high stress on stators. In this paper, a thin sheet metal NVH ring is developed as a tunable stiffness device between the stator and the motor housing. It is pre-compressed and provides additional torsional rigidity to mitigate torsional excitations. A CAE model is developed to model, analyze, and optimize the NVH ring for the bolted stator configuration. A system-level simulation method is utilized to characterize the interactions of the stator, the NVH ring, and the motor housing as well as the retention force variation of the insert ring due to thermal aspects. The optimized NVH ring provides increased torsional stiffness comparable to an interference fit configuration, which leads to reduced motor noise in the critical low frequency range.

He, Song, Tran, Xuan, Naismith, Gregory, Du, Isaac, Patruni, Pavan Kumar, Baladhandapani, Dhanasekar

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