Browse Topic: Dampers and shock absorbers
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.
A futuristic vehicle chassis rendered in precise detail using state-of-the-art CAD software like Blender, Autodesk Alias. The chassis itself is sleek, low-slung, and aerodynamic, constructed from advanced materials such as high-strength alloys or carbon-fibre composites. Its polished, brushed-metal finish not only exudes performance but also emphasizes the refined form and engineered details. Underneath this visually captivating structure, a sophisticated system of self-hydraulic jacks is seamlessly integrated. These jacks are situated adjacent to the four shock absorber mounts. These jacks are designed to lift the chassis specifically at the tyre areas, and the total vehicle, ensuring that underbody maintenance is efficient and that, in critical situations, vital adjustments or emergency lifts can be performed quickly and safely. The design also incorporates an intuitive control system where the necessary buttons are strategically placed to optimize driver convenience. Whether positioned alongside the steering wheel for immediate reach, integrated near the infotainment display for multifunctional control, or mounted within the driver's side door for easy access, these controls underscore a blend of technology and practicality.
A semi-active suspension system provides superior safety, ride, and handling performance for a vehicle by continuously varying the damping based on vehicle motions, where semi-active hydraulic damper (SAHD) is the most critical component. Today, SAHD’s are standard in most of the premium segments of vehicles and optional extras in mid-size and compact vehicle segments. Electric vehicles require larger sized SAHD’s to meet heavier vehicle loads and meet ride and handling requirements. The aim of this paper is to highlight the design and development methodology of a base valve for larger bore-size for semi-active hydraulic damper. The workflow follows to present a process for base valve design to meet structural strength and, the key steps of design calculations of the hydraulic performance. The design of the base valve and suction disks architecture was engineered with the aid of Computer Aided simulations. The structural performance was analyzed using the Finite Element Analysis (FEA) and valve hydraulic performance factors were obtained by using Computational Fluid Dynamics (CFD) methods to simulate the physics of hydraulic fluid flow around the base valve assembly using the de-coupled fluid /structure interaction (FSI) method. In this effort, the analytical study was reinforced to identify the critical performance parameters such hydraulic pressure (P) - oil discharge (Q) curve generation and understand the base valve design performance. Furthermore, valve characterization using flow bench testing was conducted to validate and correlate the simulation predictions with prototype samples to increase the confidence level in computer aided simulations.
A damper is one of the most important elements in a vehicle suspension system. The damper valves are a fully coupled hydraulic system where the suspension fluid flow interacts with the elastic response of the valve structure. The base valve in the hydraulic damper plays a significant role in compression damping force characteristics of a damper, and therefore designing of the base valve is critical for damping force tuning. In this paper, the impact of the base valve design complexity reduction is quantitatively analyzed. The Current base valve design is restrictive which prevents achieving the required compression damping force ranges without a substantial base valve body parts library. A new base valve assembly is suggested with one more degree of freedom via a restrictor plate. Introducing this new element allows reducing the number of base valve designs for damping performance tuning. The design of the new base valve is engineered from existing designs with the aid of computer aided simulation for improving the tuning range of the damper with reduced number of valve body parts. Finite Element (FE) methods are utilized to evaluate the new base valve structural strength and validated by conducting experimental structural hub crush strength test. For the hydraulic performance of the new base valve design, Computational Fluid Dynamics (CFD) simulations were carried out for meeting damping force requirement. A test flow bench was built to validate the computational models. The new base valve is also a cost-effective solution to meet compression damping force tuning range and resolution.
This study delves into the microstructural and mechanical characteristics of AlSi10Mg alloy produced through the Laser Powder Bed Fusion (L-PBF) method. The investigation identified optimal process parameters for AlSi10Mg alloy based on Volume Energy Density (VED). Manufacturing conditions in the L-PBF process involve factors like laser power, scan speed, hatching distance, and layer thickness. Generally, high laser power may lead to spattering, while low laser power can result in lack-of-fusion areas. Similarly, high scan speeds may cause lack-of-fusion, and low scan speeds can induce spattering. Ensuring the quality of specimens and parts necessitates optimizing these process parameters. To address the low elongation properties in the as-built condition, heat treatment was employed. The initial microstructure of AlSi10Mg alloy in its as-built state comprises a cell structure with α-Al cell walls and eutectic Si. Heat treatment caused the collapse of the eutectic Si cell walls, and a needle-shaped Mg2Si precipitated phase formed within α-Al. These changes became more prominent with higher heat treatment temperatures and times. Interestingly, increasing heat treatment temperature and time resulted in lower strength but higher ductility in the mechanical properties. Thus, finding optimal heat treatment conditions is crucial to achieving the desired material properties. Furthermore, the study explored the microstructural properties, compression behavior, and energy absorption properties of lattice structures fabricated using the L-PBF method. Leveraging the previously derived optimal process parameters for L-PBFed AlSi10Mg alloy improved internal and surface quality even in thin lattice structures. Analyzing shock absorption characteristics with the application of lattice structures revealed that the L-PBF method's advantage lies in its ability to create complex shapes. This versatility enables incorporating both bulk geometry and lattice structure in a single part using AlSi10Mg alloy. Applying this technique to a shock absorber housing demonstrated excellent durability and achieved a 27% reduction in weight.
Automotive dampers are essential vehicle components regarding vehicle dynamics by keeping the road contact and reducing wheel load fluctuations. So damper degradation could not only significantly influence driving comfort but also the dynamics and therefore driving safety. The aim of this study is to expand knowledge about the behavior of passive automotive twin-tube dampers degraded by loss of oil and pressure. This serves to improve the understanding of inner processes of the damper and modeling the behavior of degraded dampers. To analyze the damper behavior, an intact damper has been modified and validated to allow adjusting the oil and pressure level. Using a dynamic hydraulic damper test rig a preconditioning routine for degraded dampers is developed. With this routine, a wide measurement program at various amplitudes, frequencies, oscillations, and damper configurations is carried out and the obtained results are discussed. The conducted measurement program did not cover small amplitudes (<8.4 mm) and high frequencies (>19 Hz). The results show that the loss of oil or pressure leads to complex dependencies on all varied parameters such as amplitude, frequency, number of oscillations, and waiting time between two measurements. While the absence of pressure only leads to small performance reductions, especially the loss of oil leads to significant deterioration of the damper performance. Already at a level of 90% of the original oil volume, the examined damper loses up to 30% of its performance under disadvantageous operating conditions. Furthermore, the loss of oil can make a damper almost useless when 40% of the oil is still present.
As the automotive industry undergoes significant changes in the dynamic behavior of vehicles and increasing demand for rapid product design, accurate prediction of product performance in the early stages has become more crucial than ever in the competitive environment. Shim-stack-type hydraulic dampers are widely used in automotive parts for both internal combustion engine (ICE) vehicles and electric vehicles (EV). EVs are even more sensitive to damper performance as ICE, which is a major NVH source has been removed. However, the industry still faces challenges in obtaining accurate models of dampers due to their highly nonlinear hydro-mechanical behavior. Bleed slits in a shim-stack-type hydraulic damper play a key role in determining the blow-off characteristics of dampers, and therefore, accurate prediction of the blow-off characteristics is crucial in evaluating the damping performance of a vehicle. Bleed flow analyses are conducted at two levels: component level and assembly system level. For the component level analysis, computational fluid dynamics (CFD) is utilized to analyze bleed flow characteristics corresponding to various bleed slits, which are validated by conducting experimental flow bench tests. For the assembly system level analysis, a dynamic 1-dimensional (1-D) system model is developed for a target passive hydraulic damper to evaluate the effect of bleed slits on the assembly level. The damper characteristic of the proposed method and a conventional method with a constant discharge coefficient are compared. An experimentally measured damper characteristic from a dynamo is used to validate the system model.
The sensitivity of the brake dive of a sport utility vehicle (SUV) was analyzed using a five-degree-of-freedom (5-DoF) lumped-mass model and design of experiments (DoE). A program was developed and validated using Visual Basic for Applications (VBA). The analysis parameters used actual kinematics and compliance (K&C) data without linear assumptions, enabling detailed numerical and systematic descriptions of previously unorganized knowledge obtained from the experiences of tuning engineers. The initial shock and residual ripple of the nose-dive angle were defined as DoE performance metrics, and the required suspension parameters and shock absorber piston speeds were identified. The initial shock was greatly influenced by the rear and front spring forces, followed by the rear rebound damping, rear anti-lift force, and front anti-dive force. Further, the residual ripple was highly sensitive to the front and rear rebound damping forces. The initial shock can be improved to some extent by applying only shock absorber tuning to effectively reduce the residual ripple.
This research provides preliminary guidance for laboratory testing of marine shock isolation seats. The purpose of the test is to demonstrate the effectiveness of a passive seat in reducing simulated wave impact loads in a laboratory before installation in a high-speed planing craft.
Passenger vehicles are used as one of the frequently used and versatile mode of transport. Commercial buses cater to short to long distance travel for city as well as highway applications. Thus, passenger ride comfort becomes paramount for the salability of the vehicle. Generally, it is observed that the rear seat experiences the worst ride comfort characteristics due to rear overhang and pitching characteristics of buses. Therefore the objective of this project is to improve the rear seat vibrations of passenger bus by tuning damper characteristics. Shock absorbers, being a low cost and easily interchangeable component is tuned first before optimizing other suspension parameters. The methodology is as follows: first, a 4 degree of freedom mathematical model is created on MATLAB Simulink R2015a environment. Time domain data is obtained by road load data analysis and used as an input for the mathematical model. An experimentation was carried out on the bus at speeds of 20 km/h over a single hump to obtain actual acceleration time domain data. The model is then correlated with actual test over a single hump. After setting up baseline results, tuning of damper is carried out. First low speed compression range is tuned to obtain better ride comfort characteristics over Class A road and results are observed. This is done by varying the damping force from 5kgf to 100kgf in speeds between 0.05 m/s to 0.25 m/s in compression. Thereafter, high speed rebound range is tuned over a single hump by varying the damping force between 1000 kgf to 4000 kgf in speeds between 1m/s to 3 m/s in rebound travel and results are obtained. Finally, fitment of data in Ride Comfort Index is carried out as per ISO 2631. Therefore a comprehensive and parametric damper tuning sheet is prepared considering the natural frequency, critical damping coefficient and damping ratio.
Coil springs are crucial components of the clutch damper. Quantifying the stresses accumulated on them during operation is crucial in the prediction of remaining usable spring life. This paper demonstrates the use of a mathematical model-based approach in predicting the behavior of localized stresses on the spring used in clutch dampers. An equivalent cantilever beam model for spring coils solved using the theory of elastic stability is utilized to predict the spring response in operation, a contact model that translates the spring response into localized stresses due to wear and iterative wear model that accounts for surface morphology and change in geometry due to wear is illustrated in this paper for the prediction of wear.
The conventional approach in aircraft landing loads analysis, such as for shock absorber development, is using a nonlinear set of equations and a modal representation of the airframe. For preliminary shock absorber design studies, a linearized set of equations may provide a highly efficient simulation method to limit the parameter space of linear shock absorber models. This article develops a set of linearized equations of motion to simulate the landing touchdown event while capturing airframe flexibility effects using a transfer function. The linearized flexible model demonstrates the ability to generally capture flexibility effects and output responses of interest with a significantly reduced simulation time compared to both fully flexible and nonlinear reduced-order models. The linearization of a Fiala tire model is accomplished by scaling the longitudinal tire stiffness such that the peak tire drag force matches that of the nonlinear model, and the vertical tire stiffness is obtained from a linear regression of a nonlinear vertical force versus deflection curve through an expected range of tire deflection.
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