Browse Topic: Dampers and shock absorbers
ABSTRACT Model based design techniques are being used increasingly to predict vehicle performance before building prototype hardware. Tools like ADAMS and Simulink enable very detailed models of suspension components to be developed so vehicle performance can be accurately predicted. In creating models of vehicle systems, often there is a question about how much component detail or model fidelity is required to accurately model system performance. This paper addresses this question for modeling shock absorber performance by comparing a low fidelity and high fidelity shock absorber model. A high fidelity and low fidelity mathematical model of a shock absorber was developed. The low fidelity shock absorber model was parameterized according to real shock absorber hardware dimensions. Shock absorber force vs. velocity curves were calculated in Simulink. The results from the low fidelity and high fidelity model were compared to shock absorber force vs. velocity test results. New vehicle
ABSTRACT GenShock is an energy-harvesting, semi-active shock absorber. The device converts vertical travel of a vehicle suspension system to useful electricity. On defense platforms, this power ranges from a few hundred watts to several kilowatts. Conventional shock absorbers provide damping by dissipating suspension energy as heat, while GenShock provides damping by generating electricity. For an internal combustion engine (ICE) vehicle, the energy harvested by GenShock is used for reducing alternator load. The energy can also be conditioned for battery charging to address vehicle hotel loads. GenShock is also semi-active capable, in which each unit can stiffen or loosen in concert with the terrain, vehicle speed and load conditions for improved maneuverability. This paper presents a characterization of GenShock technology in its form and function of a direct replacement shock absorber that has regenerative and semi-active capabilities
Abstract RedRAVEN is a pioneered autonomous robot utilizing the innovative Linked-Bogie dynamic frame, which minimizes platform tilt and movement, and improves traction while maintaining all the vehicle’s wheels in contact with uneven surfaces at all times. Its unique platform design makes the robot extremely maneuverable since it allows the vehicle’s horizontal center of gravity to line up with the center of its differential-drive axle. Where conventional differential-drive vehicles use one or more caster wheels either in front or in the rear of the driving axle to balance the vehicle’s platform, the Linked-Bogie design utilizes caster wheels both in the front and in the rear of the driving axle. Without using any springs or shock absorbers, the dynamic frame allows for compensation of uneven surfaces by allowing each wheel to move independently. The compact and lightweight ground vehicle also features a driving-wheel neutralizing mechanism, a rigid aluminum frame, and a translucent
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
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
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
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
This SAE Aerospace Standard (AS) offers gland details for a 0.364 inch (9.246 mm) cross-section gland (nominal 3/8 inch) with proposed gland lengths for compression-type seals with two backup rings over a range of 7 to 21 inches (178 to 533 mm) in diameter. The dash number system used is similar to AS568A. A 600 series has been chosen as a logical extension of AS568A, and the 625 number has been selected for the initial number, since 300 and 400 series in MIL-G-5514 and AS4716 begin with 325 and 425 sizes. Seal configurations and design are not a part of this document. This gland is for use with compression-type seals including, but not limited to, O-rings, T-rings, D-rings, cap seals, etc
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
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
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
This SAE Standard sets forth accepted definitions and terminology of major components and parts peculiar to snowmobiles
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
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
This SAE Aerospace Information Report (AIR) covers the field of civilian, commercial and military airplanes and helicopters. This summary of tail bumper design approaches may be used by design personnel as a reference and guide for future airplanes and helicopters that require tail bumpers. Those described herein will consist of simple rub strips, structural loops with a wear surface for runway contact, retractable installations with replaceable shock absorbers and wear surfaces and complicated retractable tail landing gears with shock strut, wheels and tires. The information will be presented as a general description of the installation, its components and their functions
Modeling of shock absorbers is often used to either study and/or tune its parameters or to calculate the damping force as an input to the vehicle oscillation simulation. Shock absorber damping is accomplished by the oil resistance to flow-through restrictions. Due to their complex design and flow paths, one of the major difficulties is to determine the flow discharge coefficient and actual geometric flow area at these restrictions. This paper proposes an approach where the effective flow area (product of discharge coefficient and geometric flow area) is calculated based on the results of a simple vehicle oscillation test, combined with a shock absorber model. Governing equations are solved numerically resulting in useful dependence of the effective flow area at the absorber restrictions and the pressure differential between the compression and rebound chambers. The Methodology is described in detail. The Proposed Approach is verified by comparing the results of two-dimensional (2D
The rubber bushing is the key component to suppress vibration in the suspension system, an accurate constitutive model of rubber bushing should capture the amplitude and frequency dependency. Based on the lumped parameter model, three types of rubber bushing models are applied and compared, including the common Kelvin-Voigt model. To evaluate the model parameter and suitable frequency range, the quasi-static and dynamic tests have been performed. Comparing with the testing result, the fractional Kelvin-Voigt model combined with Berg’s friction has the minimum relative error of dynamic stiffness on the whole. Finally, two examples of chassis bushing under different loading conditions are presented. The rubber force and deflection are analyzed in both the time domain and the frequency domain, and the results show the difference of stiffness and hysteresis loop relative to frequency
Design for Six Sigma (DFSS) is an essential tool and methodology for innovation projects to improve the product design/process and performance. This paper aims to present an application of the DFSS Taguchi Method for an automotive/vehicle component. High-Pressure Vacuum Assist Die Casting (HPVADC) technology is used to make Cast Aluminum Front Shock Tower. During the vehicle life, Shock Tower transfers the road high impact loads from the shock absorber to the body structure. Proving Ground (PG) and washout loads are often used to assess part strength, durability life and robustness. The initial design was not meeting the strength requirement for abusive washout loads. The project identified eight parameters (control factors) to study and to optimize the initial design. Simulation results confirmed that all eight selected control factors affect the part design and could be used to improve the Shock Tower's strength and performance. Non-dynamic analysis Smaller-the-Better (STB) was used
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