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Technical Paper

Engine vibration-dampening (reduction) through split engine mounting arm for passenger vehicle.

2022-03-29
2022-01-0213
Automotive industry is focusing on NVH reduction and customer comfort for passenger vehicle. Structural optimization is an one of the effective tool to obtain an optimum design to achieve NVH reduction. For an internal combustion engine, there exist two basic dynamic disturbances: a) the firing pulse due to the explosion of the fuel in the cylinder and b) the inertia force and torque caused by the rotating and reciprocating parts (piston, connecting rod and crank). The usage of engine mounts is the best solution for dampening the effect of vibrations and transmitting forces between the engine and the automotive body structure. In this paper, application of structural optimization in the design of a engine mount has been carried out. Effort has been taken to develop engine-mounting arm with two different designs solution. Further, engine with two different configuration has been tested at Engine test bed and vehicle level to understand the behavior in real environment.
Technical Paper

Reduced Order Metamodel Development Framework for NVH using Experimental Data

2022-03-29
2022-01-0219
Traditional reliance on physics-based models during the design conception phase of a vehicle translates to unexplored design opportunities and missed business efficiencies. The widespread approach makes it extremely difficult to predict full vehicle response for NVH during the early design phase primarily because the available design information offers inadequate fidelity to model systems interaction. This constraint prevents identification as well as predictive analysis of potential systems interaction issues between powertrain and vehicle until physical prototypes become available. To address that restriction on the design optimization opportunities, this paper introduces an alternate approach to predict vehicle level response using regression models trained on historical measurement data. The concept is illustrated using a driveline NVH phenomenon called take-off shudder.
Technical Paper

Forming Characteristics of Very Low Carbon High strength Dual Phase Steels Produced through a Flex Mill Continuous Galvanizing Line

2022-03-29
2022-01-0239
A low carbon, lean alloyed chemistry was selected for the development of high strength dual phase (DP) steels with enhanced global and local formability. Optimized best process conditions including clean steel practices, choice of suitable casting powder, hot rolling and continuous anneal set points resulted in excellent mechanical properties and formability characteristics of DP steels. The enhanced balance of strength and formability is attributed to the optimization of the microstructure through refinement, uniformity and balancing microconstituents mechanical response and guaranteeing outstanding internal cleanliness. In this contribution, production strategy and formability characterization of DP steels with tensile strengths of 780 MPa and above relevant to automotive body structure applications will be discussed.
Technical Paper

Comparing stress gradient and other concepts for fatigue analysis of notched components

2022-03-29
2022-01-0252
Nowadays simulation of the fatigue life is an essential part of the development of components in the automotive and machinery industry. Weak points can be identified fast and reliable with respect to stiffness, strength and lightweight. A pure virtual optimization of the design can be performed without the need of prototypes. Only for the production release a final test is necessary. A lot of parameters influence the fatigue life as the local stress, material, surface roughness, size of the component, temperature etc. Notches have the strongest impact on fatigue life, depending on radius and shape. Stresses at the notch base are increased because the load flow is forced through a reduced cross section, or changes its direction around an inwardly curved edge. But notches cause not only an increase of the local stress. Also, the local fatigue strength is increased because of a support effect from the neighboring areas, where the stress is already reduced.
Technical Paper

A Perspective on Materials Selection for Body Structure Lightweighting in Battery Electric Vehicles

2022-03-29
2022-01-0233
The secular trend of automotive body structure light-weighting for internal combustion engine (ICE) vehicles is constrained by simultaneous and increasingly challenging vehicle cost, fuel economy and passenger safety standards. Mass optimization via materials selection in ICE vehicles, therefore, is ultimately dependent on the normalized cost of mass reduction solutions and the associated implications on passenger safety and vehicle performance metrics. These constraints have resulted in development and implementation of increasingly high specific-strength solutions for metallic components in the body structure and chassis. In contrast, mass optimization in battery electric vehicles is subject to alternative performance metrics to fuel efficiency, although considerations for vehicle safety and cost naturally remain directionally similar.
Technical Paper

Control strategy for ISD suspension considering dynamic vibration absorber of wheel motor

2022-03-29
2022-01-0285
Vehicles driven by in-wheel motors have the advantages of compact structure and high transmission efficiency, which is one of the most ideal energy-saving, environmentally friendly and safe driving forms in the future. However, the addition of the in-wheel motor significantly increases the unsprung mass of the vehicle, resulting in a decrease in the mass ratio of the vehicle body to the wheel, which will deteriorate the ride comfort and safety of the vehicle. To improve the vibration performance of in-wheel motor vehicles, a semi-active inerter-spring-damping(ISD) suspension based on in-wheel motor vibration absorption is proposed in this paper. Firstly, mounting elements are applied to the wheel to provide elastic isolation between the in-wheel motors and the tyre, which converts the in-wheel motor mass into a vibration absorber to suppress the high-frequency vibration of the unsprung mass.
Technical Paper

The investigation of a contact and element-based approach for Cohesive zone modelling in the simulation of Delamination propagation

2022-03-29
2022-01-0259
The CAE industry always moves towards new ways to improve the productivity, efficiency and to reduce the solution times. Conventional method of Cohesive Zone Modelling has drawback of higher computation and modelling time. Due to this problem, sometimes Engineers need to avoid simulations and rely only on some sort of approximation of crack from previous designs. This approximation can lead to either product failure or overdesign of the product. A new approach is discussed in this paper to simulate crack initiation and propagation with Cohesive Zone Modelling. Conventional method uses Cohesive zone modelling with Hex or Penta elements by assigning material with cohesive properties, which increases computation and modelling time. The new approach models Cohesive zone as contact between two bodies, thus eliminating the need to use cohesive elements which will essentially reduce the computation time as well as modelling time.
Technical Paper

Evolution and Redistribution of Residual Stress in Welded Plates During Fatigue Loading

2022-03-29
2022-01-0257
The presence of residual stresses affect the fatigue response of welded components. In the present study of a thick welded cantilever specimen, residual stresses were measured in an as-welded A36 steel sample and in a sample subjected to a short history of bending loads where substantial local plasticity is expected at the fatigue hot-spot weld toe. Extensive XRD measurements describe the residual stress state in a large region in front of the weld toe both in an untested as-welded sample and in a sample subjected to a short load history that generated an estimated 0.01 strain amplitude at the stress concentration zone at the weld toe. The results show that such a test will significantly alter the welding induced residual stresses. Fatigue life prediction methods need to be aware that such alterations are possible and incorporate the effects of such cyclic stress relaxation in life computations.
Technical Paper

Multi Body Dynamics Modeling of Launch Shudder in Electric Vehicles

2022-03-29
2022-01-0308
The continued push for faster automotive design cycles while maintaining high product quality is requiring increasing fidelity in virtual analysis. One vibration disturbance load case that has been targeted for virtual analysis improvement is launch shudder, particularly in electric vehicle applications. Launch shudder is caused by halfshaft constant velocity joint (CVJ) excitation of a powertrain mounting resonance. It is heavily dependent on the CVJ friction characteristics, axle torque, dynamic operating angles of the half shafts, the mounting system of the powertrain and the transfer path of vibration to the occupant’s seat. The need to model these parameters accurately makes a full vehicle, multi-body dynamics model a great candidate for this load case. This study introduces an approach to modeling, analysis and applications of launch shudder simulation at General Motors.
Technical Paper

An Engineering Approach to Consider Stress Concentrations in Fatigue Life Predictions on Automotive Body Structures

2022-03-29
2022-01-0261
This paper proposes a new procedure for more accurate durability predictions on the edges of structural components especially on notch regions. Current CAE procedures based on elemental stress often require iterative mesh refinement to correlate predictions to experimental cracking on the edges of components. The new proposed procedure is based on element nodal stress. It is first studied theoretically on a rectangular plate with different element sizes and options and demonstrates an improvement over elemental stress methods. It is then studied on multiple examples of experimental cracks and successfully predicts issues where current elemental stress methods do not. In addition, it avoids the iterative mesh refinement associated with current methods. In summary, the new method based on nodal stress is more accurate, more efficient, and improves first time through capability on the edges of structural components.
Technical Paper

Effect of Aero Covers on Underfloor Wind Noise; Conclusions from a Wind Tunnel Validated, Aero-Vibro-Acoustic Model

2022-03-29
2022-01-0310
Low frequency interior wind noise is typically dominated by underfloor flow noise. The source mechanisms are fluctuating surface pressure loading from both turbulence and acoustic field levels developed in the semi-reverberant cavity between floor and road. Previous studies have used computation fluid dynamics (CFD) to estimate the aero-acoustic loading applied to a vibro-acoustic model, which is then used to predict the transmitted interior wind noise. This paper reports a new perspective in two respects. First it uses sophisticated surface pressure microphone arrays to directly measure the underfloor aero-acoustic loading in the wind tunnel. Second, it considers two different underfloor aerodynamic configurations – with and without lightweight aero cover panels, which are installed primarily to reduce aerodynamic drag.
Technical Paper

Efficient acoustic trim components results recovery for industrial finite elements models

2022-03-29
2022-01-0309
In the automotive industry, acoustic trim components are playing an essential role in the vehicle Noise, Vibration and Harshness (NVH). They act in three different ways: reducing the structure vibration, absorbing incident acoustic waves and reducing both the structure-borne and air-borne noise transmission. Mastering acoustic trims is key for interior acoustic comfort and a major differentiator in terms of customer appreciation. An elegant and efficient way to solve fully trimmed vehicle models numerically is the well documented and widely used Reduced Impedance Matrix (RIM) method. It solves the structure and cavity in modal coordinates, while the acoustic trim components are solved in physical coordinates where their complex damping behavior can be fully captured. This method is very accurate to compute structure and cavity results but couldn’t initially recover data such as pressure or displacement inside the acoustic trim parts.
Technical Paper

Prediction and identification of vehicle rattle noise caused by shock absorbers

2022-03-29
2022-01-0304
A novel technology is proposed to predict vehicle rattle noise caused by shock absorbers. The model of shock absorber is developed by analyzing the force of moving parts, hydronic characteristic of valves and physical characteristic of oil. The model of mount, fixed between shock absorber and vehicle body, is developed with Maxwell method of combining series of spring and damping components. The characteristics of mount are measured under the specified frequency and amplitude conditions, the spring and damping coefficients of Maxwell model are identified using the measured data. The model of spring is developed by curve interpolation of measured data, considering the hysteresis properties of the real spring. The mass, wheel base etc. data of real vehicle are measured and the model of vehicle body is developed by Carsim using the measured data.
Technical Paper

Simulating HVAC Noise in Vehicle Cabin with Material Absorption Modelling

2022-03-29
2022-01-0302
Design of HVAC system plays an important role in acoustic comfort for passengers. With automotive world moving towards electrical vehicles where powertrain noise is low, designing low noise HVAC system is becoming more important. For an automobile manufacturer, ability to predict the production vehicle cabin noise at the early design stage is important as it allows more freedom for design changes, which can be incorporated in the vehicle at lower cost. Although HVAC prototype and system level testing at early design stage is possible for noise estimation but flow field is not visible in test that makes difficult to improve design. CFD simulation can provide detailed information on flow field, noise source strength and location. But in such a simulation, accurate prediction has been a challenge due to the inability of CFD tools to model acoustic absorptive characteristics of interior walls of cabin.
Technical Paper

Identification of vehicle noise based on transfer path and condition power spectrum analysis

2022-03-29
2022-01-0306
The identification of vehicle noise is the basis for studying the acoustic characteristics of vehicles. In this paper, both excitation of noise sources and response of interior noise were identified. Firstly, a transfer path analysis (TPA) model was established to identify the excitation of noise sources, which includes vehicle main noise sources, such as engine, tires, exhaust pipe and mufflers. Based on the operational signals and transfer function which were tested in the vehicle semi-anechoic room, we identified the excitation of noise sources using inverse matrix method. Identify result indicated that tires have higher excitation amplitude than engine in high frequency band. Therefore, the transfer path between the tire and the cabin, such as carpet and windshield, should be taken as the focus of acoustic performance improvement. By improving the acoustic material on the transfer path, the loss of sound in the transmission path will be increase.
Technical Paper

Design of Muffler in Reducing Hiss Noise of Turbocharged Vehicles

2022-03-29
2022-01-0315
The application of turbochargers in fuel vehicles brings high-frequency noise, which seriously affects the vehicle's ride comfort. The hiss noise of a turbocharged car is improved in this paper. Firstly, under different operating conditions and whether the air intake system is wrapped, the noise in the vehicle cabin and the driver's right ear is tested, and the noise sources and noise characteristics are identified. Then, the acoustic calculation model of the muffler is established, and the transmission loss(TL) of the original muffler behind the turbocharger(MBT) is calculated. The TL of the muffler is measured by the double-load impedance tube method. The finite element calculation model is verified by comparing the TL of muffler calculated with tested. Thirdly, the MBT is redesigned. The improved muffler significantly improves the performance of eliminating high-frequency noise, and its TL beyond 20 dB is expanded to the band of 1600 ~ 3500 Hz.
Technical Paper

Parameter Analysis and Optimization of Road Noise Active Control System

2022-03-29
2022-01-0313
The parameter setting has a great influence on the noise reduction performance of the road noise active control (RNC) system. This paper analyzes and optimizes the parameters of the RNC system. Firstly, the model of the RNC system is established based on the FxLMS algorithm. Based on this model, taking the maximum noise reduction as the evaluation index, the sensitivity analysis of convergence coefficient, filter order, and reference signal gain was carried out using the Sobol method with the data measured by a real vehicle on asphalt pavement at 40km/h. The results show that there is no significant interaction between the three parameters. Then, using the idea of orthogonal experiment, the simulation results of the control model are analyzed by taking the maximum noise reduction as the evaluation index. It is found that the convergence coefficient has the greatest effect on the maximum noise reduction, followed by the filter order, and the reference signal gain has the least effect.
Technical Paper

Optimal chassis suspension design for towbarless aircraft tractor taxiing system vibration isolation

2022-03-29
2022-01-0291
The towbarless aircraft tractor taxiing system (ATTS) is composed by the tractor vehicle and the aircraft, of which the nosewheel is lifted and transmit the power driven by the tractor to the aircraft, and the aircraft is towed to the destination in a long distance with a high speed of about 40 km/h. Compared to the traditional aircraft traction with the speed of 5 km/h and about 50 m distance, the ATTS can increase the airport operation efficiency and economy. However, the ATTS vibration becomes one significant problem, which will reduce the driver’s ride comfort and failure to the system structure, as the traction velocity increases and the tractor lacks of the chassis suspension. Due to the excellent vibration isolation characteristics, the air suspension is considered to install on the tractor, and the dynamic model of the ATTS with air suspensions is derived.
Technical Paper

Studies on the dynamic characteristics of vibration energy recovery system

2022-03-29
2022-01-0288
The vehicle suspension plays a significant role in alleviating the vibrations translated from the rough road and most of the vibrations are dissipated by the hydraulic shock absorber. Vibration energy harvesting technology is widely concerned for the self-powered wireless sensor system in intelligent vehicle. However, the system dynamic characteristics changes due to the coupling between the vibration and electro-magnetic induction. Mechanical electromagnetic coupling is investigated in this paper, a quarter vehicle vibration energy recovery model including electromagnetic system is established. And this paper focuses on the dynamic stiffness and normalized damping, which are often ignored by researchers. A harmonic excitation is applied to the vehicle suspension, and the dynamic stiffness and damping in time domain is studied by changing the frequency of harmonic excitation.
Technical Paper

Managing Trust along the CAN Bus

2022-03-29
2022-01-0119
Multiple approaches have been created to enhance intra-vehicle communications security over the past three decades since the introduction of CAN. The twin pair differential-mode communications bus is tremendously robust in the face of interference, yet physical access to the bus offers a variety of potential attack vectors whereby false messages and/or denial of service are easy to achieve. This paper seeks to evaluate extensions of a common-mode watermark-based authentication technique recently developed to improve authentication on the CAN bus by considering the watermark as a side-channel communications means for high value information. We also describe a variety of higher layer algorithms, with benefits and pitfalls, for employing the watermark as a physical-layer firewall. All of these results are backed by a software-defined radio (SDR) based hardware testbed.
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