Vehicle Finite Element Model Research Articles

A Study on the Mid-frequency Tire-Sourced Cabin Noise in Electric Vehicles

ABSTRACT This study investigates and provides a framework for addressing a reported tire- sourced cabin noise in the mid-frequency range of 300–500 Hz for an electric vehicle (EV). Noise, vibration, and harshness (NVH) of EVs present new challenges compared with internal combustion engine vehicles because of significant design changes between the two vehicle types. In turn, the tire–road interaction noise becomes a more significant source of cabin noise in EVs. In this regard, some prominent EV manufacturers recently reported relatively high measured cabin noise, particularly in the mid-frequency range of 300–500 Hz. Identifying the root cause(s) of noise in that range is a challenging task, as both tire structure–borne and airborne sources are contributors in that frequency range of elevated noise. The current work presents the results of an experimental modal analysis to provide insight into some potential sources of the reported noise for an all-season tire/wheel assembly designed for an EV. The subsequent parametric simulations, conducted via the tire–vehicle finite element model, evaluate some of the mitigation solutions for the reported noise.

Validation of a generic finite element vehicle buck model for near-side crashes

Objective Finite element (FE) reconstructions of motor vehicle crashes using human body models are effective tools for developing a better understanding of occupant kinematics and injuries in real-world lateral crash conditions, but current near-side reconstruction methods are limited by the paucity of full-scale FE vehicle models. The objective of this study was to validate a generic vehicle model equipped with left-side airbags and intrusion capability by simulating a series of near-side crash tests for a range of vehicles and assessing model accuracy using objective evaluation methods. Methods Moving deformable barrier crash tests were reconstructed for five common vehicle classifications (compact passenger, mid-size passenger, sport utility vehicle, pickup truck, and van) using an updated version of a previously developed simplified vehicle model. Unknown vehicle and intrusion properties (pretensioner force, seatback airbag pressure, curtain airbag pressure, door panel stiffness, ratio of dynamic-to-static intrusion, intrusion velocity, and intrusion scaling factor) were estimated by parameterizing them across 224 simulations per crash test using a Latin hypercube design of experiments. Model accuracy was assessed for 13 anthropomorphic test device signals using the Correlation and Analysis (CORA) objective rating method and injury metric comparisons. Results Maximum ratings of 0.69, 0.67, 0.52, 0.52, and 0.62 were achieved for the compact passenger, midsize passenger, sport utility vehicle, pickup truck, and van classifications, respectively. On average, the abdomen displayed the most accurate behavior (0.51 ± 0.12), followed by the thorax (0.50 ± 0.10) and head (0.50 ± 0.07). The pelvis displayed the least accurate behavior (0.46 ± 0.18) of any region. Reconstructions overpraedicted injury metrics in all cases. Conclusions All vehicles achieved “fair” biofidelity ratings and the compact passenger and midsize passenger vehicles achieved “good” biofidelity ratings, validating them for kinematic evaluations with vehicle-to-vehicle nearside crash reconstructions. Regression models were developed for injuries and CORA ratings and can be used to optimize vehicle parameters in future studies.

A method for generating case-specific vehicle models from a single-view vehicle image for accurate pedestrian injury reconstructions

Developing vehicle finite element (FE) models that match real accident-involved vehicles is challenging. This is related to the intricate variety of geometric features and components. The current study proposes a novel method to efficiently and accurately generate case-specific buck models for car-to-pedestrian simulations. To achieve this, we implemented the vehicle side-view images to detect the horizontal position and roundness of two wheels to rectify distortions and deviations and then extracted the mid-section profiles for comparative calculations against baseline vehicle models to obtain the transformation matrices. Based on the generic buck model which consists of six key components and corresponding matrices, the case-specific buck model was generated semi-automatically based on the transformation metrics. Utilizing this image-based method, a total of 12 vehicle models representing four vehicle categories including family car (FCR), Roadster (RDS), small Sport Utility Vehicle (SUV), and large SUV were generated for car-to-pedestrian collision FE simulations in this study. The pedestrian head trajectories, total contact forces, head injury criterion (HIC), and brain injury criterion (BrIC) were analyzed comparatively. We found that, even within the same vehicle category and initial conditions, the variation in wrap around distance (WAD) spans 84–165 mm, in HIC ranges from 98 to 336, and in BrIC fluctuates between 1.25 and 1.46. These findings highlight the significant influence of vehicle frontal shape and underscore the necessity of using case-specific vehicle models in crash simulations. The proposed method provides a new approach for further vehicle structure optimization aiming at reducing pedestrian head injury and increasing traffic safety.

Multi-criteria structural optimization of a hood inner structure using machine learning technique

This article presents an efficient multi-criteria structural optimization process based on machine learning for shape and size optimization of the hood inner. For this purpose, a low dimensional parameterization based on two-dimensional mapping and dimensionality reduction is used to decrease the number of design variables. There are many design parameters to be considered for designing this structure. In this study, the effect of three important criteria consisting of head injury, eigenfrequency, and static load were analyzed. A full vehicle finite element model is prepared for a newly developed product because head injury analysis requires a full vehicle model due to contact with the inner components of the engine compartment. Then, an experimental study is performed based on the real test scenario for model verification. A new rating method for analyzing the head injury criteria evaluated in different points is proposed and different machine learning techniques are compared in the approximation of the objective function. Finally, the problem is solved as both single and multi-objective optimization problems. Results present considerable improvement in accuracy and efficiency in the identified structure while the method has a low computational cost and the implementation is not difficult.

Advances in Methodology for Fatigue Assessment of Composite Steel–Concrete Highway Bridges Based on the Vehicle–Bridge Dynamic Interaction and Pavement Deterioration Model

Fatigue cracking is one of the most prominent causes of mechanical failure limiting the service life of existing steel and composite steel–concrete bridges and is among the central concerns of structural and bridge engineers. In this context, the current work presents some recent advancements in an existing methodology for fatigue analysis developed by the authors throughout the years. The methodology is specifically devoted to the fatigue assessment of composite steel–concrete bridges employing the local hot-spot S-N approach and a coupled vehicle–pavement–bridge system considering progressive pavement deterioration with stochastically generated roughness profiles. Two different methodologies were used to solve the dynamic equilibrium equations: the modal superposition method to solve the bridge dynamic equations and a direct integration method to solve the vehicle dynamic equations. From a computational point of view, the present approach is more efficient and detailed than previous versions, as it allows a significant reduction in the analysis time and the use of complex bridge and vehicle finite element models. In this regard, a case study of a highway composite steel–concrete bridge spanning 40 m was selected in order to demonstrate the usefulness of the presented improved methodology by carrying out a fatigue analysis. The results of this investigation (displacements and stresses) are presented, aiming to verify the factors that directly influence the structural response and, consequently, the service life of steel–concrete composite highway bridges.

Research on interior noise optimization of minibus based on vibration transfer path analysis using super element method

In this paper, aiming at the problem of excessive low-frequency noise in a minibus, the SEM (Super Element Method) was applied to the NVH (Noise, Vibration and Harshness) dynamics simulation analysis of the vehicle, and the vibration and noise control schemes were proposed from the aspect of vibration transfer path to improve NVH performance. First, the relationship and difference between SEM and LFEM (Legacy Finite Element Method) were elaborated theoretically. Afterward, the legacy finite element model of the full vehicle, which comprehensively considered all related components such as BIW (Body In White), chassis, door covers, body accessories and interior and exterior trims, was established based on LFEM. Furthermore, the subsystems of legacy finite element model of the vehicle were divided into super elements based on SEM, and the differences between SEM and LFEM in model processing were discussed in detail. In addition, the modal analysis and frequency response analysis of the full vehicle were carried out by LFEM and SEM respectively, and the computational results were compared with the testing results to verify the simulation accuracy and feasibility of the SEM in solving the vehicle body dynamics problems. Meanwhile, through the comparison of simulation analysis process of SEM and LFEM in practical case, the advantages of SEM compared with LFEM were discussed in terms of computational efficiency and storage space occupied. Finally, the stiffness optimization schemes of rubber bushing in the middle of driveshaft were proposed to improve vibration and noise from the aspect of vibration transfer path, and the testing results verified the effectiveness of the optimization schemes in reducing the low frequency noise inside the vehicle. The study concluded that SEM had obvious advantages over LFEM in terms of computational efficiency and storage space occupied, while ensuring the computational accuracy basically consistent with that of LFEM.

A Novel Simplified FE Rail Vehicle Model in Longitudinal and Lateral Collisions

It is a challenge to efficiently and accurately predict train dynamic responses during complex collisions. In this paper, a novel numerical simplification method for high-speed rail vehicles during complex impact configurations is proposed. The central section of high-speed rail vehicles is a sandwich corrugated hollow double-shell structure. Starting with a baseline detailed finite element (FE) model of a high-speed train, the central section was first simplified as a solid single-shell structure. A parametric study with various simplification thickness ratios of the simplified FE rail vehicle model in different longitudinal rigid-wall collisions and lateral rigid-cylinder impacts was then performed using LS-DYNA. Furthermore, a correlation and analysis (CORA) objective rating method was used to evaluate the related responses between the simplified and detailed baseline FE rail vehicle models. The results demonstrate that the simplified FE model could effectively predict the rail vehicle impact responses. The displacement and impact force time histories of the simplified vehicle model with a thickness ratio of 0.38 matched closely with the results of the baseline detailed FE model under both longitudinal and lateral impacts (total combined CORA rating score: 93%). The rail vehicle impact deformations of the simplified vehicle model were similar to those of the baseline detailed model. The application of the simplified vehicle FE model substantially reduced the computational time (approximately 55% reduction). This work provides a solid basis for efficiently exploring train impact responses in complex collisions, and will be especially useful for train occupant injury assessment.

Fundamental investigation of structural design optimization of guardrails based on collision simulation

Guardrails are essential structures for protecting vehicles and saving human lives when traffic accidents occurred. When a vehicle collides with a guardrail in the traffic accident, some kinetic energy of the moving vehicle can be absorbed or reduced by the guardrail according to its energy absorption capacity. In the present work, we aim to investigate structural design optimization of guardrails based on collision simulation to enhance their energy absorption capacities. To reproduce a real collision condition for structural design optimization of guardrails, in the collision simulation of a vehicle collides with guardrails, we construct the finite element model of the guardrail considering details of the shape of the guardrail, the bolts connecting the guardrail and the post, and the efficient model of soil. A verified finite element model of vehicle is adopted for real collision simulation. According to the results of collision simulation, we perform structural design optimization of the guardrail using the optimization method of central composite designs, where three design variables representing its cross-section shape are chosen. For the results, collision simulations using the constructed finite element models of the guardrail and the vehicle were smoothly performed. At last, based on the optimization method of central composite designs, the optimal cross-section shape of the guardrail was determined, which could absorb the most kinetic energy of the moving vehicle.

Targeting the acceleration-time response of vehicle structures under crash impact using equivalent dynamic loads

This work introduces an optimization procedure derived from the targeting force-displacement response (TFDR) method to improve the crashworthiness of full-size vehicle structures. The proposed method aims at targeting the vehicle’s acceleration-time response (ATR) under a crash event using topometry (thickness) optimization. In contrast to the original TFDR method, the proposed targeting method uses a moving coordinate system (MCS) that allows addressing fully dynamic crash models with initial velocity. By setting a proper target ATR curve, the proposed method can improve several crashworthiness indicators including specific energy absorption, maximum deceleration, dynamic penetration, and crash load efficiency. The result of the topometry optimization could be a guideline for the further design. In the proposed method, the nonlinear optimization problem is discretized into a series of analytical subproblems using equivalent dynamic load (EDL). In each iteration, the dynamic response from an explicit dynamic finite element (FE) analysis is utilized to define and solve a subproblem. To demonstrate the proposed iterative method, the baseline FE model of a Dodge Grand Caravan vehicle, obtained from the US National Highway Traffic Safety Administration (NHTSA) website, is optimized. The results show the effectiveness of the algorithm finding the element thickness distribution to make the acceleration-time response of the vehicle’s center of gravity (VCG) gradually approach a target curve. The proposed EDL algorithm finds a converged solution using less than 15 crash simulations. This makes it possible to solve problems involving full-size vehicle FE models.

Reconstruction finite element model of cars

The experimental method used in a frontal crash of cars costs much time and expense. Therefore, numerical simulation in crashworthiness is widely applied in the world. The completed car models contain a lot of parts which provided complicated structure, especially the rear of car models do not contribute to behavior of frontal crash which usually evaluates injuries of pedestrian or motorcyclist. In order to save time and resources, a simplification of the car models for research simulations is essential with the goal of reducing approximately 50% of car model elements and nodes. This study aims to construct the finite element models of front structures of vehicle based on the original finite element models. Those new car models must be maintained important values such as mass and center of gravity position. By using condition boundaries, inertia moment is kept unchanged on new model. The original car models, which are provided by the National Crash Analysis Center (NCAC), validated by using results from experimental crash tests. The modified (simplistic) vehicle FE models are validated by comparing simulation results with experimental data and simulation results of the original vehicle finite element models. LS-Dyna software provides convenient tools and very strong to modify finite element model. There are six car models reconstructed in this research, including 1 Pick-up, 2 SUV and 3 Sedan. Because car models were not the main object to evaluate in a crash, energy and behavior of frontal part have the most important role. As a result, six simplified car models gave reasonable outcomes and reduced significantly the number of nodes and elements. Therefore, the simulation time is also reduced a lot. Simplified car models can be applied to the upcoming frontal simulations.

Parameter sensitivity analysis of pedestrian head dynamic response and injuries based on coupling simulations.

There are a very limited number of reports studying on the dynamic response and injuries of pedestrian head in the scenarios with head hitting windshield. This study aims to investigate the significant factors that affect the dynamic response and injuries of pedestrian head through finite element-multi-body coupling simulations. Two finite element vehicle models and two multi-body pedestrian human models were used to build the coupling simulations. Orthogonal experimental design and analysis of variance were used for parameter combination and data analysis. This study demonstrated that the dynamic response of pedestrian head and HIC15 were strongly associated with collision speed and pedestrian orientation. Vehicle type had a significant influence on the dynamic response of pedestrian head and HIC15, while there was no significant relationship between the dynamic response of pedestrian head and HIC15 and the size of pedestrian human models. Collision speed, pedestrian orientation, and vehicle type should be prioritized over the other collision parameters in the study of head injury mechanism and reconstruction of vehicle-pedestrian collisions in the scenarios with head hitting windshield.

Study of structural optimization design on a certain vehicle body-in-white based on static performance and modal analysis

Abstract The intensity analysis was proposed for a certain all-aluminum vehicle body-in-white, and an optimistic method of the vehicle body was carried out based on lightweight target. The finite element model of vehicle body-in-white was established, and the flexural rigidity and torsional rigidity of the vehicle body are calculated according to the actual operating conditions of the vehicle. The flexural rigidity and torsional rigidity of the vehicle body are calculated, and the main opening deformation of the vehicle body under these two working conditions was studied. Finally, based on the thickness of the body panel, the structural sensitivity analysis of the vehicle body was carried out. According to the sensitivity analysis data, the optimization variable is determined with lightweight as the target, and the vehicle body structure is optimized. The results showed that the static and dynamic performance indexes of the white body were higher than the standards of similar motorcycle type at home and abroad, the bending stiffness of the structurally improved basic model after sensitivity optimization was reduced by 2.1% compared with before optimization, but still much higher than the target reference value (122,000 N/mm). And the quality of the vehicle body was reduced, which met the lightweight requirements of optimized design after the optimization of the thickness of the improved basic model.

Safety analysis of children transported on bicycle-mounted seat during traffic accidents

The paper concentrates on the safety analysis of children transported in bicycle-mounted baby carriers. The biomechanics are widely researched for pedestrians and cyclists, but there is no clear understanding of children’s kinematics during accidents in commonly used baby carriers. Using a finite element vehicle model coupled with a multibody bicycle, dummies and a generic baby carrier, the authors numerically simulated various impact scenarios. The results of the simulations proved a complex motion of the bicycle. Validation of the simulative outcome was done by comparison to full-scale tests from the literature. This includes Wrap Around Distances and cyclist kinematics as well as the frontal shape parameters of the impacting vehicle. Further, the crashworthiness of the baby carrier was investigated. It was concluded that the belt system, which is attached to the baby carrier, was in several cases not able to secure the child in its position. In a result, the studied baby carrier showed poor performance as a passive safety device during the simulated accidents. In this respect, also possible injuries of the child’s head, brain and neck were discussed. Finally, the authors concluded that the kinematics of the impacted child buckled in a baby carrier are neither representing cyclist’s nor pedestrian’s kinematics.

Using GHBMC M50-O to assess the suitability of H-III and THOR for the SOI tests

The NHTSA frontal 90 kph 150 OMDB 35% offset test is a part of the new test protocol being proposed to simulate small overlap and oblique impact crashes in the field. An advanced crash test dummy, THOR, is proposed in the test protocol for injury risk assessment instead of the standard frontal impact dummy Hybrid III (H-III). An integrated vehicle finite element model with H-III, THOR and the GHBMC 50th male models is employed to compare the kinematics and injury differences. In this study, we evaluated the occupant response in the new frontal OMDB test using GHBMC models to quantify and qualify the potential injury pattern and risk in this type of crash. The vehicle model was validated with both a full frontal 35 mph rigid barrier test and the very first frontal OMDB test with the H-III 50th %ile male dummies is conducted. The differences in the measured responses of the H-III and THOR from simulations and tests, and the simulated responses of the GHBMC model, were compared. The additional tissue-level injuries predicted by the GMBMC model, which are beyond the capability of the H-III and THOR dummies, showed the potential injury pattern and risk of occupants in the OMDB test.

Methodological approach for reducing computational costs of vehicle frontal crashworthiness analysis by using simplified structural modelling

ABSTRACTA challenge in the design and optimisation of the vehicle front structures is the high computational costs required for crash analysis. A methodological approach to simplifying finite element vehicle models and crash barriers is presented in this paper. The methodology uses global deformation characteristics of structures which are obtained from the global crash model. For the simplification of the vehicle crash model, structural regions which sustain only elastic deformations during the frontal crash are replaced by kinematic numerical representations which describe both stiffness and load paths at the interface of the substituted structures. Verification studies of the simplified vehicle model show a very good agreement of the global and local structural response during the frontal crash. Further simplifications were applied to the offset deformable barrier by replacing its detailed crushing behaviour by kinematic descriptions. Through the combined use of both simplified numerical representations, the computational cost of a Euro new car assessment program (NCAP) offset crash analysis can be reduced by around 92%. With the obtained time reduction, structural optimisation studies of the remaining structure can be conducted efficiently for the identification of weight reduction potentials.

Comparison of response variation of THOR and Hybrid III dummy Models in a controlled rollover impact model

ABSTRACTSeveral dynamic rollover test procedures have been developed over the years; however, the repeatability of test results is often questioned. Also, there can be sensitivity of test and simulation results to small variations in the initial conditions. The objective of this study is to evaluate the response variation of three different crash dummy finite element (FE) models (two versions of a 50th percentile male Hybrid III (HIII) and a Test Device for Human Occupant Restraint (THOR) dummy) in a simulation of a controlled rollover test, using a late model vehicle FE model. A baseline model was established with each dummy, and then a global sensitivity analysis was performed for each dummy varying vehicle design and crash parameters. The simplified HIII dummy model was very sensitive to small variations in the initial conditions of the test. Both the THOR and detailed HIII models gave very consistent results presenting similar trends in the sensitivity analysis.

Design and Optimization of Engine Mount

Engine is consider as one of the main source in producing noise and vibration in vehicle. Engine mount is used between chasis and body to control engine vibration. The goal of the paper is introducing optimization method to find optimum value for engine mount specification based on random vibration method. Changing design parameters such as: location of engine mount, angle of instal, stiffness and damping coefficient of engine mount causes to change Natural frequency and vibration transmissibility ratio of system. For this purpose, full vehicle finite element model include chasis, body, suspension system, tires, seats, glosses and engine of typical van vehicle is provided and the effect of engine unbalances harmonic is applied on the model as a Power Spectral Density (PSD) form. Finally, driver seat PSD acceleration in three direction (longitudinal, lateral and vertical) is obtained. Design parameters (location, stiffness, damping coefficient of engine mount) change in specific range to find best system response. Final result shows that driver seat PSD acceleration can be considered as an optimum choice.

Design and structural analysis of unique structures under an internal vacuum

This paper details an experiment that was used to validate the frame deformation of three vacuums lighter than air vehicle finite element models composed of a frame with a skin covering. The experiment consisted of a simplified one directional loading to determine the behavior of a 3D printed frame, which was compared to a corresponding finite element model. A 3D printed icosahedron frame was loaded in compression using a mechanical testing machine to record the load versus displacement of the structure. It was discovered that the material properties of the printed structure were significantly lower than the quoted values from the manufacturer. The modulus property was extracted from the finite element model that best matched the experiment. The behavior of the frame from the experiment shows that the beams do buckle. The model matches the frame buckling and load retention. The feasibility of a vacuum lighter than air vehicle using an icosahedron, hexakis icosahedron, and celestial frame and skin were then analyzed since the method of analysis was proven through the experiment. The icosahedron showed failure due to material limits and the hexakis icosahedron showed definite feasibility using modern material properties.

Ride Dynamics of a Tracked Vehicle with a Finite Element Vehicle Model

<p>Research on tracked vehicle dynamics is by and large limited to multi-rigid body simulation. For realistic prediction of vehicle dynamics, it is better to model the vehicle as multi-flexible body. In this paper, tracked vehicle is modelled as a mass-spring system with sprung and unsprung masses of the physical tracked vehicle by Finite element method. Using the equivalent vehicle model, dynamic studies are carried out by imparting vertical displacement inputs to the road wheels. Ride characteristics of the vehicle are captured by modelling the road wheel arms as flexible elements using Finite element method. In this work, a typical tracked vehicle test terrain viz., Trapezoidal blocks terrain (APG terrain) is considered. Through the simulations, the effect of the road wheel arm flexibility is monitored. Result of the analysis of equivalent vehicle model with flexible road wheel arms, is compared with the equivalent vehicle model with rigid road wheel arms and also with the experimental results of physical tracked vehicle. Though there is no major difference in the vertical bounce response between the flexible model and the rigid model, but there is a visible difference in the roll condition. Result of the flexible vehicle model is also reasonably matches with the experimental result.</p><p><strong>Defence Science Journal, Vol. 66, No. 1, January 2016, pp. 19-25, DOI: http://dx.doi.org/10.14429/dsj.66.9201</strong></p>

Effects of translational and rotational accelerations on traumatic brain injury in a sport utility vehicle-to-pedestrian crash

A series of full-scale vehicle-to-pedestrian impact simulations were performed using a vehicle finite element (FE) model and a pedestrian FE model at 25 and 40 km/h. The pedestrian model collided laterally against the centre front (wrap-around) or front right corner (fender vault) of the vehicle considering a pedestrian's pre-impact transverse speed of 0.0-4.0 m/s. Analysis using selected injury assessment parameters revealed that both translational and rotational accelerations applied to the head were significantly related to the intracranial tissue deformation in the simulated impact cases; the cumulative strain damage measure (CSDM) (an injury metric representing a 'volume fraction' of the brain elements exceeding the tolerance level) resulted in 5.7% for primary and 39.4% for secondary head strikes on average (N = 12), implying that traumatic brain injury (TBI) can be closely associated with a combination of linear and rotational loadings exerted over the head during an eventual contact with the ground.