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The forming effects along with strain rate, actual material properties and weld effects have been found to be very critical for accurate prediction of crash responses especially the prediction of local deformation. As a result, crash safety engineers started to consider these factors in crash models to improve the accuracy of CAE prediction and reduce prototype testing. The techniques needed to incorporate forming simulation results, including thickness change, residual stresses and strains, in crash models have been studied extensively and are well known in automotive CAE community. However, a challenge constantly faced by crash safety engineers is the availability of forming simulation results, which are usually supplied by groups conducting forming simulations. The forming simulation results can be obtained by either using incremental codes with actual stamping processes or one-step codes with final product information as a simplified approach.

There are a wide variety of approaches to model the automotive seat and occupant interaction. This paper traces the studies conducted for simulating the occupant to seat interaction in frontal and/or rear crash events. Starting with an initial MADYMO model, a MADYMO-LS/DYNA coupled model was developed. Subsequently, a full Finite Element Analysis model using LS/DYNA was studied. The main objective of the studies was to improve the accuracy and efficiency of CAE models for predicting the dummy kinematics and structural deformations at the restraint attachment locations in laboratory tests. The occupant and seat interaction was identified as one of the important factors that needed to be accurately simulated. Quasi-static and dynamic component tests were conducted to obtain the foam properties that were input into the model. Foam specimens and the test setup are discussed. Different material models in LS/DYNA were evaluated for simulating automotive seat foam.

To improve the energy absorption capacity of front-end structures during a vehicle crash, a novel 12-sided cross-section was developed and tested. Computer-aided engineering (CAE) studies showed superior axial crash performance of the 12-sided component over more conventional cross-sections. When produced from advanced high strength steels (AHSS), the 12-sided cross-section offers opportunities for significant mass-savings for crash energy absorbing components such as front or rear rails and crush tips. In this study, physical crash tests and CAE modeling were conducted on tapered 12-sided samples fabricated from AHSS. The effects of crash trigger holes, different steel grades and bake hardening on crash behavior were examined. Crash sensitivity was also studied by using two different part fabrication methods and two crash test methods. The 12-sided components showed regular folding mode and excellent energy absorption capacity in axial crash tests.

To evaluate vehicle crash performance in the early design stages, a reliable fracture model is needed in crash simulations to predict material fracture initiation and propagation. In this paper, a generalized incremental stress state dependent damage model (GISSMO) in LS-DYNA® was calibrated and validated for a 780-MPa third generation advanced high strength steels (AHSS), namely 780 XG3TM steel that combines high strength and ductility. The fracture locus of the 780 XG3TM steel was experimentally characterized under various stress states including uniaxial tension, shear, plane strain and equi-biaxial stretch conditions. A process to calibrate the parameters in the GISSMO model was developed and successfully applied to the 780 XG3TM steel using the fracture test data for these stress states.

The modeling of plastic fuel tank systems for crash safety applications has been very challenging. The major challenges include the prediction of fuel sloshing in high speed impact conditions, the modeling of multilayer thermoplastic fuel tanks with post-forming (non-uniform) material properties, and the modeling of tank straps with pre-tensions. Extensive studies can be found in the literature to improve the prediction of fuel sloshing. However, little research had been conducted to model the post-forming fuel tank and to address the tension between the fuel tank and the tank straps for crash safety simulations. Hoping to help improve the modeling of fuel systems, the authors made the first attempt to tackle these major challenges all at once in this study by dividing the modeling of the fuel tank into eight stages. An ALE (Arbitrary Lagrangian-Eulerian) method was adopted to simulate the interaction between the fuel and the tank.

Strain rate effects have been identified as one of the most critical factors for the modeling of vehicle components in many previous investigations. The strain rate data available to the authors have been processed to obtain the input decks of a required material law in prior investigations. With the application of strain rate modeling, the strain rate database needs to be expanded. In order to continuously improve the safety CAE quality and efficiency, especially the prediction of a vehicle's pulse in a crash event, the effort has been made to include more strain rate data and extend the material database for safety CAE applications. In this study, strain rate data provided by Ispat Inland Inc. for AISI/DOE Technology Roadmap Program are processed. The material processed in this study include HSS590-CR, 440W-GA, BH300-GI, HSLA350-GI, DP600-HR, TRIP590-EG, TRIP600-CR, TRIP780-CR.

The objective of this study is to verify the performance of a target vehicle model in vehicle-to-vehicle impact applications. In some vehicle-to-vehicle tests, the target vehicle stays the same and the bullet vehicle changes from test to test depending on the programs under evaluation. To obtain reasonable crash pulse predictions in vehicle-to-vehicle impacts, it was decided to develop an accurate and robust target vehicle model first. The development of the target vehicle model was divided into two phases, rigid barrier and vehicle-to-vehicle impacts. Twelve rigid barrier tests, including full rigid barriers, angular rigid barriers, offset rigid barriers, and fixed rigid poles were adopted in the first phase of the study to calibrate the target vehicle model. The results of the study have been reported [1]. This paper focuses on the verification of vehicle-to-vehicle impacts.

An accurate and robust target vehicle model was developed for vehicle compatibility applications. Although vehicle compatibility simulation involves a bullet vehicle hitting a target vehicle, the focus of this paper is to develop a target vehicle model. To ensure the robustness, the target vehicle model needs to provide reasonable responses under different impact conditions. This can be achieved by calibrating the model against different physical tests. Significant effort was taken to improve the accuracy of the target vehicle model. In the calibration process, some components were found to have significant effects on the global responses. These components play different roles in different crash modes. To improve the overall correlation with test, different component tests were also designed and conducted to understand the characteristics and improve the modeling of these critical components.

The objective of this study is to develop a target vehicle model for vehicle-to-vehicle impact applications. In order to provide reasonable predictions for crash pulses in vehicle-to-vehicle impacts, an accurate and robust target vehicle model was developed first. An ideal target vehicle model should be able to provide reasonable results when hit by different bullet vehicles at different impact speeds and under different impact conditions. This was achieved by calibrating the target vehicle model against different vehicle crash tests, which include full rigid barriers, angular rigid barriers, offset rigid barriers, and fixed rigid poles. Twelve rigid barrier tests were adopted in this study to calibrate the target vehicle model. During the calibration process, some of the vehicle structures were examined and remodeled carefully for their properties and mesh quality.

This study is a systematic investigation of the body mounts' dynamic characteristics in component, sub-system and full system levels and its application in the frontal impact analysis of a body-on-frame (BOF) vehicle. Concluded from the component study, the body mount is modeled by non-linear spring with built-in damage and rupture properties. The sub-system study reveals the importance of modeling the interaction between the body mount and its surrounding structure. A general-purpose interaction modeling is developed to provide a realistic CAE simulation of this interaction behavior. The full system is mainly for methodology validation. Four 90-degree frontal and the one IIHS offset frontal crash tests are used to evaluate the performance of the body mount in low and high speeds and its capability of predicting the body mount and the floor pan failures.

This study summarizes the latest development of the methodologies for testing and CAE modeling of the engine mount. A systematic approach is used in this study with detailed component, subsystem and full system level investigations. The component level study reveals the entangling phenomenon of the inertial and rate effects in the engine mount dynamic characteristics. In the subsystem, the interaction between the engine mount and its surrounding structure is explored. The full system study is primarily used to validate the CAE methodology for engine mounts developed in the component and subsystem level studies. Four full vehicle barrier crash tests, with different crash modes and speeds, are employed in this validation phase to evaluate the performance of the engine mount CAE methodology.

The frontal rail is one of the most important components of a vehicle in determining crash performance, especially for a body on frame vehicle. Prior research [1] has shown that the frontal rail absorbs a significant amount of impact energy in a crash condition. In order to optimize crash performance, a component level sensitivity study was conducted to determine the effect different types of triggers would have on the performance of the frontal rail. The objective of this study is to determine the sensitivity of trigger size, trigger shape, and trigger orientation as well as to improve corresponding trigger modeling methodology by comparing crushed components to crushed CAE models. In this sensitivity study, the location of the triggers was held fixed, while the size, shape, and orientation were varied. The metric that will be used to compare the performance of these different trigger shapes is the overall stiffness of the frontal rail.

For a body-on-frame (BOF) vehicle, the frame is the major structural subsystem to absorb the impact energy in a frontal vehicle impact. It is also a major contributor to energy absorption in rear impact events as well. Thus, the accuracy of the finite element frame model has significant influence on the quality of the BOF vehicle impact predictability. This study presents the latest development of the frame modeling methodology on the simulation of BOF vehicle impact performance. The development is divided into subsystem (frame sled test) and full system (full vehicle test). This paper presents the first phase, subsystem testing and modeling, of the frame modeling development. Based on the major deformation modes in frontal impact, the frame is cut into several sections and put on the sled to conduct various tests. The success of the sled test highly depends on whether the sled results can replicate the deformation modes in the full vehicle.

This study focuses on the modeling of a frame in a body-on-frame (BOF) vehicle to improve the prediction of vehicle response in crashes. The study is divided into three phases - component (frame material modeling), subsystem (frame sled test) and full system (full vehicle test). In the component level, we investigate the available strain rate data, the performance of various material models in crash codes and the effect of the strain rate in crash simulation. In the subsystem phase, we incorporate the strain rate modeling and expand the scope to include both the forming and the welding effects in the subsystem CAE model to improve the correlation between CAE and test. Finally the improved frame modeling methodology with strain rate, forming and welding effects is adopted in full vehicle model. It is found that the proposed frame modeling methodology is crucial to improve the pulse prediction of a full vehicle in crashes.

Statistic shows the majority of real world frontal collisions involve only partial overlap of the vehicle front end. Thus the European Experimental Vehicle Committee (EEVC) has established a safety standard and test procedure utilizing a deformable barrier for offset impacts. The offset deformable barrier (ODB) is designed to represent the characteristics of a vehicle front end. Therefore, it can replace a target vehicle and the offset test can be conducted economically. Many component, sub-assembly and full vehicle system tests have been conducted in Ford using the EEVC ODB. Based on the various tests, the barrier responds differently depending on the front end design and the size of an impacting vehicle. Sometimes the front end of a test vehicle punches through the barrier. Also rupture of aluminum sheets and tearing of honeycomb materials are often observed in post-test barriers.

Advanced High Strength Steels (AHSS) have been implemented in the automotive industry to balance the requirements for vehicle crash safety, emissions, and fuel economy. With lower ductility compared to conventional steels, the fracture behavior of AHSS components has to be considered in vehicle crash simulations to achieve a reliable crashworthiness prediction. Without considering the fracture behavior, component fracture cannot be predicted and subsequently the crash energy absorbed by the fractured component can be over-estimated. In full vehicle simulations, failure to predict component fracture sometimes leads to less predicted intrusion. In this paper, the feasibility of using computer simulations in predicting fracture during crash deformation is studied.

The dynamic response of a front lower control arm (LCA) is very important in crash safety. In the event of a crash, the deformation of the LCA affects the frame rail's ability to crush and absorb energy on impact. Therefore, the deformation and rupture of the LCA during a crash may indirectly influence the deceleration pulse which is needed for safety sensor calibration of airbag deployment [1]. Depending on compliance, bushings have a significant effect on the deformation and rupture of the LCA. During a high speed impact test, the bushings allow the LCA to rotate at the joints or points where the LCA connects to the frame. The development of new LCA and bushing designs, constructed of different materials and geometries, require a standard test to measure their performance. The overall goal of this study was to develop a standardized procedure to test the stiffness, deformation, and strength of LCA bushings.

The conversion between cast aluminum lower control arms (LCAs) and stamped steel LCAs has prompted the need for new LCA designs to achieve parallel levels of performance. Component tests procedures and CAE modeling methodologies need to be utilized to assess future LCA designs across a variety of vehicle lines to meet or exceed performance criteria. Therefore the overall goal of this study was to develop a standardized test procedure to test the stiffness, deformation and strength of LCAs. In addition, CAE modeling methodologies to better model LCAs will be developed. The test procedures and CAE modeling methodologies would then be used to set performance targets for future LCA designs. To standardize the LCA test procedure, component test fixtures were developed in this work. The objective of the fixtures is to test LCAs with similar boundary conditions they would experience in vehicle crash. Three different test modes are examined in this project.

Explicit method is commonly used in crashworthiness analysis due to its capability to solve highly non-linear problems without numerous iterations and convergence problems. However, the time step for explicit methods is limited by the time that the physical wave crosses the element. Therefore, to avoid large amount of CPU time, the explicit method is usually used for non-linear dynamic problems with a short period of simulation duration. For problems under quasi-static loading conditions at pre-crash and post-crash, implicit method could be more efficient than explicit methods because the required computation time is much shorter. Due to the recent advance of crash codes, which allows both implicit and explicit computations to be performed in the same code, crash engineers are able to use explicit computation for crash simulation as well as implicit computation for some of the pre-crash quasi-static loading or post-crash spring back simulations.

Vehicle pitch and drop has become an important subject to crash analysis due to the recent FMVSS208 requirements for unbelted occupant. During frontal impact, the excessive header drop due to significant vehicle pitch and drop can induce the contact between occupant's head and sun visor. To avoid this issue, structure design for reducing vehicle pitch and drop is essential to crash safety. Historically, CAE simulation has been used in structure design during vehicle development process. Therefore, the quality of CAE modeling for replicating vehicle pitch and drop at physical test is crucial for assisting the structure design. In this paper, the most effective components in CAE model to vehicle pitch and drop have been identified and ranked by using the results of the sensitivity study. Hence the model quality can be emphasized on those major components including front horn, kick-down of front frame, body structure at upper load path, and body mounts.