Validation of DyMESH for Vehicle vs Barrier Collisions

A new three-dimensional collision simulation algorithm, called DyMESH (Dynamic MEchanical SHell) was recently introduced.[1]* This paper presents a validation of DyMESH for vehicle vs. barrier collisions. The derivation of the three-dimensional force vs. crush relationship was described previously.[1] Here the application of threedimensional force vs. crush curves using the outlined methodology is shown to be effective. Nonlinear force versus crush relationships are introduced for use in DyMESH. Included are numerous DyMESH collision simulations of several types of vehicles (e.g., light and heavy passenger car and sport utility) compared directly with experimental collision test results from various types of barrier tests (e.g., full frontal, angled frontal, and offset frontal). The focus here is not on the vehicle’s change in velocity, but on the acceleration vs. time history. The paper shows that, while not as important for simulating velocity change, a nonlinear or piecewise linear force vs. crush relationship can improve the prediction of the acceleration vs. time history which is critical for simulations in which occupant dynamics are to be studied. The capability of prescribing a non-linear forcedeflection curve within DyMESH is illustrated in each case studied. The studies show the effect on vehicle acceleration as the vehicle stiffness models are altered. The simulation results agree favorably with experimental data. INTRODUCTION Numerical simulation of complex physical events is becoming more commonplace as the cost of computing power drops with advances in technology. In addition to allowing faster run times using existing or “legacy” codes, many researchers are choosing to upgrade their codes and obtain higher fidelity results in run times that are similar to those achieved a few years ago. An important step in the process of developing or upgrading a code or algorithm is validation with test and/or theoretical results. The purpose of DyMESH (Dynamic MEchanical SHell) is to allow an interactive three-dimensional collision simulation of higher fidelity than has been available in the past. This paper presents simulation results using DyMESH. These results form part of the validation documentation. More validation results will be presented in the future. DyMESH uses the discretized surfaces of a vehicle to calculate its interaction with other objects (vehicles, barriers, light poles, etc.). Figure 1 shows the general flow of the DyMESH algorithm. An important extension of existing twodimensional methodology is used to generate a threedimensional force vs. deflection (or crush) relationship. This was discussed in a previous paper. [1] TESTS USED FOR COMPARISON Data from vehicle crash tests are readily available from sources such as the National Highway and Traffic Safety Administration (NHTSA), The George Washington University National Crash Analysis Center (NCAC), and the Insurance Institute for Highway Safety (IIHS). This paper contains simulations of documented full-scale tests using the DyMESH collision algorithm within the Human-Vehicle Environment (HVE) software.[7] The tests that are simulated with DyMESH are summarized in Table 1. These particular tests were selected because they vary in the size of the vehicle, the impact speed, and the impact orientation. The authors chose to present simulations resulting from first-time runs using input parameters that are intuitive and readily available. There has been no attempt to optimize the simulations to obtain more favorable agreement with *Numbers in brackets designate references found at the end of the paper. 1 test data. For example, stiffness coefficients available in the HVE vehicle database are used along with standard HVE vehicle-specific properties such as rotational inertias and suspension system properties.