BACKGROUND
Crash simulations using finite element (FE) analysis are being used to design and help evaluate the safety performance of roadside safety hardware and features. Roadside safety crash simulations involve developing FE models of vehicles and roadside appurtenances and using these models to simulate the vehicles impacting the appurtenances. Use of simulation has progressed from modeling crash tests, to supporting hardware design decisions, and to providing guidance for roadside hardware placement. Effective use of simulation permits design optimization and minimizes the number of crash tests required to achieve acceptable impact performance, thus reducing both the development cost and installed cost of roadside hardware. Additionally, simulation provides a tool for assessing the performance limits of roadside hardware under conditions that cannot be readily tested with full-scale vehicles, such as sideways vehicle impacts and hardware installed on non-level terrain.
Historically, the safety performance of roadside safety hardware has been evaluated through full-scale vehicular crash testing. The testing process is typically iterative as design weaknesses and flaws are sequentially discovered and corrected. This type of physical experimentation is expensive and time consuming. Additionally, full-scale crash testing is often required to approve modifications to roadside safety devices that have already been fully crash tested. Crash simulation has the potential to be used for approval of design modifications. FHWA is beginning to consider acceptance of simulation in lieu of full-scale crash tests in approving some modifications to roadside safety systems.
However, there are no comprehensive and objective procedures for verification and validation of crash simulations. Verification and validation procedures have been developed for FE models in other disciplines (e.g., weapons systems, space crafts, and nuclear waste packaging). Sandia National Laboratories has developed a Phenomena Identification and Ranking Table. The American Institute of Aeronautics and Astronautics has published a Guide to Verification and Validation of Computational Fluid Dynamics Simulations (G-077-1998). The American Society of Mechanical Engineers has established a committee (PTC 60) on Verification and Validation in Computational Solid Mechanics. Although the verification and validation procedures mentioned above may be applicable to crash testing, there are many modeling issues that are unique to the roadside safety field.
Particularly relevant to this project are the ongoing activities of the recently established Computational Mechanics/Europe (CM/E) group. CM/E, which exists under the auspices of the European Committee for Standardization (CEN), is engaged in defining simulation reporting procedures, defining objective validation procedures, defining requirements for vehicle and barrier models, and defining analyst competency criteria.
OBJECTIVE
The objective of this research was to develop guidelines for verification and validation of detailed finite element analysis for crash simulations of roadside safety features. The focus of these guidelines are on establishing accuracy, credibility, and confidence in the results of crash test simulations intended (1) to support policy decisions and (2) to be used for approval of design modifications to roadside safety devices that were originally approved with full-scale crash testing.
Accomplishment of the project objective required the following tasks.
TASKS (1.) Conduct a literature review, including international sources, to obtain relevant information on verification and validation procedures that are being developed or have been used by other organizations. The contractor shall provide a review of the relevance of the documents cited in the "Background." (2.) Conduct interviews with practitioners and others in the field to obtain information on model verification and validation practices. (3.) Identify verification procedures, and the associated metrics, for FE model simulations for roadside safety applications. Define any uncertainties in the measured test data and simulation responses. (4.) Identify validation procedures, and the associated metrics, for FE model simulations for roadside safety applications. Define any uncertainties in the measured test data and simulation responses. (5.) Develop a proposed concept of the recommended verification and validation guidelines. Prepare an updated work plan for developing the guidelines. (6.) Submit an interim report that documents the findings from Tasks 1 through 5. (7.) Meet with the NCHRP panel to review the Task 6 interim report, approximately 1 month after its submittal. Submit a revised interim report and an updated work plan reflecting the panel's decisions. (8.) Execute the approved work plan and develop the guidelines. (9.) Apply the guidelines to a minimum of two selected crash simulations of roadside hardware designs. Revise the guidelines as appropriate. (10.) Meet with the NCHRP panel and up to 5 to 8 additional subject-area experts to review the guidelines developed in Task 8, approximately 1 month after their submittal. Modified guidelines resulting from review comments and discussions at the meeting shall be included in the preliminary draft final report. (11.) Develop recommendations for implementation for hardware modification acceptance, including a standardized report format for documenting the verification and validation of the model. (12.) Submit a final report documenting the entire research effort. The final report shall describe how the project was conducted and describe any needs for additional research and development work. It shall include appendixes documenting the verification and validation guidelines.
Status: The project is completed.
Product Availability: The final report has been posted on the TRB website as Web Document 179.
