Recommended Test Vehicle Update for Manual for Assessing Safety Hardware

Passenger vehicles in Manual for Assessing Safety Hardware (MASH) crash testing are required to be representative of the modern vehicle fleet and practical worst-case impact scenarios. The objective of this paper was to identify potential updates for standard test vehicle selection criteria for MASH as well as develop a preferred strategy for performing future standard test vehicle reviews. Representative vehicles were documented using sales data, and registration and crash data were observed to validate the primary use of sales data. Curb weights were plotted against cumulative market share of new vehicle sales to identify the 5th and 95th percentile “practical worst-case” weights of 2,800 lb and 5,850 lb, respectively, consistent with MASH philosophy. Suitable test vehicle options were found at the 5th percentile weight; however, a pickup near the 92.5 percentile weight (5,400 lb) was recommended to ensure vehicles are both representative of the fleet and obtainable for crash sites. MASH test vehicle specifications were recommended based on a review of geometrical and inertial properties of candidate vehicles near these target weights. Potential mid-size test vehicles were also explored, and four vehicle classes (two mid-size car and two crossover utility vehicle [CUV] classes) were identified as test vehicle candidates. Research on vehicle impact behavior of mid-size cars and CUVs are desired to determine impact behavior of each vehicle with different roadside hardware. Future revisions to MASH test vehicle selection criteria were outlined and should use analysis and attributes of new vehicle sales.

Enhancement of Vehicle/Roadside Hardware Crash: Dynamic Response of Child Occupant Involved in Vehicle/Pole Impact

This paper focuses on minimizing child injuries experienced during frontal vehicle-to-pole collisions by improving on the safety and energy absorption of existing traffic pole structures. A finite element computer model, using LS-DYNA software, is used to simulate crash events in order to determine the influence of pole structural and material characteristics on the injury parameters of a hybrid III 3-year-old child dummy occupant. Different pole support systems and laminar traffic poles of different materials are investigated in this paper. It is concluded that the anchored base support and the embedded pole in soil systems provide desirable crashworthy results, thus reducing fatalities and injuries resulting from vehicle impact. It is also recommended to mandate traffic protection devices in all areas with poor energy absorbing characteristics that resemble non-deformable objects.

Component and Full Scale Tests for Suspension Model Validation

The National Crash Analysis Center (NCAC) at the George Washington University (GWU) has been developing and maintaining a public domain library of LS-DYNA finite element (FE) vehicle models for use in transportation safety research. The recent addition to the FE model library is the 2007 Chevrolet Silverado FE model. This FE model will be extensively used in roadside hardware safety research. The representation of the suspension components and its response in oblique impacts into roadside hardware are critical factors influencing the predictive capability of the FE model. To improve the FE model fidelity and applicability to the roadside hardware impact scenarios it is important to validate and verify the model to multitude of component and full scale tests. This paper provides detailed description of the various component and full scale tests that were performed, specifically, to validate the suspension model of the 2007 Chevrolet Silverado FE model.

Modeling Tire Blow-Out in Roadside Hardware Simulations Using LS-DYNA

Often when vehicles interact with roadside hardware like guardrails, bridge rails and curbs, the interaction between the roadside hardware and the tire causes the tire to lose its air seal and “blow-out”. Once the seal between the rim and rubber tire is lost, the tire deflates. The behavior of the deflated tire is much different than the behavior of an inflated tire such that when this behavior is observed in real world crashes or in full-scale crash tests, the vehicle kinematics are strongly coupled to the behavior of the deflated tire. Accounting for this behavior in LS-DYNA models is crucial in many types of roadside hardware simulations since the forces generated by the deflated tire often introduce instability into the vehicle that can cause rollover or spinout. This paper will present a method for accounting for tire deflation during LS-DYNA simulations and will present examples of the use of this type of improved model.

Improved Truck Model for Roadside Safety Simulations: Part I—Structural Modeling

Computer simulation is now a mainstream tool for design and analysis of roadside hardware. For the past several years, researchers at the National Crash Analysis Center, Worcester Polytechnic Institute, and the University of Nebraska–Lincoln have been improving various features of a 2000-kg pickup truck model, the most widely used vehicle model for roadside safety simulation. Many modeling techniques have been learned, and an improved model has been developed that should aid analysts at other locations who are performing similar simulations. The various effects and difficulties of “reducing” a finite element model to decrease computational costs are examined, including the elimination of initial penetrations, free-edge tangling, snagging, and “shooting nodes.” The elective refinement of mesh density, the elimination of manipulated material densities to achieve desired masses, the improvement of connections between components, and the inclusion of all significant parts to improve accuracy are analyzed. The significance of not oversimplifying critical components is emphasized, as well as the importance of realistic model behavior. Evolutionary changes to vehicle models are required as more information is obtained about modeling and truck behavior in roadside safety applications. Different research groups will have different modeling approaches, but by sharing the details of those approaches and by sharing models, the collective capabilities in roadside safety simulation will improve, ultimately resulting in better roadside hardware. The models described are thought to be a tremendous improvement over previous-generation models of the reduced pickup truck.

Improved Truck Model for Roadside Safety Simulations: Part II—Suspension Modeling

The 2000-kg pickup truck is a very important vehicle in roadside safety research because it is specified in many of the tests in NCHRP Report 350. The characteristics of the pickup truck make it a very demanding crash test vehicle. Because the 2000-kg pickup truck is an important crash test vehicle, it was the very first vehicle chosen for development of a finite element model. The nonlinear finite element program LS-DYNA has become an important feature of roadside hardware design and analysis in recent years, and much of the success of these modeling efforts is partly caused by the availability of a good 2000-kg pickup truck model. Like all models, the model has evolved over the past decade. New features and improvements have been added continuously to the model by many different teams to solve specific analysis problems. One particular area where there has been a great deal of activity is in the area of modeling the suspension properties of the vehicle. Suspension response is particularly important for 2000-kg pickup truck impacts because the vehicle often experiences stability problems in impacts with roadside hardware. A number of improvements and modifications to Version 9 of the NCAC 2000-kg pickup truck model are summarized. These improvements involved changing the finite element model, changing element properties, and obtaining suspension response properties from physical tests. The 2000-kg truck model was then validated against a series of low-speed, live-drive tests with an instrumented pickup truck. The improved model provides more realistic vehicle suspension response than earlier models and should prove to be a valuable addition to future finite element modeling activities.