Ali O. Atahan

Finite Element Simulation of a Strong-Post W-Beam Guardrail System

Computer simulation of vehicle collisions has improved significantly over the past decade. With advances in computer technology, nonlinear finite element codes, and material models, full-scale simulation of such complex dynamic interactions is becoming ever more possible. In this study, an explicit three-dimensional nonlinear finite element code, LS-DYNA, is used to demonstrate the capabilities of computer simulations to supplement full-scale crash testing. After a failed crash test on a strong-post guardrail system, LS-DYNA is used to simulate the system, determine the potential problems with the design, and develop an improved system that has the potential to satisfy current crash test requirements. After accurately simulating the response behavior of the full-scale crash test, a second simulation study is performed on the system with improved details. Simulation results indicate that the system performs much better compared to the original design.

Crashworthiness evaluation of an intercity coach against rollover accidents

Rollover accidents can result in serious consequences to vehicle occupants if necessary safety measures are not taken. Two significant measures that can be implemented to minimise occupant injury risk during vehicular rollover events are structural adequacy of the vehicle against crushing and occupant protection by using passive protective devices, such as safety belts and air bags. The aim of this study is to evaluate the structural resistance and passenger injury risks and compare the effectiveness of safety belt usage during a simulated rollover event. In this study, a 13 m long TEMSA bus was used as the vehicle. A total of eight occupants were placed in the critical places of the bus by considering the structurally weakest sections. Three different occupant protection cases were considered: (i) no safety belt; (ii) two-point safety belt and (iii) three-point safety belt. A standard rollover procedure was simulated using non-linear finite element code LS-DYNA. Head and neck injury criteria were used for all three cases to evaluate the effectiveness of seat belt usage on occupant protection. Simulation results clearly illustrated that if occupants had no seat belt protection they suffered serious risk of injuries. Moreover, two- and three-point safety belts provided somewhat similar protection levels for most of the occupants. On the basis of findings, use of two-point safety belts in all the seats of the TEMSA buses was recommended because of their ease of handling.

Crash test simulation of a modified thrie-beam high containment level guardrail under NCHRP Report 350 TL 4-12 conditions

This paper describes details of a computer simulation study performed on a modified thrie-beam high containment level guardrail designated as SGR09b. Because the SGR09b guardrail system is the only high containment guardrail system passing the NCHRP Report 350 TL4 requirements in its class, developing an accurate finite element model for this guardrail is deemed to be a significant contribution towards enhancement of computer-simulated virtual roadside safety research. For this reason, a detailed finite element model of the SGR09b guardrail system has been developed and subjected to 8000 kg single unit truck impact under NCHRP Report TL4 conditions. The fidelity of the simulation study was evaluated using the full-scale crash test results. As in the full-scale crash test, in the finite element simulation study, the guardrail system successfully contained and redirected the 8000 kg single unit truck. Based on the crash test results, it was determined that the finite element models for both the SGR09b guardrail system and the 8000 kg single unit truck are fairly accurate and can be used with confidence in further computer-simulated virtual roadside safety research.

Vehicle Crash Test Simulation of Roadside Hardware Using LS-DYNA: A Literature Review

A great deal of progress has been achieved during the past several years in integrating advanced non-linear finite element programs into the design and analysis phases of roadside hardware. Most of the progress in this area can be attributed to the pioneering work by Lawrence Livermore National Laboratory (LLNL) along with extensive financial support by the Federal Highway Administration (FHWA) and other institutions. There is still, however, much work remaining before analytical methods achieve their full potential in roadside safety research. The computer software tools are available and computing capabilities continue to improve at a rapid pace making analysis of complex systems possible. The application of Finite Element Analysis (FEA) has evolved from relatively simple impacts to highly realistic interaction problems. With continued progress, FEA is expected to play a vital role in the design and analysis of new generation cost-effective roadside hardware in coming years. This literature review attempts to summarise the major achievements and key developments on crash test simulation of roadside hardware over the past years and inform readers about the current state of knowledge in roadside hardware simulation. Successful crash test simulations on different applications are reviewed based on roadside hardware type. Specific models used in the virtual crash tests are explained. Due to the nature of the paper, many of the details that go into the successful simulations are not discussed herein. References for those details previously discussed in the literature are provided.

Development of a 30,000 kg heavy goods vehicle for LS-DYNA applications

In this paper, a finite element model of a 30,000 kg Heavy Goods Vehicle (HGV) was developed and validated against full-scale crash test data. Since this vehicle is a standard test vehicle in the European crash test standards, EN1317, development of an accurate vehicle model was deemed to be a positive contribution to the evaluation of roadside safety hardware. The vehicle model reproduces a FIAT-IVECO F180 truck, a vehicle with four axles and a mass of 30,000 kg when fully loaded. The model consisted of 12,337 elements and 11,470 nodes and was built for and is ready to use with LS-DYNA finite element code from Livermore Software Technology Corporation. Data available from two previously performed full-scale crash tests, one on a steel bridge rail and the other on a portable concrete barrier, were used to validate the accuracy of the HGV model. Results of the finite element simulation study show that the developed HGV model shows promise and can accurately replicate the behaviour of an actual HGV in a full-scale crash test. Improvements such as the steering mechanism in the front axles and the suspension system are currently underway to make the model more realistic.

Design Methodology of Heavy Truck Front Underride Protection Devices (FUPD)

The Objective of this study is to explain a new methodology in the design of heavy vehicle front underride protection devices (FUPD). This methodology is targeted generating optimal solutions in a cost-effective manner. In this research project non-linear finite element models were created using LS DYNA FEA package to perform crash simulations between a small car and the front of the truck at various levels, starting from component model level and ending with full tractor-semitrailer model level. Comparison between the crash simulation results with and without FUPD cases was performed to assess the adequacy of the design at every level of the study. Based on the results obtained an efficient and confident methodology for the evaluation of heavy truck FUPD designs is proposed. Furthermore, the proposed evaluation criteria are recommended to be the pioneering standard for FUPD performance evaluation.© 2010 ASME

Design and Validation of a 30,000 kg Heavy Goods Vehicle Using LS-DYNA

Extraordinary developments in virtual crash testing research have been achieved during the past decade. Advancements in hardware and software technology along with improvements in computation mechanics and increased number of full-scale crash tests contributed positively to the development of more realistic finite element models. Use of complex finite element codes based on computational mechanics principles allowed the virtual reproduction of real world problems. Regarding roadside safety, the design phase was, until now, based on the use of simplified analysis, unable to describe accurately the complexity of vehicle impacts against safety hardware. Modeling details, such as geometry, constitutive laws of the materials, rigid, kinematic and other links between bodies, definition and characterization of contact surfaces are necessary to build an accurate finite element model for an impact problem. This set of information is needed for each different body involved in the event; making the development of a complete model very much demanding. Once a part (subset) of the entire model has been accurately validated against real experimental data, it can be used again and again in other analogous models. In this paper, finite element model of a unique Heavy Goods Vehicle (HGV) was developed and partially validated using actual crash test data. Development of this particular vehicle model was important since this vehicle is extensively used in Europe to test the structural adequacy of high containment level (H4a) safety barriers according to EN 1317 standard. The HGV model studied reproduces a FIAT-IVECO F180 truck, a vehicle with 4 axles and a mass of 30,000 kg when fully loaded. The model consisted of 12,337 elements and 11,470 nodes and was built for and is ready to use with LS-DYNA finite element code from Livermore Software Technology Corporation. Results of the validation study suggest that the developed HGV model shows promise and can be used in further studies with confidence. Improvements such as, steering mechanism in front axes and suspension system is currently underway to make model more realistic.Copyright

Design and simulation of an energy absorbing underride guard for heavy vehicle rear-end impacts

Recent passenger car-heavy vehicle rear-end crashes demonstrate the importance of rear underride guard designs for heavy vehicle applications. Currently specified rear underride guards have many shortcomings, such as structural strength and energy dissipation capacity, clearance from ground, and other design aspects. As a result of these inadequacies in underride-guard design, many lives are lost every year when passenger cars slide underneath heavier vehicles. In this study, design modifications to an underride guard that minimally complies with the requirements contained in FMVSS 223/224 are evaluated. A previously performed crash test on the guard using a compact passenger car demonstrated the potential for excessive vehicle underride and passenger compartment intrusion problems. After the full-scale crash test, a detailed finite-element study is performed to investigate the shortcomings of the design. The accuracy of the underride guard model is partially validated using both a quasi-static and a full-scale crash test. After the validation, the guard is modified to improve its structural behaviour and energy-dissipation capacity. Four crash-test simulations are performed on the modified guard model to verify its effectiveness in energy dissipation and preventing intrusion into the passenger compartment. In these simulations, two vehicle speeds of 48 km/h and 56 km/h and two impact positions of 0% and 50% offsets are used to fully verify the acceptability of the modified guard model. Simulation results show that the modified rear underride guard performs much better than the original design. The guard dissipated a significant amount of the impacting vehicles energy and showed no potential for passenger-compartment intrusion in any simulation. The deceleration of the vehicle was also within acceptable limits. Based on these results, it can be concluded that the improved guard performed well and the implementation of this particular underride guard on heavy vehicles looks promising.

A Rear-End Protection Device for Heavy Vehicles

Rear underride crashes, particularly with heavy vehicles, constitute a serious safety concern for passenger cars. Several solutions to this emerging concern have been proposed by responsible agencies. Recent rear-end crashes with heavy vehicles show that a properly used rear underride guard devices can slow down impacting vehicle in a controlled manner. Moreover, with the use of these devices, the severity of crashes can be reduced and loss of lives can be prevented. In this paper, a special underride guard device is designed for heavy vehicle use. The height of the device from ground and support conditions are varied to evaluate and compare the crash performances. Finite element models of these particular designs are constructed and models are impacted by a passenger car model traveling at two different speeds of 48 km/h and 64 km/h. LS-DYNA, a non-linear finite element code capable of analyzing large deformations is used for the analysis. Vehicle decelerations, energy dissipations and passenger car crush characteristics are compared to determine the acceptability of each design. Based on the simulation study, an optimum height from ground and support condition are determined for acceptable impact performance for heavy vehicle mounted rear -end underride guard devices against passenger vehicle impacts.Copyright

Truck front underride development: literature survey

The objective of this literature survey is to review and report related information on Front Underride Protection Devices (FUPDs) based on previously conducted studies, test reports and existing regulations. An attempt has been made to review and collate the findings from worldwide studies examining frontal underride crashes involving heavy- and light-class vehicles. Moreover, a literature review was performed to identify any relevant findings and developments subsequent to these studies including any existing or proposed design standards for FUPDs.