DESIGN IMPROVEMENT IN FRONT BUMPER OF A PASSENGER CAR USING IMPACT ANALYSIS”-A REVIEW

Car accidents are happening every day. We must take into account the statistics – ten thousand dead and hundreds of thousands to million wounded each year. These numbers call for the necessity to improve the safety of automobiles during accidents. Automotive bumper system is one of the key systems in passenger cars which helps to protect the vehicle during impacts. The following paper deals with the design improvements in the front bumper of passenger cars in India, using impact analysis. The modification will be made considering size, shape and material

Optimization of the axial crushing behavior of closed-cell aluminum foam filled welded 1050 al square-cross section crashboxes

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2009Includes bibliographical references (leaves: 194-209)Text in English; abstract: Turkish and Englishxx, 211 leavesThe crushing behavior of partially Al closed-cell foam (Alulight AlSi10) filled 1050H14 Al crash boxes was investigated at quasi-static and dynamic deformation velocities. The quasi-static crushing of empty and filled boxes was further simulated using LS-DYNA. Finally, the crushing of partially foam filled 1050H14 crash boxes was optimized using the response surface methodology. The used optimization methodology was also applied to the boxes made of a stronger Al alloy, 6061T4 Al, and filled with a higher strength Al foam, Hydro Al closed cell foam, in order to clarify the effect of box material and foam filler strength on the crushing behavior of the filled boxes. Within the investigated tube thickness and foam relative density range, the energy absorption of 1050H14 boxes was optimized at 3 mm wall thickness and 0.1114 (Alulight) and 0.0508 (Hydro foam) foam filler relative density. The increase in specific energy absorption of 1050H14 crash box was 5.6% with Alulight and 21.9% for Hydro foam filling. The SEA values of empty, partially and fully foam filled boxes were predicted as function of box wall thickness between 1 and 3 mm and foam filler relative density between 0 and 0.2, using the analytical equations developed for the mean crushing loads. The analysis indicated that both fully and partially foam filled boxes were energetically more efficient than empty boxes above a critical foam filler relative density. Partial foam filling however decreased the critical foam filler density at increasing box wall thicknesses

Study of a simplified bumper system subjected to offset impact loading

Includes abstract.Includes bibliographical references.This thesis reports on the behaviour of a simplified bumper system, with regards to energy absorbing characteristics. The simplified bumper system comprises of three components, the crossbeam and two longitudinal members. In the study, several parameters are altered to investigate the change in behaviour of the individual components as well as the bumper system. These parameters of the bumper system include: Wall-thickness of the crossbeam (1.0mm to 4.0mm in increments of 0.5mm), Two profiles of a crossbeam (straight and curved), Two longitudinal member profiles (straight and tapered). Experiments are carried out to study the behaviour of the bumper system subjected a 40% offset impact loading condition

Crash Safety Assurances Strategies for Future Plastic and Composite Intensive Vehicles (PCIVs)

This report addresses outstanding safety issues and research needs for Plastics and Composite Intensive Vehicles (PCIVs) to facilitate their safe deployment by 2020. PCIVs have the potential to revolutionize the automotive sector; however, the use of plastics and composite materials in automotive structures requires an in-depth knowledge of their unique performance characteristics in the crash and safety environment. Included in this report is a proposed definition of the PCIV, a review of potential safety benefits, lessons-learned, and progress to date towards crashworthiness of PCIVs as well as proposed safety performance specifications and research needs

An Investigation on Spot-Weld Modeling Complexity for Crash Simulation

In order to design car body structures which are safe during crash, modern automotive manufacturers perform both full-scale experimental crash tests and computer simulation of vehicle crash events using commercially available Finite Element Analysis (FEA) packages such as ABAQUS or LS-DYNA. Use of crash simulations significantly reduces the number of real time crash experiments needed and reduces the time required for design changes. However, in order to capture accurately crash behavior during high-speed impact, a large amount of detailed FEA modeling features such as number and types of elements, mesh element size, number of components, different types of connectors, material properties, and other detailed features are needed. Crash simulation requires explicit time-stepping procedures, which can be computationally expensive for complicated full vehicle models with many components. An important feature in crash simulation is the amount of detail included in modeling spot weld connections. Traditionally for efficiency, simple node-to-node rigid connections for modeling spot weld connections between different components are used, especially when many components are connected in a full vehicle crash model. Recent studies have shown the importance of accurate modeling including elastic stiffness and failure modes for spot welds due to high impact loads in automotive crash analysis. For efficiency and convenience, most commercially available FEA packages now include the option of creating mesh independent spot welds, which allow the user to define the location of the center point of the spot weld and define the spot weld radius on adjacent surfaces of connected components. A distributed coupling to nodes within the radius specified is automatically created which approximates the behavior of a spot weld of finite size. In addition, the size of the rigid spot weld model provides greater accuracy compared to the simple node-to-node connection. However, it has not been until very recent that some researchers and commercially available FEA software have the ability to include important spot weld elastic properties and failure modes combining pull, peal, shear, and torsion. In this work, different levels of complexity in spot weld modeling are examined in terms of sufficient accuracy which can be used efficiently for impact analysis of large connected components and full vehicle crash models. In order of increasing complexity, the following spot weld models are considered and results compared: (a) simple node-to-node rigid connection, (b) rigid mesh independent spot welds, (c) elastic mesh independent spot welds, and (d) elastic with failure mesh independent spot welds. In order to study the fundamental behavior of the different mesh-independent spot weld models, pullout and peal tests between two thin ductile steel plates are performed which isolate different failure modes. Comparisons of reaction force versus displacement curves and internal energy versus displacement for all the different spot weld models are given. Results indicate that the rigid connected results in peak reaction forces which are much larger than elastic spot welds. The spot weld model, which includes failure, follows the same path as the elastic weld but when reaching the particular failure force the reaction remains constant with additional applied displacement. To better understand the behavior of the spot-weld models for crash analysis on a realistic and important automotive component which exhibits complex crushing modes with combined axial and bending a frontal longitudinal rail designed for strength and energy absorption was studied with a node-to-node rigid spot weld compared with mesh independent rigid and elastic spot weld connections. The frontal longitudinal rail is a thin walled closed section located in between the front bumper and the firewall manufactured from two stamped sheets with spot welds on both sides of flanges at discrete intervals along the length. In addition to spot welds, the effect of various shape and size parameter changes including waves, beads, and a small rib for crush initiation that significantly increase energy absorption and crush force efficiency for the rail component are proposed

Early phase of the cross car beam concept development

Tese de Mestrado Integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 201

Analysis of a car door subjected to side impact

The study presented in this thesis focuses on the response of a side impact beam located in a car door to impact loading in close conformation to the Federal Motor Vehicle Safety Standard 214 (FMVSS 214) standard. The side impact beam is situated in both the front and rear side doors of a vehicle between the inner and outer shells to minimise intrusion into the passenger compartment whilst absorbing as much impact energy as possible in a collision. While some manufacturers use tubular side impact beams, others use corrugated structures. Different materials are also considered, depending on the class of vehicle, a nd market for which it is intended. In this study, a numerical model of a light -weight passenger car, developed by the National Crash Analysis Center (NCAC ) of The George Washington University under contract with the Federal Highway Administration (FHWA) and National Highway Traffic Safety Administration (NHTSA ) of the United States Department of Transportation (US DOT ), was used to simulate a side impact on the front side door using the LS -DYNA R7.1.1 explicit solver . The resulting deformation of the door from the full vehicle model was used to design an experiment for an impact test on a passenger door, which was used to validate an equivalent numerical simulation. In the experiments, the car door was modified and subjected to a drop mass of 385 kg from a height of 1.27 m. The drop mass and height were chosen such that the maximum deflection in the car door impact test would be of similar magnitude to the deflecti n of the door in full vehicle model when subjected to an impact load in accordance with the FMVSS 214 Standard - which requires that the vehicle be projected into a rigid vertical 10 inch diameter pole at 29 km/h in a direction 75° to the longitudinal axis of the vehicle . The results from the numerical simulation of the struck door test were in good agreement with the experiments in both shape and magnitude of deformation. The behaviour of the side impact beam located in the passenger door was isolated and further studied. Drop test experiments on beams with square and round cross -sections were carried out to validate the equivalent finite element model. The drop mass and height of the striker was varied such that the transient response of the isolated side impact beam matched the response of the beam in the simulation of the equivalent door model and full vehicle model. In the impact test experiments, the tubular structures were subjected to a 200 kg mass dropped from six incrementally varying heights of 250- 500 mm. Both square and round tubes were observed to buckle at approximately 835 mm from the free end with different magnitude s of maximum deformation (depending on the drop height). The results from the numerical simulations showed good correlation with the experiments for shape and magnitude of deformation. A quadratic curve fit to the experimental maximum transverse deflection resulted in an R -squared value of 0.92 and 0.96 for the square and round tubes respectively. A parametric study was carried out on the side impact beam to investigate the effect of: Thickness and material of a singular tube configuration, and: Inner tube length and outer tube thickness of a compound tube structure. The performance of the different configurations were assessed in terms of Crash Force Efficiency (CFE and Specific Energy Absorption (SEA). A parametric study on the effect of the tube thickness showed that thicker tubes of the same material exhibited deformation of lo wer magnitude and had lower SEA. Aluminium tubes absorbed two or more times the energy per unit mass than the equivalent steel tubes. A round aluminium tube with a thickness of 2.175 mm was found to give the best balance between SEA and maximum deflection with values of 1.5 kJ/kg and 350 mm respectively. The compound tube configuration with the inner tube extended beyond the buckling point performed better in terms of SEA and maximum deflection provided the length of the inner tube did not exceed 90% of the length of the outer tube. The optimised compound tube configuration performed better than the single tube configuration in the full vehicle model with a 1mm reduction in the overall intrusion of the rigid pole