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Technical Paper

Incidence and Mechanism of Head, Cervical Spine, and Lumbar Spine Injuries for Occupants in Low- to Moderate-Speed Rear-End Collisions

2021-04-06
2021-01-0900
Automotive accidents and subsequent personal injury claims incur significant costs annually. While seat and head restraint design continue to evolve and improve, occupant safety and injury risk assessment in rear-end collisions remain at the forefront of automotive innovation. In this study, we combined statistical analyses of nine years (2007-2015) of data from the National Automotive Sampling System Crashworthiness Data System (NASS-CDS) database and one year (2017) of data from the Crash Investigation Sampling System (CISS) database with data acquired from vehicle-to-vehicle crash tests conducted with instrumented anthropomorphic test device (ATD) occupants in order to compare and relate field injury rates with potential mechanisms underlying head, cervical spine, and lumbar spine injuries in low-to moderate-speed rear-end collisions.
Technical Paper

Crashworthiness optimization of hydraulic excavator cab roof rail and predicting the safety provided by protective structures using finite element analysis

2021-04-06
2021-01-0925
Off-road trucks, tractors and earth-moving machines are at high risk of accidents involving falling objects or rollovers. Therefore, these machines need to be equipped with proper protective structures. This study designed roof rail of a hydraulic excavator cab using an improved BESO method considering two impact load cases. A new method using explicit finite element (FE) analysis is proposed to predict the performances of roll-over protective structure (ROPS) under standardized laboratory test. In the crashworthiness optimization problem, a weighted summation of external works of two load cases treated as objective function while the volume treated as constraint. A mutative weight scheme is proposed to stabilize the optimization and balance the two independent load cases. The smooth evolution histories of structural responses demonstrate the effectiveness of mutative weight scheme. The optimal design is interpreted and two prototypes are fabricated.
Book

Fundamentals of Automobile Body Structure Design, 2nd Edition

2020-08-04
This book provides readers with a solid understanding of the principles of automobile body structural design, illustrating the effect of changing design parameters on the behavior of automobile body structural elements. Emphasizing simple models of the behavior of body structural systems rather than complex mathematical models, the book looks at the best way to shape a structural element to achieve a desired function, why structures behave in certain ways, and how to improve performance. This second edition of Fundamentals of Automobile Body Structure Design contains many new sections including: the treatment of crashworthiness conditions of static roof crush and the small overlap rigid barrier torsion stiffness requirements material selection illustrations of body architecture Each chapter now includes a clear flow down of requirements following the systems engineering methodology.
Standard

Cab Sleeper Occupant Restraint System Test

2020-07-07
WIP
J1948
This SAE Recommended Practice provides a standardized test procedure for heavy-duty truck sleeper berth restraints to determine whether they meet the FMCSR 393.76(h) requirements.
Technical Paper

Crash Response of a Repaired Vehicle - Influence of Welding UHSS Members

2020-04-14
2020-01-0197
Automakers generally recommend not to weld structural parts after a vehicle crash, and these should be replaced as a whole part in case of a crash event. Sectioning of these members is also not recommended and use of the repair manual is mandatory in case of fracture of such parts. However, repair shops may not adhere to these instructions and use incorrect repair procedures on these members which would modify their strength properties. This study analyses the impact of welding structural members in a vehicle like the A-pillar which use Ultra-High Strength Steels (UHSS) for reducing the weight of the vehicle and improving the crashworthiness of the structure. The research conducted in this paper highlights the differences in the crash performance of a repaired vehicle as opposed to baseline injury values for the vehicle.
Technical Paper

Crashworthiness Design of Hierarchical Honeycomb-Filled Structures under Multiple Loading Angles

2020-04-14
2020-01-0504
Thin-walled structures have been widely used in automobile body design because of its good lightweight and superior mechanical properties. For the energy-absorbing box of the automobile, it is necessary to consider its working conditions under the axial and oblique impact. In this paper, a novel hierarchical honeycomb is proposed and used as filler for thin-walled structures. Meanwhile, the crashworthiness performances of the conventional honeycomb-filled and the hierarchical honeycomb-filled thin-walled structures under different impact conditions are systematically studied. The results indicate the energy absorption of the hierarchical honeycomb-filled thin-walled structure is higher than that of the conventional honeycomb-filled thin-walled structure, and the impact angle has significant effects on the energy absorption performance of the hierarchical honeycomb-filled structure.
Technical Paper

An Innovative Approach to Component Testing Using an Impact Sled

2020-04-14
2020-01-1331
Historically, crash development component testing has been conducted using gravity-based vertical drop towers. The drop tower carriage is loaded to a specified weight, raised to a specific height to achieve an energy target, and dropped onto the part. This long-used approach has significant limitations with respect to achievable speed and energy, part orientation, impact angle, useable impact surface, component size, etc. With the wide variance in simulating today’s global crash scenarios, a better approach is being developed using an impact sled. The most significant advantage of this system is that there is a much higher achievable speed and energy which can be controlled with precise accuracy. This paper will provide an overview of the impact sled test system, as well as the methodology used to conduct the testing. The overview will include the challenges faced during the development of the impact sled, as well as the need for accurate and precise component fixturing methods.
Technical Paper

Frontal Crash Worthiness Performance of Bi-Tubular Corrugated Conical: Structures under Axial Loads at Low Velocity

2020-04-14
2020-01-0983
Vehicle collisions are a major concern in the modern automotive industry. To ensure the passenger safety, major focus has been given on energy absorption pattern on the crumple zone during collision, which lead to the implementation of new design of the crash box for low speed collision. The main aim of this research is optimization of the conical shaped structure based on its mean diameter, graded thickness and semi apical angle. Further, to decrease initial peak load of the conical crash box, corrugations are integrated on structure and optimized based on different parameters, such as number of corrugations, pattern of corrugation relative to both tubes and amplitude of corrugation. The concept of bi-tubular structure is proposed to improve both specific energy absorption and initial peak load during crash event. A finite element model is created to perform parametric study on corrugated conical tube based on axial load conditions at low velocity.
Technical Paper

Kriging-Assisted Structural Design for Crashworthiness Applications Using the Extended Hybrid Cellular Automaton (xHCA) Framework

2020-04-14
2020-01-0627
The Hybrid Cellular Automaton (HCA) algorithm is a generative design approach used to synthesize conceptual designs of crashworthy vehicle structures with a target mass. Given the target mass, the HCA algorithm generates a structure with a specific acceleration-displacement profile. The extended HCA (xHCA) algorithm is a generalization of the HCA algorithm that allows to tailor the crash response of the vehicle structure. Given a target mass, the xHCA algorithm has the ability to generate structures with different acceleration-displacement profiles and target a desired crash response. In order to accomplish this task, the xHCA algorithm includes two main components: a set of meta-parameters (in addition target mass) and surrogate model technique that finds the optimal meta-parameter values. This work demonstrates the capabilities of the xHCA algorithm tailoring acceleration and intrusion through the use of one meta-parameter (design time) and the use of Kriging-assisted optimization.
Technical Paper

Bi-Directional Evolutionary Structural Optimization for Crashworthiness Structures

2020-04-14
2020-01-0630
Gradient based topology optimization method is difficult used to optimization of crashworthiness structures due to the expensive computational cost of sensitivity analysis and complex nonlinear behaviors (geometric nonlinearity, material nonlinearity and contact nonlinearity) of structures during a collision. Equivalent static loads (ESLs) method is one of the methods for nonlinear dynamic response optimization. However, this method ignores the material nonlinearity. Thus this paper proposes an improved topology optimization method for crashworthiness structure based on a modified ESLs method. A new calculation of ESLs considering material nonlinearity is proposed. The improved ESLs method is employed to transform the nonlinear dynamic response optimization into a nonlinear static response optimization with multiple load cases. Each element in the design domain is assigned with a design variable.
Technical Paper

Accident Statistical Distributions from NASS CDS - An Update

2020-04-14
2020-01-0518
The National Automotive Sampling System (NASS) Crashworthiness Data System (CDS) contains an abundance of field crash data. As technology advances and the database continues to grow over the years, the statistical significance of the data increases and trends can be observed. The purpose of this paper is to provide a broad-based, up-to-date, reference resource with respect to commonly sought-after crash statistics. Charts include up-to-date crash distributions by Delta-V and impact direction with corresponding injury severity rates. Rollover data is also analyzed, as well as historical trends for injury severity, belt usage, air bag availability, and the availability of vehicle safety technology.
Technical Paper

Likelihood of Spinal Disc Herniations in Occupants Involved in Real World Side Impacts

2020-04-14
2020-01-0526
The prevalence of spinal disc herniations in people with no spinal symptoms have been reported to increase with age; from about 20% in those below 40 years to about 30% in those above 40 years. Spinal disc herniations are usually associated with degenerative changes. Though rare, spinal disc herniations can also be caused by trauma. With an increasing number of older people on U.S. roads with a concomitant increase in the probability of getting injured in a vehicle collision, it is reasonable to expect that some of these occupants can present with clinical findings of spinal disc herniations after a side impact, and attribute these findings to the impact. In this study, we looked at the relationship between real world side impacts and the occurrence of spinal injuries, in particular disc herniations, in occupants involved in such impacts.
Journal Article

Material Characterization of Extruded Aluminum Axial Tubes as Energy-Absorbing Structural Members

2019-11-21
Abstract The increasing use of aluminum alloy extrusion in automotive vehicle chassis as structural members has necessitated the need to investigate their crushing behaviors. This article experimentally examines in detail, for the first time with respect to strength, ductility, and microstructure, AA6063-T7 (overaged) condition and the standard T6 temper and their capacity to meet crashworthiness requirements. Both tempers were assessed based on their mechanical properties (strength, ductility, true stress/strain behavior to necking, plastic anisotropy, strain rate sensitivity, and post-instability ductility to fracture) and microstructure, which were determined using basic tensile testing methods and metallographic approach.
Technical Paper

Next Steps for the IIHS Side Crashworthiness Evaluation Program

2019-07-08
SC18-22-0002
Abstract - IIHS has been conducting side impact crash tests since 2003. To understand how the side crashworthiness program can be enhanced, an ongoing research effort is focused on understanding the correlation between IIHS ratings and driver death rate. In addition, the performance of good-rated late-model vehicles has been assessed in higher severity side crash tests. The purpose of this short communication is to summarize the ongoing work and potential next steps toward developing a new crash test procedure or updating ratings criteria to further advance side crashworthiness.
Technical Paper

Design for Crashworthiness of Vehicle Structures Using an Extended Hybrid Cellular Automaton Method

2019-04-02
2019-01-0842
This paper introduces a design methodology to tailor the acceleration and displacement responses of a vehicle structure subjected to a dynamic crushing load. The proposed approach is an extension of the hybrid cellular automaton (HCA) method, through which the internal energy density is uniformly distributed within the structure. The proposed approach, referred here to as an extended HCA (xHCA) method, receives the suitable combinations of volume fraction and a finite element meta-parameter for which the algorithm synthesizes the load paths that allow the desired crash response. Lower meta-parameter values lead designs obtained by traditional optimizers, while larger values lead to designs obtained by the HCA method. Simultaneous implementation of multiple values of meta-parameters is presented here as a further development of xHCA method.
Technical Paper

Structural Optimization of Thin-Walled Tubular Structures for Progressive Collapse Using Hybrid Cellular Automaton with a Prescribed Response Field

2019-04-02
2019-01-0837
The design optimization of thin-walled tubular structures is of relevance in the automotive industry due to their low cost, ease of manufacturing and installation, and high-energy absorption efficiency. This study presents a methodology to design thin-walled tubular structures for crashworthiness applications. During an impact, thin-walled tubular structures may exhibit progressive collapse/buckling, global collapse/buckling, or mixed collapse/buckling. From a crashworthiness standpoint, the most desirable collapse mode is progressive collapse due to its high-energy absorption efficiency, stable deformation, and low peak crush force (PCF). In the automotive industry, thin-walled components have complex structural geometries. These complexities and the several loading conditions present in a crash reduce the possibility of progressive collapse. The Hybrid Cellular Automata (HCA) method has shown to be an efficient continuum-based approach in crashworthiness design.
Technical Paper

Dynamic Crushing Behaviors of Four Kinds of Auxetic Structures

2019-04-02
2019-01-1096
Auxetic structures/materials with the negative Poisson’s ratio (NPR) properties can contract when compressed and expand when stretched, different from the conventional structures/materials. Due to the unique properties, it can have higher stiffness and better impact resistance with lightweight. Therefore, the auxetic structures/materials have been applied in various engineering field, such as automobile crash box, suspension mount etc. For auxetic structures/materials with negative Poisson’s ratio, there are four typical configurations (re-entrant hexagonal, double-V, tetra star-shaped and tetra-chiral). However, comparisons on the dynamic behaviors and crashworthiness between the four auxetic structures have not been studied. In this paper, the finite element models were developed for four typical auxetic structures. The deformation modes and energy absorption properties of four different auxetic structures were explored under different impact velocities.
Technical Paper

Simulation and Experimental Study on Crashworthiness of CFRP Body Electric Vehicle

2019-04-02
2019-01-1100
Carbon fiber reinforced plastic (CFRP) composite materials typically have a high strength-to-weight ratio, which is the one of excellent solutions to develop the next generation of lightweight vehicles in automotive engineering, especially for electric vehicles. However, the process of acquiring mechanics properties under quasi-static and dynamic loading, construction of the constitutive model, building and validating crashworthiness model of CFRP materials remain research worthiness. The purpose of this study is to establish the passive safety model, connection, analysis and related methods of CFRP materials body, and to understand its crashworthiness. Based on the explicit numerical algorithm of LS-DYNA, the composite constitutive model *MAT_54 and adhesive constitutive model *MAT_169 are chosen.
Technical Paper

Constructing a Concept Vehicle Structure Optimized for Crashworthiness

2019-04-02
2019-01-0613
Multi-disciplinary optimization (MDO) of a vehicle structure at the earliest stages of design is critical as OEMs are pressed to reduce the design time in order to respond to various demands from the market. MDO for the three essential areas of performance of the vehicle structure (NVH, Crash, and Durability) needs the throughput for each of the major disciplines to be approximately in the same range of turn-around time. However, crashworthiness simulation typically takes significantly longer than the others, making it difficult to include crashworthiness in the MDO. There have been many approaches to address crash simulation in a shorter time. The lumped mass-spring method is one of the approaches but has not been widely accepted since there are many difficulties in modeling and replicating the existing structure.
Technical Paper

Design and Optimization of Crash-Box of Passenger Vehicle to Enhance Energy Absorption

2019-03-25
2019-01-1435
Frontal crash is the most common type of accidents in passenger vehicles which results in severe injuries or fatalities. During frontal crash, some frontal vehicle body has plastic deformation and absorbs impact energy. Hence vehicle crashworthiness is important consideration for safety aspect. The crash box is one of the most important parts in vehicle frontal structure assembly which absorb crash energy during impact. In case of frontal crash accident, crash box is expected to be collapsed by absorbing crash energy prior to the other parts so that the damage to the main cabin frame and occupant injury can be minimized. The main objective of this work is to design and optimize the crash box of passenger vehicle to enhance energy absorption. The modeling of the crash box is done in CATIA V5 and simulations are carried out by using ANSYS. The results show significant improvement in the energy absorption with new design of the crash box and it is validated experimentally on UTM.
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