A Combined Experimental Theoretical And Numerical Approach To Bending Collapse In Empty And Filled Thin Walled Structures For Automotive Crashworthiness Applications

Concerns have been raised for many years about the quality and safety of the vehicles as well as their contribution to the air pollution that endangers public health. Several vehicle safety standards have been developed for different crash scenarios. To improve air quality and reduce vehicle’s emissions, there are high interests to amend vehicle fuel consumption through producing light weight vehicles. These improvements should not menace vehicle safety. Vehicle designers achieve safety and fuel economy advances through using lightweight materials like aluminum alloys, high strength steels, tailored beams and composite materials in the vehicle’s structures. In this research, finite element crash simulation of a vehicle model is considered to characterize the energy absorption capacity of the vehicle’s frontal structure. Crashworthiness optimization technique is implemented to reduce the weight of selected frontal elements while vehicle safety performance is improved. Crush performance of the two most effective vehicle’s frontal crash elements, namely, crash box and bumper beam is investigated by a comprehensive experimental and numerical study in axial, oblique and bending crush conditions. The energy absorption mechanisms of these elements are characterized briefly and multi design optimization MDO technique is implemented to maximize their energy absorptions and reduce their weights. The crush behavior of low density materials like aluminum honeycomb and foam is studied. The concept of filling crash box and bumper beam with these materials is investigated experimentally and numerically. The same MDO procedure which is used for empty aluminum crash box is implemented to maximize the energy absorption capacities of the filled structures and minimizing their weights. Experimental and numerical research is performed to investigate the crush behavior of thermoplastic composite crash boxes. The energy absorption mechanisms of composite materials and its differences to aluminum alloys are studied. The effort is conducted to characterize the energy absorption of the foam-filled composite crash box. The MDO procedure is used to maximize energy absorption capacity of the composite crash box and minimize its weight. Finally the optimum composite crash box is compared with the optimum aluminum crash box. In the above mentioned optimization procedures, practical and safety requirements are considered as optimization constraints. The theoretical methods of predicting the crush behavior of empty and filled crash box and bumper beam are sammaried. The experimental results are used to calibrate these formulations. The calibrated expressions can be used in the primary phase of the vehicle’s structural design.

FROM THE INTRODUCTION Vehicle crashworthiness has been improving in recent years with attention mainly directed towards reducing the impact of the crash on the passengers. Effort has been spent in experimental research and in establishing safe theoretical design criteria on the mechanics of crumpling, providing to the engineers the ability to design vehicle structures so that the maximum amount of energy will dissipate while the material surrounding the passenger compartment is deformed, thus protecting the people inside. During the last decade the attention given to crashworthiness and crash energy management has been centered on composite structures. The main advantages of fibre reinforced composite materials over more conventional isotropic materials, are the very high specific strengths and specific stiffness which can be achieved. Moreover, with composites, the designer can vary the type of fibre, matrix and fibre orientation to produce composites with proved material properties. Besides the perspective of reduced weight, design flexibility and low fabrication costs, composite materials offer a considerable potential for lightweight energy absorbing structures; these facts attract the attention of the automotive and aircraft industry owing to the increased use of composite materials in various applications, such as frame rails used in the apron construction of a car body and the subfloor of an aircraft, replacing the conventional materials used. Our monograph is intended to provide an introduction to this relatively new topic of structural crashworthiness for professional engineers. It will introduce them to terms and concepts of it and acquaint them with some sources of literature about it. We believe that our survey constitutes a reasonably well-balanced synopsis of the topic.

This important study focuses on the way in which structures and materials can be best designed to absorb kinetic energy in a controllable and predictable manner. Understanding of energy absorption of structures and materials is important in calculating the damage to structures caused by accidental collision, assessing the residual strength of structures after initial damage and in designing packaging to protect its contents in the event of impact. Whilst a great deal of recent research has taken place into the energy absorption behaviour of structures and materials and significant progress has been made, this knowledge is diffuse and widely scattered. This book offers a synthesis of the most recent developments and forms a detailed and comprehensive view of the area. It is an essential reference for all engineers concerned with materials engineering in relation to the theory of plasticity, structural mechanics and impact dynamics. Important new study of energy absorption of engineering structures and materials Shows how they can be designed to withstand sudden loading in a safe, controllable and predictable way Illuminating case studies back up the theoretical analysis

Governed by strict regulations and the intricate balance of complex interactions among variables, the application of mechanics to vehicle crashworthiness is not a simple task. It demands a solid understanding of the fundamentals, careful analysis, and practical knowledge of the tools and techniques of that analysis. Vehicle Crash Mechanics s

(Cont.) Using the analytical closed form expression of the crushing force of "S" shaped frame, the optimization process was performed based on Sequential Quadratic Programming. As a more realistic application, a front side rail and subframe structure of a mid size passenger car is analyzed. The combinational optimization process of "Design of Experiment" and "Response Surface Method" is carried out with the objective of weight minimization while maintaining the same or higher level of crash energy absorption. Both methods of internal reinforcement show high increase in the energy absorption and weight efficiency. The gain in terms of the specific energy absorption varies from 37% to 267% depending on the method. The proposed theoretical understanding and the design methodologies could be used as crash oriented early-stage component design tools.

This Festschrift is dedicated to Professor Dr.-Ing. habil. Peter Wriggers on the occasion of his 60th birthday. It contains contributions from friends and collaborators as well as current and former PhD students from almost all continents. As a very diverse group of people, the authors cover a wide range of topics from fundamental research to industrial applications: contact mechanics, finite element technology, micromechanics, multiscale approaches, particle methods, isogeometric analysis, stochastic methods and further research interests. In summary, the volume presents an overview of the international state of the art in computational mechanics, both in academia and industry.

Simplified modeling generates a great deal of interest in the area of crashworthiness analysis. Modeling methods used to create simplified computer models for crashworthiness have been well developed. In advanced simplified models, researchers develop simplified elements that can correctly predict structure's crash behavior based on the existing collapse theories. These developed simplified elements then are applied to develop the simplified models. Nevertheless, most of the exiting collapse theories are regarding the thin-walled box section beams. However, in addition to the box section member, the channel section member is another popular member and is widely used in engineering for architectural structures, vehicles, and etc. Therefore, to simplify the thin-walled channel section beams, new collapse theory is required to predict the crash behavior for such beams. This topic is the focus of this dissertation. This dissertation develops a mathematical model to predict the crash behavior of the thin-walled channel section beams based on their real collapse mechanisms. The derived math formulae are verified through several basic applications. After that, both the existing collapse theories and the developed collapse theory regarding the thin-walled channel section beams are applied to simplify the detailed truck chassis model. The developed simplified model is used for crashworthiness analysis and the results are compared to those from the detailed model. The developed theory and the modeling method are then validated through the comparison. Additionally, in developing the simplified truck chassis model, the cross members that were modeled using coarse shell elements in previous simplified models are remodeled using simple elements. Two of the simplified modeling methods, the superelement method and the equivalent beam method, are utilized to generate the simplified models for the cross members of the truck chassis model. The principle of both methods is to use simple elements to transfer the original members' mass and stiffness matrices. The equivalent beam method is recommended after comparison of the results of the crashworthiness analyses of each method. The primary contributions of this work are first, the derivation of crash theory that can predict the crash behavior of thin-walled channel section beams. The second is the use of equivalent beams to simplify the cross members within truck chassis models. Finally, a simplified modeling methodology is presented and evaluated. All the theory and modeling method developed in this work are applied for creating simplified models. Both the simplified and detailed models are used for crashworthiness analyses, results show that the errors caused by the simplified models are fewer than 10% and the simplified models only take less than 10% of the computer time of the corresponding detailed models.

Structural Impact is concerned with the behaviour of structures and components subjected to large dynamic, impact and explosive loads which produce inelastic deformations. It is of interest for safety calculations, hazard assessments and energy absorbing systems throughout industry. The first five chapters introduce the rigid plastic methods of analysis for the static behaviour and the dynamic response of beams, plates and shells. The influence of transverse shear, rotatory inertia, finite displacements and dynamic material properties are introduced and studied in some detail. Dynamic progressive buckling, which develops in several energy absorbing systems, and the phenomenon of dynamic plastic buckling are introduced. Scaling laws are discussed which are important for relating the response of small-scale experimental tests to the dynamic behaviour of full-scale prototypes. This text is invaluable to undergraduates, graduates and professionals learning about the behaviour of structures subjected to large impact, dynamic and blast loadings producing an inelastic response.