摘要:

This article examines the dynamic axial crushing of thin-walled sections made from ductile metals and uses these solutions to explore several important phenomena in the structural crashworthiness field. In particular, the range of validity of quasi-static behaviour is explored, and the transitions to dynamic plastic buckling and global bending are discussed. Some observations are made on several phenomena associated with the dynamic material properties which are important for the large strains and the range of strain rates encountered in structural crashworthiness problems.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0110

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

The energy absorption process of metallic cylindrical shells under dynamic axial loading is determined with the help of different theoretical models, which describe the dynamic buckling and folding process. Firstly the dependency of the load-carrying capacity and the buckling mode on the shell geometry and the time dependent loading conditions are investigated. Calculations with two different theoretical models are performed in the time domain. The first model is based on the beam on elastic foundation. It includes geometric imperfections and shear deformations and is capable of describing the symmetric dynamic buckling process. The second model is based on the exact complete shell bending theory and considers non-axisymmetric buckling modes as well as plasticity. The determined buckling modes lead to a geometric description of the folding pattern. Considering the formation of plastic hinges the absorbed energy due to axial crushing is calculated for an appropriate example. The results are compared to those, achieved by an explicit finite element code.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0111

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

In cars, often special changeable energy absorber units are used in order to reduce repair costs attributed from minor accidents. These kinds of absorber units are cheap and easy to change at low cost. Thus, one of the solutions showing such affordable energy absorbers is presented herein as a tapering mechanism. This uses a circular tube which is circumferentially reduced by a tapered die during impact. This tapering process of tubes (steel or aluminium) has proved to be efficient and absorbs more energy than either tube inversion or progressive buckling. The paper also presents some analytical predictions for such devices. The mechanism of tapering is thereby described using kinematic relations and energy considerations. This closed-form solution shows the influence of material and geometrical parameters on the mean impact load. Overall, extensive experimental studies with different materials, lubrications, tubes and dies have been performed. The varied parameters are thickness, diameter, die angle and degree of deformation. The influence of friction is tested using grease and oil lubrication and without lubricant. Experimental data show good agreement with analytical results.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0112

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

The paper deals with the numerical simulation of crushing processes of axially compressed axisymmetric shells, by application of the upper bound theorem of limit analysis in combination with an FE-like discretization. In order to account for large deformations, a sequence of optimization problems, each followed by a geometrical update, is solved for the unknown velocity parameters. Frictionless contact can be taken into account simply through the enforcement of additional inequalities entering the optimization problems. In order to allow an accurate (though numerically relatively simple) computation of the internal energy dissipation, the exact form of the llyushin yield surface is applied, expressed exclusively in terms of kinematic quantities. The proposed numerical procedure allows to study crushing processes of general axisymmetric structures with great accuracy. Analytically based kinematic mechanisms, proposed in the literature, can be regarded as special cases, which allows to investigate the influence of simplifications used in such models.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0113

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

A program is underway to develop and validate a high fidelity finite element model of a full size car for crashworthiness analysis. This study is part of an overall program to develop a set of detailed finite element models for various vehicles that represent the range of vehicle types currently on the road. These vehicle models can then be used to study how future lightweight vehicles will change the overall crash safety of the fleet.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0114

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

This paper presents the results of a three-dimensional finite element simulation study to analyse the crashworthiness of a modified thrie-beam guard-rail during vehicle impacts. In this study, a model of a compact automobile (model 820C vehicle, provided by the FHWA) impacting a model of a modified thrie-beam guardrail (developed at the University of Mississippi) at 100.6 kdhour has been employed. The simulated results of the 820C vehicle impact at an angle of 15 degrees showed better comparison with the results obtained from the actual crash tests. The study was extended to simulate the event of a C2500 pickup truck impacting the modified thrie-beam guard-rail model. The maximum computed deflections of the guard-rail were 307 mrn and 500 mm respectively for the 820C car model and the reduced pickup truck model. Further, a simulation of the impact of a detailed pickup truck model under the same impact condition was conducted. The simulation results indicate that the guardrail model was performing properly and as expected and the two pickup truck models were redirected after impact and left the guardrail without any significant problem. The results demonstrate the significant computational efficiency of the reduced pickup truck model for crashworthiness simulations.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0115

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

In an environment where resources are scarce, decisions to spend more on safety or risk reduction need to be made on a rational basis. The assessment of such a situation must reflect the impact on society as a whole. When death and injury are involved the assessment, hence becomes very complicated. This paper discusses how societal cost models can assist in making these difficult decisions and an example is analysed based on train crashworthiness.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0116

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

This paper describes some applications of the computer-aided analysis tools typically used in the studies of the crash responses of aircraft seats and occupants. The methodology used incorporates a combination of non linear finite element analysis and multibody modeling of the seat and the occupant as well as component testing in early design stages, and sled and/or full-scale testing in later stages of design evaluations. The nature of the current crashworthiness standards is first discussed. The systems approach utilised for the aircraft seat design process is briefly described. Examples of this systems approach methodology for some of the current crash safety issues are then presented and the importance of the CAE tools in these crashworthiness problems is demonstrated. These crashworthiness problems include the head impact protection for seats facing the bulkhead, the solution to the proposed 32G commuter seat, and the certification criteria for side-facing aircraft seats. Using this methodology and the CAE tools, solutions to these crashworthiness problems are arrived at.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0117

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

ISSN:1358-8265    

DOI:10.1533/cras.1999.0118

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor