摘要:

The objective of this paper is the analysis of large planar and biaxial bending rotation response of thin-walled beams with square cross-section filled partially or fully with aluminium foam. The beams were subjected to the cantilever bending, and the characteristics of moment-rotation response were investigated varying the length of foam-filling, the orientation angle, and the adhesive strength. A general purpose nonlinear FE code Pam-Crash was used to generate results. It was shown that the aluminium foam filler retards inward sectional collapse of thin-walled column so that the multiple folds are formed increasing the bending resistance considerably. The initial and subsequent shrinking of failure locus were constructed, and the normality rule was checked for the partially or fully foam-filled columns in biaxial bending collapse.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0148

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor

摘要:

A demonstrator car bumper system consisting of a transversal cross beam connected to two square columns with aluminium foam filler has been designed and experimentally subjected to dynamic loading conditions. The objective of the foam filled crash boxes was to absorb the kinetic energy involved in the crash. Using a drop hammer rig, the bumper system was subjected to two different loading conditions, namely a non-symmetric 40% load overlap as well as to a full contact impact. The foam filled crash boxes showed average forces within ± 10% of that predicted by using existing design formulas. In addition, the non-linear, explicit finite element code LS-DYNA was applied in order to simulate the complete crushing process. Compared to the scatter in the experimental results, the numerical simulations were able to predict the whole crushing of the bumper system with acceptable accuracy.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0149

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor

摘要:

Real life accidents provide important information for understanding pedestrianhehicle collisions. Collision speed is the critical parameter in determining pedestrian injury severity and, where possible, this has traditionally been estimated from tyre skid marks. However, the introduction of ABS brakes has increased the importance of pedestrian projection distance as a means of estimating collision speed in real life accidents. This paper presents a theoretical Hybrid Model relating collision velocity to pedestrian projection distance. The model combines the flight trajectory of a simple particle with the distribution of post head-impact velocities predicted by Wood's Single Segment Model (SSM). Comparison with staged and real life accidents shows good predictions of minimum, maximum and mean projection distances. The overall distribution of collision speeds has been used to predict upper and lower limits and a mean value of collision velocity for a given pedestrian projection distance.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0150

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor

摘要:

The paper presents results from research efforts focused on possible crashworthiness and safety improvements of existing Breakaway Cable Terminals (BCT). A need for such improvements became evident from several full-scale crash tests and preliminary computational mechanics analyses. A nonlinear, dynamic, 3-D finite element code LS-DYNA was utilized in the study to identify problems in the existing BCT. Analytical data and actual crash test results led to the conclusion that the terminal is too stiff in the initial phase of the end-on impact. Acceleration histories provided an evidence of poor dissipation of vehicle kinetic energy among different parts of the BCT. The study was restricted to existing terminals and its primary objective was to improve the crashworthiness of the terminal during end-on impacts. An expected low cost-to-benefit ratio was also an important constraint in this research. Finite element models of 820C passenger car (Honda Civic) and 2000P pickup truck (Chevrolet C2500) were adopted as impactors.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0151

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor

摘要:

Four different analytical methods were developed to evaluate the accuracy of a mathematical model to tit a crash test, defined by a set of experimental channels. For each evaluated curve, composed of an experimental and a simulation channel, one of these 4 methods is used and a score is computed, between 0 and 100%. A specifically developed software, ModEval, was made to perform these evaluations. Results were confirmed by an analysis of subjective model evaluations. made by 40 persons proficient in mathematical model designing.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0152

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor

摘要:

A method for accurately estimating chest velocity in air bag deployment tests is presented. It employs a state model of chest motion and a Kalman Filter to combine experimental acceleration and displacement measurements to estimate the velocity in a maximum likelihood sense. This technique uses statistics of the experimental and modelling noise to effectively combine the results of both types of measurements in making an accurate estimate of velocity. Results from highly demanding chest injury assessment tests, out-of-position air bag deployments, are presented. These results indicate that the problems associated with attempting to obtain velocity from either acceleration or displacement alone can be significantly reduced. Methods for estimating Kalman Filter parameters and assessing accuracy are presented. Accuracy comparisons are made between the Kalman Filter technique and SAE Recommended Practices for velocity estimation.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0153

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor

摘要:

Most of the previous work on the crush response of foam-filled columns was concerned with extruded aluminium profiles. This paper presents preliminary results of an on-going experimental project on the crush behaviour of closed top-hat foam-filled sections made of aluminium sheet. The manufacturing process of the foam-filled closed top-hat members was addressed first. Various joining techniques were investigated. Twenty-four axial crushing and twelve bending collapse tests were performed. Some important features of the crushing behaviour of closed top-hat members were revealed. The test results showed a promising future of thin-walled foam-tilled members as weight-efficient crash energy absorbers. More studies have to be carried out. especially on the techniques for joint integrity.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0154

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor

摘要:

The impact absorbing properties of a novel class of devices comprising stout, flexible, high tensile stiffness bags filled with a blend of small elastomeric capsules and a matrix liquid are described. The devices combine the elastic impact absorbing properties of elastomeric closed cell foams with the hydraulic pressure equalisation and viscous damping properties of liquids. The capsules can take many forms, including beads of expanded foams, bubble packing and air filled, open ended tubes. The matrix liquid, which may be a Newtonian liquid or a grease, contributes lubrication, viscous damping and pressure equalisation properties. The impact absorbing characteristics of the devices are less dependent on the shape of the contact face of the impacting body, compared with elastomeric foam impact absorbers, but uniaxial stiffness decreases, as the size of impact face of the device, relative to the impact zone, increases. Problems of package leakage and weight are addressed. The novel impact absorbing properties of the devices suggest that they could have a wide range of crash protection applications, including the design of pedestrian friendly vehicle front ends, to meet pending European legislative requirements.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0155

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor

摘要:

Methods for testing helmets are usually based on translatory acceleration vector measurements on a headform-helmet assembly exposed to impact in a special drop test rig. The measured acceleration is assumed to be related to a corresponding degree of brain damage on the helmet wearers head. However, medical research indicates that rotational acceleration above a certain level would have detrimental effects on the brain just as severe as the effects of translatory acceleration. The disregard of rotation in present standards would therefore make helmet testing incomplete and may give users a false impression about helmet protection quality. The question may also be raised if instead of using acceleration it might be better to base helmet testing on impact force, which has possibilities of more complete tests including influence of rotation. Furthermore, force based testing would facilitate production and ensure more reproducible results.

ISSN:1358-8265    

DOI:10.1533/cras.2000.0156

出版商:Woodhead Publishing Ltd    

年代:2000

数据来源: Taylor