ISSN:1358-8265    

DOI:10.1533/cras.1999.0087

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

Improvement in computer hardware and Finite Element (FE) software have made it possible to simulate complex phenomenon such as the behaviour of automobiles and roadside hardware during crashes. In this paper, the performance of a modified 3″×3″ slibase sign support system is evaluated using Finite Element simulations. The first task of the study consisted of developing an accurate finite element model of the new 3″×3″ slipbase. This is achieved by using full-scale tests that were conducted on an 8″×8″ slipbase at 32 and 96 km/hr (20 and 60 mph) to validate an 8″×8″ slipbase FE model. Once an accurak model of the 8″×8″ slibase is obtained, the exact modelling techniques used in developing this slipbase are used to construct a FE model of the 3″×3″ slipbase. The second task of this study involved using the 3″×3″ slipbase model to predict its behaviour in a 32 and 96 km/hr (20 and 60 mph) impacts. The predictions showed that modified 3″×3″ slipbase passes the NCHRP 350 safety Criteria. These predictions were compared to full-scale tests that were conducted subsequent to the simulations. It was found that the FE model accurately predicted the full-scale test results. The final task of this study consisted of coducting a parametric FE analysis to determine the maximum clamping force that can be applied to the 3″×3″ slipbase without causing it to fail the NCHRP 350 safety criteria The computer simulation parametric study revealed that the bolts can be clamped up to their yielding point and the slipbase will still pass the safety criteria of acceptable vehicle velocity change.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0088

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

A new side impact component test apparatus has been developed to recreate, in a cost-effective, repeatable, test environment, the kinematics of the intruding door, seat, and occupant as experienced in a full-scale side impact test. In this component test, a fixture-mounted door structure, complete with inner trim, is accelerated from rest using a pneumatic ram. The occupant is seated in a standard automobile seat that is mounted on rails to allow translation in the lateral direction. The onset and deceleration pulses of the seat and door can be tailored using programmable hydraulic decelerators in order to reproduce the velocity time history of intrusion as seen in a full scale test. A MADYMO model of the apparatus was developed to facilitate comparison of this test method to other side impact component tests, address design issues, and to demonstrate the effectiveness of this type of device in studying padding, spacing, and injury parameter development issues.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0089

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

ISSN:1358-8265    

DOI:10.1533/cras.1999.0090

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

The methods of multibody system dynamics provide most of the numerical tools required to construct models of vehicles and to describe biomechanical models of occupants with accuracy. Some of the most recent developments in this area of applied mechanics extended the basic capabilities of the multibody formulations to include the description of the system components deformation. For a given model of a vehicle each moving part is represented as a rigid body or as a flexible body experiencing linear elastic or fully nonlinear deformations. The relative motion of the system components is described by imposing kinematic constraints between them. the interactions among the system components, with other objects and multibody systems or even the coupling with the equations of other disciplines to describe aerodynamics effects or contact-impact conditions are efficiently modeled in this numerical environment. These characteristics suggest that the multibody methodologies provide appropriate ingredients to develop not only the simple conceptual models used in the early phases of the design process but also the more elaborate models of complex systems required for analysis. In this work, the position and orientation of each body of the system is described by a set of Cartesian coordinates or by natural coordinates, which consist in a set of points and vectors representing each body. For flexible bodies. the linear or nonlinear deformations are described with reference to a body fixed coordinate system using an updated Lagrangean formulation and the finite element method. In this form the equations of motion of the flexible bodies exhibit the coupling between the gross rigid body motion and the component flexibility. The relative motion between each of the multibody, components is assured by imposing kinematic constraints in the form of algebraic equations that relate the coordinates used to describe the system. The contact and impact between the system components and other bodies, internal or external to the system. is described using a continuous contact force model. Alternatively, unilateral constraints representing motion restrictions for a particular body in contact, are used. For situations where the deformed region of the component in contact is much smaller than the region of the same body that behaves in a rigid manner a kinetostatic formulation is used. Here, the inertial coupling between the body deformations and its gross motion is neglected. Finally, the formulations reviewed are applied to the description of a biomechanical model and several vehicle models that are simulated in different scenarios, including vehicle rollovers with and without occupants and pedestrian impact. Based on these applications the advantages of using a unified formulation to describe all systems are discussed.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0091

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

A method is developed for finding the best and worst possible responses of a child dummy in a child seat sled test where the sled deceleration pulse must follow a prescribed corridor. Constrained optimization techniques are applied to a two-degree-of-freedom lumped mass model of the sled test to determine the best and worst sled deceleration pulses, within the prescribed corridor, that produce the minimum and maximum child chest decelerations. A three-dimensional multi-body model is used to predict the values of the peak child chest g's in sled tests with the best and worst sled deceleration pulses. The results are useful as a measure of the variability of child dummy response that can be expected for a prescribed sled deceleration corridor. The standards for child seat safety testing can be evaluated and compared quantitatively using this sensitivity information. Results indicate that some prescribed sled deceleration corridors are too wide, allowing extreme variations in occupant responses, and some are too narrow, or perhaps unnecessarily complex.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0092

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

A search has been undertaken to find performance indices related to the dummy injury indices and which exhibit relatively simple behaviour across the design space. Finding such indices would allow a simple optimisation technique. requiring few simulations to be applied, aiding convergence on a successful design. Subject to the geometric constraints of the European side impact test, and the means used to change the model B Pillar, floor and rocker properties used in this study, such indices have been found. These performance indices were approximated across the design space using quadratic surfaces.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0093

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor

摘要:

The finite element method (FEM) has shown to be an effective and viable tool for simulating the events of a high-speed impact. As materials and methods for protecting the vehicle occupant advance, so must the capabilities of the FEM codes. One shortcoming that must be addressed is the way in which fracture (more appropriately failure) is currently modelled. Two problems exist when using the method of element erosion; 1) it is impossible to predict proper crack propagation with reasonably sized elements and 2) the stress distribution is inaccurately represented at the crack tip when elements are removed. To address this issue, a new fracture algorithm has been written and implemented into DYNA3D. This algorithm allows for prediction of both crack propagation and direction. Crack propagation is predicted using either a Crack Tip Opening Angle (CTOA) criteria or a plastic energy criteria. Crack growth direction is determined from the principle stresses of the elements surrounding the crack tip. The algorithm allows for a crack to split existing elements thus creating new elements and nodes respectively. The fracture algorithm has been validated for several classical fracture mechanics problems using standard engineering materials. The algorithm has been applied toward the prediction of the fracture modes of a long bone under different loading conditions. A model of the human tibia was subjected to pure tension, pure compression, pure torsion, and simple bending. The fracture algorithm was able to predict the proper modes of failure for tension, torsion, and simple bending. The algorithm had difficulty predicting the proper failure mechanism in compression. Future developments will focus on the application of the fracture algorithm to all material types in DYN A3D and the implementation of a better failure initiation criteria for bone.

ISSN:1358-8265    

DOI:10.1533/cras.1999.0094

出版商:Woodhead Publishing Ltd    

年代:1999

数据来源: Taylor