Dynamic responses and reliability analysis of bridge double-column under vehicle collision

Vehicle Crush Prediction Using Finite-Element Techniques

Formulations on multibody dynamics are shown to be suitable for the development of methodologies for the impact simulation and crashworthiness design of vehicles The proposed design methods comprise a range of computer aided tools of increasing complexity and accuracy which can be used with greater advantage and efficiency in the different crashworthiness design stages The key issue in the use of such rigid and flexible multibody formulations is their capability to model and simulate efficiently the behavior of complex systems experiencing material and geometric nonlinear deformations while undergoing gross motion The proposed multibody based crashworthiness design methods and associated multibody dynamics tools require information about the structural nonlinear behavior of specific parts of the vehicle structures which can be obtained from numerical or experimental tests of specific structural components and subsequently used in the formulations Alternatively, the behavior of such components can be directly and efficiently incorporated through the use of appropriate nonlinear finite element procedures This hybrid feature lends to the present design tools flexibility, ease of use and efficiency gains, as a result of a better understanding of the crash phenomena with particular emphasis in the interaction of the gross motion with different collapse mechanisms Formulations for the sensitivity analysis and optimization of mechanical systems are also presented allowing for the design of optimum crash characteristics of energy absorption devices The capabilities of the design tools presented herein are demonstrated with several applications to different vehicles types in different crash-impact scenarios It is shown that the same formulations are applicable to enhanced occupant multibody models allowing extended injury assessment capabilities

Multibody Dynamic Tools for Crashworthiness and Impact

The CRASH3 computer program, a well known and useful tool in accident reconstruction, is shown to be inaccurate by comparison with car-to-car crash test data. Claims for accuracy of about 10 percent cannot be validated. Both the impact model and the damage only model yield results which are in error. Cases involving error well in excess of 20 percent are demonstrated. These inaccuracies are due primarily to the omission of terms in the formulation of the energy equation and to the sensitivity of the solution to the input estimate of principle-direction-of-force.

Inaccuracies in the crash3 program

Formulations based on multibody dynamics for the analysis of crashworthiness and impact of vehicles and structural systems are reviewed in this paper. A methodology to incorporate the elastodynamics effects, suitable to describe the elastic deformations of flexible bodies, is discussed. The limitations of this methodology for crash impact are overcome in a more general formulation where the deformation of the flexible (or partially flexible) bodies is described using an updated Lagrangian formulation. This allows for geometric and material nonlinear behavior of the multibody components. A major drawback of this nonlinear formulation is the inability to describe zones of concentrated deformation due to local instabilities. For this purpose the plastic hinge concept, where the structural plastic deformation is modelled by nonlinear joint-spring set-up, is used. The validity of this model is assessed by carrying out an experimental test where a hollow steel extruded beam collide with a rigid block. By predicting where and when failure is likely to occur using a flexible model, the present technique provides an efficient tool to access the crashworthiness design of a broad class of impact excited structural configurations with general kinematic constraints. Finally these methodologies are applied to model the rollover of a truck in order to illustrate their capabilities.

Flexibility in Multibody Dynamics with Applications to Crashworthiness

A Study on Automobile Crashworthiness

THE POSTCOLLISION MOTION STARTS IMMEDIATELY UPON COMPLETION OF A COLLISION IMPACT WHERE THE VEHICLES OBTAIN NEW SETS OF VELOCITIES THROUGH AN EXCHANGE OF MOMENTUM. SIMILITUDE WITH MODEL STUDY AND FULLSCALE AUTOMOBILE EXPERIMENTS INDICATE THAT THE POST-COLLISION TRAJECTORY IS ESSENTIALLY A PLANE MOTION, GOVERNED BY INERTIA AND TIRE FRICTION. TRAJECTORIES DEPEND ON MANY PARAMETERS (SUCH AS TIRE FRICTION COEFFICIENT, FRONT WHEEL STEERING ANGLE, VEHICLE GEOMETICS, AND WHETHER WHEELS ARE LOCKED OR FREE TO ROTATE) BUT NOT ON THE VEHICLE WEIGHT. THEORETICAL COMPUTATION OF TRAJECTORIES ARE COMPARED WITH EXPERIMENTS. /AUTHOR/

Richard I. Emori

Papers

A Study on Automobile Crashworthiness

Vehicle Trajectories After Intersection Collision Impact