Impact dynamics of mechanical systems and structures, and applications in crash energy management, impulse mitigation, and impact injury biomechanics

Abstract

Among the different load conditions on a mechanical system, impact loading and its contribution to the design process require special consideration. The static methods of stress, strain, and deflection analyses are not applicable under impact conditions. The main goal of this study is to address the fundamental aspects of impact and to examine its applications for different design requirements. First, different approaches to the impact phenomena, namely stereomechanics, contact mechanics, stress wave propagation, finite element method, and energy method are investigated in this dissertation. The advantages and disadvantages of each method are pointed out, and the areas of application of each method and the degree of accuracy are examined. Quantification of energy absorption during impact is the most complicated part of impact modeling and is one of the topics of interest addressed in this dissertation. Application of the impact analysis methodologies in vehicular accidents and protection of occupants are the eventual goals of this research, demonstrated using some case studies and applicable examples. Because occupant safety is a major concern in the automobile and aerospace industries, a crashworthy design must be able to dissipate the kinetic energy of impact in a controlled manner. Four test cases or applications related to impact energy management or dissipation, impulse mitigation, and impact injury biodynamics are thus presented. The application examples include the design of a truck side guard and quantification of its effects on reducing occupant injury in the collison of a small car with a truck; lumbar load attenuation for seated occupants of a rotorcraft; injuries to pedestrians impacted by a sport or utility vehicle equipped with a frontal guard; and investigation of a motorcyclist impact with roadside barriers. For each case, an analysis methodolgy is developed, and from the modeling and simulations, impact design issues are addressed.