The rapid spread of various sports games has changed the role of shoes from the simple protection of human feet to more advanced ones like competency improvement. Accordingly, intensive research efforts are being focused on the development of high-competency sports shoes by taking kinesiology and biomechanics into consideration. However, the success of this goal depends definitely on the reliable evaluation of the main functions required for sports shoes. As the first part of our study on the landing impact analysis of court sports shoes, this paper introduces a coupled foot-shoe finite element model in order to fully reflect the mutual interaction between the foot and the shoe, not relying on traditional independent field experiments any more. Through illustrative numerical experiments, we assess the reliability of the proposed coupled FEM model by comparing with the experimental results and investigating the fundamental landing impact characteristics of sports shoes.
This paper investigates the effects of sports ground materials on the transfer characteristics of the landing impact force using a coupled foot-shoe-ground interaction model. The impact force resulting from the collision between the sports shoe and the ground is partially dissipated, but the remaining portion transfers to the human body via the lower extremity. However, since the landing impact force is strongly influenced by the sports ground material we consider four different sports grounds, asphalt, urethane, clay and wood. We use a fully coupled 3-D foot-shoe-ground interaction model and we construct the multi-layered composite ground models. Through the numerical simulation, the landing impact characteristics such as the ground reaction force (GRF), the acceleration transfer and the frequency response characteristics are investigated for four different sports grounds. It was found that the risk of injury, associated with the landing impact, was reduced as the ground material changes from asphalt to wood, from the fact that both the peak vertical acceleration and the central frequency monotonically decrease from asphalt to wood. As well, it was found that most of the impact acceleration and frequency was dissipated at the heel, then not much changed from the ankle to the knee.
This paper deals with the process to identify the exciting forces generated from a rotary compressor. The equation of motion of a rigid compressor supported by several mounts was derived with 6 degree of freedom. The mass moment of inertia of compressor and the stiffness of rubber mounts were also identified by experiments. The exciting force at the center of mass of the compressor were estimated from the acceleration data measured at compressor shell. The piping system connected to the compressor was modeled. The acceleration of a pipe was predicted numerically by using the predicted exciting force. The numerical results showed good agreement with experimental results, which validated the identified exciting force.
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