The effect on human body at the impact of tennis racket and balls from the viewpoints of mechanical characteristics of the grip

实验清楚地表明，球与球拍碰撞时产生的振动有两种频率，一种是130 Hz左右的高频，另一种是10 ~ 50 Hz左右的低频。这些结果使我们得出这样的结论：球拍在撞击时，一个是振动体，另一个是刚性物体。当球仅撞击拍面中心时，这种高频振动消失，而低频振动仍然存在于拍面上。这种规律的频率振动传递到手和前臂。在偏心冲击时，将握把的刚性由紧变松时，发现高频很难传递到手上，而低频则通过握把传递。Yoneyama， S.（2003）等研究报道，撞击后的振动可能导致“网球肘”。实验结果表明，当球拍作为刚体时，不仅高频振动产生于肘部，低频振动也产生于肘部。实验结果表明，球拍作为一个物体具有两种性质，一种是振动体，另一种是刚性物体。从这个角度出发，我们制作了一个刚体的冲击模型，球拍通过具有粘弹性特性的握把与手相连。利用该模型，对抓地力特性进行了研究。通过对比球与球拍接触时间、球的恢复系数、振动阻尼特性、振动频率和峰值等实验数据，对模型进行了识别。通过对模型的仿真可知，根据握把的松紧程度，握把的黏度系数在1.0 ~ 5.5 N/m/s之间变化，弹性系数在50 ~ 500 N/m之间变化。随着握把松紧度的变化，腕关节的粘弹性系数也会受到影响。少

Experiments reveal clearly that when the vibration occurred at the impact of a ball and a racket, there are two kinds of frequency, one is high frequency around 130 Hz and another one is low frequency around 10 to 50 Hz. These results lead us to the conclusion that the racket acts as one is a vibration body and another one is a rigid object at the impact. This high frequency vibration disappeared when a ball impacts only just on the center of racket face, and low frequency remains on the racket. This law frequency vibration transmits to a hand and a forearm though. At the off center impact, when changing the rigidity of the grip from tight to loose, it was found that the high frequency was hard to transmit to a hand, but low frequency passed through the grip. Yoneyama, S. (2003) and other studies reported that the vibration after the impact may causes the "tennis elbow". The results of this experiment reveal that not only the vibration of high frequency but also the low frequency origi … More nates in the tennis elbow, when the racket is regarded as a rigid body.Findings from the experimental results show that the racket acts as a body with two types of properties, one is a vibration body and another one is a rigid object at the impact. From this point of view, we made a model of impact as a rigid body, and the racket links to a hand through a grip that has the characteristics of visco-elasticity. By means of this model, the characteristics of grip are investigated. The model was identified by comparing the experiment data such as the duration time of contact with the ball and racket, the coefficient of restitution of ball, the characteristics of damping of vibration, the frequency and the peak value of vibration. From the simulation of the model, it is inferred that the coefficient of viscosity of grip changes 1.0 to 5.5 N/m/s and the coefficient of elasticity changes from 50 to 500 N/m, according to the tightness of grip. As the tightness of the grip changes, the visco-elasticity coefficients of wrist joint are also influenced. Less