基于TDC的L(下标 CR)波切向应力检测方法的研究

Based on the relationship between the sound velocity and stress in solid and the theory of generating critically refracted longitudinal (L(subscript CR)) wave, the practical way to measure the shear stress inside the workpiece from the surface by L(subscript CR) wave is presented, and the structure and working principle of the evaluation system is described detailedly. In order to measure the little change in travel time of L(subscript CR) wave caused by stress variation, the time digital converter (TDC) based on the delay in transmitting time of logic gate is employed to meet the demand of high precision measurement. Moreover, the manner of single-point transmission and double-point reception is used to decrease the measuring errors and improving the precision.