微机化超声螺栓轴向应力仪的原理与误差分析

本文提出用沿轴向纵波声时差以测螺栓的轴向应力，推导了声时差与应力的关系．利用声时差测螺栓轴向应力，能克服耦会误差”“，同时还能克服温度引起的伸缩及波速变化的声时误差·本文还导出并且从实验上测出了，只与螺栓材料有关，而与螺栓的夹紧长度，直径，总长无关的常数，简化了测量过程．经实验测定，在夹紧长度大于30mm，应力低于240MPa时，应力最大误差小于±4MPa．本文还分析了声时，夹紧长度测量误差所导致的应力误差．

The principle and error analyses of microcomputer-based ultrasonic instrument for the measurement of axial bolt stress

This paper presents a method of measurment of the axial stress in a bolt from the transit time difference of longitudinalwaves in tihgtedand unstressed bolt. Measuring stress by the transit time difference method can avoid error in the transit time in couplers as well as that in the transit time arising from the thermal expansion and thermal variation of ultrasonic velocity. The paper infers and measures experimentally a constant which depends only on the bolt material and not on the clamped length, diameter or length of the bolt. The paper also analyzes the effects of errors in the transit time and in the clamped length on the error of stress. Experimental result shows that the error of stress is less than t 4 MPa when clamped length is more than 30 mm and the stress is less than 240MPa.