利用拉伸试验机和超声应力检测仪,对水电机组蜗壳螺栓45钢进行轴向拉伸,测定其在拉伸过程中的应力值和对应的超声波纵波和横波的传播时间,获得超声波纵波与横波的声时比,即超声纵波与横波的波速比,建立弹性应力与超声波纵波与横波声时比之间的定量关系,为利用超声波实时测定螺栓弹性应力提供依据。结果表明,在45钢所承受的轴向弹性应力处于钢的弹性变形范围内时,超声波纵波与横波声时比与弹性应力之间呈线性关系,为σ=-50 249.8 S_l/S_t+90 536.1。通过实际测定应力值对超声波纵波与横波声时-应力模型测定出的应力值进行验证,结果表明,利用超声波纵波与横波测定的应力值与实际应力值之间的最大误差为2.36%,满足工程要求。

Using tensile testing machine and ultrasonic stress detector, axial tensile was carried out on 45 steel of volute bolt of hydropower unit, and the stress value and the corresponding ultrasonic p-wave and s-wave propagation time were measured in the tensile process, so as to obtain the ultrasonic p-wave and s-wave acoustic ratio, i.e., the ultrasonic p-wave and s-wave velocity ratio. The quantitative relationship between elastic stress and ultrasonic p-wave and s-wave acoustic time ratio was established, which provided a basis for real-time determination of bolt elastic stress by ultrasonic wave. The results showed that the axial elastic stress of 45 steel was within the elastic deformation range of the steel, and the relationship between the acoustic time ratio of ultrasonic p-wave and s-wave and the elastic stress was linear, σ=-50 249.8 S_l/S_t+90 536.1. The error between the stress measured by p-wave and s-wave and the actual stress was 2.36%, which meets the engineering requirements.