利用拉伸试验机和超声应力检测仪,对水电机组蜗壳螺栓(35CrMo钢)进行轴向拉伸,测定其在拉伸过程中的应力值及其对应的超声横波和纵波传播时间,获得横波与纵波的声时比,建立弹性应力与超声横波与纵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35CrMo钢所承受的轴向弹性应力处于钢的弹性变形范围内时,超声横波与纵波声时比与弹性应力之间呈线性关系。对该模型进行误差分析,结果表明,利用超声横波与纵波测定的应力值与实际应力值之间的误差为0.04%~2.08%,满足工程要求。

The 35CrMo steel of volute bolt of hydropower unit was subjected to axial tensile by using tensile testing machine and ultrasonic stress detector, and the stress value and the corresponding ultrasonic transverse wave and longitudinal wave propagation time were measured in the process of tensile, so as to obtain the sound-hour ratio of ultrasonic transverse wave and longitudinal wave, that is, the wave velocity ratio of ultrasonic longitudinal wave and transverse wave. The quantitative relationship between elastic stress and ultrasonic time ratio of shear wave and longitudinal wave is established to provide a basis for real-time determination of bolt elastic stress by ultrasonic wave. The results show that the axial elastic stress of 35CrMo steel is within the elastic deformation range of steel, and there is a linear relationship between the acoustic time ratio of shear wave to longitudinal wave and the elastic stress.Through the error analysis of the model, the results show that the error between the stress value and the actual stress value measured by ultrasonic shear wave and longitudinal wave is between 0. 04 and 2. 08%, and the error meets the engineering requirements.