At present, the torque value of bolt fastening is selected with reference to the design manual according to the specification and material of the bolt, without considering the material of the fastened fittings. This installation method is quite crude. Different materials of the connected parts will lead to differences in the torque-pretension conversion, affecting the safety of the tightened connection. In our opinion, to ensure the quality of tightening needs to further clarify the relationship between the connection of parts of different materials and torque stability.

This project is based on the total assembly process of rolling stock common several material component connection combinations, through the production of test pieces to simulate the vehicle assembly, operation state, to obtain the law of axial force transformation, and measure the axial force attenuation mechanism under different vibration, temperature alternation, rest time and installation gap tooling, and ultimately to formulate the principle of torque compensation and tightening torque, in order to improve the reliability of the connection on the basis of the bolts and components without damaging. The principle of torque compensation and tightening torque are finally formulated to improve the reliability of connection without damaging the bolts and components.

Material and Torque Stability Relationship Research Setup and Selected Test Results

Test analysis shows that the bolt connection structure with different materials of connected parts will show different axial force transformation when the same tightening torque is applied; at the same time, the bolt connection structure with different materials of connected parts will lead to different axial force attenuation laws under the same working conditions. Therefore, bolt connection should not only refer to the design manual to select according to the specification and material of the bolt, but also need to consider the material of the connected parts.

In fact, the traditional selection, assembly standards due to the development of standards at the time of the theory, technology backward, the standard tightening strategy provided by the standard, tightening the value of the rough, resulting in fasteners in different equipment on the connection effect is unpredictable, simply in accordance with the standard provisions of the tightening will lead to the reliability of major equipment in doubt.