bolt elastic modulus,china fasteners: bolt cross-sectional area. After the strength grade and size of the bolt are determined, the pre-tightening force is only related to the bolt elongation, which can eliminate the influence of variable factors such as friction coefficient, contact deformation, and deformation of the connected parts, so the highest control accuracy can be obtained and used as

Therefore, the pre-tightening force range must be determined in the assembly process. China Standard Parts Network prompts to determine the scientific and reasonable pre-tightening torque range based on the comprehensive consideration of the importance of the connected parts, the force condition, the movement mode, the structural characteristics, the thread specifications and grades, the material of the connected parts and the purpose of the connection, etc.; Strictly comply with the torque requirements specified by the process during assembly. Only in this way can the reliability of the threaded connection and the fatigue strength of the connection piece be truly improved.

The pre-tightening force control method of important bolt connection. However, measurement devices (such as micrometers, ultrasonics, etc.) are inconvenient to implement in specific connection structures and affect production rhythms, so they have not been widely used in the automotive industry. Under laboratory conditions, the elongation method is an indispensable method for calibration, calibration and experimental development.

The four assembly methods of threaded connection have their own advantages and disadvantages. When tightening, they must be determined according to the actual connection structure. The requirements of the connected parts, the accuracy requirements of the axial pre-tightening force and the application of the control method must be clarified, and selected through experiments and analysis. The most suitable method.

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