There are two kinds of fastener torque: static torque and dynamic torque. Static torque: the torque required to continue rotating a fastener in the tightening direction after it has been fixed. The torque was measured after loading. Dynamic torque: the maximum peak value measured when the fastener is reattached. Both torque wrench and power tool can apply dynamic torque, and dynamic torque cannot be measured after fastening. The torque value obtained by on-line measurement during dynamic torque loading.

    The testing torques of the two kinds of torques are the same. There are three testing methods for the torque of fasteners shared by Zhonggu standard parts network: tightening method (tightening method), marking method (marking method) and loosening method.

    1. Tightening method

    The principle of tightening method (additional tightening method): the torque wrench of tightening method (tightening method) can steadily exert force to increase the torque gradually (avoid impact). When the nut or bolt starts to rotate slightly, its instantaneous torque value is the maximum (due to overcoming static friction force). If it continues to rotate, the torque value will fall back to a transient stable state. At this time, the torque value is the torque obtained from inspection.

    The advantages of tightening method (additional tightening method): the operation is simple, only skilled and experienced.

    The disadvantages of tightening method (additional tightening method): A has the possibility of secondary tightening; B is difficult to determine when the bolt starts to start, and there are subjective factors; C when the bolt is started, the actual torque value should be about the torque value during installation, so the test value is generally too large.

    Static torque: this method is used to test the residual torque, and is suitable for the inspection of tightening quality at assembly site.

    2. Marking (marking)

    The principle of marking method (marking method): before inspection, mark a line on the head of the bolt or nut to be inspected and the connected body to confirm the original position of each other. Then loosen the bolt or nut a little, and tighten the bolt or nut to the original position with a torque wrench (the line should be aligned at the line). At this time, the maximum torque value multiplied by 0.9 ~ 1.1 is the torque obtained by inspection.

    The advantages of marking method (marking method): the technical level is not high, the operation is cumbersome, and it is not suitable for fasteners with locking function

    The disadvantage of tightening method (tightening method): compared with tightening method (tightening method), it is more accurate.

    Dynamic torque: the torque given by the designer from the design point of view is the dynamic torque, so it is recommended to use this method when disassembling the vehicle.

    3. Loosening method

    Principle of loosening method: slowly apply torque to the tested bolt or nut with a torque wrench to make it loose, read the instantaneous torque value at the beginning of rotation, and multiply it by a coefficient: 1.1 ~ 1.2 according to the test and experience, which is the inspection torque value.

    The advantages of loosening method are as follows: easy to operate, but skilled and experienced;

    Disadvantage of loosening method: the torque is too small.