Mechanical knowledge question and answer

1. What are the failure modes of mechanical parts?

(1) Overall fracture (2) Excessive residual deformation (3) Surface damage of parts (4) Failure caused by damage to normal working conditions

2. Why do threaded connections often need to be prevented from loosening? What is the essence of anti-looseness? What kinds of anti-loose measures are there?

Generally, the threaded connection can meet the self-locking condition and will not automatically loosen, but under vibration or shock load, or when the temperature changes greatly, the connecting nut may gradually loosen. The main reason for thread loosening is the relative rotation between the thread pairs. Therefore, in the actual design, anti-loose measures must be adopted. The commonly used measures mainly include the following: 1. Friction anti-loose --- keep the thread pair To prevent loosening, such as adding spring washers, double nuts on top; 2. Mechanical anti-loose---stop parts are used to ensure anti-loose, and groove nuts and split pins are often used; 3. Damage Anti-loosening of thread pair --- destroy and change the relationship of thread pair, such as impact method.

3. What is the purpose of tightening in the threaded connection? Cite several control tightening force

The purpose of tightening in the threaded connection is to allow the bolt to generate a pre-tightening force. The purpose of the pre-tightening is to enhance the reliability and tightness of the connection to prevent gaps or relative sliding between the connected parts after being loaded. The effective method to control the tightening force is to measure the torque wrench or the fixed torque wrench, when the required torque is reached, lock it; or use the method of measuring the elongation of the bolt to control the pre-tightening force.