Because of the inhomogeneity, deterioration and defects of the welded metal materials, there are three basic assumptions in materials science; The continuity hypothesis, uniformity hypothesis and isotropy hypothesis are not satisfied, which requires the application of fracture mechanics theory. The task of fracture mechanics is to use linear elastic fracture mechanics and elastic-plastic fracture mechanics to solve the crack problem of components based on the fact that there are macro microcracks in the components. Namely, the crack size, working stress and the ability of materials to resist cracks (that is, the crack tip opening displacement CTOD fracture toughness value) in the component are quantitatively linked, and the safety and life test analysis and evaluation are carried out for the components containing microcracks and joints with poor quality tissue.

Function of full-automatic damper and plugging of internal pressure of damper
The basic functions of the fully automatic damper are as follows:
When vehicles and personnel pass by under full automatic control. Automatic roll over, vehicle or personnel will automatically close after passing by, without manual opening, convenient and applicable.
The electrical and mechanical double locking is completed between the two air doors, which completely prevents the two doors from turning over, and it is safe and secure.
It has the function of manual control, and can manually control the opening and closing of the damper by using the remote control or manual button.
Each air door adopts a reverse air design, which ensures that the air door can be opened and closed manually in case of power failure in the mine.
It has the function of emergency unlocking. Under special circumstances, the locking of two sets of air doors can be unlocked, so that both sets of air doors are locked in the open state.