The first stage: the elastic deformation stage
When the cutting edge starts to contact the material, the material produces compression, stretching and bending deformation. The larger the cutting edge gap, the more serious the bending. The material stress does not exceed the elastic limit.
The second stage: plastic deformation stage
When the upper shearing edge continues to drop, plastic deformation begins to occur when the material stress reaches the yield strength. At the same time, the cutting edge of the cutting edge also begins to press against the material, the material hardening in the deformation zone increases, and the shear deformation resistance increases until the material near the edge of the cutting edge appears microcracks due to tensile stress, and the plastic deformation stage ends.
The third stage: cracking and separation stage
The upper and lower micro-cracks have been formed. As the upper shearing edge continues to press, the cracks continue to expand into the material along the direction of the maximum shear stress. When the shear cracks generated by the upper and lower cutting edges overlap, the material is finally pulled apart and separated.