The elastic deformation stage of the hydraulic shearing machine in the shearing plate

There are several stages in the bar shearing of the hydraulic shearing machine. Do you know it? It doesn't matter if you don't know. Today, the world press machine will explain to you. I hope everyone can be familiar with hydraulic What happened to the shears.

Hydraulic shears generally go through several stages such as elastic deformation, plastic deformation, crack generation and slip expansion, and fracture separation. On the fracture surface after shearing, there are obvious fracture features such as rounded corners, bright zones, and unstable fracture zones.

The elastic deformation stage of the hydraulic shearing machine in the shearing plate refers to the deformation of the bar material under the action of the force after the movable shearing blade contacts the bar material. The deformation at this stage is elastic deformation. At this time, the force has not reached the The yield limit of the material. As the shear force increases, when the stress exceeds the yield limit of the material, the material begins to enter the plastic deformation stage.

Since the shearing speed and force at the dynamic and static shearing edges are different, the plastic deformation near the section of the bar shearing plate is also different, and stress and strain concentration will occur at the tip of the blade. The material here is first Yield occurs, forming a shear plate slump. When shearing the plate, the material at the moving cutting edge is bent downward, and the material at the static cutting edge is raised upward. The larger the axial clearance is, the larger the bending moment is, the more serious the upturning of the bar is, and the larger the collapse angle is.

The use of sleeve shears and keeping the gap value small can greatly limit the upturning of the bar and the bending of the billet, while the use of clamping shears basically eliminates the rotational freedom of the material to be sheared and completely limits the bar. The upturn of the material and the bending of the blank. In this way, the shear stress at the shear plate section does not change, while the compressive stress at the shear plate section is reduced, the plastic deformation is reduced, and the fillet at the billet and bar is also reduced.

The moving shearing edge continues to move downward, causing the compressive stress to increase sharply, the deformation of the material in this area along the moving direction of the shearing edge intensifies, the lattice slips seriously, and cracks begin to form. When the cracks formed at the upper and lower shearing edges converge, the bar breaks and separates. When the hydraulic shearing machine clamps the shearing plate, the material in the sheared area is in a state of multi-directional compression, and the crack basically expands along a straight line, which improves the section quality of the blank.

When the hydraulic shearing machine shears the plate, the force at each stage is different, so that the blank section after shearing has different shearing characteristic zones. Generally, the shearing section is mainly rounded area, bright zone and unstable fracture surface. The fillet area is formed by the combined action of the shear force acting on the bar and the bending moment formed by the shear force to cause the plastic deformation of the material attached to the edge under the action of the force.

Especially when the axial clearance between the dynamic and static shearing blades is large or the shearing speed is low, the rounded corner feature is very obvious. When the moving shearing edge cuts the material, when the tensile limit of the material is exceeded due to the plastic deformation and bending moment, the unstable fracture will occur and the unstable fracture surface will be formed.

According to the analysis of the hydraulic shearing machine, when the shearing plate is fully clamped in the radial direction, under the action of the clamping force, the phenomenon of bending and upturning is eliminated to a certain extent, so that the material in the shearing plate area is in a state of multi-directional compression, limiting shearing. The plastic deformation of the material in the plate area, especially at the cutting edge, reduces the appearance of the fillet area and the unstable fracture surface, and improves the quality of the section.