Study On V-shaped Bending Of The Plate Of High Strength Low Alloy Steel By Technology And Numerical Simulation Analysis

Bending parts of high strength low alloy steel are important steel structure of crane. But for the medium and heavy plate of these bending products, several defects including the cracking, spring-back and other defects appear more easily during deformation process than that of thin plates. In this paper, the V-shaped bending process of the three selected high strength low alloy steel plates of Weldox960, Hg785, Hg70were studied. The effects of thickness t, punch round radius r and friction factors μ on the defects spotted during the v-shaped bending process were investigated by tests and finite element numerical simulation methods (FEM). By analyzing the variation regularities, the V bending forming process was optimized.The result shows that the crack and spring-back trends of Weldox960steel are maximum, and that of Hg70steel is minimum, with the same thickness of6-10mm. For the same kind of steel, the cracking situation is alleviated with the decrease of t and the increase of r. Moreover, the firming angle a shows relatively complicated relationships with the process parameters. It shows a direct proportional to r, but an inversely proportional to t when r is10mm or15mm. When r is25mm, it possesses a close relationship with the un-deformed area of plates and the reduction of the process.In addition, there is a strong friction between the outer surface of the plate and the corresponding part of die, resulting in a bad effect on the appearance quality of final products and the service life of the die. The FEM analysis indicates that the maximum tension stress of outside surface of the plate can be reduced by increasing r or decreasing t, while, it is completely contrary for spring-back trend. The spring-back trend shows a direct proportional to r and μ, and an inversely proportional to thet. The V-shaped bending process can be optimized by placing a relatively soft metal mat on the die. Soft metal mat can reduce the surface friction between plate and die, resulting in the decrease of deformation un-homogeneity and the crack trend. However, it can also make the spring-back trend of plate increase. In addition, soft metal mat reduces the intense friction on the surface of the work-piece, which can promote the product surface quality and extend the work life of the die.