Bending stresses in sheet metal

Please forgive this simple question, I have extensive experience in finite element analysis of general structure, but I have never analyzed the shape of nonlinear sheet metal. I first need to evaluate the fatigue life of a piece of spring steel that forms a particular shape and then cycles X times around the deformed shape throughout its lifetime. This is new to me.

Are there tips on how to handle this in simulation? Can shell elements handle such problems? I hope so, but if you bend the parts you will be worried. For a while, forget about the cylinder - I would like to get a good first crack in the process of plastically deforming the spring steel piece from the standardized state into the "product" state. Tips?

Figure 1.2.2: Bending - Term and shape ductility of curved sheet metal plays a very important role. When ductility is low, the minimum bending radius is large. Likewise, the biaxial stress state in the curved region also reduces the ductility of the outer fiber. As the plate thickness ratio (w / t) is larger, the state of biaxial stress can be expected. When w / t reaches 8, the biaxial state is reached. Larger w / t ratios reduce the critical strain required for fracture. As a result, the bending radius increases. Since the stress condition along the edge is more biaxial than the central part, cracks occur at the end of the narrow part. Upon receiving a large bending radius, the central part undergoes more biaxial stress conditions, so the wider sheet cracks in the center. To increase the minimum radius, polish or grind the sheet

The outer surface of the curved sheet is called the minimum bending radius. It is usually expressed in thickness t. The following table shows the minimum radius of some materials. Table 1.2.1: Minimum curvature radius material Please bend. To obtain a representation of the minimum bend radius, the true strain of the material during the uniaxial tensile test at break can be equal to the bending strain. Ln (Ao / Af) = ln (1 + e) ​​= ln (1+)

Bending is a common manufacturing method for processing metal plates. Normally it is done with a bending machine, but a vibration bending machine is also used. In this machine, the curved material is bent with respect to a predetermined angle. Linear bending occurs in bending operation, and curved bending occurs in shape manipulation. In order to restore the residual stress of the stamped workpiece, heat treatment is usually carried out. The heat treatment can heat the metal to the recrystallization temperature, which will readjust the particles in the metal. By heat treating the metal, finer crystal grains can be obtained, so that cracks can be reduced and cured. The following describes the process heat treatment of the blade.