In sheet metal processing, stretching is a common forming process, widely used in the manufacturing of parts in industries such as automobiles, aviation, and home appliances. However, during the stretching process, materials are prone to cracks and even fractures, seriously affecting product quality and production efficiency. Therefore, how to effectively prevent fractures during the sheet metal stretching process is a problem that engineering and technical personnel must pay close attention to.



I. Reasonable selection of materials and thickness



The type and thickness of materials directly affect their stretching properties. Different materials have different plasticity and strength, such as low-carbon steel, aluminum alloy, and stainless steel have different stretching properties. Appropriate materials should be selected according to the complexity of the part shape and the stretching depth. At the same time, too thin material thickness is prone to tearing, and too thick thickness will increase deformation resistance, causing local stress concentration and fracture. Therefore, the reasonable selection of material grade and thickness is the first step to avoid fracture.



II. Optimizing mold design



Mold design is crucial for stretching quality. Too small of a radius of the die corner can cause material flow obstruction, increase tensile stress, and easily cause cracks; too small of a radius of the punch corner can cause local stretching deformation to be剧烈, leading to fracture. Therefore, when designing molds, it is necessary to reasonably design the mold corner radius according to the material properties and part shape, so that the material can flow uniformly during the stretching process and reduce stress concentration.



III. Controlling stretching speed and lubrication conditions



Excessive stretching speed will not allow the material to deform plastically in time, resulting in greater internal stress, which can lead to fracture. Appropriately reducing the stretching speed can help improve the ductility performance of the material. In addition, good lubrication conditions can reduce the friction resistance between the material and the mold, making it easier for the material to flow and reduce the risk of fracture. Special stretching oil or lubricant is usually used for coating treatment to improve forming performance.



IV. Adopting pre-forming and multi-pass stretching process



For parts with complex shapes or large stretching depths, pre-forming or multi-pass stretching can be adopted. By gradually forming through multiple stretching, it can effectively reduce the amount of deformation per time, reduce material stress concentration, and thus avoid fracture. At the same time, annealing treatment can be carried out in the intermediate process to restore the plasticity of the material.



V. Strengthen process control and detection



In actual production, it is necessary to strengthen the monitoring of process parameters such as pressure, speed, and lubrication status, and regularly check the wear condition of the mold. In addition, by using finite element simulation technology to simulate and analyze the stretching process, we can predict the potential fracture risks in advance and optimize the process scheme.



Conclusion



The reasons for fracture in sheet metal stretching process are various, involving materials, molds, processes, and many other aspects. Only by scientifically selecting materials, optimizing mold design, reasonably controlling process parameters, and adopting advanced simulation analysis methods can we effectively avoid the occurrence of fracture problems and improve product quality and production efficiency. With the development of intelligent manufacturing and advanced forming technology, sheet metal stretching process will continue to move towards higher precision and higher quality.