Analysis of the problems in the cold roll forming process of acoustic tubes
2023-07-20
The cold bending forming process of acoustic tubes is known as an "art", and its products are widely used in various fields. At present, scholars have conducted in-depth theoretical research on it, and some researchers have conducted computer simulations of the forming process and achieved certain results. However, the cold bending and forming process of acoustic tubes is a very complex process, and there are still many problems that need to be solved in the design and production process, which are often discovered during the debugging and production process. Taking the forming of wide cross-section thin plates as an example, if the design is not reasonable, deformation defects such as edge waves, pocket waves, longitudinal bending, corner wrinkles, cracks, and twisting may occur during the debugging process.
Redesigning and processing rolls after problems arise will inevitably result in a significant waste of human and material resources. If we can understand the mechanism of these defects and try to avoid them during the design process, or make reasonable improvements to the roller after the defects appear, in order to reduce or even eliminate these defects, we can still achieve the expected goals of roller design.
The following is a brief analysis of the reasons for the problems encountered in the actual operation of cold bending forming of acoustic tubes.
1. The generation of bag shaped waves is mainly due to the transverse tensile stress and transverse strain generated during the bending process of the plate, while the strain of the plate along the thickness direction is relatively small. According to the Poisson relationship of material deformation, shrinkage deformation will inevitably occur along the longitudinal direction in areas with concentrated deformation. In this experiment, this phenomenon mainly occurs at the four deformation corners, so the longitudinally contracted part applies compressive force to the middle plate, and some areas experience instability under the force, resulting in bag shaped bulges, which are commonly referred to as bag shaped waves. Bag shaped waves are mainly elastic deformation.
2. Edge waves (hereinafter referred to as edge waves) are a more common defect than pocket waves, and their generation is mainly a combination of two effects: the first is the same mechanism as the front pocket wave, which is due to the material in the curved section being subjected to transverse tensile stress, resulting in transverse tensile strain. When the strain in the thickness direction is not large, longitudinal shrinkage occurs according to the Poisson relationship, while the edge part is subjected to compressive stress, resulting in edge waves; The second type is that the material at the edge is first stretched and sheared to become longer under external forces, and then compressed and sheared again to produce plastic deformation and cause edge waves. These two effects overlap with each other, forming edge waves.
3. There are many reasons for longitudinal bending, one of which is that the edges of the section are subjected to tension when bending the side, attempting to elongate the entire section along the longitudinal direction. However, the tension is insufficient to elongate the entire rigid section, resulting in upward or downward bending at the front end of the rolled piece.
Analysis and resolution:
The previous pass and the subsequent pass have a greater impact on the generation of pocket waves than the middle pass, especially the subsequent pass. The occurrence of pocket shaped waves can be eliminated by using more forming passes. The width of the section edge has a certain impact on the bag shaped wave, and the design can refer to the relationship F<250t2/(W-88t). Thin plates are more prone to pocket shaped waves than thick plates. Bag shaped waves can be slowed down by applying tension to the sheet material.
2. Edge waves may occur in each pass, with the previous pass facing edge waves