Simulation And Experiment Of Cold Extrusion For Deep Hole Of The Caterpillar Parts

The plates of armored tracked vehicle work in poor conditions, which lead to defects in the deep holes of the pin bush and the plate body, and the service life of workpieces are shortened greatly. Therefore, it is urgent to improve the mechanical properties of the deep holes. Nevertheless, traditional processing methods of deep holes can not improve the mechanical properties of deep holes efficiently, making deep hole precision processing still one of challenges in mechanical processing industry. In order to reduce surface roughness of deep holes, remove surface defects and improve surface hardness, it is feasible to perform cold extrusion strengthening processing after mechanical removal processing, such as deep hole driling, boring and reaming. However, the lack of simulation research on deep hole cold-extrusion technology makes it hard to explain the problems in extrusion process and to provide effective guidance during the process. Therefore, a research on deep hole cold extrusion is presented.The effects of process parameters on aperture and surface of the hole were investigated with the combination of simulation and experiments based on the theory of elastic-plastic deformation and material mechanics in this paper. Furthermore, the process of cold extrusion process for deep hole was optimized, which fulfilled the requirements of aperture size and surface quality after extrusion process.First of all, finite element simulating research on hole cold-extrusion processing is performed out. The three-dimensional finite element simulation model of two kinds of workpieces(pin bush of 38 CrSi steel and plate body of 42 CrMo steel) are established, and the results are analyzed. Based on the fitting curves of the pore diameter between the relative extrusion, friction coefficient and propulsion, the influence of parameters on aperture is presented. When the relative compression ratio is 0.79% and the friction coefficient is 0.1, the propulsion of 50000 N and 40000 N are applied to squeeze the deep hole of pin bush and plate body, respectively. And the pore diameter is approach 38 mm.Secondly, experiments about the cold extrusion processing of deep hole have been studied by orthogonal experimental based on the results obtained from the simulation. The experimental results reveal the influence of aperture size with the relative extrusion, friction coefficient and propulsion, and verify the correctness of simulation results.Finally, this thesis analyzes the quality detection of the deep hole in two kinds of workpieces that before and after the cold extrusion, such as surface roughness of deep hole, surface metallography and surface hardness. It is verified that the cold extrusion which had been processed in deep hole could reduce the surface roughness, remove processing surface material defects and improve surface hardness.