Geometry detection In order to understand the dimension of the broken part of the part, the semi-finished product after hot bending was tested for dimensions. The test result showed that the diameter of the fractured part of the fracture meets the requirement of not less than 20.5mm; the radius of the inner radius of the fracture part is in the range of R22mm20mm. Inside; the inner circle of the fracture site has different degrees of protrusion wrinkles. Causes of Fracture Analysis The radiator torsion bar is an elastic part. After hardening and tempering, the structure should be a better elastic troostite. The general hardness requirement is in the range of 375495 HB. From the test results, there are no problems with the chemical composition, hardness, and microstructure of the material. Furthermore, the metallographic analysis shows no quenching defects such as coarse grains, indicating that the quenching and tempering heat treatment process is normal. The macro-fracture shows that the fatigue zone of the fatigue arc is small and the rapid expansion zone is large, which means that the part is subject to a large alternating load and break. From the assembly of the component, it can be known that under the locked state of the fixing mechanism, the part is subjected to static torsion, and this static torsion does not cause the part to break quickly (the torsion angle is within its elastic range). However, statistics of the fracture of the part show that the part has 5 fracture records in 2 years, which indicates that this alcohol solution etched alternating load will be generated and existed in the use of some vehicles. It can be seen that some vehicles have improper use of locking devices. The crack originated on the surface of the part, there was no decarburization on both sides of the crack, and no problems such as oxidation were found, indicating that the crack was generated during use. The surface of the component was found to have a significant decarburization layer, which not only reduced the surface fatigue strength of the material, but also caused tensile stress on the surface of the component due to the difference in carbon content between the surface and the inside, so that the surface of the component under a large external force. Cracks develop. According to the data, taking 60Si2Mn as an example, even a very slight decarburization layer (0.125mm) will cause the fatigue strength to drastically drop from 570N/mm to 350N/mm. The decarburized layer of the fractured part is 0.10mm, which is already close to 0.125mm. Therefore, the decarburization of the surface of the part is one of the causes of cracks. Wenzhou Huaze Machinery Co.,Ltd , https://www.multihzs.com
Erosion alternating loads are generated and present in the use of some vehicles