材料热衰退下的连杆衬套刚强度特性分析

In order to study the influence of the performance decay of bushing materials at high temperature on bushing rigidity and strength and provide a basis for the design of suppressing bushing failure, the stress-strain mechanical properties of typical tin bronze (QSn7-0.2) and copper-nickel alloy (CuNi6Sn6) at different high temperatures were tested, and the radial deformation, equivalent stress and interference contact pressure of a diesel engine connecting rod bushing of the two materials in assembled state were calculated with considering the material thermal decay characteristics. The results showed that the elastic modulus, specified non-proportional extension strengths and tensile strengths of both materials decreased with increased temperature. The mechanical properties of QSn7-0.2 declined sharply at 200~250 ℃, while those of CuNi6Sn6 decreased slightly obvious at 150~200 ℃, but the values were still higher than or close to those of QSn7-0.2 at the same high temperatures. In addition, the simulation results showed that the radial deformation of QSn7-0.2 bushing was slightly larger than that of CuNi6Sn6, and the out-of-roundness was more serious. The equivalent stress of QSn7-0.2 bushing was small on the whole, and when temperature reached 300 ℃, plastic deformation occurred in the area of the busing where the interference contact pressure was the largest, resulting in a slightly lower interference contact pressure in the region. If the deformation continued to develop, the bushing was more prone to loosen or rotate than CuNi6Sn6. It can be concluded that the material thermal decay is an important cause of bushing failure, and the bushing of CuNi6Sn6 has better mechanical properties at high temperature and high load, and a higher resistance to failure.