FEA Analysis Of The Piston Structural Strength

As one of the most important parts of the engine, the working condition of the piston is directiy rclated to the cngine rcliability, durability and cmissioni performance. The piston works with complicated heat and stress conditions which produce great stress and strain, especially in the seat of piston pin, and the damage caused by insufficient strength will reduce the intensity of piston. Recent years, with the development of the finite element analysis method, the piston strength calculation is becoming mature. We can obtain the temperature, stress, and strain of the piston and find the dangerous position through the calculation of piston temperature field and stress field, and then improve the piston with purpose.In this paper, we do the experiment of diesel engine piston temperature field measurement and determine the piston’s thermal boundary conditions, according to the previous summary of the empirical formula and experimental data. Test the piston pin seat pressure distribution innovatively, research the pressure distribution on the piston pin seat in the MatLab and complete the piston strength and fatigue calculation. The main contents of this paper include:1. Use the method of hardness plug to measure the piston temperature field, and get the key temperature of the piston surface. Load the heat transfer coefficient factor in the piston top surface according to the factor’s radial variation. Determine the piston’s thermal boundary conditions with the temperature test data.2. The innovative use of pressure-sensitive film to measure the pressure distribution of piston pin seat can help get the pressure data, which provide a new method to study the strength of piston pin seat. Then process and analysis the data in the MatLab, and obtain the fitting formula for strength calculation. 3. Use the finite element analysis software to calculate the temperature and temperature-stress coupling field. According to the temperature experiment result, load the pressure fitting results into the piston pin seat through a Python program, obtain and analyze the distribution of the piston temperature, stress and strain. Complete the piston fatigue analysis.Experimental data and the FEA results show:subjecting to the maximum explosion pressure, the pressure distributes according to the cosine law along the radial direction and according to the law of quadratic parabola along the axial direction at120°within the scope of the piston pin seat’s top surface. The piston strength calculation, whose boundary condition is determined by the test of the temperature and the piston pin seat’s pressure distribution, shows:the piston maximum temperature is within the temperature range allowed by the material, the maximum deformation of the piston will not interference on the liner, the maximum piston stress occurs at the junction of the piston pin edge and the skirt and not exceed the limit of the material strength, the fatigue safety factor shows the piston is safe overall.