| In recent years,with the development towards larger power and heavier load,the maximum explosion pressure of diesel generator is increasing,as the main part of bearing the load,the upper side of piston pin hole is easy to fatigue cracking.Therefore,the reliability of piston pin boss appears to be particularly important.Insert copper bush at piston pin boss solves the issues discussed above,but the copper bush and the piston is the two part of separation,it is easy to lead to cooper bush shedding under heat load and mechanical load.And the cost of copper bush accounts for about a quarter of the total cost of piston,higher costs.In this paper,the influences of aluminum matrix ceramic fiber composite on the piston pin were studied.This paper based on one Material Research Center measures the properties of piston material,and thermal boundary conditions of piston were obtained by temperature field tests.And nine groups of orthogonal tests and a comparison scheme of inserted copper bushing were designed by using orthogonal test L9(34)of three factors,including pin boss profile,clearance between piston pin and pin hole,the thickness of the reinforcement(aluminum matrix ceramic fiber composite).The optimal combination of the orthogonal test was obtained by the simulation of the piston by workbench,and the reliability of piston with reinforcement was verified through fatigue analysis of the optimal combination and the comparison scheme.The major research contents and conclusions are as follows:(1)The material properties and temperature field were tested with the technicians of Material Research Center.The material properties including the tensile strength,linear expansion coefficient and other performance parameters.And the temperature field of piston was measured by the hardness plug method under rated working condition to get the average temperature of different parts of piston.(2)Temperature field was calculated by setting thermal boundary conditions in Ansys-workbench.The deviation between the simulation and measured mean values of temperature is less than 5% by comparison,which shows that the thermal boundary conditions are in good agreement with the real boundary conditions,providing a good foundation for further analysis.(3)Thermal load,mechanical load and coupling analysis were carried out for 9 groups of experiments and contrast tests designed by orthogonal table.Compared to 10 th test,maximum coupling deformation of nine groups of experiments decrease in varying degrees,Among them,the deformation of No.6 is 317.98μm,reduced by 3.6%,which will play a protective role on the lubricating oil film.(4)According to the range method the optimal combination is the piston pin hole which the pin hole line is NO.2,the clearance is 0.015 mm,the thickness of the reinforcement is 12 mm.Then the optimal combination was modeling analyzed.It is shown that the maximum coupling stress was reduced by 28.8% compared with the scheme of inserted copper bushing,and it is far below the stress limit of the composite material,which meets the structural strength requirements of the piston.The equivalent stresses and the first principal stresses are simulated and analyzed at the throat of the combustion chamber,the results show that the combustion chamber throat area should be much smaller than the matrix material of piston stress limit of 89 MPa,therefore,fatigue cracks will not occur at the throat of the combustion chamber.(5)By using the Fatigue Tool module,the fatigue life,damage and safety factor of the optimal combination and tenth comparison scheme were analyzed and calculated through Fatigue Tool module.The fatigue life of the piston was reduced to 56.3% by using reinforcement,but it still met the maximum requirements for continuous operation and practical engineering needs of engine,fatigue failure would not occur,which verified the reliability of reinforcement of piston. |
