Study On The Influence Of Nonmetallic Inclusions On Contact Fatigue Performance Of Gears

As one of the key parts of the transmission system,contact fatigue of gears is a key factor that restricts the performance and reliability of mechanical equipment such as ships,automobiles,wind power and machine tools.Aiming at the contact fatigue failure of gears,the contact fatigue performance of gears has been effectively improved by the improvement of tooth shape design,material smelting and heat treatment.By strictly controlling the size and distribution of inclusions,steel enterprises in Japan,Europe,America and South Korea have improved the purity of steel and greatly improved the anti-fatigue performance of the clean steel.However,the defects of various gear materials represented by nonmetallic inclusions cannot be completely avoided,which often become the source of cracks and further lead to fatigue failure.In addition,the random distribution of nonmetallic inclusions in gears is rarely considered,so it is of great significance to study the influence of distribution characteristics on the contact fatigue performance of gears.In summary,it is necessary to study the mechanism of contact fatigue failure of gears with nonmetallic inclusions.In this paper,based on the finite element technique and multiaxis fatigue theory,the contact fatigue model of gears with nonmetallic inclusions is established.Based on the Monte Carlo method,the random distribution of inclusions was introduced into the model,and the stress-life curve(S-N curve)with different survival rates was drawn,that is,the P-S-N curve.The main research contents of this paper are as follows:(1)The analysis of stress,strain and fatigue life of the gear considering inclusions are carried out.The contact fatigue life model of gear is established and the stress state of subsurface is analyzed.The local stress concentration of inclusions is studied,and its effect on contact fatigue life was evaluated by the multiaxis fatigue criteria of MorrowBrown-Miller.(2)The influence of inclusion properties and distribution characteristics on contact fatigue life of gears is studied.The effects of the size,shape,distribution depth,elastic modulus and multi-inclusion on the stress field and contact fatigue strength of the secondary surface of the gear are considered.(3)The gear contact fatigue P-S-N curve with randomly distributed inclusions is drawn.Monte Carlo method is introduced to consider the influence of random distribution of nonmetallic inclusions on contact fatigue strength of gears.The depth position of minimum life and fatigue life distribution under four loads are calculated.The goodness of fit test is carried out with different distribution functions.Finally,the three-parameter Weibull distribution function is used to draw the contact fatigue P-S-N curve.