| Parts represented by gears,bearings,crankshafts,etc.are often equivalent to cylinders in the process of engineering analysis and design,and their service process is essentially a cyclic rolling-slip contact process between cylinders.Under the action of the surface roughness of the parts,contact stress concentration occurs on the near-surface and sub-surface of the material,which induces fatigue damage,and finally produces contact fatigue failure forms such as micro-pitting and pitting corrosion.Therefore,it is of great benefit to establish a correlation model between surface roughness and contact fatigue strength of cylindrical parts to guide their anti-fatigue design and manufacture.Although there are numerous contact fatigue strength studies considering surface roughness,most of the existing works are based on a limited number of measured or reconstructed roughness samples,without systematic modeling of surface roughness,and often only focus on a few Roughness parameters are common,and the conclusions obtained are often influenced by many random factors and other roughness parameters,which makes the intrinsic relationship between roughness parameters and contact fatigue unclear.Therefore,how to effectively carry out roughness modeling to clarify the correlation between different roughness parameters and contact fatigue performance parameters has a positive effect on promoting the fine design and accurate creation of part surface roughness.In this paper,cylindrical parts are taken as the research object,according to different combinations of curvature radius,load and roughness parameters,a large number of random samples of roughness are obtained by the rough surface reconstruction method.The analysis method discusses the influence of the roughness parameters on the contact fatigue strength,and provides a reference for the design and manufacture of the surface roughness of the parts.The main research work of this paper is as follows:(1)Based on the FFT method,the surface roughness reconstruction of the part is carried out,and the measured surface roughness data is used to test the reconstruction method to solve the geometric modeling problem of the subsequent rough surface contact fatigue analysis.Based on the elastic half-space pressure-displacement relationship,the numerical model of rough surface is used to carry out contact calculation and analysis,and the influence of roughness parameters on surface contact pressure,near-surface and sub-surface contact stress distribution is studied.(2)Based on the contact stress field obtained by the contact analysis,the subsurface crack initiation life calculation is carried out based on the critical plane method and the multiaxial fatigue criterion,and the validity of the crack initiation life calculation method is verified by the contact fatigue test.Through the calculation and analysis of a large number of cases,the influence of the roughness parameters on the crack initiation life was studied by means of the correlation analysis method,and the influence strength of different roughness parameters on the crack initiation life was discussed.Spacing parameter,and finally the roughness blend parameter.(3)Based on the contact pressure distribution obtained by the contact analysis,a subsurface crack growth calculation model of rough surface was established based on the extended finite element method and fracture mechanics theory,and the crack growth calculation method was verified by the experimental data reported in the literature.By calculating the crack growth path and crack growth life of samples with different roughness,the dispersion degree of crack growth under different roughness parameters is analyzed.It is found that within a certain range,the roughness is increased,the load is decreased,and the curvature radius is increased Both will increase the dispersion of crack growth,and the crack growth life is more significant than the crack growth path dispersion,and they are more obviously affected by the roughness amplitude parameter. |
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