Effect Of Gear Shot Peening Parameters On Surface Intergity

The higher requirements for surface quality of gears etc.loading bearing components.Compared with other surface strengthening technologies,shot peening has the characteristics of significant strengthening effect,convenient implementation,wide adaptability,low energy consumption,etc.Shot peening technology is a mechanical cold working method that continuously impacts the surface of the material with the help of a high-speed moving shots stream,causing the surface of the material to be plastically deformed,the surface material structure is further refined,and the hardness and wear resistance are significantly improved.At the same time,shot peening can also form a residual compressive stress layer on the surface,which is an important strengthening mechanism for improving the fatigue resistance and stress corrosion resistance of engineering materials.However,the current understanding of the mechanism of shot peening is not clear.The relationship between shot peening process parameters and surface roughness,residual stress distribution,and material microstructure properties is not clear.The selection of process parameters is heavily dependent on experience,resulting in poor strengthening process effects,especially restrictions It is used in improving the contact fatigue strength and bending fatigue strength of gears.In order to effectively strengthen the gear surface while taking into account the cost,shot peening technology has become an important research direction in the surface strengthening of high-performance gears.To obtain the influence law between the process parameters and the shot peening effect,the establishment of a simulation model for the prediction of shot peening process parameters and the study of its mechanism have high scientific value and engineering guiding significance.In this thesis,the shot peening process parameters of the processed by the carburizing and quenching machine wind power gear material 18 Cr Ni Mo7-6 are studied.The random multi-shot shot peening Model was eatablished including the actual material properties,such asthe yield strength,initial surface morphology and initial residual stress of different depths.Try to explore the correlation law between shot peening process parameters and surface integrity,and provide theoretical support and technical support for the anti-fatigue design and manufacture of high-performance gears.The main research contents of the thesis are as follows:(1)Carry out shot peening experiments and establish a test characterization system for shot peening surface integrity parameters.Through the shot peening of the wind power gear material,the surface topography measurement,residual stress detection,hardness characterization,microstructure test and other characterization methods are established to establish a characterization system for the correlation between shot peening and surface integrity.(2)Establish real material properties-random multi-shots peening model.Based on the results of the experimental characterization,the shot peening finite element model was modeled.During the modeling process,for the machining process of wind power heavy-duty gear materials,the gradient characteristics of mechanical properties such as hardness distribution and residual stress caused by carburizing and hardening were considered.A real material property-random multi-shot peening model including the yield strength,initial surface topography and initial residual stress at different depths is established.The influence of the shot peening process parameters on the distribution of residual compressive stress and surface morphology is analyzed,and the model results are compared with the test results.The residual stress error is no more than 18%,and the surface roughness parameter change trend is almost the same,the correctness and reliability of the pill model.(3)Investigate the impact of shot peening coverage on surface integrity parameters.Based on the results of experimental and simulation analysis,the influence of shot peening coverage on surface integrity parameters such as residual stress,surface morphology,hardness,equivalent plastic strain,metallographic structure,and grain size is explored.The results show that the axial and tangential residual stress distribution of the specimens tends to be the same with shot peening.As the coverage increases from100% to 400%,the surface residual compressive stress linearly increases from-628 MPa to-705 MPa.The ratio of the thickness affected by the residual compressive stress by shot peening to the depth at which the maximum residual compressive stress appears is a fixed value,generally in the range of 3.6 to 4.3.In addition,shot peening will slightly increase the surface and near-surface hardness from 690 HV to 740 HV.As the coverage increases,the surface roughness parameters Sa,Sq,S5 z and Sku gradually decrease.(4)Analyze the influence of shot peening machine process parameters on shot peening intensity.Through a large number of shot peening process parameter tests and combined with random forest algorithm,the influence of shot peening machine process parameters on shot peening intensity is analyzed.The results show that the shot peening intensity increases linearly with the increase of the shot pressure,and decreases inversely with the increase of the shot flow rate.With the increase of the peening distance,the shot peening intensity presents a trend of first increasing and then decreasing.The influence of process parameters on shot peening intensity is shot diameter(36.73%),shot peening air pressure(32.07%),shot flow rate(23.11%)and peening distance(8.1%).(5)Explore the impact of shot peening intensity on surface integrity parameters.The shot peening intensity ranging from 0.15 mm A to 0.55 mm A with experimental and simulation were carried out.The results show that with the increase of the shot peening intensity,the surface residual stress decreases linearly,and the maximum residual stress and its depth and the depth of the residual stress influence layer all show a linear increasing trend.And with the increase of shot peening intensity,the surface roughness Sa and Sq linearly increase to 1.64 μm and 2.1 μm,which were 0.62 μm and 0.78 μm without shot peening.At the same time,there is a linear change trend between the surface roughness Sq and the surface hardness HV.To a certain extent,the roughness parameter Sq can be used to predict the change trend of the surface hardness with shot peening.