The production of gear components includes numerous manufacturing operations which are carried out to ensure proper surface characteristics of components to deal with wear and fatigue. Surface shot peening is one way to increase the compressive residual stresses on the surface and thus ensure better wear and fatigue resistance. An experimental plan for shot peening was conducted to produce samples with varying surface characteristics. Residual stress profile and Barkhausen noise measurements were carried out for the samples. The objective of the study was to evaluate the interactions between the shot peening parameters studied, the residual stress profiles and the Barkhausen noise measurements. A multivariable regression analysis was applied for the task. Some remarkable correlations were found between the shot peening parameters, residual stress profile and Barkhausen noise features. The most important finding was that when the shot peening intensity was high enough, over 0.5 mmA, it dominated the shot peening coverage density parameter and thus no correlations could be gained. On the other hand, if the intensity parameter was lower than the limit of 0.5 mmA, the correlation between residual stress and Barkhausen noise measurements was remarkable. This means that the surface Barkhausen noise measurements could be used for the evaluation of the stress gradient in the shot peening process.

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A bstract-The detection of surface stress in materials is becoming increasingly important in failure analysis. In the case of ferromagnetic steels, the Barkhausen effect provides a practical tool for surface stress evaluation. However, one of the drawbacks of the method has been the lack of an underlying model theory for use in computer simulations of these effects. In recent work a model theory has been suggested and calculations of the effects of stress on the Barkhausen signal amplitude have been made. In this paper results are presented on Barkhausen measurements taken from surface modified materials and x-ray diffraction data from the same specimens. These results show a decrease in Barkhausen signal envelope amplitude with compressive stress in the surface of the material.

The production of gear components includes numerous manufacturing operations, which are carried out to ensure proper surface characteristics. Shot peening is one of the surface finishing processes used for transmission components like gears to improve their fatigue behavior. Shot peening increases the compressive residual stresses on the surface, and the procedure also reduces the amount of retained austenite in the surface layer. In addition, shot peening has an influence on other mechanical properties, such as surface roughness and surface hardness. An experimental design was conducted with varying shot peening process parameters, like coverage density and intensity, to alter the surface layer of 13 transmission gear specimens. The correlation between shot peening parameters, Barkhausen noise (BN) features, and X-ray diffraction residual stress measurement was studied. Linear correlation was found between residual stress and shot peening parameters. The relationship between residual stress and BN root-mean-square was not evident but was revealed by taking the ratio of BN measurements at different frequencies. Additionally, BN features, such as peak position, coercivity, and integral area, were found to have a linear trend with the intensity. Along with the aforementioned measurements, other material characterization measurements were also taken. The shot peening coverage density was observed to have a linear relationship with surface roughness values, while an intensity of over 0.6 mm A was noticed to affect the surface hardness. The results obtained can be used in the determination of suitable shot peening parameters to achieve a surface with desired residual stress and other surface properties.

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