Effect of Shot Peening on Pitting Strength of Case-Hardened Steel Roller

Influence of Shot Peening on Surface Durability of Case-Hardened Steel Gears (Influences of Shot Velocity and Shot Diameter)

“…The results of the plasma case-hardened sintered powder metal gears obtained in the past study (5) are also shown in this figure. As in the cases of the case-hardened steel rollers and the plasma case-hardened sintered powder metal rollers shown in the past papers (3), (5) , it can be said from this figure that the shot peening has the lower impact on the surface roughness of case-hardened steel gears, compared with the case of sintered powder metal gears. Figure 2 shows the average hardness distributions of test pinions.…”

“…Therefore, it should still be useful to investigate the influence of shot peening on the fatigue strength of steel gears. In the previous papers (2), (3) , we focused attention on spalling failure (2) due to subsurface cracks and pitting failure (3) due to surface cracks, respectively, and discussed the influence of shot peening on the surface durability of case-hardened steel rollers. As a result, it was clarified that strong shot peening, which increased the hardness and the compressive residual stress near the roller surface, was suitable for increasing in the spalling strength, on the other hand, light shot peening, which did not increase the surface roughness much, was suitable for increasing in pitting strength.…”

Influence of density and nickel content on fatigue strength of powder-forged gears - Comparison with ingot steel and sintered steel -

“…In the calculations of these stresses, a contact point on the roller surface or the tooth surface was chosen as the origin, the axial direction of the roller or the tooth trace direction of the pinion was chosen as the x coordinate, the circumferential direction of the roller or the tooth profile direction of the pinion was chosen as the y coordinate, and the radial direction of the roller or the normal direction to the tooth surface of the pinion was chosen as the z coordinate. In this contact stress analysis, the friction coefficient between the test roller pair and the test gear pair was considered to be 0.035, from previously reported experimental results of the case-hardened steel roller pair (Yoshida et al, 2003), because it was not measured herein. Moreover, the residual stress distribution of the test rollers shown in Fig.3 was considered for calculating the alternating orthogonal shear stress yz, and the surface residual stress of the test pinions shown in Table 4 was considered for calculating the tangential normal stress y.…”

Rolling Contact Fatigue Life of Steel Rollers Treated by Cavitation Peening and Shot Peening

“…Thus, tangential normal stress σ y was considered because it became maximum on the surface (15) . In the calculation of this tangential normal stress on the contact surface,…”

“…As in the case of the carburized steel rollers employed in the past paper (15) , the maximum amplitude [A(σ y / 3 HV)] max of the ratio of tangential normal stress σ y to Vickers hardness HV was calculated by neglecting the effect of mean stress on fatigue and by assuming that the material strength of the test rollers is proportional to their hardness before the RCF tests. In the following paragraph, the RCF life and the surface durability of the test rollers were discussed by [A(σ y / 3 HV)] max (17) .…”