November_December_2021_AMP_Digital

FEATURE A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 2 1 4 7 TABLE 1 — RESIDUAL STRESS ANALYSIS TEST RESULTS Characteristics Location Batch A and B after soft gear cutting Batch B after annealing heat treatment SN1 SN2 SN3 SN1 SN2 SN3 Residual stress, MPa A +97 +109 +155 +110 +88 +95 B +112 +135 +119 +90 +103 +85 C +150 +89 +95 +105 +97 +102 D +165 +145 +85 +95 +106 +95 Residual stress, MPa +131 +119.5 +113.5 +100 +98.5 +94.25 Average residual stress, MPa +121.3 +97.5 % drop in tensile residual stress 19.50% Min residual stress, MPa +97 +89 +85 +90 +88 +85 Max residual stress, MPa +165 +145 +155 +110 +106 +102 Within-part variation, MPa +68 +56 +70 +20 +18 +17 Average residual stress within part, MPa +64.6 +18.3 % reduction in variation within the part 71.60% Part-to-part variation, MPa +18 +6 % reduction in variation part-to-part 66.66% same for both batch A and batch B. Apart from this, quench press parameters and quench oil parameters are also kept the same. RESIDUAL STRESS MEASUREMENT AND DISCUSSION Residual stress is measured on the gear set tooth flank at four locations using an x-ray diffraction machine [3] . Locations are shown in Fig. 1. The gears are not sectioned but entire gear and pinions are exposed to machine. The analysis results show the residual stresses are tensile in nature. The stress analysis results are tabulated in Table 1. A graphical analysis shows the benefit of annealing on residual tensile stress, within-part stress variation, and part-to-part variation in stress. Results are shown in Fig. 2. The comparison between batches A and B shows the ten- sile stress variation within part is +64 MPa for batch A, and +18 MPa for batch B. This indicates the annealing heat treatment reduces the within-part stress variation to 71%. Similarly, the part-to-part variation for batch A is +18 MPa whereas batch B after annealing is +6 MPa. This data also shows the annealing process helped to reduce the part- to-part variation to 66.6%. Also, there is a drop in tensile residual stress. Batch A shows tensile residual stress of +121 MPa whereas batch B, post-annealing heat treatment shows +97 MPa. The 19.5% drop in tensile residual stress indicates stress relieving occurred during the annealing heat treatment. HYPOID GEAR PROFILE MEASUREMENT TEST RESULT Both batches of hard gear sets were tested in Klingeln- berg P 65 test equipment and the topography of the tooth profiles were compared by gear group. The observation shows batch B has lower tooth distortion than batch A gear sets. Also, the distortion pattern in batch B is symmet- ric within the part and part to part, whereas distortion in batch A gear sets is on particular segments of the gear tooth; also the distortion pattern is asymmetric. A majority of batch B gear sets meet the AGMA class 8 requirements, 13