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Simulating Fatigue Cracks Growth in Spiral Bevel Gears Part 7

Tham khảo tài liệu 'simulating fatigue cracks growth in spiral bevel gears part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Figure 5.5 Simplified model 3 ignore both shafts and half of gear rim. A semi-elliptical crack is introduced in the root of the middle tooth in each model. The crack is 0.64 inches long and 0.14 inches deep. A simplified load is applied to the middle tooth over the middle thứd of the tooth length and tooth height. The shape of the traction patch is rectangular and the traction across the patch is constant. The shape and location of the traction patch is different from those described in Section 5.2.1. However the difference is not important because the intent is to analyze differences in SIFs between models after changing one variable and keeping all the rest of the model parameters constant. To achieve consistency between all the models the mesh in the region of the crack and load patch is identical. The SIFs increase on average by 7 8 and 11 with respect to the full model s SIFs for simplification one two and three respectively. In a fatigue growth rate context changes of this magnitude are significant. Recall that the crack growth rate is proportional to Ki raised to a power Equation 3.6 . For AISI 9310 the magnitude of the exponent is approximately 3.4. Consequently seemingly small changes in the SIFs have dramatic effects on the crack growth rate predictions. It is concluded from this study that the full model should be used for all trajectory predictions. To verify that only explicitly modeling three teeth yields accurate results a nine teeth model is analyzed. If the SIFs between the three teeth and nine teeth models are similar then it can be concluded that not all of the nineteen teeth of the pinion need to be modeled. An edge crack is introduced in the three and nine teeth models in the middle of the tooth length in the root of the concave side of the middle tooth. The crack shape is semi-elliptical and is 0.125 inches long and 0.05 inches deep. An effort is made to keep the meshes between the two models identical. The difference in SIF distribution under