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Abstract. The gear contact stress problem has been a great point of interest for many years, but still an extensive research is required to understand the various parameters affecting this stress. Among such parameters, helix angle is one which has played a crucial role in variation of contact stress. Numerous studies have been carried out on spur gear for contact stress variation. Hence, the present work is an attempt to study the contact stresses among the helical gear pairs, under static conditions, by using a 3D finite element method. The helical gear pairs on which the analysis is carried are 0, 5, 15, 25 degree helical gear sets. The Lagrange multiplier algorithm has been used between the contacting pairs to determine the stresses. The helical gear contact stress is evaluated using FE model and results have also been found at different coefficient of friction, varying from 0.0 to 0.3. The FE results have been further compared with the analytical calculations. The analytical calculations are based upon Hertz and AGMA equations, which are modified to include helix angle. The commercial finite element software was used in the study and it was shown that this approach can be applied to gear design efficiently. The contact stress results have shown a decreasing trend, with increase in helix angle.

Misalignment between pinions to wheel gears induces bending stresses continued influences the fatigue life of the spur gear system. Lack of research projected to the issues causes uncertain in their useful lifetime estimation. In this paper, the bending fatigue life of the spur gear in axial misalignments condition was predicted. A three teeth FEM model of spur gear with the same geometrical profiles was constructed according to ISO 6336-1:2006. The gear was subjected with five misalignment from 0.1mm to 0. 5mm at different torque loadings from 50Nm to 300 Nm. Exerted with quasi-static approach; the stress variant was analysed to stress life model as well as the damage accumulation model for fatigue life prediction in ANSYS V19. Results showed that the application of axial misalignment had a small impact significantly reduce the life of the gear, in percentage difference between 0.1 - 2%. This suggested that the bending fatigue life did not reflect to the existence of axial misalignments as the effect is very small that it is possible to be neglected.

This paper evaluates the effects of yawing misalignment contact on the tooth root bending stress values of spur gear pair during the gear meshing cycle. A model basedon involute 3DparametricCAD geometry, of spur gear design ISO 6336:2006 is analyzed with worst loading position when yawing misalignment (Y) exist due to assembly error (AE) between 0.20 to 0.40 in degree scale values. Finite-element method (FEM) with dynamics module from ANSYS is used in order to calculate the tooth root bending stress (TRBS) at the critical region with respect to face width of pinion and gear section. A comparison is made between standard high point single tooth contactmodels (HPSTC) to this model as verification. Further analysis showeda good agreement that these methodologies are adequate in order to conduct a real time dynamics simulation to define the value of TRBS in Y condition due to AE. Yawingmisalignment influence factor (YMIF) was introduced as an indication of TRBS values in consideration of Y due to AEshows a higher result for pinion, give a good justification that the pinion is weaker compared to the gear in Y condition.

Gear offsets mesh in axial misalignment always leads to unevenness of load transferred contributing the impact of stress value and distribution along important critical path of the tooth root. Its happening due to overpress fitting when the gear is mounted onto the shaft as an interference hub fit. Current design methodology based on empirical model provide solution by approximation load factor fail to attributes in detailed regarding this phenomenon This paper determined to focus on this phenomenon in term of methodology to the stress distribution at the critical contact region of the tooth root of the gears. Pair of spur gear with real geometrical construction and condition was constructed with offset parameter. A moving load quasi-static model with a numerical FEM solution using ANSYS is presented with modification in loading variation. For verification, the stress value at the critical path of the tooth root is compared between standard high point single tooth contacts (HPSTC) loading to moving load model. As the result, a numerical FEM methodology to calculate the stress distribution of the gear tooth root in offset axial misalignment with moving load model approach is determined. The proposed method is also found reliable as an alternative solution to define an accurate load factor calculation compared to the approximation provided by the standard empirical procedure.