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Educational finite element models of static and dynamic strength of machine components

Makaroglou Nikolaos

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Summary

This thesis presents detailed user instructions for the engineering simulation software Ansys and Fusion 360. For this purpose, three example models were used, giving the user information about the different cases considered. Initially, the stress concentration factor (Kt) was recalculated, which is present in the diagrams of Chapter 5.3.6 from the book "Elements of Machines" by the author Christos A. Papadopoulos, 3rd edition, TZIOLA publications. For each diagram from pages 134-139, the figures were created, on which the simulations were made in the Ansys software. For the first curve, by changing the necessary dimensions, 6 points and their stress concentration factor were found. This coefficient was compared to that contained in the book for axis i) with a hemispherical tip spline, ii) with changing cross-sections, iii) with notches and iv) with a hole subjected to tension, bending and torsion. The theoretical and calculated values were found to be close, verifying the correctness of the models. In the second stage, the Fusion 360 software was used, with which 21 and 42 tooth spur gears were designed. A comparison of bending stress and surface pressure was made as the torsional force applied to the small gear varies. The calculated bending stress and surface stress values were verified through the AGMA equations for torque force from 100 to 800 N-m. In the third and final stage of the thesis, the bending stress and surface pressure were again compared, but on 20 and 40 teeth spur gears, the force being constant, with rotating contact slope. A straight line was found on their point of contact, where at all its points there is contact of one set of teeth. Then, 8 points were found on this line and by moving both wheels along the Z axis, the surface pressure at their contact point was calculated for a torque of 400 N-m. As the contact point moves away from the top of the tooth towards the root of the pinion, the surface pressure is reduced. In addition, the bending stress of the pinion and wheel at 8 different points was compared, in which it was observed that as the contact point moved away from the top of the tooth towards the root of the pinion, the bending stress increased. The same happened for the wheel. Therefore, it was concluded that the surface pressure is inversely proportional to the bending stress.

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