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In this study, the analysis and characterization of the failure that occurred during the torsional fatigue test of the flange yoke unit part of the cardan shaft used in heavy commercial vehicles were carried out. In order to determine the root cause of the failure according to the production, structure, property and performance relationship in materials science, chemical analysis of the steel raw material used in the production of flange yoke, hardness measurement, grain size analysis, decarburization measurement, inclusion analysis and raw material characterization by scanning electron microscopy (SEM) were carried out. As a result of the studies, it was determined that the values obtained for 41Cr4 steel raw material were conformant according to the TS EN ISO 683-2 standard, but in the SEM examination and EDS analysis, elongated MnS inclusions in the microstructure and cracks were detected at the interface of the metal matrix and MnS inclusions. In this context, as a result of the characterization of the flange yoke unit part, it was determined that the MnS ratio was 2-4 µm x 898-1.181 µm according to the ASTM E45 standard, at the same level as the raw material and equivalent to the A-type value of 3.0-3.5. It was determined that MnS inclusion formations in the subsurface region formed crack propagation zones. [ABSTRACT FROM AUTHOR]

Rubber is one of the most important materials of modern industry and have a wide range of usage owing to a number of superior properties. In this study, the mechanical behaviour of the metal-rubber combination pulley part transferring motion in the engine through the timing belt was examined by the finite element method, confirmed experimentally, and optimized. Uniaxial tension and pure shear tests were carried out physically to develop a hyperelastic material model. 3 parameter Mooney-Rivlin hyperelastic material constants were calculated by using force-elongation values obtained from uniaxial tension and, pure shear tests. Afterwards, pulley geometry was modelled, and displacements, stresses, reaction moments were examined under various torsional loadings. To confirm the accuracy of the pulley analysis, a servomotor driven pulley torsion testing machine was designed and manufactured. Then, torque and angle values were measured by testing the pulley parts at the same torsional angles. By this study, it was proven that mechanical behaviour of pulley can be expressed numerically. After validation of the material model and the results obtained using analysis method, the pulley geometry was further improved the stress levels on the rubber material were reduced 28% under the same loading conditions by using optimization tools. [ABSTRACT FROM AUTHOR]