دانلود رایگان مقاله تحلیل شکست یک نیمه محور ماشین مسابقه فرمول SAE

Abstract

The formula SAE is a competition among students worldwide, where they are challenged to design, build and test a small formula-type racing car, following rules and specifications defined by the Society of Automotive Engineers (SAE). In the present analysis, a premature failure of a half-shaft of the transmission system of a racing car occurred after circa 100 km of use. The fractured component was analyzed by means of metallographic, chemical and mechanical analysis, fractography and finite element analysis. The results show that the alloy steel bar used for the half-shaft did not follow specifications, with a consequent lower strength and resulting in a material with insufficient loading capacity and fatigue resistance. As a consequence, the fracture process was a confluence of torsional fatigue crack propagation and overload ductile fracture through the spline section of the half-shaft.

8. Conclusion

Based on the observations, the following conclusions can be made:  The use of a AISI/SAE 4140 steel instead of the specified AISI/SAE 4340 steel had a decisive influence on the premature failure of the component, as the lower hardenability and strength resulted in a microstructure with insufficient mechanical properties for the requisites of the half-shaft.  The failure of the half-shaft occurred by a combination of torsional fatigue and overload. Fatigue cracks were nucleated at the root of the spline, which reduced the loading capacity of the component. Plastic deformation due to overload occurred on multiple events, evidenced by the twisted threads and the fracture surface.  The finite element analysis has shown that the higher stresses were observed at the filet at the spline region, especially at the face of the spline teeth, corroborated by the wear observed in these regions.