Increasing efficiency of the mechanical properties and materials life of the cardan shafts manufactured from steel and composite materials

It is aimed to produce cardan shafts with better mechanical properties and longer service life. Some improvements have been investigated by using different heat treatments on the steel shafts, and failure analysis studies have been done within this scope. Additionally, some studies on designing and manufacturing of composite shaft, which is a recent promising machine element, have been carried out. A new heat treatment procedure has been investigated by considering AISI 4140 and AISI 4340 steels, which are widely used material for ordinary shafts, to obtain multiphases in the microstructure of shafts. Additionally, the microstructure and mechanical properties of the materials which is obtained by the new heat treatment are determined. The production processes have been tried to be optimized for obtaining the shafts with longer fatigue life and less heat treatment defects. Results with the new heat treatment show that it is possible to obtain much more flawless structure and, therefore longer fatigue life which can be up to three times of an ordinary shaft life. As an alternative to the steel shafts, composite shafts have been designed and fabricated by using two different manufacturing methods, and the results have been compared. Shafts manufactured by using VARTM method give better results compared to the ones manufactured by using vacuum bagging method. Additionally, it has been shown that hybrid composite shaft can provide high price/performance ratio. Furthermore, Finite Element Method (FEM) studies have been carried out for modeling and simulating the behaviour of metallic and composite shafts, and the results are compared with the experimental data.