Development of contact failure analysis technology - first year(2000) report -

Contact tractions are affected by the geometry of contacting bodies. In the present research, square punch, wedge and cylinders are considered as the geometry. Among the geometry, a square punch with rounded corners is basically used. Normal traction profile is obtained in the case of the rounded punch, and shear tractions are evaluated under the partial slip regime by using the influence function method. Multiplication of the shear traction and slip displacement in the slip region of the contact provides the friction energy dissipation from the contact. Since the trace of the shear force influences the amount of the dissipated energy, a desirable trace of the shear force may be supposed to reduce the energy dissipation. Internal stresses are evaluated from the contact normal and shear tractions, which are to be used for calculating the stress intensity factors of a surface breaking crack emanated from the contact surface. The stress intensity factors, KI and KII, are investigated during the cyclic shear. It is found that a period of crack opening exists during a shear cycle, which is effective for crack growing. So, to reduce the period can be a method for restraining the cracking failure. On the other hand, there can exist a desirable shape of the contacting body, which can restrain the cracking failure. In the experiment, fretting wear tester is used with the specially designed specimen. Wear of the contact surface are observed in detail, which shows typical shape following the partial and gross slip regimes. An algorithm for evaluating the wear volume is newly developed using the signal processing technique and the Fast Fourier Transform (FFT)