Experiment And Numerical Analysis Of The Rotation And Fretting Behavior Between GCrl5Steel And PP Plastic

Rotation and fretting behavior is considered as two kinds of slightly relative motions on touching surface under cyclic loading. It always occurs in the fitting surface which can be found in ball socket joints, wheel and yoke shaft mechanisms in locomotives and vehicles, and the space between the hip and the knee in human implanted devices. These mechanical structures are always suffering from a failure because of fretting. Mo Jiliang et al.(2008) made a rotation and fretting test of ball-flat touching. Then, many researchers studied the wear properties of various materials subjected to rotation and fretting. It should be pointed out experiment method is still the main method to study the rotation and fretting behavior of a specific medium. This would make the research costly. This situation can be changed by means of finite element method (FEM), which is a powerful tool to examine the moving and wear mechanism of the materials involved. A lot of material resources will thus been saved.(1) With multi-functional fretting machine (CETR UMT) and high precision six-dimensional mechanical sensor (CETR TH-50), the rotation and fretting behaviors between PP plastic flat and GCrl5steel ball under different rotation amplitudes are tested. The test results show that the rotation amplitude has great influence on the rotation and fretting behaviors, and that the transition from partly sliding to totally sliding can be described with F(?)θ curve and friction coefficient curve. Through the rubbed surface, the grinding crack and the profile curve vary with rotation amplitude, and the phenomenon of uplift at the touching center with concave at the two sides exists in all situations.(2) By virtue of Marc with Achard wear analysis model, the simplified finite element model of PP plastic flat to GCr15steel ball is simulated under one characteristic loading cycle. From the analysis of wear displacement, plastic strain and wear curve on the touching surface, the wear behavior is seen to occurs in the touching center, and the wear radius is nearly0.8mm which is becoming harder with the decrease of rotation amplitude, and the plastic flowing is the main reason of the uplift found in the touching center under bigger rotation amplitude. Furthermore, in view of the plastic strain contour, the Mises stress contour and the wear contour, the plastic flowing actually exists in the process of rotation and fretting, and the rotation amplitude deeply influenced the stress-strain size as well as the plastic flowing intensity.(3) Comparison of the FEM results with the corresponding test results shows that the surface plastic strain contour is consistent with the actual fringe grinding crack.; the wear rate contour reflects the spreading trend of grinding crack from the touching center to the sides; the surface plastic deformation is consistent with the profile topography; the accumulation of wear debris the plastic flowing is considered as the reason of uplift in the touching surface. Therefore, the numerical results obtained by FEM is consistent with the experimental data. As a consequence, FEM, as a method of study the rotation and fretting behaviors of various materials can be employed to investigate more involved problems..