PEMODELAN KEAUSAN STEADY STATE

Abstract

In engineering design, tribology science carries critical contribution to the reliability and efficiency of the machine components. The focus of the tribology science on friction, wear and lubrication plays important role in reducing losses, increasing energy efficiency and determining the component’s life span, especially for the high forces and rapid movement components. In sliding contact, researchers divided the wear cycle into three important phases: running-in, steady state phase and accelerated wear/wear out phase. On the steady-state phase, the adjustment of the wear rate, contact pressure, surface roughness, and surface conformability at the contact interface attains the stabilized condition. The aims of this research is to model the steady state phase, incorporates mild wear, by employing the analytical, numerical and experimental solutions. Hertz’s analytical formula for elastic contact was developed to predict the wear on the steady state phase of the point and line contacts. The finite element analysis (FEA) is simulated to observe the contact pressure of the sliding contact on a pin-on-disc contact system. In the FEA, the input are geometry, boundary condition, material properties and initial load. Then, the obtained contact pressure is use in wear calculation based on Archard’s wear law by considering the sliding distance. The wear depth of pin for conformal and non-conformal contact is predicted. The ball-on-disc experiment was conducted to verify the wear prediction based on the analytical and the FEA solution. The analytical, FEA and experimental solution show that the wear on the running-in phase increases dramatically until reaching the steady state phase, where the stable condition occurs. In the analytical solution, the steady state phase is identified as the stabilized wear rate for the increasing of the sliding distance. In the FEA solution, the steady state phase is recognized by observing the stabilized contact pressure on the contact area as the sliding distance increases. Combination of the FEA solution and Archard’s wear law predicts the stabilized wear rate on the sliding contact. Experimental observation agrees well with the FEM and analytical solution where the wear of the ball is initially high and reaches its stabile condition at steady state phase. The interesting phenomenon in sliding contact of ball-on-disc discloses that the radius of the ball increases as the sliding distance increase. The ratio of the initial radius to the worn radius of the contacting ball tends to reach zero when the steady state phase is obtained. Key words: steady state, mild-wear, conformal contact, non-conformal contact, FEA.