Application of thermodynamic principles in determining the degradation of tribo-components subjected to oscillating motion in boundary and mixed lubrication regimes

Recent studies reveal that the degradation-entropy generation (DEG) theorem based on thermodynamic principles can be satisfactorily employed to determine the degradation of a tribo-pair operating in dry uni- and bi-directional sliding as well as lubricated uni-directional sliding conditions. The theorem is based on the thermodynamic principles that consider degradation forces and correlates the entropy generation to wear through a parameter called degradation coefficient. This paper reports an investigation of the efficacy of extending the DEG theorem to lubricated oscillatory sliding conditions subjected to boundary and mixed-lubrication regimes. For this purpose, series of oscillatory sliding experiments are performed using a pin-on-disk test setup that cover a wide range of operating conditions. From the obtained experimental results, a new methodology to characterize the friction coefficient in oscillatory motion is presented and thereafter DEG theorem is applied to characterize the wear during the lubricated oscillatory sliding motion covering a wide range of oscillating angles and operating conditions. •The Degradation Entropy Theorem is applied to analyze wear in trio-components subjected to oscillatory motion.•Degradation coefficient is modified to assess wear in boundary and mixed lubrication regimes.•Experimental pin-on-disk tests confirm the validity of the results over a wide range of speeds and oscillation angles.