Abstract
Biomedical implants like the hip joint with cup work under continuous friction and wear phenomena where soft materials are suitable for the low coefficient of friction. As continuous, joints go under dynamic fatigue that should be accelerated by the fretting action generated from contact pairs and the inclination angle of the femur. In this research, the fatigue behavior of PTFE has been studied and compared under friction along with fretting action. A FE based Numerical model justified the experimental results. It showed that fretting and friction influence the fatigue life of PTFE by various angles. Fretting pressure optimization was identified as the determinant factor, while the loading point ratio was remarked as an effective parameter for both fretting and friction fatigue. Penetration depths proportionality to corresponding stress observed the effect of fretting fatigue where friction acts in different degrees depending on the geometry (collar/notch)-loading (friction) position. The fractographical demonstration revealed a relation between crack orientation and fretting action. Predefined loading action on test samples justified the singularity of fretting-friction fatigue characteristics on the damage mechanism of PTFE.
Highlights
In industrial applications, due to its low co-efficient of friction, PTFE (Polytetrafluoroethylene) is being used in the plain heading, gears, slide plates, seals, gaskets, bushings and more applications with the sliding activity of parts, where it works better than acetyl and nylon [1]
In this research, Rotating bending fatigue behavior of PTFE has been studied under the action of fretting and compared with the sliding friction effect
- Fretting fatigue reduces the lifetime of more than 90% for PTFE
Summary
Due to its low co-efficient of friction, PTFE (Polytetrafluoroethylene) is being used in the plain heading, gears, slide plates, seals, gaskets, bushings and more applications with the sliding activity of parts, where it works better than acetyl and nylon [1]. To resist fluid leakage from the cylinder when the system pressure pushes the piston inside the cylinder bore, PTFE piston with seals are desired. Rod seals prevent high-pressure fluids from passing out of the cylinder in a linear bi-directional motion. PTFE is preferred as a chemically neutral material of nuclear valves and seals. Machined, compounded PTFE elements are used in cases where elastomeric seals cannot sustain the temperature, frictional, or chemical resistive requirements of the application. When friction acts along with fatigue, the stress, as well as the life cycle is influenced- fretting fatigue occurs [2] that can be classified into reciprocating and rotating type fatigue [3].
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