الفهرس 
CHAPTER 1: Literature SurveyOnly 14 pages are availabe for public view
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Abstract
The objective of this work is to study the relaxation behavior and wear behavior of some thermoplastic materials [Polyvinyl chloride, Poly methyl methacrylate, Acrylonitrile–butadiene–styrene]. As the objective was a trial to find the effect of pre-relaxation on wear behavior of these materials at constant strain. Also the effect of motion parameters on wear behavior was studied.
In the present work a relaxation machine has been used in order to measure the relaxation. The applied stress was at 0.6 and relaxed to 0.5 from the yield stress of PVC, PMMA and ABS. Additionally, a pin-on-disc machine is used to measure the wear under several operation conditions.
from the study of the relaxation behavior of PMMA, ABS&PVC it was found that the relaxation time to fracture of PMMA is higher than ABS &PVC respectively. from the study of the wear behavior of the different polymeric materials after relaxation, it was found that Pre-relaxation (5, 15, 30 and 35% from the total relaxation time) leads to increase the weight loss of the different polymeric materials. This may be attributed to the fact that the relaxation process affects on the internal bonds of materials by weakness it.
ABS material was chosen to study the effect of motion parameters such as sliding velocity and applied pressure on the weight loss. The operation conditions were sliding velocities 3.9, 4.2, 4.4, 4.7 and 5 m/s; applied loads 10N, 20N, 30N, 40N and 50N., pre-relaxation time (35% of the total relaxation time) showed that Increasing applied load has a direct effect on weight loss of ABS. also at low loads the weight loss of ABS has low values.
The optical microscope showed that the transfer film increases by increasing both the applied load and pre-relaxation. Additionally, the amount of accumulated layers on the counterface during wear test increase by increasing the sliding velocity and applied load for the three polymeric materials.