الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
Polymeric materials, many ycars ago, have bcen employcd in numcrous mechanical and medical applications dll(’ to its cxcellent mechanical and tribological properties. This encouraged the designer and developer of mechanical and biomcdical systems to study its behavior under different operating conditions.
Wear is one of the commonly failure mode associated with hardwarc. Reduction and control of wear tend to be a great challenge because of the complexity of wear behavior and the lack of a unifing theory or model, such as those used for fracture and fatigue. Many intensive studies, over the last 30 or so years, have been developed to investigate the influence of different factors affecting wear in polymers in order to clear this feature.
The present thesis studies the influence ofloading nature ( loading mode) on the wear behavior of Polyamide (PA 66) sliding against stainless steel in dry condition. The polymer was, first, tested under constant load then further tests were conducted under fluctuating loading condition where the mean of the cyclic load was adjusted to be equal, in magnitude, to the static load. Moreover, additional tests were performed to study the effect of load frequency and load ratio (Pamp / Pm,,) on the wear of the polymer. The polymer was tested at three different frequencies and under four different load ratios. Finally, an explorer test was conducted to investigate the effect of the initial contact stress on the wear under cyclic load. In this test, the polymer was introduced with a constant applied stress equal to 0.12 of that used in the previous tests, while the other testing conditions were fixed.
A new testing machine was designd and constructed to perform wear tests under constant and fluctuating loading conditions. The machine has the configuration of pin un plate. The tests can be conducted under dry or wet conditions. Also, it has the facility of changing the amplitude, mean load and the frequency of loading cycle.
As would be expected, the wear rate (Volume loss / Sliding distance) of polymer under constant load generally increases with increasing load. but the wear factors (Volume loss I Load x Sliding dls!
A clear tendency of the wear factor to the load frequency and load ratio, (Pillnp / Pm”,). was, also. observed. As the load frequency was increased, a corresponding increase in wear fllctors was detected. On the other hand, the results indicated that the effect of load ratio on the wear behavior was governed by the change in the mean load. In contrast, IDr the same mean, the change in load ratio has a minor effect on wear factor. But if this change was accompanied by a change in the mean load, a significant increase in the wear factor becomes noticeable.
The result of the preliminary test suggests that the polymer wear has a great dependence on the apparent area of contact rather than the applied load, under fluctuating loading condition. However, we still need more study in this topic.
III