الفهرس 
ApestractOnly 14 pages are availabe for public view
 |  | from | 127 |  |  |
| | | from | 127 | | |
Abstract
The artificial hip joints are widely used, and for the time being, the artificial hip joints are mainly made either from Stainless Steel 316 L or Titanium because of either high mechanical properties, special corrosion resistance, and consequently their capacity to work in a human body as an artificial hip joint, while subjected to many different stresses, as well as the highly corrosive fluids of the human body.
It is very important to manufacture the artificial hip joints using metals of high mechanical properties and good resistance for corrosion to avoid the problems of short life of the artificial hip joints.
In this concern, this study is a trial to evaluate availability of using other metals for producing artificial joints, with high mechanical properties and good corrosion resistance, meanwhile, more available, light and reasonably cheap such as Aluminum Alloys grade 707 & 7475.
Moreover, the study is carefully considered the necessary heat treatment required to improve the hardness of the selected Aluminum alloys to levels between 140 and 181 Brinel.
The study also concentrating on obtaining through experiments the optimum passivation layer needed to improve the corrosion resistance of the Aluminum alloys up to the accepted levels for the required application.
Experimental Work
The experimental work in this study is divided into two main groups as follows:
1)Laboratory measurements for specimens of the two selected grades of Aluminum alloy to investigate hardness, tensile strength and corrosion resistance, before and after chemical treatments.
2)Simulation Test rig to investigate behavior or the artificial hip joint made from Aluminum alloy, when facing all different stresses similar to actually affecting the join in human body.
Concerning the first part of experimental work, the hardness and tensile strength were measured, and the results of hardness were not sufficient for the required application, as well as that of tensile strength compared to stainless steel316 L. However, the result of hardness shows that heat treatment of Aluminum alloys is a must to improve the hardness.
So that, specimens were heat treated, and then the experiments were repeated again for both hardness and tensile strength.
The treatment result shows a great improvement, almost three times the previous result before heat treatment, meanwhile, tensile strength result shows a very close reading to that recorded for Stainless Steel 316L.
Recording corrosion, specimens, of the two selected grades of Aluminum alloy are tested for corrosion without any passivation operation as well as one specimen of Stainless Steel 136L the results of Aluminum alloys were quite far from Stainless Steel as an accepted reference.
The measurements were repeated for passivated spicemens with different layers with different layers, the thickness of each layer was controlled by controlling the passivation time , results show as indirect propotion between thickness of the passivation layer and corrosion rate.
The optimum passivation time was defined as the passivation time needed to give the lowest corrosion rate.
Concerning the second part of experimental work, a test rig is designed and constructed to simulate all possible stresses could be applied on an artificial hip joint in human body.
The design of the simulation test rig considered all stresses at maximum limits.
The test is performed with a number of balls made from the two selected grades of Alluminum alloys, then they were heat treated, and passivated with different thickness, and a Stainless Steel ball was used as a reference.
Balls were connected to the test rig (After recording the initial weight of each one),and then the simulation test were run for each ball for a constant calculated period.
Using the weight loss of each ball, the wear rate calculated as Volume per time.
Comparing the wear rat of each ball with that of Stainless Steel 316L ball, it is clear that wear loss calculated on as Aluminum alloy 7475 ball, heat treated and anodized for the optimum time, is very close to that calculated on the ball made from Stainless Steel 316L.