Testing of Materials
Apart form knowing a material’s composition and behavior, the next step is actual testing of the material’s integrity. In terms of mechanical property of the material, its strength, brittleness and fatigue must be determined.
A material is said to be strong when it could resist a certain amount of load. During a test it is subjected to stress, which is the amount of load applied which could then result to strain the amount of deformation. With a small applied stress the material could go back to its original shape like a rubber band once the applied load is removed. This type of response is known as elasticity. But when stress is sufficiently large, the material might deform. In this stage the material is said to have reached its yield stress. But once the material reaches the maximum amount of stress it could take before it breaks, it had reached its ultimate strength.
In practice, the material to be tested is to be stretched to a breaking point in an instrument that could induce stress such as a Universal Testing Machine. A specimen is taken and machined to a cylindrical bone shape to ensure it will break at the middle.
In the evaluation of brittleness, an impact test is then used. The material would be subjected to a sudden intense blow. A material is said to be tough if it is able to withstand such impact. In the case of materials applied in repeated stress below its yield strength, it will be subjected to a cantilever beam test. The material will be turned 180 degrees with stress increasing at each turn. The purpose of this is to measure the material’s fatigue level. The fatigue life is the number of turns it in the test could take before breaking
For the physical property of a substance, in this case the electrical property, it is determined through the material’s conductivity. The thermal property, which is the coefficient of expansion or how much change heat could induce in a substance is also considered while corrosion resistance is what determines its chemical property.