Evaluating Ra Value: Deviation of Peaks from the Centre Line

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  • Topic: Roughness, Materials science, Waviness
  • Pages : 2 (476 words )
  • Download(s) : 117
  • Published : March 15, 2013
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In this experiment, the factor that is evaluated is the Ra value, which is the mean deviation of the peaks from the centre line of the trace. In the case surface is considered smooth if the Ra value is equal or less than 0.1m. From the result of these experiment, we can say that different of the theoretical data and experimental value is very large. This is happen because value of n is not big enough to get accurate result. In this experiment we only that n=5 that’s make the huge different between theory and experimental result. Besides that, the value of Rq,Rz,Rp, and Ry calculated deviates from the standard readings. This is cause by three main factors: 1. Surface of materials: Before the experiment is done, the surface of materials should be cleaned complete removal of the oxide film from surface to have an accurate reading. If not, it will affect the roughness of the surface.

2. Size of materials: The size of the sample must be big and readings must be taken randomly all over the observed area. But, the experiment is done on only a very small portion of the surface. So, in our calculations, the sample size is inadequate to give a good approximation for the surface roughness values.

3. Experimental error : The machine used to analyze the surface roughness has a very sensitive sensor. When the surrounding factors (e.g. wind, temperature etc) vary, it will affect the roughness of the surface, and the readings will differ from the actual one.

There is many factors that contribute to the roughness surface, The designer using certain symbol normally draws the quality and surface texture pattern of a component, which is to be machined. Components like heat transferring tube and brake must have controlled surface texture. For the heat transferring tube, if the surface of the tube is a bit rough, the tube will transfer the heat even faster. The same thing also applies to the brake. Brake needs rough surface to ensure its...
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