Question
Download Solution PDFThe CLA value is used for measurement of
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
Whatever may be the manufacturing process, an absolutely smooth and flat surface cannot be obtained. The machine element or parts retain the surface irregularities left after manufacturing. The surface irregularities are usually understood in terms of surface finish, surface roughness, surface texture or surface quality.
Evaluation of surface roughness:
- Root mean square value: r.m.s. value
- Centreline average (CLA) or arithmetic mean deviation (Ra)
- Maximum peak to valley height (Rt or Rmax)
- The average of five highest peaks and five deepest valleys in the sample (Rz)
- The average or levelling depth of the profile (Rp)
The two most accepted methods of assessing the surface roughness are: Root mean square value and the arithmetic average or Centreline average value.
In both the methods, the surface roughness is measured as the average deviation from a nominal surface.
The value of surface roughness is expressed in micrometres (μm).
|
Parameter |
Definition |
Pictorial Representation |
|
Ra |
It is the arithmetic average of the absolute values of the roughness profile ordinates. Ra = Σ h/n |
|
|
Rz |
Average peak to valley profile roughness .the average is based one peak and valley per sampling length. The single largest deviation is found in five sampling length then averaged. |
|
|
Rmax |
Maximum peak to valley distance. Distance between the top of the highest peak and the bottom of the deepest valley. It is maximum of all peak to valley values |
|
Important Points
Surface roughness is represented by the triangle.
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