Surface Roughness Essay

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’TECHNICAL DATA» SURFACE ROUGHNESS Categories of surface roughness EXCERPT FROM JIS B 0601 1994) ( AND JIS B 0031 1994) ( Definitions and indications for surface roughness parameters for industrial products) specified. ( are They are arithmetical mean roughness Ra)maximum height Ry)ten-point mean roughness Rz)mean ( , ( , ( , spacing of profile irregularities Sm)mean spacing of local peaks of theprofile S) profile bearing length ( , ( and ratio tp)Surface roughness is given as the arithmetical mean value for a randomly sampled area. ( . ’Mean center line roughness (Ra 75) defined in the annexes of JIS B 0031 and JIS B 0601.» is Typical ways for obtaining surface roughness Arithmetical mean roughness (Ra) A section of standard length is sampled from the mean line on the roughness chart. The mean line is laid on a Cartesian coordinate system where in the mean line runs in the direction of the x-axis and magnification is the y-axis. The value obtained with the formula on the right is expressed in micrometer Om)when y=f ◊) ( . ( Y m R Ra= R 1 0 f(◊) d◊ Ra 0 X R R Maximum peak (Ry) A section of standard length is sampled from the mean line on the roughness chart. The distance between the peaks and valleys of the sampled line is measured in the y direction. The value is expressed in micrometer Om) ( r . Note: To obtain Ry, sample only the standard length. The part, where peaks and valleys are wide enough to be interpreted as scratches, should be avoided. m Rp Ry Ry=Rp+Rv Yp 1 Ten-point mean roughness (Rz) A section of standard length is sampled from the mean line on the roughness chart. The distance between the peaks and valleys of the sampled line is measured in the y direction. Then, the average peak is obtained among 5 tallest peaks (Yp)as is the average valley between 5 lowest valleys Yv) , ( . The sum of these two

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