The surface quality can be determined by several characteristics, including the microstructure of the metal, the physical and mechanical state, and the roughness of the surface layer. Wear resistance, contact stiffness, vibration resistance, strength of joints depend on the latter, which is why it is very important to be able to correctly determine the roughness.
Necessary
- - measuring devices of shadow or light section;
- - indicator depth gauges.
Instructions
Step 1
Choose a device for measuring roughness, it can be shadow or light section devices, indicator depth gauges, with which you can measure unevenness with a height of 25 to 1600 microns. In this case, the expected distance from the lowest point to the highest point of the largest unevenness should be within the measuring range.
Step 2
If you have chosen an indicator depth gauge as the instrument, fix the dial indicator in the block so that the measuring tip protrudes by a stroke from 1.6 to 2.0 mm above the surface. Place the device with the support plane of the block on the control plate (at least 100x25 mm in size) and align the indicator arrow with zero on the device scale.
Step 3
To measure irregularities with a screw eyepiece micrometer, set it so that one of the reticle is parallel to the centerline of the profile.
Step 4
Examine the surface and select the largest irregularities to measure. At the same time, it is impossible to measure large potholes, cracks, shells, since they can significantly distort real indicators.
Step 5
Take measurements (at least five), and if you use optical means (a light section device or a shadow section microscope), then use a screw eyepiece micrometer to find the dimensions of irregularities. Take the length of the section no more than two steps along the depressions.
Step 6
When measuring with a screw eyepiece micrometer the distance from the highest point to the lowest point of unevenness, align the reticle (parallel to the profile line) first with the top of the ridge (S1i) and then with the bottom of the valley (S2i). At the same time, take readings of the micrometer each time and write them down in the journal. Calculate the distance from the highest point of unevenness to the lowest using the formula Нmax i = 5 / N (S1i-S2i), where N is the lens magnification.
Step 7
To measure unevenness with a depth gauge, set it so that the tip touches the bottom of the largest depression. Then take the reading, taking into account that the movement of the hand from 0 counterclockwise corresponds to Hmax i (the distance from the highest point to the lowest).
Step 8
Calculate the roughness in micrometers using the formula Rm max = 1 / n∑ Нmax i, where n is the number of measurements.
