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Knowledge of Roughness

2023-08-16

1、After processing, the parts may experience large or small peaks and valleys on the surface of the workpiece due to cutting tools, chip deposits, and burrs. The height of these peaks and valleys is very small, usually only visible when magnified. This micro geometric feature is called surface roughness.
2、The Influence of Surface Roughness on the Performance of Mechanical Parts
Surface roughness has a significant impact on the quality of parts, mainly focusing on their wear resistance, fit properties, fatigue strength, workpiece accuracy, and corrosion resistance.
① The impact on friction and wear. The impact of surface roughness on part wear is mainly reflected in the peak and peak, where two parts come into contact with each other, which is actually a partial peak contact. The pressure at the contact point is very high, which can cause the material to undergo plastic flow. The rougher the surface, the more severe the wear.
② The impact on the coordination properties. There are two forms of component fit, interference fit and clearance fit. For interference fit, due to the flattening of the surface peaks during assembly, the interference amount is reduced, which reduces the connection strength of the components; For clearance fit, as the peak is continuously flattened, the degree of clearance will increase. Therefore, surface roughness affects the stability of the mating properties.
③ The impact of resistance to fatigue strength. The rougher the surface of the part, the deeper the dent, and the smaller the curvature radius of the trough, making it more sensitive to stress concentration. Therefore, the larger the surface roughness of a part, the more sensitive its stress concentration is, and the lower its resistance to fatigue.
④ Anti corrosive effects. The larger the surface roughness of the part, the deeper its wave valley. In this way, dust, spoiled lubricating oil, acidic and alkaline corrosive substances can easily accumulate in these valleys and penetrate into the inner layer of the material, exacerbating the corrosion of the parts. Therefore, reducing surface roughness can enhance the corrosion resistance of parts.