When designing a part, the choice of surface roughness value is determined according to the function of the part in the machine. and then, What are the effects of surface roughness on parts?
1. Wear resistance. The rougher the surface, the smaller the effective contact area between the mating surfaces, the greater the pressure, the greater the frictional resistance, and the faster the wear
2. The stability of cooperation. For clearance fit, the rougher the surface is, the easier it is to wear so that the clearance gradually increases during the working process; for an interference fit, the actual effective interference is reduced due to the flattening of microscopic peaks during assembly. connection strength.
3. Fatigue strength. There are large troughs on the surface of rough parts, which are sensitive to stress concentration like sharp corner notches and cracks, thus affecting the fatigue strength of the parts.
4. Corrosion resistance. The rough surface of the parts easily allows corrosive gases or liquids to penetrate into the inner metal layer through the microscopic valleys on the surface, causing surface corrosion.
5. Sealing. Rough surfaces do not fit tightly, and gas or liquid leaks through the gaps between the contact surfaces.
6. Contact stiffness. Contact stiffness is the ability of the joint surface of a part to resist contact deformation under the action of external force. The stiffness of the machine is largely determined by the contact stiffness between the various parts.
7. Measurement accuracy. The surface roughness of the measured surface of the part and the measuring surface of the measuring tool will directly affect the accuracy of the measurement, especially in the precise measurement.
In addition, the surface roughness will have varying degrees of influence on the coating, thermal conductivity and contact resistance of parts, reflectivity and radiation properties, resistance to liquid and gas flow, and current flow on the conductor surface.
