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What Does Roughness Size Mean in Practice?

Views: 0     Author: Site Editor     Publish Time: 2024-06-12      Origin: Site

Roughness, everyone is quite familiar with it, so I won't go into too much detail here. However, there is a question that you can ask yourself: what does choosing a higher or lower roughness mean in practice? What is the physical impact it brings? For example, what exactly does choosing Ra3.2 and Ra1.6 affect the bearing mating surface? If you are used to following the recommended values in the manual or selecting roughness values based on experience, you have never considered this issue. So I hope this article can broaden your thinking.

We won't randomly choose a roughness, the selection of a specific roughness is always to meet a certain function and improve a certain performance.

For individual parts, roughness not only affects the appearance and touch of the component, but its value mainly indicates the magnitude of stress concentration. From a microscopic perspective (as shown in the previous figure), the larger the roughness, the greater the difference in height between potholes and more gullies. In areas subjected to high tensile stress loads, stress concentration exists in gullies, which are also the source of cracks. So to improve fatigue strength, it is necessary to choose a smaller roughness.

More often than not, roughness is used for matching between two parts. There are many factors that can affect roughness here, such as friction coefficient, wear, deformation, heat conduction, leakage, adhesion, and so on.

The smaller the roughness, the smaller the friction coefficient and resistance. Small roughness is required between components that rotate rapidly, such as between the rolling elements and raceways of bearings.

If the roughness is small, the micro level "small peaks" will not be very high or many. When there is vibration or high pressure between two components, there will be no changes in connection stiffness or slight changes in fitting size due to the grinding and compression deformation of the mountain peak, and the occurrence of micro wear will also be reduced.

If the roughness is small, the better the surface adhesion between the two parts and the better the heat conduction effect. In some areas where heat dissipation needs to be improved, the roughness requirements should also be higher. Additionally, a small roughness will also reduce the possibility of oil leakage.

For adhesion, a rough surface can provide more surface area for the adhesive, which helps improve bonding strength. However, if the surface is too rough, the overall contact area may decrease and air may be trapped at the joint surface, thereby weakening bonding strength. So choose moderation.

In summary, the choice of roughness varies depending on the application, and may not be important in certain applications or locations, but it is crucial in the aforementioned situations and applications. Before choosing the roughness size, why not think about my purpose? Perhaps it can be more targeted.


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