What is Surface roughness: Definition and 16 Discussions

Surface roughness, often shortened to roughness, is a component of surface texture. It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, the surface is rough; if they are small, the surface is smooth. In surface metrology, roughness is typically considered to be the high-frequency, short-wavelength component of a measured surface. However, in practice it is often necessary to know both the amplitude and frequency to ensure that a surface is fit for a purpose.
Roughness plays an important role in determining how a real object will interact with its environment. In tribology, rough surfaces usually wear more quickly and have higher friction coefficients than smooth surfaces. Roughness is often a good predictor of the performance of a mechanical component, since irregularities on the surface may form nucleation sites for cracks or corrosion. On the other hand, roughness may promote adhesion. Generally speaking, rather than scale specific descriptors, cross-scale descriptors such as surface fractality provide more meaningful predictions of mechanical interactions at surfaces including contact stiffness and static friction.Although a high roughness value is often undesirable, it can be difficult and expensive to control in manufacturing. For example, it is difficult and expensive to control surface roughness of fused deposition modelling (FDM) manufactured parts. Decreasing the roughness of a surface usually increases its manufacturing cost. This often results in a trade-off between the manufacturing cost of a component and its performance in application.
Roughness can be measured by manual comparison against a "surface roughness comparator" (a sample of known surface roughness), but more generally a surface profile measurement is made with a profilometer. These can be of the contact variety (typically a diamond stylus) or optical (e.g.: a white light interferometer or laser scanning confocal microscope).
However, controlled roughness can often be desirable. For example, a gloss surface can be too shiny to the eye and too slippery to the finger (a touchpad is a good example) so a controlled roughness is required. This is a case where both amplitude and frequency are very important.

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  1. Quietrabbit

    Alternate ways to measure surface roughness?

    I am trying to compare the surface roughness of 3D printed specimens for a school project, but I am realizing I don't have access to any of the standard equipment that would be used to measure it. Are there alternative measurements I would be able to use that would yield similar results, using...
  2. J

    Typical surface roughness heights for aircraft surfaces

    Hello! I am investigating some preliminary aerodynamics on a regional turboprop and for the drag model the surface roughness height of the airplane is required as an input. For this i do not have any data. In which range are the typical values for modern aircraft surfaces? Thanks a lot!
  3. T

    Surface smoothness of a slowly frozen metal droplet

    Would a small (of order 5 microns to 0.5 mm) liquid metal droplet, if cooled slowly away from external perturbations and not in the presence of oxygen, retain its highly smooth and polished surface as it froze? What phenomena would influence the surface roughness? I assume that simple density...
  4. ccdani

    Transmission of blue light through ceramics and surface roughness effects

    Hey :) I measured the transmission of blue visible light (350-550nm) through lithiumdisilicate ceramics with an ulbricht ball and an spectrometer. The light source was a led dental curing unit (bluephase style). The light guide was positioned direct on the ceramics. Now I wanted to test...
  5. M

    Effect of the surface roughness of a wing

    Homework Statement I am doing a report on the effect of the surface roughness of a wing on the wing's performance. This was done by testing a a wing design in a wind tunnel using a smooth, intermediate and then rough surface. The test involved varying the pitch angle and tunnel power setting...
  6. Talal

    Surface roughness in 2D sinusoidal corrugation

    Hello, For a project I am working on, I am trying to design a 2D with parallel sinusoidal patterns. Imagine a 2D section of a pipe (two parallel surfaces with distance in between). Each surface is basically a sine function. Peak points meet with each other, as well as troughs. Liquid is...
  7. M

    Can surface roughness on wings improve performance

    Homework Statement I have a project to research the effect of surface roughness on wing performance. I found mostly that roughness leads to increased drag on a wing, however came across a website that briefly spoke about how recently researchers have observed how carefully selected roughness...
  8. M

    Literature survey - wing surface roughness effect on performance

    Homework Statement I am currently trying to do a literature survey on my project task 'effect of wing surface roughness on wing performance'. I have been struggling to find many research papers that are of a similar experiment to mine, however i have come across many that investigate the effect...
  9. Prateeksha Sharma

    How to design surface roughness model using CST?

    I am working om multilayer hybrid plasmonic waveguide (Si-SiO2-Ag_SiO2-Si). I have to see effect of roughness on propagation length and other parameters. So in reference to that I am having some doubts: 1) I use CST microwave studio for numerical simulation. I am not getting any direct option...
  10. D

    I Surface roughness and Magnus force of a cylinder

    I know that the surface roughness plays an role in the Magnus force exerted of a rotating cylinder. But, i cannot find an equation that includes the surface roughness in the equation of the Magnus force. If someone could state the formula (and preferably a source to read up more on it) it would...
  11. M

    Inquiry on effects surface roughness on Tidal Turbines.

    Hi, I'm an intern in an energy research company and I'm asking if anyone has any links or channels to papers or studies conducted on the effects of barnacle growth or other causes of surface roughness on tidal turbines? I apologize in advance if I have posted under the wrong part of physics...
  12. O

    Correlation length of surface roughness

    I need a simple mental physical picture of interface roughness. If the auto-correlation function of surface roughness is Gaussian, does a long correlation length connote a smooth surface or not? I do not seem to be able to find a simple picture that would appeal to me physically. Thanks all for...
  13. S

    How to use interferometer for surface roughness calculations?

    Dear all I am working on a project and I need to measure the surface roughness of a specific type of wood. I don't want to make things complicated because I have to make the instrument myself. I think an interferometer can help me to measure surface roughness but I really don't know how to...
  14. J

    Which Surface Roughness value to use for pipe flow friction factor

    I am trying to predict pressure drop in a pipeline with a range of different materials. I have used a surface profilometer to measure the surface roughness of the different materials and I have values for various surface roughness variables - Ra Rz Rmax Rq Rm S Sm R3z Wt and a range of other...
  15. K

    Improving Surface Roughness of Polypropylene and Measuring Surface Roughness

    Hi everyone, I was just wondering if anybody can offer me any tips or advice for a project I am working on at the moment. We have been carrying out shot blasting using various abrasives to improve the surface roughness of some polypropylene parts that we are making for the medical industry...
  16. N

    What is the mathematical measurement of surface roughness?

    Dear Experts! Do you know any mathematical measurement of roughness of surface? Thank in advance.