The simplest software which we offer to our customers is the Surface Generator. This program generates a randomly rough surface with a specific power spectrum or statistical properties. To understand let us briefly review what surface roughness is and hence what the outcome of this software is.

Surface roughness is defined as the deviation of a real surface from its ideal form. In practice one often categorizes surface roughness components on different length scales into different categories, e.g. macrotexture and microtexture, by considering different frequency or wavelength components of a given surface. In practice almost all real surfaces in technology and Nature exhibit surface roughness. For many surfaces, e.g. a road surface, roughness occurs from centimetre length scales all the way down to atomic resolution. Also a highly polished metal surface, e.g. balls for rolling bearings, is rough when studied on small length scales like micro- and nanometer.

Roughness on a very large length scale - deviation of the earth surface from its spherical shape	Roughness on a very small length scale - Scanning electron microscopy of cracks on a metal sample

Because roughness occurs basically on all surfaces it is necessary to consider it when designing a product or studying the interaction between two bodies. Today this is often done using finite element methods or other numerical approaches studying a certain system. For these kind of calculations it is necessary to generate a suitable topography input file with a certain kind of surface roughness. This can either be done by measuring the roughness (surface metrology) or by mathematically generating a topography.

This is what the roughness generator is used for. It generates a randomly rough surface with given roughness properties. The generated topography is then used for, e.g., molecular dynamics simulations where the adhesion between two solids or the viscoelastic energy dissipation between a rubber block in sliding contact with a rough counter surface is calculated. The roughness properties are given by the power spectrum (PS). Here the power spectrum information can either be read in numerically from a file or specified by supplying the characteristic parameters q0, qr, q1, h0 and H. Roughness anisotropy, as it occurs e.g. on grinded steel surfaces, can also be taken into account by giving the peklenik number. The surface generator will calculate a random realization of a topography with the given statistical properties. The result is provided as plain ASCII file with x, y and z coordinates given in three columns.

The roughness generator is available for Linux as well as for windows. Please note that the handling of the program is very different depending on the operating system. The Linux version is a CLI (Command-line interface) program where flagparameters need to be set in different input files according to what should be calculated. On the other side the Windows version is a GUI (Graphical user interface) software allowing the user to directly choose different options in the user interface. The figure below shows the latest Windows version of the software and its different input parameters.

For further information on the roughness generator please consider the following information:

For more information on surface roughness as well as the surface roughness power spectrum we would like to refer you to our online lectures.

In case you are interested in using the surface generator or you have further questions concerning the software please feel free to contact us.