On the tribological behavior of retrieved hip femoral heads affected by metallic debris. A comparative investigation by stylus and optical profilometer for a new roughness measurement protocol

In this study, 35 retrieved ceramics femoral heads with evidence of metallic dark lines on the surface were analyzed. The surface roughness of these femoral heads was acquired using both a stylus contact profiler and an optical non-contact profilometer. The metallic deposition on hip ball surface, also known as Metal Transfer (MT), appeared as dark metallic and can occur during the surgery or during the reduction of a dislocated prosthesis. In this study, we validate a new protocol to measure surface roughness on retrieved femoral heads, by using the aforementioned two different acquisition techniques and also to investigate the hypothesis that such metal transfer retrieved ceramic femoral head is associated with increased surface roughness.All femoral components of this investigation showed remarkable differences in roughness values between MT-affected and MT-unaffected areas. The two acquisition procedures – conventional stylus and 3D confocal profilometer – confirmed a satisfying agreement, even considering the obvious resolution difference.     

Investigations on machined metal surfaces through the stylus type and optical 3D instruments and their mathematical modeling with the help of statistical techniques

The measurement of roughness on machined metal surfaces is of considerable importance to manufacturing industries as the roughness of a surface has a significant influence on its quality and function of products. In this paper, an experimental approach for surface roughness measurement has been based on the comparison of roughness values taken from the stylus and optical type instruments on the machined metal surfaces (turning, grinding and milling) is presented.Following this experimental study, all measured surface roughness parameters have been analyzed by using Statistical Package for Social Science (SPSS 15.0) statistically and mathematical models for the two most important and commonly used roughness parameters R_a and R_z have been developed so that R_a = R_a (F, P, C) and R_z = R_z (F, P, C, M), whereas F expresses feed, P periodicity, C contrast and M the type of material. The statistical results from numerous tests showed that there has been a correlation between the surface roughness and the properties of the surface topography and there have been slight differences among three measurement instruments on machined metal surfaces in this experimental study.     

The effect of tip size on the measured Ra of surface roughness specimens with rectangular profiles

When measuring rectangular and trapezoidal profile roughness specimens, the stylus tip increases the measured profile peak width and decreases the measured valley width. This can cause either an increase or a decrease in the apparent roughness average Ra, depending on the tip size and the ratio of peak width to valley width. Sometimes the change is larger than the combined measurement uncertainty from other sources. This raises the question as to whether measured surface parameters should be corrected for the effect of tip size.