Heat transfer between contacting surfaces is a key factor in the thermal behaviour of engineering components in turbomachinery and various other areas of technology. Thermal contact conductance (TCC) is a parameter that quantifies this heat flow. An ongoing challenge in measuring and modelling TCC is the different length scales of surface topography exhibited on real components. Manufacturing techniques such as turning and fly cutting introduce repeatable surface deviations of medium wavelength which are the focus of this study.
An instrumented split tube with in-line washers, loaded under carefully controlled conditions, was used to measure the TCC of washers made of PE16. Fly cutting was used in this study to introduce a repeatable lay typifying a range of manufacturing techniques. Experimental determination of TCC for (i) flat contacting washers and (ii) contact between flat washers and fly cut washers with repeatable lay is reported. As expected the latter case gives rise to significantly lower TCC than the former. A 2D finite element model is described which models the elastic-plastic deformation of a representative machining induced contact line. Using the TCC data for flat contacting surfaces, FEA is used to calculate the reduced TCC for the machined case. Predicted values of TCC assuming plane stress and plane strain are compared with experimental data.
