Analysis of the stress field in a threshold-galling test

The wear phenomena of galling is characterized by macroscopic roughening and deformation of the surfaces of mated materials. Currently, the ASTM G98 button-on-block test method is the only standardized testing procedure for determining the galling resistance of material couples. The pattern of surface damage resulting from performing the ASTM test tends to be predicable. In particular, the galling generally occurs near the outer edge of the button and migrates inwards. In this study, the stress distribution between the mated specimens leading up to the onset of galling was investigated. A suitable analytical model of the system geometry and loading conditions was developed and applied. The results of the model show that a stress concentration exists along the edge of the button specimen when loaded. The stress concentration is believed to contribute to the initiation of galling at this site. The results of the analytical model have also shown that the magnitude of the stress concentration is dependent on the size of the corner radius. An alternative testing arrangement is presented and preliminary results are shown.