Spatially Resolved Strain Measurements on Micro Moulds

The strain distribution in surface treated Toolox 44 steel was investigated using synchrotron Xray diffraction. Surface treatment involved a sequential application of grinding, micro milling and abrasive micro peening processes. The micro-features created at the milled surfaces were studied using a high lateral resolution CCD based Material X-ray Imaging (MAXIM) detector. Results from the strain measurements were evaluated with special consideration of the influence of possible geometric effects on the measured data. The sin2ψ method was used to determine the residual stress state at the surface of the treated samples. The results revealed that a large compressive stress component is superimposed on the ground surfaces by the milling process thus creating a stress profile different from that prior to milling. Subsequent abrasive micro peening on the previously machined surfaces removed the optically visible pattern created by the milling process and also introduced a residual stress state that is homogeneously distributed over the entire peened area. This study demonstrates the feasibility of accurately determining the strain distributions at localized features.