Measurement of the residual stress in the micro milled thin-walled structures

A new microbridge testing method to measure the residual stress of the micro milled thin-walled structure is proposed. Since this type of microbridge structures is of micron dimension, the normal residual stress testing methods, such as XRD and hole-drilling method, are difficult to be applied. To solve this problem, theoretic analysis is firstly conducted to provide a formula of deflection vs load, considering the existence of the residual stress in the micro structure. Using this formula, the residual stress can be evaluated. The 3J21 Alloy sample is prepared via the micro milling process. Experimental result shows that the residual stress in micro structure is around 120MPa, with the cutting depth of 10 μm and feed rate of 1mm/s.