Dependence of micro-morphology of electrical strain gauges on stress distribution

We investigated the determinations by the micro-morphology of the sensitive grids of resistance strain gauge on their stress distributions. The micro-morphologies of the sidewalls for four typical resistance strain gauges were observed by scanning electron microscopy (SEM), and then the microscopic images were binarized to obtain the micromorphological characteristics of the sensitive grids. The observation shows that the sidewalls of the sensitive grids have periodic microstructures. A geometrical model of sinusoidal contour and a strain transfer model was established following the observed micro-morphological features. The influence of the amplitude and period parameters of the sinusoidal contour on the stress level of the sensitive grid was calculated numerically. The results show that the maximum stress increases, however the average stress decreases, with the increase of the profile amplitude with a certain periodicity. For a sinusoidal profile having a fixed amplitude, its maximum stress decreases with the increase of the cycle, wherever the average stress increases. The smaller side wall defects and longer interval in a sensitive grid would make the stress distribution more uniform. The obtained results would provide guidance for the fabrication of the resistance strain gauge.