Moiré patterns of slope contours in flexed plates

A simple method is described for the measurement of partial slopes in flexed plates. The interference of the resultant distorted reflection of a referenceline grating, projected by means of a collimated monochromatic light on the polished surface of a flexed plate, with an identical grating yields a moiré pattern of the partial-slope contours of the plate. The method can be applied to determine the moment and strain distribution of any type and shape of plate loaded to any loading mode. As an illustration, the method has been applied to determine the partial-slope distribution in laterally loaded square plates either supported at their corners or simply supported. Comparison of the results with existing numerical solutions shows the accuracy of the method.