Development of a Piezoelectric Shear Stress Gage for Dynamic Loading

This report describes a combined analytic and experimental approach to demonstrate the feasibility of developing a piezoelectric shear stress gage sensitive only to shear loading. A simplified but general analysis of the mechanical and piezoelectric response in anisotropic crystals was carried out. Both the mechanical and piezoelectric analyses provide criteria for developing a suitable shear gage. When these criteria were applied to alpha quartz and lithium niobate (LiNbO sub 3), only the 163 degrees Y-cut LiNbO sub 3 appeared suitable for our purposes. Impact experiments, using the recently developed combined compression and shear loading facility, were conducted to verify the use of 163 degrees Y-cut LiNbO sub 3 for shear stress gages. The results of these experiments show that the gage has negligible sensitivity to compressive stresses and a very large sensitivity to shear stresses. Hence, 163 degrees Y- cut LiNbO sub 3 may be used as a stress gage sensitive only to shear loading. Further development of gages for routine use in laboratory and field measurements requires additional calibration experiments and development of proper packaging techniques for field experiments.