Buckling Control of Multilayered Diaphragm Structures for Highly Sensitive Piezoelectric Ultrasonic Microsensors

Buckling of multilayered diaphragm structures was analytically investigated and its results were utilized for new designs of the structure. Sensitivity of ultrasonic microsensors on piezoelectric diaphragm structure is enhanced by an adequate buckling of the diaphragm caused by the stress combination of the multilayered structure. One dimensional multilayered beam was modeled for the analysis, and three kinds of strains caused by residual stress, bending deformation and lateral stretching by buckling were taken into account in the analysis. The analytical buckling behavior was in good agreement with experimental results from the viewpoints of buckling limit stress and buckling deflections. As new designs of the structure, thickness of a compressive stress layer or of a tensile stress layer was varied. Thicker compressive layer acted as an enhancer for the buckling owing to larger in-plain expanding force rather than a reducer for the buckling due to larger rigidity against bending.