One-sided Liquid Coupled Ultrasonic Method for Recovery of Third Order Elastic Constants

Ultrasonic measurements for experimentally determining third order elastic constants (TOECs) typically utilize multiple setups for bulk waves with directions of propagation parallel and perpendicular to the direction of applied stress. Experiments can be tedious and may require access to both sides of a specimen, which can be problematic in field applications for propagation parallel to the loading direction. Shown here is an alternative ultrasonic technique which utilizes an angle beam method whereby transducers are mounted on the same side of a parallel faced specimen. The general theory of acoustoelasticity for homogeneous and isotropic materials is used to derive acoustoelastic constants for propagation at an angle to the principal stress directions. TOECs are then estimated utilizing one shear vertical and two longitudinal angle beam measurements in an oil coupled or floating configuration. Experimental results are shown for aluminum 7075 and compared to published TOEC values. A sensitivity analysis is performed to understand how small variations in all input parameters affect the accuracy of the recovered third order elastic constants.