Baseline-free absolute strain estimation for cylindrical structures

Abstract

The total strain induced by forces in a structure, known as absolute strain, provides crucial information about structural integrity. The unexpected variations in absolute strain can compromise the overall safety of the structural system. In this paper, a baseline-free absolute strain estimation technique is developed based on the acoustoelastic effect of ultrasonic guided wave for in-service cylindrical structures. To generate and sense ultrasonic guided waves, two macro-fiber composite (MFC) transducers were installed on the surfaces of cylindrical structures subjected to tensile force. Additionally, a strain gauge was used to measure the relative strain generated after installing the MFC transducers and the strain gauge. The absolute strain was estimated using the velocity of the ultrasonic guided waves and the relative strain, without the need for calibration tests and baseline data obtained from known absolute strain levels. The effectiveness of the developed technique was experimentally examined using blind data obtained from a hollow steel cylinder and an aluminum mooring cable from a submerged floating tunnel model.