On propagation characteristics of ultrasonic guided waves in helical strands

Steel strands have been widely used in industrial fields as a reliable load-bearing component. Under the influence of environmental erosion and fatigue stress, different types damage, such corrosion fracture, will occur in-service steel strands, which cause unpredictable loss personnel property. Ultrasonic nondestructive testing technology has become an ideal method for long-distance metal structures recent years due to advantages long detection distance high efficiency. The effect ultrasonic largely depends on propagation characteristics selected guided wave modes. However, helical structure contact between wires, waves are very complicated. In this paper, analyzing dispersion based Floquet boundary conditions (Floquet BCs) is proposed. essence mutual transformation principle solution vibration solution. To adapt paper proposes coordinate system twisted deduces corresponding wavenumber conversion formula. results BCs consistent with semi-analytical finite element sweep frequency modeling method, proves correctness BC from both theoretical experimental perspectives. This provides new idea complex waveguides strands.