COMPARISON OF THE EFFECTS OF APPLIED LOADS AND TEMPERATURE VARIATIONS ON GUIDED WAVE PROPAGATION

摘要

Most guided wave-based damage detection methods for structural health monitoring rely upon detecting small damage-induced changes in ultrasonic guided wave signals. However, the structure of interest is generally exposed to variable loads and temperatures during normal usage, and received signals can be significantly affected. These signal changes are of concern because of their potential to cause false alarms during in situ monitoring. Load-induced signal changes are similar in some respects to those caused by temperature variations because both cause changes in bulk wave speeds and specimen dimensions. However, load-induced changes, unlike temperature changes, can produce a slight anisotropy of the structure, causing the changes in velocities to depend on the direction of propagation. Here we present experimental results that show the anisotropic effect of applied loads on the direct arrivals of various Lamb wave modes and compare that to both theory and to the isotropic effect of temperature.