Environmental and operational conditions effects on Lamb wave based structural health monitoring systems: A review.

• Lamb wave based SHM techniques are used to monitor the health status of structures. • Environmental and Operational conditions (EOCs) affect Lamb wave based SHM techniques. • This paper provides a review of EOCs effects on Lamb wave propagation in structures. • EOCs effects' compensation strategies for Lamb wave based SHM systems are also reviewed. • Moreover, baseline free damage identification techniques are briefly summarized. Lamb wave is widely recognized as one of the most encouraging tools for structural health monitoring (SHM) systems. In spite of many favourable characteristics of Lamb wave for SHM, real-world application of these systems is still quite limited. Beside the complexities derived from multi-modal, dispersive and multi-path characteristics of Lamb waves, one of the main challenges in Lamb wave based SHM is sensitivity of these systems to environmental and operational conditions (EOCs) parameters. This paper provides a state of the art review of the effects of EOCs parameters including: temperature, moisture, load, vibration and bonding (adhesive layer shear modulus and thickness, bond defects), on Lamb wave propagation. Moreover, this paper provides a summary of compensation strategies to account for EOCs effects as well as baseline free techniques. An objective is also to understand the future directions and areas requiring attention of the researchers. [ABSTRACT FROM AUTHOR]