Abstract
In the electromechanical impedance (EMI) method, the PZT patch performs the functions of both sensor and exciter. Due to the high frequency actuation and non-model based characteristics, the EMI method can be utilized to detect incipient structural damage. In recent years EMI techniques have been widely applied to monitor the health status of concrete and steel materials, however, studies on application to timber are limited. This paper will explore the feasibility of using the EMI technique for damage detection in timber specimens. In addition, the conventional damage index, namely root mean square deviation (RMSD) is employed to evaluate the level of damage. On that basis, a new damage index, Mahalanobis distance based on RMSD, is proposed to evaluate the damage severity of timber specimens. Experimental studies are implemented to detect notch and hole damage in the timber specimens. Experimental results verify the availability and robustness of the proposed damage index and its superiority over the RMSD indexes.
Highlights
In recent several decades, many nondestructive detection (NDD) techniques have been extensively applied to metal and concrete materials
By analyzing the calculation procedure of Mahalanobis Distance (MD) based on root mean square deviation (RMSD), it can be found that the inverse matrix of S is highly ill-conditioned resulting in instability of the MD results
Damage index, MD based on RMSD, is proposed to evaluate the damage severity of test specimens
Summary
Many nondestructive detection (NDD) techniques have been extensively applied to metal and concrete materials. Studies on NDD of timber is rarely reported in the literature, while timber is one of the most popular construction materials in many countries. Since local damages such as hole, decay, and crack caused by the adverse environmental influence and external loads extensively exist in wooden structures, reliable damage detection techniques for timber or wooden structures are heavily needed. Philipp and Thomas [8] recently reviewed existing feasible methods to assess the integrity of glue-laminated timber elements. While a few of abovementioned methods can, somehow, quantitatively assess any damage, the majority of them can only provide qualitative information
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