Abstract
Adhesive bonding has become increasingly important in many industries. Non-destructive inspection of adhesive joints is essential for the condition assessment and maintenance of a structure containing such joints. The aim of this paper was the experimental investigation of the damage identification of a single lap adhesive joint of metal plate-like structures. Nine joints with different defects in the form of partial debonding were considered. The inspection was based on ultrasonic guided wave propagation. The Lamb waves were excited at one point of the analyzed specimen by means of a piezoelectric actuator, while the guided wave field was measured with the use of a laser vibrometer. For damage imaging, the recorded out-of-plane vibrations were processed by means of the weighted root mean square (WRMS). The influence of different WRMS parameters (i.e., the time window and weighting factor), as well as excitation frequencies, were analyzed using statistical analysis. The results showed that two-dimensional representations of WRMS values allowed for the identification of the presence of actual defects in the adhesive film and determined their geometry.
Highlights
Adhesive joints of metal elements are a kind of non-separable connections with numerous applications, e.g., in the aviation, machine, or automotive industry [1]
This study presents an approach to the damage identification of adhesively bonded joints that is based on the Lamb wave propagation
Before analyzing the defects in the lap joints, the characteristics of Lamb waves were determined for two specimens: a single steel plate with a thickness of 3 mm and dimensions of 240 mm × 300 mm, and two steel plates that were adhesively bonded with an adhesive layer with a thickness of 0.2 mm
Summary
Adhesive joints of metal elements are a kind of non-separable connections with numerous applications, e.g., in the aviation, machine, or automotive industry [1]. The strength and durability of adhesive joints are essential for the safety of engineering structures. They are highly susceptible to any defects resulting from mistakes that were committed during the preparation and joining of elements, e.g., poor condition of the adherend surface or a lack of glue on a part of the overlay. Destructive testing provides very accurate results [1] This approach allows for the determination of the influence of certain parameters (e.g., damage existence [2,3] or adhesion condition [4]) on the strength of representative samples, which were usually prepared in laboratory conditions and to predict the state of existing joints
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