Inspecting Marquetries at Different Wavelengths: The Preliminary Numerical Approach as Aid for a Wide-Range of Non-destructive Tests

The present study is based on the non-destructive inspection of two marquetries representing arms’ coats, which were produced by the Technical University in Zvolen (Slovakia) and tested under laboratory conditions. The aforesaid samples were made of traditional European and exotic wood species, while the veneers of the decorative layers were prepared through the technology cutting technique, emphasizing in such a manner the wooden texture. One sample was a defect-free panel, while the second one consisted of three sub-superficial flaws and one superficial putty insert, added during the manufacturing stage. The samples were inspected by different non-destructive techniques, such as visible imaging, ultraviolet testing, near-infrared reflectography and transmittography, infrared thermography, holographic interferometry, digital image correlation, laser speckle contrast imaging and ultrasonic testing. Sometimes a comparison was not performed, by avoiding unnecessary data processing. Numerical simulations focusing on the optimization of the provided thermal flux anticipated the experimental results. The latter analysis proved the necessity for the integration of experimental and numerical testing in similar case studies. A peculiarity of this work is the additional creation of an ad hoc Matlab® code, written under the LSCI conditions, which identifies the wooden texture. The interactive methodology applied in the present study verified the synergy of the selected inspection methods enabling the production of a complete view for the preservation state of the inspected marquetry samples, through the comparison and/or the correlation of the individual informative content produced by each inspection procedure.