Non-invasive measurements of damage of frescoes paintings and icon by laser scanning vibrometer: experimental results on artificial samples and real works of art

摘要

Frescoes and icons show analogies in terms of defects, both present layer-to-layer detachments and delaminations and surface cracks; the aim of this work is to develop a diagnostic system for the measurement of the defects position and size. After initial measurement set-ups based on accelerometers and impact hammers a novel system based on laser vibrometers and acoustic stimulation of structures to allow full remote and contactless investigation of detachments and delaminations has been developed.This paper presents a measurement procedure based on two subsequent scans of the work of art is employed; the first scan aims at finding defects positions the second one to characterize their resonant response.A new kind of exciters, namely piezo actuators, has been introduced in the measurement chain and its effectiveness in finding defects in icons will be demonstrated. Also an on field measurement session on large sample walls will be described along withthe results obtained that show how efficient this technique has become.