Lumber moisture evaluation by a reflective cavity photothermal technique

Abstract

Photothermal methods constitute a convenient approach for the nondestructive quality control of industrial materials because they are rapid and noninvasive. One such application is the monitoring of moisture in unseasoned lumber for drying mill process control. This paper describes a photothermal method for the analysis of moisture in wood by measuring its surface temperature rise under laser radiation. It is shown that this parameter is much more sensitive than thermal diffusivity to moisture content variations. A reflective cavity technique is used to increase both the absorptivity and the emissivity of the inspected surface in order to improve the measurement reliability. Results obtained with an off-center hemispherical cavity on wood samples of different moisture content are presented and discussed

Subsurface Flaw Detection In Reflective Materials By Thermal-Transfer Imaging

“…b) shows some results obtained on the aluminum panel over a 2.5 cm diameter, 1 mm depth (aluminum skin) defect (artificially induced lack of epoxy at the foam interface) and on the plexiglas plate (drilled hole 1 cm in diameter and 1 6. mm in depth).…”