Grid-based tactile sensor system for shrinkage pressure measurement

A study was conducted to determine the applicability of a grid-based tactil e pressure sensor system in monitoring the shrinkage pressure in wood durin g drying. The sensor was attached to green red oak (Quercus sp.) and loblol ly pine (Pinus taeda L.) boards through a mortise fitted with a two-piece m etal insert. As current sensor models could not withstand actual kiln-dryin g temperatures, the boards were allowed to dry under room conditions (70 de grees F and 60% RH). Results indicate that the pressure sensor system could accurately monitor t he shrinkage pressure within the sample boards. Frame-by-frame recordings o f the pressure profile across the loaded sensor grids showed not only a vis ual manifestation of the stress development and reversal phenomena in dryin g, but also the magnitudes of the internal compressive stresses. For the fi rst time, both real-time visual graphics and quantitative data on compressi ve drying stresses in wood are made available. The current sensor system is designed exclusively for measuring compressive stresses, and is incapable of monitoring the magnitude of the internal tensile stresses that occur sim ultaneously with the compressive stresses.