Grid-Based Tactile Sensor System for Shrinkage Pressure Measurement
Keywords:Drying stresses, shrinkage pressure, casehardening, sensor, red oak, loblolly pine
A study was conducted to determine the applicability of a grid-based tactile pressure sensor system in monitoring the shrinkage pressure in wood during drying. The sensor was attached to green red oak (Quercus sp.) and loblolly pine (Pinus taeda L.) boards through a mortise fitted with a two-piece metal insert. As current sensor models could not withstand actual kiln-drying temperatures, the boards were allowed to dry under room conditions (70°F and 60% RH).
Results indicate that the pressure sensor system could accurately monitor the shrinkage pressure within the sample boards. Frame-by-frame recordings of the pressure profile across the loaded sensor grids showed not only a visual manifestation of the stress development and reversal phenomena in drying, but also the magnitudes of the internal compressive stresses. For the first time, both real-time visual graphics and quantitative data on compressive 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 simultaneously with the compressive stresses.
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