Detecting Compression Wood in Green Loblolly Pine with Radio Frequency

Compression wood is formed on the lower side of leaning softwood trees stem. High density and high microfibril angle lead to a very high longitudinal shrinkage compared to that of normal wood. This shrinkage leads to a high degree of warp and resultant value loss in lumber during drying. Detection of compression wood in green lumber would allow segregation of the lumber for special handling or product designation and reduce value loss from warpage during drying. A dielectric method was tested to differentiate compression from normal wood in green loblolly pine lumber. Compression wood produced a considerable increase in the phase shift of an applied radio frequency signal. A threshold value was determined, tested, and resulted in 95%, 100%, 95%, and 80% successful differentiation of compression from normal wood in lumber for 100, 500, 1000 and 5000 kHz frequencies, respectively.