High-Temperature Drying and Equalizing: Effects on Stress Relief in Yellow-Poplar Lumber

Warp caused by longitudinal growth stress has limited the use of hardwoods for some products such as structural lumber. This study evaluates the effects of high-temperature drying and equalizing times on relief of longitudinal growth stress. Small-diameter yellow-poplar logs were sawn into flitches for evaluation of total stress levels in green flitches and final stress levels in dried flitches.High temperatures evaluated were 200 F (93 C), 240 F (116 C), 260 F (127 C) and 290 F (143 C). Equalizing times were 10, 20, 40, and 100 hours at 10% equilibrium moisture content.Average adjusted absolute stresses for center flitches in the green conditions were about 525 psi (362 MPa). Average absolute stresses were 210 psi (145 MPa) for all high-temperature dried materials without equalizing, and 154 psi (106 MPa) for all equalized materials.There were no well-correlated relationships of stress between the individual high-temperature or equalizing treatments and controls or green flitches. Possible causes for lack of correlation and suggestions for further research are discussed