干燥过程中小径木表层应力的研究

采用连续加热和间歇加热(间歇2h和间歇6h)方式对小径木锯材进行常规干燥,研究了干燥过程中小径木的表层应力(全应力和残余应力)发生、发展变化规律.结果表明,随着试材的含水率降低,其表层全应力最初表现为拉应力,拉应力增大到最大值后,逐渐减小直至消失,然后转变为压应力,压应力达到最大值后,逐渐减小直到干燥结束;残余应力是先逐渐增大,达到最大后又减小;3种加热方式下,试材表层应力的变化趋势基本一致,但是试材的表层应力间歇加热的明显小于连续加热的,间歇6h试材的表层应力最小;同一含水率水平下,表层应力弦切板的比径切板大.

Study on surface layer stress of small-diameter wood during drying process

The small-diameter lumbers of Daimyo Oak(Quercus dentata) were dried with consecution-heat method and intermittent-heating methods(intermittent 2h and intermittent 6h) to study the occurred stress of surface layer of them during conventional drying process.The results show that the total stress was elongate stress at first,the elongate stress became large and got to the most,then became small and changed into compress stress,the compress stress became large and got to the most,and then became small,with the fall of moisture content of the lumber; the residual stress became large,and became small again after got to the most; the change of stress of surface layer with three kinds of heating methods were in a similar way.However,the stress with intermittent-heating was smaller than that with consecution-heat during either prophase drying or metaphase drying,and the stress was least with intermittent 6h.At the same moisture content level,the stress of surface layer of tangential lumber was larger than that of radial lumber.