利用超声波无损检测评估不同等级足尺规格材弯曲性质(英文)

Assessment of flexural properties of different grade dimension lumber by ultrasonic technique

参照加拿大锯材目测分等规则, 将人工林杉木(Cunninghamia lanceolata (Lamb.) Hook.)足尺规格材45mm×90mm×3700mm)分成SS, No.1, No.2和No.3四个等级。利用超声波无损检测法获得动态弹性模量,同时参照ASTM D198-99 标准测试了其静态抗弯弹性模量与抗弯强度。探讨了不同等级的动态弹性模量与静态抗弯弹性模量和抗弯强度之间的相互关系,进一步比较不同等级静态抗弯弹性模量和抗弯强度。研究结果表明,不同等级动静态弹性模量的相关性不同,其决定系数(R2)依次分别是0.616(No.2)、0.567(SS)、0.366(No.1)和0.137(No.3),不同等级动静态模量与抗弯强度的相关性也不一样,对每个等级而言,静态抗弯弹性模量与抗弯强度相关性好于动态弹性模量与抗弯强度的相关性。No.2等级以上的规格材动态弹性模量与静态弹性模量和抗弯强度的相关性很好,可以通过动态弹性模量预测规格材的弯曲性质;No.3等级的相关性较差,但都在0.01水平上具有显著的相关性;不同等级的动静态抗弯弹性模量和抗弯强度不等,No.2等级的静态抗弯弹性模量值最大,其次分别是SS、No.1和No.3,依次分别为:10.701GPa、10.359GPa、9.840GPa和9.554GPa;对同一等级规格材的动态弹性模量大于静态抗弯弹性模量;同样抗弯强度也是No.2等级的最大为48.67MPa, 其次是SS48.16MPa),然后是No.3(46.55MPa),最小的是No.1(43.39MPa)。

The dimension lumber （45mm×90mm×3700mm） of plantation Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） was graded to four different classes as SS, No. 1, No.2 and No.3, according to national lumber grades authority （NLGA） for structure light framing and structure joists and planks. The properties of apparent density was determined at 15% moisture content, bending strength and stiffness were tested according to American Society for Testing and Materials （ASTM） D198-99, and dynamic modulus of elasticity （Eusw） was measured by ultrasonic technique, for predicting the flexural properties of different grade lumbers. The results showed that Eosw was larger than the static MOE. The relationship between Eusw and static MOE was significant at 0.01 level, and the determination coefficients （R2） of the four grade lumbers followed the sequence as R^2No.2 （0.616）〉 R^2ss （0.567）〉 R^2No1 （0.366）〉 R^2No.3 （0.137）. The R^2 of Fusw and MOR were lower than that of the Etru and MOR for each grade. The Eusw of all the grade lumbers, except No.3-grade, had significant correlation with the static MOE and MOR, thus the bending strengthof those grade lumbers can be estimated by the E The Etru valuesof four grade lumbers followed a sequence as No.2-grade （10.701 GPa） 〉 SS-grade （10.359 GPa） 〉 No.l-grade （9.840 GPa） 〉 No.3-grade （9.554 GPa）. For the same grade dimension lumber, its Eusw value was larger than static MOE. Mean values of MOR for four grade lumbers follow a sequence as No.2-grade （48.67 MPa） 〉 SS-grade （48.16 MPa） 〉 No.3-grade （46.55 MPa） 〉 No. 1-grade （43.39MPa）.