3种无损检测方法评估巨尾桉木材抗弯和抗压强度性质

为探讨不同无损检测方法评估木材强度性质的可行性及可靠性，该文分别运用纵向基频振动、超声波和应力波3种无损检测方法，对由广西东门林场采集的34株14年生巨尾桉人工林加工的191个无疵小试样进行了抗弯和抗压强度性质预测。首先采用3种无损检测设备获得无疵小试样的动态弹性模量，然后进行抗弯弹性模量（MOE）、抗弯强度（MOR）和顺纹抗压强度（σc）的测定，并分析3种无损检测结果与木材强度性质的关系。结果表明:纵向基频振动法、超声波法和应力波法获得的动态弹性模量Efr、Eus和Esw与静态MOE的相关系数分别为0.816 6、0.788 9和0.634 7，均在0.001水平上显著相关；与MOR的相关系数分别为0.694 0、0.683 0和0.567 3，均在0.001水平上显著相关；与σc的相关系数分别为0.810 3、0.809 3和0.648 9，均在0.001水平上显著相关；其中应力波法测得的动态弹性模量Esw与木材强度性质的相关系数均为最低。可见，纵向基频振动法和超声波法能够比较精准地预测国标无疵小试样的MOE、MOR和σc，但应力波方法对无疵小试样进行测定时具有一定局限性。 

Evaluating bending and compressive strength properties of Eucalyptus grandia x E.urophylla plantation wood with three nondestructive methods

The objective of this study is to compare three nondestructive methods for evaluating the bending modulus of elasticity (MOE)，modulus of rupture (MOR) and compressive strength parallel to grain (σ_c) of Eucalyptus grandia×E. urophylla plantation wood. Thirty four Eucalyptus plantation trees at 14 years old were selected in Dongmen Forest Farm，Guangxi Zhuang Autonomous Region, southern China. All the sample trees were cut into 191 small clear specimens，for which three dynamic modulus of elasticity，ie longitudinal vibration (E_fr)，ultrasonic wave (E_us) and stress wave (E_sw)，were measured in the air dry condition. Static bending and compressive strength tests were then performed to determine the MOE，MOR and σ_c. The correlation coefficients obtained in this study were 0.816 6，0.788 9 and 0634 7 respectively between dynamic MOE (Efr，Eus and E_sw) and static MOE (P<0.001). Meanwhile，the correlation coefficients were 0.694 0，0.683 0 and 0.567 3 between dynamic MOE (E_fr，E_us and Esw) and MOR (P<0.001). The correlation coefficient between dynamic MOE (E_fr，E_us and E_sw) and σ_c were 0.810 3，0.809 3 and 0.648 9 (P<0.001). The results showed that the correlations between E_sw based on stress wave method and wood strength properties was the lowest in comparison with longitudinal vibration and ultrasonic wave method. This study also indicates that the longitudinal vibration and ultrasonic wave could provide accurate predictions of the bending properties and compressive strength of small clear specimens prepared in accordance with Chinese national standard. On the other hand，stress wave method has more limitation for anticipation on the mechanical properties of small clear specimens.