- 期刊
杉木原木材質對製材率與機械性質之影響－以惠蓀林場52年生杉木為例
Effect of the Log Quality on Yield and Mechanical Properties of China Fir (Cunninghamia lanceolata) - A Case Study for 52- Year-Old China Fir Plantation in Huisun Experimental Forest
摘要
本研究主要係針對惠蓀林場52年生杉木進行製材利用率之分析，評估其材質健全度對製材利用率之影響。同時藉抗彎與抗壓等力學性能試驗結果，輔以結合應力波斷面影像技術所計算之平均應力波速值，進行木材力學性能及與應力波速值之相關性分析。研究結果指出，健全杉木之中原木與大原木，經製材鉋光後之壁板材平均製品製材利用率分別為41.6%與43.9%，顯示隨原木徑級之增加，其製品製材利用率有提升之趨勢。而心材腐朽之杉木原木，經製材鉋光後之壁板材平均製品製材利用率為28.4%，隨腐朽率之增加，其製品製材利用率則隨之下降。另一方面，健全杉木之平均抗彎彈性模數與抗彎強度值分別為8.5 GPa及73.9 MPa，而具心材腐朽之杉木，其平均抗彎彈性模數與抗彎強度值則分別為6.4 GPa及57.6 MPa，均較健全者為低。然無論係健全或腐朽之杉木原木，利用應力波斷面影像技術所計算之平均應力波速值與其平均之抗彎彈性模數與抗彎強度值間均具有良好之相關性，r值分別為0.94及0.84。而其與抗壓強度間亦具有良好之相關性，健全材與心材腐朽者之r值則分別為0.88與0.85。另依普通結構材之長期容許應力誘導方法計算本研究杉木之長期抗彎與抗壓容許應力分別為7.5 MPa與5.7 MPa。
並列摘要
The main purpose of this study was to analyze the sawing yield of 52-year-old China fir (Cunninghamia lanceolata) plantation wood in Huisun Experimental Forest, and the effect of log quality on the sawing yield was also evaluated. Besides, the relationships between the bending strength, compression strength and average stress wave velocity calculated by the stress wave tomography were also investigated. The experimental results showed that planned volume yield of the healthy medium-sized (Diameter: 14-30 cm) and big-sized (Diameter: ＞ 30 cm) were 41.6% and 43.9%, respectively. The result also indicated that the volume yield of the healthy logs increased with the increasing diameter of the logs. In addition, the average volume yield of the planned decayed logs was 28.4%, and with the increasing decayed ratio, the volume yield of the decayed logs decreased. On the other hand, the average MOE and MOR value of the healthy logs were 8.5 GPa and 73.9 MPa, respectively. The bending performance of the decayed China fir logs were lower than those of the healthy ones, the average MOE and MOR were 6.4 GPa and 57.6 MPa, respectively. In addition, a well defined relationship between the stress wave velocity and the bending performance of China fir wood was also found, the r value for the MOE and MOR were 0.88 and 0.71, respectively. Moreover, there was also a good correlation between the stress wave velocity and the compression strength of the healthy and decayed China fir wood, the r value for the healthy wood and decayed wood were 0.88 and 0.85, respectively. According to the long-term allowable stress design calculating of common structural lumber, the values for bending and compression strength in this study were 7.5 MPa and 5.7 MPa, respectively.