應用非破壞檢測技術評估杉木集成元之抗彎性質

Evaluation of Bending Properties of China fir Laminae Using Nondestructive Testing

本研究利用目視分等法、超音波法、打音法及抗彎試驗法評估國產2 by 6與2 by 8之杉木集成元之動彈性模數與抗彎彈性模數之相關性。試驗結果指出，依CNS14630分等法，抗彎彈性模數方面有一級材＞二級材＞三級材之趨勢，但經變異數分析則顯示僅一級材與三級材有差異；另依CNS14631分等法下，2by6集成元之抗彎彈性模數值依序為特級材＞一級材＞三級材＞二級材；2 by 8集成元之抗彎彈性模數值依序為特級材＞二級材＞三級材＞一級材，但各等級間均無顯著差異，因此目視分等等級材其強度上並不如機械分等材精確。在動彈性模數方面，超音波動彈性模數（DMOEv）與打音動彈性模數（DMOEf）均較抗彎彈性模數（MOE）為大，而以打音動彈性模數最為接近，比較其關係式雖彼此均有正相關存在，但以打音動彈性模數與抗彎彈性模數之關係性最佳（R^2=0.82-0.90），因此以打音法所得之動彈性模數來作為評估杉木集成元之抗彎彈性模數較為適當。 The purpose of this study was to investigate the dynamic and static bending properties of 2-by 6-inch and 2-by 8-inch China fir laminae using nondestructive techniques, including visual grade method, ultrasonic wave method, tap tone method and static bending test. In addition, the DMOEv which was dynamic MOE from ultrasonic wave method, DMOEf which was dynamic MOE from tap tone method and MOE which was from static bending test were calculated, respectively. The results indicated that the MOE values of 2-by 6-inch and 2-by 8-inch laminae have the tendency of Class1 ＞ Class2 ＞ Class3 according to CNS14630, the visual grading method. In addition, there was a significant difference between Class1 and Class 3. However, there was no significant difference among the MOE values of the four laminae grades by CNS 14631, the visual grading method. Most of the criteria used in the visual grading of the lumber were not closely correlated with specific properties, therefore, visual grading was not as precise as machine stress rated. The results also showed that the dynamic MOE of lumber was greater than that the static MOE of lumber, however, the values of DMOEf were very close to those of MOE. There were high correlations among the DMOEv, DMOEf and MOE, especially between the DMOEf and MOE (R^2 = 0.82-0.90). Hence, the tap tone method was a better approach to determine the static MOE of lumbers.

The purpose of this study was to investigate the dynamic and static bending properties of 2-by 6-inch and 2-by 8-inch China fir laminae using nondestructive techniques, including visual grade method, ultrasonic wave method, tap tone method and static bending test. In addition, the DMOEv which was dynamic MOE from ultrasonic wave method, DMOEf which was dynamic MOE from tap tone method and MOE which was from static bending test were calculated, respectively. The results indicated that the MOE values of 2-by 6-inch and 2-by 8-inch laminae have the tendency of Class1 ＞ Class2 ＞ Class3 according to CNS14630, the visual grading method. In addition, there was a significant difference between Class1 and Class 3. However, there was no significant difference among the MOE values of the four laminae grades by CNS 14631, the visual grading method. Most of the criteria used in the visual grading of the lumber were not closely correlated with specific properties, therefore, visual grading was not as precise as machine stress rated. The results also showed that the dynamic MOE of lumber was greater than that the static MOE of lumber, however, the values of DMOEf were very close to those of MOE. There were high correlations among the DMOEv, DMOEf and MOE, especially between the DMOEf and MOE (R^2 = 0.82-0.90). Hence, the tap tone method was a better approach to determine the static MOE of lumbers.