| Summary: | 碩士 === 國立中興大學 === 森林學系所 === 104 === The purpose of this study is that using the stress-wave tomography technique, tapping resonance method, the growth cone sampling and other non-destructive testing to evaluate the soundness of standing China-fir in Hui Sun Forest. And to explore the accuracy of this method, as well as non-destructive testing for the relevant mechanical properties of materials, for reference of China-fir plantation thinning in the future.
The results show that the transverse stress between healthy China-fir velocity 1500 m/s or more, and velocity less than 1300 m/s who is considered defective fir. Radial and tangential stress-wave velocity ratio was about 1.0. Using this method to assess the rate of decay of China-fir has excellent performance, R2 value about 0.86. The FD values measured by tapping resonance method should be higher than 240. However, the results may be affected by bark. Using stress-wave tomography technique to assess the rate of decay of China-fir has objective and accurate results, the correlation was about 0.90. In addition, with transverse stress wave velocity to assess MOR (Modulus of Rupture), can really accurately assess material changes in the nature of the premises R2 value about 0.8. Tomography average velocity of each area to assess the compression strength, the correlation was about 0.77. Finally, the sawing yield of overall China-fir about 34%. The sawing yield of healthy fir about 36-39%. The sawing yield of decay fir about 30%.
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