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|標題:||Property of wood-based materials tested by ultrasonic|
|摘要:||The purpose of this study was to apply the nondestructive ultrasonic wave to test the ultrasonic velocity of wood and wood based materials, and to use destructive universal testing machine to test their strength.
The finding of this study were summarized as follows:
Ultrasonic velocity is increased with the density of the increased particleboard. The coefficients of determination (R2) of the regression analysis between density and longitudinal wave and between density and surface wave were 0.93 and 0.92, respectively. However, the density and ultrasonic velocity of solid wood showed that they had no relations because of the structure of solid wood.
Fiber angle of wood affected the transport velocity of ultrasonic. Also, the velocity is decreased with fiber being angle increased. Producing flow direction of merchant particleboard and fiberboard had a little impact on ultrasonic velocity. That was to say, the directionality of panels wasn't obvious. Surface layer direction of plywood had also a little impact on ultrasonic velocity.
The velocity of longitudinal wave is decreased with the increased specimen length, but the relationships among them were not obvious. When the length of specimen was longer than 15cm, velocity of surface wave is increased with the increased specimen length, and the relationships among them were not obvious, either. The relationships between thickness and ultrasonic velocity of particleboard and fiberboard were not obvious, but the ultrasonic velocity of plywood is decreased with the increased thickness.
The ultrasonic was applied to test the mechanical property of wood based panels. The relationship between MOE and the velocity of longitudinal wave or surface wave was statistically significant, and R2 values of them are 0.86 and 0.85, respectively. The relationships between MOR and their velocities were also statistically significant, and their R2 values were 0.84 and 0.83, respectively. IB specimen was tested with longitudinal wave which frequency was 40 and 100 KHz, and R2 values of them are 0.74 and 0.75, respectively.
Based the result of this study, it showed that the ultrasonic was not suitable to test the artificial defect with hole, if the wavelength was larger than the size of artificial defected hole. As the results mentioned above, results applied to test in wood based panels of longitudinal wave and surface wave were similar. These results showed the longitudinal wave and surface wave could cooperate with each other.|
本研究以非破壞性的超音波探測儀檢測材料的波速，且利用破壞性的萬能試驗機檢測木質板材的強度性質，其結果摘述如下。 超音波波速隨粒片板密度增加而加快，密度與縱波的判定係數為0.93；與表面波為0.92；然而實木由於結構之關係，實驗中，實木的密度與超音波波速沒有形成規律的關係。 木材纖維角度影響超音波的傳遞速度，隨纖維角度的增加而波速逐漸減慢；市售粒片板與纖維板的生產流程方向對超音波波速影響不大，亦即板材的方向性不明顯；合板的表層纖維方向對超音波波速的影響不大。 縱波會隨試材長度增加而減慢，但其關係不顯著；表面波在試材長度大於15 cm時，卻隨著試材長度增加而增加的趨勢，其關係一樣不顯著。縱波及表面波與粒片板及纖維板之厚度關係不顯著，而合板方面，縱波及表面波隨試材厚度增加而減慢。 實驗設定的缺點大小對超音波傳遞速度的影響不大，而實驗中使用的超音波頻率為40KHz，屬於較低頻的超音波，穿透力較強，或許因此波速對於孔洞的檢測較不靈敏而不適用於板材的缺點檢測。 超音波應用於力學性質之檢測上，縱波及表面波與MOE之關係顯著，其R2分別為0.86及0.85；與MOR之關係亦顯著，其R2分別為0.84與0.83；而在IB方面，以40與100KHz之縱波檢測，R2分別為0.74與0.75。 經由上述的結果觀之，縱波與表面波應用在木質板材的檢測上，除在試材長度與厚度的結果不同外，其餘的結果均相似。這樣的結果顯示兩者可彼此相互印證，配合應用。
|Appears in Collections:||森林學系|
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