柳杉是臺灣主要的造林與經濟樹種之一，為一種天然材料。由於木材不同於一般人造材料，當柳杉由原木製成木材時，每一木材皆獨一無二，所以世界上沒有完全一模一樣之木材。本論文利用臺灣柳杉製成木材之表面特徵以微觀、細觀與巨觀多尺度探討木材之機械行為。
　　木材表面有不同的特徵，為了能從橫截面得到年輪資訊，本論文發展了數位影像分析（Digital Image Analysis, DIA）法以取代X射線密度（X-ray Densitometry, XrD）法來量測木材之晚材比例。由於年輪結構與疊層材料結構相似，本論文以混合規則（Rule of Mixtures）為基礎，發展年輪分析（Annual Ring Analysis, ARA）法與改良年輪分析（Modified Annual Ring Analysis, MARA）法來計算木材之彈性模數（Modulus of Elasticity, MOE）。本論文發現久為林業學者使用之莫克準則 (Mork Criterion, MC) 僅適用於過渡帯（Transition Zone）不明顯的歐洲與北美樹種，依據本論文針對臺灣柳杉之實驗結果，臺灣柳杉之早材（Earlywood, EW）、過渡帶與晚材（Latewood, LW）區域應使用本論文所提出的修正MC範圍，即分別為MC ≤ 0.3、0.3 < MC < 0.75與 MC ≥ 0.75。此外，木材之弦切面與徑切面具有紋理與節點之特徵，本論文根據管胞效應（Tracheid effect）研發三維（Three-dimensional, 3D）纖維方向掃描系統 (Fiber Orientation Scanning System, FOSS) 以量測木材表面之纖維方向。本論文進一步提出了密度與纖維方向（Density and Fiber Orientation, DFO）法來預測木材之MOE。在DFO法中，首先應用纖維潛入角結合線性內插法來預測節點體積，以決定柳杉之無節材(Clear Wood)與節點之密度比例 (Knot Density Ratio, KDR)。同時，根據KDR提出無節材KDR (KDR_Clear Wood, KDRCW)法以求得木材無節區域之密度，並進一步結合無節區之木材密度與纖維方向來預測木材之全域MOE。
　　由年輪實驗結果可知DIA法是一有效可分析年輪晚材比例的方法，ARA與MARA法重新定義了早材、過渡帶與晚材之區域，而可正確計算無節材的MOE。DFO法不僅能預測木材之MOE，且可決定KDR，以求得木材無節區之密度。由柳杉之年輪微觀分析、小試片之細觀分析與巨觀尺度下之直交式集成板 (Cross Laminated Timber, CLT) 之推倒實驗均可瞭解年輪、密度、纖維方向與節點確實影響木材之機械性質。
　　本論文透過木材表面特徵進行多尺度木材機械行為之研究，期能正確的預測木材品質並改善國產木材結構件之安全。未來，在提高國產木材自給率後，本論文之研究成果有助於木材分等自動化與產業升級，藉此增加臺灣林產業之國際競爭力。

Japanese cedar (Cryptometria japonica), a kind of natural material, is one of the major species for afforestation and economy in Taiwan. Unlike man-made materials, every and each timber itself is unique after the wood log was manufactured into timbers. There is no entirely the same timber to each other in the world. In this dissertation, by using the surface characteristics, multiscale mechanical behavior of the timber was investigated from the microscopic, mesoscopic to macroscopic scales.
There are different characteristics on surfaces of the timber. To obtain annual ring information from cross-sectional surface, the digital image analysis (DIA) method was developed to replace the X-ray densitometry (XrD) method to measure the proportion of latewood. Since the structure of the annual ring is similar to that of laminated materials, based on the rule of mixtures, the annual ring analysis (ARA) and the modified annual ring analysis (MARA) methods were developed in this dissertation to calculate the modulus of elasticity (MOE) of clear wood timber.
Based on the experimental findings of this dissertation, the widely used Mork criterion (MC) was found valid only for wood species with indistinct transition zone generally found in Europe and North America. For the Japanese cedar in Taiwan, the modified MC (i.e. MC ≤ 0.3, 0.3 < MC < 0.75, and MC ≥ 0.75) was proposed in this dissertation to define earlywood, transition zone, and latewood.
In addition, the characteristics of grain and knot were found on the tangential and radial surfaces of the timber. Based on the tracheid effect, a three-dimensional (3D) fiber orientation scanning system (FOSS) was developed to measure the fiber orientations on surfaces of the timber. The density and fiber orientation (DFO) method was further proposed to predict the MOE of the timber. In the DFO method, the diving angle combined with linear interpolation was used to predict the knot volume to determine the knot density ratio (KDR). The KDR_Clear wood (KDRCW) method was proposed in this dissertation to calculate the density of clear wood region of the timber. The global MOE was predicted by combining the density of clear wood region and fiber directions of the timber.
With the experimental results obtained from the annual ring analysis, the DIA method was proved to be an effective method to analyze the proportion of latewood. By employing ARA and MARA methods, the MOE of the clear wood region can be accurately calculated by using the newly defined regions of earlywood, transition zone and latewood. were successfully used to calculate the MOE of clear wood timber. The DFO method can be used to predict MOE and calculate the KDR so that the density of clear wood region can be determined. Based on microscopic and mesoscopic analysis of timbers as well as the macroscopic scale cross-laminated timber (CLT) push-over test, it was found that the mechanical behavior of the timber is affected by the annual ring, density, fiber orientation, and knot.
By implementing the results of multi-scale investigation of mechanical behavior by using surface characteristics of the wood, it is expected that the accuracy of the quality prediction of the timber and the safety of the wood structure can be improved. In the future, after improving the self-sufficiency rate of domestic wood produce, the international competitiveness of wood industry of Taiwan is expected by automation of timber grading and upgrading of industrial level.

CONTENTS viii
LIST OF TABLES xiii
LIST OF FIGURES xv
CHAPTER 1 INTRODUCTION 1
1.1 Background 1
1.2 Motivation 3
1.3 Objectives 5
CHAPTER 2 LITERATURE REVIEW 8
2.1 Introduction of wood 8
2.2 Methods for measuring characteristics on surfaces of timber 11
2.3 Digital image correlation method 12
2.4 Tracheid effective method 14
2.5 Methods for mechanical grading of wood 16
CHAPTER 3 EXPERIMENTAL METHODS 19
3.1 The DIC Method 19
3.2 The XrD method 21
3.3 The DIA method [22] 22
3.3.1 Feasibility analysis of the DIA method 23
3.4 The tracheidogram method 26
3.5 Annual ring analysis method for calculating MOE of clear wood timber 29
3.5.1 The ARA method 29
3.5.2 The MARA method 30
3.6 The DFO method 32
3.6.1 The tracheid effect method 33
3.6.2 The ellipse shape determination 34
3.6.3 Determining the in-plane and diving angles 36
3.6.4 Determination of knot volume 37
3.6.5 Determination of the density of clear wood region of timber 38
3.6.6 Orthotropic material mechanics of timber 39
3.6.7 Determination of predicted global MOE 45
CHAPTER 4 EXPERIMENTAL PROCEDURES 47
4.1 The wood species and specimens 47
4.2 Experiments to obtain mechanical properties 49
4.2.1 Strain measurement 49
4.2.2 Tensile test 51
4.2.3 Shear test 52
4.2.4 Static bending test 53
4.2.5 The push-over test 55
4.3 Experimental procedures for the annual ring analysis method 56
4.3.1 The XrD method 56
4.3.2 The DIA method 58
4.3.3 The tracheidograms method 59
4.4 Experimental procedure for the DFO method 62
4.4.1 Density measurement 62
4.4.2 Development of the 3D FOSS 64
4.4.2.1 Optical system 64
4.4.2.2 Three-axis displacement platform 65
4.4.2.3 Software development of the 3D FOSS 65
4.4.3 Reliability of measurement 67
CHAPTER 5 RESULTS AND DISCUSSIONS 69
5.1 Mechanical properties of Japanese cedar 70
5.1.1 Young’s moduli 70
5.1.2 Poisson’s ratios 73
5.1.3 Shear moduli 75
5.1.4 Static bending MOE and modulus of rupture 77
5.2 Results of fracture behavior 78
5.3 Results of annual ring analysis 82
5.3.1 Results of the DIA method 82
5.3.2 Results of the ARA method 84
5.3.3 Results of the MARA method 85
5.3.4 Comparison of the ARA and MARA methods 87
5.4 Parameters determination of the 3D FOSS 88
5.4.1 Relationship between diving angle and shape factor 88
5.4.2 Determination of 89
5.5 Predicted global MOE results of clear wood specimen 90
5.6 Results of 91
5.7 Results of the timber with a knot 92
5.8 Results of push-over test of CLT shear wall 94
CHAPTER 6 CONCLUSIONS 97
CHAPTER 7 FUTURE WORK 100
BIBLIOGRAPHY 102
APPENDIX A LIST OF ABBREVIATIONS AND ACRONYMS 248
APPENDIX B LIST OF SYMBOLS 251
A. Roman letters 251
B. Greek symbols 254

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