Analysis of Stress Field Near Crack Tip Using Finite Element Method and Prediction of Cracking Direction for Wood Sample with Crack Applying Computerized Tomography(CT) to Study the Feature of Wood Fracture Fractal Feature of Wood Fracture with 3D Scanning Technologies STUDY ON THE COMPLIANCE METHOD FOR DETERMINE WOOD FRACTURE TOUGHNESS THE PARTICULARITY OF APPLICATION OF PRINCIPLES OF LINEAR-ELASTIC FRACTURE MECHANICS TO WOOD AND FRACTURE PARALLEL TO GRAIN