本研究成功地以數值模擬方法和實驗方法驗證了利用最小二乘法（Least-Squares Method）求解不同板寬或板厚對接鋼板接頭處楔形尖端應力強度因子（Notch Stress Intensity Factor）之適用性。在數值模擬部份，透過有限元素法對各種不同幾何形狀之試體進行模擬分析，並以最小二乘法求解應力強度因子後，討論各幾何形狀參數對應力強度因子之影響。由結果發現，當板寬差距越大之鋼板彼此對接時，其Mode I的應力強度因子會越高，而Mode II的應力強度因子會越小；兩楔形尖端距離長短對應力強度因子也會造成類似的影響，但其影響程度不如板寬差距的影響明顯；非對稱型對接鋼板受到上述幾何形狀參數之影響，與對稱型對接鋼板所受影響相似，但其受影響的程度較小；整體而言，在其他幾何參數條件相同之前提下，非對稱型對接鋼板之Mode I應力強度因子相對於對稱型對接鋼板為小，而Mode II應力強度因子則相對為大。在實驗部分，本研究利用數位影像相關度（Digital Image Correlation）技術，成功地量測出對接鋼板受拉後微小變形的位移資料，並以此位移資料配合最小二乘法求解出對接鋼板楔形尖端的應力強度因子，此實驗方法將可運用在鋼橋、天車梁或機械構件的疲勞評估與分析上。

This study successfully verifies the feasibility of using the least-squares technique to evaluate the mixed-mode notch stress intensity factors (N-SIFs) for butt-welded joints of two unequal width or thickness plates numerically and experimentally. In numerical analysis, the least-squares technique integrated with finite element analysis is employed to compute the mode-I and mode-II N-SIFs for butt-welded joint specimens of various geometric shapes. The followed parameter study is performed to understand the variation of N-SIFs against the discussed geometric parameters. The results of parameter study show that: (1) the greater the width (or thickness) difference between the two butt-welded plates, the higher the mode-I N-SIF value but the smaller the mode-II N-SIF value; (2) the longer the distance between the two notch tips, the higher the mode-I N-SIF value but the smaller the mode-II N-SIF value; (3) the unsymmetrical specimen usually has smaller mode-I N-SIF and larger mode-II N-SIF compared to the symmetrical specimen with the same geometric parameters. In the experimental portion of this study, the digital image correlation technique is utilized to measure the subtle deformations of the two butt-welded joint specimens and the measured displacement data are used to derive the N-SIFs for the two specimens. The N-SIF results of the two specimens obtained from the experiment are in good agreement with those computed from the numerical analyses. The proposed experimental method can be applied to the fatigue evaluation of similar butt-welded details in steel bridges, crane girders or other mechanical components.

Atzori, B., Lazzarin, P. and Tovo, R., Stress Distributions for V-Shaped Notches under Tensile and Bending Loads. Fatigue Fract. Engng Mater. Struct. Vol. 20, No. 8, pp. 1083-1092, (1997)
Chen, D.A., Stress Intensity Factors for V-notched Strip under Tension or In-Plane Bending. International Journal of Fracture, Vol. 70, pp. 81-97, (1995)
Chu, T.C., Ranson, W.F., Sutton, M.A. and Peter, W.H., Application of Digital-Image-Correlation Technique to Experimental Mechanics. Experimental Mechanics, Vol. 25, pp. 232-244, (1985)
Gross, R. and Mendelson, A., Plane Elastostatic Analysis of V-Notched Plates. Int. J. Fracture Mech.Vol. 8 , pp. 267-276, (1972)
Ju, S.H., Accuracy and Limit of a Least-Squares Method to Calculate 3D Notch SIFs. International Journal of Fracture, Vol. 148, pp. 169-183, (2007)
Ju, S.H., Simulating Stress Intensity Factors for Anisotropic Materials by The Least Squares Method, International Journal of Fracture, Vol. 81, pp. 283-297, (1996)
Lazzarin, P. and Filippi, S., A Generalized Stress Intensity Factor to be Applied Torounded V-Shaped Notches. International Journal of Solids and Structures, Vol. 43, pp. 2461-2478, (2006)
Lazzarin, P. and Tovo, R., A Unified Approach to The Evaluation of Linear Elastic Stress Fields in The Neighborhood of Cracks and Notches. International Journal of Fractur, Vol 78, pp. 3-19, (1996)
Lazzarin, P. and Tovo, R., A Notch Intensity Factor Approach to The Stress Analysis of Welds. Fatigue & Fracture of Engineering Materials & Structures, Vol 21, pp. 1089-1103, ( 1998)
Lazzarin, P. and Livieri, P., Notch Stress Intensity Factors and Fatigue Strength of Aluminium and Steel Welded Joints. International Journal of Fatigue,Vol. 23, pp. 225-232, (2001)
Lyons, J.S., Liu, J. and Sutton, M.A., High-Temperature Deformation Measurements Using Digital-Image Correlation. Experimental Mechanics, Vol. 36, pp. 64-70, (1996)
McNeill, S.R., Peters, W.H. and Sutton, M.A., Estimation of Stress Intensity Factor by Digital Image Correlation. Engineering Fracrure Mechanics, Vol. 28, pp. 101-112, (1987)
Sutton, M.A. and McFadden, C., Development of a Methodology for Non-Contacting Strain Measurements in Fluid Environments Using Computer Vision. Optics and Engineering, Vol. 32, pp. 367-377, (2000)
Sutton, M.A., Wolters, W.J., Peters, W.H., Ranson, W.F. and McNeill, S.R., Determination of displacements using an improved digital correlation method. Image and Vision Computing, Vol. 1, No. 3, pp. 133-139, (1983)
Sutton, M.A., Zhao, W., McNeill, S.R., Helm, J.D., Piascik, R.S. and Riddell, W.T., Local Crack Closure Measurements: Development of a Measurement System Using Computer Vision and a Far-Field Microscope. advances in fatigue crack closure measurement and analysis : Second Volume, pp. 145-156, (1999)
Press, W.H., Flannery, B.P., Teukolsky, S.A. and Vettenling, W.T., Numerical Recipes, The Art of scientific Computing. Cambridge University Press, New York, (1986)
Williams, ML., Stress Singularities Resulting From Various Boundary Conditions in Angular Corners of Plates in Tension. J. App. Mech. Vol 19, pp. 526–528, (1952)
林奕佐，“鋼構填角銲搭接接頭應力強度因子之研究”，國立成功大學土木工程學系，台南，(2007)
林容暄，“承拉型填角銲十字接頭應力強度因子之量測與數值分析”，國立成功大學土木工程學系，台南，(2007)
涂森屏，“應用影像相關性量測變位”，國立成功大學土木工程學系，台南，(2007)
劉淑秀，“應用數位相機發展非接觸式量測技術及建立自動化運算程式”，國立成功大學土木工程學系，台南，(2007)