本研究以ABAQUS有限元素軟體分析六種不同載重位置下，對純I型、純II型與I+II複合型之四點彎曲斷裂韌度試驗模型，分析其應力強度因子對於裂隙比(裂縫長度/試體寬度)的變化。本研究以無因次因子(YI代表I型、YII代表II型)表示所計算的應力強度因子。本研究針對元素選取、網格劃分(全域和收斂區域)、資料點在裂縫上的選取位置，分別討論計算結果的適當性。
本研究發現在裂縫尖端附近使用楔型體奇異元素時，其結果較六面體奇異元素浮動較小，此外並無差異。在比較Wang et al.(1977)與徐等人(1984)所得之結果時，本研究計算所得之YI值於兩者之間且變化趨勢相當一致，YII值隨裂隙比的變化趨勢則是與徐等人的結果相似。本研究發現ABAQUS在計算純II型的模型中會出現KI值，此值會隨裂隙比變大而減少，在實際應用上宜注意此可能造成的計算誤差。

In this study, the models were established by a finite element program ABAQUS following Lee (2018). The simulation was based on the single edge-cracked four-point bending tests (FPBT) of granite specimens based on the study of Lai (2001). Six sets of loading configurations were used to simulate the mode-I, mode-II and mixed-mode I+II conditions. Then the mixed-mode stress intensity factors (SIFs) as a function of crack to depth ratio (a/W) were investigated in this study. YI and YII defined by this study represent the forms of dimensionless SIFs. The applications of the ABAQUS under different scenarios of element selection, mesh controls in particular area and the distribution of SIFs on crack front were discussed.
This study demonstrates that wedge singular elements for crack front region can provide better results than hexahedron elements. The YI results are similar to the results by Wang et al (1977) and Xu (1984). The YII results are similar to those by Xu (1984). The KI values may be found in pure mode-II models, and increase when crack length decreases. It should be noted that this may cause calculation errors.

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