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| Three-dimensional characteristic analyses on mixed mode I/II crack of CTS specimens |
| Received:August 25, 2009 Revised:November 15, 2009 |
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| DOI：10.7511/jslx201104027 |
| KeyWord:mixed mode crack thickness effect out-of-plane constraint Tz in-plane constraint T stress |
| Author | Institution |
| 董蕙茹 |
北京航空工程技术研究中心,北京 |
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| Abstract: |
| The full field three-dimensional finite element computation was performed for Compact Tension Shear (or CTS) specimens of an aeronautical structure aluminum alloy under I/II mixed mode-loading conditions. The characteristics of out-of-plane constraint Tz and in-plane constraint T-tress were analyzed. The effects of thickness and loading conditions on stresses, stress triaxiality Rσ and strain energy density U0 were examined. In particular the characteristics of these parameters on the observed crack initiation angle are discussed. It is shown: (1) in-plane constraint T-stress vanishes for the CTS specimen with a/W=0.5. (2) The size of the three-dimensional region scales with thickness B (0.4~0.5B) and is no relative with mode mixity. However, the thickness effect weakens with decreasing loading angle and almost disappears under pure II loading condition. (3) The out-of-plane constraint Tz decreases as polar radial r and thickness size z increase, and is independent of the polar angle θ. (4) The direction of U0min indeed represents the crack initiation direction of three-dimensional mixed mode fracture. The results make a theoretic basis to establish a three-dimensional mixed mode fracture criterion. |