13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- 6. Conclusions The Finite element Analysis and Direct measurement of the crack tip displacement field is performed using Abaqus software and Digital Image Correlation (Q4-DIC). In Finite Element Analysis, the two parameter fracture mechanics approach, describing the near–crack-tip stress field (SIF and T-stress) were calculated using the domain integral “J”. In Digital Image Correlation, these parameters were obtained by adjusting the first supersingular term of William’s series. One the crack tip was determined, the crack growth increment is estimated in addition to other global parameters such as the stress intensity factor range and T-stress. In both method, good agreement is shown and finite element analysis can be validated. The stress intensity factor versus crack length remains constant whereas the T-stress varies from negative to positive. This later variation is similar to the three point bend beam, but different from the compact tension specimen, for which the T-term is always positive. Using Digital Image Correlation (DIC), the stress intensity factor and T stress were estimated with 10% and 15% uncertainty in a complex loading set-up without the need for a numerical modeling of the experiment. The displacement and crack extension at the onset of crack propagation is important. It is expected that any model that can match all the experimentally observed features of the test will provide a significant enhancement to our present capability to predict any fracture parameter. Our wedge splitting test is particularly attractive for fundamental research and model validation because of the enhanced length of stable crack propagation. This advantage allows us the identification of crack propagation parameters during all propagation from one single test. Acknowledgement The authors acknowledge support of the ANR Program SYSCOMM grants ANR-09-SYSC006 (France). References [1] T.Fett, A Green’s function for T-stresses in an edge-cracked rectangular plate. Eng Frac Mech, 57(4) (1997) 365-373. [2] B. Cotterell, J.R. Rice, Slightly curved or kinked cracks. Int J Fracture, 16(2) (1980) 155-169. [3] H.N. Linsbauer and E.K. Tschegg, Fracture energy determination of concrete with cubeshaped specimens. Zement und Beton, 31 (1986) 38-40. [4] E. Bmhwiler and E H. Wittmann, The wedge splitting test: A method of performing stable fracture mechanics tests. Engineering Fracture Mechanics, 35 (1990) 117-125. [5] M. Elser, E. K. Tschegg, N. Finger, S. E. Stanzl-Tschegg, Fracture behaviour of polypropylene-fibre reinforced concrete: an experimental investigation. Compos Sci Technol, 56 (1996) 933–45. [6] J. Scheibert, C. Guerra, F. Célarié, D. Dalmas and D. Bonamy, Brittle-Quasibrittle Transition in Dynamic Fracture: An Energetic Signature. Physical Review Letters, 104 (2010) 045501. [7] L. Ostergaard, Early-age fracture mechanics and cracking of concrete-experiments and modelling. Ph.D. Thesis. Department of Civil Engineering, Technical University of Denmark; 2003. [8] G.V. Guinea, M. Elices, J. Planas, Stress intensity factors for wedge-splitting geometry. Int J Fracture, 81 (1996) 113–24.
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