PSI - Issue 42

Zeng Chen et al. / Procedia Structural Integrity 42 (2022) 180–188 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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thickness and a/W . It means the constraint levels of 3PB and 5PB specimens are lower. However, the mean values of parameter Q for 3PB and 5PB specimens are very close. It is hard to use parameter Q to quantify the constraint change caused by the multi-axiality effect. From Figure 9, it can be observed that like other studies stated, there is a high-order relationship between the unified parameter  and the fracture toughness for C(T) and SEN(B) specimens, while this relationship no longer exists for 3PB and 5PB specimens. But the differences of  between 3PB and 5PB specimens are very distinct. This demonstrates parameter  is still sensitive to the constraint change caused by the multi-axiality effect. 5. Conclusions A series of multi-axial bending experiments and numerical modelling on 3-point bend specimens and 5-point bend specimens with BS1501-224 28B steel were conducted to validate this method. A large number of experimental data of C(T) and SEN(B) specimens were collected to support the investigation. An investigation of parameter Q and unified parameters φ based on the experimental data and simulation results was discussed. The following conclusions are obtained: • The parameter Q cannot characterize out-of-plane constraint, and it is also not suitable for quantifying the constraint changes caused by multi-axiality. • There is a high-order relationship between the unified constraint parameter  and the fracture toughness for C(T) and SEN(B) specimens, but this monotonic relationship no longer exists for specimens affected by multi-axiality. The parameter  still can be sensitive to the constraint change caused by the multi-axiality effect. Acknowledgements This work was financially supported by TWI Ltd, the National Structural Integrity Research Centre (NSIRC) and China State Scholarship Fund provided by China Scholarship Council (CSC). References 148-1, I. (2009). Metallic materials-Charpy Pendulum Impact Test: I. Test method. In: Geneva International Organization for Standardization. Balart, M., & Knott, J. (2006). Effects of geometry and flow properties on the fracture toughness of a C – Mn reactor pressure vessel steel in the lower shelf region. International journal of pressure vessels and piping , 83 (3), 205-215. Brocks, W., & Schmitt, W. (1995). The second parameter in JR curves: constraint or triaxiality? ASTM special technical publication , 1244 , 209-231. Dodds, R. H., Anderson, T. L., & Kirk, M. T. (1991). A framework to correlate a/W ratio effects on elastic-plastic fracture toughness (J c). International Journal of Fracture , 48 (1), 1-22. Dodds, R. H., Fong Shih, C., & Anderson, T. L. (1993). Continuum and micromechanics treatment of constraint in fracture. International Journal of Fracture , 64 (2), 101-133. https://doi.org/10.1007/BF00016693 E1820-20b, A. (2020). Standard Test Method for Measurement of Fracture Toughness. In: ASTM International West Conshohocken, PA, USA. Gao, X., & Dodds Jr, R. H. (2001). An engineering approach to assess constraint effects on cleavage fracture toughness. Engineering Fracture Mechanics , 68 (3), 263-283. Leevers, P., Radon, J., & Culver, L. (1976). Fracture trajectories in a biaxially stressed plate. Journal of the Mechanics and Physics of Solids , 24 (6), 381-395.