PSI - Issue 13

J Beswick et al. / Procedia Structural Integrity 13 (2018) 63–68

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Beswick et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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Fig. 6. Predicted fracture toughness values of the pre-strained material for the three constraint conditions. The calculations used the stress-strain properties for the pre-strained materials and the modified Beremin model with exponential plasticity correction with  =1.5 and power law correction with  =0.02 .

4. Conclusions

The J-Q analysis suggests that the shape of the failure curve might be unaffected by the plastic strains. Testing with several constraint geometries of as-received material would provide the shape. The LA analysis suggests that two constraint geometries would be sufficient for calibration in order to predict the apparent fracture toughness across different constraints, with plasticity corrections improving the predictions. The tested LA could not provide the shift of the failure curve caused by plastic strains. Potentially LA could be recalibrated for a given pre-strained material, which would require testing of at least two constraint geometries. The conclusion is that the changes of deformation and fracture toughness properties, caused by the introduction of plastic strains, are not correlated to the extent necessary for the existing LA to predict toughness from known deformation properties. At present, this leaves the option of testing materials with different levels of plastic strain with at least one constraint geometry. The alternative is to advance the LA by including the effect of pre-existing micro-cracks generated during the plastic deformation history. This is a subject of on-going work, which will be reported in the near future. Acknowledgements This investigation was supported by the Royal Academy of Engineering, UK, through the Newton Research Collaborative Program Grant NRCP1617/6/19, signed between University of Manchester (UK) and University of São Paulo (Brazil). Experimental work was conducted with the support of EPSRC and Wood via the Nuclear Engineering Doctorate (EngD) Training Centre, grant EP/G037426/1. of the ASME 2016 Pressure Vessels and Piping Division Conference, Vancouver. BS EN 10002-5, 1992. Tensile Testing of Metallic Materials. British Standards Institute. E1820-01, 2003. Standard Test Method Measurement of Fracture Toughness. ASTM International. O'Dowd, N.P., Shih, C.F., 1991. Family of Crack-Tip Fields Characterized by a Triaxiality Parameter - I. Structure of Fields. Journal of the Mechanics and Physics and Solids 39, 989-1015. R6, 2015. Assessment of the Integrity of Structures Containing Defects, Revision 4. EDF Energy Nuclear Generation Ltd. Ruggieri, C., Dodds R.H., 2018. A local approach to cleavage fracture modelling: an overview of progress and challenges for engineering applications. Engineering Fracture Mechanics 187, 381-403. Ruggieri, C., Savioli, R., Dodds, R.H., 2015. An engineering methodology for constraint corrections of elastic-plastic fracture toughness – Part II: Effects of specimen geometry and plastic strain on cleavage fracture predictions. Engineering Fracture Mechanics 146, 185-209. Sherry, A.H., Wilkes, M.A., Beardsmore, D.W., Lidbury D.P.J, 2005. Material constraint parameters for the assessment of shallow defects in structural components-Part I: Parameter solutions. Engineering Fracture Mechanics 72, 2373-2395. References ABAQUS Documentation ©, 2015. Dassault Systèmes, Providence, RI, USA. Brayshaw, W.J., Sherry, A.H., Burke, M.G., James, P., 2016. Characterisation of mictrostrucutre and properties of a transitiion weld. Proceedings