PSI - Issue 60

Prakash Bharadwaj et al. / Procedia Structural Integrity 60 (2024) 655–664 Prakash Bharadwaj / Structural Integrity Procedia 00 (2019) 000 – 000

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calculation of CPZ by FE analysis for 34.58 mm crack size is 4.46% higher while for crack size 35.99 mm and 38.04 mm, it is 5.2% and 5.38% higher respectively when compared with the corresponding DIC evaluated experimental CPZ. The average difference is about 5%.

Table 1. Comparison of CPZ calculated by DIC system and FE analysis.

Δ K (Mpa √ )

CPZ (mm) calculated for FE plane stress case and 0.1% average loop opening condition

CPZ (mm) calculated by DIC

CPZ (mm) calculated by Irwin’s expression

Crack size (mm)

34.58

28.21959

0.4412

0.4609

1.2636

35.99

32.89806

0.6024

0.6341

1.7173

38.04

42.37911

0.7721

0.8137

2.8498

6. Conclusions The FCGR tests were conducted on nuclear piping material steel SA333Gr6 using a constant load range and load ratio (R) on a full compact tension (CT) specimen in order to determine the size of the cyclic plastic zone resulting from cyclic loading. The experimental cyclic plasticity zone (CPZ) was compared to the CPZ determined by a finite element (FE) analysis utilizing a calibrated material model. The following inferences were obtained: • Shape of the CPZ is asymmetric butterfly type. The area of CPZ increases with an increase in crack size • Crack growth observed by the DIC system is in good agreement with growth calculated using the unloading compliance method. • Load-strain curve can be used instead of a stress-strain curve for different zone identification ahead of the crack tip and the straight-line fitting method is one of the ways to get the CPZ. • The DIC evaluated experimental CPZ is found to in close agreement with that evaluated using plane stress- FE analysis using Chaboche model. The average difference is observed about 5%. • The CPZ obtained using Irwin’s expression is roughly 2.9 to 3.7 times of the size obtained using DIC evaluated experimental CPZ. References ARAMIS, G., 2009. User Manual-Software. GOM, Germany, Manual de usuario. ASTM Code, E647-95a, 1995 “Standard Test Method for Measurement of Fatigue Crack Growth Rates,” American Society for Testing and Materials. Bathias, C. and Pelloux, R.M., 1973. Fatigue crack propagation in martensitic and austenitic steels. Metallurgical Transactions, 4, pp.1265-1273. Bharadwaj, P., Gupta, S.K. and Chattopadhyay, J., 2023, June. Cyclic plastic zone and stress-strain evolution in low C-Mn steel ahead of crack under fatigue loading. In AIP Conference Proceedings (Vol. 2786, No. 1). AIP Publishing. Chapetti, M.D., Miyata, H., Tagawa, T., Miyata, T. and Fujioka, M., 2005. Fatigue crack propagation behaviour in ultra-fine grained low carbon steel. International journal of fatigue, 27(3), pp.235-243. Chikh, B.O., Imad, A. and Benguediab, M., 2008. Influence of the cyclic plastic zone size on the propagation of the fatigue crack in case of 12NC6 steel. Computational Materials Science, 43(4), pp.1010-1017. Dowling, N.E., Kampe, S.L. and Kral, M.V., 1999. Mechanical behavior of materials: engineering methods for deformation, fracture, and fatigue. Gao, H., Lin, Z., Huang, X., Shang, H. and Zhan, J., 2022. In situ measurement of cyclic plastic zone and internal strain response of Q&P steel near fatigue crack tip region based on micro-DIC. Materials, 15(17), p.6114. Gao, P.F., Lei, Z.N., Wang, X.X. and Zhan, M., 2019. Deformation in fatigue crack tip plastic zone and its role in crack propagation of titanium alloy with tri-modal microstructure. Materials Science and Engineering: A, 739, pp.198-202. Glinka, G., 1985. Calculation of inelastic notch-tip strain-stress histories under cyclic loading. Engineering Fracture Mechanics, 22(5), pp.839 854. Gonzales, G.L.G., González, J.A.O., Antunes, F.V., Neto, D.M. and Díaz, F.A., 2023. Experimental determination of the reversed plastic zone size around fatigue crack using digital image correlation. Theoretical and Applied Fracture Mechanics, 125, p.103901.