Issue 7

S.K. Kudari et alii, Frattura ed Integrità Strutturale, 7 (2009) 57-64; DOI: 10.3221/IGF-ESIS.07.04 63 The conventional analysis based on applied stress (Fig.7) illustrates that there is good amount of deviation in the results on different specimen geometry, which does not allow one to satisfactorily explain the effect of geometry on PZS. On the other hand, the variation of r p /a with J/a σ y (Fig.6) shows that the nature of growth of PZS in the two types of specimens in both the investigated steels is almost identical up to a particular magnitude of J/a σ y , beyond which the specimen geometry influences the nature of variation of r p /a, as obtained in the investigation of Kudari et al. [5]. The critical value of up to which r p /a is similar in SENT and CT specimens is ≅ 0.0035 . These results elucidate that the development of plastic zone size in a specimen is primarily affected by the specimen geometry and a/W ratio due to varied in-plane constraint [4]. The present experimental results on PZS thus validate the theory proposed by Kudari et al . [5] t hat the study of plastic zones made with respect to normalized J (J/a σ y ) yield better analysis of the results. The PZS results studied in this manner gives clear idea of geometry dependency and can be used for constraint analysis and to obtain specimen size requirements for fracture test independent of geometry. C ONCLUSIONS n this work a simple procedure for demarcating the location of elastic-plastic boundary in the microhardness vs . distance plot ahead of a crack-tip has been suggested. It has been shown that the experimental results of PZS for interstitial free steel are in excellent agreement with the elastic-plastic FE analysis. The experimental results obtained validates the theoretical investigation of Kudari et al . [5], w hich can be used for to obtain specimen size requirements for fracture test independent of geometry. A CKNOWLEDGEMENTS One of the present authors Dr S. K. Kudari would like to thank the Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kharagpur, India, for providing Laboratory facilities to carry out this work. R EFERENCES [1] ASTM E1820 -99a, 1999. Standard test method for measurement of fracture toughness, American Society for Testing and Materials, Philadelphia. [2] G. S. Wang, Engineering Fracture Mechanics, 46 (1993) 909-930. [3] Park, Heung-Bae, Kim, Kyung-Mo, Lee, Byong-Whi., International Journal of Pressure Vessels & Piping, 68 (1996) 279-285. [4] H. Yuan, W. Brocks, Journal of the Mechanics Physics Solids, 46 (1998) 219-241. [5] S. K. Kudari, B. Maiti, K.K. Ray, Journal of Strain Analysis for Engineering Design, 42 (2007) 126-137. [6] A. Uguz, J. W. Martin, Materials Characterization, 37 (1996) 105-118. [7] G.R. Irwin, Proc 7th Sagamore Ordinance Mater. Res. Conf., New York, IV (1960) 63-77. [8] D.S. Dugdale, Journal of the Mechanics Physics Solids, 8 (1960) 100-104. [9] D. Kujawski, F. Ellyn, Engineering Fracture Mechanics, 25 (1986) 229-236. [10] ASTM E8-00, 2000. Standard test method for tension testing of metallic materials, American Society for Testing and Materials, Philadelphia, Pennsylvania. [11] A.H. Priest, Journal of Strain Analysis for Engineering Design, 10 (1975) 225-232 [12] ANSYS Version 9, 2004. Swanson Analysis Systems, ANSYS Inc., Canonsbarg PA, USA [13] E.E. Gdoutos, G. Papakalitakis, International Journal of Fracture, 32 (1987) 143-156. [14] J.R Rice, Journal of Applied Mechanics Transactions of ASME, 35 (1968) 379-386. [15] R. Mendoza, M. Alanis, J. Huante, C. Gonzalez-Rivera, J.A. Juarez-Islas, Journal of Materials Processing and Technology, 101 (2000) 238-244. [16] R. Mendoza, M. Alanis, J. Huante, C. Gonzalez-Rivera, J.A. Juarez-Islas, Materials Science and Engineering A, 276 (2003) 203-209. [17] C. Bathias, R.M. Pelloux, Metallurgical Transactions, 4 (1973) 1265-1273. [18] S.I. Kwun, S.H. Parks, Scripta Metallurgica, 21 (1987) 797-800. [19] C. Loye, C. Bathias, D. Retali J. C. Devux. ASTM-STP 811 (1983) 427-444. I