Issue 48

R. Nikhil et alii, Frattura ed Integrità Strutturale, 48 (2019) 523-529; DOI: 10.3221/IGF-ESIS.48.50 524 This expression is valid for specimens made of homogenous material. Wang and co-authors [2] proposed CTOD equations expressed in terms of weld height, mismatch level and strain hardening rate for specimens made of non-homogeneous and strain hardening materials. Smith [3], Panontin and co-authors [4], Cassanelli and co-authors [5], Kim and co-authors [6], Davies and co-authors [7], have proposed analytical and numerical solution to η expression for even match ( M =1) C(T) specimens but varying strain hardening exponent. Xuan and co-authors [8] and Marie & Nedelec [9] have performed FE based analysis for various mismatch factors from 0.25 to 2 and 2.3 respectively. A literature review of η solution for C(T)specimen in tabular form is provided by H. Zhou and co-authors [10]. They have analyzed the influence of mismatch factor, weld height, material hardening exponent and a/ W ratio effect on η solution. ASTM Type 316LN stainless steel is a major structural material for fast breeder reactor being commissioned at Kalpakkam, India. The M value for 316LN weld is found to vary across the weld thickness [11] and found to be as high as 2.2. In the present study, plane strain FE analysis have been carried out to assess the η factor for C(T) geometry with weld width to specimen width ratio, h/ W varying from 0.08 to 0.32 and crack depth to width ratio, a/ W varying from 0.45 to 0.7 for strength mismatch M = 1.2,1.4,1.6,1.8,2 and 2.2. T HEORETICAL BACKGROUND or homogeneous material, as per ASTM experimental load, load line displacement (crack opening displacement) and crack length data are obtained to evaluate J -integral values for a growing crack. A typical plot is shown in Fig. 1. Figure 1 : Area under the load-displacement plot. J- integral consists of an elastic component and a plastic component. p e J J J   (2) where ' 2 E K J e  such that E E  ' for plane stress   2 ' 1    E E for plane strain (3) Bb A J p p   (4) F