PSI - Issue 71

Nagaraj Ekabote et al. / Procedia Structural Integrity 71 (2025) 58–65

65

5. Conclusions CTOD , as a fracture parameter, is scarcely acknowledged among the practical fracture applications. Due to distinct estimation procedures adopted by popular standard bodies, the CTOD magnitudes differed largely and created doubts among the practitioners. PHM based CTOD estimation adopted by British and Japanese standards proved to be accurate and widely accepted in applications. However, the need for a relationship between J and CTOD as similar to K and G is useful. On a similar assumption, ASTM 1820 defined the J-CTOD relation, but the estimated CTOD magnitudes were inaccurate. The major observations made during the present efforts are listed below. ● The constraint parameter, m , as stated in ASTM 1820 are redefined by using 1 st order polynomials for CT, DCT, and SENB specimens. The proposed m equations were verified for the different a/W and S yt /S ut . The proposed equations are valid for materials having S yt /S ut between 0.5 and 1. ● CTOD computed through BS 7448 for CT specimen seems accurate (as evidenced in literature) and exhibits non-linear variation of CTOD for the increase in applied load or J -integral. ● A linear relationship between J-CTOD as defined in ASTM 1820 through constraint parameter, m , thus needs modification to account the non-linearity (as seen in BS 7448) among the two. A relook and modification in this direction may be helpful for wider application.

Fig. 9: CTOD in ASTM 1820 and BS 7448.

Fig. 10: CTOD in BS 7448 and FE origin .

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