PSI - Issue 71

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

63

0.4 0.5 0.6 0.7 0.8

3.092 3.07 3.048 3.026 3.004

3.428 3.205 2.982 2.759 2.536

3.524 3.295 3.066 2.837 2.608

1.626 1.52 1.414 1.308 1.202

Fig. 6: m variation in SENB specimen w.r.t S yt /S ut for varied a/W.

As the a/W increases, a gradual increase in m is noticed. Similar to CT and DCT specimens, the increase in S yt /S ut resulted in decrease in m magnitude. However, the decreasing m followed almost the linear nature for all the considered a/W against S yt /S ut . It is clear that a mathematical model of 3 rd order polynomial is unnecessary to the current linear nature behavior and 1 st order polynomial is sufficient. While shifting from the 3 rd order polynomial to 1 st order polynomial, the a/W dependent geometry dependent constants ( A 0 , A 1 , A 2 , and A 3 ) need to be discarded and new a/W dependent constants will be introduced. A mathematical modelling of straight line in the general form, for the m estimation in SENB is shown in Equation (6). The new constants Z 0 and Z 1 represent the intercept and slope of the straight line respectively. The procedure to estimate the new constants Z 0 and Z 1 is discussed further. = 0 − 1 ∗( ) (6) Firstly, a linear equation in the form of Equation (6), was fitted for each of the lines represented for a/W in Fig. 6. A total of seven linear equations were generated for each a/W varied between 0.2 and 0.8. From each equation, intercept and slope were extracted and plotted against the change in a/W as shown in Fig. 7.

Fig. 7: Variation of new constants Z 0 and Z 1 vs. a/W in SENB specimen.

The variation of new constants, Z 0 and Z 1 were linear as witnessed in Fig. 7. The increase in Z 0 , and decrease in Z 1 , with increase in a/W were noticed. These linear variations of Z 0 and Z 1 against a/W are further mathematically modelled as shown in Equation (7) and (8). With these proposed Equations (7) and (8), the new constants, Z 0 and Z 1 , were estimated and substituted in Equation (6) to compute the modified constraint parameter in SENB,