PSI - Issue 60

S.K. Pandey et al. / Procedia Structural Integrity 60 (2024) 3–12 S. K. Pandey/ Structural Integrity Procedia 00 (2023) 000–000

7 5

Error= � � � � − � _ �

� No. of specimens �

(2)

2.3. Evaluation of Normalized- Error at each sets of (n, α) The Error is determined as in Eq.2. Normalized-Error at a point (RO parameter) is the ratio of Error at a point and smallest Error among all points. While computing the Error, the difference of areas is divided with maximum elongation (δ) of specimen at th e rupture, to nullify the effect of length of specimen. Normalized-Error has been determined for all 85 sets of RO parameters with the Errors calculated in the previous paragraph using the Eq.2. The Normalized-Error of SS316LN at the temperature of 298 K has been provided in Fig.6. 2.4. Step 4: Evaluation of optimized set of (n, α) The Normalized-Error at each point (each value of RO parameter) is calculated. Data of 2-dimensional plane is converted into 1-dimension (along a line) as provided in Fig.7 and Fig.8 . Evaluation of unique (n, α) is processed in two steps. In the first step, RO parameters are identified in each row where Normalized-Error is lowest. In the second step, RO parameter is identified among the RO parameters of first step which have lowest Normalized-Error. The lowest value of Normalized-Error, among each row, is found by plotting the Normalized-Error versus RO parameter- n. Abscissa (n) at the minima of curve is marked for each row. For α =12 (typical), Normalized-Errors versus ‘n’ is provid ed in Fig.9. Next, α versus n, determined from above process, is plotted in Fig.10. Now the two dimensional data in converted in one-dimensional data. The best fit equation of, 1-dimentional data of (n, α ) is provided in Eq. 3. For the temperature of 923K, RO parameter- α versus RO parameter - n has been determined for minimum Normalized-Errors as given in Eq. (3).

Fig 6. Normalized-Error for temperature of 298K

Fig 8. Lowest Normalized-Error along a line (1 dimensional) in (n- α) plane

Fig 7. Normalized-Error in (n- α) plane (2 -dimensional)