PSI - Issue 35

Kpemou Apou Martial et al. / Procedia Structural Integrity 35 (2022) 254–260 Kpemou A. M. et al. / Structural Integrity Procedia 00 (2019) 000 – 000

257

4

vs temperature and fitting the data according to Eq. (2 ), one gets an ‘S’ -shaped curve according to W. Oldfield (1980) [8].

CV C  −      CV T D

( ) K J A B = + CV

tanh

(2)

CV CV

T T = It is important to mention that the transition temperature is not a material constant but depends on several parameters such as specimen’s thickness [7], notch radius [9], loading rate [10] and tests used for its determination. This dependence, known as plastic constrain, can be described by several parameters such as constrain factor [11], stress triaxiality [12], parameter [13], and triaxial stress constrain [14] and stress difference = − [15]. A linear relation was found by Wallin [16] between the transition temperature T0 specific to the material failure master curve (MFMC) Kc = f (temperature) and the T stress. (3) T  + Where A CV , B CV , C CV , and D CV are constants. A CV represents the Charpy energy at transition temperature Dcv, B CV is the energy jump between the brittle and ductile plateaus, and 2C CV is the temperature range of the Charpy energy transition. Fig. 2 s hows an example of the ‘S’ -Shaped curve for API 5L X65 pipe steel found in literature.

0

0.

0 Tstress =

stress

 is a parameter depending on the yield stress.

Fig. 2. Charpy V energy versus temperature curve for API 5L X65 pipe steel [7].

A similar relation has been found for X65 pipe steel by Coseru et al. [7] between various transition temperatures T (T t , T tensile , T 0 and T K1/2 ) and critical effective T stress , T ef ,c. . t Tef c (4) where T ef ,c the T stress value is determined at the effective distance and T t.Tef,c=0 is DBTT reference value for T ef ,c equal to 0. , 0 = , 0.14 ef c T t T T = +