Fracture behavior of surface cracked panels of HT-9 at low temperatures

Cleavage fracture and irradiation embrittlement of fusion reactor alloys: mechanisms, multiscale models, toughness measurements and implications to structural integrity assessment

“…For certain well-defined conditions, 4 known as SSY, the fields are self-similar in non-dimensional distance, r=d % r= ½K 2 J =ð2E 0 r y Þ, and are uniquely determined by K J , E 0 and rðeÞ [1]. As discussed below, the high r n fields must reach a critical level ðr n ¼ r Ã Þ that encompasses a sufficient volume of trigger particle microstructure in front of the crack tip to cause cleavage [1,[4][5][6][7][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

“…In almost all-practical situations, the amplitude of the fields at a given K J is reduced from the SSY limit, due to the loss of constraint, which increases with increasing D (Fig. 4(b)) [1,4,6,[23][24][25][26][27][28][29][30]. 5 CL increases the K Jm and K Je at cleavage.…”

“…Indeed, in the limit of severe CL, the local fracture mode may change from cleavage to ductile tearing. CL also occurs for shallow cracks and for tensile versus bending dominated loading conditions, due to compressive stress fields (a so-called T-stress) in the direction of crack propagation [1,4,21,[26][27][28][29][30]. Note that statistical (depending on B) and CL effects (depending on geometry, D and B) interact to increase K J e [22][23][24][25].…”

“…We (and others) have proposed an alternative model that cleavage, by either a single or few propagating microcracks, or quasi-cleavage involving extensive microcracking prior to cleavage, occurs when the r n ¼ r à encompass a critical area ðA à Þ, or more generally volume, [4][5][6][7][8][23][24][25][26][27][28][29][30]. Here, Aðr n Þ is the in-plane area within a specified r n stress contour averaged over the crack front length, B.…”

“…The r à ðT Þ-V à model also provides a basis to treat extrinsic size and geometry effects on the measured K J m [4,6,11,[23][24][25][26][27][28][29][30]. As noted previously, when CL occurs in small specimens undergoing extensive plastic deformation, a larger K J is needed to produce the same stressed volume V ðr n Þ ¼ BAðr n Þ compared to the corresponding K J for SSY conditions.…”