Evaluation of fracture toughness by notched small punch tests with Weibull stress method: Fid-Bau Portal

Evaluation of fracture toughness by notched small punch tests with Weibull stress method

Xu, Yifei / Guan, Kaishu

Highlights • Critical J integral of LNSP specimen at 77K is lower than that of 0.4T SENB specimen. • The cell to determine the σw shall remove the impact of unnecessary plastic zone. • Equivalent σw method can be used to estimate $J_{c}^{ITSENB}$ with other small specimens.

Abstract The fracture toughness obtained by pre-notched (pre-cracked) small punch specimens is much higher than that obtained by conventional single edge notch bending (SENB) or by compact tension specimens. In this paper, an equivalent Weibull stress method has been introduced. The tests with 0.4T SENB specimens and linear notched small punch specimens were carried out at 77K. At this temperature (on lower shelf), the results of both test methods show scatter but not significant. The loads at fracture of both types of specimen were used to determine the Weibull stress parameter, m, and the Weibull stress, σw, with finite element method. Base on the assumption that Weibull stress parameters are material constants, the m which could meet a condition that $σ_{w}^{0.4 TSENB}$ = $σ_{w}^{LNSP}$ was regarded as Weibull stress parameter, m. The critical J integral of 1T SENB $J_{c}^{ITSENB}$ at 77K has been estimated with m and σw deduced by 0.4T SENB and LNSP specimens.