Dendrite tip splitting and primary spacing adjustment mechanism of Al-Cu alloy during directional solidification;

High pressure,rich gas transmission pipeline demands the development of measuring method of CTOA.

Two parameters of the crack dynamic propagation driving force, energy release rate and crack tip opening angle, are calculated by establishing a finite element model of the crack dynamic propagation in gas pipelines and considering the attenuation of the crack propagation velocity.

The calculating model and method for crack tip opening angle (CTOA) were introduced.

Experimeneal research on high Temperature CTOD of electron beam welded joints of GH4169 alloy;

Then regression equation is obtained between CTOD and welding parameter.

0 for predicting the welding performance parameter-crack tip opening displacement (CTOD)-of high strength pipeline steel joint.

Based on BS7448 fracture toughness test experiment standard (ISO/TC164/SC4-N400) and DNV-OS-C401, crack tip opening displacement (CTOD) tests are carried out on 80 mm thick plates butt joints of offshore petroleum platform joined by the submerged-arc welding and CO2 gas shielded welding.

The measuring and testing technique of crack tip opening displacement (CTOD)tests for large welded joints in the offshore platform under low environmental temperatures of -15℃ were performed in accordance with the BS 7448 standard (part2,1997).

The results show that G_(fF),critical crack mouth opening displacement(δ_(fmc)) as well as critical crack tip opening displacement(δ_(ftc)) of SFHAC increase linearly with the increas.

In order to investigate the size effect of the fracture toughness of concrete,the size effect law deduced from Weibull s statistical theory was compared with that from Bazant s energy release principle,and three fracture parameters,namely,the initiatial fraction toughness(Kini1c),the unstable toughness(Kun1c) and the critical crack tip opening displacement(δc) were tested.