Reasonable Analysis of Crack Arrest Toughness K_ca Calculation Expression in WES 2815（2014） and UR S33

Crack arrest toughness K_ca of three different crack types is calculated by finite element method for K_ca calculation expression and calculation method of crack deflection in WES 2815:2014 《Test method for brittle crack arrest toughness,K_ca》 and UR S33 《Requirements for Use of Extremely Thick Steel Plates》. The mistake of K_cacalculation expression in above standards is pointed out based on the FEM calculation results.It is unreasonable to calculate K_ca according to the length of crack straight projection for large crack deflection angle.