Plain strain fracture toughness

One of the most important appHcations of LEFM is to estimate the critical crack or defect size which causes fast fracture to occur. This occurs when the value of iCin a stmcture becomes equal to the plain strain fracture toughness, of the material the critical crack size, for a given stress and fracture toughness, is then given by equation 31. 

Plain-Strain Fracture Toughness and Strain Energy Release Rate of Plastics Materials (ASTM D5045-93)... 

Plain strain fracture toughness Kic(J) values were generally lower for these weldments than for their comparable base metal conditions, with the exceptions of the K-58 30% CW/GTAW, the P-538 SMAW, and the A-286 GTAW. 

In the absence of corrosive agents, a crack will not propagate unless the stress intensity factor exceeds a critical value, ATjc, called the plain strain fracture toughness. 

Z = dimensionless constant, typically 1.2 8 = plain strain fracture toughness in MPa m / a = length of crack in meters... 

Based on fhis analysis, a material parameter called the plain strain fracture toughness, a measure of the ability of the material to resist fracture, can be defined as... 

When the applied force on the die due to TCE or thermal differences exceeds this figure, fracture is likely. The plain strain fracture toughness for selected materials is presented in Table 4.8. It should be noted that Equation 4.13 is a function of thickness up to a point but is approximately constant for the area-to-thickness ratio normally found in subsfrafes. 

Brown, W.F., Srawley, J.E. Plain Strain Fracture Toughness Testing of High Strength Metallic Materials. American Society for Testing and Materials, ASTM STP IO (1967)... 

A.S.Saleemi, J.A. Naim, The Plain-Strain Essential Work of Fracture as Measure of the Fracture Toughness of Ductile Polymers, Polym. Eng. Sci., 30 (1990), 211-218. 

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