TWI Industrial Member Report Summary 248/1984
By T L Anderson
The effect of crack tip region constraint (CTRC) on fracture toughness in the ductile-to-brittle transition region was studied. Experimental data for two materials, ABS EH36 steel and commercially pure iron, are presented. Transition curves tend to shift to higher temperatures with increasing thickness and crack length-to-width ratio. These upward temperature shifts were attributed to increases in constraint.
A technique was developed to measure CTRC experimentally. These measurements showed that CTRC decreases with crack blunting. This observation led to an analytical model for the ductile-to-brittle transition, which was used to:
i. compute best-fit transition curves through fracture toughness data and
ii. predict transition curves, given appropriate material properties and specimen geometry data.
The possible applications and limitations of this model are discussed.