CHEVRON-NOTCHED TOUGHNESS OF MATERIALS WITH RISING FRACTURE-RESISTANCE CURVES

The effect of rising resistance curves on the fracture tougness determ ined from chevron-notched beam tests is estimated via a set of simple numerical calculations, It is shown that for materials with a rising r esistance curve, the toughnesses determined by the peak load method an d by the work of fracture method are both higher than the initiation t oughness, and both depend on the sample size relative to the length ov er which the resistance curve increases. It is also found that the tou ghness based on the work of fracture is higher than that based on the peak load, Fracture toughness data obtained from tests of a nickel-alu mina composite are discussed in light of the results of the numerical calculation.