Visual Cases

On the environmental fracture of polymethylmethacrylate

“…*R is a symbol used in Gurney [11] and is essentially equivalent to 23-" as used in Andrews and Bevan [1,2]. For crack propagation, ER = pK 2 where p = 1 for plane stress and (1 -~) for plane strain.…”

“…It was not readily understood why cracking (under monotonic increasing displacements) was unstable and the specific work of fracture increased. However, Gurney and Hunt [11] suggested that in the presence of a solvent the fracture toughness* (R) of the crack tip material would be apparently increased, (probably due to the blunting of the tip of the craze wedge [2] under increasing load or displacement). When the crack ran away from the swollen zone and into the virgin material with negligible absorption and hence a lower R value, cracking was unstable because dR/dA was negative, A being the crack area.…”

“…When the crack ran away from the swollen zone and into the virgin material with negligible absorption and hence a lower R value, cracking was unstable because dR/dA was negative, A being the crack area. Some fundamental concepts on the stability of cracking are given in [11][12][13][14][15][16][17].…”

“…In the present paper, continuous slow cracking of PMMA in the presence of a variety of liquid environments is discussed. The energy approach of Gurney and co-workers [11][12][13][14] to fracture mechanics is used for fracture measurements.…”

“…When stable cracking was achieved in these experiments, fracture toughness values were obtainable from the method of Gurney and Hunt [11 ] and expressible as a function over a useful range of crack velocity.…”