Brittle-to-ductile transition in steels and the critical transition temperature

Abstract

Specimens of different thickness made of a low-alloy steel were tested to determine fracture toughness under static and impact loading at room and low temperatures. It was found that for the specimen of each thickness there was a specific brittle-to-ductile transition temperature Tps defined as the upper temperature boundary up to which plane-strain conditions were valid at fracture. The temperature Tee, as well as the brittleness transition temperature Ts0 (determined via the 50% ductile component of the fracture surface), rose with the increase in the thickness B of a specimen. The value of Tps was found to be in a linear dependence on lgB for both static and impact loading.

Crack Dynamics in Metallic Materials

“…On the other hand, general relation for stationary cracks in SSY is low-alloy steel, quasi-static -1, and dynamic loading -2; data after [18].…”

“…Performing the necessary differentiations, we obtain for the displacements and the stresses [17] for the steady-state case. Nilsson [18], Clifton and Freund [19], Achenbach and Bazant [20] later pointed out that these relations are also valid for arbitrary crack motion. It can also be verified that the equations reduce to the appropriate quasi-static forms as a.. We shall now investigate the relation between the Laplace transformed integral IL and the stress intensity factors.…”

“…Consequently, sime the dependencies from the radial distance r and the For a propagating crack the near-field stress distribution differs ft·om that of a stationary crack due to inertia effects (see, e.g. [18]. [19], and the contribution of F. Nilsson, this volume).…”

“…The measured increase in toughness for a ppopagating crack with increasing crack velocity, however, does not necessarily indicate that the same behaviour applies for stationary cracks imPflcted at increasing levels of loading rate. The stress fields of propagating cracks and of stationary cracks under impact loading conditions are diffepent [18,65]. Furthermore, the physical processes which control the energy balance in these two cases can also be very different.…”

“…Within a relatively short tim<-' of about 50 f-JS the shadow patterns reach their maximum size. Unifm·rnly distributed tensile stresses are observed for the following time interval (frames [15][16][17][18][19][20][21][22]; later on the stresses change into compression agEdn ( feames 23--24). Further investigations with a row of holes oriented along the teansverse direction of the specimen also showed rather uniformly distributed stresses in this direction, particularly at later times during the event, i.e.…”