Fracture toughness

About: Fracture toughness is a research topic. Over the lifetime, 39642 publications have been published within this topic receiving 854338 citations.

Calibration of Weibull stress parameters using fracture toughness data

Abstract: The Weibull stress model for cleavage fracture of ferritic steels requires calibration of two micromechanics parameters $$(m,\sigma _u ) $$ Notched tensile bars, often used for such calibrations at lower-shelf temperatures, do not fracture in the transition region without extensive plasticity and prior ductile tearing However, deep-notch bend and compact tension specimens tested in the transition region can provide toughness values under essentially small-scale yielding (SSY) conditions to support Weibull stress calibrations We show analytically, and demonstrate numerically, that a nonuniqueness arises in the calibrated values, ie, many pairs of $$(m,\sigma _u ) $$ provide equally good correlation of critical Weibull stress values with the distribution of measured (SSY) fracture toughness values This work proposes a new calibration scheme to find $$(m,\sigma _u ) $$ which uses toughness values measured under both low and high constraint conditions at the crack front The new procedure reveals a strong sensitivity to m and provides the necessary micromechanical values to conduct defect assessments of flawed structural components operating at or near the calibration temperature in the transition region Results of a parameter study illustrate the expected values of m for a typical range of material flow properties and toughness levels A specific calibration is carried out for a mild structural steel (ASTM A36)

Hardness, Toughness, and Scratchability of Germanium–Selenium Chalcogenide Glasses

Abstract: Ge-Se chalcogenide glasses are characterized by relatively low hardness (0.39-2.35 GPa) and low fracture toughness (0.1-0.28 MPa.m 1/2 ). Actually, the hardness of chalcogen-rich glasses is low enough so that the brittleness parameter, B = H/K c , is lower than that of silicate glasses. Whereas hardness and Young's modulus increase with increasing germanium contents, fracture toughness follows a trend similar to that of the density and exhibits a maximum for the Ge 20 Se 80 composition, which corresponds to the rigidity percolation threshold. Optical microscopy and atomic force microscopy observations suggest that the indentation deformation proceeds by a localized shear deformation phenomenon. Glasses in the chalcogen-rich region behave viscoelastically at room temperature. As a consequence, an increase of the loading time results in a decrease of hardness and toughness.