Fracture toughness

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

The Penny-Shaped Crack and the Plane Strain Crack in an Infinite Body of Power-Law Material

Abstract: A study is carried out of the problem of a penny-shaped crack in an infinite body of power-law material subject to general remote axisymmetric stressing conditions. The plane strain version of the problem is also examined. The material is incompressible and is characterized by small strain deformation theory with a pure power relation between stress and strain. The solutions presented also apply to power-law creeping materials and to a class of strain-rate sensitive hardening materials. Both numerical and analytical procedures are employed to obtain the main results. A perturbation solution obtained by expanding about the trivial state in which the stress is everywhere parallel to the crack leads to simple formulas which are highly accurate even when the remote stress is perpendicular to the crack.

Fracture and impact behaviours of hollow micro-sphere/epoxy resin composites

Abstract: Fracture and impact behaviours of hollow-glass micro-sphere/epoxy resin composites are studied in terms of fracture toughness, fractography, flexural properties and impact force. Volume fraction of micro-spheres for the composites was varied up to 0.65. The addition of micro-spheres did not enhance the specific fracture toughness of the composites despite the presence of a pinning mechanism at relatively low volume fractions. Performance in reducing the impact force was enhanced as the content of micro-spheres increased, but at the expense of other properties such as specific fracture toughness and specific flexural strength, while specific flexural modulus marginally increased at some high volume fractions of micro-spheres.

On the effect of x-ray irradiation on the deformation and fracture behavior of human cortical bone

Abstract: submitted to Bone On the effect of x‐ray irradiation on the deformation and fracture behavior of human cortical bone Holly D. Barth a,b,c,† , Maximilien E. Launey a,† , Alastair A. MacDowell b Joel W. Ager III a and Robert O. Ritchie a,c,  a Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Experimental Systems Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA b c Department of Materials Science & Engineering, University of California, Berkeley, CA 94720, USA ABSTRACT In situ mechanical testing coupled with imaging using high‐energy synchrotron x‐ray diffraction or tomography imaging is gaining in popularity as a technique to investigate micrometer and even sub‐micrometer deformation and fracture mechanisms in mineralized tissues, such as bone and teeth. However, the role of the irradiation in affecting the nature and properties of the tissue is not always taken into account. Accordingly, we examine here the effect of x‐ray synchrotron‐source irradiation on the mechanistic aspects of deformation and fracture in human cortical bone. Specifically, the strength, ductility and fracture resistance (both work‐of‐fracture and resistance‐ curve fracture toughness) of human femoral bone in the transverse (breaking) orientation were evaluated following exposures to 0.05, 70, 210 and 630 kGy irradiation. Our results show that the radiation typically used in tomography imaging can have a major and deleterious impact on the strength, post‐yield behavior and fracture toughness of cortical bone, with the severity of the effect progressively increasing with higher doses of radiation. Plasticity was essentially suppressed after as little as 70 kGy of radiation; the fracture toughness was decreased by a factor of five after 210 kGy of radiation. Mechanistically, the irradiation was found to alter the salient toughening mechanisms, manifest by the progressive elimination of the bone’s capacity for plastic deformation which restricts the intrinsic toughening from the formation “plastic zones” around crack‐like defects. Deep‐ultraviolet Raman spectroscopy indicated that this behavior could be related to degradation in the collagen integrity. Keywords: Human cortical bone, x‐ray radiation, deformation, toughness, collagen Both authors contributed equally to this work Corresponding author. tel: +1‐510‐486‐5798; fax: +1‐510‐643‐5792. E‐mail address: RORitchie@lbl.gov (R.O. Ritchie)

A Plastic-Strain, Mean-Stress Criterion for Ductile Fracture

Abstract: We describe a computer model for predicting ductile-fracture initiation and propagation. The model is based on plastic strain. Fracture starts or a crack extends when the integrated product of the equivalent plastic-strain increment and a function of the mean stress exceeds a critical value over a critical length. This critical length is characteristic of the microstructure of the material. The computer fracture model is calibrated by computer simulation of simple and notched round-bar tension tests and a precracked compact tension test. The model is then used to predict fracture initiation and propagation in the standard Charpy V-notch specimen. The computed results are compared with experiments. The model predicts fracture toughness from tests of standard surveillance specimens from nuclear-reactor pressure vessels and can be applied to fracture calculations for these vessels.

Fracture toughness of type 304 and 316 stainless steels and their welds

Abstract: Fracture toughness data for type 304 and 316 stainless steels and their welds are reviewed. The material and operational parameters evaluated in this paper include: heat to heat variability; weld process variations; welding induced, heat affected zones; crack orientation; cold work; monotonic and cyclic prestrain; long term thermal aging; neutron irradiation; temperature; and loading rates. Statistical analyses of literature data are provided to establish minimum expected fracture toughness values for use in fracture mechanics design evaluations. Guidance is also provided concerning the potential for component failure and when fracture mechanics assessments are required to guard against unstable fracture. Macroscopic fracture toughness properties are correlated with key microstructural features and operative fracture mechanisms.