We present a model for the brittle–ductile transition in ferritic steels based on two dimensional discrete dislocation simulations of crack-tip plasticity. The sum of elastic fields of the crack and the emitted dislocations defines an elasto–plastic crack field. Effects of crack-tip blunting of the macrocrack are included in the simulations. The plastic zone characteristics are found to be in a...

This report presents the outcome of four fracture test series, addressing the ductile-to-brittle toughness behaviour of a nuclear reactor pressure vessel steel. Each test series corresponds to a specific test specimen geometry, tensile or three-point-bend, with a given degree of crack-tip constraint. A brief overview is given of available constraint-based fracture mechanics methodologies in the...

A finite-element procedure is developed to analyze plane ductile fracture problems in the presence of largescale yielding near the crack tip. Strain and stress singularities near the crack tip, corresponding to the strainhardening material model, are embedded in elements near the crack tip. The developed elastic-plastic incremental finite-element method is based on a hybrid displacement model. ...

The tensile fractures of ultrafine-grained (UFG) Al-Mg alloy with a bimodal grain size were investigated at the microand macroscale using transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with focused ion beam (FIB), and optical microscopy. The nanoscale voids and crack behaviors near the tensile fracture surfaces were revealed in various scale ranges and provi...

Fracture mode of ductile solids can vary depending on the history of stress state the material experienced. For example, ductile plates under remote in-plane loading are often found to rupture in mode I or mixed mode I/III. The distinct crack patterns are observed in many different metals and alloys, but until now the underlying physical principles, though highly debated, remain unresolved. Her...

Cyclical fatigue may influence the appearance and propagation of the type of fracture of an endodontic instrument. The aim of this study was to assess the influence of cyclic fatigue on morphological features of torsional fracture in Pathfile nickel-titanium rotary instruments for surgical preparation in endodontics. Thirty new Pathfile instruments (Dentsply- Maillefer. Ballaigues-Switzerland) ...

Failure in sheet metal structures of ductile material is usually caused by one of, or a combination of, ductile fracture, shear fracture or localised instability. In this paper the failure of the high strength steel Docol 600DP and the ultra high strength steel Docol 1200M is explored. The constitutive model used in this study includes plastic anisotropy and mixed isotropic-kinematic hardening....

Hyaluronan (HA) is a natural polyelectrolyte with distinctive biological functions. Cross-linking of HA to generate less degradable hydrogels for use in biomedical applications has attracted interest over many years. One limitation of HA hydrogels is that they are very brittle and/or easily dissolve in physiological environments, which limit their use in load-bearing applications. Herein, we de...

Ductile fracture and extremely low cycle fatigue (ELCF) [1] are two common failure modes in aircraft engines and turbomachinery designs [2]; however, the linkage between these two failure modes under multi-axial loading conditions has never been systematically studied. Inconel 718 (IN718) is one type of high temperature alloys widely used in turbomachines. Specially designed specimens and tests...

in the present research, damage mechanisms during room temperature uniaxial tensile testing of two different modern high strength dual phase steels,dp780 and dp980, were studied. detailed microstructural characterization of the strained and sectioned samples was performed by scanning electron microscopy (sem). the results revealed that interface decohesion, especially at the triple junctions of...