Material grain size and crack size influences on cleavage fracturing

2019

Metals

Dislocation pile-up and thermal activation influences on the deformation and fracturing behaviors of polycrystalline metals are briefly reviewed, as examples of dislocation mechanics applications to understanding mechanical properties. To start, a reciprocal square root of grain size dependence was demonstrated for historical hardness measurements reported for cartridge brass, in line with a similar Hall-Petch grain size characterization of stress-strain measurements made on conventional grain size and nano-polycrystalline copper, nickel, and aluminum materials. Additional influences of loading rate (and temperature) were shown to be included in a dislocation model thermal activation basis, for calculated deformation shapes of impacted solid cylinders of copper and Armco iron materials. Connection was established for such grain size, temperature, and strain rate influences on the brittle fracturing transition exhibited by steel and other related metals. Lastly, for AISI 1040 steel material, a fracture mechanics based failure stress dependence on the inverse square root of crack size was shown to approach the yield stress at a very small crack size, also in line with a Hall-Petch dependence of the stress intensity on polycrystal grain size.

Section: Brittle Fracturing and Fracture Mechanicsmentioning

confidence: 99%

Section: The Ductile-to-brittle Transition Temperature (Dbtt)mentioning

confidence: 99%

Dislocation Mechanics Pile-Up and Thermal Activation Roles in Metal Plasticity and Fracturing

2019

Metals

“…An updated review has been presented [16]. An analogous relationship to the crack size dependence of the fracture mechanics properties of metals and related materials has been established [17].…”

Section: Crystal Polycrystal Nanopolycrystal Deformationsmentioning

confidence: 99%

Crystal Dislocations

2016

Crystals

Crystal dislocations were invisible until the mid-20th century although their presence had been inferred; the atomic and molecular scale dimensions had prevented earlier discovery. Now they are normally known to be just about everywhere, for example, in the softest molecularly-bonded crystals as well as within the hardest covalently-bonded diamonds. The advent of advanced techniques of atomic-scale probing has facilitated modern observations of dislocations in every crystal structure-type, particularly by X-ray diffraction topography and transmission electron microscopy. The present Special Issue provides a flavor of their ubiquitous presences, their characterizations and, especially, their influence on mechanical and electrical properties.

“…Related theoretical analyses in the former case are in [63,64] and, for glass material, to essentially static hardness testing by Rouxel [55] and applied to hierarchical structural aspects of tooth enamel by Yilmaz et al [65]. Other benefits of structural considerations dealing with experimental fractographic analyses, building onto Hull's attribution to Hooke [3], are provided in [66,67], relating also to an exposition of ductile versus brittle fracturing considerations in the articles by Tekoglu et al [68], Armstrong [48], Knott [69] and Matic et al [70].…”

mentioning

confidence: 99%

“…Towards the 'opposite' crystal/polycrystal/nanopolycrystal level of size scale, coverage is provided by Antolovich [47], Armstrong [48], Hohenwarter & Pippan [49], Ovid'ko [50] and Pineau [51]. Emphasis is given by these authors to the importance of crystal/grain boundaries.…”

mentioning

confidence: 99%

Fracturing across the multi-scales of diverse materials

Phil. Trans. R. Soc. A.

Antolovich

Griffiths

et al. 2015

Everyone has to deal with fracturing of materials at one level or another, beginning from normal household chores and extending to the largest scale of observations reported for catastrophic events occurring on a geological level or even expanded to events in outer space. Such wide perspective is introduced in the current introduction of this theme issue. The follow-on organization of technical articles provides a flavour of the range in size scales at which fracturing occurs in a wide diversity of materials—from ‘fracking’ oil extraction and earth moving to laboratory testing of rock material and extending to the cracking of tooth enamel. Of important scientific interest are observations made and analysed at the smallest dimensions corresponding to the mechanisms by which fracture is either enhanced or hindered by permanent deformation or other processes. Such events are irrevocably linked to the atomic structure in all engineering materials, a sampling of which is presented, including results for crystalline and amorphous materials. Hooray for the broad subject description that is hoped to be appealing to the interested reader.