J. G. Williams

Imperial College London

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A. J. Kinloch

Imperial College London

B.R.K. Blackman

Imperial College London

M.N. Charalambides

Imperial College London

S. Hashemi

Ferdowsi University of Mashhad

G. P. Marshall

Manchester Metropolitan University

Alojz Ivanković

University College Dublin

Abderrafi M. Ougouag

Idaho National Laboratory

H. Hadavinia

Kingston University

Yatish Patel

Imperial College London

Patrick Griffin

United States Department of the Army

Cooperative Institutions

Imperial College London

University of Illinois Urbana-Champaign

University of Technology Sydney

University of Sydney

University of London

University of Arkansas at Fayetteville

Sandia National Laboratories

Goodwin College

California Institute of Technology

Urbana University

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Modelling deformation and fracture in confectionery wafers

AIP conference proceedings (2015)

Idris K. Mohammed M.N. Charalambides J. G. Williams J. Rasburn

The aim of this research is to model the deformation and fracture behaviour of brittle wafers often used in chocolate confectionary products. Three point bending and compression experiments were performed on beam and circular disc samples respectively to determine the 'apparent' stress-strain curves in bending and compression. The deformation of the wafer for both these testing types was observed in-situ within an SEM. The wafer is modeled analytically and numerically as a composite material with a core which is more porous than the skins. X-ray tomography was used to generate a three dimensional volume of the wafer microstructure which was then meshed and used for quantitative analysis. A linear elastic material model, with a damage function and element deletion, was used and the XMT generated architecture was loaded in compression. The output from the FE simulations correlates closely to the load-deflection deformation observed experimentally.

Brittleness

10.1063/1.4906675

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Citations (0)

Fracture under complex stress — The angled crack problem

International Journal of Fracture Mechanics (1972)

J. G. Williams P.D. Ewing

10.1007/bf00191106

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Citations (512)

Mixed mode partitioning of beam-like geometries: A damage dependent solution

Engineering Fracture Mechanics (2015)

Margaret Conroy A. J. Kinloch J. G. Williams Alojz Ivanković

Mode (computer interface)

Cohesive zone model

10.1016/j.engfracmech.2015.06.061

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Citations (39)

Modelling Dynamic Fracture in Polymers Using a Local Modulus Concept

Springer eBooks (1991)

Alojz Ivanković J. G. Williams

Constant (computer programming)

10.1007/978-94-011-3652-5_27

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Citations (2)

Environmental craze growth in polycarbonate

Polymer Engineering and Science (1981)

Mohammad Hadi Parvin J. G. Williams

Abstract Environmental craze growth in polycarbonate was studied under plane stress and plane strain conditions. In plane stress, the craze growth rate could not be described in terms of either initial stress intensity factor, K o , net or gross stress. In plane strain, K o was found to be the governing factor for craze growth, as has been previously reported for poly(methyl methacrylate) (PMMA). For shallow cracks (<1 mm), there is evidence of an inherent flaw effect.

Polycarbonate

Plane stress

Strain (injury)

10.1002/pen.760211303

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Citations (3)

The toughness of copolymers of polypropylene

Polymer Engineering and Science (1981)

P. L. Fernando J. G. Williams

Abstract A series of fracture mechanics tests of a set of random and impact copolymers of polypropylene, in which the ethylene content was varied, is described. The plane strain toughness is found to change from the homopolymer value, but thereafter to be independent of ethylene content. The yield stress of the impact copolymers decreases markedly with ethylene content, while that for random copolymers increases only slightly. This is reflected in toughness values in tension. A comparison with the behavior of other rubber‐modified materials is made and it is concluded that crazing is an important mechanism in polypropylene and is perhaps more rate and temperature sensitive than in acrylonitrile‐butadiene‐styrene (ABS).

Crazing

Polypropylene

10.1002/pen.760211504

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Citations (36)

The melting behavior of a low density polyethylene powder in a screw extruder

Polymer Engineering and Science (1981)

A. Cox J. G. Williams D. P. Isherwood

Abstract An experimental investigation into the performance in general and the melting behavior in particular of a single screw extruder running with a low density polyethylene power has been carried out and the results compared with those for a granular feedstock of low density polyethylene having similar melt properties. It was found that the tendency was for the output rate, pressure generated and specific power consumption to be lower for the powders, and that the removal of barrel heating near the feed hopper increased these parameters. Two melting mechanisms were observed in powder extrusion; one being the classic “Maddock” type, and the other such that the solid bed and melt pool were in reversed positions relative to the Maddock case. There was a trend for this latter mechanism to operate with low screw speeds, shallow channels and full heating. Melt initiation occurred nearer the feed end and melting was completed much more quickly with powders. An explanation of the mechanisms is proposed which is based on the observation of early melt initiation, and the industrial practices of feed zone cooling and increasing feed pressure generation to improve the performance of extruders running with powders are seen to be consistent with this proposition.

10.1002/pen.760210206

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Citations (9)

Pressure Vessel Steel Embrittlement Monitoring by Magnetic Properties Measurements

JF Stubbins W-J Shong M. J. Giacobbe Abderrafi M. Ougouag J. G. Williams

The magnetic properties of specimens of one heat of A533B nuclear pressure vessel grade steel have been examined in the as-received condition and after neutron irradiation to various fluence levels up to 4 × 1018 cm-2 (E > 0.1 MeV) in the University of Illinois advanced TRIGA reactor core at two temperatures, approximately 120 and 260°C. The effect of certain heat treatments was also investigated. The magnetic properties were measured by an automated hysteresis curve-tracing method using a miniature transformer which incorporated the specimens in its core. Changes in magnetic hysteresis energy loss were correlated with neutron fluence in the case of certain irradiated specimens and with microhardness measurements in the case of heat-treated specimens. At the higher irradiation temperatures, no significant changes in either the magnetic hysteresis properties or the microhardness were noted for the present fluences. The relationship between the observed magnetic properties response and irradiation-induced embrittlement is discussed.

Embrittlement

10.1520/stp12717s

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Citations (7)

Fracture at bimaterial interfaces: the role of residual stresses

Journal of Materials Science (1991)

A. J. Kinloch Ekachai Thrusabanjong J. G. Williams

10.1007/bf02387802

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Citations (33)

Single and multi-specimenR-curve methods forJ IC determination of toughened nylons

Journal of Materials Science (1991)

S. Hashemi J. G. Williams

Single specimen

10.1007/bf00588296

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Citations (33)