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Dive into the research topics where Luc J. Vandeperre is active.

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Featured researches published by Luc J. Vandeperre.


Journal of Materials Research | 2004

Effect of elastic surface deformation on the relation between hardness and yield strength

Luc J. Vandeperre; F. Giuliani; W.J. Clegg

The use of an analytical approach to determine the relation between hardness and yield strength for materials with a high ratio of yield strength to Youngs modulus is re-examined. It is shown that predictions using the analogy of the spherical cavity fail to reproduce experimental and finite element results because the surface deflection that occurs during loading is not taken into account. A modification is proposed to allow this. This gives a greatly improved prediction of the relationship between the hardness and yield strength of a material. It also enables the effect of the indenter shape on the measured hardness to be incorporated and explains why in some very hard materials, indentation is observed to be completely elastic.


Journal of Materials Science | 2008

The effect of porosity in thermal shock

Chen Yuan; Luc J. Vandeperre; Robert J. Stearn; W.J. Clegg

The effects of porosity on cracking during thermal shock have been studied by directly observing the cracks that formed after quenching heated porous alumina bars into water. The porosity was introduced by adding different volume fractions of fugitive inclusions and the behaviour compared with that obtained by partial sintering of a powder compact. Where fugitive inclusions had been used, there was little effect of either pore size or pore volume fraction over the ranges studied. The extent of cracking was always slightly less than that of a monolithic, dense alumina and gave reasonable agreement with predictions using experimentally measured data. However, cracks grew much further in the partially sintered material. This discrepancy became greater as the temperature change increased, inconsistent with existing analyses. It is suggested that this difference in behaviour arises predominantly because of the greater measured fracture energy of the alumina made using fugitive inclusions compared with that made by partial sintering.


MRS Proceedings | 2003

Tailoring strains through microstructural design

Luc J. Vandeperre; W.J. Clegg

Composite structures are presented that allow a wide design space for strains in response to an applied stimulus to be accessed. The basic principle of operation is described and examples of how it can be used to obtain a range of behaviours are given. Experiments were conducted to assess the basic behaviour of building blocks for such composites and it is shown that the results agree reasonable with simple predictions made by considering bending and stretching of the beams in the structures.


2003 International Electronic Packaging Technical Conference and Exhibition, Volume 2 | 2003

A Package for Thermal Compensation of Fiber Bragg Gratings

Alison L. Howlett; Luc J. Vandeperre; W.J. Clegg

A new package for thermally compensating a fiber Bragg grating, which requires less accuracy in positioning the fiber onto the device, is discussed. Experiments show that it can reduce the shift in reflected wavelength from 1575 pm to 78 pm for a temperature change of 120 K. The deformation of the package showed no hysteresis, and the effective thermal compensation is repeatable over many cycles. Furthermore the package also has the potential to give non-linear thermal compensation for fiber Bragg gratings.Copyright


MRS Proceedings | 2002

The Growth of Bamboo-Structured Carbon Tubes Using a Copper Catalyst

B.L. Farmer; D.M. Holmes; Luc J. Vandeperre; Robert J. Stearn; W.J. Clegg

Abstract : Catalytic decomposition of methane has been used to grow bamboo-structured carbon tubes at temperatures ranging from 1233 K to 1291 K. No tube growth was observed at temperatures less than 1233 K, whilst above 1291 K pyrocarbon was the dominant product. It is shown that the average size of the copper catalyst particles was influenced by the reaction temperature, with the reciprocal of the maximum size of the copper particle decreasing linearly with temperature. This is consistent with the idea that the melting point can be reduced by surface energy effects. Observations show that under the conditions here the catalyst particle penetrates into the carbon fibre and a mechanism is proposed for development of the bamboo structure based upon the energy changes that take place.


Acta Materialia | 2007

The hardness of silicon and germanium

Luc J. Vandeperre; F. Giuliani; S. J. Lloyd; W.J. Clegg


Journal of the American Ceramic Society | 2001

Thermal Shock of Layered Ceramic Structures with Crack‐Deflecting Interfaces

Luc J. Vandeperre; Annika Kristofferson; Elis Carlström; W.J. Clegg


25th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: B: Ceramic Engineering and Science Proceedings, Volume 22, Issue 4 | 2008

Effect of Grain Size on the Fracture Behaviour of Porous Alumina Made by Partial Sintering of Powder Compacts

J. Wang; Luc J. Vandeperre; W.J. Clegg


Archive | 2001

Platform with controlled thermal expansion coefficient

W.J. Clegg; Anthony Kelly; Robert J. Stearn; Luc J. Vandeperre


MRS Proceedings | 2003

Mechanisms controlling the hardness of Si and Ge

Luc J. Vandeperre; F. Giuliani; S. J. Lloyd; W.J. Clegg

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W.J. Clegg

University of Cambridge

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F. Giuliani

University of Cambridge

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J. Wang

University of Cambridge

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S. J. Lloyd

University of Cambridge

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Anthony Kelly

University of Southampton

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B.L. Farmer

University of Cambridge

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C. Yuan

University of Cambridge

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