Publications de Václav Pejchal

Laser powder-bed fusion of a high entropy alloy with outstanding intrinsic mechanical properties

Roland Logé, Cyril Cayron, Jamasp Jhabvala, Václav Pejchal, Navid Sohrabi

In the past few years, laser powder-bed fusion (LPBF) of high entropy alloys (HEAs) has gained significant interest. We investigated a HEA (PdPtRhIrCuNi) elaborated by LPBF, and studied its microstructure and mechanical properties. This alloy has potential ...

ELSEVIER SCIENCE SA2023

On the diametric compression strength test of brittle spherical particles

Andreas Mortensen, Goran Zagar, Václav Pejchal

Diametric compression testing can be used to measure the hoop strength of spherical particles if one uses platens whose deformation behaviour is tailored in a way that allows the particles to sink sufficiently far into the platens before particle fracture ...

2018

Meridian crack test strength of plasma-sprayed amorphous and nanocrystalline ceramic microparticles

Andreas Mortensen, Goran Zagar, Václav Pejchal, Marta Fornabaio

2018

Compression testing spherical particles for strength: Theory of the meridian crack test and implementation for microscopic fused quartz

Andreas Mortensen, Goran Zagar, Raphaël Charvet, Cyril Dénéréaz, Václav Pejchal

We show that uniaxial compression testing of spherical particles can give unambiguous access to their tensile strength as governed by surface flaws if one uses pairs of elasto-plastic platens, tailoring their hardness in order to control the relative area ...

2017

The local strength of individual alumina particles

Andreas Mortensen, Goran Zagar, Václav Pejchal, Marta Fornabaio

We implement the C-shaped sample test method and micro-cantilever beam testing to measure the local strength of microscopic, low-aspect-ratio ceramic particles, namely high purity vapor grown a-alumina Sumicorundum (R) particles 15-30 mu m in diameter, kno ...

2017

Probing the micromechanical strength of oxide ceramic composite reinforcements

Václav Pejchal

This work shows how one can probe the micromechanical strength of ceramic reinforcements used in metal matrix composites, which greatly influences the mechanical performance of the composite material yet has seldom been quantified with precision. More spec ...

EPFL2017

Fracture toughness measurement in fused quartz using triangular chevron-notched micro-cantilevers

Andreas Mortensen, Goran Zagar, Lionel Michelet, Martin Guillermo Mueller, Václav Pejchal

We extend to flat surfaces the fracture toughness method presented in Acts Materialia vol. 86 (2015) p.385 and measure in this manner the fracture toughness of fused quartz. Tests give 0.67 +/- 0.01 MPa m(1/2) which agrees with earlier microscopic and macr ...

Elsevier2016

Fracture toughness testing of nanocrystalline alumina and fused quartz using chevron-notched microbeams

Andreas Mortensen, Marco Cantoni, Goran Zagar, Martin Guillermo Mueller, Václav Pejchal

We show that chevron-notched samples offer an attractive approach to the measurement of fracture toughness in micron-scale samples of brittle materials and use the method to characterize quartz and nanocrystalline alumina. Focused ion beam milling is used ...

Elsevier2015

The local strength of microscopic alumina reinforcements

Andreas Mortensen, Marco Cantoni, Goran Zagar, Andreas Rossoll, Martin Guillermo Mueller, Václav Pejchal

We measure, using an adaptation of a method designed for ceramic ball bearings, the local strength of a brittle second phase that serves to reinforce a metal. The method uses focused ion beam milling and a nanoindentation device, and is free of artifacts c ...

Elsevier2015

On measuring fracture toughness under load control in the presence of slow crack growth

Andreas Mortensen, Goran Zagar, Martin Guillermo Mueller, Aparna Singh, Václav Pejchal

The influence of slow crack growth in ceramics on the measurement of their fracture toughness under steadily increasing controlled load (as is generally practiced in microscale testing) is analyzed to identify conditions under which the phenomenon can caus ...

Elsevier2015