Publications de Andreas Mortensen

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It has been proposed in the literature, based on theoretical considerations and on finite-element calculations, that all three stress tensor invariants govern the yield surface of cellular materials. Recent experiments on 75 gm pore size aluminium replicat ...

A new process for the production of metal matrix composites, whereby molten metal is forced into the interstices of a fibrous preform using electromagnetic body forces, is presented. These forces are created by subjecting the molten matrix to a concentrated transient magnetic field which, in turn, induces intense eddy currents in the melt. This gives rise to Lorentz forces which propel the metal into the preform. Equations governing the mechanics of Lorentz force infiltration of an axisymmetric preform surr

Seven alloys of the ternary Au-Cu-Pt system, containing 75 or 76.5 wt.% Au with 0-15 wt.% Pt and heat-treated to a fully ordered condition, are examined using in-situ synchrotron radiation to determine transformation temperatures and phases formed, and to ...

We present here a study of the mechanical behavior of cellular Zn and Zn1.5Mg with densities between 11.9 and 24.5%, produced by replication processing using NaCl as a spaceholder. Cellular Zn and Zn1.5Mg deform homogeneously during quasi-static compressio ...

Different predictive models-the Maxwell mean field approach, the differential effective medium scheme, the 2- and 3-phase self-consistent, and 3-point model-for the electrical conductivity of two-phase materials are assessed based on electrical conductivity measurements of metal matrix composites with non-conducting inclusions produced by gas pressure infiltration. The volume fraction of non-conducting phase, namely equiaxed or angular alumina particles of various sizes and size-distributions embedded in a

In the pressure infiltration of metal matrix composites, molten metal is injected under external pressure into a porous preform of the reinforcing material. Equilibrium capillary parameters characterizing wetting for this process are summarized in plots of ...

Following a review of the processing of functionally graded metals and metal-ceramic composites in Part 1; this Part 2 of the two part series focuses on the thermomechanical behaviour. The paper begins with an overview of the fundamentals of thermoelastic and thermoplastic deformation in metal-ceramic composites. Various approaches, including the rule of mixture approximations, mean field theories, crystal plasticity models, discrete dislocation models, and continuum finite element formulations of the const

Composite materials are often produced by pressure-infiltration of a liquid matrix into a preform of packed solid fibers or particles. Capillary forces that intervene in this process are quantified by measuring saturation curves, which are plots of the fraction pore space filled with the matrix versus the pressure difference between the matrix and the atmosphere initially present in the porous preform to be infiltrated. We have constructed an apparatus capable of measuring saturation curves at high temperat

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 ...

The work needed to mechanically drive molten metal into a porous solid preform when producing a composite material by infiltration can significantly exceed the energy change required for thermodynamically reversible infiltration. We measure, by quantitativ ...

A microcasting process is used to produce high aspect ratio ( > 30) monocrystalline pure aluminium wires with a diameter between 14 and 115 mu m. The role of thermal activation in the plastic deformation of these microwires is measured by means of (single) ...

Femtosecond laser exposure of fused silica combined with chemical etching has opened up new opportunities for three-dimensional freeform processing of micro-structures that can form complex micro-devices of silica, integrating optical, mechanical and/or fluidic functionalities. Here, we demontrate an expansion of this process with an additional fabrication step that enables the integration of three-dimensional embedded metallic structures out of useful engineering metals such as silver, gold, copper as well

Open-pore replicated microcellular 99.99% pure aluminium is tested in tensile creep, varying the temperature from 150 to 450 degrees C, the applied stress from 0.15 to 0.5 MPa, and the relative density from 0.14 to 0.28. Tensile creep curves are of classic ...

Ternary Au-Cu-Pt alloys, of unequal gold and copper atomic contents and containing 2.5 wt.% Pt, are ordered isothermally at 250 or 400 degrees C after annealing at 650 degrees C and quenching in water. The alloys are characterized by transmission electron ...

The processing, mechanical analysis, and performance of functionally graded materials containing a metallic phase is reviewed in two parts. This first part focuses on processing, and distinguishes two principal process classes in graded materials production. The first class, termed' constructive processes', produces gradients by stacking selectively two or more starting materials, allowing full and potentially automated control of compositional gradients. The second class is termed 'transport based processe

Cu-Ni-Sn alloys with Pb additions exhibit high mechanical strength at room temperature coupled with good machinability but experience a significant ductility loss above the melting point of lead. We explore here the influence of minor additions of Al, Mn, ...

The in situ matrix flow stress of continuous fibre-reinforced aluminium is measured in tension along the fibre axis. We use a new, tighter, estimate for the effect differential Poisson contraction between fibres and matrix and take into consideration nonli ...

An iterative Finite Element method predicated on a linearization of the weak form around a reference configuration is derived for general, three-dimensional, free-surface flows, including systems with arbitrary contact angles. This sharp-interface method is a rigorous generalization of the Total Linearization Method that was proposed by Kruyt et al. (International Journal for Numerical Methods in Fluids 1988; 8: 351–363) for two-dimensional flows with contact angles limited to 90◦. In contrast to existing n

The high-temperature wettability of alumina particulate preforms by copper is investigated by means of infiltration experiments conducted at 1473 K under low oxygen partial pressure. Wetting is quantified in terms of drainage curves, which plot the volume ...

In this work, the macrotexture of dense Zn produced by laser powder bed fusion (LPBF) was studied and the mechanical properties for different tensile bar orientations were measured. The compressive strength of LPBF Zn scaffolds with five different unit cel ...

Andreas Mortensen

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Yield surface of polyurethane and aluminium replicated foam

Lorentz Force Infiltration Of Fibrous Preforms

Solid state transformations of Au-Cu-Pt alloys studied by in-situ X-ray synchrotron radiation and DSC

Mechanical properties of replicated cellular Zn and Zn1.5Mg in uniaxial compression

On the electrical conductivity of metal matrix composites containing high volume fractions of non-conducting inclusions

Capillarity in pressure infiltration: improvements in characterization of high-temperature systems

Functionally graded metals and metal-ceramic composites .2. Thermomechanical behaviour

Capillarity in pressure infiltration: influence of percolation and wetting angle

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

Surface energy contributions to the work of infiltration in metal matrix composite processing

The thermally activated deformation behaviour of single-crystalline microcast aluminium wires

Femtosecond laser assisted 3-dimensional freeform fabrication of metal microstructures in fused silica

Creep of replicated microcellular aluminium

L10 nanotwinned gold-rich Au–Cu–Pt

Functionally graded metals and metal-ceramic composites .1. Processing

Improvement of elevated temperature mechanical properties of Cu–Ni–Sn–Pb alloys

In situ flow stress of pure aluminium constrained by tightly packed alumina fibres

Generalization of the total linearization method to three-dimensional free-surface flows

Wetting in infiltration of alumina particle preforms with molten copper

Mechanical properties and cytocompatibility of dense and porous Zn produced by laser powder bed fusion for biodegradable implant applications