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Dr. Hanaor - Department of Ceramic Materials - TU Berlin's blog

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An improved semi-analytical solution for stress at round-tip notches

Highlights

 

A semi-analytical model is developed for the notch tip maximum stress.

Application of the formula to U and blunt V-notches is demonstrated.

The results can be used to assess the brittle failure of notched components.

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Novel porous materials by freeze casting

in recent years the technique of freeze casting has undergone tremendous development. New techniques and novel nanoscale building blocks have given rise to porous materials with extraordinary properties. As an example, by spinning freeze cast fibre with aligned pores fabrics with unprecedented levels of thermal insulation could be produced. This 

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Electrical contact resistance and its dependence on applied pressure

The relationships between surface roughness, contact pressure and contact resistance are studied in this work published three years ago.

It is imporant to distinguish between the different conduction mechanisms acting at contacts at different scales, in order to better understand how surface structure and surface chemistry can alter the behaviour of electrical contacts

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Freeze casting of novel materials

Freeze casting presents exciting new avenues towards high performance materials with aligned pore structures.

Bone scaffolds, highly elastic composites and nacre mimetic materials can all be produced by means of freeze casting methods. 

This comprehensive review presents recent development in terms of materials and processing

 

 

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Electro-mechanical behaviour or rough surfaces

Understanding electrical contact resistance 

Electrical contact resistance at interfaces between pairs of rough surfaces is of great importance in the performance of diverse systems, particularly in miniaturised electromechanical systems containing switches.

 

In this study, the role of pressure and surface structure is explored with a view towards gaining a beter understanding of electrical contact resistance.

 

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Elastic behavior in porous materials

In the work shown here:

Multiscale modeling of effective elastic properties of fluid-filled porous materials

The elastic deformation and its dependence on fluid displacement is studied at two distinct scales, to address the multi-scale nature of porous structures in nature.

 

 

 

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Electrical resistance at rough surfaces in contact

Electrical Contact Resistance of Fractal Rough Surfaces 

 

The presence of roughness at electrical contacts tends to involve contacting asperities across multiple scales. Depending on the nature of the contact between asperities on opposing surfaces, different conduction mechanisms take place. This is shown in the figure here.

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Contact stiffness of rough surfaces

Contact stiffness of multiscale surfaces by truncation analysis

 

In this concise piece of work, an effective method is shown to gain new understandings into the role of surface structure in the field of contact mechanics. In particular, normal contact stiffness is correlated to parameters of surfaces' fractal dimension and amplitude. 

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3D printing of simulated geomaterials

3D printable geomaterials

https://doi.org/10.1680/jgeot.15.P.034

This work, dating back to 2015 demonstrates the simulation of grain morphologies for subsequent fabrication of surrogate geomaterials 

 

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The remarkable mechanical properties of crumpled materials

Mechanics of crumpled materials

Crumpled materials exhibit unusual and as yet unexpained mechanical properties. Through the surprisingly complex morphologies of facets and ridges formed in the crumpling of paper into a ball or densser materials, very high strength to weight ratios can emerge.

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Compressive performance of MAX phase composites

Compressive performance and crack propagation in MAX phase composites 

 

Here micro CT was used to reveal the structure performance relationships in metal/ceramic composites based on Ti2AlC / Al alloy combinations.

The results show the promise of infiltrated max phase materials in the production of high performance composites.

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