9am - 4pm
Monday 26 April - Friday 30 April 2021

Second MATHEGRAM advanced training course: Emerging applications of granular materials

Led by SIMaP, CNRS and University of Grenoble Alpes (France), this training course focuses on the challenges and opportunities for the application of granular materials in emerging areas of material science. The courses will be delivered by world leading experts, both from within the MATHEGRAM network and externally.

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This training school is free for MATHEGRAM members. If you are a member of the public then please contact us to find out more information.

Overview

Topics

The second MATHEGRAM advanced training course covers the following topics:

  • Characterization of polymer powders
  • Refractory materials
  • Sintering
  • Fluid and grains interactions
  • X-ray tomography: sintering and additive manufacturing
  • X-ray tomography: Insight into granular materials
  • Discrete simulation of powder sintering.

Programme

Please note: All times are in the Central European Summer Time (GMT+2).

TimeActivitySpeaker
9am - 9:15amWelcome and introductionProfessor Charley Wu, MATHEGRAM Coordinator and Christophe Martin ATC2 Organiser
9:15am - 12 noon

Early stage researcher presentations

10 min presentations (questions included) and 15 min break.

Chaired by WP leads
12 noon - 2pmBreak
2pm - 4pmThe technology of speciality, functional  particulate product manufacturingHugh Stitt, Matthey

TimeActivitySpeaker
9am - 10amX-ray tomography in materials scienceLuc Salvo, University of Grenoble Alpes
10am - 11amMeasuring 3D granular deformation with repeated x-ray tomographyEdward Ando, University of Grenoble Alpes
12 noon - 2pmBreak
2pm - 3pmFundamentals of powder sinteringDidier Bouvard, University of Grenoble Alpes
3pm - 4pmFrom rock to road: How Astec is improving sustainability in infrastructure with simulationAndrew Hobbs, Astec Industries, Inc

TimeActivitySpeaker
9am - 10amX-ray tomography for sintering and additive manufacturing investigationsPierre Lhuissier, University of Grenoble Alpes
10am - 11am

Insight into granular materials from tomography:

  • Natural and engineered sands
  • Semi-solid metals
Catherine O'Sullivan, Imperial College
11am - 2pmBreak
2pm - 2:30pmDiscrete simulation of powder sinteringChristophe Martin, University of Grenoble Alpes
2:30pm - 4pmPolymer derived composite ceramic coatings and jointsRaj Bordia, Clemson University

TimeActivitySpeaker
9am-10amFluid and grains interactionsPierre Jop, Saint-Gobain
10am- 11amWet powders in the pharmaceutical industry: numerical approaches for coating and granulationMaryam Askarishahi, Research Center Pharmaceutical Engineering
11am- 2pmBreak
2pm- 3pmThe relevance of particle mechanics concepts in SLSMassimo Poletto, Department of Industrial Engineering, University of Salerno
3pm- 4pmChallenges and opportunities for the characterisation of polymer powders for the selective laser sintering processEnrico Gallino, Ricoh

TimeActivitySpeaker
9am-10amThe multi-particles finite-element methodBarthelemy Harthong, University of Grenoble Alpes
10am - 11amRefractory materialsSéverine Roméro, Vesuvius
11am - 2pmBreak
2pm - 3pmIndustrial applications: Materials at high temperature in Saint-GobainPierre Jop, Saint-Gobain
3pm - 4pmMicrostructure-based modelling of snow mechanicsPascal Hagenmuller, Centre d’Etudes de la Neige, CNRM, Météo-France - CNRS

Book your place

If you would like to attend this training school then please register your interest.

Abstracts

Speaker

Title and abstract

Hugh Stitt, Matthey

The technology of speciality, functional particulate product manufacturing

Catalysts, e-catalysts and battery materials are functional particulate products, structured at scales from nm to mm. Their manufacture involves a significant amount of particle and powder processing technology.

The presentation will review the manufacturing processes from a powder technology perspective, with specific case studies in:

  • General powder flow, particle formation
  • Wet particulate systems (high solids content dispersions, wet powders)
  • Size reduction
  • Product forming (pelleting)
  • Thermal processing (rotary calciners)
  • Considering the role of theory and modelling in design.

Luc Salvo, SIMaP, UGA, CNRS

X-ray tomography in materials science

X-rays are known since 1895 and have been employed widely for materials characterisation since that time.

However, the relevant scale in materials can be very small and it is only since less than 30 years that x-ray tomography with spatial resolution of the order of few microns became possible thanks to large instrument facilities. This is now currently available in laboratory tomograph and nano scale are now available at the large instrument.

Beside this change of spatial resolution with time a huge change in acquisition time occurs starting from several hours for one 3D image to less than seconds now. We will review the main important parameters for 3D tomography and the evolution with time as well as the application that can be done in materials science with a focus on in situ tomography.

Edward Ando, 3SR, Univ. Grenoble Alpes

Measuring 3D granular deformation with repeated x-ray tomography

In this talk I'll go into details of measuring strains from deformations of particle assemblies starting from series of x-ray tomography images.

We'll briefly cover particle identification, go onto measuring particle kinematics with optical-flow or particle-tracking methods, and move onto strain quantification. I'll be using this software to illustrate the process with live examples.

You can play around with the data beforehand (M2EA05).

Didier Bouvard, SIMaP, UGA, CNRS

Fundamentals of powder sintering

Sintering is the major step of the route transforming a metal or ceramic powder into a bulk material. This transformation involves various temperature-activated physico-mechanical phenomena that strongly depend on powder composition and features (mainly, particle size).

The control of these phenomena allows tailoring the microstructure and thus the properties of the sintered material.

Andrew Hobbs, Astec Industries, Inc

From rock to road: How Astec is improving sustainability in infrastructure with simulation

Hot mix asphalt (HMA) is one of the most common materials for road construction and is 100 per cent recyclable. While recycled asphalt product (RAP) is widely available and inexpensive, processing challenges means that RAP usage in new road construction is relatively low (22 per cent in the USA and 17 per cent in Europe).

As an equipment manufacturer Astec uses simulation to improve equipment design to increase RAP processing capacity, but the changing thermo-mechanical characteristics of HMA during the production and recycling process has required the development of new particle-scale models, to address complex multiphysic phenomena such as liquid coating and mixing, and conductive and convective heat transfer.

We will review successes and where gaps remain in the process of simulating HMA production and RAP processing.

Pierre Lhuissier, SIMaP, UGA, CNRS

X-ray tomography for sintering and additive manufacturing investigations

X-ray tomography covers a wide range of specifications: From the micro CT lab equipment to the nano-tomography at synchrotron the temporal and spatial resolutions ranges over several orders of magnitude.

Applications of x-ray tomography in the fields of powder sintering and additive manufacturing are presented emphasising on the relationship between the imaging performances and the characterised phenomena.

Catherine O'Sullivan, Imperial College

Insight into granular materials from tomography: (i) natural and engineered sands (ii) semi-solid metals

This talk will show how micro-CT data can be used to study the fabric of sands. The presentation will focus both on characterising the fabric of sands looking at the particles and the contacts as well as considering the void space. The ability to use micro-CT data and DEM data in a complementary way to advance understanding of the pore-space topology and the ability of granular materials to act as a filter.

The talk will also highlight some recently completed work on semi solid metals which can be viewed as a granular material. The work on semi-solid metals has involved radiography, DEM simulations and high temperature triaxial testing.

Christophe Martin, SIMaP, UGA, CNRS

Discrete simulation of powder sintering

This talk reviews recent advances in simulations based on the discrete element method (DEM) applied to sintering of powders. Constrained sintering provides a good example on the possibilities of a discontinuous approach to tackle crack growth (or healing) problems with DEM.

Raj Bordia, University of Clemson

Polymer derived composite ceramic coatings and joints

The pyrolysis of Si-based polymeric precursors to make composite ceramics offers many advantages over conventional ceramic processing. This is especially true for ceramic coatings and for joining and bonding ceramics. Advantages include ease of green state processing, ability to form a ceramic material at low temperatures, and form high purity, tailorable composites.

After an overview of the polymer derived ceramics, results on the processing, properties and performance of ceramic coatings and joints will be presented. We have investigated the mechanics of constrained pyrolysis for ceramic coatings. It is shown that the stresses generated in the coating due to the constraint from the substrate can lead to cracking in the coating.

A critical thickness below which cracking does not occur has been calculated. It has been shown that this depends on the free (unconstrained) shrinkage of the coating. The predictions of this analysis have been experimentally verified.

We have also modified the Landau-Levich analysis to make coatings of controllable thickness using dip-coating process. We use these calculations and analysis to develop robust processes to make high performance composite ceramic coatings on both ceramics and metals and for joining of ceramics and ceramic matrix composites.

The mechanical properties of joints and coatings, including the fracture toughness of the interface and high temperature strength of the joints, will be presented. The effectiveness of the coatings as environmental barrier, corrosion resistant coatings and to control surface energy will also be discussed.

Pierre Jop, Saint Gobain

Fluid and grains interactions

The interaction of a fluid with granular materials can alter their behavior. In this lecture, we will consider the impact of fluid motion on the behavior of the grains illustrated by different industrial cases.

From low liquid content to excess of liquid, we will focus on the different physical mechanisms governing some processes such as the mixing of building materials with water. The viscosity and the capillarity of the fluid are the main ingredients. The mechanics of wet granular matter as well as the transition from dry to wet grains will be presented.

Maryam Askarishahi, Research Center Pharmaceutical Engineering

Wet powders in the pharmaceutical industry: numerical approaches for coating and granulation

Granulation of wet powders is extensively used in the pharmaceutical industry. The aim of granulation is mainly to:

  • Improve flow, porosity, content uniformity
  • Avoid segregation
  • Control the rate of drug release
  • Decrease dust generation.

In a granulator, particles are converted into large agglomerates called granules. This process involves two steps:

  1. Particle coating: Wetting the particles with a binder solution
  2. Particle agglomeration: Bringing the wet powers into contact resulting in size enlargement.

In the case of using a fluid bed granulator, granule drying is also integrated into the granulation. 

Due to the complexity of the particle and droplet interactions in the granulation process, numerical tools are essential to obtain an in-depth understanding of particle collision and growth.

In this lecture, we will focus on the numerical approaches which are employed to investigate the granulation in three different scales. In the micro- and meso-scale simulation approaches, we study the interaction of wet powers and formation of the liquid bridge to obtain deep insight into the wet powders’ agglomeration.

The most common approaches in these scales are detailed simulation such as direct numerical simulation (DNS), discrete element method (DEM) and computational fluid dynamics (CFD). In the macro-scale modelling approach, we will review the reduced-order modelling approach to evaluate the overall performance of the granulators. This approach typically requires empirical correlations and/or constitutive equations derived from detailed simulations.

In Summary, this lecture will provide an overview of different modelling and simulation approaches to investigate wet granulation processes in different level of detail and complexity with a trade-off between accuracy and computational cost.  

Massimo Poletto, Department of Industrial Engineering, University of Salerno

The relevance of particle mechanics concepts in SLS

Selective laser sintering (SLS) of powders is an additive manufacturing technique that allows to build three dimensional objects using a layer by layer addition and the laser sintering of selected portions of these layer powders.

The preparation of good quality powder layers requires appropriate powder properties at the process conditions. The strength of sintered material depends on the characteristics of the powder used and on the effectiveness of the sintering process.

The talk addresses the results of some dedicated work carried out on these issues, highlighting how basic concepts of powder mechanics can be useful in understanding some finding in dedicated experiments relevant to SLS.

Enrico Gallino, Ricoh

Challenges and opportunities for the characterization of polymer powders for the selective laser sintering process

As additive manufacturing (AM) technology transitions from the fabrication of prototypes to serial production of end-use parts, the understanding of the powder properties needed to reliably produce parts of acceptable quality becomes critical.

Achieving the optimal quality for parts does not only depend on setting the right process parameters. Material feedstock also plays an important role when aiming for high performance products.

In the case of selective laser sintering, polymer powders are used as a raw material. Therefore, controlling the quality and correctly characterising the particles used in the process is a key step to successfully apply polymer AM techniques and also to expand the range of material that can be process with this technology.

Barthelemy Harthong, 3SR, Univ. Grenoble Alpes

The multi-particles finite-element method

The multi-particles finite-element method is one of the three FEM/DEM coupling methods. A granular assembly is modelled as a collection of meshed particles, each of them being solved as a boundary value problem in which the boundary forces are particle/particle interaction forces.

As such, the method fully resolves the problem of particle deformation and is suitable for problems in which the particle deformation is large and no particle breakage occurs. The presentation will highlight the main features of the method and some results and applications.

Séverine Roméro, Vesuvius

Refractory materials

TBC

Pierre Jop, Saint Gobain

Industrial applications: Materials at high temperature in Saint-Gobain

Final products often require industrial processes able to transform heterogeneous materials into a homogeneous one. Glass industry is an example of millenary process, roughly speaking, that transforms sand into glass for windows. However, making high quality glass requires the understanding of the physical and chemical processes at the grains scale.

During this lecture, we will see how we can explore the behavior of grains, how we can understand the transformations, depending on the nature of the grains (raw materials or glass cullet). In a second time, we will analyze the transport properties inside a rotating kiln of granular materials, and the impact of the temperature.

Pascal Hagenmuller, Centre d’Etudes de la Neige, CNRM, Météo-France - CNRS

Microstructure-based modelling of snow mechanics

Characterising the mechanical properties of snow and its evolution is a major challenge for many applications such as avalanche forecasting. Snow is a hot material existing close to its melting point and a very porous material with a void ratio up to 20, which promotes very active metamorphism.

In consequence, there is not a unique snow material but numerous snow types distinguished by the shape, the size and the spatial arrangement of their ice particles. The mechanical properties of snow are tied to this microstructure. However, because of the wide range of microstructural patterns and the difficulty in conducting mechanical tests on this fragile and heterogeneous material, the relationship between microstructure and mechanical properties is still poorly understood.

To decipher this link, we built mechanical models based on the three-dimensional microstructure of snow obtained by x-ray micro-tomography. The main idea is to numerically reproduce mechanical experiments by considering snow simply as a porous structure of ice. The difficulty of this approach is the processing of the large amount of data obtained by tomography at high resolution (e.g. 10 μm).

For loadings involving small local deformations such as the elastic behavior, the strategy is to use a fine description of the structure but a simple constitutive law for ice and finite element models. For loadings involving complex structural rearrangements such as the penetration of an object (e.g. SMP), compression or structural collapse, the degrees of freedom of the structure are constrained to inter-granular deformations and discrete element models are considered.

This approach overcomes the difficulty of conducting real experiments on fragile snow types and enables to apply different and controlled loadings on the same sample. This presentation will give an overview of the different numerical methods and experiments developed at the Snow Research Center of Météo-France.

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