Breaking Ground with the new Tavares Breakage Model

In this post I’m pleased to introduce the latest in particle breakage simulation technology – the new Tavares Breakage model. This model combines computationally efficient methods for calculating the energy of the system and applies an innovative particle replacement approach to deliver accurate breakage results based on stochastic, rather than deterministic, methods. A wide range of materials as well as their fine distributions can be modelled now!

BACKGROUND

Particle damage and subsequent size reduction is characteristic across a wide range of applications, such as comminution, transportation, materials handling, separation and geotechnical applications. This makes the breakage of materials a hot topic these days with a lot of interest and research around the best methods and models to simulate and predict this complex process.

Mill_mineral_processing

EDEM (now part of Altair) has been very active over the years on that front and developed a model that was able to describe such phenomena for certain loading conditions. The ultimate goal is to provide a breakage model that will be able to accurately capture the complex breakage mechanisms and provide the fragment size distribution including the fines.

THE TAVARES BREAKAGE MODEL

After months of intensive development, we are pleased to announce the availability of a new model called ‘Tavares Breakage Model’. This model is based on previous well-established research at the Federal University of Rio de Janeiro (L.M.Tavares et al 2002, 2009, 2012, 2013) and is the result of close collaboration between Prof. L.M.Tavares, Prof. J.Ooi and the EDEM R&D Team. It describes the breakage of brittle materials but most importantly uses an innovative approach for particle replacement that captures accurately the kinematics of the fragments, eliminates mass loss, while keeping a high degree of fidelity in describing the material response.

Calculation_cycle

Calculation cycle of Particle Weakening and particle replacement due to body breakage

There have been many mathematical models that fail to provide realistic results either because of their empirical nature, large number of fitting parameters, great complexity or, most importantly, poor accuracy and excessive computational cost. The new Tavares Breakage Model minimizes the use of empirical fitting parameters, uses contact detection for spheres to achieve computational efficiency and uses a state-of-the-art method to replace the particles with fragments of various sizes. Also, it employs a new stochastic approach that allows representing fragment size distribution with great fidelity, contrasting with previous studies that also used spherical particle replacement but that were deterministic in nature.

Over the years there have been different numerical approaches that describe the breakage of materials, but the only viable option that considers the flow of material due to breakage is the Discrete Element Method (DEM). DEM can capture the different modes of particle fracture, hence this method has proven to be a great predictive tool both for milling, crushing and other applications where particles are subject to complex series of loading events.

EDEM software is used by many customers in the mining and mineral processing industries with a need for modelling a number of unit operations. This need has been the driving force for the EDEM team to include a model that will be able to capture both catastrophic breakage (when particles suffer a significant impact) as well as weakening due to repeated stressing. Finally, the new Tavares breakage model delivers the final size distribution of the material including the fines, giving predicted size distributions that extend below the minimum particle size used in the DEM simulation. The implementation of the model has been verified on the basis of the continuum model from L.M. Tavares and A.S. das Chagas (2020) and validated based on single-particle tests and unconfined particle-bed experiments. The results of the latter are being prepared for publication in peer-reviewed journals.

OUTPUTS OF THE MODEL IN EDEM

The Tavares breakage model provides a list of outputs related to particle breakage due to impact, weakening of particles due to impacts not resulting in breakage and their related energies during weakening, as well as the body breakage and the final size distribution of the fragments.

The breakage model is currently available as an API that can be downloaded from the EDEM User Forum. It includes the .dll file, used as an input in the physics section in EDEM, as well as the preference file with the parameters of the breakable materials and the FracturePatternDistributions folder. For guidelines on how to setup an example simulation and tips regarding the parameters please refer to the Setup_guidelines document.

The outputs of the breakage model are the following:

  • New fracture energy per particle type
  • Fragment size distribution

Professor Tavares of the Federal University of Rio de Janeiro commented:

 “The model was the result of over a quarter of a century of testing single particles and applying the resulting equations proposed to a number of operations that include different types of mills and crushers, as well as degradation of materials during handling. Its implementation in EDEM was the result of a very successful collaborative effort, and the outcome is a model that allows very realistic predictions, without the high computational cost.

Professor Ooi of the University of Edinburgh added:

 “I am very pleased to have this opportunity to work with Prof. Tavares and the Altair EDEM R&D colleagues to develop this much improved predictive model for milling processes.  The model has successfully coupled the strength of EDEM in simulating the particle dynamics during milling with the fracture energies and the fragment size distributions based on robust experimental observations.

This project demonstrates how successful it is when industry and academia work together towards a common vision and goal. We are very pleased that we had the opportunity to work in such an efficient way with the biggest experts in the field of Materials Engineering and Solids Mechanics. We look forward to further collaboration and to continue to advance research in this field!

 

References

Tavares L.M. and King R.P. (2002) Modeling of particle fracture by repeated impacts using continuum damage mechanics. Powder Technology  123(2): p. 138-146.

Tavares L.M. (2009) Analysis of particle fracture by repeated stressing as damage accumulation. Powder Technology  190(3): p. 327-339.

Tavares L.M. and de Carvalho R.M. (2012) Modeling ore degradation during handling using continuum damage mechanics. International Journal of Mineral Processing  112-113: p. 1-6.

de Carvalho R.M. and Tavares L.M. (2013) Predicting the effect of operating and design variables on breakage rates using the mechanistic ball mill model. Minerals Engineering  43-44: p. 91-101.

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