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Mechanical Characterization of Highly Heterogeneous Brittle Materials by Optical Techniques
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.ORCID iD: 0000-0002-4099-253x
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.ORCID iD: 0000-0001-5218-396X
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0001-7395-3302
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Solid Mechanics.ORCID iD: 0000-0003-0910-7990
2022 (English)In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 185, article id 107704Article in journal (Refereed) Published
Abstract [en]

Fragmentation processes like crushing and grinding are complex and extensively energy-consuming activities in the mining and mineral processing industry. Numerical analysis of different materials and loading conditions will gain more knowledge and support in the improvement of the efficiency of the fragmentation process. Although, a challenge is the lack of experimental data both for calibration and validation hampering the development of constitutive models. As a case of study, a mechanical characterization of pre-processed MnSiFe-slags was performed. Diametral and axial compressive tests under quasi-static conditions were used to load the mineral material and obtain a strain  field (ε) during increasing and cyclic loading until failure accounting for progressive damage. The evolution of the strain captured by digital image correlation (DIC) techniques exposed a mechanical behavior of composite-like material where random failure of the components caused high variability of the elastic parameters. These were found to be load dependent and they are strongly related to the ability of the material to internal rearrangement during loading. Irreversible damage affects the structure of the material and is perceived as non-linearities in the load-strain curves. It was found a degradation of the material under repetitive loading decreasing of the elastic modulus perceived as a weakening of the matrix and dominant behavior of the inclusions on the mechanical response of the material.

Place, publisher, year, edition, pages
Elsevier, 2022. Vol. 185, article id 107704
Keywords [en]
Heterogeneous materials, Slag, Brazilian disc, Cyclic loading, Digital Image Correlation
National Category
Other Mechanical Engineering
Research subject
Solid Mechanics; Experimental Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-87274DOI: 10.1016/j.mineng.2022.107704ISI: 000823233000001Scopus ID: 2-s2.0-85132694063OAI: oai:DiVA.org:ltu-87274DiVA, id: diva2:1598518
Funder
EU, Horizon 2020, ”GREENY” 18009
Note

Validerad;2022;Nivå 2;2022-06-30 (sofila)

Available from: 2021-09-29 Created: 2021-09-29 Last updated: 2024-12-01Bibliographically approved
In thesis
1. Mechanical Characterization of Heterogeneous Brittle Materials
Open this publication in new window or tab >>Mechanical Characterization of Heterogeneous Brittle Materials
2021 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Comminution is one of the highest energy-consuming processes in the mining and mineral processing industry by consuming around 2% of the global generated energy with an overall efficiency of 1-3%. Different approaches to the optimization of processes have been developed, but there is still room for improvement. The macro events where energy is mostly spent require numerical methods, so an overall optimization of the system is performed by the analysis and optimization of individual subsystems, such as machines and material to be crushed. The challenge when applying numerical analysis lies on the calibration of the models with mechanical parameters inherent to the constitutive laws and physics of the system. It has been seen that mineral material is exposed to a great variety of time dependent forces within the process. A baseline to understanding the interaction of the material with the machines is the analysis of fracture processes under different loading conditions. This thesis focuses on the mechanical characterization of manganese slag core material for the development, calibration and validationof constitutive models via direct and indirect measurements of the strength and fracture behavior. Diametrial and axial compressive tests under quasi-static and dynamic conditions were used by the hand of optical techniques to obtain information about the evolution of damage. Digital image correlation in 2D and 3D was implemented, considering that it is a method virtually independent ofthe geometry, size, material and deformation rate. Quasi-static tests on both Brazilian disc and unconfined axial compression configurations exposed a mechanical behavior of composite-like material where random failure of the components caused high variability of the elastic parameters. Irreversible damage was perceived globally as non-linearities in load-strain curves, while cyclic loading revealed a degradation of the material affecting the elastic modulus where a weakening of the matrix and dominant behavior of the inclusions on the mechanical response is perceived. Dynamic tests were performed in an in-house built Split Hopkinson Pressure Bar which follows the wave propagation theory in the material generated by the impact of a pressure driven projectile. 2D high speed imaging was performed in order to obtain informationabout the crack initiation and fracture process so that a sampling frequency of 380,000 fps and 663,200 fps was obtained for axially and diametrically loaded samples, respectively. Full-field deformations showed a staggered fracture process were on set failure points vary due to the internal events happening in the material. Localized frictional occurrences and inertial effects acting in the pre-cracked matrix have a strong effect on the global mechanical response and, therefore, a great variability of ultimate compressive and tensile strengths was found. The overall strain/loading rate dependency of the material was perceived as a general increase of the UCT and maximum load compared to quasi-static values. In general, the objective of this work was to study the effect of different loading conditions on the mechanical behavior and material parameters of unprocessed slag for the future development of numerical models of large-scale comminution processes.

Place, publisher, year, edition, pages
Luleå University of Technology, 2021
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-87275 (URN)978-91-7790-936-1 (ISBN)978-91-7790-937-8 (ISBN)
Presentation
2021-11-26, E632, Luleå tekniska universitet, 97187, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2021-09-29 Created: 2021-09-29 Last updated: 2023-09-05Bibliographically approved
2. Mechanical Characterization and Modeling of Heterogeneous Brittle Materials in Comminution Processes
Open this publication in new window or tab >>Mechanical Characterization and Modeling of Heterogeneous Brittle Materials in Comminution Processes
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The steel industry has been an asset in society’s development; therefore, the worldwide production of crude steel has shown a growing trend. Following the sustainability principles reflected by the World Steel Association, incorporating pyrometallurgical by-products into a circular economy framework is of great interest to maximize the efficient use of resources throughout the life cycle of steel products and to help reduce CO2 emissions. Thus, research to optimize the supply chain of raw materials has increased, and there is a need to address the energy consumption of the highly demanding mechanical processes related to it, such as crushing.  

This PhD research focuses on the development of a framework that facilitates the optimization of comminution processes for secondary raw materials and enhances the value of material data for modeling breakage processes in the upscaling and evaluation of crushing at an industrial scale.  This investigation was divided into two primary components. First, an experimental framework was developed and implemented to characterize the tensile and compressive responses of electric arc furnace (EAF) manganese slag under both quasi-static and dynamic conditions. In the first study, manganese slag, a highly heterogeneous material, was examined, providing insights into the methodologies and challenges associated with sample manufacturing, quasi-static testing using simple loading schemes, and processing of mechanical and optical data. In the second study, the macro-response of slag under dynamic conditions was investigated, providing pertinent information regarding processing and crushing in relation to rate-dependent behavior, as well as energy expenditure during the fragmentation processes. The second part of this research focused on evaluating a numerical framework to upscale the fracture processes in crushing applications. Simulations of the fracture process of quasi-brittle materials employing finite element methods (FEM) were implemented and evaluated for mineral and secondary raw materials, enhancing the knowledge regarding the calibration of material models to simulate complex geometries with a high level of detail in the crack patterns and the accuracy of the failure loads. Finally, a fourth research article demonstrated the viability of employing an established material model to simulate slag from a macroscopic perspective. 

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2025. p. 45
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Slag, SHPB, Brazilian disc, Fracture, Crushing, Heterogeneous
National Category
Engineering and Technology
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-110913 (URN)978-91-8048-708-5 (ISBN)978-91-8048-709-2 (ISBN)
Public defence
2025-02-19, E632, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2024-12-02 Created: 2024-12-01 Last updated: 2025-01-29Bibliographically approved

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Suarez, LauraKajberg, JörgenForsberg, FredrikJonsén, Pär

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