Search

Highlights • Combined PFEM-DEM-FEM mill model. • Efficient and robust fluid model of the pulp is included into the numerical model. • Numerical results are validated against experimental measurements. • Direct coupling between force, stress and deflection for the whole mill system. • Predict pressure in the pulp. Abstract Modelling of wet grinding in tumbling mills is an interesting challenge. A key factor is that the pulp fluid and its simultaneous interactions with both the charge and the mill structure have to be handled in a computationally efficient way. In this work, the pulp fluid is modelled with a Lagrange based method based on the particle finite element method (PFEM) that gives the opportunity to model free surface flow. This method gives robustness and stability to the fluid model and is efficient as it gives possibility to use larger time steps. The PFEM solver can be coupled to other solvers as in this case both the finite element method (FEM) solver for the mill structure and the DEM solver for the ball charge. The combined PFEM-DEM-FEM model presented here can predict charge motion and responses from the mill structure, as well as the pulp liquid flow and pressure. All cases presented here are numerically modelled and validated against experimentally measured driving torque signatures from an instrumented small-scale batch ball mill equipped with a torque meter and charge movements captured from high-speed video. Numerical results are in good agreement with experimental torque measurements and the PFEM solver also improves on efficiency and robustness for solving charge movements in wet tumbling mill systems. [ABSTRACT FROM AUTHOR]

In the powder metallurgy (PM) pressing process the mechanical properties of the green body are highly dependent on the material density. During the ejection stage of the pressing process the elastic behaviour is important especially for the crack formation in the powder compact. Experiments show a non-linear and also stress dependent elastic behaviour of green bodies. In this study diametral compression tests have been used to study elastic deformation during crack formation in a tensile fracture process of metal powder disc compacts. The powder material used for the experiments was a press-ready premix containing Distaloy AE, 0.5% graphite (uf-4) and 0.6% Kenolube. Tensile strength is used as a failure condition and limits the stress in the fracture interface. To control the tensile fracture, a cohesive zone model is used. The softening rate of the fracture model is obtained from the corresponding rate of the dissipated energy. The deformation of the powder material is modelled with an elastic–plastic cap model where an easy-to-use model for non-linearity in the elastic state due to stress is presented. The model is implemented in a finite element code and tested in simulation of a diametral compression testing. Results from simulations correlate well with experimental results and demonstrate the importance of including the non-linear elastic effect of the powder compacts. Results also show the necessity to accurate model the elasticity in the tooling to correct capture force–displacement response and fracturing processes. [ABSTRACT FROM AUTHOR]

Modelling the pulp fluid and its simultaneous interactions with both the charge and the mill structure is an interesting challenge. The interactions have previously been modelled for dry grinding with a combination of discrete element method (DEM), smoothed particle hydrodynamics (SPH) and the finite element method (FEM), where the DEM particles or SPH particles represent the grinding balls and FEM is used to model the mill structure. In this work, the previous model is extended to include fluids with SPH. Wet milling with water and a magnetite pulp, for graded and mono-size charges are numerically modelled and validated. The internal working of the charge and the physical interaction between the charge and the mill structure is studied. The combined SPH–DEM–FEM model presented here can predict the classical DEM results, but can also predict responses from the mill structure, as well as the pulp liquid flow and pressure. Validation is conducted by comparing numerical results with experimental measurements from grinding in an instrumented small-scale batch ball mill equipped with an accurate torque metre. The simulated charge movement is also compared with high speed video of the charge movement for a number of cases. Numerical results are in good agreement with experimental measurements. [ABSTRACT FROM AUTHOR]

Highlights: [•] Combined SPH–DEM–FEM mill model. [•] Pulp is included into the numerical model. [•] Direct coupling between force, stress and deflection for the whole mill system. [•] Predict pressure in the pulp. [Copyright &y& Elsevier]

This article discusses the fracture modelling accuracy of strain-driven ductile fracture models when introducing damage of high strength sheet steel. Numerical modelling of well-known fracture mechanical tests was conducted using a failure and damage model to control damage and fracture evolution. A thorough validation of the simulation results was conducted against results from laboratory testing. Such validations show that the damage and failure model is suited for modelling of material failure and fracture evolution of specimens without damage. However, pre-damaged specimens show less correlation as the damage and failure model over-predicts the displacement at crack initiation with an average of 28%. Consequently, the results in this article show the need for an extension of the damage and failure model that accounts for the fracture mechanisms at the crack tip. Such extension would aid in the improvement of fracture mechanical testing procedures and the modelling of high strength sheet metal manufacturing, as several sheet manufacturing processes are defined by material fracture. [ABSTRACT FROM AUTHOR]

For investigating high pressure sintering processes, numerical models can be used. This will demand material models which give realistic mechanical response throughout the whole parameter space of the actual process. As the pressures become higher, the material density approaches its full theoretical value and the elastic part of the material properties becomes increasingly important. In this investigation, Poisson's ratio was determined using ultrasonic pulse-echo measurements. A new elastic model and an improved plasticity model were implemented into a user-defined material subroutine in a finite element (FE) code. To experimentally investigate the load displacement response and pressure distribution in powder compacts during pressing, a pressure instrumented Bridgman anvil apparatus was used. Validation of the FE model was conducted against experimental data from pressing experiments using two different start densities. The results show that the simulation model is indeed capable of reproducing load–thickness curves and pressure profiles reasonable close to the experimental curves. [ABSTRACT FROM AUTHOR]

Abstract: The smoothed particle hydrodynamic (SPH) method is used to model a ball charge and its interaction with the mill structure, while the flexible rubber lifter and the lining are modelled with the finite element method (FEM). The adaptive nature of the SPH-method together with the non-connectivity between the particles results in a method that is able to handle very large deformations. This computational model makes it possible to predict the deflection and stresses of the lining in a pilot ball mill and the mechanical waves travelling in the mill system. It also makes it possible to predict e.g. charge pressure and von Mises’ stress within the charge and the contact forces between the charge and lining. The deflection profile of the lifters obtained from SPH–FEM simulation shows a reasonably good correspondence to pilot mill measurements as measured by an embedded strain gauge sensor. [Copyright &y& Elsevier]

Abstract: High Pressure High Temperature (HPHT) equipment is used for commercially produce synthetic diamond and other polycrystalline products. The common denominator for almost all high-pressure systems is to use capsules where a powder material encloses the core material. In this work, the properties of CaCO3 powder up to ultra-high pressure have been studied using an instrumented Bridgman anvil apparatus. Bismuth phase transformations were used as fix point calibrant. Three different parameters were studied, density, moisture and diametral support dependence on the load–thickness and pressure build-up. The experiments are done such as they can be used as validation and calibration of constitutive models for finite element simulations of the HPHT-process. The results show that increasing the density of the powder compact increases the load needed to reach maximum pressure. In addition, the residual stresses in the compact seem to delay the phase transition on the down-ramp. Moisture content within 0.5%–1.2% does not significantly influence the compaction properties of the discs. Diametral support increases the phase transition load. [Copyright &y& Elsevier]

Abstract: Computational demands and the lack of detailed experimental verification have limited the value of distinct element method (DEM) modelling approaches in mill simulation studies. This paper presents the results of a study in which the deflection of a lifter bar in a pilot ball mill is measured by an embedded strain gauge sensor and compared to deflections predicted from finite element (FE) simulations. The flexible rubber lifter and the lining in a tumbling mill are modelled with the finite element method (FEM) and the grinding medium is modelled with DEM. The deflection profile obtained from DEM–FE simulation shows a reasonably good correspondence to pilot mill measurements. To study the charge impact on the mill structure two different charges are used in the simulations. The approach is a contribution to the validation of DEM–FE simulations and an introduction to the description of a bendable rubber lifter implemented in a DEM–FEM mill model. It opens up the possibility to predict contact forces for varying mill dimensions and liner combinations. FEM is especially valuable in this case, since there are readily available libraries with material models. [Copyright &y& Elsevier]

Abstract: The mechanical properties of powders at high pressures are difficult to measure and therefore such data are rarely reported in open literature. Available test equipment mainly operates in the low-pressure region, 0–200MPa. Calcite (CaCO3) is a mineral suitable for high-pressure processes, e.g. sintering of diamond compacts. It is also a very common material in the earth core and therefore of interest for geoscientists. In order to model the processes in the high-pressure region (above 1GPa), knowledge of the mechanical properties of the powder in the entire pressure range is needed. Experimental studies have been conducted to investigate the pressure–density relationship of a CaCO3 powder and also to correlate the relative density to elastic and strength properties using experimental results. Further, a methodology has been introduced to provide a foundation for an elastic–plastic constitutive model. The mechanical behaviour of a CaCO3 powder mix has been investigated using the Brazilian disc test, uniaxial compression testing and closed die experiments. The experiments showed increasing elastic modulus and strength with increasing density. An empirical expression of the dependence of the bulk modulus on density has also been introduced. [ABSTRACT FROM AUTHOR]

Abstract: Die pressing of metal powder results in a green body. After release from the die, the green body must have enough strength to be handled, to endure transport to a sintering furnace and heating to the sintering temperature. Drilling, turning and milling, which are common operations in the green state, require a green body of high strength, with no defects and excellent mechanical properties. A plane strain finite element model is used to analyse pressing of metal powder into a rectangular bar. The powder behavior is described by a “cap” model, which is implemented as a user material subroutine in the non-linear finite element program LS-DYNA. To improve modelling of strength in the green state a new non-linear density dependent failure envelope has been used. The model is adjusted to the properties of a water atomised metal powder from Höganäs AB. To resolve the severe stress gradient at the side surface of the green body, the smallest element size was chosen to be 65 μm. The aim of this work is to numerically capture and understand the development of the residual axial stress in particular at the side surface. The influence of kinematics, friction, compacting pressure and die taper are studied. Results from the numerical study show that the thickness of the compressive stress region close to the side surface of the green body varies between 50 μm and 600 μm along the surface. Compacting pressure, “upper punch hold down” and die taper geometry all have a significant influence on the residual stress state while die wall friction has only a small influence. The numerical results are in agreement with results from X-ray and neutron diffraction measurements. [Copyright &y& Elsevier]

In this work, the essential work of fracture (EWF) method is introduced for a peridynamic (PD) material model to characterize fracture toughness of ductile materials. First, an analytical derivation for the path-independence of the PD J-integral is provided. Thereafter, the classical J-integral and PD J-integral are computed on a number of analytical crack problems, for subsequent investigation on how it performs under large scale yielding of thin sheets. To represent a highly nonlinear elastic behavior, a new adaptive bond stiffness calibration and a modified bond-damage model with gradual softening are proposed. The model is employed for two different materials: a lower-ductility bainitic-martensitic steel and a higher-ductility bainitic steel. Up to the start of the softening phase, the PD model recovers the experimentally obtained stress–strain response of both materials. Due to the high failure sensitivity on the presence of defects for the lower-ductility material, the PD model could not recover the experimentally obtained EWF values. For the higher-ductility bainitic material, the PD model was able to match very well the experimentally obtained EWF values. Moreover, the J-integral value obtained from the PD model, at the absolute maximum specimen load, matched the corresponding EWF value. [ABSTRACT FROM AUTHOR]

Abstract: The multi-particle finite element method (MPFEM) is used to simulate confined compression of iron ore pellets. The confined compression test consists of a cylindrical steel tube and two compressive platens. The iron ore pellets are confined by the tools and compressed. In the MPFEM model of the test, the iron ore pellets are represented by 1680 finite element (FE) discretised particles (7–16mm). The size, shape and material properties of the pellets are statistically distributed. The contacts are modelled using the penalty stiffness method and Coulomb friction. The compression is simulated in two steps. In the first step, the iron ore pellet models are sparsely placed in the computational model of the steel tube and a gravity-driven simulation is conducted to make the pellets arrange themselves randomly. In a second step, the compression is simulated by a prescribed motion of the upper compressive platen. From the MPFEM simulation, the stresses inside the individual pellet models are evaluated, and the fracture probability of the iron ore pellets is derived and compared with the experimental data. In addition, data on the global axial and radial stresses and axial displacement are presented and compared with the experimental confined compression test data. The MPFEM model can reproduce the fracture ratio of iron ore pellets in uniaxial confined compression and is a feasible method for virtual fracture experiments of iron ore pellets. [Copyright &y& Elsevier]

Abstract: Iron ore pellets are sintered, centimetre-sized spheres of ore with high iron content. Together with carbonized coal, iron ore pellets are used in the production of steel. In the transportation from the pelletizing plants to the customers, the iron ore pellets are exposed to different stresses, resulting in degradation of strength and in some cases fragmentation. For future reliable numerical simulations of the handling and transportation of iron ore pellets, knowledge about their mechanical properties is needed. This paper describes the experimental and numerical work to investigate the mechanical properties of blast furnace iron ore pellets. To study the load deformation behavior and the fracture of iron ore pellets, a number of point load tests are carried out and analyzed. Material parameters for an elastic–plastic constitutive model with linear hardening for iron ore pellets are derived and expressed in terms of statistical means and standard deviations. Two finite element models are developed for different purposes. For the material parameter determination, a perfectly spherical model is used. The constitutive model is validated with a finite element model based on a representative optically scanned iron ore pellet. The proposed constitutive model is capturing the force displacement relation for iron ore pellets in a two-point load test. A stress based fracture criterion which takes the triaxiality into account is suggested and calculated as the maximum equivalent effective stress dependent on the three principal stresses at fracture. The results of this study show that the equivalent effective stress in the vicinity of the centre of an irregular model of an iron ore pellet is very close to the results of a model of a perfectly spherical iron ore pellet. The proposed fracture criterion indicates fracture in the representative iron ore pellet model coincident with the location of the crack developed during the test of the optically scanned iron ore pellet. [Copyright &y& Elsevier]

Abstract: Numerical simulation of manufacturing processes with working conditions at high pressure (above 1GPa) requires constitutive data of the powder for the whole range of pressure and density. Most of the test apparatuses commonly used to obtain such data are only working in the lower pressure regions. Because of the absence of high-pressure data, many parameters have to be guessed or extrapolated. A material used in high-pressure applications is Calcite (CaCO3). The material can be used as an insulator in high-pressure capsules it is also a common material in the earth core. An apparatus often used to generate high pressure during compaction is the Bridgman anvil apparatus. In this work experimental tests with a Bridgman anvil set-up using Calcite powder discs with different thicknesses were done. A nonlinear elastic-plastic cap model was developed to model the behaviour of powder material from low pressure and loose state to high pressure and solid state. The constitutive model was implemented in a finite element code. The constitutive data were identified by optimization of experimental data. Validation was done by numerically reproduce the mechanical behaviour of uni-axially pressing Calcite to different pressure (up to 5GPa) including unloading. The load–displacement curves, density distribution and the surface displacement were measured and compared to the finite element results. The results of the compaction simulations agree reasonably well with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract The automotive industry's desire for weight reduction while maintaining crashworthiness demands development of materials and material properties within the economic framework of consumers. The industrial process of hot stamping provides a technique to utilize steel in an efficient way. In hot stamping, microstructural characteristics of a steel blank are influenced by controlling the cooling rate. Hot stamping has become a prevalent method for lightweight solutions in car bodies without sacrificing passenger safety. The process of hot stamping applies sequential forming and quenching in a single production step. During the cooling of the blank, various microstructures can be formed depending on the cooling rate or holding temperature. Special tooling allows the application of different cooling rates within the same blank. Thus, the microstructure and mechanical properties can be influenced in designated areas of a blank. Fracture toughness properties of sheet metal are necessary to better understand fracture initiation and crack propagation during crash loading as well as improve crashworthiness predictions. This paper focus on fracture toughness of low-alloyed boron steel sheet common in the automotive industry. A heat treatment process is used to form different microstructures, predominately consisting of one single phase or mixed microstructures with two distinct phases. The fracture toughness of the present microstructures is evaluated using the Essential Work of Fracture methodology. Results are discussed in terms of the different microstructures obtained and the consequent part performance. Results show a strong connection between microstructure and fracture toughness. The bainitic grade shows favorable fracture toughness while a mixed microstructure of bainite and martensite shows a very brittle fracture behavior. A post heat treatment in the form of paint bake curing shows a negligible effect on fracture toughness of martensite. [ABSTRACT FROM AUTHOR]

The automotive industry is striving for light body-in-white structures while maintaining or improving passenger safety. The aim of this paper is to investigate the influence of the loading rate on the fracture toughness of thin steel sheet metal of three advanced high strength steels. Although steel is a heavy material it plays a significant role for lightweight solutions in car bodies. Three different advanced high strength steel (AHSS) grades, namely dual-phase (DP), quench-partitioning (Q&P) and TRIP-assisted bainitic-ferritic (TBF), are investigated in the present paper. For crash relevant components it is of importance to know the material response under high loading velocities i.e. high strain rates. A standard tensile test system is used for low loading rates, a high-speed tensile testing setup is used to obtain high loading rates. The fracture toughness of the three AHSS grades is evaluated using the methodology of the Essential Work of Fracture (EWF). The tensile specimen used in the present work is the double edge notched tensile (DENT) geometry with a pre-developed crack. High-speed imaging is applied to verify the validity of the evaluation method Essential Work of Fracture at high rates of loading. Results from this work show that knowledge of fracture toughness would improve the understanding of fracture and crack propagation mechanisms for third generation high strength steels used for automotive components. [ABSTRACT FROM AUTHOR]

Materials in granular form are widely used in industry and in the society as a whole. Granular materials can have various behaviours and properties. An accurate prediction of their flow behaviour is important to avoid handling and transportation issues. In this study, the flow behaviour of dry potassium chloride (KCl) in granular form was investigated experimentally and simulated numerically. The aim was to develop numerical tools to predict the flow of KCl in transportation and handling systems and granular material flow in various industrial applications. Two experimental setups were used to quantify the flow of KCl. In the first setup, the collapse of an axisymmetric granular column was investigated. In the second setup, digital image correlation was used to obtain velocity field measurements of KCl during the discharge of a flat-bottomed silo. The two experiments were represented numerically using two-dimensional computational domains. The smoothed particle hydrodynamics method was used for the simulations, and a pressure-dependent, elastic-plastic constitutive model was used to describe the granular materials. The numerical results were compared to the experimental observations, and an adequate qualitative and quantitative agreement was found for the granular column collapse and the silo discharge. Overall, the simulated flow patterns showed adequate agreement with the experimental results obtained in this study and with the observations reported in the literature. The experimental measurements, in combination with the numerical simulations, presented in this study adds to the knowledge of granular material flow prediction. The results of this study highlights the potential of numerical simulation as a powerful tool to increase the knowledge of granular material handling operations. [ABSTRACT FROM AUTHOR]

Blast furnace iron ore pellets are sintered, centimetre-sized ore spheres with a high iron content. Together with carbonized coal, iron ore pellets are used in the production of steel. In transporting pellets from pelletizing plants to customers, iron ore pellets are exposed to different static and dynamic loading situations, resulting in strength degradation and, in some cases, fragmentation. This can lead to a reduced gas flow in the blast furnace, which causes reduced quality in steel production. Reliable numerical simulations that can predict the ability of the pellets to endure their handling are important tools for optimizing the design of equipment for iron ore handling. This paper describes the experimental and numerical work performed to investigate the impact fracture behaviour of iron ore pellets at different strain rates. A number of split Hopkinson pressure bar tests with different striker velocities are carried out and analysed to investigate the strain rate dependency of the fracture strength of iron ore pellets. Fracture data for iron ore pellets are derived and expressed in terms of statistical means and standard deviations. A stress based, strain-rate dependent fracture model that takes triaxiality into account is suggested. The fracture model is used and validated with impact tests of iron ore pellets. In the validation experiment, iron ore pellets are fired against a steel plate, and the percentage of fractured pellets at different impact velocities are measured. Finite element simulations of the experiment are carried out and the probability of pellets fracturing during impact are calculated and compared with the experimental results. The agreement between the experiments and numerical simulations shows the validity of the model. [ABSTRACT FROM AUTHOR]

Granular material flow occurs in many industrial applications, and the characteristics of such flow is challenging to measure. Therefore, an experimental method that captures the flow behavior at different loading situations is desired. In this work, experimental measurements of granular material flow with digital speckle photography (DSP) are carried out. The granular flow process is recorded with a high-speed camera; the image series are then analyzed using the DSP method. This approach enables field data such as displacement, velocity, and strain fields to be visualized during the granular material flow process. Three different scenarios were studied: free surface flow in a fill shoe, flow without a free surface in a fill shoe, and the rearrangement of material in a cavity. The results showed that it is possible to obtain field data of the motion of particles for all three scenarios with the DSP technique. The presented experimental methodology can be used to capture complex flow behavior of granular material. [ABSTRACT FROM AUTHOR]

The natural phenomena hydraulic jump that is commonly used in spillways as an energy dissipater coupled to hydropower applications has been investigated with Smoothed Particle Hydrodynamics. A new approach was applied based on a periodic open boundary condition. The model consisted of a tank, a gate, a stilling basin and periodic open boundaries at each end of the computational domain. The tank provided a hydraulic head and in turn a specific flow through the gate, and a downstream condition in terms of a depth for the jump. The gate elevation had a major impact and was calibrated to ensure a correct and stable flow rate, when compared to experiments. With the proper flow rate, the position of the jump toe was significantly improved. The jump toe oscillated with a frequency in good agreement with experimental findings found in the literature and the oscillation amplitude increased with Froude number. However, for high Froude number cases the position was still too close to the gate but could be improved by including a correction based on the length of the jump. The depths in both the super- and subcritical zones was in good agreement with experiments and previous numerical studies. Furthermore, the Froude number was in-line with the definition of super- and subcritical flows. [ABSTRACT FROM AUTHOR]

• The macro-response of MnFeSi-slag under quasi-static compression conditions is highly dependent on the structure and composition of the material. • The strength of MnFeSi-slag samples depends strongly on the inclusion density, distribution and level of attachment to the matrix. • The texture of MnFeSi-slag samples characterized by X-ray Computed Tomography together with mechanical tests suggests a strong relation between the phase-to-inclusion ratio and the brittleness of the material. • The evolution of the strain field captured by DIC shows a mechanical behavior of a composite-like material where random failure of the components caused high variability of the elastic parameters. Fragmentation processes like crushing and grinding are complex and extensively energy-consuming activities in the mining and mineral processing industry. By studying the processes and the typically brittle material involved in a virtual environment, i.e. numerical simulations, knowledge will be gained to support improvement of the efficiency and thereby meet established environmental goals. 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 MnSiFe-slag was performed. X-ray Computed Tomography was used for 3D imaging and quantitative characterization of the material texture, with focus on the shape, size and spatial distribution of inclusions. 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 re-arrangement during loading. Irreversible damage affects the structure of the material and it is perceived as non-linearities in the load–strain curves. It was found a degradation of the material under repetitive loading. A decrease of the elastic modulus exposes a weakening of the matrix and dominant behavior of the inclusions on the mechanical response of the material. [ABSTRACT FROM AUTHOR]

Lightweight components are in demand from the automotive industry, due to legislation regulating greenhouse gas emissions, e.g., CO2. Traditionally, lightweighting has been done by replacing mild steels with ultra-high strength steel. The development of micro-sandwich materials has received increasing attention due to their formability and potential for replacing steel sheets in automotive bodies. A fundamental requirement for micro-sandwich materials to gain significant market share within the automotive industry is the possibility to simulate manufacturing of components, e.g., cold forming. Thus, reliable methods for characterizing the mechanical properties of the micro-sandwich materials, and in particular their cores, are necessary. In the present work, a novel method for obtaining the out-of-plane properties of micro-sandwich cores is presented. In particular, the out-of-plane properties, i.e., transverse tension/compression and out-of-plane shear are characterized. Test tools are designed and developed for subjecting micro-sandwich specimens to the desired loading conditions and digital image correlation is used to qualitatively analyze displacement fields and fracture of the core. A variation of the response from the material tests is observed, analyzed using statistical methods, i.e., the Weibull distribution. It is found that the suggested method produces reliable and repeatable results, providing a better understanding of micro-sandwich materials. The results produced in the present work may be used as input data for constitutive models, but also for validation of numerical models. [ABSTRACT FROM AUTHOR]

Failure in industrial processes is often related to wear and can cause significant problems. It is estimated that approximately 1–4% of the gross national product for an industrialized nation is related to abrasive wear. This work aims to numerically predict development of wear for full-scale mining applications in harsh sub-arctic conditions. The purpose is to increase the understanding of wear development in industrial processes and optimize service life and minimize costs related to wear. In the present paper, a granular material model consisting of the discrete element method (DEM) and rigid finite element particles is utilized to study wear in full-scale mining applications where granular materials and steel structures are present. A wear model with the basis in Finnie's wear model is developed to calculate wear from combined abrasive sliding and impact wear. Novel in situ full-scale experiments are presented for calibration of the wear model. A simulation model of the rope shovel loading process is set up where the bucket filling process is simulated several times, and the wear is calculated with the calibrated wear model. From the full-scale validation, it is shown that the simulated wear is in excellent agreement when compared to the experiments, both regarding wear locations and magnitudes. After validation, the model is utilized to study if wear can be minimized by making small changes to the bucket. One major conclusion from the work is that the presented wear simulator is a suitable tool that can be used for product development and optimization of the loading process. [ABSTRACT FROM AUTHOR]

Modeling of wet stirred media mill processes is challenging since it requires the simultaneous modeling of the complex multiphysics in the interactions between grinding media, the moving internal agitator elements, and the grinding fluid. In the present study, a multiphysics model of an HIG5 pilot vertical stirred media mill with a nominal power of 7.5 kW is developed. The model is based on a particle-based coupled solver approach, where the grinding fluid is modeled with the particle finite element method (PFEM), the grinding media are modeled with the discrete element method (DEM), and the mill structure is modeled with the finite element method (FEM). The interactions between the different constituents are treated by loose (or weak) two-way couplings between the PFEM, DEM, and FEM models. Both water and a mineral slurry are used as grinding fluids, and they are modeled as Newtonian and non-Newtonian fluids, respectively. In the present work, a novel approach for transferring forces between grinding fluid and grinding media based on the Reynolds number is implemented. This force transfer is realized by specifying the drag coefficient as a function of the Reynolds number. The stirred media mill model is used to predict the mill power consumption, dynamics of both grinding fluid and grinding media, interparticle contacts of the grinding media, and the wear development on the mill structure. The numerical results obtained within the present study show good agreement with experimental measurements. [ABSTRACT FROM AUTHOR]

Machining of metals is an essential operation in the manufacturing industry. Chip formation in metal cutting is associated with large plastic strains, large deformations, high strain rates and high temperatures, mainly located in the primary and in the secondary shear zones. During the last decades, there has been significant progress in numerical methods and constitutive modeling for machining operations. In this work, the Particle Finite Element Method (PFEM) together with a dislocation density (DD) constitutive model are introduced to simulate the machining of Ti-6Al-4V. The work includes a study of two constitutive models for the titanium material, the physically based plasticity DD model and the phenomenology based Johnson–Cook model. Both constitutive models were implemented into an in-house PFEM software and setup to simulate deformation behaviour of titanium Ti6Al4V during an orthogonal cutting process. Validation show that numerical and experimental results are in agreement for different cutting speeds and feeds. The dislocation density model, although it needs more thorough calibration, shows an excellent match with the results. This paper shows that the combination of PFEM together with a dislocation density constitutive model is an excellent candidate for future numerical simulations of mechanical cutting. [ABSTRACT FROM AUTHOR]

• Two-way coupled particle finite element, discrete element and finite element models. • Modelling of interactions between slurry, grinding media and mill structure in a horizontal wet stirred media mill. • Slurry modelled as either Newtonian or non-Newtonian fluid. • Coupled models used to predict power draw, grinding media dynamics and contacts and agitator wear. Wet comminution is an important process in the mineral processing industry. Modelling of wet comminution in stirred media mills requires the simultaneous modelling of grinding media, a moving internal stirrer, and slurry. In the present study, a novel approach for modelling the physical interactions between slurry, grinding media and mill structure in a stirred media mill is presented. The slurry is modelled with the particle finite element method (PFEM). The grinding media is modelled using the discrete element method (DEM) and the mill structure is modelled using the finite element method (FEM). The interactions between slurry, grinding media and mill structure are modelled by two-way couplings between the PFEM, the DEM and the FEM models. The coupled model of the present study is used to predict the motion of slurry and grinding media, and to calculate the power draw during wet comminution in a pilot scale horizontal stirred media mill. Furthermore, the model is used to compare a Newtonian and a non-Newtonian model of the slurry, where the non-Newtonian model is used to capture experimentally observed shear-thinning. The coupled PFEM-DEM-FEM model preserves the robustness and efficiency of each of the methods and it gives the possibility to use large time increments for the fluid, greatly reducing the computational expense. The coupled model of the present work provide information on the complex dynamics of slurry and grinding media. The numerical model is shown to be a useful tool for increasing the knowledge and understanding of wet comminution in stirred media mills. [ABSTRACT FROM AUTHOR]