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Article
Publication date: 15 June 2015

Wei Zhou, Gang Ma, Xiao-Lin Chang and Yin Duan

The purpose of this paper is to discretely model rockfill materials considering the irregular shape of the particles and their crushability. The scientific goal was to investigate…

Abstract

Purpose

The purpose of this paper is to discretely model rockfill materials considering the irregular shape of the particles and their crushability. The scientific goal was to investigate the influence of particle crushability and shape on the mechanical behavior of rockfill materials.

Design/methodology/approach

The method of generating irregular-shaped particles was based on the observation that most rockfill grains can be approximately circumscribed by an ellipsoid. Two shape descriptors were used to make the virtual particles closely replicate the geometric features of natural rockfill grains. The combined finite-discrete element method (FDEM) was used to numerically simulate a drained, tri-axial compression test. The particle assemblies were subjected to tri-axial compression under strain controlled conditions while a constant confining pressure was maintained.

Findings

The non-breakable particles showed a remarkable ability to dilate as a result of a higher inter-particle locking effect. Dilation forces the particles to move from a lower potential energy state to a higher potential energy state, which causes the micro-structure to become less stable, resulting in a dramatic decline in the angle of friction from the peak state to the residual state. In addition, the elongated particles enhance the interlocking effect, but breakage is also more likely to occur. The net effect of those two mechanisms controls the overall shearing resistance of rockfill materials.

Originality/value

After calibration using a few micro-parameters, the combined FDEM was able to reproduce the typical behavior of rockfill materials without requiring a description of the complex relationship that exists between constituents; this relationship must be described in continuum mechanics. The simulation results showed that this approach is predictive. The combined FDEM also provides an opportunity for a quantitative study of the micro-structure of granular materials, and this study will help us to better understand the mechanical characteristics of rockfill materials.

Details

Engineering Computations, vol. 32 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 9 February 2010

Guangbin Dou, David C. Whalley, Changqing Liu and Y.C. Chan

Non‐planarity of assemblies and co‐planarity variation effects on anisotropic conductive adhesive (ACA) assemblies have been a concern for ACA users since the materials are first…

Abstract

Purpose

Non‐planarity of assemblies and co‐planarity variation effects on anisotropic conductive adhesive (ACA) assemblies have been a concern for ACA users since the materials are first devised. The primary objective of this paper is to introduce a new experimental method for studying co‐planarity variation effects on ACA assemblies.

Design/methodology/approach

The approach simulates non‐planarity through deliberate chip rotation during the ACA bonding process, thereby locking different levels of co‐planarity variation into ACA test assemblies. Scanning electron microscope (SEM) analysis and electrical joint resistance measurement using the four wire resistance (FWR) method are used to mechanically and electrically examine the connection quality of the ACA assemblies bonded with non‐planar joints, for which the chip and substrate patterns are specially designed to allow joint resistance measurement using the FWR method.

Findings

Typical experiments and their results are presented and analysed. The bond thickness differences between the SEM measurements and calculations indicate that the real rotations are smaller than those predicted by the calculations. The typical experimental results show that the joint resistance reduces as the deformation increases until reaching a relatively stable value after a certain deformation degree.

Research limitations/implications

The average joint resistances in the rotated samples are all bigger than those measured in the un‐rotated samples. This raises the question as to whether the joint resistances of ACA assemblies are more significantly affected by other affects of non‐planarity than just by its effect on bond thickness. However, before this can be confirmed, more research must be done to check if this behaviour happens for different bonding forces.

Originality/value

This paper reports a novel and simple experiment that can be used to examine the effects of co‐planarity variation on the electrical performance of ACA assemblies, by creating different bond thicknesses that are normally difficult to achieve by changing the bonding pressure, since ACA bond thicknesses are not linearly related to the bonding force. The merit of the technique is that there is no need to manufacture chip bumps and substrate pads with different geometries, or to control the bond pressure, to achieve bond thickness variation in ACA assemblies.

Details

Soldering & Surface Mount Technology, vol. 22 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 13 November 2018

Alireza Ahangar Asr, Asaad Faramarzi and Akbar A. Javadi

This paper aims to develop a unified framework for modelling triaxial deviator stress – axial strain and volumetric strain – axial strain behaviour of granular soils with the…

Abstract

Purpose

This paper aims to develop a unified framework for modelling triaxial deviator stress – axial strain and volumetric strain – axial strain behaviour of granular soils with the ability to predict the entire stress paths, incrementally, point by point, in deviator stress versus axial strain and volumetric strain versus axial strain spaces using an evolutionary-based technique based on a comprehensive set of data directly measured from triaxial tests without pre-processing. In total, 177 triaxial test results acquired from literature were used to develop and validate the models. Models aimed to not only be capable of capturing and generalising the complicated behaviour of soils but also explicitly remain consistent with expert knowledge available for such behaviour.

Design/methodology/approach

Evolutionary polynomial regression (EPR) was used to develop models to predict stress – axial strain and volumetric strain – axial strain behaviour of granular soils. EPR integrates numerical and symbolic regression to perform EPR. The strategy uses polynomial structures to take advantage of favourable mathematical properties. EPR is a two-stage technique for constructing symbolic models. It initially implements evolutionary search for exponents of polynomial expressions using a genetic algorithm (GA) engine to find the best form of function structure; second, it performs a least squares regression to find adjustable parameters, for each combination of inputs (terms in the polynomial structure).

Findings

EPR-based models were capable of generalising the training to predict the behaviour of granular soils under conditions that have not been previously seen by EPR in the training stage. It was shown that the proposed EPR models outperformed ANN and provided closer predictions to the experimental data cases. The entire stress paths for the shearing behaviour of granular soils using developed model predictions were created with very good accuracy despite error accumulation. Parametric study results revealed the consistency of developed model predictions, considering roles of various contributing parameters, with physical and engineering understandings of the shearing behaviour of granular soils.

Originality/value

In this paper, an evolutionary-based data-mining method was implemented to develop a novel unified framework to model the complicated stress-strain behaviour of saturated granular soils. The proposed methodology overcomes the drawbacks of artificial neural network-based models with black box nature by developing accurate, explicit, structured and user-friendly polynomial models and enabling the expert user to obtain a clear understanding of the system.

Details

Engineering Computations, vol. 35 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 24 January 2019

Min Wang, Y.T. Feng, Ting T. Zhao and Yong Wang

Sand production is a challenging issue during hydrocarbon production in the oil and gas industry. This paper aims to investigate one sand production process, i.e. transient sand…

Abstract

Purpose

Sand production is a challenging issue during hydrocarbon production in the oil and gas industry. This paper aims to investigate one sand production process, i.e. transient sand production, using a novel bonded particle lattice Boltzmann method. This mesoscopic technique provides a unique insight into complicated sand erosion process during oil exploitation.

Design/methodology/approach

The mesoscopic fluid-particle coupling is directly approached by the immersed moving boundary method in the framework of lattice Boltzmann method. Bonded particle method is used for resolving the deformation of solid. The onset of grain erosion of rocks, which are modelled by a bonded particle model, is realised by breaking the bonds simulating cementation when the tension or tangential force exceeds critical values.

Findings

It is proved that the complex fluid–solid interaction occurring at the pore/grain level can be well captured by the immersed moving boundary scheme in the framework of the lattice Boltzmann method. It is found that when the drawdown happens at the wellbore cavity, the tensile failure area appears at the edge of the cavity. Then, the tensile failure area gradually propagates inward, and the solid particles at the tensile failure area become fluidised because of large drag forces. Subsequently, some eroded particles are washed out. This numerical investigation is demonstrated through comparison with the experimental results. In addition, through breaking the cementation, which is simulated by bond models, between bonded particles, the transient particle erosion process is successfully captured.

Originality/value

A novel bonded particle lattice Boltzmann method is used to investigate the sand production problem at the grain level. It is proved that the complex fluid–solid interaction occurring at the pore/grain level can be well captured by the immersed moving boundary scheme in the framework of the lattice Boltzmann method. Through breaking the cementation, which is simulated by bond models, between bonded particles, the transient particle erosion process is successfully captured.

Details

Engineering Computations, vol. 36 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 30 September 2014

Xiao-Bo Wang, Wen-Jie Xu, Bing-Yin Zhang and Qi-Cheng Sun

Rock-fill dams are embankments of compacted free-draining granular earth containing an impervious zone. Earth utilized in such dams often contains a high percentage of large…

Abstract

Purpose

Rock-fill dams are embankments of compacted free-draining granular earth containing an impervious zone. Earth utilized in such dams often contains a high percentage of large particles – hence the term rock-fill. Mass stability of these dams results from friction and particle interactions rather than through a cementing agent binding the particles together. However, high-stress conditions and prolonged exposure to the elements can severely damage rock-fill. Therefore, understanding and modeling rock-fill breakage is important for dam engineering. The purpose of this paper is to improve discontinuous deformation analysis (DDA) techniques for modeling rock-fill breakage, proving the new method using simulations of spherical particle crushing.

Design/methodology/approach

This work models rock-fill as bonded ellipsoid particles, and develops an improved DDA method to model the breakage of particle assemblies. The paper starts by describing the principles of three-dimensional DDA for spherical particles, and then derives the submatrices for normal contact, shear contact, and frictional force. The new algorithm incorporates a bond model with a revised open-close iteration algorithm into the DDA method to simulate particle crushing. To validate the improved DDA method, calculated particle contacts and movements are validated against theoretical results. Finally, this work performs a series of point-loading experimental tests for cement ellipsoid particles of both high and low compression strengths, with the test results compared against the results from corresponding DDA simulations.

Findings

In particle crushing tests, the force and displacement show an approximately linear relationship until the crushing point, at which point low compression ellipsoid particles split into several large pieces while the high-compression particles break into many small fragments. The DDA simulation results are in good agreement with the crushing tests, demonstrating the validity of the DDA method for solving particle crushing problems. Although the improved DDA model is applicable to rock-fill particle crushing studies, some issues remain, particularly in increasing calculation efficiency and performing large-scale computations and long real-time simulations. Future research should address these issues.

Originality/value

A bond model with a revised open-close iteration algorithm is incorporated into the DDA method. The simulated results shed insight into rock-fill crushing mechanisms, an element of concern in engineering practices.

Details

Engineering Computations, vol. 31 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 27 July 2018

Junxia Li and Shaowei Liang

The study of the friction law and wear characteristics of the middle trough material can better select the appropriate material for the scraper conveyor of fully mechanized…

Abstract

Purpose

The study of the friction law and wear characteristics of the middle trough material can better select the appropriate material for the scraper conveyor of fully mechanized working face and provide theoretical support for the wear-resistant treatment technology.

Design/methodology/approach

This paper investigated friction and wear of the middle trough in a scraper conveyor under different media. Lignite, coking coal and anthracite were selected media, and middle trough wear was maximum for anthracite and minimum for lignite, with coking coal being intermediate.

Findings

Wear increased linearly with increasing load nonlinearly with increasing sliding speed. Middle trough wear also increased with increasing media granularity up to approximately 0.4 mm (40 mesh), but had little effect beyond that.

Originality/value

It can provide a reference for the scraper conveyor running resistance. At the same time, it has great social significance and economic benefits for the safe, green and efficient coal mine industrial adjustment, etc.

Details

Industrial Lubrication and Tribology, vol. 70 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Open Access
Article
Publication date: 23 May 2022

Yangsheng Ye, Degou Cai, Lin Geng, Hongye Yan, Junkai Yao and Feng Chen

This study aims to propose a semiempirical and semitheoretical cyclic compaction constitutive model of coarse-grained soil filler for the high-speed railway (HSR) subgrade under…

Abstract

Purpose

This study aims to propose a semiempirical and semitheoretical cyclic compaction constitutive model of coarse-grained soil filler for the high-speed railway (HSR) subgrade under cyclic load.

Design/methodology/approach

According to the basic framework of critical state soil mechanics and in view of the characteristics of the coarse-grained soil filler for the HSR subgrade to bear the train vibration load repeatedly for a long time, the hyperbolic empirical relationship between particle breakage and plastic work was derived. Considering the influence of cyclic vibration time and stress ratio, the particle breakage correction function of coarse-grained soil filler for the HSR subgrade under cyclic load was proposed. According to the classical theory of plastic mechanics, the shearing dilatation equation of the coarse-grained soil filler for the HSR subgrade considering particle breakage was modified and obtained. A semiempirical and semitheoretical cyclic compaction constitutive model of coarse-grained soil filler for the HSR subgrade under cyclic load was further established. The backward Euler method was used to discretize the constitutive equation, build a numerical algorithm of “elastic prediction and plastic modification” and make a secondary development of the program to solve the cyclic compaction model.

Findings

Through the comparison with the result of laboratory triaxial test under the cyclic loading of coarse-grained soil filler for the HSR subgrade, the accuracy and applicability of the cyclic compaction model were verified. Results show that the model can accurately predict the cumulative deformation characteristics of coarse-grained soil filler for the HSR subgrade under the train vibration loading repeatedly for a long time. It considers the effects of particle breakage and stress ratio, which can be used to calculate and analyze the stress and deformation evolution law of the subgrade structure for HSR.

Originality/value

The research can provide a simple and practical method for calculating deformation of railway under cyclic loading.

Article
Publication date: 23 November 2010

G.Q. Wu and Z.K. Zhang

The purpose of this paper is to present an update and the latest results from work on a project aimed at enabling waste printed circuit board (WPCB) recycling to become more…

Abstract

Purpose

The purpose of this paper is to present an update and the latest results from work on a project aimed at enabling waste printed circuit board (WPCB) recycling to become more environmentally friendly and efficient.

Design/methodology/approach

A new system was proposed and studied individually under laboratory and factory conditions, which consisted of lossless component removal, component classification, waste crushing/separating processes, and application of crushed non‐metallic particles to develop resin composites.

Findings

The use of these novel processes, including component lossless removal, component classification, waste crushing/separating processes, and application of crushed non‐metallic particles to develop resin composites can be combined to give a more sustainable treatment process for printed circuit boards recycling.

Research limitations/implications

Most parts of the WPCBs recycling system have been used. Further development work should be undertaken to establish the whole system in a factory‐scale environment in order to enhance the system efficiency.

Originality/value

The paper details how individual treatment technologies can be combined to enable a more environmentally friendly and efficient system for treatment of WPCBs which offers the benefits of reducing pollution and complete resource recovery for WPCBs.

Details

Circuit World, vol. 36 no. 4
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 21 August 2009

Paul W. Cleary

The purpose of this paper is to show how particle scale simulation of industrial particle flows using DEM (discrete element method) offers the opportunity for better understanding…

2844

Abstract

Purpose

The purpose of this paper is to show how particle scale simulation of industrial particle flows using DEM (discrete element method) offers the opportunity for better understanding of the flow dynamics leading to improvements in equipment design and operation.

Design/methodology/approach

The paper explores the breadth of industrial applications that are now possible with a series of case studies.

Findings

The paper finds that the inclusion of cohesion, coupling to other physics such fluids, and its use in bubbly and reacting flows are becoming increasingly viable. Challenges remain in developing models that balance the depth of the physics with the computational expense that is affordable and in the development of measurement and characterization processes to provide this expanding array of input data required. Steadily increasing computer power has seen model sizes grow from thousands of particles to many millions over the last decade, which steadily increases the range of applications that can be modelled and the complexity of the physics that can be well represented.

Originality/value

The paper shows how better understanding of the flow dynamics leading to improvements in equipment design and operation can potentially lead to large increases in equipment and process efficiency, throughput and/or product quality. Industrial applications can be characterised as large, involving complex particulate behaviour in typically complex geometries. The critical importance of particle shape on the behaviour of granular systems is demonstrated. Shape needs to be adequately represented in order to obtain quantitative predictive accuracy for these systems.

Details

Engineering Computations, vol. 26 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 July 1973

P. Kresse

Because of rationalisation and demands for improved quality, the surface coatings industry makes ever‐increasing demands for micronised pigments. Micronised pigments permit…

Abstract

Because of rationalisation and demands for improved quality, the surface coatings industry makes ever‐increasing demands for micronised pigments. Micronised pigments permit quicker dispersion and increased output, coincident with decreased production costs. Such factors as the superior dispersibility of micronised pigments have frequently been mentioned, and it is not easy to quote new aspects of this. Therefore, this article will primarily cover other technical advantages of micronised iron oxide pigments‐advantages hitherto neglected in favour of the main advantage, better dispersibility.

Details

Pigment & Resin Technology, vol. 2 no. 7
Type: Research Article
ISSN: 0369-9420

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