J. Langus, P. Šuštarič and T. Rodič
The purpose of this paper is to evaluate the effect that polymer coat has on the impact behavior of grinding sphere and to find possible subsection of parameter space in which…
Abstract
Purpose
The purpose of this paper is to evaluate the effect that polymer coat has on the impact behavior of grinding sphere and to find possible subsection of parameter space in which grinding sphere wear could be reduced.
Design/methodology/approach
Numerical analysis is based on axisymmetric finite elements that were developed using symbolic tool AceGen. Comparing stress response of elastic and visco‐elastic material revealed that for high strain rates observed in impacts both behave the same and that is why elastic elements were used in simulations.
Findings
Impact velocity, coat thickness and polymer material properties were varied in a parametric case study of polymer‐coated sphere impact. Decrease of the pressure on the surface of grinding sphere indicates that polymer layer can be effective in reducing grinding media wear, but in order to maintain adequate impact pressure to do the grinding the impact velocity has to be increased. Both upper and lower limit for impact velocity were determined for some arbitrary pressure threshold values. This shows that combining measured threshold values of specific material with results from presented numerical tool could provide valuable guides for finding optimum stirred media milling operation parameters.
Originality/value
In this work, the authors develop numerical tools with the aim of supporting experimental development of polymer coat capable of reducing grinding media wear.
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Ashwani Assam, Nikhil Kalkote, Nishanth Dongari and Vinayak Eswaran
Accurate prediction of temperature and heat is crucial for the design of various nano/micro devices in engineering. Recently, investigation has been carried out for calculating…
Abstract
Purpose
Accurate prediction of temperature and heat is crucial for the design of various nano/micro devices in engineering. Recently, investigation has been carried out for calculating the heat flux of gas flow using the concept of sliding friction because of the slip velocity at the surface. The purpose of this study is to exetend the concept of sliding friction for various types of nano/micro flows.
Design/methodology/approach
A new type of Smoluchowski temperature jump considering the viscous heat generation (sliding friction) has recently been proposed (Le and Vu, 2016b) as an alternative jump condition for the prediction of the surface gas temperature at solid interfaces for high-speed non-equilibrium gas flows. This paper investigated the proposed jump condition for the nano/microflows which has not been done earlier using four cases: 90° bend microchannel pressure-driven flow, nanochannel backward facing step with a pressure-driven flow, nanoscale flat plate and NACA 0012 micro-airfoil. The results are compared with the available direct simulation Monte Carlo results. Also, this paper has demonstrated low-speed preconditioned density-based algorithm for the rarefied gas flows. The algorithm captured even very low Mach numbers of 2.12 × 10−5.
Findings
Based on this study, this paper concludes that the effect of inclusion of sliding friction in improving the thermodynamic prediction is case-dependent. It is shown that its performance depends not only on the slip velocity at the surface but also on the mean free path of the gas molecule and the shear stress at the surface. A pressure jump condition was used along with the new temperature jump condition and it has been found to often improve the prediction of surface flow properties significantly.
Originality/value
This paper extends the concept of using sliding friction at the wall for micro/nano flows. The pressure jump condition was used which has been generally ignored by researchers and has been found to often improve the prediction of surface flow properties. Different flow properties have been studied at the wall apart from only temperature and heat flux, which was not done earlier.
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Adnan Ibrahimbegović, Igor Grešovnik, Damijan Markovič, Sergiy Melnyk and Tomaž Rodič
Proposes a methodology for dealing with the problem of designing a material microstructure the best suitable for a given goal.
Abstract
Purpose
Proposes a methodology for dealing with the problem of designing a material microstructure the best suitable for a given goal.
Design/methodology/approach
The chosen model problem for the design is a two‐phase material, with one phase related to plasticity and another to damage. The design problem is set in terms of shape optimization of the interface between two phases. The solution procedure proposed herein is compatible with the multi‐scale interpretation of the inelastic mechanisms characterizing the chosen two‐phase material and it is thus capable of providing the optimal form of the material microstructure. The original approach based upon a simultaneous/sequential solution procedure for the coupled mechanics‐optimization problem is proposed.
Findings
Several numerical examples show a very satisfying performance of the proposed methodology. The latter can easily be adapted to other choices of design variables.
Originality/value
Confirms that one can thus achieve the optimal design of the nonlinear behavior of a given two‐phase material with respect to the goal specified by a cost function, by computing the optimal form of the shape interface between the phases.
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Tomaž Rodič, Domen Cukjati and Igor Grešovnik
To present numerical techniques and results of finite element based optimisation of material forming process for production of shaped food and beverage cans.
Abstract
Purpose
To present numerical techniques and results of finite element based optimisation of material forming process for production of shaped food and beverage cans.
Design/methodology/approach
The objectives were achieved by combining finite element system ELFEN with optimisation shell INVERSE. These computer systems were applied to optimisation of preform design, optimisation of tribological conditions between can body and individual segments of the tooling system as well as to optimisation of kinematics of the tooling segments.
Findings
Numerical analyses show that preform design offers the highest optimisation potential. For preform shape optimisation a very efficient algorithm has been developed which enables effective minimisation of the objective function.
Originality/value
The paper identifies three main technological possibilities to optimise production process for shaped cans and quantifies the effects of each option. It also identifies the most efficient optimisation techniques to improve the investigated process.
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T. Rodič and I. Grešovnik
A system for solving a wide variety of inverse and optimization problems in solid mechanics is introduced. The system consists of a general purpose finite element method (FEM…
Abstract
A system for solving a wide variety of inverse and optimization problems in solid mechanics is introduced. The system consists of a general purpose finite element method (FEM) analysis system “Elfen” and a shell which controls this system. The shell functions as a stand‐alone programme, so the system is physically divided into two separated parts. The “optimization part”, which corresponds to the shell, possesses optimization and inverse problem solution algorithms. The “analysis part”, which corresponds to an FEM system, serves for the definition of the objective function to which these algorithms are applied. The shell has a user interface implemented in the form of file interpreter which imposes a great flexibility at the definition of various optimization and inverse problems, including parameter identification in constitutive modelling, frictional contact problems and heat transfer. Concepts of the shell are discussed in detail.
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Luca G. Campana, Paolo Di Barba, Fabrizio Dughiero, Michele Forzan, Maria Evelina Mognaschi, Rudy Rizzo and Elisabetta Sieni
In electrochemotherapy, flexible electrodes, composed by an array of needles, are applied to human tissues to treat large surface tumors. The positioning of the needles in the…
Abstract
Purpose
In electrochemotherapy, flexible electrodes, composed by an array of needles, are applied to human tissues to treat large surface tumors. The positioning of the needles in the tissue depends on the surface curvature. The parallel needle case is preferred, as their relative inclinations strongly affect the actual distribution of electric field. Nevertheless, in some case, small inclinations are unavoidable. The purpose of this paper is to study the electric field distribution for non-parallel needles.
Design/methodology/approach
The effect of electrode position is evaluated systematically by means of numerical models and experiments on phantoms for two different angles (5° and 30°) and compared with the case of parallel needles. Potato model was used as phantom, as this tissue becomes dark after few hours from electroporation. The electroporation degree was gauged from the color changings on the potatoes.
Findings
The distribution of electric field in different needle configuration is found by means of finite element analysis (FEA) and experiments on potatoes. The electric field level of inclined needles was compared with parallel needle case. In particular, the electric field distribution in the case of inclined needles could be very different with respect to the one in the case of parallel needles. The degree of enhancement for different inclinations is visualized by potato color intensity. The FEA suggested that the needle parallelism has to be maintained as possible as if the tips are closer to each other, the electric field intensity could be different with respect to the one in the case of parallel needles.
Originality/value
This paper analyzes the effect of inclined electrodes considering also the non-linearity of tissues.
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Catarina F. Castro, Luísa Costa Sousa, C.A.C. António and J.M.A. César de Sá
An optimisation method for design of intermediate die shapes needed in some forging operations is presented. The basic problem consists of finding an optimal two‐step forging…
Abstract
An optimisation method for design of intermediate die shapes needed in some forging operations is presented. The basic problem consists of finding an optimal two‐step forging sequence by automatically designing the shape of the preforming tools. The optimisation problem is defined based on an inverse formulation. The objective function of the optimisation problem is a function describing the quality of the obtained part by measuring the die underfill. The finite element method is used to simulate the forging problem. The optimisation method is based on a modified sequential unconstrained minimisation technique and a gradient method. The sensitivity‐dependent algorithm requires computing the derivatives of the objective function with respect to the design variables defining the preform shapes. A direct differentiation method has been developed for this purpose. The optimisation scheme is demonstrated with two axisymmetric forging examples in which optimal preform dies are obtained.
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This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder…
Abstract
This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.
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This paper gives a review of the finite element techniques (FE)applied in the area of material processing. The latest trends in metalforming, non‐metal forming and powder…
Abstract
This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming and powder metallurgy are briefly discussed. The range of applications of finite elements on the subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for the last five years, and more than 1100 references are listed.
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M. Poursina, C.A.C. António, C.F. Castro, J. Parvizian and L.C. Sousa
A numerical method for shape optimisation in forging is presented. The goal of the optimisation is to eliminate work‐piece defects that may arise during the forging process. A…
Abstract
A numerical method for shape optimisation in forging is presented. The goal of the optimisation is to eliminate work‐piece defects that may arise during the forging process. A two‐dimensional finite element code has been developed for the simulation of the mechanical process. The material is incompressible and it follows the Norton‐Hoff law. To deal with contact constraint the velocity projection algorithm is used. The optimisation process is conducted using a genetic algorithm supported by an elitist strategy. A new genetic operator called adaptive mutation has been developed to increase the efficiency of the search. The developed scheme is used to design optimal preform shapes for several axisymmetric examples. Continuous and discrete design variables are considered. The objective function of the optimisation problem is associated with the quality of the final product. Comparing the obtained optimal results with the literature validates the proposed optimisation method.