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1

Experimental study of lignite structure evolution characteristics and mechanisms under thermal-mechanical co-function

Yu Weidong

Archives of Mining Sciences

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2023

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Vol. 68, no. 4

671--684

EN

In-situ thermal upgrading modification technology is of great significance to lignite utilisation cleanly. It is an extremely complex multi-field coupling process. Therefore, it is necessary to study the physical properties of lignite under the thermo-mechanical coupling function. In this paper, the lignite pore evolution characteristics under thermal-mechanical co-function have been obtained at different scales based on experimental results. The mechanisms also have been deeply studied. The results indicated that lignite total porosity first increased and then decreased as the temperature increased from 23°C to 400°C under the triaxial stress of 7 MPa. The maximum value of 21.64% for the total porosity of lignite was observed at 200°C. Macropores were dominant when the temperature was lower than 100°C, while visible pores were dominant when at temperatures ranging from 100~400°C. The thermal weight loss and deformation characteristics of lignite were further studied using a thermal-mechanical testing platform. The weight loss and deformation process could be divided into three stages, namely the slow, rapid, and relatively slow stages. After being continuously pyrolysed for 5 hours at a temperature of 400°C, the maximum weight loss rate of lignite was 52.38%, the maximum axial linear strain was 11.12%, and the maximum irrecoverable radial strain was 18.79%. The maximum axial thermal deformation coefficient of lignite was −2.63×10 −4℃ −1 at a temperature of 289°C. Macro-deformation and component loss were the main mechanisms of lignite structure evolution.

2

A review on numerical modelling techniques in friction stir processing: current and future perspective

Marode Roshan Vijay, Pedapati Srinivasa Rao, Lemma Tamiru Alemu, Awang Mokhtar

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e154, 2023

EN

Friction stir processing (FSP) has gained significant attention worldwide since its inception due to its remarkable solid-state characteristics and microstructure refinement. However, the complex geometry of the FSP and 3-D features makes it challenging to create a set of governing equations for analyzing the post-process theoretical behavior. Due to significant deformation, experiments cannot provide comprehensive information throughout the real process, which frequently entails expense, resources, and time; numerical analysis has been examined extensively over the former to solve these concerns. Numerous alternative processes are to be simulated using FSP’s numerical analysis before physical testing to better understand the impact of various system characteristics. An attempt has been made to explore the latest research on the development of various numerical modelling techniques that lead to meaningful insight to enhance the performance of FSP. An advanced numerical technique for studying the influence of different field variables, changes in tool orientation on material flow coupled with appropriate surface contact involving temperature-dependent coefficient of friction values using advanced smoothed particle hydrodynamics on a GPU hardware configuration is still in future scope. This necessity to develop thermo-mechanical models of surface composites facilitates accurate prediction of the thermal record and particle dispersion in FSP. This article compiles computational approaches, the potential of different FEA software, and other post-processing parameters, viz., heat generation, temperature distribution, and material transition. In this regard, some vital challenges and issues regarding the numerical approaches of friction stir processing remain to be addressed, and opportunities for future research prospects are thus recommended.

3

Impact of input parameters on numerical calculations optimized by swarming algorithms during computer simulations of the heat conduction phenomenon

Zych Maria, Gawrońska Elżbieta, Dyja Robert, Krawiec Piotr

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 4

107--118

EN

The article presents the application of swarming algorithms in heat conduction, taking into account the continuity of the boundary condition (type IV). The influence of the input parameters of the bee and ant algorithm and tessellation on the selection of the heat conduction coefficient between the casting mold and the casting in computer simulations was presented. The results were compared for two different finite element grids, a different number of individuals, and a different number of iterations. The study also considered the magnitude of the reference temperature disturbance as the input temperature for numerical calculations. The analysis showed that the relative error of reproducing the value of the thermal conductivity coefficient in the continuity condition did not exceed 1.5% of the reference value of this coefficient.

4

Exact thermomechanical analysis of functionally graded (FG) thick-walled spheres

Yildirim V.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 4

1197--1221

EN

The present study aims to provide a deeper understanding for the thermo-mechanical analysis of spheres made of non-homogeneous isotropic materials. To this end, Navier equations are solved analytically based on the spherically-symmetric plain-strain assumptions and closed-form formulas are proposed for the elastic fields in a simple-power-law graded spheres subjected to steady-state thermal and internal/external pressure loads. A comprehensive parametric study is then performed with both functionally-graded hypothetical and physical materials. Two benchmark examples are reconsidered with hypothetically chosen inhomogeneity indexes. Effects of inhomogeneity indexes are reviewed in these examples. Differently from the literature, thickness effects are also examined under separate and combined loads together with the thermo-mechanical behavioral differences in spheres and cylinders. Finally three physical metal-ceramic pairs are studied originally with appropriate inhomogeneity indexes which are deffned as the inner surface is full ceramic and the outer surface is full metal. Results are presented in graphical and tabular forms.

5

The modelling of temperature-dependent stress-strain curves for weldable steels

Winczek J., Mičian M., Ivanov V.

Journal of Applied Mathematics and Computational Mechanics

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2018

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Vol. 17, nr 3

111--117

EN

The calculation of stresses in the steel elements subjected to the thermomechanical loads requires taking into account the influence of temperature on mechanical properties of a material, including the stress-strain curve. The simplified and extended computational models of temperature-dependent tensile curves have been discussed. The methodology of the stress-strain curve construction in the entire temperature range of the solid state of the material has been proposed. The considerations are illustrated by the examples of calculated stress-strain curves in different temperatures for S235 and S355 welding steels.

6

Effect of Hall current in thermoelastic materials with double porosity structure

Kumar R., Vohra R.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 2

303--319

EN

The present investigation is concerned with one dimensional problem in a homogeneous, isotropic thermoelastic medium with double porosity structure in the presence of Hall currents subjected to thermomechanical sources. A state space approach has been applied to investigate the problem. As an application of the approach, normal force and thermal source have been taken to illustrate the utility of the approach. The expressions for the components of normal stress, equilibrated stress and the temperature change are obtained in the frequency domain and computed numerically. A numerical simulation is prepared for these quantities. The effect of the Hartmann number is depicted graphically on the resulting quantities for a specific model. Some particular cases of interest are also deduced from the present investigation.

7

Modelowanie krzywych umocnienia wybranych stali spawalnych z uwzględnieniem wpływu temperatury

Winczek J., Ziobrowski P.

Modelowanie Inżynierskie

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2014

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T. 19, nr 50

77--82

PL

Obliczanie naprężeń w elementach stalowych poddanych oddziaływaniu obciążeń cieplno-mechanicznych wymaga uwzględnienia wpływu temperatury na własności mechaniczne materiału, w tym na krzywą rozciągania. W pracy, bazując na równaniach Hollomona, Ludwika, Swifta i Voce’a, omówiono modelowanie krzywych umocnienia stali S235, S355J2H i S460M z uwzględnieniem wpływu temperatury. Rozważania przeprowadzono na podstawie rezultatów badań doświadczalnych publikowanych w literaturze w postaci krzywych rozciągania wymienionych stali dla wybranych temperatur. Wyznaczono wartości parametrów w równaniach poszczególnych modeli, co umożliwiło analityczne opisanie krzywych umocnienia materiału.

EN

Calculation of stresses in the steel elements subjected to the influence of thermo-mechanical loads requires taking into account the influence of temperature on material properties, including stress-strain curve. In this paper, on the basis of Hollomon, Ludwik, Swift and Voce equations, the modeling of strain-hardening curves of steels S235, S355J2H, S460M considering the influence of temperature is discussed. The consideration were made on the basis of experimental results published in the literature as stress-strain curves for the mentioned steels for selected temperatures. The values of the parameters in the equations of the individual models were determined, which allowed to analytical description of the material strain-hardening curves.

8

Więzy termomechaniczne w teorii gradientowej

Kubik J.

Roczniki Inżynierii Budowlanej

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2013

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z. 13

111--114

EN

The theory of thermomechanical constraints is used in the work in order to derive particular forms of equations for the theory of gradient thermodiffusion. The constraints are considered for the material medium in which the gradient components of the equations do not cause additional energy dissipation.

9

Sześcioskładnikowy model degradacji żelbetu w warunkach korozji chlorkowej

Krykowski T.

Roczniki Inżynierii Budowlanej

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2013

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z. 13

67--70

EN

In the paper the six component model of corrosion concrete cover degradation has been presented. The model is based on the multicomponent media theory with the dominant constituent. In particular the paper shows the method of obtaining the constitutive equation and the evolution equation of the rate and flux type.

10

Brake system studies using numerical methods

Baranowski P., Damaziak K., Małachowski J.

Eksploatacja i Niezawodność

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2013

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Vol. 15, no. 4

337--342

EN

The paper presents the examples of numerical simulations of braking systems performed in order to determine the parameters of their work. Using a typical finite element and meshless numerical methods, dynamic analyses of the brake were performed paying particular attention on the phenomenon of thermo-mechanical coupling occurring in the process of braking, as well as wear processes occurring on the surface of the linings. The article presents sequence of research steps, including hybrid modelling of braking system.

PL

\W pracy przedstawiono przykłady symulacji numerycznych układów hamulcowych wykonanych w celu wyznaczenia parametrów ich pracy. Stosując siatkowe i bezsiatkowe metody numeryczne przeprowadzono dynamiczne analizy pracy hamulca ze zwróceniem szczególnej uwagi na zjawiska sprzężone (cieplno – mechaniczne) występujące w procesie hamowania oraz procesy zużycia zachodzące na powierzchni okładziny ciernej. W artykule przedstawiono kolejne kroki badań obejmujące modelowanie hybrydowe układu hamulcowego.

11

Higher-order FEM for analysis of coupled problems

Kansy R., Cecot W.

Czasopismo Techniczne. Budownictwo

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2013

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R. 110, z. 2-B

29--39

EN

The paper presents the application of the hp-adaptive FEM to numerical analysis of coupled problems. HP3D code is especially discussed, as well as some topics concerning mesh adaptation and numerical aspects of modeling coupled problems on the example of weakly coupled thermo-mechanical problem. Some possibilities of the new code are illustrated by a numerical example motivated by a real engineering problem. Finally, some future possible and desirable directions of development for this code are noted.

PL

W artykule przedstawiono zastosowanie hp-adaptacyjnej MES do analizy numerycznej problemów sprzężonych. W szczególności omówiono program HP3D i pewne wątki dotyczące adaptacji siatki oraz numerycznych aspektów modelowania problemów sprzężonych. Niektóre możliwości nowego programu ilustruje przykład numeryczny motywowany rzeczywistym inżynieryjnym problemem. Wskazano również na możliwe i pożądane przyszłe kierunki rozwoju tego oprogramowania.

12

Twierdzenie o wzajemności dla dystorsji gradientowych

Kubik J.

Roczniki Inżynierii Budowlanej

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2012

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z. 12

89--92

EN

In the paper the reciprocity theorem for gradient viscoelasticity with non-mechanical distortion was proposed. The theorem arises from symmetry analysis of physical equations and can be treated as a generalization of adequate theorems of classical thermo-mechanics.

13

Thermo-mechanical treatment of Fe–Mn–(Al, Si) TRIP/TWIP steels

Dobrzański L. A., Borek W.

Archives of Civil and Mechanical Engineering

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2012

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Vol. 12, no. 3

299--304

EN

Recent development in group of Fe–Mn–Al–Si steels with high-manganese content demands for more research in thermo-mechanical treatment and development of microstructure in such steels. Hot working conditions on forming the structure and course of the heat activated processes, removing the strain hardening effects, have been investigated. The chemical compositions of two high-manganese austenitic TRIP/TWIP steels containing various Mn concentrations were developed. Additionally, the steels were microalloyed by Nb and Ti in order to control the grain growth under hot-working conditions. The force-energetic parameters of hot-working were determined in continuous and multi-stage compression test performed in temperature range from 850 to 1100 °C and strain rate of 0.1, 1, 10 s−1 using the Gleeble 3800 thermo-mechanical simulator. The microstructure of investigated steels was determined in metallographic investigations using light microscope as well as X-ray diffraction. It was found that the thermo-mechanical treatment conditions have no influence on phase composition of the investigated steels.

14

Hot deformation behavior and softening kinetics of Ti–V–B microalloyed steels

Opiela M., Grajcar A.

Archives of Civil and Mechanical Engineering

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2012

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Vol. 12, no. 3

327--333

EN

Results of the effect of deformation parameters on the hot-deformation behavior and softening kinetics of two Ti–V–B-microalloyed steels were presented in the paper. The investigated steels are assigned to production of forged elements for the automotive industry by thermo-mechanical treatment. Research was conducted by compression test at elevated temperature. Hot compression test was performed using the Gleeble 3800 thermomechanical simulator at the temperature range from 900 °C to 1100 °C and strain rate of 1, 10 and 50 s−1. The σ–ε curves were determined on the basis of continuous compression and double-hit compression tests.

15

Ocena trwałości konstrukcji drogowej w numerycznym modelu termomechaniki

Bartoszek M., Fedorowicz L., Fedorowicz J.

Modelowanie Inżynierskie

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2011

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T. 10, nr 41

11-18

PL

Przedmiotem rozważań była budowa i weryfikacja przydatności numerycznego modelu do symulowania sprzężonych zjawisk cieplnomechanicznych zachodzących w konstrukcji drogi pod wpływem temperatury. Badano możliwość odtworzenia warunków powstania uszkodzeń termicznych nawierzchni drogowej oraz rozwarstwień wynikających z działania skrajnie niskich temperatur. Dostępne w literaturze pomiary temperatury in situ oraz analiza wrażliwości pozwoliły na ustalenie warunków brzegowych oraz oszacowanie wpływu brakujących parametrów cieplnych.

EN

Construction and verification of the coupled thermomechanical model of road structure was the main purpose of this paper. Numerical model was utilized to simulate structures behavior under extreme winter conditions. Our intention was to recreate real conditions leading to thermal damage of the road. Thermal in situ measurements and sensitivity analyses were necessary to establish boundary conditions of the model and to evaluate some unknown thermal properties.

16

Thermo-mechanical deformation in magneto micropolar thermoelastic medium with modified Fourier and Ohm's law

Singh R., Kumar V.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 1

83-105

EN

The present investigation is concerned with a two dimensional problem in a magnetic micropolar thermoelastic half space, whose surface is subjected to thermo-mechanical sources in the presence of transverse magnetic field with modified Ohm's and Fourier's law. The Laplace and Fourier transforms are used to solve the problem. As an application, concentrated normal force and thermal source are taken to illustrate the utility of the approach. The transformed components of displacement, stress, couple stress, electric field and current density vector are derived. Some special cases of interest are also deduced from the present investigation.

17

Funkcjonał Lagrange'a gradientowej termomechaniki

Kubik J.

Roczniki Inżynierii Budowlanej

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2010

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z. 10

39--42

EN

The aim of this paper is to providing a simple method to build a Lagrange functional for the complex interactions of thermal, mechanical and processes in the gradient thermomechanics. The formal similarity of the mass, momentum and energy balances is used

18

Unexpected properties of SH-waves in superconducting heterostructure

Drzewiecki A., Maruszewski B., Starosta R.

Vibrations in Physical Systems

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2008

|

Vol. 23

109--114

EN

The paper provides confrontation of a surface wave of SH polarization propagating in a superconducting layer (type II superconductor) located in a superconducting halfspace of similar material properties. It was found that the wave in the determined heterostructure is distinguished by the properties significantly different from classical Love wave propagating in similar elastic structure. Among more important differences first of all should be mentioned occurrence of only one mode and changed direction of the inequality that determines allowable range of phase velocity of propagating wave. Both waves are subject to normal dispersion.

19

Three dimensionaI oscillating flow between two parallel plates with heat transfer

Guria M., Jana R. N.

International Journal of Applied Mechanics and Engineering

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2007

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Vol. 12, no 1

19-35

EN

The unsteady viscous incompressible Couette flow between two parallei plates when the upper plate oscillates in its own piane and is subjected to a constant suction whereas the lower plate is subjected to a suction velocity distribution has been theoretically analyzed. An approximate solution has been obtained using perturbation technique. It is found that the main flow velocity increases with an increase in the Reynolds number as well as suction parameter but it decreases with an increases in the frequency parameter. It is also shown that with an increase in the Reynolds number, the magnitude of the cross velocity increases near the stationary plate but decreases near the oscillating plate. On the other hand, it increases with an increase in the suction parameter. The heat transfer characteristic has also been studied by taking viscous dissipation into account. It is found that the temperature increases with an increase in the Reynolds number as well as the Prandtl number but it decreases with an increase in the frequency parameter.

20

Disturbance due to mechanical and thermal sources in orthorhombic thermoelastic material

Kumar R., Rani L.

International Journal of Applied Mechanics and Engineering

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2007

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Vol. 12, no 3

677-692

EN

A dynamical two-dimensional problem of thermoelasticity has been considered to investigate the disturbance due to mechanical (horizontal or vertical) force and thermal source in a homogeneous, thermally conducting orthorhombic material. The Fourier transforms are applied to basic equations to fonn a vector matrix differential equation, which is then solved by eigenvalue approach. The displacements, stresses and temperature distribution so obtained in the physical domain are computed numerically and illustrated graphically. The numerical results of these quantities for the zinc crystal-like material are illustrated to show the comparison for various sources for the theory of coupled thermoelasticity (CT) and uncoupled thermoelasticity (UCT) for an insulated boundary and temperature gradient boundary.