Wyniki wyszukiwania - BazTech

1

Numerical analysis of the heating of a die for the extrusion of aluminium alloy profiles in terms of thermochemical treatment

Joachimiak Damian, Judt Wojciech, Joachimiak Magda

Archives of Thermodynamics

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2023

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Vol. 44, no 2

159--175

EN

Thermochemical treatment processes are used to produce a surface layer of the workpiece with improved mechanical properties. One of the important parameters during the gas nitriding processes is the temperature of the surface. In thermochemical treatment processes, there is a problem in precisely determining the surface temperature of heat-treated massive components with complex geometries. This paper presents a simulation of the heating process of a die used to extrude aluminium profiles. The maximum temperature differences calculated in the die volume, on the surface and at the most mechanically stressed edge during the extrusion of the aluminum profiles were analysed. The heating of the die was simulated using commercial transient thermal analysis software. The numerical calculations of the die assumed a boundary condition in the form of the heat transfer coefficient obtained from experimental studies in a thermochemical treatment furnace and the solution of the nonstationary and non-linear inverse problem for the heat conduction equation in the cylinder. The die heating analysis was performed for various heating rates and fan settings. Major differences in the surface temperature and in the volume of the heated die were obtained. Possible ways to improve the productivity and control of thermochemical treatment processes were identified. The paper investigates the heating of a die, which is a massive component with complex geometry. This paper indicates a new way to develop methods for the control of thermochemical processing of massive components with complex geometries.

2

Coefficient inequalities for a subclass of Bazilevič functions

Fitri Sa’adatul, Marjono, Thomas Derek K., Wibowo R. B. E.

Demonstratio Mathematica

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2020

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Vol. 53, nr 1

27--37

EN

Let f be analytic in D={z:|z| < 1} with f(z)=z+∑∞n=2anzn, and for α ≥ 0 and 0 < λ ≤ 1, let B1(α,λ) denote the subclass of Bazilevič functions satisfying (…) <λ for 0 < λ ≤ 1. We give sharp bounds for various coefficient problems when f ∈ B1(α,λ), thus extending recent work in the case λ = 1.

3

A numerical algorithm for computing the inverse of a Toeplitz pentadiagonal matrix

Talibi B., Hadj D. A., Sarsri D.

Journal of Applied Mathematics and Computational Mechanics

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2018

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Vol. 17, nr 3

83--95

EN

In the current paper, we present a computationally efficient algorithm for obtaining the inverse of a pentadiogonal toeplitz matrix. Few conditions are required, and the algorithm is suited for implementation using computer algebra systems.

4

Investigation of the effect of thermal diffusivity coefficient of tool material on electrode-tool wear in the EDM process

Joudivand Sarand M. H., Shabgard M. R.

Archives of Civil and Mechanical Engineering

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2015

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Vol. 15, no. 4

806--821

EN

Tool wear occurrence causes a variety of difficulties including expensive and inaccurate cutting processes. Therefore, it is imperative to determine which parameter has the most influence on tool erosion rate. Since EDM is basically a thermal process, it is mostly affected by thermo physical properties of tool material. This becomes more important in numerically modeling of EDM process which contributes a better understanding of the wear mechanism. This study aimed to examine the effect of thermal diffusivity on tool erosion rate which has not yet been investigated in detail. Therefore, the experiments were conducted using copper alloy, copper-iron alloy, aluminum alloy and graphite as tools and AISI H13 as workpiece. Additionally, numerical simulation of tool wear was performed using Levenberg–Marquardt technique to gain better understanding of tool wear phenomenon. Results revealed that, increase of thermal diffusivity of tool material decreases tool wear rate. It is observed that in the experiments, performed using tool electrodes with low thermal diffusivity coefficient, the increase of wear rate is significantly intensified with increase of current and pulse on-time. Comparative analysis of the experimental and numerical results indicates that the introduced numerical simulation is capable of estimating tool wear rate with 5% average error, approximately.

5

Trefftz function for solving a quasi-static inverse problem of thermal stresses

Grysa K., Maciąg A., Maciejewska B.

Computer Assisted Mechanics and Engineering Sciences

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2009

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Vol. 16, No. 3/4

251-266

EN

The problem of thermal stresses in a hollow cylinder is considered. The problem is two-dimensional and the cross-section of the hollow cylinder is approximated as a long and thin rectangle as the ratio of the inner and outer radiuses is close to one. On the outer boundary of the hollow cylinder the heat source moves with a constant velocity. In the case of the rectangle the heat source moves on the upper side and the conditions of eąuality of temperatures and heat fluxes are assumed on the left and right boundaries. The stresses are to be found basing on the temperature measured inside the considered region, which means that an inverse problem is considered. Both for the temperature field and the displacements and stresses the finite element method is used. Thermal displacement potentials are introduced to find displacements and stresses. In order to construct the base functions in each element the Trefftz functions are used. For the temperature field the time-space finite elements are used and for the thermal displacement potentials the spatial elements are applied. Thanks to the use of the Trefftz functions a low-order approximation has given a solution very close to the exact one.

6

Recent developments in numerical homogenization

Boso D. P., Lefik M., Schrefler B. A.

Computer Assisted Mechanics and Engineering Sciences

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2009

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Vol. 16, No. 3/4

161-183

EN

This paper deals with homogenization of non linear fibre-reinforced composites in the coupled thermo-mechanical field. For this kind of structures, i.e. inclusions randomly dispersed in a matrix, the self consistent methods are particularly suitable to describe the problem. Usually, in the framework of the self consistent scheme the homogenized material behaviour is obtained with a symbolic approach. For the non linear case, that method may become tedious. This paper presents a different, fully numerical procedure. The effective properties are determined by minimizing a functional expressing the difference (in some chosen norm) between the solution of the heterogeneous problem and the equivalent homogenous one. The heterogeneous problem is solved with the Finite Element method, while the second one has its analytical solution. The two solutions are written as a function of the (unknown) effective parameters, so that the final global solution is found by iterating between the two single solutions. Further, it is shown that the considered homogenization scheme can be seen as an inverse problem and Artificial Neural Networks are used to solve it.

7

Inverse identification technique in loading forces detection formulation and verification study. Part 1

Uhl T.

Archives of Transport

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2004

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Vol. 16, iss.4

83-96

EN

In the paper loading forces identification techniques are presented. The inverse identification techniques are based on assumed objective function optimisation methods. The theoretical background and main limits of the applications are discussed. Formulated method has be en tested employing laboratory tests in which loading forces are measured and estimated using inverse identification procedure. Applicability of the method for identification of track/wheel contact force is shown.

PL

W artykule przedstawiono metodę identyfikacji sił obciążających konstrukcje w wyniku pomiaru odpowiedzi układu. Do rozwiązania problemu zastosowano metodę odwrotnego zadania identyfikacji sformułowaną na podstawie minimalizacji przyjętego kryterium jakości modelu. Przedstawiono podstawy teoretyczne metody oraz ograniczenie w jej zastosowaniach. Sformułowaną metodę zweryfikowano, stosując wyniki symulacji zachowania układu mechanicznego oraz na stanowisku badawczym przez porównanie zidentyfikowanej siły i zmierzonej bezpośrednio. Metoda będzie zastosowana do identyfikacji sił oddziaływania w układzie koło - szyna.