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1
Content available The thermoelastic state of a bi-material with an open gas-filled interface crack
Serednytska Khristina, Martynyak Rostyslav, Chumak Kostyantyn
Journal of Theoretical and Applied Mechanics
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2019
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Vol. 57 nr 2
331--341
EN
The thermoelastic behavior of a bi-material with a gas-filled interface crack is investigated. The bi-material is subjected to a uniform tensile load and a uniform heat flow. The gas exerts pressure on the crack surfaces and offers thermal resistance proportional to the crack opening. The gas state is assumed to be described by the ideal gas law. The effects of gas mass, gas thermal conductivity and heat flux on the crack opening, interface temperature jump, gas pressure and stress intensity factors are analyzed. It is revealed that a bi-material with a heat-conducting crack exhibits the heat flow directional effect.
2
Content available Criterion for crack initiation from notch located at the interface of bi-material structure
Mieczkowski Grzegorz
Eksploatacja i Niezawodność
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2019
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Vol. 21, no. 2
301--310
EN
The fracture process of bi-material structure with the notch was analysed in this work. For fracture prediction, a criterion based on the Theory of Critical Distances was used. Under analysis were elements made of aluminium alloy and polymer combination (with a various structural notch-tip angle), which then were subjected to the three-point bending test. Values of critical loads resulting from the used hypothesis were compared with values obtained from the experiment. Validation of the selected criterion required defining a qualitative and quantitative description of singular stress fields present around the structural notch-tip area. Therefore, such solutions were obtained and methodology of their determining was discussed.
PL
W pracy przedstawiono wyniki badań dotyczących pękania struktury bi-materiałowej z karbem usytuowanym na interfejsie. Do prognozowania inicjacji procesu pękania zastosowano kryterium oparte na punktowej teorii krytycznych dystansów. Analizowano elementy wykonane ze stopu aluminium i polimerów (PC, PMMA), które poddane były trójpunktowemu zginaniu. Wartości obciążeń krytycznych wynikających z wykorzystanej hipotezy porównano z wartościami uzyskanymi z eksperymentu. Walidacja wybranego kryterium wymagała określania jakościowego i ilościowego opisu osobliwych pól naprężeń, występujących w okolicy wierzchołkowej karbu strukturalnego. W związku z tym, uzyskano takie rozwiązania i omówiono metodykę ich otrzymywania.
3
Content available Application of Thermo-Bimaterial Effect in Designing of Snap-Fit Joints
Golewski P., Sadowski T.
Archives of Metallurgy and Materials
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2019
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Vol. 64, iss. 3
1095--1100
EN
Snap-fit connections have been used for many years in various fields of technology and everyday objects. They often have complex shapes, which is allowed by the processing technology of the polymers from which they are made, but they are not designed to carry loads. Changing the material to a metal or fiber composite allows these types of joints to be used as replacements for rivets or screws, but there are problems with the closing technique – an increase in closing force due to the large Young’s modulus ofthese materials relative to polymers without reinforcement. One of the methods to solve this problem may be the use of a thermo-bimetallic effect consisting in heating both or one of the connection parts to the appropriate temperature. This kind of treatment results in deflection of the beam of the clip (Fig. 1), followed by assembly with zero force or less in relation to the case without heating.The paper presents the results of numerical simulations for the connection in which the beam of the clip consisted of two materials: (1) a fiber composite designed to carry loads, (2) thin metal layer tied with the composite and designed to create a thermo-bimetallic effect. In the case of this solution, the main parameter is the difference in coefficients of linear thermal expansion of both materials. The paper presents results for two cases of connection work: closing and opening. The calculations were carried out in the Abaqus/Standard solver using thermal-displacement steps.
4
Content available Boundary integral equations for an anisotropic bimaterial with thermally imperfect interface and internal inhomogeneities
Sulym H., Pasternak I., Tomashivskyy M.
Acta Mechanica et Automatica
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2016
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Vol. 10, no. 1
66--74
EN
This paper studies a thermoelastic anisotropic bimaterial with thermally imperfect interface and internal inhomogeneities. Based on the complex variable calculus and the extended Stroh formalism a new approach is proposed for obtaining the Somigliana type integral formulae and corresponding boundary integral equations for a thermoelastic bimaterial consisting of two half-spaces with different thermal and mechanical properties. The half-spaces are bonded together with mechanically perfect and thermally imperfect interface, which model interfacial adhesive layers present in bimaterial solids. Obtained integral equations are introduced into the modified boundary element method that allows solving arbitrary 2D thermoelacticity problems for anisotropic bimaterial solids with imperfect thin thermo-resistant interfacial layer, which half-spaces contain cracks and thin inclusions. Presented numerical examples show the effect of thermal resistance of the bimaterial interface on the stress intensity factors at thin inhomogeneities.
5
Content available Antiplane deformation of a bimaterial containing an interfacial crack with the account of friction. [P.] 1, Single loading
Sulym H., Piskozub L., Piskozub Y., Pasternak I.
Acta Mechanica et Automatica
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2015
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Vol. 9, no. 2
115--121
EN
The paper presents the exact analytic solution to the antiplane problem for a non-homogeneous bimaterial medium containing closed interfacial cracks, which faces can move relatively to each other with dry friction. The medium is subjected to the action of normal and arbitrary single loading in a longitudinal direction. Based on the discontinuity function method the problem is reduced to the solution of the system of singular integral-differential equations for stress and displacement discontinuities at the possible slippage zones. Influence of loading parameters and the effects of friction on the sizes of these zones is analyzed. The stress intensity factors, stress and displacement discontinuities, energy dissipation are determined for several characteristic types of external loading.
6
Content available Antiplane deformation of a bimaterial containing an interfacial crack with the account of friction 2. Repeating and cyclic loading
Sulym H., Piskozub L., Piskozub Y., Pasternak I.
Acta Mechanica et Automatica
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2015
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Vol. 9, no. 3
178--184
EN
The paper presents the exact solution of the antiplane problem for an inhomogeneous bimaterial with the interface crack exposed to the normal load and cyclic loading by a concentrated force in the longitudinal direction. Using discontinuity function method the problem is reduced to the solution of singular integral equations for the displacement and stress discontinuities at the domains with sliding friction. The paper provides the analysis of the effect of friction and loading parameters on the size of these zones. Hysteretic behaviour of the stress and displacement discontinuities in these domains is observed.
7
Content available remote The compliance approach for analyzing bimaterial interface cracks
Abdel-Fattah H., Hamoush S. A.
Computer Assisted Mechanics and Engineering Sciences
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2004
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Vol. 11, No. 4
275-281
EN
A numerical method is presented for analyzing the mixed mode interface crack between two dissimilar isotropic materials. A simple and efficient solution procedure is developed based on the finite element method and the compliance approach in conjunction with the fundamental relations in fracture mechanics. The procedure makes it possible to separate the Mode I and Mode II stress intensity factors KI and KII respectively for an interfacial crack in bi-material media under different loading conditions. The strain energy release rate is first computed, then using the compliance method and the known auxiliary solutions, the values for KI and KII are evaluated. The procedure is investigated for different crack extensions. The formulations used for computing the strain energy release rate and the stress intensity factors are presented. The method converges to accurate solutions for small crack extensions. A numerical example is presented to demonstrate the accuracy of the proposed model.
8
Methods for an estimation of thershold values for fatique crack propagation through a bi-material interface
Nahlik L.
Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska
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2003
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nr 21
179-184
EN
elastic materials under assumptions of linear-elastic fracture mechanics. Two procedures for the estimation of threshold values for further crack propagation from bi-material interface to the second material are suggested. One of the is related to the area of the plastic zone in front of the crack tip, while the second one is based on the Sih's strain energy density concept. Special attention is devoted to a crack perpendicularly oriented to the bi-material interface. It is shown that the corresponding fatigue threshold value is strongly influenced by the existence of an interface between the two materials. Both methods are used to quantify the threshold values of the fatigue crack propagation and simultaneously compare the relative accuracy of both approaches. On the basis of the obtained results, it seems promising to use any approach in the decision on whether the crack will stop at the interface or will continue growing into the second material.
9
Content available remote Partial material replacement without stress redistribution
Matuszak A.
Archives of Mechanics
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2002
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Vol. 54, nr 1
35-54
EN
A partial material replacement causes stress redistribution in comparison to the original structure made of a homogeneous material. The article presents a possibility to design a geometry of the replacement which keeps the state of stress unchanged. It is shown that for a class of two-dimensional configurations, it is possible to find a solution of this problem. Conditions for the existence of an appropriate geometry are given. A method to obtain the shape of the replaced part is proposed.
10
Content available Growth of plastic zones due to heat loading near a closed interface crack
Kit H., Martynyak R., Kryshtafovych A.
Journal of Theoretical and Applied Mechanics
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1998
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nr 2
249-261
EN
A bimaterial consisting of two conjugated half-planes possessing different thermophysical characteristics, with an interface crack closed due to external pressure is considered. The growth of interface plastic zones near the crack tips, caused by a heat flow and thermal resistance of crack faces, is investigated. The complex potentials of the problem that define main characteristics of the bimaterial thermal stress state are expressed in terms of interface jump discontinuities of temperature and tangential displacements, which simulate the crack and plastic zones. A system of singular integro-differential equations in these functions is obtained. The length of plastic zones is derived from the condition for interface shear stress boundedness in the tips of these zones. The closed form expresions for the displacement jumps of the bimaterial components and the plastic zones length are obtained for a certain thermal resistance.
PL
Praca poświęcona jest analizie utworzenia cienkich stref plastycznych wokół końców szczeliny umieszczonej na międzyfazowej granicy bimateriału złożonego z termicznie różnych półpłaszczyzn. Bada się rozwój odkształceń plastycznych spowodowany strumieniem cieplnym i oporem termicznym jej brzegów wokół końców zamkniętej zewnętrznym ciśnieniem szczeliny. Potencjały zespolone, które wyznaczają stan termosprężysty bimateriału, przedstawione są przez międzyfazowe nieciągłości temperatury i przemieszczeń stycznych, którymi modelowana jest szczelina i strefy plastyczne. Dla ich wyznaczania otrzymany jest układ równań singularnych całkowo-różniczkowych. Długość stref plastycznych oblicza się z warunku ograniczaności naprężeń stycznych międzyfazowych na końcach tych stref. Dla konkretnego oporu termicznego szczegółowo przeanalizowano nieciągłość przemieszczeń brzegów szczeliny i długość raf plastycznych.
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