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Preface.- Bolognini, L., An overview of enhanced modal identification.- Bui, H. D., Constantinescu, A., Maigre, H., The reciprocity gap functional for identifying defects and cracks.- Maier, G., Bocciarelli, M., Fedele, R., Some... more
Preface.- Bolognini, L., An overview of enhanced modal identification.- Bui, H. D., Constantinescu, A., Maigre, H., The reciprocity gap functional for identifying defects and cracks.- Maier, G., Bocciarelli, M., Fedele, R., Some innovative industrial prospects centered on inverse analyses.- Mroz, Z., Dems, K., Identification of damage in beam and plate structures using parameter dependent modal changes and thermographic methods.- Stavroulakis, G. E., Engelhardt, M., Antes, H., Crack and flaw identification in statics and dynamics, using filter algorithms and soft computing.- Toropov, V., Yoshida, F., Application of advanced optimization techniques to parameter and damage identification problems.- Waszczyszyn, Z., Ziemianski, L., Neutral networks in the identification analysis of structural mechanics problems.
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ABSTRACT A static solution is presented for the case of compression of short circular cylinders between rough, rigid plates. It is assumed that the material is perfectly plastic, satisfying the Coulomb yield condition and the associated... more
ABSTRACT A static solution is presented for the case of compression of short circular cylinders between rough, rigid plates. It is assumed that the material is perfectly plastic, satisfying the Coulomb yield condition and the associated flow law. The stress state is calculated for the edge régime of the Coulomb hexagon for which the Haar-Kármán hypothesis is satisfied. The solution is obtained for several height-diameter ratios, various friction conditions at the cylinder-plate interface and for various angles of internal friction. Results of theoretical solutions are compared with available experimental data. The analysis may be useful in experimental determination of the angle of internal friction and cohesion by compressing short cylinders between rigid plates.
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The present paper is concerned with the modelling of fatigue crack ini-tiation and propagation by applying the non-local critical plane model, proposed by Seweryn and Mróz (1996, 1998). Using the linear elastic stress field at the front... more
The present paper is concerned with the modelling of fatigue crack ini-tiation and propagation by applying the non-local critical plane model, proposed by Seweryn and Mróz (1996, 1998). Using the linear elastic stress field at the front of a crack or sharp notch, the damage growth on a physical plane is specified in terms of mean values of the stress and strength function. The model is applied to study crack propagation under cyclically varying tension-compression conditions. The predictions are compared with experimental data. Key words: fatigue, damage accumulation, crack propagation 1.
The most important effects related to monotonic and cyclic response of con-tact interfaces of brittle materials are analyzed in the paper. Next, the availa-ble constitutive models are reviewed with respect to their ability to describe... more
The most important effects related to monotonic and cyclic response of con-tact interfaces of brittle materials are analyzed in the paper. Next, the availa-ble constitutive models are reviewed with respect to their ability to describe these effects. Several micro-mechanical mechanisms are analyzed including de-cohesion, interaction of primary and secondary asperities, asperity wear and damage and formation of a third body granular layer. Finally, we propose new formulations of constitutive models for cyclic interface response.
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Most structural components contain inhomogeneities such as hardened surface layers or coatings, welded or bonded elements, etc. The crack growth mode then depends not only on applied loading and structure geometry but also on material... more
Most structural components contain inhomogeneities such as hardened surface layers or coatings, welded or bonded elements, etc. The crack growth mode then depends not only on applied loading and structure geometry but also on material inhomogeneity. In the presentation the analysis of crack growth mode will be discussed for two cases: a bi-material structure with two materials of different thermo-elastic and plastic properties connected along the interface and a structure with introduced interlayer of different material. The simplified approach is presented, namely the MK-criterion (1,2) based on the linear elastic fracture mechanics (LEFM). In the criterion it is assumed that crack growth follows the direction of minimum distortion energy density at a distance corresponding to specified value of dilatation energy. For two materials, A and B the crack growth from A to B or along the interface AB may occur depending on relative critical stress and fracture energy values. For a three-...
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The present paper is concerned with the modelling of fatigue crack initiation and propagation by applying the non-local critical plane model, proposed by Seweryn and Mroz (1996, 1998). Using the linear elastic stress field at the front of... more
The present paper is concerned with the modelling of fatigue crack initiation and propagation by applying the non-local critical plane model, proposed by Seweryn and Mroz (1996, 1998). Using the linear elastic stress field at the front of a crack or sharp notch, the damage growth on a physical plane is specified in terms of mean values of the stress and strength function. The model is applied to study crack propagation under cyclically varying tension-compression conditions. The predictions are compared with experimental data.
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To determine limit states of mechanical structures has always been one of the most important design issues in mechanical and civi l engineering and long before modern computational tools had been available, engineering scientists and... more
To determine limit states of mechanical structures has always been one of the most important design issues in mechanical and civi l engineering and long before modern computational tools had been available, engineering scientists and mathematicians have developed methods to deal with this question. For this, most important is to identify failure mechanisms in their particular technical context, to model them and to understand the structural evolution leading to the according limit state. Among the large variety of scenarios, we deal here exclusively with failure caused directly by inelastic material behaviour, concentrating on ductile metal or metal-li ke materials. From methodological point of view, only so-called Direct Methods, in particular Limitand Shakedown Analysis are considered. Limit Analysis, applicable only in the case of monotone loading is considered as particular case of Shakedown analysis, valid for variable loads with not deterministicall y given loading histories. ...
The elasto-plastic hardening model for austenitic steels undergoing plastic strain induced martensitic transformation is presented with application to both monotonic and cyclic loading processes. The kinematic hardening rule is assumed... more
The elasto-plastic hardening model for austenitic steels undergoing plastic strain induced martensitic transformation is presented with application to both monotonic and cyclic loading processes. The kinematic hardening rule is assumed and expressed in terms of the back stress Z composed of two portions X and Xt , the first related to plastic strain, the other to phase transformation and volume fraction of martensite. The transformation process is assumed to be driven by the back stress difference X – Y, where Y is the transformation back stress related to growth of the martensitic phase. The non-linear coupling of hardening and phase transformation processes occurs due to interaction of back stresses X and Xt. The thermodynamic framework is applied by introducing state variables and conjugate forces used in specifying the plastic flow and evolution rules. The model is applied to simulate cyclic hardening response for uniaxial tension-compression tests and for combined tension-torsi...
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Welcome Address.- Welcome Address.- Session 1. Mathematical Methods.- A Graph Problem of Structural Design.- Applications of Optimal Control Theory to Structural Optimization: Analytical and Numerical Approach.- Interactive and Automated... more
Welcome Address.- Welcome Address.- Session 1. Mathematical Methods.- A Graph Problem of Structural Design.- Applications of Optimal Control Theory to Structural Optimization: Analytical and Numerical Approach.- Interactive and Automated Design of Ship Structures.- On Variational Formulations for Structures Design Problems.- Session 2. Mathematical Methods.- Optimal Control of the Consolidation Process.- On Singularities, Local Optima, and Formation of Stiffeners in Optimal Design of Plates.- A Variational Formulation of the Optimal Plastic Design Problem with Linear and Convex Cost Function.- Session 3. Mathematical Programming.- Game Problems in the Theory of Optimal Design.- Application of Dynamic Programming to Optimization of Structures.- Session 4. Dynamics.- Optimum Design of a Circular Shaft in Forward Precession.- Optimal Design Criteria of Dynamically Loaded Elastic Structures.- Optimal Design for Stability under Dissi-pative, Gyroscopic, or Circulator Loads.- Session 5. S...
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Wall stresses are very important parameter in processes run in silos and tanks. DEM method appeared to be a very useful numerical tool in simulation of granular materials [1]. The paper presents the comparison of measured wall stresses... more
Wall stresses are very important parameter in processes run in silos and tanks. DEM method appeared to be a very useful numerical tool in simulation of granular materials [1]. The paper presents the comparison of measured wall stresses exerted by 20,400 pea grains with DEM simulation in the model of silo by the DEMMAT code [2]. Two sensors of 55 mm in diameter were placed on the lateral wall and wall stresses were registered.
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The models of crack growth in mixed mode conditions are reviewed for the plane(2D)and three-dimensional (3D) states of stress. Both critical load value and crack path orsurface growth are predicted by different criteria in terms of... more
The models of crack growth in mixed mode conditions are reviewed for the plane(2D)and three-dimensional (3D) states of stress. Both critical load value and crack path orsurface growth are predicted by different criteria in terms of elastic singular stressstates and T-stress component. Both monotonic and cyclic loading are considered. Theconcepts of smooth and rough crack surface are discussed with application to 3D cracksurface growth.
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Abstract The stability of discrete elastic systems subjected to conservative loading is governed by the potential energy, which is a function of the generalized coordinates. When dry friction is present, it affects the stability... more
Abstract The stability of discrete elastic systems subjected to conservative loading is governed by the potential energy, which is a function of the generalized coordinates. When dry friction is present, it affects the stability conditions and the post-critical response. Quasi-static loading is considered and the normal forces to the friction surface are assumed to be specified. General critical state conditions are obtained in terms of the potential energy and the dissipation function. Then several examples are presented to illustrate various types of behavior. It is seen that limit points, bifurcation points, and transition points (associated with slip activation or deactivation) may occur on the deformation path, and that a sudden “snap” from one state to another is a common phenomenon when the system includes dry friction.
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... The stability conditions are derived and applied to several simple illustrative examples. I. INTRODUCTION ... Page 2. 96 DEMS AND MR ~ Z of interacting cracks was considered by Bazant and Ohtsubo [3], Nemat-Nasser, Sumi, and Keer [4],... more
... The stability conditions are derived and applied to several simple illustrative examples. I. INTRODUCTION ... Page 2. 96 DEMS AND MR ~ Z of interacting cracks was considered by Bazant and Ohtsubo [3], Nemat-Nasser, Sumi, and Keer [4], and others. ...
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A general variational formulation of the optimal column problem in which the column shape is either prescribed over given segments or can be varied continuously is outlined. Necessary conditions are derived for the optimal location of... more
A general variational formulation of the optimal column problem in which the column shape is either prescribed over given segments or can be varied continuously is outlined. Necessary conditions are derived for the optimal location of segment boundaries and internal supports. Most previously published optimality criteria are shown to be special cases of the general conditions presented. The proposed theory
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ABSTRACT For global behavioral constraints, the problem of optimal design of plates and shells is formulated by assuming the design to be dependent upon a set of design parameters. Global minimum theorems are proved for some constraints,... more
ABSTRACT For global behavioral constraints, the problem of optimal design of plates and shells is formulated by assuming the design to be dependent upon a set of design parameters. Global minimum theorems are proved for some constraints, whereas for others only local extremum conditions are derived. A possibility of constructing some numerical algorithms by using the optima-lity condition and proper variational principle is discussed. The following behavioral constraints are considered: prescribed mean compliance measurer1 as the work of surface tractions, prescribed local deflection of linearly or nonlincarly elastic structure, given set of several free frequencies, prescribed safety factor for limit load of a plastic structure, any global constraint ex pressed as a surface integral with integrand depending on generalized stresses or strains.
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Abstract Considering arbitrary stress, strain or displacement functionals specified over a domain of an elastic, homogeneous and isotropic body, their invariance is proved for the case of translation, rotation and scale change of an... more
Abstract Considering arbitrary stress, strain or displacement functionals specified over a domain of an elastic, homogeneous and isotropic body, their invariance is proved for the case of translation, rotation and scale change of an arbitrary domain within the body. The assosciated class of path-independent integrals is derived. It is shown that sensitivity analysis with respect to translation, rotation or expansion of defects can be performed by using these path-independent integrals.
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Abstract Disks and plates subjected to stretching and flexure are stiffened by curvilinear ribstiffeners whose shape and cross-sectional area are subject to optimization. Sensitivity analysis is first discussed for an arbitrary integral... more
Abstract Disks and plates subjected to stretching and flexure are stiffened by curvilinear ribstiffeners whose shape and cross-sectional area are subject to optimization. Sensitivity analysis is first discussed for an arbitrary integral functional of generalized stress, strain and displacement and boundary domains. The optimality conditions are next derived. The general theory is illustrated by three examples of optimal design of ring-stiffeners in circular disks and plates and of rib-stiffeners in a rectangular plate.
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The damage accumulation condition expressed in terms of traction components on a physical plane is discussed for both monotonic and cyclic loading conditions. The crack initiation is assumed to correspond to a critical value of damage... more
The damage accumulation condition expressed in terms of traction components on a physical plane is discussed for both monotonic and cyclic loading conditions. The crack initiation is assumed to correspond to a critical value of damage reached on the physical plane. For singular stress distribution in the front of sharp notch or crack the non-local condition is formulated. The proposed
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1st. J. Solids Strucuwa Vol. 19, No. 8, pp. 677692, 1983 00W83 3.1XI+ .00 Printnl in Great Britain 1983 perffflon Press Lid. VARIATIONAL APPROACH BY MEANS OF ADJOINT SYSTEMS TO STRUCTURAL OPTIMIZATION AND SENSITIVITY ANALYSIS1 VARIATION... more
1st. J. Solids Strucuwa Vol. 19, No. 8, pp. 677692, 1983 00W83 3.1XI+ .00 Printnl in Great Britain 1983 perffflon Press Lid. VARIATIONAL APPROACH BY MEANS OF ADJOINT SYSTEMS TO STRUCTURAL OPTIMIZATION AND SENSITIVITY ANALYSIS1 VARIATION OF ...
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A problem of optimal design for perfectly plastic, isotropic structures is analyzed. It is shown that for such structures as plates or shells, an extremum of the volume, if it exists, is either a local maximum or a minimum.
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The constitutive model of the interface layer is first discussed using the concept of the critical state model. Next, the dynamic dilatancy effect occuring in rapid flows of granular materials is described by applying the viscoplastic... more
The constitutive model of the interface layer is first discussed using the concept of the critical state model. Next, the dynamic dilatancy effect occuring in rapid flows of granular materials is described by applying the viscoplastic model. It is assumed that the critical state line is a unique function of actual material density. Static and kinematic conditions at the interface are discussed and the effect of strain rate on dilatancy or transverse pressure is analysed.
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A multisurface hardening model is modified in order to describe cyclic hardening phenomena occurring for proportional and non-proportional monotonic and cyclic loading. A complex interaction of cyclic loading histories can be described by... more
A multisurface hardening model is modified in order to describe cyclic hardening phenomena occurring for proportional and non-proportional monotonic and cyclic loading. A complex interaction of cyclic loading histories can be described by using proper evolution rules for consecutive surfaces associated with specified hardening moduli. Next, the integral description of back stress evolution is considered with the memory of maximal prestress incorporated into the model. These two descriptions are applied to simulate the deformation response of stainless steel 316 for a variety of loading programmes and their predictions are compared.
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Considering an arbitrary behavioural functional specified for a mixed Dirichlet-Neumann boundary-value problem, its first variation with respect to variation of domain shape is derived using the material derivative concept and adjoint... more
Considering an arbitrary behavioural functional specified for a mixed Dirichlet-Neumann boundary-value problem, its first variation with respect to variation of domain shape is derived using the material derivative concept and adjoint approach. Next the invariance of this functional is proved for the case of translation, rotation and scale change of an arbitrary homogeneous and isotropic domain of a problem. The associated path-independent integrals are derived and it is shown that the sensitivity analysis with respect to translation, rotation or expansion of defects can be performed by using these integrals
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Abstract A general constitutive model for concrete is discussed in which the total strain rate is decomposed into elastic, plastic and damage strain rates. The rate equations are formulated for all strain rate portions together with... more
Abstract A general constitutive model for concrete is discussed in which the total strain rate is decomposed into elastic, plastic and damage strain rates. The rate equations are formulated for all strain rate portions together with evolution rules for hardening and damage state variables. The coupling effect between damage and plastic deformation is considered by introducing yield and damage surfaces and formulating proper interaction rules. Both axisymmetric and general threedimensional stress states are considered for which monotonic and cyclic loading conditions are assumed. The model is aimed to describe material behavior for a variety of loading histories. Its applicability is illustrated by considering uniaxial, biaxial and triaxial compression with superposed shear stresses.
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In the paper a class of wear problems is considered, for which the contact zone is fixed on one of contacting bodies and translates on the surface of another body, like in the case of punch in relative translation on a substrate. In the... more
In the paper a class of wear problems is considered, for which the contact zone is fixed on one of contacting bodies and translates on the surface of another body, like in the case of punch in relative translation on a substrate. In the case of constant normal loads interacting with the induced monotonic sliding, the steady state wear process is reached. In the case of fixed normal load and the reciprocal sliding condition the wear process tends to its steady periodic state. Similarly, for periodically varying normal load, a steady periodic state is reached for the case of monotonic sliding. A most general case occurs for in-phase or out-of-phase periodic variation of normal load interacting with the reciprocal sliding. The paper is aimed to provide further study of steady wear states by considering periodically varying normal load combined with monotonic or alternating sliding conditions. The illustrative examples demonstrate the contact pressure and wear distribution in steady states with application to brake wear analysis.