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Search results for: SHEAR YIELD STRESS
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Investigations on strength and fracture in RC beams scaled along height or length
PublicationThe objective of the present paper is to identify experimentally and theoretically differing failure mechanisms in reinforced concrete beams subjected to four-point bending for a separate variation of the depth and length at the constant thickness. Experiments were performed on reinforced concrete beams under four-point bending. Different failure mechanisms included steel yielding, diagonal tension or shear- compression depending...
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Bending analysis of functionally graded nanoplates based on a higher-order shear deformation theory using dynamic relaxation method
PublicationIn this paper, bending analysis of rectangular functionally graded (FG) nanoplates under a uniform transverse load has been considered based on the modified couple stress theory. Using Hamilton’s principle, governing equations are derived based on a higher-order shear deformation theory (HSDT). The set of coupled equations are solved using the dynamic relaxation (DR) method combined with finite difference (FD) discretization technique...
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Ultimate strength of stiffened plates subjected to compressive load and spatially distributed mechanical properties
PublicationThe present study deals with the ultimate strength of stiffened plates subjected to spatially distributed mechanical properties and compressive load. Normally, mean values of mechanical properties based on tensile tests are used to validate the numerical assessment with experimental results. However, mechanical properties may vary within a single specimen. To investigate the impact of that, random fields of yield stress and Young...
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Beata Zalewska-Piątek dr hab.
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COMMENTS ON EXISTING ANALYTICAL SOLUTIONS TO THE WAVE-INDUCED CYCLIC RESPONSE OF A POROUS SEABED OF INFINITE THICKNESS
PublicationThis paper deals with the wave-induced cyclic response of a porous seabed (by means of oscillating parameters: pore-fluid pressure, soil displacement components, effective normal stress and shear stress components) due to a surface sinusoidal water-wave propagating over a seabed of infinite thickness. The main existing analytical solutions to the governing problem are critically discussed, pointing out their meaningful errors and...
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Elastoplastic law of Cosserat type in shell theory with drilling rotation
PublicationWithin the framework of six-parameter non-linear shell theory, with strain measures of the Cosserat type, we develop small-strain J2-type elastoplastic constitutive relations. The relations are obtained from the Cosserat plane stress relations assumed in each shell layer, by through-the-thickness integration employing the first-order shear theory. The formulation allows for unlimited translations and rotations. The constitutive...
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Damped forced vibration analysis of single-walled carbon nanotubes resting on viscoelastic foundation in thermal environment using nonlocal strain gradient theory
PublicationIn this paper, the damped forced vibration of single-walled carbon nanotubes (SWCNTs) is analyzed using a new shear deformation beam theory. The SWCNTs are modeled as a flexible beam on the viscoelastic foundation embedded in the thermal environment and subjected to a transverse dynamic load. The equilibrium equations are formulated by the new shear deformation beam theory which is accompanied with higher-order nonlocal strain...
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2022-2023 - Wytrzymałość materiałów I, PG_00039799
e-Learning CoursesCelem przedmiotu jest zapoznanie studentów z podstawowymi zagadnieniami związanymi z wytrzymałością materiałów. Wykłady dotyczą kolejno: podstawy wytrzymałości materiałów, wytrzymałość pręta prostego na ściskanie/rozciąganie, analiza wytrzymałości dla układów prętowych statycznie niewyznaczalnych, wytrzymałość prętów na skręcanie, wytrzymałość belek zginanie, odkształcenia belki zginanej, ścinanie pręta (pręt ścinany), stany naprężeń,...
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HYGRO-MAGNETIC VIBRATION OF THE SINGLE-WALLED CARBON NANOTUBE WITH NONLINEAR TEMPERATURE DISTRIBUTION BASED ON A MODIFIED BEAM THEORY AND NONLOCAL STRAIN GRADIENT MODEL
PublicationIn this study, vibration analysis of single-walled carbon nanotube (SWCNT) has been carried out by using a refined beam theory, namely one variable shear deformation beam theory. This approach has one variable lesser than a contractual shear deformation theory such as first-order shear deformation theory (FSDT) and acts like classical beam approach but with considering shear deformations. The SWCNT has been placed in an axial or...
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Fracture prediction in flat PMMA notched specimens under tension - effectiveness of the equivalent material concept and fictitious material concept
PublicationThe fracture of notched elements under mode I loading (tension) remains an inexhaustible research topic, especially when it comes to the fracture of thermoplastic materials such as polymethylmethacrylate (PMMA), which experience considerable plastic strains under tension. The paper points out that traditional brittle fracture criteria such as mean stress (MS) or maximum tangential stress (MTS) criteria used to predict this phenomenon do...
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Incorporating installation effects into the probability analysis of controlled modulus columns
PublicationThis technical report presents the probabilistic analysis which integrates the Monte Carlo simulation (MCS) with random field theory to model the load–displacement behavior of Controlled Modulus Columns (CMCs) in overconsolidated Poznań clay. Presented study focuses on the practical aspects of statistical analysis of geotechnical data, numerical model development, and results evaluation. Variability and spatial distribution of...
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Multiaxial Fatigue Behaviour of SLM 18Ni300 Steel
PublicationFatigue behaviour of SLM 18Ni300 steel under proportional bending-torsion loading is studied. The fatigue tests are conducted under pulsating loading conditions using tubular specimens with a transversal circular hole. Three ratios of the normal stress to shear stress are considered, namely σ/τ=4,σ/τ=2 and σ/τ = 4/3. Crack initiation sites were found for two diametrically opposite points around the hole, whose locations are governed...
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Application of fracture mechanics for energetic effects predictions while wood sawing
PublicationIn the classical approach, energetic effects (cutting forces and cutting power) of wood sawing process are generally calculated on the basis of the specific cutting resistance, which is in the case of wood cutting the function of more or less important factors. On the other hand, cutting forces (power) could be considered from a point of view of modern fracture mechanics. Cutting forces may be employed to determine not only toughness...
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Nieliniowa statyka 6-parametrowych powłok sprężysto plastycznych. Efektywne obliczenia MES
PublicationGłównym zagadnieniem omawianym w monografii jest sformułowanie sprężysto-plastycznego prawa konstytutywnego w nieliniowej 6-parametrowej teorii powłok. Wyróżnikiem tej teorii jest występujący w niej w naturalny sposób tzw. stopień 6 swobody, czyli owinięcie (drilling rotation). Podstawowe założenie pracy to przyjęcie płaskiego stanu naprężenia uogólnionego na ośrodek typu Cosseratów. Takie podejście stanowi oryginalny aspekt opracowania....
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Application of Fracture Mechanics for Energetic Effects Predictions While Wood Sawing
PublicationIn the classical approach, energetic effects (cutting forces and cutting power) of wood sawing process are generally calculated on the basis of the specific cutting resistance, which is in the case of wood cutting the function of more or less important factors. On the other hand, cutting forces (or power - more interesting from energetic point of view) could be considered from a point of view of modern fracture mechanics. Cutting...
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Tensile failure study of 3D printed PLA using DIC technique and FEM analysis
PublicationThe paper presents the experimental and numerical study of the failure behaviour of Fused Filament Fabricated (FFF) Polylactic Acid (PLA) samples subjected to tensile load. The examined samples are printed in flat orientation with 0◦, 45◦ and 90◦ raster angles. During the experiments the deformation of the specimens is continuously scanned with the 3D Aramis measuring system utilizing the digital imaging correlation technique,...
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On rotational instability within the nonlinear six-parameter shell theory
PublicationWithin the six-parameter nonlinear shell theory we analyzed the in-plane rotational instability which oc- curs under in-plane tensile loading. For plane deformations the considered shell model coincides up to notations with the geometrically nonlinear Cosserat continuum under plane stress conditions. So we con- sidered here both large translations and rotations. The constitutive relations contain some additional mi- cropolar parameters...
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Some aspects of the constitutive modelling of natural fine grained soils
PublicationThe monograph deals with selected problems of the constitutive modelling of natural fine grained soils commonly known as clays. The main idea is not to propose a unified model which is capable of describing all known features of mechanical behaviour of fine grained soils. Instead, separate models are proposed describing the mechanical behaviour of heavily overconsolidated, lightly overconsolidated and normally consolidated clays....
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Activation Energy and Inclination Magnetic Dipole Influences on Carreau Nanofluid Flowing via Cylindrical Channel with an Infinite Shearing Rate
PublicationThe infinite shear viscosity model of Carreau fluid characterizes the attitude of fluid flow at a very high/very low shear rate. This model has the capacity for interpretation of fluid at both extreme levels, and an inclined magnetic dipole in fluid mechanics has its valuable applications such as magnetic drug engineering, cold treatments to destroy tumors, drug targeting, bio preservation, cryosurgery, astrophysics, reaction kinetics,...
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Process zone in the Single Cantilever Beam under transverse loading. - Part II: Experimental
PublicationThis paper describes an experimental arrangement to evaluate stress/strain fields in the process zone of asymmetric adhesively bonded joints. A transparent polycarbonate flexible beam was bonded to an aluminium alloy rigid block with an epoxy adhesive in a Single Cantilever Beam (SCB) configuration. The flexible adherend was loaded in the direction parallel to the initial crack front at constant rate. To monitor strains induced...
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Importance of sign conventions on analytical solutions to the wave-induced cyclic response of a poro-elastic seabed
PublicationThis paper discusses the influence of different sign conventions for strains and stresses, i.e. the solid mechanics sign convention and the soil mechanics sign convention, on the form of governing partial differential equations (the static equilibrium equations and the continuity equation) used to describe the wave-induced cyclic response of a poro-elastic seabed due to propagation of a sinusoidal surface water-wave. Some selected...
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Analytical predictions for the buckling of a nanoplate subjected to non-uniform compression based on the four-variable plate theory
PublicationIn the present study, the buckling analysis of the rectangular nanoplate under biaxial non-uniform compression using the modified couple stress continuum theory with various boundary conditions has been considered. The simplified first order shear deformation theory (S-FSDT) has been employed and the governing differential equations have been obtained using the Hamilton’s principle. An analytical approach has been applied to obtain...
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Rheology of liquid crystalline polymers
PublicationLiquid crystallinity was invented in the 19th century. It was sometimes called the fourth state of matter because of the ability of macromolecules to generate liquid crystal phases. The main classification divided liquid crystalline polymers (LCPs) into lyotropic and thermotropic types. Interpretation of the rheological behavior of LCP is more complicated than for other polymers. Ordinary polymers are characterized by a normal...
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Material Identification of the Human Abdominal Wall Based On the Isogeometric Shell Model
PublicationThe human abdominal wall is an object of interest to the research community in the context of ventral hernia repair. Computer models require a priori knowledge of constitutive parameters in order to establish its mechanical response. In this work, the Finite Element Model Updating (FEMU) method is used to identify an heterogeneous shear modulus distribution for a human abdominal wall model, which is based on nonlinear isogeometric...
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Pure cross-anisotropy for geotechnical elastic potentials
PublicationThe pure cross-anisotropy is understood as a special scaling of strain (or stress). The scaled tensor is used as an argument in the elastic stiffness (or compliance). Such anisotropy can be overlaid on the top of any elastic stiffness, in particular on one obtained from an elastic potential with its own stress-induced anisotropy. This superposition does not violate the Second Law. The method can be also applied to other functions...
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Fracture mechanics model of cutting power versus widespread regression equations while wood sawing with circular saw blades
PublicationA comparison of the theoretical cutting power consumption results forecasted with the model (FM_CM model) which include work of separation (fracture toughness) in addition to plasticity and friction, and two widespread regression equations while wood sawing with circular saw blades has been described. in and cutting power consumption forecasted. In computations of the cutting power consumption during rip sawing of Scots pine wood...
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Empirical verification in industrial conditions of fracture mechanics models of cutting power prediction
PublicationA comparison of experimental results obtained in the industrial conditions at a sawmill located in the Baltic Natural Forest Region (PL) and theoretical cutting power consumption forecasted with the models which include work of separation (fracture toughness) in addition to plasticity and friction has been described. In computations of cutting power consumption during rip sawing of Scots pine wood (Pinus sylvestris L.) values of...
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Surface finite viscoelasticity and surface anti-plane waves
PublicationWe introduce the surface viscoelasticity under finite deformations. The theory is straightforward generalization of the Gurtin–Murdoch model to materials with fading memory. Surface viscoelasticity may reflect some surface related creep/stress relaxation phenomena observed at small scales. Discussed model could also describe thin inelastic coatings or thin interfacial layers. The constitutive equations for surface stresses are...
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Recent Achievements in Constitutive Equations of Laminates and Functionally Graded Structures Formulated in the Resultant Nonlinear Shell Theory
PublicationThe development of constitutive equations formulated in the resultant nonlinear shell theory is presented. The specific features of the present shell theory are drilling rotation naturally included in the formulation and asymmetric measures of strains and stress resultants. The special attention in the chapter is given to recent achievements: progressive failure analysis of laminated shells and elastoplastic constitutive relation...
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Fracture Surface Behavior of 34CrNiMo6 High-Strength Steel Bars with Blind Holes under Bending-Torsion Fatigue
PublicationThe present study evaluates the fracture surface response of fatigued 34CrNiMo6 steel bars with transverse blind holes subjected to bending with torsion loading. The analysis of the geometric product specification was performed by means of height parameters Sx, functional volume parameters Vx, and fractal dimension Df. Surface topography measurements were carried out using an optical profilometer with focus variation technology....
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Numerical modelling and analysis of steel specimens subjected to marine immersed corrosion and tensile load
PublicationThe present study develops numerical models to analyse the behaviour of steel specimens subjected to marine immersed corrosion degradation and tensile load. The finite element method with the use of the explicit dynamic solver LS-DYNA, satisfying the quasi-static conditions, is employed. Two numerical models are developed, where in the first one, the scans of surfaces gathered from corroded plate specimens are implemented directly...
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Design of Jack-up Platform for 6 MW Wind Turbine: Parametric Analysis Based Dimensioning of Platform Legs
PublicationThe article presents the results of the research conducted within the framework of the project entitled WIND-TU-PLA (ERA-NET, MARTEC II), the general aim of which was to design and analyse supporting structures for wind turbines intended for operation on the South Baltic area. The research part described in the article aimed at developing a preliminary design for a jack-up platform which can operate on water areas with depth of...
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Influence of grain shape on the mechanical behaviour of granular materials
PublicationWe performed series of numerical vertical compression tests on assemblies of 2D granular material using a Discrete Element code and studied the results in regard to the grain shape. The samples consist of 5000 grains made either of 3 overlapping discs (clump - grain with concavities) or of six-edged polygons (convex grain). These two types of grains have a similar external envelope, ruled with a geometrical parameter α. In the...
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Buckling analysis of piezo-magnetoelectric nanoplates in hygrothermal environment based on a novel one variable plate theory combining with higher-order nonlocal strain gradient theory
PublicationIn the present investigation, a new first-order shear deformation theory (OVFSDT) on the basis of the in-plane stability of the piezo-magnetoelectric composite nanoplate (PMEN) has been developed, and its precision has been evaluated. The OVFSDT has many advantages compared to the conventional first-order shear deformation theory (FSDT) such as needless of shear correction factors, containing less number of unknowns than the existing...
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Revisiting The Determination Of Cutting Power While Sawing Of Wood With Circular Saw Blades By Means Of Fracture Mechanics
PublicationIn the classical approach, energetic effects (cutting forces and cutting power) of wood sawing process are generally calculated on the basis of the specific cutting resistance, which is in the case of wood cutting the function of more or less important factors. On the other hand, cutting forces (power) could be considered from a point of view of modern fracture mechanics. Cutting forces may be employed to determine not only toughness...
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Estimation of Stresses in a Dry Sand Layer Tested on Shaking Table
PublicationTheoretical analysis of shaking table experiments, simulating earthquake response of a dry sand layer, is presented. The aim of such experiments is to study seismic-induced compaction of soil and resulting settlements. In order to determine the soil compaction, the cyclic stresses and strains should be calculated first. These stresses are caused by the cyclic horizontal acceleration at the base of soil layer, so it is important...
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Non-adiabatic Effects in Pressure Drop Calculations in Flow Boiling and Flow Condensation in Minichannels
PublicationConsiderations presented in the paper relate both to the case of flow boiling and flow condensation in conventional channels as well as small diameter ones. Authors devoted all the possible attention that the modeling presented is applicable to the whole range of quality variation in both cases of condensation and boiling. The form of two-phase flow multiplier, which is a major factor in modeling presented here, should be capable...
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Electromagnetic forced vibrations of composite nanoplates using nonlocal strain gradient theory
PublicationThis article is intended to analyze forced vibrations of a piezoelectric-piezomagnetic ceramic nanoplate by a new refined shear deformation plate theory in conjunction with higher-order nonlocal strain gradient theory. As both stress nonlocality and strain gradient size-dependent effects are taken into account using the higher-order nonlocal strain gradient theory, the governing equations of the composite nanoplate are formulated....
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Comparative 3D DEM simulations of sand–structure interfaces with similarly shaped clumps versus spheres with contact moments.
PublicationThree-dimensional simulations of a monotonic quasi-static interface behaviour between initially dense cohesionless sand and a rigid wall of different roughness during tests in a parallelly guided direct shear test under constant normal stress are presented. Numerical modelling was carried out by the discrete element method (DEM) using clumps in the form of convex non-symmetric irregularly shaped grains. The clumps had an aspect...
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Discrete-continuous optimisation of an axial flow blood pump
PublicationThis paper presents results of discrete-continuous optimisation of an axial flow blood pump. Evolution Strategies (ES) are used as a global optimisation method in order to localise the optimal solution in relatively short time. The whole optimisation process is fully automated. This also applies to geometry modelling. Numerical simulations of the flow inside the pump is performed by means of the Reynolds-Average Navier-Stokes...
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2-D constitutive equations for orthotropic Cosserat type laminated shells in finite element analysis
PublicationWe propose 2-D Cosserat type orthotropic constitutive equations for laminated shells for the purpose of initial failure estimation in a laminate layer. We use nonlinear 6-parameter shell theory with asymmetric membrane strain measures and Cosserat kinematics as the framework. This theory is specially dedicated to the analysis of irregular shells, inter alia, with orthogonal intersections, since it takes into account the drilling...
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Electroelastic biaxial compression of nanoplates considering piezoelectric effects
PublicationIn the present theoretical work, it is assumed that a piezoelectric nanoplate is connected to the voltage meter which voltages have resulted from deformation of the plate due to in-plane compressive forces whether they are critical buckling loads or arbitrary forces. In order to derive governing equations, a simplified four-variable shear deformation plate theory has been employed using Hamilton’s principle and Von-Kármán...
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Numerical investigations of discrete crack propagation in Montevideo splitting test using cohesive elements and real concrete micro-structure
PublicationThe paper is aimed at accurately predicting the discrete fracture process in concrete specimens under complex stress states in two dimensional (2D) simulations. Plain concrete specimens subjected to Montevideo splitting test (MVD) were used for consideration due to non-negligible shear stresses impact in this type of test. In order to reflect the heterogeneous nature of the concrete, the meso-structure of the samples was included...
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Strength analysis of container ship subjected to torsional loading
PublicationThe objective of this work is to investigate the torsional response of a container ship, with particular consideration of the warping effect. Two different models are investigated. In the first case, the full length model of a ship is analyzed and a distributed load is applied with the use of a novel approach. The model is supported in the torsional centre of the cross-section, which is derived analytically. In the second case,...
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Experimental study and numerical optimization of tensegrity domes – A case study
PublicationThe paper deals with the design, experimental analysis and numerical optimization of tensegrity dome models. Two structures are analyzed – a Geiger system dome (preliminary dome), with PVC-U bars and PA6/PP/PET tendons and a Fuller system dome (target dome), with wooden bars and steel cables as tendons. All used materials are experimentally tested in terms of Young's modulus and yield stress values, the compressed bars are also...
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PRESSURE DROP OF HFE7000 AND HFE7100 IN FLOW CONDENSATION IN MINICHANNELS WITH ACCOUNT OF NON-ADIABATIC EFFECTS
PublicationFlow boiling and flow condensation are often regarded as two opposite or symmetrical phenomena involving the change of phase. There is a temptation to describe both these phenomena with one only correlation. From amongst the structures present in flow boiling and flow condensation at least the annular flow structure seems to be mostly appropriate to the common modeling. However, the shear stress acting between vapor phase and liquid...
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LCF behavior of 2024AA under uni- and biaxial loading taking into account creep pre-deformation
PublicationThis study presents the results of experimental low-cycle fatigue (LCF) tests of aluminum 2024 alloy T3511 temper in uni- and biaxial loading states. Tests were carried out on both the as-received material (hardened extruded rods) and material with different pre-deformation histories. These deformations were carried out in the creep process at 200 °C and 300 °C for two different levels of at each temperature. The pre-deformed material’s...
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Direct design of Controlled Modulus Columns (CMC) based on in-situ testing
PublicationIn this paper, the serviceability limit state and bearing capacity of tension screw displacement piles were analyzed using the results of static pile load tests, carried out on the test plot near the Elbląg city, and field, and laboratory tests. The paper presents the methodology of determining the pile load-settlement curve using different types of t-z transfer functions. The new method of constructing the pile load-settlement...
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Revisiting the estimation of cutting power with different energetic methods while sawing soft and hard woods on the circular sawing machine: a Central European case
PublicationIn the classical approaches, used in Central Europe in practice, cutting forces and cutting power in sawing processes of timber are commonly computed by means of the specific cutting resistance kc. It needs to be highlighted that accessible sources in handbooks and the scientific literature do not provide any data about wood provenance, nor about cutting conditions, in which cutting resistance has been empirically determined. In...
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Corrosion fatigue crack propagation rate characteristics for weldable ship and offshore steels with regard to the influence of loading frequency and seawater temperature
PublicationAfter Vosikovsky (1975), the corrosion fatigue crack growth rate (CFCGR) characteristics have been divided into three regions. The region-III rates are very close to mechanical fatigue crack growth rates. CFCGR formulae, including the long-crack length effect (in region I only), the loading frequency effect (in region II only), and the saltwater temperature effect, have been proposed. It has been assumed that CFCGR is proportional...