Search results for: mechanics
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Modelling and analysis of beam/bar structure by application of bond graphs
PublicationThe paper presents an uniform, port-based approach to modelling of beam/bar systems (trusses). Port-based model of such distributed parameter system has been defined by application of the bond graph methodology and the distributed transfer function method (DTFM). The proposed method of modelling enables to formulate input data for computer analysis by application of the DTFM. The constructed computational package enables the frequency...
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Investigations of Aerodynamics of Tesla Bladeless Microturbines
PublicationThe paper presents an analysis of a Tesla bladeless turbine for a co-generating micro-power plant of heat capacity 20 kW, whichoperates in an organic Rankine cycle with a low-boiling medium. Numerical calculations of flow in several Tesla turbine models areperformed for a range of design parameters. Results of investigations exhibit interesting features in the distribution of flowparameters within the turbine interdisk space. The...
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Parameter estimation of a discrete model of a reinforced concrete slab
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Experimental validation of the use of energy transfer ratio (ETR) for damage diagnosis of steel-concrete composite beams
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ADAPTATION OF ENGINEERING FEA-BASED ALGORITHMS TO LCF FAILURE AND MATERIAL DATA PREDICTION IN OFFSHORE DESIGN
PublicationThere is an ever growing industrial demand for quantitative assessment of fatigue endurance of critical structural details. Although FEA-based calculations have become a standard in engineering design, problems involving the Low-To-Medium cycle range (101-104) remain challenging. This paper presents an attempt to optimally choose material data, meshing density and other algorithm settings in the context of recent design of the...
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Fe-Al based composite reinforced with ultra-fine Al<sub>2</sub>O<sub>3</sub> oxides for high temperature applications
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Assessment of fatigue life of aluminized, coarse-grained MAR247 alloy supported by full-field ESPI measurements
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Hydrogen induced degradation of structural steel exposed to the technical liquid hydrocarbons
PublicationBadano degradacje stali 26H2MF w mieszaninach węglowodorów. Badania były prowadzone pod stałym obciążeniem i przy małej prędkości 10-6s-1
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Theoretical and experimental assessment of parameters for the non-linear viscoelastic model of structural pounding
PublicationZjawisko zderzeń pomiędzy sąsiednimi konstrukcjami budowlanymi podczas trzęsień ziemi jest w ostatnim czasie intensywnie badane z wykorzystaniem różnych modeli numerycznych siły zderzenia w czasie kontaktu. Wyniki badań eksperymentalnych pokazują, iż nieliniowy model lepko-sprężysty jest najdokładniejszy wśród modeli stosowanych do analizy. Model ten zdefiniowany jest poprzez dwa parametry: liczbę tłumienia zderzenia oraz parametr...
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Turbulent heat transfer in thin liquid films at low and high heat fluxes
PublicationW pracy przedstawiono rozważania turbulentnej wymiany ciepła w cienkich filmach cieczowych powstałych w wyniku uderzenia strugi przy małych i dużych strumieniach ciepła. W ostatnim przypadku może dojść do wrzenia filmu cieczowego. Oba zjawiska zamodelowano i uzyskano odpowiednie rozkłady temperatury i pedkosci.
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Elastic-plastic properties of metal matrix composites: Validation of mean-field approaches
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The use of response surface methodology for reliability estimation of composite engineering structures
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Representative volume element in 2D for disks and in 3D for balls
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Neuro-wavelet damage detection technique in beam, plate and shell structures with experimental validation
PublicationNiniejsza praca poświęcona jest technice diagnostyki konstrukcji bazującej na transfor-macie falkowej oraz sztucznych sieciach neuronowych (tzw. system neuro-wavelet). Zastosowanie analizy falkowej pozwala na lokalizację uszkodzeń wymagającą mini-malnej ilości danych wejściowych. W tym celu niezbędna jest tylko odpowiedź kon-strukcji pomierzona w wielu punktach. Poprawę efektywności lokalizacji zniszczeń uzyskano poprzez użycie...
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Modeling of the fascia-mesh system and sensitivity analysis of a junction force after a laparoscopic ventral hernia repair
PublicationW pracy rozpatrywano prosty model cięgnowy układu powięż-siatka do oszacowania siły połączenia siatki z powięzią po operacji laparoskopowej przepukliny brzusznej. Cięgno obciążone jest ciśnieniem wewnątrz brzusznym, symulującym kaszel, oraz przemieszczeniami jego końców wywołanymi skłonami pacjenta. Wpływ poszczególnych parametrów cięgna na siłę połączenia określono za pomocą analizy wrażliwości. Sformułowano pewne wnioski ważne...
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Damage detection in beams using wavelet transform on higher vibration modes
PublicationNiniejsza praca poświęcona jest technice diagnostyki konstrukcji bazującej na transformacie falkowej. Badany obiekt to belka wspornikowa z uszkodzeniami w formie nacięcia o głębokości 20%, 10% oraz 5% wysokości belki. Pomiary postaci drgań wykonano za pomocą nowoczesnego wibrometru laserowego. Celem pracy jest przedstawienie eksperymentalnych i numerycznych analiz wpływu wyższych postaci drgań na efektywność wykrywania uszkodzeń...
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Process zone in the Single Cantilever Beam under transverse loading. - Part I: Theoretical analysis
PublicationSingle Cantilever Beam (SCB) specimen loaded with a transverse force parallel to the crack front is proposed for the analysis of crack propagation phenomena under mixed mode conditions. The stress redistribution in the adhesive layer in the vicinity of the crack front so as the beam deformation are estimated using a Timoshenko beam on elastic foundation model. This model emphasizes the Mode II contribution due to flexural beam...
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Identification i simulation of initial geometric imperfection of steel cylindrical tanks
PublicationPrzedstawiono stochastyczną analizę stalowych zbiorników walcowych ze wstępnymi imperfekcjami geometrycznymi. Wykorzystano pomierzone odchyłki rzeczywistych zbiorników. Imperfekcje opisano za pomocą nienorodnych pól losowych. Wygenerowano realizacje odpowiadające pomierzonym imperfekcjom a także imperfekcjom ekstremalnym. Wykonano obliczeniach geometrycznie i materiałowo nieliniowe zbiornika z imperfekcjami. Wykazano, że imperfekcje...
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Effect of printing direction on fatigue response and damage development in additive manufactured Haynes 282 nickel superalloy
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Identification of the damage mechanism in orthopaedic implant. Case study including the biomechanical analysis
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On the Buckling Response of Axially Pressurized Nanotubes Based on a Novel Nonlocal Beam Theory
PublicationIn the present study, the buckling analysis of single-walled carbon nanotubes (SWCNT) on the basis of a new refined beam theory is analyzed. The SWCNT is modeled as an elastic beam subjected to unidirectional compressive loads. To achieve this aim, the new proposed beam theory has only one unknown variable which leads to one equation similar to Euler beam theory and is also free from any shear correction factors. The equilibrium...
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Buckling Analysis of a Micro Composite Plate with Nano Coating Based on the Modified Couple Stress Theory
PublicationThe present study investigates the buckling of a thick sandwich plate under the biaxial non-uniform compression using the modified couple stress theory with various boundary conditions. For this purpose, the top and bottom faces are orthotropic graphene sheets and for the central core the isotropic soft materials are investigated. The simplified first order shear deformation theory (S-FSDT) is employed and the governing differential...
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Differential Quadrature Method for Dynamic Buckling of Graphene Sheet Coupled by a Viscoelastic Medium Using Neperian Frequency Based on Nonlocal Elasticity Theory
PublicationIn the present study, the dynamic buckling of the graphene sheet coupled by a viscoelastic matrix was studied. In light of the simplicity of Eringen's non-local continuum theory to considering the nanoscale influences, this theory was employed. Equations of motion and boundary conditions were obtained using Mindlin plate theory by taking nonlinear strains of von Kármán and Hamilton's principle into account. On the other hand, a...
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METHOD FOR SHIP'S ROLLING PERIOD PREDICTION WITH REGARD TO NON-LINEARITY OF GZ CURVE
PublicationThe paper deals with the problem of prediction of the rolling period. A special emphasis is put on the practical application of the new method for rolling period prediction with regard to non-linearity of the GZ curve. The one degree-of-freedom rolling equation is applied with using the non-linear stiffness moment and linear damping moment formulas. A number of ships are considered to research the discrepancies between the pending...
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The use of a two-phase Monte Carlo material model to reflect the dispersion of asphalt concrete fracture parameters
PublicationThe work covers comprehensive laboratory tests of semi-circular bending (SCB) of asphalt concrete samples. The results of two test series, including four and 32 SCB specimens, indicate a substantial scatter of force–deflection (F-d) histories. The numerical analysis is aimed to reflect the maximum breaking load and fracture energy of the samples, pointing out their random character. The original simulation-based fictitious Monte...
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LINEAR CHARACTERISTICS OF THE SLOSHING PHENOMENON FOR THE PURPOSE OF ON-BOARD SHIP'S STABILITY ASSESSMENT
PublicationThe paper presents results of experimental research and numerical simulations of the sloshing phenomenon. The research was focused on computation of the heeling moment affecting stability of a vessel. The proposed linearisation enables application of the results to the assessment of the ship's stability. The dependence of the heeling moment upon localisation of a tank in the ship's hull is analysed. The heeling moment obtained...
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The energy approach to fatigue crack growth of S355 steel welded specimens subjected to bending
PublicationThe study presents the results of the research on the rate of fatigue crack growth subjected to bending in the ferritic-pearlitic structure. The studies were carried out at a constant amplitude of the moment and at various values of the load ratios R and at the operating frequency of the machine of 28.4 Hz. Flat specimens made of S355 steel and with fillet welds and with double-sided blunt external notches as well as concave...
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Determination of Mechanical Properties of P91 Steel by Means of Magnetic Barkhausen Emission
PublicationIn this work, an attempt at determination of mechanical properties by means of a method based on magnetic Barkhausen emission measurements was proposed. The specimens made of P91 steel were subjected to creep or plastic flow which were interrupted after a range of selected time periods in order to achieve specimens with an increasing level of strain. Subsequently, measurements of magnetic Barkhausen emission were carried out, and...
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Characteristics of orthopaedic implants damage and mechanisms of its initiation
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Polyester sail technical woven fabric behaviour under uniaxial and biaxial tensile tests
PublicationThe paper is focused on the identification of mechanical properties of a sail technical woven fabric (yacht sailcloth polyester) style 480 AP with MTO (Medium Tempered Optimized) finish. The non-linear elastic behaviour of the fabric applied for sails is investigated under uniaxial and biaxial tensile tests. Comparison of non-linear elastic parameters with others polyester coated fabrics is made. This paper is intended to be an...
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On the crack front curvature in bonded joints
PublicationStandard tests of adhesively bonded specimens are likely to produce heterogeneous stress distribution along the crack front and its vicinity. High separation rate mode I dominated fracture test is performed.Observation of post mortem fractured surfaces with an optical microscope reveals characteristic features of mixed mode I/III fracture near the sides of the specimen but not in the middle. At first, finite elements calculations...
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Mitigation of the Flow Maldistribution in Minichannel and Minigap Heat Exchangers by Introducing Threshold in the Manifolds
PublicationIn the present paper, a detailed numerical investigation has been carried out to analyze the flow maldistribution in 50 parallel rectangular cross-section (1 mm depth and 1 mm width) minichannels and minigap section (1 mm depth and 99 mm width) with rectangular/trapezoidal manifolds in Z-type flow configuration. The author carried out numerical investigation with various mass flowrates, namely 0.05 kg/s, 0.1 kg/s and 0.2 kg/s which...
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A PRELIMINARY STUDY ON THE OPTIMAL CHOICE OF AN IMPLANT AND ITS ORIENTATION IN VENTRAL HERNIA REPAIR
PublicationThis paper addresses the problem of ventral hernia repair. The main goals are to find an optimal surgical mesh for hernia repair and to define its optimal orientation in the abdominal wall to minimise the maximum force at the tissue-implant juncture. The optimal mesh is chosen from a set of orthotropic meshes with different stiffness ratios for typical hernia placement in the abdominal area. The implant is subjected to an anisotropic...
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Flexural buckling and post-buckling of columns made of aluminium alloy
PublicationThe paper concerns flexural buckling and initial post-buckling of axially compressed columns made of aluminium alloy described by the Ramberg-Osgood relationship. The non-linear differential equation of the problem is derived using the stationary total energy principle and the assumptions of classical beam theory within a finite range. The approximate analytical solution of the equation leading to the buckling loads and initial...
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Development and test of fex, a fingers extending exoskeleton for rehabilitation and regaining mobility
PublicationThis paper presents the design process of an exoskeleton for executing human fingers' extension movement for the rehabilitation procedures and as an active orthosis purposes, together with its first clinical usability tests of a robotic exoskeleton. Furthermore, the Fingers Extending eXoskeleton (FEX) is a serial, under-actuated mechanism capable of executing fingers' extension. FEX is based on the state-of-art FingerSpine serial...
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On the plastic buckling of curved carbon nanotubes
PublicationThis research, for the first time, predicts theoretically static stability response of a curved carbon nanotube (CCNT) under an elastoplastic behavior with several boundary conditions. The CCNT is exposed to axial compressive loads. The equilibrium equations are extracted regarding the Euler–Bernoulli displacement field by means of the principle of minimizing total potential energy. The elastoplastic stress-strain is concerned...
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Implementation of Hermite-Ritz method and Navier’s Technique for Vibration of Functionally Graded Porous Nanobeam Embedded in Winkler-Pasternak Elastic Foundation Using bi-Helmholtz type of nonlocal elasticity
PublicationPresent study is devoted to investigating the vibration characteristics of Functionally Graded (FG) porous nanobeam embedded in an elastic substrate of Winkler-Pasternak type. Classical beam theory (CBT) or Euler-Bernoulli beam theory (EBT) has been incorporated to address the displacement of the FG nanobeam. Bi-Helmholtz type of nonlocal elasticity is being used to capture the small scale effect of the FG nanobeam. Further, the...
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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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Contact with coupled adhesion and friction: Computational framework, applications, and new insights
PublicationContact involving soft materials often combines dry adhesion, sliding friction, and large deformations. At the local level, these three aspects are rarely captured simultaneously, but included in the theoretical models by Mergel et al., (2019). We here develop a corresponding finite element framework that captures 3D finite-strain contact of two deformable bodies. This framework is suitable to investigate sliding friction even...
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Effects of Xanthan Gum Biopolymer on the Permeability, Odometer, Unconfined Compressive and Triaxial Shear Behavior of a Sand
PublicationBiopolymers, which are microbially induced polymers, can be used as an alternative material to improve engineering performance of soils. In this paper, a laboratory study of 0.075-1.0 mm size sand and biopolymer (i.e., xanthan gum) mixtures with various mix ratios (0%, 0.5%, 1.0%, and 1.5%) was performed. The materials, specimen preparation, and test methods are described, as are the results of a suite of permeability, odometer, unconfined...
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Enhanced energy conversion as a result of fluid-solid interaction in micro- and nanoscale
PublicationIt is known that nano- and micromechanics require new approaches to right describing of surface-like phenomena which lead to an enhanced energy conversion. In this work, a general form of surface forces that consist of a contribution from both the friction and mobility components has been extended to collect the effects of bulk and surface motion of a fluid. Quite similar impact can be observed for a solid-fluid mixture, where...
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Channel Blockage and Flow Maldistribution during Unsteady Flow in a Model Microchannel Plate heat Exchanger
PublicationThis paper describes the problem of channel blockage as a result of flow maldistribution between the channels of a model mini channel plate heat exchanger consisting of one pass on each leg. Each leg of the heat exchanger contains 51 parallel and rectangular minichannels of four hydraulic diameters namely 461 μm, 571 μm, 750 μm and 823 μm. In addition, a more complex geometry has been investigated where for the sake of breaking...
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Electrochemical analysis of the passive layer cracking process on A95052 aluminium alloy performed by means of DC and AC techniques
PublicationPraca dotyczy porównania zastosowania technik stało- i zmiennoprądowych do badania pękania warstwy pasywnej na różnych stopach aluminum podczas testów rozciągania mechanicznego w warunkach polaryzacji anodowej.
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The method of detection of electromagnetic fields in ground
PublicationW prezentowanej metodzie, detekcja pola polega na pomiarach i analizie zmian rozkładu potencjału. Różnice potencjałów są mierzone jako napięcie pomiędzy elektrodami umieszczonymi w różnych pozycjach na powierzchni ziemi. Analiza tych napięć przy pomocy krótkoczasowej transformaty Fouriera STFT umożliwia wyznaczenie zmian spektralnej gęstości mocy sygnału w funkcji czasu. Ten rodzaj łącznej analizy czasowo-częstotliwościowej daje...
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Comparison of corrosion resistance of al-alloys by means of dynamic electrochemical impedance spectroscopy
PublicationPrzeprowadzono badania metodą dynamicznej elektrochemicznej spektroskopii impedancyjne stopów 1100 i 5162. Zaproponowano zastępcze modele elektryczne opisujące zachowanie się stopów w warunkach ekspozycji w roztworach zawierających wysokie stężenie jonów chlorkowych. Wyznaczono zmiany podstawowych parametrów elektrycznych układów zastępczych od potencjału. Stwierdzono wyższą podatność na korozję stopu 5162 w porównaniu ze stopem...
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Application of higher order spectra in harmonic analysis of corrosion process
PublicationZjawiska nieliniowe są niezwykle często spotykane w praktyce badań elektrochemicznych i korozyjnych. Typowym przykładem są procesy elektrodowe kontrolowane szybkością przeniesienia ładunku. Często stosowanym w takich przypadkach podejściem jest aproksymacja fragmentu krzywej prąd-napięcie za pomocą charakterystyki liniowej. W niniejszej pracy autorzy prezentują możliwość wykorzystania pomiarów składowych harmonicznych do oceny...
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Accelerated degradation of organic coatings due to cyclic mechanical stress
PublicationPotrzeba okresowej renowacji wymalowań na obiektach technicznych wynika z naturalnej degradacji powłok ochronnych wskutek oddziaływania czynników obecnych w miejscu eksploatacji. W niniejszej pracy opisano synergiczny wpływ dwóch z nich - promieniowana ultrafioletowego i cyklicznych naprężeń mechanicznych - na trwałość komercyjnie stosowanego zestawu powłokowego przeznaczonego do ochrony konstrukcji mostowych.
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Application of the dynamic electrochemical impedance spectroscopy to investigation of spontaneous electrochemical oscillations
PublicationPrzedstawione zostały wyniki impedancyjne uzyskane podczas oscylacji prądowych miedzi w kwaśnym środowisku zawierającym jony chlorkowe. Kształt chwilowych widm impedancyjnych jest skorelowany z uzyskanym przebiegiem prądowym. Badany proces anodowego roztwarzania miedzi kontrolowany jest na przemian aktywacyjnie i dyfuzyjnie.
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Cavitacion erosion, influence of electrochemical corrosion on cavitation - a review
PublicationZjawisko kawitacji polega na narastaniu, a następnie zapadaniu się i implozji pęcherzy wypełnionych gazem lub parami. Zachodzi ono niemalże we wszystkich układach hydrodynamicznych np. w pompach, zaworach, na śrubach okrętowych, turbinach, hydropłatach itp. na skutek lokalnej, gwałtownej zmiany ciśnienia. W większości przypadków jest to zjawisko niepożądane, ponieważ siły generowane podczas implozji pęcherzy kawitacyjnych są tak...
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Using impedance spectroscopy to characterize and monitor protection aspects of organic coating systems on metal
PublicationOrganiczne powłoki ochronne stosowane są powszechnie do ochrony konstrukcji metalowych przed korozją i zużyciem mechanicznym. W pracy zaproponowano nowy typ sensora impedancyjnego, który może być zastosowany do ciągłej oceny właściwości barierowych i adhezyjnych systemów powłokowych w warunkach terenowych w sposób nieniszczący, bez konieczności stosowania naczyń z elektrolitem. Przedstawiono koncepcję czujnika oraz przykładowe...