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PL
Przedstawiono i przedyskutowano wyniki badań popożarowej wytrzymałości konstrukcyjnej stali S355J2+N, niskowęglowej, o ferrytyczno-perlitycznej strukturze wewnętrznej. Wnioskowanie oparto na statycznej próbie rozciągania, prowadzonej na próbkach wystudzonych po ich uprzedniej ekspozycji na oddziaływanie temperatury pożarowej. Rozważono różny czas trwania incydentu pożarowego, różny poziom temperatury wygrzewania materiału i różny sposób jego studzenia. Oddziaływanie pożaru symulowano w scenariuszu badania izotermicznego.
EN
The results of post-fire strength tests performed for samples made of S355J2+N low-carbon structural steel, with ferritic-pearlitic microstructure, have been presented and widely discussed. The conclusion was based on the static tensile tests, carried out on samples cooled down after their prior exposure to fire temperature. Different duration of the fire incidents as well as various temperature levels of the material heating and also differentiated ways of its cooling down after the fire exposure were considered. The fire impact was simulated in an isothermal, steady-state heating regime.
PL
Celem pracy jest poznanie możliwości i uwarunkowań stosowania modeli wykonanych w technologii druku 3D do badań dynamicznych. Zaprezentowano metodę i wyniki badań określających parametry fizykomechaniczne polimeru PLA-IMPACT drukowanego z różnymi kątami rastrowania. Badania wykazały, że wartość modułu sprężystości polimeru nie zależy od kąta rastrowania, natomiast na granicę plastyczności ma wpływ kierunek laminacji, co wpływa w istotny sposób na realizację modeli obiektów do badań dynamicznych.
EN
The aim of the work is to identify the possibilities and conditions for the use of models made in 3D printing technology for dynamic experiments. The methodology and results of tests determining the physical and mechanical parameters of the PLA-IMPACT polymer printed with different screening angles are presented. The research showed that the value of the polymer modulus of elasticity does not depend on the rastering angle, while the yield point depends on the direction of lamination, which is of key importance in the implementation of models of objects for dynamic tests.
EN
The study of constitutive model is of great significance to engineering safety evaluation and geological disaster prevention. In this paper, rock materials were regarded as a composite geological material composed of voids and rock matrix, and then a piecewise constitutive model bounded by the yield point was proposed. It can reflect the complete stress–strain curves of rocks, including the compaction stage, the elastic stage, the plastic yield stage and the post-peak stage. Primarily, an objective method to determine the yield point based on the stress difference was proposed. For the rock deformation before yielding, the relationship between the strain of rock materials and the strains of voids and rock matrix was analyzed to establish the corresponding constitutive model. Subsequently, based on the modified Weibull distribution, a damage statistical constitutive model of rocks was established to describe the nonlinear deformation after the yield point. Meanwhile, the determining method of model parameters was given. Finally, the uniaxial and triaxial compression test data of different types of rocks were used to verify the proposed model. The results indicate that the model curves are in good agreement with the experimental results. Hence, it is feasible and reasonable to divide the macroscopic strain of rocks into the strains of voids and rock matrix. Additionally, there is a power function attenuation relationship between the deformation ratio of voids to rock matrix and the axial stress.
PL
W artykule omówiono parametry wytrzymałościowe pasów stalowych stosowanych w dźwigarach o falistym środniku na podstawie badań, przeprowadzonych na losowo pobranych próbkach z dwudziestu dźwigarów. Pasy dźwigarów miały grubość 15 mm oraz 20 mm. W wyniku badań oszacowano współczynniki częściowe granicy plastyczności γm oraz współczynniki zmienności VRe. Pokazano uzyskane rozkłady normalne granicy plastyczności. Uzyskane wyniki odniesiono do dostępnych badań blach płaskich i pokazano poziom bezpieczeństwa obliczeń nośności przy zginaniu wynikający ze stosowanych współczynników częściowych granicy plastyczności.
EN
The study presents parameters of strength properties of flanges used in corrugated web girders obtained on the basis of tests. The subject tests were carried out on randomly taken samples from twenty investigated corrugated web girders. The girder flanges were 15 mm and 20 mm thick. As a result of the tests, partial yield factors γm and coefficients of variation VRe were estimated. The normal distribution of yield strength obtained are shown. The obtained results were referred to the available flat sheet tests. Based on the conducted tests, the safety level of bending load calculations resulting from the applied partial factors of the yield strength was shown.
5
Content available remote Stale wysokiej wytrzymałości w konstrukcjach budowlanych
PL
Obecnie normy pozwalają na stosowanie w budownictwie stali wysokiej wytrzymałości o granicy plastyczności do 700 MPa. Efektywne kształtowanie elementów konstrukcyjnych ze stali wysokiej wytrzymałości umożliwia zmniejszenie masy konstrukcji, redukcję gabarytów przekrojów i grubości ich ścianek. W artykule omówiono wybrane aspekty stosowania stali wysokiej wytrzymałości i wskazano zagadnienia istotne z punktu widzenia racjonalnego kształtowania konstrukcji z tego typu stali.
EN
The current standard regulations allow for the use of high-strength steel with a yield strength of 700 mPa in construction. Effective shaping of structural elements from high-strength steel allows for reducing the structure weight, cross-section dimensions and their wall thickness. The article discusses selected aspects of using high-strength steel as well as emphasizes the issues that are important from the point of view of well-balanced shaping of structures from this type of steel.
EN
The series of experiments was performed on commercial polymeric composite material MultimetalStahl 1018. Strength tests were performed to determine the yield point of the material. The composite had the highest hardness at a temperature of 20°C. Hardness and microhardness were determined in further experiments. The adhesiveness of the material to metal surfaces and impact strength were also analyzed. The scanning electron microscopy and X-ray microanalysis methods were used for analyzing the microstructure of the material. Chemical composition of selected areas was analyzed, which allowed for a preliminary identification of metallic elements content in the composite. The microstructure of composite is highly non-homogeneous and particular phases are highly elongated and angular. The analyzed phase was enriched with silicon, aluminium, magnesium, iron and vanadium other phases enriched with metallic elements, e.g. molybdenum, titanium, vanadium and also oxygen as well as traces of cadmium and chromium. The results were presented in the form of photos and illustrations. The results confirmed the applicability of the composite as a binder for fixing mechanical and foundry devices.
EN
The article presents a method of determining the yield point, applying calculations based on the Kolmogorov-Sinai (K-S) metric entropy model. Data used in metric entropy calculations was obtained during a static tensile test of the AW-7020 aluminium alloy. The methodology of K-S entropy calculations was presented and illustrated by a selected example from a data collection. Analyzing the results obtained, the values of an arbitrary yield point were compared for R02 selected samples with the values of the yield point obtained using the metric entropy method ReK-S.
PL
W artykule przedstawiono sposób wyznaczania granicy plastyczności wykorzystując obliczenia oparte na entropii metrycznej Kołmogorow-Sinai (K-S). Dane do obliczeń entropii metrycznej uzyskano w czasie wykonania statycznej próby rozciągania stopu aluminium AW-7020. Opisano dokładnie metodologię obliczeń entropii K-S ilustrując ją wybranym przykładem ze zbioru danych. Analizując uzyskane wyniki porównano wartości umownej granicy plastyczności R R02 wybranych próbek z wartościami granicy plastyczności uzyskanymi metodą obliczenia entropii metrycznej ReK-S.
EN
The present study investigates the combined effects of varying viscosity and heat transfer on a Casson fluid through an inclined porous axisymmetric tube in the presence of slip effects. The modeled governing equations are solved analytically by considering the long wavelength and small Reynolds number approximations. The numerical integration is employed to obtain pressure rise and frictional force. A parametric analysis has been presented to study the effects of the Darcy number, angle of inclination, varying viscosity, velocity slip, thermal slip, yield stress, amplitude ratio, Prandtl number and Eckert number on the pressure rise, pressure gradient, streamlines, frictional force and temperature. The study reveals that an increase in the angle of inclination and viscosity parameter has a proportional increase in the pressure rise. Also, an increase in the porosity causes a significant reduction in the pressure rise.
EN
Purpose: of this paper is to prepare a nano magnetic fluids with nano additives to have the combined characteristics of high yield stress and better magnetic properties for smart vehicles. This study focuses on increasing the sedimentation time of the fluid using suitable nano additive nickel along with graphene as fillers. Design/methodology/approach: Magnetic nano sized nickel particle based electromagneto-rheological fluid was prepared and graphene nanoparticle with thickness less than 10nm was introduced as an additive to reduce its sedimentation. This added plate like graphene acts as filler which seals the interfaces of nickel particles and thereby it improves the resistance to sedimentation. Triton X 100 was added as the surfactant for the fluid to reduce the agglomeration of the particles. Findings: Morphology of pure nickel and graphene were examined using scanning electron microscopy (SEM) images. Research limitations/implications: The important limitations is that freely dispersed micron sized iron particles could settle over a period of time, in the form of cakes at the bottommost, and it is tedious to recuperate as dispersed phase. In this investigation, nano sized nickel particles were used as additive to reduce the sedimentation of micron sized iron particles so that, the mixture is homogeneous for extended period of time. In future, addition of different types composite additives in the magnetorheological fluid could be made for the better sedimentation control. Practical implications: The sedimentation problem is one of the major drawback in the smart fluids, which can be eliminated by adding nano particles. For conventional fluid, the complete sedimentation will occur in 2 hours while the improved nano magnetic fluid with additive has good resistance to settle the micron sized iron particle up to 10 hours. Originality/value: To prepare a low cost magnetorheological fluid with nano additives like nickel particles along with fillers as graphene nano particles. With this addition of nickel and inclusion of graphene, the sedimentation problem in magnetorheological fluids is significantly reduced. This magnetorheological fluids can be used in brakes and dampers of automobiles.
EN
The paper presents the results of rheological research, conducted to examine how the properties and composition of cement affects the yield stress and plastic viscosity of Portland limestone cements. Portland limestone cements used in the research were obtained by mixing four Portland cements of various chemical and phase compositions with two limestones of different origin, in an amount of 6, 10, 20 and 30% of cement mass. The yield stress and plastic viscosity were determined using the Viskomat NT rheometer, after 5 and 60 minutes from combining the constituents. Obtained results indicate a significant effect of the C3A content in cement on the rheological properties of mortars, mainly yield stress. The specific surface area of the tested cements has a lesser effect on the rheological properties of mortars with Portland limestone cements.
EN
Knowledge of the characteristics describing the technological properties of the material is the basis for correct numerical simulation and the design of new technological processes or the modernization of existing ones. For each technological process of plastic forming, a set of features should be defined that correctly describe the susceptibility of the material to its shaping in a given process. The paper presents the results of rheological tests of 6xxx series Al alloy, obtained for deformation parameters corresponding to the process of the extrusion of large-size profiles. The effect of deformation conditions on changes in yield stress was determined. Next, the true values of the mathematical model coefficients describing the rheological properties of the tested material were determined using the inverse method, which is the basis for conducting numerical tests.
PL
Dobra znajomość charakterystyk opisujących własności technologiczne materiału jest podstawą do prawidłowego przeprowadzenia symulacji numerycznych oraz projektowania nowych bądź modernizacji istniejących procesów technologicznych. Dla każdego procesu technologicznego przeróbki plastycznej można określić zestaw cech, które dobrze opisują podatność materiału do jego kształtowania w danym procesie. W pracy przedstawiono wyniki badań reologicznych stopu Al serii 6xxx, uzyskane dla analizowanych parametrów odkształcenia odpowiadających parametrom procesu wyciskania profili wielkogabarytowych. Określono wpływ warunków odkształcenia na zmiany granicy plastyczności. Następnie określono wartości rzeczywiste współczynników modelu matematycznego opisującego właściwości reologiczne badanego materiału metodą odwrotną, który to model jest podstawą przeprowadzenia badań numerycznych.
EN
The paper presents the process of producing composite material by the vacuum bag method and its numerical analysis. The composite is made of three layers of two-directional combimat with a [0.90] orientation. Then it is cut at angles and subjected to a tensile test in the Laboratory of Composite Materials, Kielce University of Technology. The data obtained from the tensile test were used to construct three tubular elements that were designed in the ABAQUS program using the finite element method. The tube was treated as a thin-walled shell component, at both ends infinitely rigid rod-shaped Rigid links are formed, at the center of their intersection the point of attachment is generated. On both sides of the rigid restraint, the element is subjected to a uniform internal pressure of a 10 MPa amplitude, which would be very difficult to obtain under laboratory conditions. The conducted experiment gives very precise information about the stresses created in the composite and the behavior of both the fibers and the matrix at different layup angles.
PL
Przedstawiono proces produkcji materiału kompozytowego metodą worka próżniowego oraz jego analizę numeryczną. Kompozyt jest zbudowany z trzech warstw matotkaniny dwukierunkowej o ułożeniu [0,90]. Następnie zostaje pocięty pod kątami i poddany próbie rozciągania w laboratorium materiałów kompozytowych Politechniki Świętokrzyskiej. Dane uzyskane z próby rozciągania posłużyły do budowy trzech elementów rurowych, które zostały zaprojektowane w programie ABAQUS, wykorzystującym metodę elementów skończonych. Rura została potraktowana jako element cienkościenny typu Shell (powłokowy), na obu końcach utworzone są nieskończenie sztywne elementy prętowe Rigid links, w centralnym punkcie ich przecięcia wygenerowany zostaje punkt zamocowania. Po obustronnym sztywnym utwierdzeniu element zostaje poddany od wewnątrz równomiernemu działaniu ciśnienia o amplitudzie 10 MPa, co byłoby bardzo trudne do uzyskania w warunkach laboratoryjnych. Przeprowadzony eksperyment daje bardzo precyzyjne informacje o naprężeniach powstających w kompozycie oraz o zachowaniu się zarówno włókien, jak i matrycy w różnych kątach ułożenia.
EN
This article discusses the issue of viscoplastic deformation that usually occurs in road pavements, especially in the summer season in Poland. The evaluation of viscoplastic deformations was performed on the example of the asphalt concrete designated for the binding course layer (AC16W). Additionally, the bitumen used for manufacturing asphalt concrete samples was modified with two types of synthetic waxes widely applied in the warm mix asphalt technology. These waxes varied in molecular weight, which affected their softening point results. Before decomposition of the total strain into elastic and viscoplastic part, oscillatory tests in the linear viscoelastic region were required. The generalized Maxwell model was used to describe the behavior of asphalt concrete in the linear viscoelastic range. Using the elasto-viscoelastic correspondence principle, described by Schapery, the initial yield strength stress was evaluated. The pseudostrain variable turned out to be useful for estimating the onset of viscoplastic strains occurring in road pavement. Such engineering procedure approach could result in faster approximation of the yield strength level during the design of pavement structures. It will also allow for differentiation of mixtures in terms of their susceptibility to permanent deformation and of their sensitivity to traffic induced overloading.
PL
W artykule opisano badania elementów wzmocnionych taśmami CFRP, w których zastosowano różne gatunki stali do wykonania zbrojenia podstawowego. Stwierdzono, iż istotny wpływ na poziom obciążenia, przy którym następuje odspojenie taśmy, ma granica plastyczności zbrojenia podstawowego użytego do wykonania elementów.
EN
The article describes a research regarding elements reinforced with CFRP tapes in which different kinds of steel were used for creation of basic reinforcement. It has been found that the yield limit of basic reinforcement used for creation of these elements has a significant impact on the level of load at which tape loosening takes place.
EN
This paper focuses on the analysis of mechanical properties of organic-inorganic polymeric hybrid material Multimetall “Stahl 1080” containing metallic particles. This material is designed for the regeneration of used metallic parts made of steel, cast iron, or composite materials. This type of material provides a 100% contact with the surface of the filled material, attenuation of vibration loads during the operation under strains, as well as protection against corrosion and tribological wear. The analysis concentrated on the behaviour of the material under vibration loads at higher temperatures.
PL
W artykule zaprezentowano analizę właściwości mechanicznych materiału hybrydowego polimerowego organiczno-nieorganicznego Multimetall “Stahl 1080” zawierającego cząstki metaliczne. Materiał ten został zaprojektowany w celu regeneracji zużytych metalicznych części ze stali, żeliwa lub materiałów kompozytowych. Ten typ materiału zapewnia 100% przyleganie do powierzchni pokrywanego materiału, tłumi drgania, jak również chroni przed korozją i zużyciem tribologicznym. Analizę skoncentrowano na badaniu oddziaływania na materiał drgań w wysokich temperaturach.
16
Content available remote Geometrical Modeling of Woven Fabrics Weavability-Limit New Relationships
EN
The weavability limit and tightness for 2D and 3D woven fabrics is an important factor and depends on many geometric parameters. Based on a comprehensive review of the literature on textile fabric construction and property, and related research on fabric geometry, a study of the weavability limit and tightness relationships of 2D and 3D woven fabrics was undertaken. Experiments were conducted on a representative number of polyester and cotton woven fabrics which have been woven in our workshop, using three machines endowed with different insertion systems (rapier, projectiles and air jet). Afterwards, these woven fabrics have been analyzed in the laboratory to determine their physical and mechanical characteristics using air permeability-meter and KES-F KAWABATA Evaluation System for Fabrics. In this study, the current Booten’s weavability limit and tightness relationships based on Ashenhurst’s, Peirce’s, Love’s, Russell’s, Galuszynskl’s theory and maximum-weavability is reviewed and modified as new relationships to expand their use to general cases (2D and 3D woven fabrics, all fiber materiel, all yarns etc…). The theoretical relationships were examined and found to agree with experimental results. It was concluded that the weavability limit and tightness relationships are useful tools for weavers in predicting whether a proposed fabric construction was weavable and also in predicting and explaining their physical and mechanical properties.
PL
W artykule przeanalizowano wpływ wysokiej temperatury na wytrzymałość współcześnie stosowanej w Polsce stali zbrojeniowej. Sprawdzono, czy szacowanie cech wytrzymałościowych na bazie rekomendacji PN-EN 1992-1-2 nadal można uważać za prawidłowe. Analizę przeprowadzono na bazie wyników badań własnych wykonanych na próbkach prętów gatunku B500SP, zarówno w warunkach ustalonej, jak i nieustalonej wysokiej temperatury. Wyniki badań współczynnika redukcji wytrzymałości stali na rozciąganie (ks,θ) okazały się zgodne z wartościami oszacowanymi na podstawie wymagań Eurokodu. Nie zaobserwowano też, aby wyniki badań prętów o średnicy 10, 12 i 16 mm istotnie się od siebie różniły. Analiza wyników prowadzi do wniosku, iż model podany w PN-EN 1992-1-2 może nadal stanowić wiarygodną podstawę prognozowania zmniejszenia wytrzymałości stali zbrojeniowej w warunkach pożarowych
EN
In this paper the influence of high temperature on strength of the reinforcing steel currently used in Poland was analysed. It was investigated whether steel strength properties estimated according to EN 1992-1-2 are still valid. The analysis was based on tests performed on samples of B500SP reinforcing bars in steady and unsteady (increasing) high temperature conditions. Obtained values of the steel strength reduction factor (ks,θ) have been found to be in accordance with Eurocode. Additionally, no significant differences between result obtained for bars 10, 12 and 16 mm in diameter were observed. Obtained results show that the EN 1992-1-2 recommendations can provide an adequate prediction of steel strength reduction factor in fire conditions.
PL
Zaprezentowano algorytm wyznaczania temperatury eksponowanej ogniowo stalowej nośnej ramy portalowej, skojarzonej z aktywowaniem się w niej krytycznego mechanizmu zniszczenia plastycznego. Zaproponowano zastosowanie uogólnionego podejścia kinematycznego z wykorzystaniem identyfikacji chwilowego środka obrotu. Miarodajna temperatura jest najniższą spośród uzyskanych ze szczegółowej analizy poszczególnych kinematycznie dopuszczalnych mechanizmów zniszczenia.
EN
Calculation algorithm helpful in the specific temperature assessment for steel load-bearing portal frame exposed to fire, being associated with the activation in such a structure of critical plastic failure mechanism, is presented and discussed in detail. It is proposed to apply to do this a generalized kinematic approach using the identification of the instantaneous centre of rotation. The lowest of the values obtained from a detailed study of all kinematically admissible collapse mechanisms can be recognized to be the conclusive temperature value related to the whole considered frame.
PL
Praca zajmuje się badaniem wpływu temperatury na właściwości mechaniczne materiału kompozytowego MM "Stahl 1018". W pracy przedstawiono opis techniki wytwarzania kompozytu Stahl 1018 oraz metodykę prowadzonych badań laboratoryjnych. Analiza uzyskanych wyników na podstawie przeprowadzonych eksperymentów wykazała, że wraz ze wzrostem temperatury maleje granica plastyczności badanego materiału kompozytowego.
EN
A theoretical and practical study of the effect of temperature on the mechanical properties of the composite material MM "Stahl 1018". Describes laboratory setting in which testing will be conducted, as well as describes a method of preparation and carrying out of the experiment. Also, the analysis of the results of the experiments, which showed that with increasing temperature decreases the yield strength of the material.
EN
The plastic limit of soils was first described by Atterberg in 1911. The thread-rolling test became one of the standard tests of soil mechanics. In recent years this method has been the subject of much criticism. This paper reviews the original method of plastic limit determination as proposed by Atterberg and the fall cone methods for determining at the same time both the liquid and the plastic limits of soils. The tests were performed on 748 samples representing a wide range of soil type with different clay content ranging from 4 to 79%.
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