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EN
We present shakedown theorems applying to cyclically loaded media in which plastic flow and diffusion of guest atoms are coupled. The presented theorems are in the spirit of Melan and Koiter theorems in plasticity. They allow one to estimate the loading parameters for which elastic shakedown occurs, i.e. for which the plastic strain stabilizes to a time-independent limit. An application related to lithium-ion batteries is presented.
EN
The article proposes a new process for the production of thin wires made of copper and copper alloys. The proposed process is based on the idea of dieless drawing. The workpiece for dieless drawing is a thin wire obtained through a conventional drawing method. The proposed technology is based on a multi-pass process. The deformation parameters in each pass are determined on the basis of an analysis of the dependence of the flow stress of the material on the strain, strain rate and temperature. For this purpose, plastometric tests of a copper and CuZn37 alloy were performed. In order to determine technological plasticity and roughness propagation during dieless drawing, physical and numerical modelling of this process were performed. The obtained data were used in the practical implementation of the dieless drawing technology.
PL
Artykuł poświęcono nowemu procesowi produkcji cienkich drutów z miedzi i jej stopów. Zaproponowany proces jest oparty o idee ciągnienia bezmatrycowego. Wsadem do ciągnienia bezmatrycowego jest cienki drut, wyprodukowany za pomocą metody konwencjonalnego ciągnienia. Proponowana technologia jest oparta na wieloprzepustowym procesie. Parametry odkształcenia w każdym przepuście są wyznaczane na podstawie analizy zależności naprężenia uplastyczniającego od odkształcenia, prędkości odkształcenia i temperatury. W tym celu przeprowadzono badania plastometryczne miedzi i stopu CuZn37. Celem wyznaczenia technologicznej plastyczności oraz propagacji chropowatości powierzchni drutu w trakcie ciągnienia bezmatrycowego wykonano fizyczne i numeryczne modelowanie procesu. Otrzymane dane wykorzystano podczas praktycznej implementacji procesu ciągnienia bezmatrycowego.
EN
The paper is focused on study of plasticity and formability of dual phase steel DP 450, which is used in automotive industry. The paper shows results from tensile test for plasticity determination and also results of technological tests for complex evaluation of formability. These consisted from Erichsen cup test, Fukui test and Schmidt test. The paper shows also results of microhardness measurement.
PL
Artykuł koncentruje się na badaniu plastyczności i odkształcalności stali dwufazowej DP 450, która jest stosowana w przemyśle motoryzacyjnym. W pracy przedstawiono wyniki prób rozciągania dla określenia plastyczności, a także wyniki testów technologicznych dla kompleksowej oceny odkształcalności. Składały się one z testu pucharowego Erichsena, testu Fukui i testu Schmidta. W pracy przedstawiono również wyniki pomiaru mikrotwardości.
EN
Natural occurring gypsum is a soft mineral consists of hydrated calcium sulphate, mainly used in cement industry. On the other hand, red gypsum (RG) is a waste generated from a sulphate process of ilmenite ore to acquire titanium dioxide. Due to the gypsum content in both materials are similar, it is expected that both gypsum type can be used for similar engineering applications. In this study, RG was tested and compared to pure gypsum for geoelectrical grounding applications. The geotechnical properties and plasticity characteristics were carefully measured and tested. In addition, X-ray fluorescence (XRF) was employed to study the chemical constituents of the materials. Test results showed that, the geotechnical properties of RG is different to that of white gypsum. The plasticity index (PI) of RG was 239.6% greater due to the presence of Fe ions. Surprisingly, the electrical resistivity of both material were found to be similar. It was also noted that, although the plasticity of pure gypsum is high, the plasticity of pure gypsum was found to be short lived primarily due to instantaneous exothermic reaction between water and semihydrated gypsum. The change in the plasticity also affected the resistivity as gypsum hardened after short duration. Based on the geotechnical and plasticity characteristics determined, RG was found to be a better as grounding material as compared to gypsum.
EN
This investigation focussed on the plasticity and swell-shrink behaviour of an expansive soil that was stabilized using electro kinetic stabilization (EKS) techniques with cationic fluids for enhancement of stabilization. 0.25 M solutions of calcium hydroxide and calcium chloride were used as cationic fluids. An electro kinetic (EK) cell of dimensions 500 mm x 150 mm x 160 mm with inert graphite electrodes of size 140 mm x 160 mm x 5 mm was adopted for the stabilization process, carried out at an applied voltage of 40 V over a period of 6 hours. After the duration of the test, stabilized soil sample was subjected to Atterberg limits and free swell tests to determine its plasticity and swell-shrink characteristics. The results of the investigation found that both fluids were capable of reducing the plasticity and swell-shrink behaviour of the soil with different levels of effectiveness.
PL
W badaniach skupiono się na plastyczności i kurczeniu się gleby, która została ustabilizowana za pomocą technik stabilizacji elektrokinetycznej (EKS) z płynami kationowymi. Jako płyny kationowe stosowano 0,25 M roztwory wodorotlenku wapnia i chlorku wapnia. Do procesu stabilizacji przyjęto ogniwo elektrokinetyczne (EK) o wymiarach 500 mm x 150 mm x 160 mm z obojętnymi elektrodami grafitowymi o wymiarach 140 mm x 160 mm x 5 mm, przy zastosowaniu napięcia 40 V przez okres 6 godzin. Po zakończeniu testu stabilizowaną próbkę gleby poddano testom Atterberga i badaniom swobodnego spęcznienia w celu określenia jego plastyczności i charakterystyki kurczenia się. Wyniki badania wykazały, że oba płyny były w stanie zmniejszyć plastyczność i kurczenie się gleby przy różnych poziomach skuteczności.
EN
Fuzzy logic determination of the material hardening parameters based on the Heyer’s method was applied in this research. As the fuzzy input variables, the length of two measuring bases and the maximum force registered in the Heyer's test were used. Firstly, the numerical experiment (the simulation of the fuzzification of the input data) with the assumed disturbance of input variables was performed. Next, on the basis of experimental investigations (eleven samples made from the same material), the membership functions associated with the input data were created. After that, the fuzzy analysis was examined. Fuzzy material hardening constants obtained by means of the α-level optimization and the extension principle methods were compared. Discrete values of the hardening data are found in the defuzzification process, by application of the mass center method.
7
Content available remote Role of dilatancy angle in plasticity-based models of concrete
EN
The so-called concrete damaged plasticity (CDP) model is frequently employed by ABAQUS users to simulate the behaviour of concrete. One important aspect of the model, namely the representation of material dilatancy, is evaluated in the paper. The role of the dilatancy angle in pressure-dependent plasticity models is reviewed. The plastic potential adopted in the CDP model is discussed. It is shown that the definitions of the angle in the CDP model and in the Burzynski–Drucker–Prager (BDP) plasticity model for a continuum can lead to different angle magnitudes. Two tests on concrete configurations are simulated to illustrate how strongly the angle influences the results: the Kupfer benchmark of a panel under uniaxial or biaxial compression and the punching shear response in a slab-column connection. The importance of viscosity in cracking simulation is thereby mentioned, the results are compared with experimental ones and mesh sensitivity is verified. Recommendations for analysis of concrete mechanics problems are formulated.
PL
W pracy analizowano kierunkowość własności i struktury taśm cienkich wytworzonych ze stali X2NiMoTi19-4-1 i X1CrNiMoTi11-10-1, tj. odpowiednio bezkobaltowej stali typu maraging i stali odpornej na korozję umacnianej wydzieleniowo (SONK-UW). Do oceny anizotropii struktury stali i rozkładu wielkości ziarna wykorzystano mikroskop skaningowy z detektorem EBSD. Badane stale – pomimo całkowicie różnych składów chemicznych – mają bardzo zbliżone własności mechaniczne w stanie przesyconym oraz po starzeniu.
EN
The paper analyses the directionality of the tensile properties and microstructure of cold-rolled thin strips made of the X1NiMoTi19-4-1 Co-free maraging steel and the X1CrNiMoTi11-10-1 precipitation hardening stainless steel. The scanning electron microscopy EBSD technique was used to assess microstructural anisotropy and the grain size distribution. It was demonstrated that both steels – despite entirely different chemical compositions – exhibit very similar mechanical properties in the cold-rolled, annealed state and after age hardening.
EN
One hundred and five alpine accentors Prunella collaris (Scopoli, 1786) and ninety four dunnocks Prunella modularis (Linnaeus, 1758) were captured in the West Carpathian Mountains of Slovakia in order to compare the morphology of their Ischnoceran parasites Philopterus emiliae Balát 1985 and Philopterus modularis (Denny, 1842), respectively. In the case of both host species, the largest bodied lice occurred in winter, before the beginning of the host breeding season. Lice collected during the host breeding season were smaller in size than those collected in winter. Lice collected in the autumn, following postnuptial molt were even smaller in size. The largest lice were found on the bodies of host individuals with relatively long wings. The lice Ph. emiliae also differed in shape. In winter, the relative size of the head was large, while in the autumn, the head was proportionately smaller in size, compared to other body regions. Adult lice Ph. modularis also tended to have larger heads in April than in July. Measurements of lice over an eleven year period from the same site yielded differences in shape, but not in size. This study is one of the first assessments of seasonal variation in morphology of lice.
EN
In this paper a short description is reported allowing to take into account some aspects to design structures used for automotive industries. It allows to define correctly the behaviour of a vehicle and mainly the passive structures to absorb energy during an accident or an impact. The main aspect related to the behaviour is the strain rate sensitivity coupled to the process of elastic wave propagation.
EN
Flax (Linum usitatissimum L.) is one of the promising oil crops in the north of Kazakhstan. Over the last 10 years, the total area under this crop in the region has increased fourteen-fold, since flax is a very plastic crop for steppe and dry steppe conditions, and oil seeds are in high demand in the world market. Flaxseed oil, due to the content of polyunsaturated fatty acids, occupies one of the first positions among other edible vegetable oils. Depending on the environmental conditions, the oil content of the crop may vary from 36.4% to 52.0%, while, as noted by many researchers, the change in the oil content depends on the genotypic characteristics. Therefore, the study aims to analyze the influence of the genotype and climatic conditions of cultivation on the fat biosynthesis in flax seeds in the context of the dry steppe zone of Northern Kazakhstan on dark chestnut soils of the Akmola region. Field experiments were conducted in 2015–2017 with the study of nine oil flaxseed cultivars (of mid-season varieties) sown on May 20th at the seeding rate of 7 million seeds/ha based on the traditional technology of cultivation recommended for the region. The climatic parameters were taken into account according to the meteorological service data. The fat content was determined by the extraction method using a Soxhlet apparatus, in accordance with GOST (All-Union State Standard) 10857–64, and the moisture content was determined by means of the thermogravimetric method, according to the National Standard of the Republic of Kazakhstan 2.195–2010, for the recalculation of the oil content for absolutely dry matter. It was found that the formation of oil depends on the climatic parameters and on the sum of active temperatures during the ripening period, in particular. The evaluation of plasticity and stability of the cultivars (genotypes) showed that VNIIMK 620, Lirina, Karabalyksky 7 can be considered highly valuable cultivars and Severny, Biryuza, Kazar, Ilyich – valuable cultivars in terms of the oil content for the dry steppe zone.
EN
Steels and other ferrous alloys are very well known as construction materials and still are widely used and in the near future this will not change. Duplex steels due to the two-phase construction combine high corrosion resistance and good mechanical properties. Both those parameters are at higher level than austenitic stainless steels and that why duplex steels are irreplaceable material in many fields like the petrochemical, power, pulp and paper, and food industry. This multiphase microstructure generates a lot of problems which have already been repeatedly presented in many works. Among the steels and cast steels resistant to corrosion most modern and dynamically developing group are ferritic-austenitic alloys, commonly known as duplex. The chemical composition of a steel containing about 0.02% C, 26% Cr, 6.5% Ni, 3% Mo, 1.4% Mn, 0.2% N guarantees that already after casting is obtained ferritic - austenitic structure. The paper present results of the X2CrNiMoN25-7-4 duplex steel physical tests made with the Gleeble 3800 machine. The research concerns problems of the influence of primary structure on the plasticity and sigma phase formation.
PL
Stale obok innych stopów żelaza są dobrze znanymi, szeroko wykorzystywanymi materiałami konstrukcyjnymi i sytuacja taka w najbliższej przyszłości nie ulegnie zmianie. Stale dupleks dzięki swojej dwufazowej budowie cechuje wysoka odporność korozyjna oraz wysokie właściwości mechaniczne. Obydwa te parametry są na wyższym poziomie niż stali austenitycznych i dlatego stale dupleks są niezastąpionym materiałem w wielu gałęziach przemysłu jak petrochemiczny, energetyczny, papierniczy czy w produkcji żywności. Taka budowa mikrostruktury powoduje pojawienie się wielu problemów, które już w wielu pracach były szeroko omawiane. Wśród stali i staliwa odpornego na korozję najszybciej rozwijającą się grupą są stopy ferrytyczno-austenityczne znane również jako dupleks. Skład chemiczny stali zawierającej 0,02% C, 26% Cr, 6,5% Ni, 3% Mo, 1,4% Mn, 0,2% N gwarantuje uzyskanie już w stanie lanym mikrostruktury ferrytyczno-austenitycznej. W pracy przedstawiono wyniki badań fizycznych przeprowadzonych z wykorzystaniem urządzenia Gleeble 3800 na stali X2CrNiMoN25-7-4. Badania dotyczą problemów wpływu mikrostruktury pierwotnej na plastyczność oraz wydzielanie się fazy sigma.
PL
W artykule zaproponowano warunek plastyczności i wyprowadzono związany z nim potencjał dyssypacji stosując osobliwą transformację Legendre’a. Uzyskano jawną postać funkcji dyssypacji, co umożliwia dualny opis plastycznych własności materiału. Trójparametrowy warunek plastyczności umożliwia ciągłe przejście od warunku Druckera-Pragera do Hubera-Misesa przez odpowiedni dobór parametrów. Przedyskutowano kalibrację parametrów na podstawie typowych testów wytrzymałościowych. Na bazie założonego warunku plastyczności sformułowano relacje konstytutywne sprężysto-plastyczności, które mogą być stosowane do opisu własności porowatych metali i materiałów z tarciem wewnętrznym.
EN
A yield condition was proposed in this paper and associated dissipation function was derived via singular Legendre transformation. As a result, an explicit form of the dissipation function was obtained, which can be used for dual formulation of perfect plasticity model. The three-parameter yield condition enables continuous transition from the Drucker-Prager to Huber-Mises yield conditions by appropriate selection of free parameters. Calibration of the free parameters based on typical experimental tests was discussed. Based on the proposed yield function, a constitutive model of elastic-plastic material was given. The model can be used for modelling porous metals and other frictional materials.
PL
W artykule omówiono sposób formułowania relacji konstytutywnych materiałów sprężysto-plastycznych z uwzględnieniem uszkodzenia na podstawie dwóch potencjałów: potencjału energetycznego i potencjału dyssypacji. Uzyskany model materiałowy jest termodynamicznie spójny, o ile przyjęte funkcje spełniają określone warunki. Przedstawiona metoda została zilustrowana przykładem jednowymiarowym oraz przykładem relacji trójwymiarowych z wykorzystaniem warunku plastyczności Beltramiego-Michella.
EN
In the paper a thermomechanical framework for modelling elastoplastic damaged materials is presented. Basic assumptions and concepts are given, leading to formulation of constitutive equations using two potentials only: Helmholtz free energy and dissipation potential. Consecutive steps of the procedure are shown for simplified one-dimensional case, followed by three-dimensional example concerning Beltrami-Michell failure condition.
EN
In this paper, we report the complex crystallization kinetics of phase transition happening in Ti-Cu-based bulk metallic glasses (BMGs), which play significant roles in the glass formation with respect to their low reduced glass transition temperatures, Trg. The first exothermic event just occurs when annealing the BMG samples in the supercooled liquid region, leading to the Avrami exponent deviating from conventional modes affected by the residual amorphous phase. For Ti43Cu43Ni7Zr7 BMG, the plasticity can be improved by pre-annealing at a sub-Tg temperature of 623K (≈50K below Tg) for 0.5 hour, however, deteriorated by 1 hour annealing, which could be related to the change in stability of this BMG against crystallization with different pre-annealing times.
EN
The paper deals with the measurement of the residual stresses in P91 welded pipe using the blind hole drilling technique. The P91 pipe weld joints were prepared using gas tungsten arc welding process. The residual stress measurement was carried out using the strain gauge rosette that was associated with the plastic deformation of material and stress concentration effect of multi-point cutting tool. Strain gauge response was estimated experimentally using the tensile testing for the uniaxial loading while finite element analysis was performed for biaxial loading. Gas tungsten arc welds joint was prepared for conventional V-groove and narrow groove design. The corrective formulation was developed for calculating the corrected value of residual stresses from the experimentally obtained strain value. The corrected and experimental induced residual stresses values as per ASTM E837-13 were calculated for both V-groove and narrow groove design. Post weld heat treatment (PWHT) of P91 welded pipe was also conducted to study their effect on residual stresses.
18
Content available remote Cam-clay models in mechanics of granular materials
EN
The mathematical models for granular materials utilizing concept of the critical state, is reviewed. Several extensions of the critical state Modified Cam-Clay (MCC) models are reviewed, including kinematic hardening with bounding surface (BS), the general plasticity (GP) model, extension of the MCC model to include finite strain, and different variants of the pressure hardening rule, including bi-modulus extension, hypoplastic, and the hyperelastic potential extension. The associated flow rules coupled with different hardening equations are considered. In the review the main attention is paid to the case of the infinitesimal strains.
EN
In the present study, the finite element (FE) implementation of elasto-plasticity without a yield surface is discussed. For that purpose, the method of perturbing the deformation gradient tensor is employed to calculate approximate tangent moduli. The development of a user subroutine that enables one to use the proposed model within the FE program ABAQUS is covered. A number of exemplary numerical simulations is conducted in order to check the performance of this subroutine. Material parameter values determined for different materials are utilized. Finally, the presented constitutive equation is examined upon its ability to capture the shear-softening process.
EN
In the present study, a shape memory alloy (SMA) phenomenological constitutive model is proposed that is capable of describing SMA superelastic behavior and the plasticity effect. The phase transformation constitutive model, by using strain and temperature as control variables to judge the phase transformation points in order to avoid the complexity of transformation correction, incorporates plasticity described by the von Mises isotropic hardening model. Further, the proposed model is implemented into the finite element package ANSYS by the user subroutine USERMAT. The results produced by the proposed model of simulated superelastic and plasticity behavior are compared with experimental data taken from the literature.
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