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1

Method of experimental study of the force-deformation characteristics of the Belleville spring of the stop assembly of a direct-flow gate valve

Hasanov Ilman I., Guliyev Agali A., Tanriverdiyev Yusif A.

Nafta-Gaz

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2023

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R. 79, nr 11

742--748

EN

The article presents research methods and appropriate equipment for conducting experiments, as well as the analysis of the results. Studies on the hardness of the microstructure, elastic deformation and parts and samples were carried out using hardness testers, microscopes PMT-3, MIM-8 and devices for measuring the “force-strain” characteristic. The results of the study wer used to establish the dependence of the elastic properties of Belleville springs on the heat treatment modes, while also determining the microstructure and layer depth using various research methods. Every work studying the elastic properties and measurement of the static compressive force of a spring at a given strain value has been studied theoretically. Depending on the operating conditions, disc springs can be installed singly or assembled into packages, forming an elastic element working under compression. The research materials will be used in the work to improve the tightness of straight-through valves and the durability of the shut-off assembly parts. The dependence of the spring compression force and its deformation on the geometrical parameters of the disc springs has been established. Comparison of experimental and theoretical dependences has been made. It has been established that the residual deformation of the Belleville spring after captivity has a negative effect on the tightness of the shut-off valve assembly. The influence of various technological processes and modes of thermal treatment of disc springs on their elastic properties has been studied. Practical recommendations for improving the technological process of thermal treatment of Belleville springs have been proposed. The tasks of further research and implementation of the obtained results have been determined. Search work has been carried out to improve the technology of hardening processing of parts of the shut-off unit (gate and seat) of direct-flow valves. The possibility of using accelerated nitrocarburizing in a triethanolamine medium with induction heating by high-frequency currents at a temperature range of 950°С for boriding and borochroming has been established. Samples were made from standard steel grades 40, 40Kh and 38Kh2MYuA, subjected to hardening by the considered methods, and a study was made of the hardness, depth and microstructure of the hardened layer. Research in this direction should be continued in order to study the tribological characteristics (friction coefficient and wear resistance) of hardened parts. Each operation of the spring manufacturing technology has been studied, and deviations that have a significant impact on the operation of the spring and the sealing of the shut-off valve assembly have been identified.

PL

Artykuł przedstawia metody badawcze i odpowiednie wyposażenie służące do przeprowadzania eksperymentów, a także analizę wyników. Badania przyprowadzono przy użyciu testerów twardości, mikroskopów PMT-3, MIM-8 oraz urządzeń do pomiaru charakterystyki “siła-odkształcenie”. Wyniki tych badań wykorzystano do ustalenia zależności właściwości elastycznych sprężyn Belleville od parametrów obróbki cieplnej, jednocześnie określając mikrostrukturę i głębokość warstwy za pomocą różnych metod badawczych. Każdy przypadek badania właściwości elastycznych i pomiaru statycznego siłowego odkształcenia sprężyny przy danej wartości odkształcenia był analizowany teoretycznie. W zależności od warunków pracy sprężyny tarczowe mogą być montowane pojedynczo lub w pakietach, tworząc element elastyczny podlegający ściskaniu. Materiały badawcze mogą zostać wykorzystane w pracach mających na celu poprawę szczelności zasuw oraz trwałości części zespołu zamykającego. Ustalono zależność między siłą kompresji sprężyny i jej odkształceniem a parametrami geometrycznymi sprężyn tarczowych. Dokonano porównania wyników eksperymentalnych i teoretycznych. Ustalono, że szczątkowe odkształcenie sprężyny Belleville po jej zamontowaniu ma negatywny wpływ na szczelność zespołu zaworu zamykającego. Zbadano wpływ różnych procesów technologicznych i trybów obróbki cieplnej sprężyn tarczowych na ich właściwości elastyczne. Zaproponowano praktyczne zalecenia w celu poprawy procesu technologicznego obróbki cieplnej sprężyn Belleville. Określono cele dalszych badań i sposób wdrożenia uzyskanych wyników. Przeprowadzono prace badawcze w celu poprawy technologii hartowania części zespołu zamykającego (zasuwy i gniazda) zasuw klinowych. Sprawdzono możliwość zastosowania przyspieszonego azotonawęglania w środowisku trietanoloaminy z indukcyjnym ogrzewaniem prądem o wysokiej częstotliwości w zakresie temperatury 950°C w procesie borowania i borochromowania. Wykonano próbki ze standardowych gatunków stali 40, 40Kh i 38Kh2MYuA, które poddano hartowaniu przy rozważanych metodach, przeprowadzono badanie twardości, głębokości i mikrostruktury warstwy hartowanej. Badania w tym kierunku powinny być kontynuowane w celu zbadania charakterystyk tribologicznych (współczynnika tarcia i odporności na zużycie) hartowanych części. Przeanalizowano każdą fazę technologii produkcji sprężyny i zidentyfikowano odchylenia, które mają znaczący wpływ na działanie sprężyny i uszczelnienie zespołu zaworu zamykającego.

2

Novel rheological modelling of thermosets and unidirectional monotropic fibre-reinforced thermoset matrix composites

Klasztorny Marian, Nycz Daniel B.

Composites Theory and Practice

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2023

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R. 23, nr 1

3--21

EN

A refined, fully analytical rheological modelling of thermosetting polymers and unidirectional monotropic fibre-reinforced thermoset matrix (UFRT) composites is presented. New polymers and composites under normal conditions, fully relaxed from curing and post-curing stresses, are modelled. The theory includes quasi-static short-term/medium-term/long-term reversible rheological processes. Thermosets are isotropic materials exhibiting linearly viscoelastic shear strains and linearly elastic bulk strains. Fibres are monotropic (transversely isotropic) and linearly elastic materials. A generic function well reproducing the viscoelastic characteristics of thermosets and UFRT composites is a Mittag-Leffler fractional exponential function in an integral form. Coupled/uncoupled standard/inverse constitutive equations of linear rheology are formulated for thermosets and UFRT composites. The equations are mutually analytically transformable. New rheological models (coded H-R/H) for thermosets and UFRT composites are described by the smallest possible number of material constants. The thermoset is described by two independent elastic constants and three independent viscoelastic constants. The homogenized UFRT composite is described by five independent elastic constants and four independent viscoelastic constants, whereby two visco-elastic constants are common to the matrix and the composite. An improved homogenization theory of UFRT composites, based on analytical solutions of the selected tasks of the theory of linear elasticity, is formulated for monotropic fibres and positively validated experimentally. The viscoelastic constants of the thermoset are calculated analytically in an iterative loop using a long-term unidirectional tension creep experimental test. The viscoelastic constants of the UFRT composite are calculated analytically employing H-R/H shear/quasi-shear storage compliances and VECP (the viscoelastic-elastic correspondence principle) shear/quasi-shear storage compliances. The H-R/H rheological model was validated numerically for selected UFRT composites. The validation tests were performed on the enhanced reliability UFRT composites reported by Soden, Hinton, and Kaddour (Composites Science and Technology, 1998, 2002).

3

Rheological properties of elastic-visco-plastic liquid

Dadash-Zade Mirza A., Aliyev Inglab N.

Nafta-Gaz

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2022

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R. 78, nr 11

801--804

EN

A model for the motion of a compressible elastic-viscous-plastic fluid in a round pipe is proposed. The main indicators of the flow, volume flow and speed are obtained. Numerous hydrodynamic processes are associated with the properties of liquids. It is known that the mechanical and physical properties of liquids can be described by various models. Various models have been proposed that partially describe the processes of hydromechanics. The proposed model makes it possible to qualitatively describe the deformation processes that occur in various systems. To describe a closed theory of motion of a continuous medium and, in particular, between stress and strain, it is necessary to have a mechanical model. From the literature analysis it is known that there are simple models, which include elastic, viscous and plastic. At the same time, it should be noted that the mechanical model partially shows the mechanical state of the elastic body in the form of Hooke's law. Practice shows that there are more complex liquids that do not obey this law. One of these fluids is an elastic-viscousplastic fluid. In this work, a model is proposed that describes the elastic-viscous-plastic properties of liquids, which sequentially connects the elastic and viscous-plastic elements. For such a medium, the total resistance will be the sum of the stress corresponding to the elastic deformation and the stress caused by the viscous-plastic resistance. Based on the proposed model, an equation is obtained taking into account the coefficient of volumetric elastic expansion, and an equation is obtained for determining the velocity distribution over the pipe section and volume flow for a given liquid. Calculations have shown that with an increase in compressibility, the flow rate of the liquid partially increases, which in some practical cases produces a positive effect.

PL

W artykule zaprezentowano model ruchu ściśliwej cieczy sprężysto-lepkoplastycznej w rurze o przekroju okrągłym. Uzyskano główne wskaźniki przepływu, przepływu objętościowego i szybkości. Liczne procesy hydrodynamiczne są związane z właściwościami cieczy. Wiadomo, że właściwości mechaniczne i fizyczne cieczy można opisać za pomocą różnych modeli. Zaproponowano modele, które częściowo opisują procesy mechaniki cieczy. Przedstawiony model umożliwia jakościowy opis procesów odkształcenia zachodzących w różnych systemach. Model mechaniczny jest konieczny do opisania zamkniętej teorii ruchu ośrodka ciągłego, w szczególności pomiędzy naprężeniem i odkształceniem. Z analizy literatury wiadomo, że istnieją proste modele obejmujące ciecze sprężyste, lepkie i plastyczne. Należy jednocześnie zauważyć, że model mechaniczny częściowo przedstawia stan mechaniczny ciała sprężystego, wykorzystując prawo Hooke’a. Praktyka pokazuje, że istnieją ciecze bardziej złożone, niezachowujące się zgodnie z tym prawem. Jednym z takich płynów jest płyn sprężysto-lepkoplastyczny. W niniejszej pracy zaproponowano model opisujący właściwości sprężysto-lepkoplastyczne cieczy, który sekwencyjnie łączy elementy sprężyste i lepkoplastyczne. W przypadku takiego ośrodka opór całkowity jest sumą naprężenia odpowiadającego odkształceniu sprężystemu i naprężenia spowodowanego przez opór lepkoplastyczny. Na podstawie zaproponowanego modelu uzyskano równanie uwzględniające współczynnik objętościowej rozszerzalności sprężystej, a także uzyskano równanie do określenia rozkładu szybkości na przekroju rury oraz przepływu objętościowego dla danej cieczy. Obliczenia pokazały, że ze wzrostem ściśliwości szybkość przepływu cieczy częściowo wzrasta, co w pewnych praktycznych przypadkach daje pozytywny efekt.

4

Strength analysis of sandwich beams with linear elastic inner layer

Kimura Koichi

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 3

31--44

EN

A waterproof or water-resistant sandwich structure which consists of housing chassis and a gasket requires that gasket contact pressure, which depends on bolt axial force, is greater than the design minimum pressure on the entire circumference. However, it is also necessary that gasket contact pressure is smaller than the maximum permissible gasket pressure. If the maximum stress in chassis can be calculated from bolt axial force, gasket specifications and chassis stiffness, it is helpful for a design of such waterproof structures. In this study, chassis have been regarded as Bernoulli-Euler beams, and two simple numerical methods have thus been derived. Numerical results using the proposed method are sufficiently converged even in case that the number of partitions is about 10.

5

A new conservative finite difference scheme for 1D Cahn-Hilliard equation coupled with elasticity

Shimura Kazuki, Yoshikawa Shuji

Journal of Applied Analysis

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2022

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Vol. 28, nr 2

311--332

EN

In this article, we give analysis for a structure-preserving finite difference scheme to the Cahn-Hilliard system coupled with elasticity in one space dimension. In the previous article [K. Shimura and S. Yoshikawa, Error estimate for structure-preserving finite difference schemes of the one-dimensional Cahn-Hilliard system coupled with viscoelasticity, in: Regularity and Asymptotic Analysis for Critical Cases of Partial Differential Equations, RIMS Kôkyûroku Bessatsu B82, Research Institute for Mathematical Sciences (RIMS), Kyoto (2020), 159-175], we studied the system coupled with viscoelasticity, where we proposed a conservative numerical scheme for the system which inherits the total energy conservation and momentum conservation laws, and showed the error estimate. However, the error estimate can not be applied to the system without viscosity, due to the fact that the proof relies on the viscous term. Here, we show the error estimate for the system without viscosity by proposing a new structure-preserving finite difference scheme for the system. In addition, we also give the proof of existence of solution for the scheme.

6

Effect of Elasticity on Electrical Properties of Weft-Knitted Conductive Fabrics

Han Xiaoxue, Miao Xuhong, Chen Xi, Niu Li, Wan Ailan

Fibres & Textiles in Eastern Europe

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2021

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Vol. 29, no. 1 (145)

47--52

EN

Because of softness and lightness, various flexible sensors have attracted extensive attention and been widely studied. Sensing mechanism of most wearable sensors is derived from an elastic substrate, such as fabric or polymer materials. Although the mechanical-electrical performance of several flexible sensors has been reported, including sensitivity, linearity hysteresis and repeatability, research on the effects of substrate elasticity on sensor capacity is scarce. In this paper, the impact of spandex content, washing and ironing processing on the elasticity of weft knitted sensors was investigated by the constant- extension test method. Afterwards, differences in sensing properties between diverse elastic sensors under single as well as repeated stretch were reported. The experimental results showed that spandex content does influence the elasticity of knitted fabric, which has a further great effect on sensing properties. A highly elastic sensor is capable of detecting large-scale human motions, while sensors with lower elasticity are opposite, which demonstrates that elastic sensors can be designed and chosen to meet the requirements of detecting and monitoring distinct human motions.

PL

Ze względu na swoją delikatność i lekkość czujniki elastyczne przyciągają uwagę i są często stosowane. Często opisywane jest działanie mechaniczno-elektryczne kilku elastycznych czujników, w tym czułość, histereza liniowości i powtarzalność, badania nad wpływem elastyczności podłoża na pojemność czujnika są dość rzadkie. W pracy zbadano wpływ zawartości spandex’u, obróbki prania i prasowania na sprężystość dzianin wątkowych metodą badania stałego rozciągania. Następnie odnotowano różnice we właściwościach wykrywania między różnymi czujnikami sprężystymi przy pojedynczym i powtarzanym rozciągnięciu. Wyniki eksperymentalne wykazały, że zawartość spandex’u wpływa na elastyczność dzianiny, co dodatkowo ma duży wpływ na właściwości wyczuwalne. Wyniki pokazały, że wysoce elastyczny czujnik jest w stanie lepiej wykrywać ruchy człowieka, niż czujniki o niższej elastyczności, co pokazuje, że czujniki elastyczne można zaprojektować i wybrać tak, aby spełniały wymagania wykrywania i monitorowania różnych ruchów człowieka.

7

Optimum design of elastic moduli for the multiple load problems

Lewiński T.

Archives of Mechanics

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2021

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Vol. 73, nr 1

27--66

EN

The paper deals with minimization of the weighted average of compliances of structures, made of an elastic material of spatially varying elasticity moduli, subjected to n load variants acting non-simultaneously. The trace of the Hooke tensor is assumed as the unit cost of the design. Three versions of the free material design are discussed: designing the moduli of arbitrary anisotropy (AMD), designing the moduli of an isotropic material (IMD), designing of Young’s modulus for a fixed Poisson ratio (YMD). The problem is in all cases reduced to the Linear Constrained Problem (LCP) of Bouchitté and Fragalà consisting of two mutually dual problems: stress based and strain based, the former one being characterized by the integrand of linear growth depending on the trial statically admissible stresses. The paper shows equivalence of the stress fields solving the (LCP) problem and those appearing in the optimal body subjected to subsequent load cases.

8

Analysis of elastic deformation of amorphous polyethylene in uniaxial tensile test by using molecular dynamics simulation

Le Tien-Thinh

Computer Methods in Materials Science

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2020

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Vol. 20, No. 2

38--44

EN

In this paper, the linear elastic response to uniaxial tension of amorphous polyethylene was investigated by using Molecular Dynamics (MD) simulation. The polymeric system was initiated using a Monte Carlo-based technique and then equilibrated by a relaxation sequence at temperature of 100 K under a NPT control. Uniaxial tension test was carried out by modifying the corresponding component of the pressure tensor, with a loading rate of 0.5 bar/ps. The results showed that at 100 K (which is smaller than the glass transition temperature), the amorphous polymeric material exhibited a linear elastic response to uniaxial tension. The obtained Young’s modulus and Poisson’s ratio were also compared with values reported in the literature. Finally, parametric studies were performed on the stress-strain curve as a function of loading axis, number of chains and number of monomer units, respectively.

PL

W pracy przeprowadzono badania metodą dynamiki molekularnej sprężystej odpowiedzi amorficznego polietylenu w osiowosymetrycznej próbie rozciągania. System polimetryczny został zainicjowany metodą Monte Carlo a następnie zrównoważony poprzez relaksację w temperaturze 100 K ze sterowaniem NPT. Próby rozciągania przeprowadzono poprzez zmodyfikowanie odpowiedniej składowej tensora naprężeń, przyjmując prędkość obciążania 0.5 bar/ps. Wyniki wykazały, że w temperaturze 100 K (która jest niższa od temperatury zeszklenia), amorficzny polimer wykazuje liniową sprężystość w próbie rozciągania. Wyznaczone wartości modułu Younga i współczynnika Poissona zostały porównane z danymi literaturowymi. Wreszcie przeprowadzono parametryczną ocenę krzywych naprężenieodkształcenie w zależności od kierunku obciążenia, liczby łańcuchów oraz liczby jednostek monomeru.

9

Ocena wpływu warunków badania na parametry mechaniczne miedzi wyznaczone w procesie indentacji

Makuch Anna, Grygiel Dariusz, Szczeblewski Michał, Korzeniewski Wojciech

Inżynieria Powierzchni

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2019

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nr 1

54--60

PL

Celem pracy była ocena zjawisk na poziomie mikrostrukturalnym w procesie odkształcania popularnego w zastosowaniach medycznych materiału jakim jest miedź, a w szczególności zbadanie wpływu parametrów indentacji tj. prędkości odkształcenia, czasu przetrzymania i siły obciążania/odciążania na jej właściwości mechaniczne. Szczególną uwagę zwrócono na zależności między strukturą materiału, charakterem odkształcenia i właściwościami mechanicznymi. W wyniku przeprowadzonych badań stwierdzono, że największy wpływ na parametry określone w procesie indentacji spośród badanych zmiennych ma siła, z jaką wgłębnik zagłębia się w materiał. Najwyższą twardość odnotowano przy sile 500 mN i prędkości 5000 mN/min. Również na wielkość energii odkształcenia niesprężystego największy wpływ ma siła obciążenia/odciążenia – jej wzrost o 50% powoduje dwukrotny wzrost pracy odkształcenia niesprężystego.

EN

The aim of the paper was to evaluate phenomena at the microstructural level in the deformation process of copper – a material popular in medical applications, and in particular to investigate the influence of indentation parameters, i.e. strain rate, holding time and loading / unloading force on its mechanical properties. Particular attention was paid to the relationships between the structure of the material, the nature of the deformation and the mechanical properties. As a result of the conducted tests, it was found that from the tested variables the force with which the indenter sinks into the material has the greatest influence on the parameters determined in the indentation process. The highest hardness was recorded at the force of 500 mN and the strain rate of 5000 mN/min. Also, in the inelastic, the loading/unloading force plays has the most important role greatest influence on the amount of inelastic and total work – its increase by 50% causes the twofold increase in the value of the inelastic deformation work.

10

Identification of local elastic parameters in heterogeneous materials using a parallelized femu method

Petureau L., Doumalin P., Bremand F.

International Journal of Applied Mechanics and Engineering

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2019

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Vol. 24, no. 4

140--156

EN

In this work, we explore the possibilities of the widespread Finite Element Model Updating method (FEMU) in order to identify the local elastic mechanical properties in heterogeneous materials. The objective function is defined as a quadratic error of the discrepancy between measured fields and simulated ones. We compare two different formulations of the function, one based on the displacement fields and one based on the strain fields. We use a genetic algorithm in order to minimize these functions. We prove that the strain functional associated with the genetic algorithm is the best combination. We then improve the implementation of the method by parallelizing the algorithm in order to reduce the computation cost. We validate the approach with simulated cases in 2D.

11

Modelling of load-displacement curves obtained from scaffold components tests

Błazik-Borowa E., Szer J., Borowa A., Robak A., Pieńko M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2019

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Vol. 67, nr 2

317--327

EN

The paper presents the modelling measurement results of the load-displacement relation for scaffold stands and bracings. In the case of stands, there are two sections of curves, i.e. a straight-line and curvilinear section, and in the case of bracings, two straight line sections as well as one curvilinear section are distinguished. As a result of analyses, it is concluded that the sections which can be approximated by means of linear functions should be distinguished in graphs, if possible. On the one hand, this results from the evaluation methods of scaffold components. Nevertheless, the determination of elastic-linear scope of components’ operation is useful in engineering practice during computer calculations. Moreover, the method of determining an intersection point between functions, approximating tests results, along with analysis of the impact of polynomial degree, approximating the research results, on the time and effectiveness of the process of approximating functions selection, are all demonstrated in this article. The proposed method can prove useful in all science fields where curves obtained from any research (laboratory test, in situ test, numerical analysis) require approximation or replacement with a simpler description.

12

Mechanical guidelines on the properties of human healthy arteries in the design and fabrication of vascular grafts: experimental tests and quasi-linear viscoelastic model

Faturechi Rahim, Hashemi Ata, Abolfathi Nabiollah, Solouk Atefeh

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 3

13--21

EN

Knowledge of mechanical behavior of healthy human arteries as the guidelines to target properties of vascular grafts deserves special attention. There is a lack of mathematical model to characterize mechanical behavior of biomaterial while many mathematical models to reflect mechanics of human arteries have been proposed. The objective of this paper was set to measure mechanical properties of healthy human arteries including Common Carotid Artery (CCA), Abdominal Aorta Artery (AAA), Subclavian Artery (SA), Common Iliac Artery (CIA) and Right and Left Iliac Artery (RIA and LIA) and compare them to those of commercial ePTFE and Dacron®. Methods: Series of stress relaxation and strain to failure tests vere performed on all samples. The experimental data was utilized to develop quasi-linear viscoelastic (QLV) model of both natural and artificial arteries. Results: ePTFE is the stiffest sample, while the CCA is the most compliant one among all. RIA and CIA are more viscous than the other natural arteries, while AA and CCA are less viscous. The proposed model demonstrated an accurate fit to the experimental results, a proof of its ability to model both nonlinear elasticity and viscoelasticity of the human arteries and commercial ones. Conclusions: ePTFE and Dacron® are much stiffer than human arteries that may lead to the disruption of blood hemodynamic and may not be biomechanically feasible as a replacement.

13

Estimation of potential elastic energy during the countermovement phase of a vertical jump based on the force-displacement curve

Struzik Artur, Zawadzki Jerzy

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 1

153--160

EN

Purpose: One inconvenience in finding experimental evidence for the relationship between potential elastic energy and vertical jump height is the difficulty of estimating the value of the stored potential elastic energy. Therefore, the aim of this study is to present a simple method of estimating the potential elastic energy stored by lowering the center of mass during the countermovement phase of a vertical jump. Methods: The research was conducted on 30 able-bodied male university students (age: 20 years, body height: 183.1 ± 7.9 cm, body mass: 80.3 ± 10.4 kg). Each participant performed 10 single countermovement jumps with arms akimbo to maximal height. Measurements employed a Kistler force plate. The value of potential elastic energy was estimated based on the curve of dependence of the ground reaction force on the vertical displacement of the jumper’s center of mass. Results: The mean value (±SD) of potential elastic energy collected due to lowering of the center of mass during the countermovement phase of a vertical jump was 183 ± 69 J. 24.3% of this value can be considered the part of the potential elastic energy (44 ± 21 J) that comes from the transformation of kinetic energy. The total change in gravitational potential energy due to lowering the center of mass was 240 ± 58 J. Conclusions: This estimation of potential elastic energy is only general and rough. However, certain estimations of potential elastic energy may offer some insight into the phenomenon relating vertical quasi-stiffness and the ability to store potential elastic energy with vertical jump height.

14

Przyczynek do analizy nieliniowo sprężystej dźwigarów zespolonych stalowo-betonowych

Wranik J.

Przegląd Budowlany

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2018

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R. 89, nr 6

39--45

PL

W praktyce inżynierskiej nośność elementów konstrukcji projektuje się zwyczajowo przy przyjęciu sił wewnętrznych obliczonych wg teorii liniowo sprężystej. W opracowaniu niniejszym wskazano na bliższą rzeczywistości możliwość wyznaczania tych sił przez uwzględnienie fizycznej nieliniowości betonu, w szczególności zbrojonego betonu rozciąganego. Dla rozwiązania zagadnienia skorzystano z metody sił, a tym samym spełnione są warunki równowagi i warunki nierozdzielności przemieszczeń. Podany sposób umożliwia wyznaczenie macierzy podatności równań metody sił dla belek zespolonych w kolejnych iteracjach za pomocą bezpośredniego całkowania funkcji matematycznych przedziałami ciągłych, bez konieczności podziału belki na elementy skończone. Iteracja wynika z powodu nieznanej ilości zbrojenia ewentualnie skomplikowanych funkcji podcałkowych.

EN

In practice of engineering load-bearing capacity of construction elements, the designs are usually created with the assumption of internal forces calculated according to the linear-and-resilient theory. The following paper describes the possibility to determine these forces using a method which is closer to reality, i.e. by taking into account the non-linearity of concrete, in particular of reinforced tension concrete. To resolve the issue, a force method has been applied, which means fulfilment of conditions of balance as well as conditions of inseparability of displacements. The presented method makes it possible to determine the matrix of susceptibility of equations of the force method for composite beams in subsequent iterations through direct integrating of mathematical functions with intervals of continuous functions, without the necessity to divide the beam into finished elements. Iteration results from unknown quantity of reinforcement possibly complex integrands.

15

Measurement of Molding Sand Elasticity

Major-Gabryś K., Grabarczyk A., Dobosz S.M., Jakubski J., Morek J., Beňo J.

Journal of Casting & Materials Engineering

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2018

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Vol. 2, no. 2

38--44

EN

The progressive mechanization and automation of industrial equipment is the driving force of progress, not only in the field of production but also in the measuring and control equipment. In mold production, the automation of processes such as forming molds and cores along with their assembly has led to increases in serial production, reductions in defects, and the shortening of molding times, among others. Thanks to automation in mold and core departments and the use of all sorts of manipulators, mold production in foundries has gained momentum. Unfortunately, in addition to the mentioned advantages, there are also new challenges as to the quality and properties of the molding and core sands used in highly automated foundries.This article presents recent research on molding sand elasticity. The topic was introduced as an attempt to answer the new needs of highly mechanized foundries. The article discusses a new method of measuring the resistance of molding materials to undergoing mechanical deformation (molding sand elasticity), with an additional analysis of the bending strengths of the tested samples. Precise measurements, test sample preparation, and interpretation of the received results are presented in the article.

16

Warunek plastyczności i funkcja dyssypacji materiałów porowatych

Szwed A.

Autobusy : technika, eksploatacja, systemy transportowe

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2018

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R. 19, nr 12

680--684

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.

17

The Tendency of Moulding Sands to Generate Core Cracks

Grabarczyk A., Dobosz S. M., Kusiński J., Major-Gabryś K.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 1

157--161

EN

The constant growth of foundry modernization, mechanization and automation is followed with growing requirements for the quality and parameters of both moulding and core sands. Due to this changes it is necessary to widen the requirements for the parameters used for their quality evaluation by widening the testing of the moulding and core sands with the measurement of their resistance to mechanical deformation (further called elasticity). Following article covers measurements of this parameter in chosen moulding and core sands with different types of binders. It focuses on the differences in elasticity, bending strength and type of bond destruction (adhesive/cohesive) between different mixtures, and its connection to the applied bonding agent. Moulding and cores sands on which the most focus is placed on are primarily the self-hardening moulding sands with organic and inorganic binders, belonging to the group of universal applications (used as both moulding and core sands) and mixtures used in cold-box technology.

18

Thermal aging of hydrogenated nitrile rubber – loss of additives and its influence on elasticity maintenance

Liu X., Zhao J., Yang R., Iervolino R., Barbera S.

Polimery

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2017

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T. 62, nr 7-8

588--598

EN

The thermal aging of hydrogenated nitrile rubber (HNBR) at elevated temperatures 125 and 150 °C was investigated. The changes of chemical structures, including functional groups and crosslinking density, and the changes of mechanical properties, including recovery from bending (RFB), tensile strength, elongation at break and Young's modulus, were determined. In addition, the loss of additives was analyzed by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). The aging procedure of HNBR exhibited two stages: loss of additives along with the deterioration of elasticity; obvious oxidation and extra crosslinking with further hardening and embrittlement. The relationship between the deterioration of elasticity and the loss of plasticizers was established. It was demonstrated that the failure of HNBR happened long before obvious oxidation and crosslinking of the rubber chains, and the loss of additives, especially the loss of plasticizers, was the main reason for the failure. Therefore, the elasticity recovery of aged HNBR immersed in the plasticizer (n-propyl palmitate as a model) was carried out. This treatment was demonstrated to be effective before obvious oxidation and crosslinking of HNBR occurred during the thermal aging.

PL

Badano starzenie termiczne uwodornionego kauczuku nitrylowego (HNBR) w temperaturze 125 i 150 °C. Określono zmiany struktur chemicznych, w tym grup funkcyjnych i gęstości usieciowania oraz zmiany właściwości mechanicznych, w tym powrotu poodkształceniowego po zginaniu (RFB), wytrzymałości na rozciąganie, wydłużenia przy zerwaniu i modułu Younga. Ponadto metodą pirolitycznej chromatografii gazowej z detekcją mas (Py-GC/MS) analizowano straty dodatków obecnych w kauczuku. Procedura starzenia się HNBR wykazywała dwa etapy: ubytek dodatków wraz z pogorszeniem elastyczności; wyraźne utlenianie i dodatkowe sieciowanie związane z dalszym utwardzaniem i zwiększaniem kruchości. Określono zależność pomiędzy zmniejszaniem się elastyczności a ubytkiem dodatków zmiękczających. Wykazano, że pogorszenie właściwości HNBR następowało znacznie wcześniej niż utlenianie i sieciowanie oraz było spowodowane utratą dodatków, a zwłaszcza plastyfikatorów. W związku z tym przeprowadzono próbę odtworzenia elastyczności starzonych próbek HNBR przez zanurzenie w plastyfikatorze (palmitynian n-propylu jako model). Obróbka ta okazała się skuteczna, pod warunkiem przeprowadzenia jej zanim podczas starzenia termicznego nastąpiło utlenianie i sieciowanie HNBR.

19

First-principles study of mechanical, vibrational and thermodynamic properties of magnetic XC compounds (X = Rb, Sr)

Lakdja A., Benzaidi I., Sayede A., Chahed A.

Materials Science Poland

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2017

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Vol. 35, No. 3

463--469

EN

Lattice dynamic and mechanical properties of hypothetical RbC and SrC compounds were investigated using the ab-initio pseudopotential method and a linear response scheme. The lattice dynamics was studied in the framework of the density functional perturbation theory (DFPT). The dynamical and mechanical stability of the hypothetical RbC and SrC compounds was proved in their equilibrium B1 structure. In addition, the same stability was confirmed in the B3 phase. The thermodynamic properties were also investigated. They exhibited the same trend in both phases, and followed the Debye model. These results were confirmed in the ferromagnetic state, which makes the investigated compounds promising candidates in the spintronic field.

20

Identification of the Process of Dynamic Stretching of Threads in Warp-Knitting Technology

Prążyńska A., Mikołajczyk Z.

Autex Research Journal

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2017

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Vol. 17, no. 4

334--343

EN

The publication presents a theoretical study of the susceptibility of rheological models of threads to dynamic stretching in the context of modern, highly efficient textile technologies. Input parameters of the four analyzed models, the Kelvin-Voigt model, the Maxwell model, Standard model 2, and the Zener model, corresponded to the actual values of the coefficients of viscosity, elasticity, kinematic and dynamic loading, and stretching speed for the analyzed polyester silk threads produced in a knitting process, with knitting speeds from 700 to 1,600 courses/min. The research proves that the tested thread models behave differently in the stretching process-the Kelvin-Voigt model is sensitive to both the increases in kinematic loading and viscosity coefficient, Standard model 2 is only susceptible to dynamic stiffness, and the Zener model is significantly sensitive to kinematic loading. All responses of the models increase with the increase in stretching speeds. The obtained results indicate substantial “accuracy tolerance” in setting input parameters while identifying dynamics of the knitting process on warp-knitting machines.