Wyniki wyszukiwania - BazTech

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

|

2023

|

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

Еlastic properties of tyres affecting car comfort, driving and riding

Dechkova Silvia

International Journal of Applied Mechanics and Engineering

|

2023

|

Vol. 28, no. 4

54--68

EN

The present paper focuses on an elastic properties analysis of new and depreciated tires. The research was carried out using two different methods, field and numerical, respectively. The purpose of the study is to check whether there is a change in the elastic properties of the tire during its depreciation and to what extent these processes affect the comfort of driving and riding. The experimental tests were conducted on a hydraulic test stand and by applying strength and deformation analysis the effect of its structure deformation was additionally considered. The investigation performed on a vehicle-based tire test stand to find out stress-strain and tire deformation was with different vertical loading according to FEM. The numerical solution was reached by implementing SolidWorks - Simulation and Abaqus. The obtained results are graphically compared, and the average value of the elastic constant for a new and depreciated tire has been determined.

3

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

Klasztorny Marian, Nycz Daniel B.

Composites Theory and Practice

|

2023

|

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).

4

Rheological properties of elastic-visco-plastic liquid

Dadash-Zade Mirza A., Aliyev Inglab N.

Nafta-Gaz

|

2022

|

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.

5

Strength analysis of sandwich beams with linear elastic inner layer

Kimura Koichi

Journal of Applied Mathematics and Computational Mechanics

|

2022

|

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.

6

Development of Multilayer Woven Fabrics for the Adoptive Geometry Composite Structure

Zubair Zakariya, Alali Moussa, L'hostis Gildas, Zubair Muhammad, Drean Jean-Yves

Fibres & Textiles in Eastern Europe

|

2021

|

Vol. 29, no. 4 (148)

56--61

EN

In this study nine multilayer 3D woven structures were produced using polyamide filament yarns both in the warp and weft direction. Three different weaves: plain, 1/3 twill and 3/1 rib in the middle layer, and plain weave in both the top and bottom layers were produced. All specimens were developed on a narrow weaving machine equipped with multi beams and creel options. The samples were tested for tensile strength, air permeability, compressibility, resilience, bending and shear stiffness. Better compressibility was observed in 3/1 warp rib, followed by 1/3 twill and plain weave in the middle layer. Shear stiffness and bending rigidity were higher for those fabrics which had a plain weave in all layers and higher filling density. The air permeability was higher for low weft density, plain weave and its derivative 3/1 warp rib in the middle layer. Tensile strength was higher for those fabrics which were produced with higher weft densities.

PL

W badaniu wytworzono dziewięć wielowarstwowych tkanych struktur 3D z przędz z włókien poliamidowych zarówno w kierunku osnowy, jak i wątku. Zastosowano trzy rodzaje splotów. Próbki zbadano pod kątem wytrzymałości na rozciąganie, przepuszczalności powietrza, ściśliwości, sprężystości, zginania i sztywności. Wartości sztywności były wyższe dla tych tkanin, które miały splot płócienny we wszystkich warstwach i większą gęstość wypełnienia. Przepuszczalność powietrza była wyższa dla wątku o małej gęstości i splotu płóciennego. Wytrzymałość na rozciąganie była wyższa dla tkanin, które były wytwarzane z większą gęstością wątku.

7

Dynamic damage analysis of a ten-layer circular composite plate subjected to low-velocity impact

Raissi Hamed

Archives of Civil and Mechanical Engineering

|

2021

|

Vol. 21, no. 3

158--199

EN

A new theoretical solution is presented to determine the stress distribution in a ten-layer simply-supported circular composite plate subjected to the low-velocity impact. The aim of the current study is the investigation of the dynamic analysis of the composite plate when a cylindrical impactor hits the top layer of the plate with an initial velocity of 1 m/s. The plate is made of two adhesive layers adhere two aluminum layers to a six-layer carbon-epoxy laminated plate. The classical non-adhesive elastic contact theory and Hunter's relationship are used to simulate the contact behavior in terms of time and contact radius. By using Hamilton's principle and Layerwise theory, thirty-two equations of motion are derived. Moreover, Johnson–Cook’s criteria, the plastic simulation model, the normal stress–strain failure criterion theory were used for failure analysis of the aluminum, adhesive, and carbon-epoxy layers, respectively. The numerical method was used to solve the thirty-two differential equations of motion based on the finite difference method. Moreover, the relationship between stress and strain is re-written in the numerical code so that the failure criterion theories are satisfied. Moreover, according to the defined failure criterion for each layer, the damage is checked at the end of every time step. In addition, the damping behavior of the composite plate after applying the contact pressure caused by the impact was also investigated. The results showed that the impact resulted in residual stress in the plate.

8

Damage recovery for simulated modular robots through joint evolution of morphologies and controllers

Akrour Djouher, Djedi NourEddine

Journal of Automation Mobile Robotics and Intelligent Systems

|

2019

|

Vol. 13, No. 1

15--19

EN

In order to be fully autonomous, robots have to be resilient so that they can recover from damages and operate for a long period of time with no human assistance. To be resilient, existing approaches propose to change the robots’ behavior using a different control system when a hardware fault or damage occurs. These approaches are used for robots which have fixed morphologies. However, we cannot assume which morphology would be optimal for a given problem and which morphology allows resilience. In the present paper, we introduce a new approach that generates resilient artificial modular robots by evolving the robot morphology along with its controller. We used a multi-objective evolutionary algorithm to optimize two objectives at a time, which are the traveled distance of a damage-free robot and the traveled distance of the same robot with damaged parts. The result of preliminary experiments demonstrates that during evaluation, when robots are deliberately faced to motor failures, the evolution process can optimize and generate new morphologies for which the robot’s behavior is less affected by damage. This makes the robot capable to recover its ability to move forward.

9

Przyczynek do analizy nieliniowo sprężystej dźwigarów zespolonych stalowo-betonowych

Wranik J.

Przegląd Budowlany

|

2018

|

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.

10

Analiza wpływu przebiegu procesu odkształcenia na nawrót sprężysty asfaltów modyfikowanych polimerami – część I

Jurczak R.

Magazyn Autostrady

|

2018

|

Nr 10

56--60

PL

Ze względu na coraz trudniejsze warunki pracy nawierzchni pożądana jest zdolność mieszanek mineralno-asfaltowych do rozpraszania naprężeń (relaksacji), która wiąże się przede wszystkim z obecnością lepiszcza. Zatem użyty w mieszance asfalt powinien wykazywać zdolność do relaksacji w możliwie jak najszerszym zakresie temperatur. Przydatnych informacji o podatności lepiszcza do większej relaksacji naprężeń powstających w mieszance może dostarczyć pomiar nawrotu sprężystego.

EN

Because of more and more difficult working conditions of the surface, the ability of asphalt mixtures to dissipate stresses (relaxation) is desired, which is mainly related to the presence of a binder. Therefore, the asphalt used in the mixture should have the ability to relax in the widest possible temperature range. A test of elastic recovery can provide useful information about the binder’s susceptibility to greater stress relaxation in the mixture.

11

Warunek plastyczności i funkcja dyssypacji materiałów porowatych

Szwed A.

Autobusy : technika, eksploatacja, systemy transportowe

|

2018

|

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.

12

Response of thermoelastic micropolar cubic crystal under dynamic load at an interface

Ailawalia P., Sachdeva S. K., Pathania D.

International Journal of Applied Mechanics and Engineering

|

2017

|

Vol. 22, no. 1

5--23

EN

The purpose of this paper is to study the two dimensional deformation in a thermoelastic micropolar solid with cubic symmetry. A mechanical force is applied along the interface of a thermoelastic micropolar solid with cubic symmetry (Medium I) and a thermoelastic solid with microtemperatures (Medium II). The normal mode analysis has been applied to obtain the exact expressions for components of normal displacement, temperature distribution, normal force stress and tangential coupled stress for a thermoelastic micropolar solid with cubic symmetry. The effects of anisotropy, micropolarity and thermoelasticity on the above components have been depicted graphically.

13

Towards a more responsible sustainable innovation assessment and management culture in Europe

Popper R., Popper M., Velasco G.

Engineering Management in Production and Services

|

2017

|

Vol. 9, no. 4

7--20

EN

This article presents new concepts and practical approaches resulting from the piloting of CASI-F – a common framework for the assessment and management of sustainable innovation (SI). Based on lessons learned from action research carried out in the context of the EU funded CASI project, the article focuses on the meta-analysis of 46 action roadmaps produced with 43 innovators supporting the practical application of CASI-F. The applied methodology helped to demonstrate that a multi-level and multi-actor advice approach promotes a shift towards improved understanding of innovations-related critical issues (barriers, drivers, opportunities and threats) and stakeholders’ relations, as well as their management, thus promoting the sustainable resilience and transformation of socio-technical systems. This paper first reflects on how we arrived to managerial lessons from the actions roadmaps and how could these lessons be used to assess the current state of affairs and potential way forward for European initiatives and instruments promoting sustainable innovation.

14

The influence of the cumulated deformation energy in the measurement by the DSI method on the selected mechanical properties of bone tissues

Makuch A. M., Skalski K. R., Pawlikowski M.

Acta of Bioengineering and Biomechanics

|

2017

|

Vol. 19, no. 2

89--91

EN

Purpose: The goal of the study was to determine the influence of DSI test conditions, i.e. loading/ unloading rates, hold time, the value of the maximum loading force on selected mechanical properties of trabecular bone tissue. Methods: The test samples were resected from a femoral head of a patient qualified for a hip replacement surgery. During the DSI tests hardness (HV, HM, HIT) and elastic modulus (EIT) of trabecular bone tissue were measured using the Micro Hardness Tester (MHT, CSEM). Results: The analysis of the results of measurements and the calculations of total energy, i.e. elastic and inelastic (Wtotal,Welastic,Winelastic) and those of the parameters of hardness and elasticity made it possible to assess the impact of the process parameters (loading velocity, force and hold time) on mechanical properties of bone structures at a microscopic level. Conclusions: The coefficient k dependent on the ratio EIT / HIT and on the stored energy (ΔW = Wtotal- Welastic) is a measure of the material reaction to the loading and the deformation of tissue.

15

Application of force-length curve for determination of leg stiffness during a vertical jump

Struzik A., Zawadzki J.

Acta of Bioengineering and Biomechanics

|

2016

|

Vol. 18, no. 2

163--171

EN

Purpose: The aim of this study was to present the methodology for estimation of a leg stiffness during a countermovement jump. The question was asked whether leg stiffness in the countermovement and take-off phases are similar to each other as demonstrated in previous reports. It was also examined whether the stiffness in left lower limb is similar to the one in right lower limb. Methods: The research was conducted on 35 basketball players. Each participant performed three countermovement jumps with arm swing to the maximum height. Measurements employed a Kistlerforce plate and a BTS SMART system for motion analysis. Leg stiffness (understood as an inclination of the curve of ground reaction forces vs. length) was computed for these parts of countermovement and take-off phases where its value was relatively constant and F(∆l) relationship was similar to linear. Results: Mean value (±SD) of total stiffness of both lower limbs in the countermovement phase was 7.1 ± 2.3 kN/m, whereas this value in the take-off phase was 7.5 ± 1 kN/m. No statistically significant differences were found between the leg stiffness in the countermovement and the take-off phases. No statistically significant differences were found during the comparison of the stiffness in the right and left lower limb. Conclusions: The calculation methodology allows us to estimate the value of leg stiffness based on the actual shape of F(∆l) curve rather than on extreme values of ∆F and ∆l. Despite different tasks of the countermovement and the take-off phases, leg stiffness in these phases is very similar. Leg stiffness during a single vertical jump maintains a relatively constant value in the parts with a small value of acceleration.

16

Projektowanie sprzęgła kompensacyjnego

Mambetow A. D., Bajramukow A. O., Kruczek W.

Mechanik

|

2015

|

R. 88, nr 10

812--816

PL

Przedstawiono propozycje nowej konstrukcji sprzęgła sprężystego do połączenia dwóch wałów. Wykorzystano analityczną metodę wykonywania obliczeń, która umożliwia ustalenie zależności wielkości siły ściskającej nakrętkę od momentu obrotowego napędu. Zaproponowano szereg typowymiarów sprzęgieł, których parametry geometryczne określono według wartości nacisków zewnętrznych.

EN

Presented are proposals of the new flexible couplings for end to end connection of shafts. Analytical method presented in the paper makes it possible to find the relationship between the force exerted on the nut and the driving torque. Suggested in the paper are series of the coupling type sizes, geometric parameters of which are indicated by external pressures rates.

17

Resilience and Deformability of Fused Textile Systems

Ancutiene K., Strazdiene E., Krusinskiene L.

Fibres & Textiles in Eastern Europe

|

2015

|

Vol. 23, no. 4 (112)

39--45

EN

The aim of this research was to investigate the resilience properties of textile systems fused with different interlinings by applying the method of pendulum impact loading. For the investigations, four worsted outer fabrics and four interlinings were chosen. For testing, a pendulum impact device was used, the operation of which is based on cyclical strikes of the spherical indentor upon the specimen, taking into account the resilience and deformability of the material. It was defined that resilience properties could be characterised not only by the values of impact bn and angles rebound αn but also by the duration of vibration periods Tn. It was defined that the decay of pendulum impact bn and rebound angles αn in the period of t = 20 s can be described by power function y = a + bxc with a high accuracy (R2 = 0.995 - 0.999). For the rebound process, better resilience of fabrics and their fused systems is characterized by higher values of power function coefficients a and b and lower values of its coefficient c. For the impact process, lower deformability of the samples tested is characterised by lower values of power function coefficients a and b, but with a more intensive decrease in deformability – by higher values of coefficient c. The degree of the fused system’s deformability directly depends upon the thickness and mass per unit area of the interlinings used, i.e. less deformable and more stable systems were obtained with thicker interlinings, the mass per unit area of which was higher.

PL

Celem pracy było zbadanie właściwości odprężania tekstylnych systemów łączonych z różnymi podszewkami. Zastosowano metodę obciążenia za pomocą wahadła. Dla badań wybrano cztery czesankowe tkaniny zewnętrzne i cztery różne podszewki. Badania przeprowadzono z użyciem urządzenia, w którym wahadło przenosi cyklicznie obciążenia wymuszone uderzeniami w próbkę sferycznego impaktora. W badaniach brano pod uwagę odprężenie i deformację materiału. Założono, że właściwości odprężające mogą być scharakteryzowane nie tylko przez wielkość obciążenia i kąt odbicia, ale również przez czas trwania okresowych wibracji. Stwierdzono, że zanik wymuszenia i zmiany kąta odbicia w czasie 20 sekund mogą być opisane przez funkcję wykładniczą z dużą dokładnością (R2 = 0,995 - 0,999). Stopień deformacji połączonych systemów włókienniczych zależny od ich grubości i masy na jednostkę powierzchni zastosowanych podszewek. Oznacza to, że mniej podatne na deformacje i bardziej stabilne są systemy uzyskane za pomocą grubszych podszewek, których masa na jednostkę powierzchni jest większa.

18

Porównanie parametrów reologicznych zaczynu cementowego na bazie CEM i 42,5R w zależności od przyjętego modelu płynięcia

Kaleta A.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

|

2014

|

z. 104

73-76

EN

The paper presents results of the rheological properties of cement CEM I 42,5R at 15°C. Rheological properties of cement pastes were calculated from the resulting flow curves using various rheological models. The Bingham, Herchel–Bulkley and Casson models were used to estimate the stress strain relations. It was observed that the rheological properties of cement pastes varied with the change of the rheological models used for their calculation.

19

Pomiary oddziaływania parasejsmicznego na obiekty budowlane

Biessikirski A.

Wiadomości Górnicze

|

2014

|

R. 65, nr 11

601--610

PL

Prawidłowa diagnoza przyczynowo-skutkowa oddziaływania drgań parasejsmicznych na dany obiekt budowlany jest bardzo trudna. Wywoływane przez drgania naprężenia początkowo pogłębiają niedoskonałości struktury wewnętrznej kruchego materiału budowlanego, a dopiero po przekroczeniu granicy sprężystości powodują jego pękanie i zniszczenie. W artykule przedstawiono zagadnienia związane z wystąpieniem oddziaływań wynikających ze zjawisk sejsmicznych oraz parasejsmicznych.

EN

A proper cost-and effect diagnosis of the impact of para-seismic vibrations on a given construction object is very difficult. The stress, caused by vibrations, initially deepen imperfections of internal structure of fragile construction material and after exceeding of the elastic limit they cause its cracking and destruction. The article presents the issues related to the occurrence of impacts resulting from seismic and paraseismic phenomena.

20

The importance of the objective functions and flexibility on calibration of parameters of Clark instantaneous unit hydrograph

Wałęga A.

Geomatics, Landmanagement and Landscape

|

2014

|

no. 2

76--86

EN

The paper compares the results of automatic calibration of Clark's synthetic unit hydrographs. Optimal values of model parameters were determined by the objective functions: percentage error in peak flow (PEPF), percentage error in volume (PEV), peak-weighted root mean square error (PWRMSE), sum of absolute residuals (SAB.) and sum of squared residuals (SSR). The last part of the analysis assesses the flexibility of studied model. The research was performed in the upland watershed of Grabinka - left tributary of the Wisłoka river located in Southern Poland. The analysis reveals that the smallest differences between the maximum flow in the observed and calculated flood culmination were obtained when applying PWRMSE function. This paper also indicates, that Clark's model was efficient for describing the analyzed floods.