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EN
The paper deals with the working peculiarities of the support zones of reinforced concrete elements subject to bending with due account of the eccentric compression and tension. The authors performed simulation of the stress-strain behaviour of the indicated structures with the aid of “Lira” software which results are shown in the graphical and tabulated form. The performed simulation allowed of tracing the work of the studied sample beams till collapse. Such approach made it possible to single out and generalize the main collapse patterns of the inclined cross-sections of the reinforced concrete elements subject to bending on which basis the authors developed the improved method to calculate their strength (Karpiuk et al., 2019).
PL
Zarówno podczas eksploatacji samolotów i śmigłowców, jak również w badaniach elementów innych struktur cienkościennych obserwuje się wiele interesujących zjawisk zachodzących w połączeniach nitowych, jak na przykład odkształcenia plastyczne, fretting itp., które wpływają ujemnie na trwałość połączenia, powodując inicjację pękania pokrycia. W artykule zaprezentowano wyniki badań dotyczących wizualizacji pól naprężeń metodami analizy MES oraz optycznymi połączeń nitowanych oraz wskazano na możliwość wykorzystywania tego rodzaju metod w badaniach odkształceń występujących w tych połączeniach.
EN
During the exploitation of aircraft and helicopters, as well as in the study of elements of other thin-walled structures, many interesting phenomena are observed in riveted joints, such as plastic deformations, fretting, etc., which negatively affect the durability of the joint, causing the initiation of cracking of the covering. The paper presents the results of research concerning the visualization of stress fields by FEM analysis methods and optical methods of riveted joints and indicates the possibility of using such methods in studies of deformation occurring in such type of joints.
PL
W pracy omówiono wpływ naturalnego obciążenia termicznego na naprężenia i ugięcia betonowej płyty nawierzchniowej. Pierwsza część opracowania dotyczy analizy warunków klimatycznych występujących w Polsce. Na podstawie danych meteorologicznych uzyskanych z Instytutu Meteorologii i Gospodarki Wodnej przeanalizowano zmianę średniej temperatury powietrza i zmianę średniej minimalnej temperatury przy powierzchni gruntu. Omówiono także wpływ poszczególnych czynników klimatycznych na trwałość płyty betonowej przeznaczonej do budowy dróg i lotnisk. Druga część pracy obejmuje numeryczną analizę wpływu gradientów temperatury na deformację płyty. Wybrano dwie reprezentatywne stacje pomiarowe do szczegółowej analizy naprężeń w zależności od położenia geograficznego.
EN
The paper discusses the impact of the natural thermal load on stress and deflection of a concrete slab. The first part of the study concerns the analysis of climatic conditions occurring in Poland. Based on meteorological data obtained from the Institute of Meteorology and Water Management, the change in average air temperature and the change in the average minimum temperature at the ground surface were analyzed. The impact of individual climatic factors on the durability of the concrete slab intended for road and airfield construction was discussed. The second part of the study includes the numerical analysis of the impact of temperature gradients on the change in recorded deformations. Two representative measuring stations were selected for detailed stress analysis depending on the geographical location.
EN
The development of crosscuts within mining shafts’ protective pillars causes a change of state of stress in the surrounding rock mass. It also causes deformations of the rock mass and the surface. It is essential to conduct prediction analysis of the deformations and stresses in order to secure a proper functioning of a shaft located within the protective pillar. It is recommended that the analysis should be based on the integration of the finite element method (FEM) and geodetic monitoring results. FEM makes it possible to determine the rock mass stresses and displacements in the shaft protective pillars and in the surrounding rock mass. It makes is possible to determine the safety and proper functioning of the shaft. The results of the FEM analysis of the impact of crosscuts and mining activities on rock mass deformations inside and on the surface of the protective shaft pillar are presented. The influence of mining extractions was investigated. The mining panels were located around the safety pillar in three regions NW, SE and SW and the crosscut were located within the safety pillar. The presented methodology will allow for the determination of the deformations and strains in case of farther development of crosscuts within the protective shaft pilar and by planned mining activities around the pillar.
EN
The development of oil fields at a late stage is characterized by a number of complications that determine the features of the operation of downhole equipment in pumping units. The use of electric-centered pumps in wells with intervals of increased curvature intensity requires a preliminary analysis of the possibility of lowering and operating the equipment at design depths. The aim of research is development of a new approach to evaluation the stress-strain state of pumping equipment, taking into account the features of the inclinometry of the intervals of its location. The analysis of the results of previous studies of the influence of the well profile on the operation of pumping equipment and recommendations for ensuring its performance is carried out. Given the possibility of operating equipment with limited levels of deformation, a mechanism is proposed for evaluation its stress-strain state using software products based on the finite element method. The reliability of the results is confirmed by comparison with those obtained in the course of analytical studies performed according to a previously tested methodology. Application of the proposed approach will allow to assess the level of deformation of individual elements of the equipment installations, taking into account their design features and the results of inclinometry.
PL
Omówiono problematykę zarysowania żelbetowych płyt dennych w wielkokondygnacyjnych garażach podziemnych. Określono stany i naprężenia termiczno-skurczowe we wczesnym okresie twardnienia betonu, oceniono występujące skrępowanie płyty dennej w postaci oporów podłużnych w fazie studzenia płyty, wykazano zasadnicze różnice w zakresie przyjmowania wartości dopuszczalnych rys, jak też w obliczeniach minimalnego zbrojenia według normy polskiej opartej na Eurokodzie 2 oraz modyfikowanym Eurokodzie 2 – w przepisach niemieckich i przepisach francuskich.
EN
The problem of cracking reinforced concrete foundation slabs in multi-storey underground car parks is discussed. The thermal-shrinkage states and stresses in the early age concrete were determined, the existing restraining of the bottom slab in the form of longitudinal resistances in the slab cooling phase was assessed, fundamental differences were found in the limit values of cracks wmax, as well as in the calculation of the minimum reinforcement As, min according to the Polish standard based on Eurocode 2 and modified Eurocode 2 – in German and French regulations.
PL
Omówiono problematykę projektowania drewnianych belek dwutrapezowych z otworami w strefie kalenicy. Przedstawiono zagadnienia normowe oraz obliczenia numeryczne za pomocą metody elementów skończonych, z uwzględnieniem zbrojenia wzmacniającego. Zamieszczono rekomendacje dotyczące położenia otworów i stosowanego zbrojenia.
EN
The paper is dedicated to design of timber double tapered beams with openings in the apex area. Standard design regulation as well as computational analysis by the finite element method with the influence of reinforcement are presented. The work is supplemented with recommendations regarding the location of openings and the reinforcement used.
PL
Przedmiotem rozważań zaprezentowanych w pracy są przemieszczenia i naprężenia w elementach stalowych dźwigarów kratowych, spowodowane zmianami temperatury zewnętrznej i nierównomiernym rozkładem temperatur wewnątrz hali. Wielodniowe pomiary przemieszczeń stalowych, kratowych dźwigarów dachowych dużej rozpiętości połączone z pomiarami temperatury w przestrzeni hali i w różnych punktach dźwigarów wykazały znaczący wpływ nierównomiernego rozkładu temperatur na przemieszczenia. Zmierzone wartości przemieszczeń zostały porównane z przemieszczeniami otrzymanymi drogą symulacji numerycznych, w których danymi wejściowymi były pomierzone temperatury. Poza przemieszczeniami w pracy przeanalizowano także wzrost naprężeń w wybranych elementach dźwigara kratowego, spowodowany nierównomiernym rozkładem temperatur. Oceniono destrukcyjny wpływ temperatury na stan wytężenia analizowanych stalowych dźwigarów kratowych.
EN
The subject of considerations presented in the work are displacements and stresses in steel elements of truss girders, caused by changes in the external temperature and uneven distribution of temperatures inside the hall. Multi-day measurements of displacement of steel, large-span truss roof girders combined with temperature measurements in the hall space and at various points of the girders showed a significant influence of uneven temperature distribution on the displacements. The measured displacement values were compared with the displacements obtained by numerical simulations, in which the input data were measured temperatures. In addition to displacements, the increase of stress in selected elements of the truss girder, caused by uneven temperature distribution, was also analyzed in the paper. The destructive effect of temperature on the strain and stress state of the analyzed steel truss girders was assessed.
9
Content available remote Deflection of an eccentric crack under mixed-mode conditions in an SCB specimen
EN
Crack propagation under mixed-mode (I + II) conditions has been investigated in a semicircular disc where various levels of mixed-mode can be achieved by means of different geometry configurations. The research has been performed on a novel cementitious material, alkali-activated concrete. Its main advantage is that it is environment-friendly. On the other hand, its fracture mechanical properties, as of yet, have not been described sufficiently. Therefore, a fracture analysis has been performed. The crack deflection under three point bending conditions has been investigated numerically as well as experimentally. The numerical approach is based on a combination of the common finite element analysis and a multi-parameter form of the maximum tangential stress criterion. This generalized method is suitable especially for materials with specific (elasto-plastic, quasi-brittle etc.) fracture behaviour. The over-deterministic method together with the Williams expansion is applied to approximate selected stress tensor components around the crack tip. In this work, the influence of the eccentric crack is also discussed. In the conclusions, several recommendations about using single-parameter/multi-parameter fracture mechanics are stated.
10
Content available remote Kolorowanie jako forma walki ze stresem
PL
Obecnie jedną z najważniejszych przyczyn stresu zawodowego jest rozwój technologii i przeobrażenie rynku pracy, nakładające na pracownika obowiązek teleobecności. Ciągłe zanurzenie w technologii zaburza relację z samym sobą, utrudniając stosowanie metod autoterapeutycznych, które mogłyby przeciwdziałać szkodliwemu wpływowi stresu. Kolorowanie jest jedną z metod interwencji antystresowych. W procesie autoterapeutycznym ma ono wpływ nie tylko na sprawniejsze zarządzanie stresem, ale również na redukcję lęku oraz wzrost uważności, koncentracji i kreatywności u badanych osób.
EN
The paper presents the results of experimental investigations of total tensile stresses in a gyroplane’s rotor during flight. The research aimed to determine which flight maneuvers induce the greatest stress in the rotor blade and the hub bar. The object of research was an ultralight gyroplane Tercel by Aviation Artur Trendak equipped with a rotor by the same manufacturer. Measurements were taken a) at the root of the rotor blade in the longitudinal direction, at the rotor blade’s lower surface in the point where the blade is attached to the hub bar, and b) in the hub bar, on its lower surface also in the longitudinal direction. To measure the stress, the author constructed an original measuring system based on the strain gauge bridge circuit mounted on the rotor head. The tests were carried out in a wide range of maneuvers within the gyroplane’s flight envelope. The highest value of tensile stress was found to occur while rapidly reducing the horizontal velocity in steep descent.
12
Content available Fatigue testing machines and apparatus
EN
This paper presents selected examples of construction and applications of fatigue test stands. The authors made a review of universal fatigue machines and test stands, made specifically for own and individual programs to research fatigue material properties. The publication contains the developed procedures to determine the fatigue life of materials. The authors also describe how to implement these procedures to control and measurement systems in research stands. The article briefly reviews the history of the development of fatigue testing methods, with respect to industrial needs. Moreover, it presents selected examples of solutions and applications systems for fatigue testing, available in scientific
PL
W artykule przedstawiono wybrane przykłady budowy i zastosowań stanowisk do badań zmęczeniowych tworzyw konstrukcyjnych. Autorzy dokonali przeglądu uniwersalnych maszyn zmęczeniowych i stanowisk testowych, jak również urządzeń stworzonych specjalnie dla indywidualnych programów badania własności zmęczeniowych materiałów. Autorzy opisują również, jak wdrożyć te procedury do układów sterowania i pomiarów w stanowiskach badawczych.. W artykule przedstawiono historię rozwoju metod badań zmęczeniowych w odniesieniu do potrzeb przemysłu. Ponadto zaprezentowano wybrane przykłady rozwiązań i ich aplikacji do badań zmęczeniowych, dostępnych w nauce.
EN
Occupational burnout is an increasingly common disorder occurring in various occupational groups, especially in uniformed services. The research was conducted among police officers. The research process involved 140 policemen selected using the snowball sampling method. The results obtained confirmed that the vast majority (80%) suffer from medium and high levels of occupational burnout. The highest level of burnout is observed in long-serving males working in the prevention department. Research results show that there is an urgent need to, first and foremost, design measures to prevent the process of occupational burnout from developing in this group of employees. These activities should mainly focus on preventive and therapeutic programmes aimed at both minimising the risk factors and reducing the excessive work-related mental strain.
EN
Pregnancy is a special period in the life of a woman and her family, resulting in biological, social and psychological changes. Each pregnancy, even one non-burdened with social and obstetric risk, is a stressful situation (Dulude et al, 2002). For each pregnancy, the obstetrician-patient relationship and the level of the woman's confidence in the obstetrician become important. Patient's trust is one of the components of the satisfaction with medical care, which is a determinant as to adherence to the doctor's recommendations, leading to better clinical effects of the health care itself (Kurpas, Sapilak, Steciwko, 2006). The aim of this study was to assess the obstetrician-patient relationship during pregnancy and the stress levels experienced in four groups of women, selected on the basis of their pregnancy - healthy pregnancy and high-risk pregnancy complicated by: a fetal factor, a maternal factor or both factors. The purpose of this study was to assess the relationship between stress and trust towards the obstetrician in the studied groups. The research was conducted on a total of 242 women applying for follow-up examinations to the obstetrician or staying in the department of pregnancy pathology. The following measurement methods were used in the research: Global Stress Scale PSS-10 and the Trust in Physician Scale. The analyses have shown significant differences among the studied groups regarding the assessment of the magnitude of stress experienced and the assessment of confidence level towards the obstetrician. The magnitude of stress was negatively correlated with the level of trust towards the obstetrician only in the group of women in high-risk pregnancy complicated by a fetal factor.
EN
The objective of the present article is to determine the negative changes that stress experienced by soldiers of participants in international missions may trigger in their functioning. It is assumed that these changes can be so extensive and intense that they will be able to limit the ability of soldiers to take action. Therefore, their participation in the international mission may be limited. This objective can be achieved by using methods of analysis and criticism of subject literature, as well as by induction and deduction. In the result of the carried analysis the author comes to the conclusion that stress can negatively affect the physical and psychological functioning of soldiers participating in international missions. Mission stressors can occur on the physical, cognitive, emotional, social and spiritual levels. They can trigger negative changes that are noticeable in the behaviour of soldiers. Furthermore they can also be so extensive that they can affect their ability to take combat action. The quoted research results are significant, as the description of how exactly the stress-induced negative changes in a single soldier can affect not only the safety of that individual, but also others, and thus the success of the entire mission.
PL
W artykule przedstawiono podstawy określania naprężeń pierwotnych w górotworze metodą hydroszczelinowania, w tym jej wersję najczęściej stosowaną w podziemnych kopalniach – metodę microfrac. Przedstawiono także opracowaną w Głównym Instytucie Górnictwa metodę NUHS wykorzystującą ukierunkowane hydroszczelinowanie skał. Metoda ta, w odróżnieniu do metody microfrac, umożliwia określenie pełnego tensora naprężenia. W artykule porzedstawiono przykład połączonego zastosowania obu metod w badaniach dla LW Bogdanka.
EN
The article presents the basics of determination of primary stresses in rock mass by hydro-fracturing, including its version most commonly used in underground mines - the microfrac method. NUHS method is also presented. The method, developed at Central Mining Institute, uses directed hydro-fracturing of rocks. This method, in contrast to the microfrac method, enables determination of the full stress tensor. The article presents an example of a combined application of both methods in research for LW Bogdanka.
PL
Artykuł omawia metodykę obliczeń pola elektromagnetycznego w transformatorze rozdzielczym, na podstawie którego są obliczane siły działające zarówno na część aktywną jak i na kadź transformatora. W obliczeniach magnetycznych i mechanicznych jest stosowana metoda elementów skończonych 3D z uwzględnieniem uwarstwionej struktury uzwojeń i rdzenia oraz ściśliwego oleju. Końcowym efektem obliczeń jest pole przemieszczeń i naprężeń mechanicznych.
EN
The article discusses the method of calculating the electromagnetic field in the distribution transformer, on the basis of which the forces acting on both the active part and on the transformer tank are calculated. In the magnetic and mechanical calculations, the 3D finite element method is applied, taking into account the laminar structure of the windings and the core as well as the compressible oil. The final effect of the calculations is the field of mechanical displacements and stresses.
EN
The article is devoted to solving the fundamental and applied problem of nonlinear structural me-chanics of machines by introducing into the drum two additional stop cylinders with supporting rollers at the end and adjustable length, providing a given elliptical or circular shape of a flexible shell with a smoothly variable geometry in the area of its contact with compacted pavement material. Compaction of soil, gravel and asphalt concrete in the sphere of road is not only an integral part of the technological process of the roadbed, road foundation and surface construction, but it is actually the main operation to ensure their strength, stability and durability. The quality, cost and speed of road construction, the possibility of using fundamentally new technologies, structures and materials is largely determined by the availability of modern road machinery.
EN
The lack of a common methodology on compaction theory stimulates developers of road construc-tion equipment to create various approximate methods for their calculation, the number of which, at the present time, is comparable with the nomenclature of the proposed designs of rollers. The article presents the analysis of the deformable shell behavior of a road roller, and the compacted material under its compacting roller, in a situation when a rigid circular shell of the roller is replaced by a forcefully deformable elliptical shape, which, unlike the circular design, allows variation, adjustment and optimization of the road roller impact on the material to be compacted.
EN
This paper discusses the design analysis of closed vessel (CV) for power cartridge application in water-jet disruptor. In this article, various design theories are presented in which the vessel is subjected to internal pressure. CV is a kind of pressure vessel utilized to evaluate the performance of power cartridge used for water-jet application. It is a test vessel which generates pressure - time profile by burning the propellant. Energy derived from burning of the propellant of power cartridge aids in neutralizing Improvised Devices (IED's). This energy creates high water-jet plume in the disruptor. In order to evaluate various performance parameters of the cartridge, CV design plays a vital role in the research and development activities, including, development, life trials, production, lot proof trials and life extension / life revision trials. CV is one of the methodologies / techniques from which energy generated is measured in terms of the maximum pressure (Pmax) and the time to maximum pressure (TPmax). This paper also discusses about various design aspects using the finite element method (FEM) and their comparative results with different design theories. In the light of these theoretical, numerical, and experimental works, it was recommended that octahedral stress theory or van Mises theory should be used for vessel design. This satisfies the designer requirements. FEM analysis tool helps in reducing time & development cost.
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