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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.
EN
In galleries digged for different type of uses, but mostly for extracting coal, hydrotechnical adduction galleries but also for tunnels, after the dislocation of the rocks is done, the tenssions in the rock changes massively. We take for example a metallic structure used as provisory structure until the rock pressure stabilize and used in Petroșani Romania, coal mines. The galleries are digged with explosives and the shockwave gives excessive cracks and disturb the rock pressure and its characteristics. The space between the metallic structure, rock walls and bolt is filled with wood, but this article suggests a rubber band material so the rock pressure to be distributed uniformly and not concentrated in the contact points between the wood and metal profile.
PL
W wyrobiskach wybranych do różnego rodzaju zastosowań, głównie do wydobycia węgla, budowli hydrotechnicznych, tuneli, po zakończeniu wydobycia skal napięcie w skale zmienia się ogromnie. Jako przykład pokazano stabilizowanie się ciśnienia w wyrobiskach w kopalni węgla Petroșani w Rumunii Eksploatacja jest prowadzona za pomocą materiałów wybuchowych, fala uderzeniowa powoduje nadmierne pęknięcia i zaburza ciśnienie w skałach. Przestrzeń między obudowa a górotworem metalową jest wypełniona drewnem, ale w tym artykule przedstawiono zastosowanie gumy dla uzyskania równomiernego nacisku skały.
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.
EN
A relation connecting stress intensity factors (SIF) with displacement intensity factors (DIF) at the crack front is derived by solving a pseudodifferential equation connecting stress and displacement discontinuity fields for a plane crack in an elastic anisotropic medium with arbitrary anisotropy. It is found that at a particular point on the crack front, the vector valued SIF is uniquely determined by the corresponding DIF evaluated at the same point.
5
EN
The problem of gap estimation for a break of a continuous welded rail is studied. The track is represented as a semi-infinite rod on elastic-based damping. Static and dynamic solutions are obtained. It is shown that during the rail break, the dynamic factor does not exceed 1.5. We derive equations for thermal deformation of the welded rail of jointless track on an elastic foundation in the presence of the insert into the base with another characteristic stiffness. It is shown that the presence of the insertion of up to 20% of the length of the rail, with both large and small stiffness, has a little effect on the stress-strain state (SSS) of the track. The presence of a rigid insert may increase the clearance of an accidental break of the rail, which has a negative effect on traffic safety.
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.
7
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.
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.
9
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
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.
PL
W artykule przedstawiono wyniki badań naprężeń wewnętrznych w szynach kolejowych i w zgrzewanych połączeniach szyn. Badano przebieg naprężeń w złączach szynowych po zgrzewaniu oraz po badaniach zmęczeniowych. W badaniach naprężeń zastosowano tensometryczną metodę niszczącą. Porównano kształtowanie się naprężeń w szynach oraz złączach szynowych wykonanych ze stali gatunku R260 oraz gatunku R350HT. Metodę pomiaru naprężeń oparto na wymaganiach zawartych w normie PN EN 13674-1:2011+A1:2017.
EN
Purpose: The aim of the study was to determine forces which are transferred to supporting teeth during the treatment with the midpalatal device with Hyrax screw and to evaluate orthodontic and orthopaedic effects based on displacement analysis. Design/methodology/approach: The finite element method (FEM) was used to simulation the midpalatal expansion forces activated by the screw pre-loaded during a turn of 180° which corresponds to daily recommended value. Distribution of expansion forces of Hyrax device was calculated as reaction forces on elastic supports with stiffness corresponding to the teeth working on periodontal ligament in alveolar bone. Findings: On the basis of the displacement analysis was observed the movement of supporting teeth by a value higher than 0.1 mm which corresponds to the recommended daily value. The midpalatal suture splitting forces were determined on the first premolars with a value of 32.8 N and on the first premolars of 44.2 N. Research limitations/implications: The studies did not take into account the shape of palate other craniofacial bones and their stiffness. Practical implications: Adjusting the stiffness of the device to degree of ossification midpalatal suture and teeth mobility. Searching for new solutions which eliminate the negative phenomenon of tilting teeth during the expansion of maxilla and recommending a surgically assisted techniques. Originality/value: The simulation confirmed that treatment with Hyrax screw gives a uniform expansion with values of forces corresponded to stiffness of premolar and molar teeth. The studies have indicated a possibility of tendency to tilting the supporting teeth what is a negative phenomenon.
PL
Przedstawiono rozwiązania analityczne wpływu pierwotnych i wtórnych efektów skurczu na stan naprężenia i odkształcenia w stalowo-betonowych belkach zespolonych. W belkach swobodnie podpartych skurcz betonu powoduje dodatkowe ugięcia oraz naprężenia, a w wieloprzęsłowych belkach statycznie niewyznaczalnych wtórne efekty skurczu betonu - dodatkowo powstanie wzbudzonych sił wewnętrznych.
EN
The article presents analytical solutions of the infuence of the primary and secondary effects of concrete shrinkage on stress and strain state in steel-concrete composite beams. In sigle-span simply supported beams shrinkage of concrete causes additional deflections and self-equilibrated stresses. In multi-span statically indeterminate beams the secondary effects of shrinkage also give rise to induced cross sectional forces.
EN
In the present paper, we have studied the temperature and pressure dependent creep stress analysis of spherical shell. The review is critical to enhance the warm resistance of spherical shells in high-temperature conditions. The effect of different parameters was studied and it was noticed that the parameter n has a significant influence on the creep stresses and strain rates. Creep stresses and strain rates are ascertained on the premise of summed up strain measures and Seth’s transition hypothesis. This investigation is completed to demonstrate the impacts of temperature on the creep stresses and strain rates in the spherical shell. The resulting quantities are computed numerically and depicted graphically. It has been watched that the spherical shell made of an incompressible material is on more secure side of configuration when contrasted with the shell made of a compressible material.
PL
W artykule przedstawiono metodę wyznaczania współczynnika działania karbu w oparciu o metodę elementów skończonych, ze szczególnym uwzględnieniem złączy spawanych oraz ocenę jej przydatności dla miejsc monitorowanych ustroju nośnego koparki SchRs 4000.
EN
The article presents a method of determining an action coefficient of notch based on the finite element method, with particular emphasis on welded joints, and an assessment of its suitability for monitored locations of the BWE SchRs 4000 load bearing structure.
EN
Tension roofs based on cable systems are suitable for covering long span buildings. Such structures are considered to be economic, modern and aesthetic solutions in various multi-functional arenas. Development of materials and construction technologies resulted in an increased number of applications of cable systems in recent years. However, the origin of such structures dates back to 1953, when the cable net supported roof over Raleigh Arena in North Carolina was completed. Designed as self-balanced, the system was eventually pretensioned in order to provide greater stiffness. This implementation became an indispensable part of cable nets construction. A unique method of pretension was applied in one of the first and most recognizable Polish examples of tensile structure, which is the cable net roof over the open-air theater in Koszalin. The system was pretensioned through the outward rotation of simply supported edge arches, which induced tensile forces in roof cables. This simple and effective concept became an inspiration for the introduced study, which focused on the numerical application of such a solution. In this paper, the results of comparative finite element analysis of introduced cable net structure with different methods of pretensioning are presented. The investigation was preceded by the analysis of net shape, concentrated on the value of cable sags in the saddle point of parabolic hyperboloid surface. Effectiveness of the presented solutions was assessed through comparison of internal forces distribution and model deformation. Numerical verification of consecutive concepts led to a gradual reduction of directly prestressed members from 16 suspension cables to 6 cable stays in the analysed roof.
19
Content available remote Stress field determination based on digital image correlation results
EN
The aim of this work was to determine the stress distribution during plastic deformation, based on the displacement field obtained using the digital image correlation (DIC) method. To achieve stress distribution, the experimentally measured displacement gradient and the elastoplastic material model with isotropic hardening were used. The proposed approach was implemented in the ThermoCorr program. The developed procedure was used to determine stress fields for uniaxial tension and simple shear processes, carried out on samples made of austenitic steel 304L. Both material parameters, such as the Young's modulus, Poisson's ratio, yield stress, and parameters of the hardening curve, were acquired experimentally. The macroscopic force obtained from the DIC-based stresses and its finite element analysis (FEA) equivalent were compared with that measured during the experi- ment. It was shown that the DIC-based approach gives more accurate results with respect to FEA, especially for a simple shear test, where FEA significantly overestimates the value of experimentally obtained macroscopic force.
EN
The article explores the stress-strain state of the pneumatic flexible shaft coupling of the tumbling mill drive using a software of finite element analysis. The study has revealed that the stress-strain state of the pneumatic flexible shaft coupling is characterized by an uneven general and local distribution of stresses. Areas of maximum stress and strain in the pneumatic flexible shaft coupling have been defined. The study allowed for changing the geometry and reducing the mass of the disc of the pneumatic flexible shaft coupling with a slight change in stresses and strains. The results of the study can be applied to the design of pneumatic flexible shaft couplings and serve as a basis for further research.
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