Search results for "creep"
showing 10 items of 167 documents
Mechanical properties and XRD of Nafion modified by 2-hydroxyethylammonium ionic liquids
2013
In this work, the Nafion 112 membrane impregnated with 2-hydroxyethylammonium carboxylate ionic liquids have been investigated. The used ionic liquids were 2-hydroxyethylammonium formate [HEA]F, acetate [HEA]A and lactate [HEA]L. Prepared composite membranes Nafion/ionic liquid are characterized by mechanical testing, such as tensile test and creep test. It is found that ionic liquids decrease elastic modulus and creep compliance, but do not have significant effect on the tensile strength. Also, composite membranes were studied by wide angle X-ray diffraction. All ionic liquids shift the peak maximum to the lower angle. In this work, only biodegradable ionic liquids were used for composite …
RC column externally strengthened with RC jackets
2013
In this paper the behaviour in compression of RC columns externally strengthened with concrete jacketing is analysed and a cross-section analysis of the jacketed member under axial load and bending moment is developed. The focus was to study the effect of confinement of concrete jacket on concrete core and the behaviour of compressed bars with buckling effects. Some other important aspects such as shrinkage, creep, old to new concrete surfaces and bond split effects were not included in the model because: the use of thick non-shrink grout jacket and a well-roughened surface of old-to-new concrete was supposed; long term effects were included though corrective coefficients for monolithic beh…
Temperature and magnetic-field dependence of quantum creep in various high-Tcsuperconductors
1999
To investigate the quantum tunneling of almost macroscopic vortex segments we measured the normalized relaxation rate Q of superconducting currents for various high-T{sub c} superconductors (HTS's) down to 100 mK in magnetic fields up to 7 T. At fields below {approx_equal}0.5 T, Q is essentially independent of T in the temperature regime between thermally activated and quantum motion as theoretically expected. However, at higher fields, we find an unexpected linear T dependence of Q persisting down to the lowest temperatures in all investigated samples. Since these compounds were chosen to represent the distinct classes of dirty and clean HTS's, the extrapolated Q(T=0) values are used to di…
Effect of ageing on the morphology and creep and recovery of polymer-modified bitumens
2018
Polymer additives are used to improve the properties of road bitumens including their oxidative resistance. However, their usage as anti-oxidative materials remains relatively unclear. This study aims to investigate the changes in the morphology and the rheological response of polymer modified bitumens used in road pavement construction caused by ageing. An elastomer (radial styrene butadiene styrene, SBS) and a plastomer (ethyl vinyl acetate, EVA) polymer were mixed with one base bitumen at three polymer concentrations. The bitumens were RTFO and PAV aged. The morphology of the bitumens was captured by fluorescence microscopy while the rheological properties were measured by means of the m…
Influence of the Mean Load Value in Fatigue Block Loading on Strains
2014
This paper presents the results of the fatigue tests of the specimens made from S3555 steel and aluminum alloy AlCu4MgSi subjected to bending block loading with mean load value. The influence of the changes of the mean load conditions was investigated. During the tests strains were registered and relation between the load and the strains was analyzed. In the case of S355 steel it was observed, that additional hardening occurs when higher value of the mean load is applied at the beginning of the block loading. Other case, when the mean load was increased from zero to maximum, a creep effect of the material was registered. For the specimens made from aluminum alloy similar processes were not …
A micro-mechanical model for grain-boundary cavitation in polycrystalline materials
2015
In this work, the grain-boundary cavitation in polycrystalline aggregates is investigated by means of a grain-scale model. Polycrystalline aggregates are generated using Voronoi tessellations, which have been extensively shown to retain the statistical features of real microstructures. Nucleation, thickening and sliding of cavities at grain boundaries are represented by specific cohesive laws embodying the damage parameters, whose time evolution equations are coupled to the mechanical model. The formulation is presented within the framework of a grain-boundary formulation, which only requires the discretization of the grain surfaces. Some numerical tests are presented to demonstrate the fea…
Thermo-mechanical analyses and ways of optimization of the helium cooled DEMO First Wall under RCC-MRx rules
2017
Abstract The EUROfusion Consortium develops a design of a fusion power demonstrator plant (DEMO) in the framework of the European “Horizon 2020” innovation and research program. One of the key components in the fusion reactor is the Breeding Blanket (BB) surrounding the plasma, ensuring tritium self-sufficiency, heat removal for conversion into electricity, and neutron shielding. Among the 4 candidates for the DEMO BB, 2 of them use helium as coolant (HCPB, HCLL), and another one (DCLL) uses helium to cool down the First Wall (FW) only. Due to uncertainties regarding the plasma Heat Flux (HF) load the DEMO BB integrated FW will have to cope with, a set of sensitive thermal and stress analys…
LARGE DEFORMATION CREEP BEHAVIOR OF A SOLID POLYMER.
1981
Abstract The effect of loading rate and strain on the creep behavior after sample yielding has been studied in previous communications (14–15) for Mylar in tension and for Lexan in compression. In this work the creep behavior of Lexan samples previously elongated is considered both in tension and in compression. A procedure which collects all the data independently of both loading rate and initial creep strain is proposed.
Food availability and the male's role in parental care in double-brooded TreecreepersCerthia familiaris
1996
The aim of this work was to examine differences in paternal and maternal care in a double-brooded, monogamous species, the Treecreeper Certhia familiaris, in relation to food availability. As a measure of parental care, we recorded the hourly feeding activity of parents when the nestlings from their first and second breeding attempts were 7 and 12 days old. Feeding frequency of the first brood increased with the age of the nestlings and also with the brood size when 12 days old. While the feeding activities of the females were similar with respect to the first and second broods, the males were less active and failed to provide any food to their nestlings in 15 cases out of 28 second broods.…
Effects of male removal on female foraging behavior in the Eurasian treecreeper
1997
In old, spruce-dominated forests of central Finland, Eurasian treecreepers Certhia familiaris divide their territories spatially during the breeding season. Females forage primarily on the upper parts of the tree trunks, while males use the lower parts of the tree trunks. In this study we removed males from eight territories in the early nestling period to see if the mate's absence would change the foraging patterns of the resident female. Widowed females foraged at lower heights, thus behaving more like paired males. These females also spent less time on each tree and on each foraging bout than did paired females. We conclude that male removal facilitated the change in a female's foraging …