scholarly journals Creep study of carcass composites reinforced with steel fiber of the Dramix type

2019 ◽  
Vol 6 (4) ◽  
Author(s):  
Vitaliy Lesnov
Keyword(s):  
Bending Strength ◽  
Steel Fiber ◽  
Initial Section ◽  
Linear Increase ◽  
Point Scheme ◽  
Curved Section ◽  
Strength And Stiffness ◽  
The Moment ◽  
Kinetics Of ◽  
Control Composition

The results of a creep study of disperse-reinforced building composites made by carcass technology are presented. In the experiment, steel fiber «Dramix» type fiber was used as dispersed reinforcement, the content of which was 1…3 % by volume of the composite. The impregnation matrix was made on the basis of portlandcement and a superplasticizing additive of the brand Melflux 1641 F. In the creep test, the samples-beams were loaded according to a 4-point scheme. The level of load applied to the samples was 30, 50 and 70 % of the maximum values. An unreinforced carcass composite was taken as a control composition. The tests continued until the moment when the value of the deflection became constant. Based on the data obtained, graphical dependencies «relative deflection – exposure time» were constructed. On the obtained creep curves of carcass composites in the general case, four sections of the kinetics of deflection change can be distinguished: the initial section, in which an intense, almost linear, increase in deflections occurs; the curved section where the attenuation of the process of growth of deflections is observed; a linear section in which the increase in deflections is insignificant and has a quasi-permanent character; the final section, when the stabilization of the deflections occurs, and their values become constant. The minimum deflection values were obtained for an unreinforced carcass composite, and the maximum for composite reinforced with 1 % «Dramix» fiber. When the composition of the carcass composites contains 2–3 % fiber, a significant decrease in the deflections was observed, but their values were higher than that of the control composition. This is explained by the different load applied to the reinforced and unreinforced samples of carcass composites, as well as the positive effect of increasing the content fiber to 2–3 % on their bending strength and stiffness. The studied dispersion-reinforced carcass composites can be used for the manufacture of monolithic industrial floors, foundations and pavements, working under the influence of increased mechanical influences.

In Situ Preparation and Mechanical Properties of (ZrB2+ZrC)/Zr3[Al(Si)]4C6 Composites

2014 ◽  
Vol 602-603 ◽  
pp. 438-442
Author(s):  
Lei Yu ◽  
Jian Yang ◽  
Tai Qiu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Bending Strength ◽  
Coefficient Of Thermal Expansion ◽  
Raw Materials ◽  
Linear Increase ◽  
Fine Grain ◽  
Fine Grain Strengthening ◽  
Uniform Microstructure

Fully dense (ZrB2+ZrC)/Zr3[Al (Si)]4C6 composites with ZrB2 content varying from 0 to 15 vol.% and fixed ZrC content of 10 vol.% were successfully prepared by in situ hot-pressing in Ar atmosphere using ZrH2, Al, Si, C and B4C as raw materials. With the increase of ZrB2 content, both the bending strength and fracture toughness of the composites increase and then decrease. The synergistic action of ZrB2 and ZrC as reinforcements shows significant strengthening and toughing effect to the Zr3[Al (Si)]4C6 matrix. The composite with 10 vol.% ZrB2 shows the optimal mechanical properties: 516 MPa for bending strength and 6.52 MPa·m1/2 for fracture toughness. With the increase of ZrB2 content, the Vickers hardness of the composites shows a near-linear increase from 15.3 GPa to 16.7 GPa. The strengthening and toughening effect can be ascribed to the unique mechanical properties of ZrB2 and ZrC reinforcements, the differences in coefficient of thermal expansion and modulus between them and Zr3[Al (Si)]4C6 matrix, fine grain strengthening and uniform microstructure derived by the in situ synthesis reaction.

Structural Behaviour of Blind Bolted Connection to Concrete-Filled Steel Tubular Columns

2010 ◽  
Vol 163-167 ◽  
pp. 591-595
Author(s):  
Jing Feng Wang ◽  
Xin Yi Chen ◽  
Lin Hai Han
Keyword(s):  
Analysis Model ◽  
Bolted Connections ◽  
Structural Behaviour ◽  
Tubular Columns ◽  
End Plate ◽  
Moment Resisting ◽  
Strength And Stiffness ◽  
Plate Connections ◽  
The Moment ◽  
Plate Connection

This paper studies structural behaviour of the blind bolted connections to concrete-filled steel tubular columns by a serial of experimental programs, which conducted involving eight sub-assemblages of cruciform beam-to-column joints subjected to monotonic loading and cyclic loading. The moment-rotation hysteretic relationships and failure models of the end plate connections have been measured and analyzed. A simplified analysis model for the blind bolted connections is proposed based on the component method. It is concluded that the blind bolted end plate connection has reasonable strength and stiffness, whilst the rotation capacity of the connection satisfies the ductility requirements for earthquake-resistance in most aseismic regions. This typed joint has excellent seismic performance, so it can be used in the moment-resisting composite frame.

scholarly journals On mechanism of the bubble bouncing from hydrophilic and hydrophobic solid surfaces

2015 ◽  
Vol 70 (1) ◽  
Author(s):  
Jan Zawała ◽  
Piotr Zawała ◽  
Kazimierz Małysa
Keyword(s):  
Liquid Film ◽  
Solid Surfaces ◽  
Deformation Degree ◽  
Bubble Deformation ◽  
Surface Time ◽  
The Moment ◽  
Highly Hydrophobic ◽  
Energy Dissipated ◽  
Bubble Collision ◽  
Kinetics Of

AbstractThe kinetics of collision and bouncing of an air bubble on hydrophilic and hydrophobic solid surfaces immersed in distilled water is reported. We carried out the experiments and compared the bubble collision and bouncing courses on the stagnant and vibrating, with a controlled frequency and amplitude, solid/liquid interface. For stagnant interface differences in the outcome of the bubble collisions with hydrophilic and hydrophobic solid surfaces are resulting from different stability of the intervening liquid film formed between the colliding bubble and these surfaces. The liquid film was unstable at Teflon surface, where the three-phase contact (TPC) and the bubble attachment were observed, after dissipation of most of the kinetic energy associated with the bubble motion. For vibrated solid surface it was shown that kinetics of the bubble bouncing is independent on the hydrophilic/hydrophobic properties of the surface. Similarly like at water/glass hydrophilic interface, even at highly hydrophobic Teflon surface time of the bubble collisions and bouncing was prolonged almost indefinitely. This was due to the fact that the energy dissipated during the collision was re-supplied via interface vibrations with a properly adjusted acceleration. The analysis of the bubble deformation degree showed that this effect is related to a constant bubble deformation, which determined constant radius of the liquid film, large enough to prevent the draining liquid film from reaching the critical thickness of rupture at the moment of collision. The results obtained prove that mechanism of the bubble bouncing from various interfaces depends on interrelation between rates of two simultaneously going processes: (i) exchange between kinetic and surface energies of the system and (ii) drainage of the liquid film separating the interacting interfaces.

Kinetics of Mixed Low-Level Waste Incapsulation Using Iron Phosphate Chemically Bonded Cement

2006 ◽  
Vol 932 ◽  
Author(s):  
A.S. Aloy ◽  
T.I. Koltsova ◽  
E.N. Kovarskaya ◽  
M.Yu. Silin
Keyword(s):  
Formation Process ◽  
Iron Phosphate ◽  
Structural Formation ◽  
Low Level ◽  
Second Stage ◽  
Bivalent Iron ◽  
Acid Reaction ◽  
The Moment ◽  
Two Stages ◽  
Kinetics Of

ABSTRACTThe iron phosphate cement (IPC) structure formation process has been studied by Mossbauer spectroscopy. The IPC is formed as a result of interaction of iron oxides with orthophosphoric acid and could be used as a matrix for immobilization of low-level radioactive waste.The structural formation process has been shown may be considered to consist of two stages. The first stage lasts to the moment of setting, when the diffusion process goes on in the liquid phase. At this stage the main fragments of the structural polymeric frame of the IPC are developed consisting of iron (+2) and (+3) phosphates. The rate of the oxides-with-phosphoric-acid reaction as well as the time of hardening depends on the bivalent iron content.The second stage begins from the moment of setting when the diffusion becomes slower. At this stage the process is characterized by the negligible increase in the iron phosphates (+2), (+3) content and transformation of the previously formed phosphates.The nuclear gamma-resonance (NGR) parameters have been determined of FeH3(PO4)2·2.5H2O, forming in the hematite (Fe2O3) based IPC: isomeric shift (IS) = 0.46 mm/s, quadrupole splitting (QS) = 0.197 mm/s, FWHM =0.282 mm/s.

scholarly journals On certain correction terms required in the equations for the kinetics of simple hœmolysis

1932 ◽  
Vol 110 (765) ◽  
pp. 1-17 ◽  
Keyword(s):  
Photoelectric Cell ◽  
Photoelectric Current ◽  
Cell Method ◽  
High Tension ◽  
Satisfactory Method ◽  
The Moment ◽  
The Right ◽  
Correction Terms ◽  
Kinetics Of ◽  
Made In

The most satisfactory method hitherto available for the measurement of percentage hœmolysis has been the potassium cell method described in an earlier paper (Ponder and Yeager, 1930). This method, however, has certain limitations and disadvantages, two of which are particularly conspicuous. (i) The galvanometer which records the photoelectric current takes several seconds to deflect, and several seconds more to settle at zero. This determines that no more than four readings of the degree of hœmolysis can be made in a minute, and that only a few points can be obtained on the percentage hœmolysis curve for rapidly hœmolysing systems. Even these points, moreover, are apt to be inaccurate, for lysis is going on during the time taken for the galvanometer to move ; the degree of lysis recorded is thus always greater than that really present at the moment the photoelectric cell first receives the light. The effect is to move the percentage hœmolysis curve over to the right by a distance corresponding to about 0-05 minutes ; this shift is of little consequence if lysis is slow, but may introduce considerable error if it is rapid. (ii) The method is unreliable in the sense that its efficiency depends on factors which are controlled with difficulty and which are liable to vary. Photoelectric fatigue, although usually absent, may appear during any experiment, the voltage of the high tension battery or of the accumulator which supplies the lamp may vary, or the potassium cell may glow as a result of a careless exposure to the light in the interval before the cells are added to the lysin in the chamber. Experience shows that these accidents often happen, and the necessity of being continually on one’s guard against them makes the measurement of percentage hœmolysis much more difficult than would appear at first sight.

scholarly journals The catalytic decomposition of nitrous oxide on the surface of gold: a comparison with the homogeneous reaction

1925 ◽  
Vol 108 (745) ◽  
pp. 211-215 ◽  
Keyword(s):  
Nitrous Oxide ◽  
Catalytic Decomposition ◽  
Bimolecular Reaction ◽  
Homogeneous Reaction ◽  
Gaseous Reaction ◽  
Measurable Velocity ◽  
Rare Class ◽  
The Moment ◽  
Kinetics Of ◽  
Decomposition Of Nitrous Oxide

The bimolecular reaction 2N 2 O = 2N 2 + 2N 2 was recently shown to belong to the rather rare class of homogeneous reactions. Decomposition of two molecules of nitrous oxide takes place when a collision of a certain critical degree of violence occurs in the gas. At the moment of collision the two molecules must possess a combined energy of at least 58,000 calories (per 2 gram molecules), and it is probable that most of the collision in which this condition is fulfilled are fruitful. A comparison between the kinetics of this homogeneous decomposition and the corresponding reaction proceeding catalytically at the surface of a solid might be expected to throw light on the mechanism of heterogeneous catalysis. Previous efforts ( loc. cit .) to accelerate the reaction catalytically by the introduction of metals into the bulb in which the homogeneous reaction was going on were fruitless, since the reaction, if any, which took place at the surface of the metal was slow in camparison with the gaseous reaction. This difficulty was overcome by using as a catalyst a fine metal wire heated electrically. This could be raised to a sufficiently high temperature to cause the surface reaction to proceed with measurable velocity while the bulk of the gas was kept cold, thus eliminating the homogeneous reaction. Experiments made with platinum wires in this way were successful. The kinetics of the decomposition of nitrous oxide on the surface of platinum are summarized in the equation – d [N 2 O]/ dt = k [N 2 O]/1 + b [O 2 ]. The reaction is unimolecular, but is complicated by the strong retarding action of the oxygen formed.

Experimental Research on Seismic Behavior of Interior Joints of Specially Shaped Columns Reinforced by Fiber

2011 ◽  
Vol 94-96 ◽  
pp. 551-555 ◽  
Author(s):  
Xian Rong ◽  
Jian Xin Zhang ◽  
Yan Yan Li
Keyword(s):  
Energy Dissipation ◽  
Bearing Capacity ◽  
Seismic Behavior ◽  
Steel Fiber ◽  
Polypropylene Fiber ◽  
The Core ◽  
Low Cyclic Loading ◽  
The Moment ◽  
Specially Shaped Column ◽  
Damage Characteristic

Based on the low cyclic loading experiments on three interior joints with specially shaped columns, in which one of them was reinforced by polypropylene fiber in the core zone of joint, another steel fiber, the other was not reinforced, the authors compare the results in terms of damage characteristic, bearing capacity, displacement and ductility, hysteretic curve of the moment-rotation, rigidity degradation and energy dissipation. It is shown that seismic behavior of specially shaped column interior joints reinforced by fiber is improved significantly. The interior joint of specially shaped column reinforced by polypropylene fiber has a better damage characteristic and energy dissipation while that by steel fiber shows a higher yield load and bearing capacity.

scholarly journals Effectiveness and Subjectivity of Visual Inspection as a Method to Assess Bending Stiffness and Strength of Chestnut Elements

2013 ◽  
Vol 778 ◽  
pp. 175-182 ◽  
Author(s):  
Hélder S. Sousa ◽  
Jorge M. Branco ◽  
Paulo B. Lourenço
Keyword(s):  
Visual Inspection ◽  
Bending Strength ◽  
Castanea Sativa ◽  
Bayesian Probability ◽  
Maximum Diameter ◽  
Visual Grading ◽  
Bending Tests ◽  
Coefficients Of Variation ◽  
Strength And Stiffness

Besides the difficulty of assessing an existing timber structure on site, the efficiency and accuracy of visual inspection is often compromised by its subjective nature inherited by the level of expertise of the inspector. This often leads to conservative predictions of the mechanical properties, even with the use of specific visual grading norms. The main objectives of this work are to assess the effectiveness of visual inspection as a method to define different classes of strength and stiffness and to provide a statistical analysis on its subjectivity. For that aim, visual inspection using Italian standard UNI 11119:2004 and bending tests of 20 old chestnut beams (Castanea sativa Mill.) at different scale element, were carried out. Comparisons and effectiveness of visual inspection is analyzed within and between different scales of the timber members, and also regarding different level of expertise of inspectors. The results evidence similar percentages of segments classified with higher and lower visual inspections classes and proved to be a good qualitative indicator of bending strength between sawn beams. An overall 42% accuracy of the most experienced inspectors was found with better differentiation between visual classes, whereas lower level inspectors scored approximately less 5%. Lower level inspectors also evidenced higher concentration of values around a higher mean for each class denoting a more conservative approach. Regardless of the inspector level, knot size was considered the main limiting visual parameter with higher influence in small scales of the timber elements. When studying the characterization of a single knot, coefficients of variation of 15.7% and 21.8% were found for measuring the minimum and maximum diameter. Bayesian probability networks were considered as to individually assess the accuracy in stiffness prediction of different level of inspectors, and by combination of their information, evidencing that parallel combination for prior information may allow the increase in visual inspection accuracy.

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