Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

scholarly journals Effects of High Temperatures on the Physical and Mechanical Properties of Carbonated Ordinary Concrete

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Qifang Xie ◽  
Lipeng Zhang ◽  
Shenghua Yin ◽  
Baozhuang Zhang ◽  
Yaopeng Wu
Keyword(s):  
Mechanical Properties ◽  
Weight Loss ◽  
Elastic Modulus ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Physical And Mechanical Properties ◽  
Surface Characteristics ◽  
Time Service ◽  
Different Temperatures ◽  
Cooling Methods

Fires are always known for seriously deteriorating concrete in structures, especially for those with certain carbonation due to long-time service. In this paper, 75 prism specimens were prepared and divided into four groups (three carbonated groups and one uncarbonated group). Specimens were tested under different temperatures (20, 300, 400, 500, 600, and 700°C), exposure times (3, 4, and 6 hours), and cooling methods (water and natural cooling). Surface characteristics, weight loss rate, and residual mechanical properties (strength, initial elastic modulus, peak, and ultimate compressive strains) of carbonated concrete specimens after elevated temperatures were investigated and compared with that of the uncarbonated ones. Results show that the weight loss rates of the carbonated concrete specimens are slightly lower than that of the uncarbonated ones and that the cracks are increased with raising of temperatures. Surface colors of carbonated concrete are significantly changed, but they are not sensitive to cooling methods. Surface cracks can be evidently observed on carbonated specimens when temperature reaches 400°C. Residual compressive strength and initial elastic modulus of carbonated concrete after natural cooling are generally larger than those cooled by water. The peak and ultimate compressive strains of both carbonated and uncarbonated concrete specimens increase after heating, but the values of the latter are greater than that of the former. Finally, the constitutive equation to predict the compressive behaviors of carbonated concrete after high temperatures was established and validated by tests.

Diffusion of Ti, V and Nb in Ni3Al at Elevated Temperatures

2010 ◽  
Vol 297-301 ◽  
pp. 384-389 ◽  
Author(s):  
Haruhiko Fukaya ◽  
Md. Moniruzzaman ◽  
Yoshinori Murata ◽  
Masahiko Morinaga ◽  
Toshiyuki Koyama ◽  
...  
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficients ◽  
Binary Systems ◽  
Elevated Temperatures ◽  
Diffusion Mechanism ◽  
Impurity Diffusion ◽  
Diffusion Couples ◽  
Different Temperatures ◽  
Series Of Experiments ◽  
Interdiffusion Coefficients

Interdiffusion coefficients of Al replacing elements in Ni-Al-X (X=Ti, V and Nb) were estimated by a series of experiments using diffusion couples of Al rich pseudo-binary systems at three different temperatures of 1423, 1473 and 1523K. In order to obtain interdiffusion coefficients of the pseudo-binary systems, the experimental data was analyzed by the Sauer and Freise method, and also impurity diffusion coefficients of Ti, V and Nb in Ni3Al were estimated by applying the Darken-Manning equation. The magnitude of interdiffusion coefficient decreased in order of V, Ti and Nb at all three temperatures. Impurity diffusion coefficients were described by the expressions: , , . The activation enthalpies obtained from the experimental data confirmed the retardation of Ti, V and Nb diffusion in Ni3Al by the anti-site diffusion mechanism. These results are consistent with our previous work on diffusion of Re and Ru in Ni3Al .

Isothermal modeling of sand–bentonite mixtures at elevated temperatures

1995 ◽  
Vol 32 (1) ◽  
pp. 78-88 ◽  
Author(s):  
B.E. Lingnau ◽  
J. Graham ◽  
N. Tanaka
Keyword(s):  
Shear Strength ◽  
Elevated Temperatures ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Compression Tests ◽  
Strain Behavior ◽  
Bentonite Buffer ◽  
State Boundary ◽  
Increasing Temperature ◽  
Triaxial Compression Tests

Two models are proposed for describing the stress–strain behavior of sand–bentonite (buffer) mixtures at elevated temperatures: (1) isothermal pseudoelasticity and (2) isothermal elastic-plasticity. Data to support the models come from consolidated undrained triaxial compression tests performed on dense saturated buffer specimens at effective confining stresses up to 9.0 MPa and temperatures of 26°, 65°, and 100 °C. Measurements indicate that volumes decrease with increasing temperature if the tests are carried out under drained conditions. These trends can be modelled by a family of hardening lines in semilog compression space. Power law relationships are presented for undrained shear-strength envelopes that increase in size with an increase in temperature. The slopes of unload-reload lines, κ, in semilog compression space vary with temperature and can be related to systematic variation in the friction angle [Formula: see text]. The shear modulus G50 at 50% peak strength also depends on temperature. Several plotting techniques are used to show the existence of different state boundary surfaces for each test temperature. Key words : sand–bentonite, buffer, compression, shear strength, temperature, modelling.

BACKGROUND OF MODERN TECHNIQUES FOR LABORATORY DETERMINATION OF THE ELASTICITY MODULUS OF COHESIVE SOILS AND THEIR DESIGN CHARACTERISTICS IN THE ROAD STRUCTURE (Part 2)

2020 ◽  
Author(s):  
Anatolii Lytvynenko
Keyword(s):  
Elastic Modulus ◽  
Water Saturation ◽  
Relative Deformation ◽  
Compression Tests ◽  
The Road ◽  
Structured Soils ◽  
Modulus Of Deformation ◽  
Saturation Factor ◽  
Increase Productivity ◽  
Design Characteristics

According to the results of laboratory stamping tests, samples (d = 150mm; H=180mm) of bulk with soil compaction having a water saturation factor Sr≥0,85 in the range of values of fluidity index – 0,5≤lℓ≤0,25 , it is concluded that it is possible to determine practically every sample, their modulus of deformability (Епр; Ед), the calculated critical resistance – Ro of soil and its maximum relative deformation λmax. The loading of the samples is carried out by a step load with a proportional (1.3 times) increased pressure, such as at each stage. During the test, the sample is not unloaded but is subject to conditional destruction, that is, a disproportionate increase in the deposits of the die. The duration of each load is three minutes. The graphs of parabolic functions of the type λ=aσb are plotted in logarithmic coordinates in the form of two segments straight on both sides of the fracture. The parameter of the degree of parabola “b” serves for preliminary estimation of the index of deformability: for the modulus of elasticity – b≈1,0 ± 0,2; for the modulus of deformation – b≈2,0 ± 0,5; for the yield modulus – b≥3.0. The work gives a comparison with similar indicators of deformability of other building and structural materials. The elastic modulus (Епр) has only a soil that meets the conditions of the standard seal ρdmax>ρdωρ і ω_o<ωρ; the modulus of deformation (Ед) has a soil when 0<lℓ<0,5, and the modulus of fluidity (Ет) has only a soil lℓ≥0,5. Natural structured soils are characterized by a modulus of structural strength (Est) in the range 0<lℓ< 0, which is determined by compression tests. In order to reduce soil consumption and increase productivity, it is proposed to consider the task of determining soil deformability indices for the calculation of road clothing as a contact and therefore reduce the height of soil samples from 180 mm to 40 mm Keywords: soil, soil engineering structure, compacted soil, design condition, elastic modulus, critical design resistance, maximum relative deformation.

BACKGROUND OF MODERN TECHNIQUES FOR LABORATORY DETERMINATION OF THE ELASTICITY MODULUS OF COHESIVE SOILS AND THEIR DESIGN CHARACTERISTICS IN THE ROAD STRUCTURE (Part 1)

2019 ◽  
pp. 47-51
Author(s):  
Anatolii Lytvynenko
Keyword(s):  
Elastic Modulus ◽  
Water Saturation ◽  
Relative Deformation ◽  
Compression Tests ◽  
The Road ◽  
Structured Soils ◽  
Modulus Of Deformation ◽  
Saturation Factor ◽  
Increase Productivity ◽  
Design Characteristics

According to the results of laboratory stamping tests, samples (d = 150mm; H=180mm) of bulk with soil compaction having a water saturation factor Sr≥0,85 in the range of values of fluidity index – 0,5≤lℓ≤0,25 , it is concluded that it is possible to determine practically every sample, their modulus of deformability (Епр; Ед), the calculated critical resistance – Ro of soil and its maximum relative deformation λmax. The loading of the samples is carried out by a step load with a proportional (1.3 times) increased pressure, such as at each stage. During the test, the sample is not unloaded but is subject to conditional destruction, that is, a disproportionate increase in the deposits of the die. The duration of each load is three minutes. The graphs of parabolic functions of the type λ=aσb are plotted in logarithmic coordinates in the form of two segments straight on both sides of the fracture. The parameter of the degree of parabola “b” serves for preliminary estimation of the index of deformability: for the modulus of elasticity – b≈1,0 ± 0,2; for the modulus of deformation – b≈2,0 ± 0,5; for the yield modulus – b≥3.0. The work gives a comparison with similar indicators of deformability of other building and structural materials. The elastic modulus (Епр) has only a soil that meets the conditions of the standard seal ρdmax>ρdωρ і ωo<ωρ; the modulus of deformation (Ед) has a soil when 0<lℓ<0,5, and the modulus of fluidity (Ет) has only a soil lℓ≥0,5. Natural structured soils are characterized by a modulus of structural strength (Est) in the range 0<lℓ< 0, which is determined by compression tests. In order to reduce soil consumption and increase productivity, it is proposed to consider the task of determining soil deformability indices for the calculation of road clothing as a contact and therefore reduce the height of soil samples from 180 mm to 40 mm Keywords: soil, soil engineering structure, compacted soil, design condition, elastic modulus, critical design resistance, maximum relative deformation.

Simulation of the Elastic Modulus of Mo Alloys at Both Room and High Temperatures

2013 ◽  
Vol 785-786 ◽  
pp. 81-85 ◽  
Author(s):  
Hui Chao Cheng ◽  
Jing Lian Fan ◽  
Min Song
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Constitutive Model ◽  
Elevated Temperatures ◽  
Tensile Deformation ◽  
Dominant Mechanism ◽  
Sem Image ◽  
Average Grain Size ◽  
Predicted Values ◽  
Evolution Trend

In this paper, the elastic modulus of a kind of carbide strengthened Mo alloy has been investigated at both room and elevated temperatures. OM image showed that the sintered Mo alloy has an average grain size of ~20 μm. SEM image of the fracture surface of the sintered Mo alloy after tensile deformation to facture showed that intergranular fracture is the dominant mechanism during deformation. A constitutive model has been developed to simulate the elastic modulus of Mo alloys at both room and elevated temperatures. It has been shown that the evolution trend of the elastic modulus predicted by the constitutive model broadly agrees with the experimental counterparts, although most predicted values are slightly higher than the experimental data. The relatively lower experimental data are due to the pores in the Mo alloy, resulted from powder metallurgy fabrication process.

Two Approaches to the Study of Temperature Effect on the Dissipative Properties of Materials

2022 ◽  
Vol 906 ◽  
pp. 69-76
Author(s):  
Tigran Petrosyan
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Effect Of Temperature ◽  
Energy Losses ◽  
Temperature Function ◽  
Temperature Changes ◽  
Different Temperatures ◽  
Theory Equation ◽  
Instantaneous Deformation ◽  
Properties Of Materials

In order to study the effect of temperature changes on the dissipative properties of materials, two approaches are used. The first approach implies introducing some temperature function under the sign of the integral in the heredity theory equation and simultaneously taking into account the dependence of the elastic modulus on temperature. As a result, based on experimental data on the thermal creep of soils, the expression for determining the hysteresis energy losses under the periodic voltage changes was obtained depending on temperature changes.According to the second approach, the expression for determining the hysteresis energy losses under isothermal conditions at different temperatures was obtained by introducing into the heredity theory equation an approximation of the experimental dependences of instantaneous deformation and temperature creep parameters for steel Kh18 N10T.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

Improvement Of Curvilinear Diagrams Of Concrete Deformation

2019 ◽  
pp. 99-104
Keyword(s):  
Reinforced Concrete ◽  
Peak Load ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Significant Difference ◽  
Deformation Diagrams

Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.

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