The Effect of Temperature on the Material Damping of Graphite/Epoxy Composites in a Simulated Space Environment

1990 ◽  
Vol 112 (3) ◽  
pp. 277-279 ◽  
Author(s):  
G. T. Spirnak ◽  
J. R. Vinson
Keyword(s):  
Room Temperature ◽  
Damping Ratio ◽  
Theoretical Models ◽  
Space Environment ◽  
Effect Of Temperature ◽  
Time Cost ◽  
Material Damping ◽  
Temperature Dependent ◽  
Increasing Temperature ◽  
Free Beam

An experimental method for measuring material damping is described, which employs a free-free beam lightly supported at the nodes. A thermal space environment is simulated by measuring the material damping in air at temperatures ranging from −65°F to 225°F, and then subtracting out the effects of atmospheric damping. This method saves considerable time, cost and experimental difficulties associated with performing the experiments in a vacuum. Graphite/epoxy AS4/3501-6 composite beam specimens were tested. At room temperature, the [0°]12 composites were found to have an average damping ratio of 0.0556 percent. The [90°]12 composites were found to have an average material damping ratio of 0.55 percent. These data agree well with the theoretical models and experimental measurements performed in a vacuum. The material damping ratio is temperature dependent over the range −65°F to 225°F, increasing with increasing temperature. For the [0°]12 composite, the material damping ratio varies from 0.0397 percent at −65°F to 0.083 percent at 225°F. For the [90°]12 composite, the material damping ratio varies from 0.408 percent at −65°F to 0.860 percent at 225°F.

A temperature-dependent structure study of gem-quality hibonite from Myanmar

2010 ◽  
Vol 74 (5) ◽  
pp. 871-885 ◽  
Author(s):  
M. Nagashima ◽  
T. Armbruster ◽  
T. Hainschwang
Keyword(s):  
Room Temperature ◽  
Structure Study ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Trigonal Bipyramidal ◽  
Expansion Coefficients ◽  
Increasing Temperature ◽  
Length Distortion

AbstractThe structure of hibonite from Myanmar (space group P63/mmc, Z = 2, at room temperature a = 5.5909(1), c = 21.9893(4) Å), with simplified formula CaAl12O19 and composition (Ca0.99Na0.01)Σ1.00 was investigated between temperatures of 100 K and 923 K by single-crystal X-ray diffraction methods. Structure refinements have been performed at 100, 296, 473 and 923 K. In hibonite from Myanmar, Ti substitutes for Al mainly at the octahedral Al4 site and, to a lesser degree, at the trigonal bipyramidal site, Al2. The Al4 octahedra build face-sharing dimers. If Ti4+ substitutes at Al4, adjacent cations repulse each other for electrostatic reasons, leading to off-centre cation displacement associated with significant bond-length distortion compared to synthetic (Ti-free) CaAl12O19. Most Mg and smaller proportions of Zn and Si are assigned to the tetrahedral Al3 site. 12-coordinated Ca in hibonite replaces oxygen in a closest-packed layer. However, Ca is actually too small for this site and engages in a ‘rattling-type’ motion with increasing temperature. For this reason, Ca does not significantly increase thermal expansion coefficients of hibonite. The expansion of natural Ti,Mg-rich hibonite between 296 and 923 K along the x and the z axes is αa = 7.64×10–6 K–1 and αc = 11.19×10–6 K–1, respectively, and is thus very similar to isotypic, synthetic CaAl12O19 and LaMgAl11O19 (LMA).

Effect of Temperature on Crater Formation and Ejecta Composition in Aluminum Alloy Targets

2012 ◽  
Vol 706-709 ◽  
pp. 768-773
Author(s):  
Masahiro Nishida ◽  
Koichi Hayashi ◽  
Junichi Nakagawa ◽  
Yoshitaka Ito
Keyword(s):  
Aluminum Alloy ◽  
High Temperature ◽  
Low Temperature ◽  
Room Temperature ◽  
Effect Of Temperature ◽  
Crater Formation ◽  
Influence Of Temperature ◽  
Gas Gun ◽  
Influence Of Temperature On ◽  
Increasing Temperature

The influence of temperature on crater formation and ejecta composition in thick aluminum alloy targets were investigated for impact velocities ranging from approximately 1.5 to 3.5 km/s using a two-stage light-gas gun. The diameter and depth of the crater increased with increasing temperature. The ejecta size at low temperature was slightly smaller than that at high temperature and room temperature. Temperature did not affect the size ratio of ejecta. The scatter diameter of the ejecta at high temperature was slightly smaller than those at low and room temperatures.

The Deformation Microstructure in NI3Si Polycrystals Strained Over the Range of Temperature of Flow Stress Anomaly

1988 ◽  
Vol 133 ◽  
Author(s):  
B. Tounsia ◽  
P. Beauchamp ◽  
Y. Mishima ◽  
T. Suzuki ◽  
P. Veysslière
Keyword(s):  
Flow Stress ◽  
Slip System ◽  
Room Temperature ◽  
Peak Temperature ◽  
Effect Of Temperature ◽  
Screw Dislocations ◽  
Thermally Activated ◽  
Cube Plane ◽  
Octahedral Slip ◽  
Increasing Temperature

ABSTRACTIn order to correlate the flow stress anomaly of Ni3Si with dislocation properties, a weakbeam study ofpolycrystalline samples deformed between ambient and the peak temperature was carried out. Samples with two extreme Ni/Si ratios were tested.The most frequently activated slip system changes progressively from octahedral to cubic with increasing temperature. The transformation of superdislocations into Kear-Wilsdorf configurations gives rise to screw dislocations that are rectilinear only after deformation at room temperature. The effect of temperature is to gradually promote bending of Kear-Wisdorf configurations in the cube plane, from a few nanometers at 230°C to several tenths of micrometers at intermediate temperature. Cube slip begins to be massively activated a little below the peak temperature. It is suggested that the flow stress anomaly is controlled by progressive exhaustion of octahedral slip by thermally-activated expansion of superdislocations on the cube cross-slip plane.

scholarly journals Temperature-Dependent Photoluminescence of Manganese Halide with Tetrahedron Structure in Anti-Perovskites

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3310
Author(s):  
Yijie Xia ◽  
Shuaishuai Du ◽  
Pengju Huang ◽  
Luchao Wu ◽  
Siyu Yan ◽  
...  
Keyword(s):  
Energy Level ◽  
Recombination Rate ◽  
Radiative Recombination ◽  
Room Temperature ◽  
Energy Levels ◽  
Radiative Recombination Rate ◽  
Temperature Dependent ◽  
Recombination Rates ◽  
Increasing Temperature ◽  
Temperature Dependent Photoluminescence

The temperature-dependent photoluminescence (PL) properties of an anti-perovskite [MnBr4]BrCs3 sample in the temperature range of 78–500 K are studied in the present work. This material exhibits unique performance which is different from a typical perovskite. Experiments showed that from room temperature to 78 K, the luminous intensity increased as the temperature decreased. From room temperature to 500 K, the photoluminescence intensity gradually decreased with increasing temperature. Experiments with varying temperatures repeatedly showed that the emission wavelength was very stable. Based on the above-mentioned phenomenon of the changing photoluminescence under different temperatures, the mechanism is deduced from the temperature-dependent characteristics of excitons, and the experimental results are explained on the basis of the types of excitons with different energy levels and different recombination rates involved in the steady-state PL process. The results show that in the measured temperature range of 78–500 K, the steady-state PL of [MnBr4]BrCs3 had three excitons with different energy levels and recombination rates participating. The involved excitons with the highest energy level not only had a high radiative recombination rate, but a high non-radiative recombination rate as well. The excitons at the second-highest energy level had a similar radiative recombination rate to the lowest energy level excitons and a had high non-radiative recombination rate. These excitons made the photoluminescence gradually decrease with increasing temperature. This may be the reason for this material’s high photoluminescence efficiency and low electroluminescence efficiency.

Effect of Temperature and Strain Rate on the Mechanical Properties of 99.5 Aluminium Rods Extruded by KOBO

2016 ◽  
Vol 879 ◽  
pp. 230-235
Author(s):  
Sonia Boczkal ◽  
Marzena Lech-Grega ◽  
Wojciech Szymanski ◽  
Paweł Ostachowski ◽  
Marek Lagoda
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
High Strain ◽  
Effect Of Temperature ◽  
Recrystallization Process ◽  
Extrusion Force ◽  
Strain Rates ◽  
High Strain Rates ◽  
Constant Frequency ◽  
Increasing Temperature

In this study, aluminium rods were cold extruded in a direct process by KOBO method in two variants: variant I with varying (decreasing) frequency of die oscillations necessary to maintain a constant extrusion force, and variant II with constant frequency of die oscillations, leading to a decrease in the extrusion force. The tensile test of rods was carried out in a temperature range of 20 - 200°C and at a strain rate from 8xE10-5 to 8xE10-1 s-1. Significant differences in the elongation of the tested rods were observed. It was found that rods extruded at variable die oscillations and stretched at room temperature had similar elongation, independent of the strain rate. With the increase of temperature, the elongation of samples stretched at a low speed was growing from a value of about 8% at room temperature up to 40% at 200°C. At high strain rates, despite the increasing temperature, the elongation remained at the same level, i.e. 5-6%. In rods extruded at constant die oscillations, the elongation at a low strain rate was growing with the temperature from 10% at room temperature up to 29% at 200°C. At high strain rates, the elongation decreased from 28% at room temperature to 11% at 200°C. The results were interrelated with examinations of the structure of rods and fractures of tensile specimens. In the material extruded by KOBO method with constant die oscillations, the beginnings of the recrystallization process were observed, absent in the material extruded at variable die oscillations.

Infrared spectra of the ammonium ion in crystals. Part VII. Existence of symmetrically trifurcated hydrogen bond in ammonium halides

1980 ◽  
Vol 58 (3) ◽  
pp. 270-282 ◽  
Author(s):  
Osvald Knop ◽  
Wolfgang J. Westerhaus ◽  
Michael Falk
Keyword(s):  
Room Temperature ◽  
Ammonium Ion ◽  
Effect Of Temperature ◽  
Hydrogen Bonding Interaction ◽  
Maximum Probability ◽  
Threefold Axis ◽  
Ammonium Halides ◽  
Bonding Interaction ◽  
Increasing Temperature

This investigation deals with the effect of temperature, between 10 and 293 K, on the ir spectrum of the NH3D+ probe ion in polycrystalline NH4SnF3, NH4CuSO3, cubic (NH4)2SiF6, and (NH4)2SnCl6. The results lead to the following conclusions. At 10 K these crystals contain symmetrically trifurcated [Formula: see text] bonds, i.e. bonds in which the N—H orientation of maximum probability is on the threefold axis. With increasing temperature these bonds lose progressively their symmetrically-trifurcated character to become highly bent, highly dynamic [Formula: see text]•bonds, and the strength of the hydrogen-bonding interaction increases. This is reflected in the decrease of the ND stretching frequency of the probe ion with increasing temperature, which is the opposite of the behaviour observed with normal (i.e. essentially straight) [Formula: see text] bonds.Re-determination of the room-temperature crystal structure of NH4CuSO3 has confirmed the correctness of the structure reported previously by Nyberg and Kierkegaard.

Effect of temperature on the fluorescence emission of ENCTTTC in different nonpolar solvents

2013 ◽  
Vol 91 (11) ◽  
pp. 971-975 ◽  
Author(s):  
N.R. Patil ◽  
R.M. Melavanki ◽  
J. Thipperudrappa ◽  
Ushie Onumashi Afi
Keyword(s):  
Excited States ◽  
Thermal Activation ◽  
Fluorescence Emission ◽  
Energy Difference ◽  
Effect Of Temperature ◽  
Relative Location ◽  
Nonradiative Transition ◽  
Temperature Dependent ◽  
Nonpolar Solvents ◽  
Increasing Temperature

The effect of temperature (20–60 °C) on the fluorescence emission of (E)-N-(3-chlorophenyl)-2-(3,4,5-trimethoxybenzylideneamino)-4,5,6,7-tetrahydrobenzo [b]thiophene-3carboxamide (ENCTTTC) is studied in different solvents. It is found that there is no shift in the position of fluorescence maxima, but the intensity decreases with increasing temperature, which depends on the polarity of the solvent. A mechanism of fluorescence quenching with rise in temperature is discussed in terms of the relative location of lowest (ππ*) (nπ*) states and the energy difference between them. The change in temperature brings about a change in the probabilities of radiative and nonradiative transition. The nonradiative deactivation of excited states in the absence of a quencher is temperature dependent and its thermal activation energy has been determined.

Coupling effect of temperature and braided angle on compressive behaviors of 3D braided carbon–epoxy composite at low temperature

2016 ◽  
Vol 51 (18) ◽  
pp. 2531-2547 ◽  
Author(s):  
Hailou Wang ◽  
Baozhong Sun ◽  
Bohong Gu
Keyword(s):  
Room Temperature ◽  
Coupling Effect ◽  
Damage Zone ◽  
Orientation Angle ◽  
Effect Of Temperature ◽  
Braided Composites ◽  
Temperature Dependent ◽  
3D Braided Composites ◽  
Compressive Damage ◽  
Carbon Fiber Epoxy

This paper reports the influence of temperature and braided angle on compressive behaviors of 3D braided carbon fiber–epoxy composites. The compressive behaviors of the 3D braided with three braided angles (26°, 35° and 48°) were tested at various temperatures (−100℃, −50℃, 0℃, 20℃). The compressive damage morphologies were observed with SEM photographs. It was observed that the temperature and the braided angle have significant effect on the longitudinal compressive behaviors of 3D braided composites. The overall effect of braided angle on the 3D braided composites was greater than the temperature. The influence of the braided angle on the compressive behaviors is from the yarn orientation angle, while the influence of the temperature is from the temperature-dependent behaviors of the epoxy resin. Under low temperatures, the 3D braided composite behaved as brittle material and the compressive damage was easier than that of room temperature. The changes of yarn trajectory also led to generate the damage zone, especially in the edge and surface regions of the 3D braided composites.

Finite element simulation and experimental investigation on the effect of temperature on pseudoelastic behavior of perforated Ni–Ti shape memory alloy strips

2021 ◽  
Author(s):  
Emre Altas ◽  
Farshid Khosravi Maleki ◽  
Hasan Gokkaya ◽  
Vahid Arab Maleki ◽  
Yüksel Akınay ◽  
...  
Keyword(s):  
Finite Element ◽  
Shape Memory ◽  
Element Model ◽  
Effect Of Temperature ◽  
Flexural Stiffness ◽  
Temperature Dependent ◽  
Three Point Bending ◽  
Increasing Temperature ◽  
The Finite Element Model ◽  
Pseudoelastic Behavior

Abstract In the present study, the temperature-dependent pseudoelastic behavior of shape memory alloy sheets is studied experimentally and by finite element modeling. For this purpose, temperature-dependent mechanical properties for Ni-Ti alloy materials are first obtained by using direct tensile and three-point bending experiments at 23, 50, and 80 °C temperatures, respectively. The structure of these materials is examined at different temperatures using SEM images and the XRD test. Furthermore, using the finite element model, the pseudoelastic behavior and the effect of temperature on the residual deflection of the prose-shape memory strips with a circular hole under three-point bending loads are studied. After validating the results of the finite element model with the results of experimental tests, the effects of various parameters such as the diameter and number of holes on residual deformation and residual strains are investigated. The results show that with increasing temperature, the mechanical properties including the tensile strength, Young's modulus, yield stress, and flexural strength of SMA strips increase significantly. For solid strips, although increasing the temperature increases the maximum flexural force, in contrast, it reduces the flexural stiffness. In solid strips, flexural stiffness decreases by 5.5% with increasing temperature from 23 °C to 80 °C.

Energy Considerations in the Spreading of LNG on Sea Water

2008 ◽  
Author(s):  
A. Subramani ◽  
S. Jayanti
Keyword(s):  
Heat Transfer ◽  
Sea Water ◽  
Current Model ◽  
Theoretical Models ◽  
Effect Of Temperature ◽  
Test Case ◽  
Hazardous Substance ◽  
Temperature Dependent ◽  
One Dimensional ◽  
Conventional Models

The spreading of an accidental spill of Liquefied Natural Gas (LNG) on sea water has been studied for many years and several theoretical models have been proposed and successfully used. Many modeling techniques have been used by researchers for the spreading of LNG. However, most of these neglect the heat transfer aspects related to the spreading, and the effect of temperature dependent properties such as density, thermal conductivity and specific heat of LNG is not included in the analysis. In the present study, this situation is redressed by including the depth-averaged energy equation in a one-dimensional model of the spreading of LNG on sea water. The thermophysical and transport properties of the fluid are made temperature-dependent and heat transfer to the pool from the water below and the flame above are included. The resulting set of coupled one-dimensional mass, radial momentum and energy balance equations are solved numerically using an explicit, second order-accurate finite difference method-based discretization of the governing equations. Results obtained in the present study show that the incorporation of the variable properties gives significantly improved predictions over conventional models. The predicted results are compared with the experimental results of Raj et al [1], and with a conventional, constant-properties model of Fay [2] for the test case #12. Excellent agreement is found between the current model predictions and the experimental data while the conventional model overpredicts the pool diameter for longer times. It is demonstrated that the present approach is inherently capable of distinguishing between the spreading of different LNG mixtures, and can therefore be readily extended to the analysis of the accidental spill of any other hazardous substance.

Sign in / Sign up

Export Citation Format

Share Document