共查询到20条相似文献,搜索用时 31 毫秒
1.
M.N. James D.J. Hughes D.G. Hattingh G. Mills P.J. Webster 《International Journal of Fatigue》2009,31(1):28-40
This paper presents single-line residual stress profiles for 8 mm 5083-H321 aluminium plates joined by gas metal arc (MIG) welding. The data were obtained by synchrotron diffraction strain scanning. Weld metal stresses (up to ~7 mm either side of the centreline) are quite scattered and unreliable because of the large epitaxial grain size in the fusion zone. Peak magnitude of the transverse stresses varies between +50 MPa (19% of parent plate proof strength) at the HAZ boundary to ?150 MPa (57% of PP proof strength) at the weld centreline. Equivalent values for longitudinal stresses are +90 MPa (34% of PP proof strength) some 22 mm from the weld centreline to ?120 MPa (45% of PP proof strength) at the weld centreline. Plate-to-plate variation in the as-welded transverse and longitudinal residual stress values across the weld toe region is around 40 MPa. The effect on residual stress and strain values of a sequence of applied fatigue loads was also considered and reported. 相似文献
2.
Results are given of measurements of the temperature characteristics of subsonic flows of air and oxygen plasma, generated by a VGU-4 100-kW induction plasmatron developed at IPM RAN (Institute of Problems of Mechanics of the Russian Academy of Sciences). The values of absolute intensity of spectral lines of oxygen and nitrogen atoms are used to measure the average (over the plasma jet diameter) temperature of atomic level populations (hereinafter referred to as atomic temperature) as a function of the parameters of the mode of generation, namely, the gas pressure in the range from 25 to 200 GPa and the power of anode supply within 29–72 kW. The distributions of the atomic temperature of plasma (T
a
) along the jet are obtained for some modes of generation. The radial distributions of the atomic temperature are obtained for some modes of generation of air and oxygen plasma. Their comparison with the temperature profiles obtained by the calculation of flows of equilibrium plasma in a discharge channel reveals a divergence for values of temperature on the flow axis exceeding 8000 K. 相似文献
3.
A study of turbulence/combustion interactions in a relatively large turbulent diffusion flame of an axisymmetric methane
jet into air is presented. A first order k–ɛ turbulence closure model is used along with two different models (equal scales and non-equal scales) for the submodel describing
the scalar dissipation rate. The flamelet concept is used to model the turbulent combustion along with a joint mixture fraction/strain
rate probability density function (PDF) for the prediction of the average parameters of the turbulent diffusion flame. The
numerical approach is that of Patankar and Spalding, while the flamelet simulations are obtained from the RUN-1DL code of
Rogg and co-workers based on a 17 species detailed reaction mechanism. The chosen configuration is that of the experimentally
studied turbulent diffusion flame of Streb [1]. A comparison between these experimental results and the obtained numerical
ones is thus presented. Relatively good agreements are obtained which show the usefulness of the two-scale model compared
to the classical one-scale model for predicting turbulent diffusion flames. Nonetheless some discrepancies are obtained in
the outer and downstream regions of the jet, especially in comparison with the experimental data. These are attributed to
short coming of the considered turbulence model and soot radiation which is not accounted for.
Received: 2 May 2002 / Accepted: 31 January 2003 相似文献
4.
E. Çadırlı U. Böyük S. Engin H. Kaya N. Maraşlı M. Arı 《Journal of Materials Science: Materials in Electronics》2010,21(5):468-474
Sn–3 wt% Cu hypereutectic alloy was directionally solidified upward with different growth rates (2.24–133.33 μm/s) at a constant
temperature gradient (4.24 K/mm) and with different temperature gradients (4.24–8.09 K/mm) at a constant growth rate (7.64 μm/s)
in the Bridgman-type growth apparatus. The measurements of microhardness of directionally solidified samples were obtained
by using a microhardness test device. The dependence of microhardness HV on the growth rate (V) and temperature gradient (G) were analyzed. According to these results, it has been found that with the increasing the values of V and G the value of HV increases. Variations of electrical resistivity (ρ) and electrical conductivity (σ) for casting samples with
the temperature in the range of 300–500 K were also measured by using a standard dc four-point probe technique. The variation
of Lorenz coefficient with the temperature for Sn–3 wt% Cu hypereutectic alloy was determined by using the measured values
of electrical and thermal conductivities. The enthalpy of fusion for same alloy was determined by means of differential scanning
calorimeter from heating trace during the transformation from eutectic liquid to eutectic solid. 相似文献
5.
K. Vijayakumar C. Sanjeeviraja M. Jayachandran L. Amalraj 《Journal of Materials Science: Materials in Electronics》2011,22(8):929-935
Thin films of tin disulphide on glass substrates were prepared by spray pyrolysis technique using precursor solutions of SnCl2·2H2O and n–n dimethyl thiourea at different substrate temperatures varied in the range 348–423 K. Using the hot probe technique
the type of conductivity is found to be n type. X ray diffraction analysis revealed the polycrystalline nature with increasing
crystallinity with respect to substrate temperature. The preferential orientation growth of SnS2 compound having hexagonal structure along (002) plane increased with the substrate temperature. The size of the tin disulphide
crystallites with nano dimension were determined using the Full Width Half Maximum values of the Bragg peaks and found to
increase with the substrate temperature. The surface morphology had been observed on the surface of these films using scanning
electron microscope. The optical absorption and transmittance spectra have been recorded for these films in the wavelength
range 400–800 nm. Thickness of these films was found using surface roughness profilometer. The absorption coefficient (α) was determined for all the films. Direct band gap values were found to exist in all the films deposited at different substrate
temperatures. The value of room temperature resistivity in dark decreased from 5.95 × 103 Ω cm for the amorphous film deposited at low temperature (348 K) to 2.22 × 103 Ω cm for the polycrystalline film deposited at high temperature (423 K) whereas the resistivity values in light decreased
from 1.48 × 103 to 0.55 × 103 Ω cm respectively, which is determined using the four probe method. Activation energy of these thin films was determined
by Arrhenius plot. 相似文献
6.
A. P. Ershov A. V. Kalinin O. S. Surkont I. B. Timofeev V. M. Shibkov V. A. Chernikov 《High Temperature》2004,42(6):865-874
The spectroscopic and probe methods are used to measure the microscopic parameters of plasma of pulsed and stationary transverse discharges in a supersonic air jet flowing into a submerged space. The measurements are performed for the Mach number of flow M = 2, submerged space pressure p = 5 to 30 kPa, degree of the jet being off-design n 2, and discharge current I = 1 to 10 A. The discharge current dependences of the average values of gas temperature, charged particle concentration, and reduced electric field are measured for a discharge mode close to that of current generator. The measured values of gas temperature lie in the range of 1 to 3 kK, those of charged particles concentration — of 1013 to 1014 cm-3 , and of reduced electric field — of 40 to 20 Td. The axial distribution of temperature is characterized by high values of temperature even at short distances from the electrodes and by a slow decrease along the flow.Translated from Teplofizika Vysokikh Temperatur, Vol. 42, No. 6, 2004, pp. 856–864.Original Russian Text Copyright © 2004 by A. P. Ershov, A. V. Kalinin, O. S. Surkont, I. B. Timofeev, V. M. Shibkov, and V. A. Chernikov. 相似文献
7.
J.?S.?Almeida T.?S.?M.?Fernandes A.?J.?M.?Sales M.?A.?S.?Silva G.?F.?M.?P.?Júnior H.?O.?Rodrigues A.?S.?B.?Sombra
In this paper, the structural and dielectric properties of BNO (BiNbO4) was investigated as a function of the external RF frequency and temperature. The BNO Ceramics, prepared by the conventional
mixed oxide method and doped with 3, 5 and 10 wt. % Bi2O3–PbO were sintered at 1,025 °C for 3 h. The X-ray diffraction patterns of the samples sintered, shown the presence of the
triclinic phase (β-BNO). In the measurements obtained at room temperature (25 °C) was observed that the largest values of
dielectric permittivity (ε′
r
) at frequency 100 kHz, were for the samples: BNO5Bi (5 wt. % Bi2O3) and BNO5Pb (5 wt. % PbO) with values ε′
r
~ 59.54 and ε′
r
~ 78.44, respectively. The smaller values of loss tangent (tan δ) were for the samples: BNO5Bi and BNO3Pb (3 wt. % PbO) with
values tan δ ~ 5.71 × 10−4 and tan δ ~ 2.19 × 10−4, respectively at frequency 33.69 MHz. The analysis as a function of temperature of the dielectric properties of the samples,
obtained at frequency 100 kHz, showed that the larger value of the relative dielectric permittivity was about ε′
r
~ 76.4 at temperature 200 °C for BNO5Pb sample, and the value smaller observed of dielectric loss was for BNO3Bi sample at
temperature 80 °C, with about tan δ ~ 5.4 × 10−3. The Temperature Coefficient of Capacitance (TCC) values at 1 MHz frequency, present a change of the signal from BNO (−55.06 ppm/°C)
to the sample doped of Bi: BNO3Bi (+86.74 ppm/°C) and to the sample doped of Pb: BNO3Pb (+208.87 ppm/°C). One can conclude
that starting from the BNO one can increase the doping level of Bi or Pb and find a concentration where one have TCC = 0 ppm/°C,
which is important for temperature stable materials applications like high frequency capacitors. The activation energy (H)
obtained in the process is approximately 0.55 eV for BNO sample and increase with the doping level. These samples will be
studied seeking the development ceramic capacitors for applications in radio frequency devices. 相似文献
8.
Cloud point extraction and flame atomic absorption spectrometry combination for copper(II) ion in environmental and biological samples 总被引:1,自引:1,他引:0
Shokrollahi A Ghaedi M Hossaini O Khanjari N Soylak M 《Journal of hazardous materials》2008,160(2-3):435-440
A cloud point extraction procedure was presented for the preconcentration of copper(II) ion in various samples. After complexation by 4-(phenyl diazenyl) benzene-1,3-diamine (PDBDM) (chrysoidine), copper(II) ions were quantitatively recovered in Triton X-114 after centrifugation. 0.5 ml of methanol acidified with 1.0 mol L−1 HNO3 was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The influence of analytical parameters including ligand, Triton X-114 and HNO3 concentrations, bath temperature, heating time, centrifuge rate and time were optimized. The effect of the matrix ions on the recovery of copper(II) ions was investigated. The detection limit (3S.D.b/m, n = 10) of 0.6 ng mL−1 along with preconcentration factor of 30 and enrichment factor of 41.1 with R.S.D. of 1.0% for Cu was achieved. The proposed procedure was applied to the analysis of various environmental and biological samples. 相似文献
9.
Fouad Khaldi Karim Messadek Adel Mustapha Benselama 《Microgravity science and technology》2010,22(1):1-5
We present the experimental demonstration of the ability of magnetic field to remove buoyancy effects on flames. The experiment
consists to observing the shape and colour changes of a laminar jet diffusion flame located in the air-gap of a Bitter magnet
able to delivering up 650 T2/m in magnetic gradient intensity. At some critical (predicted theoretically) value of the upward magnetic field gradient
strength, the flame becomes nearly hemispheric and free of soot similarly to flames at zero-gravity in drop towers. 相似文献
10.
Sn–3.5 wt% Ag alloy was directionally solidified upward with a constant growth rate (V = 16.5 μm/s) and a temperature gradient (G = 3.3 K/mm) in a Bridgman-type growth apparatus. The variations of electrical resistivity (ρ) with temperature in the range of 293–476 K for the directionally solidified Sn–3.5 wt% Ag eutectic alloy was measured. The
measurements indicate that the electrical resistivity of the directionally solidified Sn–Ag eutectic solder increases with
increasing temperature. The variations of thermal conductivity of solid phases versus temperature for the same alloy was determined
from the Wiedemann-Franz and Smith-Palmer equations by using the measured values of electrical conductivity. From the graphs
of electrical resistivity and thermal conductivity versus temperature, the temperature coefficient of electrical resistivity
(α
TCR
) and the temperature coefficient of thermal conductivity (α
TCT
) for the same alloy were obtained. According to experimental results, the electrical and thermal conductivity of Sn–Ag eutectic
solder linearly decrease with increasing the temperature. The enthalpy of fusion (ΔH) and the change of specific heat (ΔC
P
) during the transformation at the studied alloy were determined from heating curve during the transformation from eutectic
solid to eutectic liquid by means of differential scanning calorimeter (DSC). 相似文献
11.
CuIn3S5 compound was prepared by direct reaction of high-purity elemental copper, indium and sulphur. CuIn3S5 thin films were prepared from powder by thermal evaporation under vacuum (10−6 mbar) onto glass substrates. The glass substrates were heated from 30 to 200 °C. The powder was characterized for their structural
and compositional properties by using X-ray diffraction (XRD) and energy dispersive X-ray (EDAX). The XRD studies revealed
that the powder exhibiting P-chalcopyrite structure. From the XRD data, we calculated the lattice parameters a and c. Then, the cation–anion bond lengths l
AC and l
BC are deduced. The films were characterized for their structural, compositional, morphological and optical properties by using
XRD, EDAX, atomic force microscopy and optical measurement techniques (transmittance and reflectance). XRD analysis revealed
that the films deposited at a room temperature (30 °C) are amorphous in nature, whereas those deposited on heated substrates
(≥75 °C) were polycrystalline with a preferred orientation along (112) of the chalcopyrite phase. The surface morphological
analysis revealed that the films grown at different substrate temperature had an average roughness between 1.1 and 4.8 nm.
From the analysis of the transmission and reflection data, the values of direct and indirect band gap of the films were determined.
We found that the optical band gap decreases when the substrate temperature increases. 相似文献
12.
K. M. Garrity D. C. Ripple M. Araya C. R. Cabrera L. Cordova Murillo M. E. de Vanegas D. J. Gee E. Guillén S. Martinez-Martinez E. Mendez-Lango L. Mussio S. G. Petkovic K. N. Quelhas G. Rangugni O. Robatto E. von Borries Rocha 《International Journal of Thermophysics》2008,29(5):1828-1837
Under the auspices of the Inter-American Metrology System (SIM), the National Institute of Standards and Technology (NIST)
initiated a regional comparison for type K thermocouples from (100 to 1,100) °C with 11 participating countries. The use of
type K material above approximately 200 °C is considered destructive. Therefore, each participating laboratory was sent new,
unused wire from a lot of material characterized by NIST. The uniformity of the lot was remarkable, especially at temperatures
above 500 °C; the standard deviation of the thermocouple emf values of multiple cuts tested at NIST was 2.7 μV or less over
the full temperature range. The high uniformity eliminated any need to correct for variations of the transfer standard among
the laboratories, greatly simplifying the analysis. The level of agreement among the laboratories’ results was quite good.
Even though test procedures and equipment varied significantly among the participants, the standard deviation of all emf values
at each test temperature was less than the equivalent of 0.20 °C at 200 °C and below, and less than 0.60 °C from (400 to 1,100) °C.
Of the 380 total bilateral combinations of the data at the eight test temperatures, only 13 (i.e., 3.4% of all combinations)
are outside the k = 2 limits, and of these 13, only 3 are outside k = 3 limits. All the outliers occur at temperatures of 800 °C and below, which suggests that drift of the type K wire due
to high-temperature oxidation did not cause changes in the thermocouple emf comparable to or larger than the claimed uncertainties. 相似文献
13.
The paper deals with the spectroscopic determination of the temperature T
v
of population of low-lying vibrational levels of radiating electron terms of an N2 molecule and N
2
+
molecular ion in different cross sections of a high-enthalpy jet of atmospheric-pressure nitrogen plasma. Use is made of the method of optimal fitting of the measured and simulated rovibronic spectra in some selected spectral range of the (0–1) and (1–2) bands of the first negative system of N
2
+
ion and of the method of finding T
v
by the integral intensities of molecular bands (sequence Δv = −1 of the second positive system of N2). The obtained values of vibrational temperature are compared to the previously found values of rotational temperature T
r
and electron temperature T
e
. The pattern of variation of temperatures along the plasma jet in the zone of relaxation is discussed.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 4, 2005, pp. 501–509.Original Russian Text Copyright © 2005 by A. A. Belevtsev, E. Kh. Isakaev, A. V. Fedorov, and V. F. Chinnov. 相似文献
14.
Jung Sang Cho Dae Soo Jung Jin Man Han Yun Chan Kang 《Materials science & engineering. C, Materials for biological applications》2009,29(4):1288-1292
Nano-sized α-TCP powders with spherical shape and non-aggregation characteristics were directly prepared by high temperature flame spray pyrolysis from the mixed spray solution of water and ethyl alcohol. The α-TCP powders prepared from the aqueous spray solution without ethyl alcohol had a bimodal size distribution with nanometer and micron sizes. Nano-sized and monodisperse α-TCP powders were prepared when the volume ratio (ethyl alcohol/distilled water, V/V) in the mixed solvent was of 40/60. The mean size of the nano-sized α-TCP powders was 32 nm. The composition ratio of calcium and phosphorous components of the nano-sized α-TCP powders was 1.49. The mean size of the spherical-like powders post-treated at a temperature of 600 °C was 57 nm. The mean size of the powders increased with increasing the post-treatment temperatures. The phase of α-TCP powders prepared by flame spray pyrolysis did not change at post-treatment temperatures below 700 °C. On the other hand, the powders post-treated at temperatures of 800 and 900 °C had single β phase of TCP. 相似文献
15.
《Materials Science & Technology》2013,29(12):1427-1432
AbstractA mathematical model is developed to assess the solidification behaviour of the weld pools. To do so, during gas tungsten arc welding of commercial pure aluminium, equations of conversation of mass, energy and momentum are numerically solved considering three-dimensional steady state heat transfer and fluid flow conditions. The weld pool geometry, weld thermal cycles and various solidification parameters are calculated using temperature and velocity fields acquiring from the utilised model. The solidification behaviour of the weld pool at the weld centreline and the fusion line is then studied using the solidification parameters including temperature gradient G, solidification rate R and the combined forms G/R and GR. In order to verify the predictions, welding experiments are performed and geometry of the weld fusion zone is measured. The calculated geometry of the weld fusion zone is found to be in good agreement with the corresponding experimental result. The predictions show that the cooling rate GR increases toward the centreline while the other solidification parameter G/R shows a different behaviour. In addition, it is found that under the employed welding conditions, as the welding speed increases temperature gradients both at the weld centreline and at the fusion line are reduced. 相似文献
16.
为了研究不同喷射压力对乙烷喷射火火焰形态和热辐射范围的影响,进行30、35、50 mm喷嘴口径下乙烷喷射火的引燃试验,通过对喷射火的火焰高度、温度和热辐射强度进行监测,分析不同喷射压力下乙烷喷射火的燃烧规律。结果表明,随着喷射压力和喷嘴口径的增大,火焰高度和温度逐渐升高;在50 mm喷嘴口径、0.20 MPa压力时,火焰最高温度达到1 260 ℃;在30 mm喷嘴口径和0.15、0.20 MPa喷射压力时,距离火焰30 cm处热辐射强度超过25 kW/m2,达到可能致死的辐射量级。 相似文献
17.
Accuracy and precision of single-pulse one-dimensional vibrational coherent anti-Stokes Raman-scattering temperature measurements 总被引:1,自引:0,他引:1
The accuracy and precision of time-resolved one-dimensional temperature measurements using single-pulse one-dimensional N(2) vibrational coherent anti-Stokes Raman scattering along a line have been investigated in air in the temperature range from 300 to 1500 K. For this, the experimental spectra were taken in a high-temperature oven at atmospheric pressure. A planar BOXCARS phase-matching geometry was employed to generate the signal along a 6.16-mm line directed perpendicular to the beam propagation. With the used imaging optics, in this direction a spatial resolution of 86 mum was achieved. Depending on the set temperature, the agreement between the thermocouple readings and the mean values of the evalutated coherent anti-Stokes Raman-scattering temperatures is better than 40 K. The applicability of this new technique for the time-resolved measurement of temperature gradients is demonstrated along a line that crosses the flame front in a premixed laminar CH(4)-air flame. 相似文献
18.
Gan TH Hutchins DA 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(9):1214-1218
This paper illustrates the use of air-coupled ultrasonic tomography for the measurement of a highs temperature flame from a natural gas burner, using capacitive ultrasonic transducers in through transmission. This uses a transducer pair, which is scanned in two-dimensional sections at several angles to the jet axis. Travel-time data then is recorded along various paths in counter-propagating directions. By processing the data obtained from propagation times, images have been formed of variations in temperature within the flame, using the tomographic reconstruction approach. 相似文献
19.
N. Noulkow R. D. Taubert P. Meindl J. Hollandt 《International Journal of Thermophysics》2009,30(1):131-143
At the Physikalisch-Technische Bundesanstalt (PTB), absolutely-calibrated filter radiometers based on silicon photodiodes
are routinely used for thermodynamic temperature determinations of blackbodies in the range from the zinc fixed point (FP)
(419 °C) up to 3,000 °C. To extend the temperature range down to the tin FP (232 °C), we have designed two new filter radiometers
based on indium gallium arsenide (InGaAs) photodiodes with center wavelengths at 1,300 nm and 1,550 nm. For the absolute calibration
of the spectral irradiance responsivity of the new InGaAs filter radiometers, the spectral responsivity measurement in the
near-infrared (NIR) spectral range has been significantly improved. With a newly developed tuneable laser and monochromator-based
cryogenic radiometer facility, the relative standard uncertainty of the NIR spectral responsivity has been reduced from 0.17 %
to about 0.03 %. By using the calibrated InGaAs filter radiometer in conjunction with the large-area double sodium heat pipe
of the PTB, the first results for the difference between the thermodynamic temperature T and the ITS-90 temperature T
90 in the temperature range from the zinc FP up to the aluminum FP (660 °C) are presented. The values for T – T
90 determined with the new InGaAs filter radiometers are consistent within their relative standard uncertainty of about 30 mK
at 419 °C to about 60 mK at 660 °C.
References to commercial products are for identification purposes only and constitute neither endorsement nor representation
that the item identified is the best available for the stated purpose. 相似文献
20.
《Vacuum》2013
To perform high-quality welding, the heat input from the arc to the base metal is controlled. However, an anode jet sometimes occurs. In such cases, control is difficult and weld defects occur. This study elucidates how anode jet generation is affected by the radial current density distribution for maintaining the current continuity. The anode jet starts to occur at 15–20 mm of interelectrode distance. The arc temperature decreases because the arc radius increases. Then electrical conductivity decreases sharply depending on the temperature. If electrical conductivity decreases, then the current density decreases, and the arc cannot maintain the current continuity. When the mean current density is 8.7 × 105 A/m2, the flow velocity is zero at 15 mm. Therefore, this minimum value of the mean current density is the anode jet generation condition. 相似文献