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1.
Ductile L20-type wires and+L12-type duplex wires with high strengths and large elongation in the Ni-Al-Fe and Ni-Al-Co ternary systems have been manufactured directly from the liquid state by an in-rotating-water spinning method. The wire diameter was in the range 80 to 180m and the average grain size was 2 to 4m for the wires and 0.2 to 1.0m for the+ wires.
y,
f and
p of the wires were found to be about 360 to 760 MPa, 560 to 960 MPa, and 0.2 to 5.5%, respectively, for the Ni-Al-Fe system, those of the+ wires were about 395 to 660 MPa, 670 to 1285 MPa, and 3.5 to 17%, respectively, for the Ni-Al-Fe system, and about 260 to 365 MPa, 600 to 870 MPa, and 4.0 to 7.0%, respectively, for the Ni-Al-Co system. Cold-drawing caused a significant increase in
y and
f and the values attained were about 1850 and 2500 MPa, respectively, for Ni-20Al-30Fe and Ni-25Al-30Co wires drawn to about 90% reduction in area. The high strengths, large elongation and good cold-workability of the melt-quenched and+ compound wires have been inferred to be due to the structural change into a low-degree ordered state containing a high density of phase boundaries, suppression of grain-boundary segregation and refinement of grain size. 相似文献
2.
Spectra of Rayleigh-scattered light in4He near the gas-liquid critical point have been measured, using a photon correlation method. Fitting the obtained relaxation times to Kawasaki's expression with background modification, we have obtained along the critical isochore the correlation length =(3.6±0.78)–0.534±0.046 Å and the high-frequency shear viscosity *=21.5±3.6 µP. * has been revealed to be in good agreement with the regular part of the viscosity r=21±2µP. The singular part of the thermal diffusivity has been determined to beD
Ts
=(4.9±2.7)×10–5–0.543±0.046 cm2/sec along the critical isochore. 相似文献
3.
G. Foca M. Manfredini D. Manzini A. Marchetti L. Pigani S. Sighinolfi L. Tassi A. Ulrici 《International Journal of Thermophysics》2004,25(3):839-855
The static dielectric constant () of ethane-1,2-diol+1,2-dimethoxyethane + water ternary mixtures was measured as a function of temperature (263.15 T (K) 353.15) and composition, over the complete mole fraction range 0 x
1, x
2, x
3 1. The experimental values were analyzed by empirical relationships that accounted for the dependence = (T) and Y = Y(x
i). A comparison between calculated and experimental data shows that these fitting relationships can be reliably used to predict values, along with other related properties, in areas of experimental data gaps. Starting from the experimental measurements, some derived quantities such as molar orientational polarization (P), dipolar interaction free energy ( F
) and the relevant thermodynamic excess mixing properties (F
E, FE
,i), were obtained. The values of the excess quantities are indicative of the presence of specific interactions between different components in the mixtures. A discussion of data in terms of the Kirkwood theory also provides information on the short-range intermolecular interactions, suggesting the formation of stable two-:component adducts rather than of more complex moieties involving all three molecular species. 相似文献
4.
A four-ring, toroidal cross capacitor was used to measure accurately the relative dielectric permittivity (p,T) of He, Ar, N2, O2, CH4, C2H6, C3H8, and CO2. ( is often called the dielectric constant.) The data are in the range from 0 to 50°C and, in many cases, extend up to 7 MPa. The accurate measurement of (p,T) required a good understanding of the deformation of the gas-filled capacitors with applied pressure. This understanding was tested in two ways. First, the experimental values of (p,T) for helium were compared with theoretical values. The average difference was within the noise,
expt–
theory=(–0.05±0.21)×10–6, demonstrating that the four-ring cross capacitor deformed as predicted. Second, (p,T) of argon was measured simultaneously on three isotherms using two capacitors: the four-ring capacitor, and a 16-rod cross capacitor made using different materials and a different geometry. The results for the two capacitors are completely consistent, within the specifications of the capacitance bridge. There was a small inconsistency that was equivalent to 1×10–6 of the measured capacitances, or, for argon, 3×10–5
A
, where A
is the zero-density limit of the molar polarizability (–1)/[(+2)]. 相似文献
5.
B. Chesca 《Journal of Low Temperature Physics》1998,110(5-6):963-1001
A comprehensive analytical theory is presented for non-hysteretic RF SQUIDs operating in the adiabatic mode in the presence of large thermal fluctuations. When 1 ( = 2LIc/0
is the hysteresis parameter, L is the SQUID inductance, Ic
is the critical current of the Josephson junction, and
0
is the flux quantum) the theory is applicable also for RF SQUIDs operating in the non-adiabatic mode. In contrast to previous theories in which the noise is treated perturbatively and which therefore are applicable only if the product 1 ( = 2kBT/
0
Ic
is the noise parameter, kB
is the Boltzmann constant, and T is the absolute temperature)—the case of small thermal fluctuations—the present theory is valid for around unity or higher. In the limit 0 the theory reproduces the results of small thermal fluctuations theories. It has been found that in the presence of large thermal fluctuations the screening current in the SQUID inductance is suppressed by a factor that increases with increasing . Taking into account this new basic fact, all SQUID characteristics (output signal, transfer function, noise spectral density and energy sensitivity) have been recalculated and a good agreement with experimental data has been obtained. It has been also found that RF SQUIDs can be operated with substantially higher values of the inductance and of the noise parameter than DC SQUIDs. These two aspects, which are of particular importance at liquid nitrogen temperature, make high Tc
RF SQUIDs very attractive. 相似文献
6.
Prof. Y. Kohama 《Acta Mechanica》1987,66(1-4):21-38
Summary Three-dimensional boundary layer transition on axisymmetric rotating bodies is the subject of a comprehensive experimental study. Based on this study, hypotheses are made on the mechanism of cross-flow instability for swept wing flow. These new results are combined with past explanations to provide a rough sketch for the entire flow field over the swept wing. From this new viewpoint there appears the mechanism of traveling waves, being induced by a stationary disturbance. Some uncertainties appearing in recent papers concerning this flow field are discussed. Among these uncertainties for which an explanation is provided, is the discrepancy of frequencies between the hot wire signal and the visualized flow pattern.Nomenclature
x
direction along a potential flow stream line
-
y
direction normal to a potential flow stream line
-
z
direction normal to bothx andy directions
-
U
mean velocity inx-direction
-
V
mean velocity iny-direction
-
x
direction along a disturbance
-
y
direction normal tox direction
-
u, v, w
fluctuating velocity components inx, y, z directions
-
U
velocity inx-direction with wall fixed coordinate
-
U
e
velocity of outer edge of boundary-layer
-
U
uniform flow velocity normal to leading edge
-
V
uniform flow velocity parallel to leading edge
-
Q
upstream velocity
-
N
rotation speed of an axisymmetric body
-
P
arbitrary point on a disk surface
-
r
radius to a pointP
-
R
0
radius of a disk or a cylinder
-
U
p
phase velocity of ring like vortices
-
T
position where wall streaks appear in the case of oil flow visualization
- Re
c,t
critical and transitional Reynolds numbers
-
angle of the spiral disturbance
-
boundary-layer thickness
-
angular velocity
-
sweep angle of a body
-
wave length of disturbance
-
kinematic viscosity of a fluid
With 11 Figures 相似文献
7.
The interaction between a dislocation and the impurity in KCl: Mg2+ (0.035 mol% in the melt) was investigated at 77–178 K with respect to the two models: one is the Fleischer's model and the other the Fleischer's model taking account of the Friedel relation. The latter is termed the F-F. The dependence of strain-rate sensitivity due to the impurities on temperature for the specimen was appropriate to the Fleischer's model than the F-F. Furthermore, the activation enthalpy, H, for the Fleischer's model appeared to be nearly proportional to the temperature in comparison with the F-F. The Friedel relation between effective stress and average length of the dislocation segments is exact for most weak obstacles to dislocation motion. However, above-mentioned results mean that the Friedel relation is not suitable for the interaction between a dislocation and the impurity in the specimen. Then, the value of H(T
c) at the Fleischer's model was found to be 0.61 eV. H(T
c) corresponds to the activation enthalpy for overcoming of the strain field around the impurity by a dislocation at 0 K. In addition, the Gibbs free energy, G
0, concerning the dislocation motion was determined to be between 0.42 and 0.48 eV on the basis of the following equation ln / = G
0/(kTp0)1 – (T/T
c)1/2
–1(T/T
c)1/2 + ln 0/where k is the Boltzmann's constant, T the temperature, T
c the critical temperature at which the effective stress due to the impurities is zero, p0 the effective shear stress without thermal activation, and 0 the frequency factor. 相似文献
8.
Measurements of the shear viscosity at saturated vapor pressure through the lambda transition indicate a singular behavior of the form |1 – (/)|=A
x
, (where =|1–(T/T
)|, with equal values for the critical exponent on both sides of the transition.Work sponsored by Consiglio Nazionale delle Ricerche, Rome (Italy). 相似文献
9.
The effect of antimony on the creep behaviour (dislocation creep) of a 25 wt% Cr-20 wt% Ni stainless steel with ~ 0.005 wt% C was studied with a view to assessing the segregation effect. The antimony content of the steel was varied up to 4000 ppm. The test temperature range was 1153 to 1193 K, the stress range, 9.8 to 49.0 MPa, and the grain-size range, 40 to 600m. The steady state creep rate,
, decreases with increasing antimony content, especially in the range of intermediate grain sizes (100 to 300m). Stress drop tests were performed in the secondary creep stages and the results indicate that antimony causes dislocations in the substructure to be immobile, probably by segregating to them, reducing the driving stress for creep.Nomenclature
a
Creep stress in a constant load creep test without stress-drop
-
A
Initial applied stress in stress-drop tests
-
Stress decrement
- (
A-)
Applied stress after a stress decrement,
- t
i
Incubation time after stress drop (by the positive creep)
-
C
Strain-arrest stress
-
i
Internal stress
-
s
s-component (=
i-
c)
-
Steady state creep rate (average value) in a constant load creep test
-
Strain rate at time,t, in a constant load creep test
-
New steady state creep rate (average value) after stress drop from
A to (
A-)
-
Strain rate at time,t, after stress drop. 相似文献
10.
Richard D. Sudduth 《Journal of Materials Science》2003,38(6):1123-1134
In a preceding publication this author introduced a new universal viscoelastic model to describe a definitive relationship between constant strain rate, creep and stress relaxation analysis for viscoelastic polymeric compounds. Since creep failure criterion for this model had not been addressed in detail in previous publications, selected creep failure criterion for this model were addressed in this study.The first manifestation of the yield stress failure criterion as applied to creep was elucidated at the intersection of the yield stress relaxation curve and the creep stress vs time curve. A second way to apply yield point failure criterion to creep failure was through the identification of a specific creep time associated with the limiting strain to yield, . The creep strain at occurs at the very end of the straight line portion of secondary creep and is also the strain at which tertiary creep appears to be initiated, itc = .As the strain increases from the inception of tertiary creep, itc, eventually a strain is reached where a calculation option using this model would require a step back in time to go to the next differential element of strain. Since going back in time is currently impossible, only a huge jump in strain obtained by another calculation option for the next element of time would be realistic. Since this critical creep strain, CC, is slightly greater than the inception of tertiary creep, if failure did not occur at the inception of tertiary creep then it would almost surely be expected to fail catastrophically at this condition.The near equivalency of the critical creep strain criterion and the yield strain criterion was found to be much more probable the lower the value of efficiency of yield energy dissipation such that 0 < n .4. 相似文献
11.
Lu Xing Qin Zuoxiang Zhang Yansheng Wang Xingyu Li Fengxian Ding Bingzhe Hu Zhuangqi 《Journal of Materials Science》2000,35(22):5597-5603
The paramagnetic-antiferromagnetic transition and the martensitic transformation of Fe-Mn (Mn 15–32 wt%) alloys have been investigated by resistivity, dilatometry and X-ray diffraction (XRD). The results show that paramagnetic-antiferromagnetic transition increases the resistivity and the volume of alloys, whereas the martensitic transformation reduces the resistivity and volume of alloys. The A
f
that was determined by the dilatometric method is not the temperature that martensites in the Fe-Mn alloys have reverse transformed to austenites completely. Mn additions reduce M
s, increase T
N and the lattice parameter of austenite in the Fe-Mn alloys. Both the antiferromagnetic transition and the martensitic transformation lead to an increase in the lattice parameter of austenite. The lattice parameters both above T
N and below T
N decrease linearly with temperature. The lattice parameter below M
s increases first and then decreases. Moreover, the (110) and (002) atomic planes in the Fe-15Mn-0.15C alloy are separated into two peaks: 2 for (002) is 44.16°, 2 for (110) is 44.47°. 相似文献
12.
We studied the low-temperature energy gap 2
0
on Bi
2
Sr
2
CaCu
2
o
8+
(Bi2212) and La
2–x
Sr
x
CuCO
4
(La214) systematically over a wide range of doping level p using STS, break junction tunneling spectroscopy, Raman scattering and low-T electronic specific heat data. We have also studied the electronic specific heat of La214 in the normal state at T > T
c
, and confirmed that pseudogap behavior appears at around T*, below which the in-plane resistivity and magnetic susceptibility tend to be slightly suppressed. Similar suppression appears in and of Bi2212 below the onset temperature of pseudogap T*. It is pointed out in the present study that 2
0
is closely related to T* in both Bi2212 and La214 systems; T* 2
0
/4.3k
B
. It is also pointed out that 2
0
is in almost linear proportion to k
B
T
max
( T*), where T
max
is the temperature exhibiting a broad peak in –T curves and k
B
T
max
can be considered to give a measure of the effective antiferromagnetic exchange energy J
eff. The factors in 2
0
k
B
T
max
J
eff
are 1 for La214 and 2 for Bi2212, respectively. We also report that in both Bi22l2 and La214 systems T
c
roughly scales with p
0
except in highly doped samples, where T
c
2
0
. 相似文献
13.
L. T. Grebenshchikov M. A. Ivashevskii V. A. Kudryavtsev K. B. Panfilovich A. A. Pyatin 《Journal of Engineering Physics and Thermophysics》1993,64(3):266-271
An unconventional unit for experimentally studying the optical thermophysical properties of materials over a wide temperature range is described. Results are presented of studying the temperature function and dispersion of the absorption index for the condensed phase of the combustion products of a metalbearing fuel and of the emittance of fiber fireproof materials.Notation K
spectral absorption coefficient
- D
spectral transmission coefficient
-
spectral absorption index
-
wavelength
- d
sample thickness
- ds
surface layer thickness
- I
spectral intensity of radiation
- ,
spectral and total emittances
Kirov Polytechnical Institute. Kazan Chemical Engineering Institute, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 3, pp. 330–336. March, 1993 相似文献
14.
We examine the applicability of the standard McMillan inversion of Eliashberg's equations for superconductors with a nonconstant electronic density of statesN(). We do this usign simple models forN() and a realistically shapedN() taken from recent band structure work for Nb3Sn. It turns out that peak structure inN() near F may lead to gross errors in the derived Eliashberg function 2F() when the energy dependence ofN() is omitted in the inversion procedure. For Nb3Sn, this leads to a 40% overestimate of when 2F() is evaluated via the standard McMillan program. 相似文献
15.
Erik Paul van Klaveren Jan Michels Jan Schouten 《Journal of Low Temperature Physics》1998,111(3-4):413-418
In order to obtain a better notion of the experimental results in our laboratory, Monte Carlo calculations have been performed of the N
2-Ar crystal on the N
2-rich side, in the p-T region where the and phases exist in pure N
2. Considering the enthalpy, the system prefers the Ar atoms to be located on the sphere positions. The * phase is present for mixtures down to
but is most likely metastable. The *-* transition shifts to lower temperatures with decreasing
. The 2
nd
order transition within the phase continues to exist to even smaller
. In contrast to the * -* transition, the transition temperature for the 2
nd
order transition does not shift to lower temperatures. For a mixture of
it is within 5 K from the pure 2
nd
order transition at a pressure of 7.0 GPa. 相似文献
16.
The dielectric properties of chemically vapour-deposited (CVD) amorphous and crystalline Si3N4 were measured in the temperature range from room temperature to 800° C. The a.c. conductivity (
a.c.) of the amorphous CVD-Si3N4 was found to be less than that of the crystalline CVD-Si3N4 below 500° C, but became greater than that of the crystalline CVD-Si3N4 over 500° C due to the contribution of d.c. conductivity (
d.c.). The measured loss factor () and dielectric constant () of the amorphous CVD-Si3N4 are smaller than those of the crystalline CVD-Si3N4 in all of the temperature and frequency ranges examined. The relationships of
n-1, (-
)
n-1 and/(-
) = cot (n/2) (were observed for the amorphous and crystalline specimens, where is angular frequency andn is a constant. The values ofn of amorphous and crystalline CVD-Si3N4 were 0.8 to 0.9 and 0.6 to 0.8, respectively. These results may indicate that the a.c. conduction observed for both of the above specimens is caused by hopping carriers. The values of loss tangent (tan) increased with increasing temperature. The relationship of log (tan) T was observed. The value of tan for the amorphous CVD-Si3N4 was smaller than that of the crystalline CVD-Si3N4. 相似文献
17.
Michio Inagaki Hiroshi Furuhashi Tomomasa Ozeki Shigeharu Naka 《Journal of Materials Science》1973,8(3):312-316
The relations between the effective Debye parameter and lattice strain are investigated on some non-metallic crystalline powders, CoO, Co0.5 Mg0.5O, CoAl2O4, TiO2, CaF2, BaTiO3 and graphite. The effective Debye parameter B
eff was determined from the integrated intensities of X-ray diffraction lines with different sin /-values and the lattice strain, , was determined from the half-widths of the diffraction lines. Both B
eff and increased with increase in grinding time and pressure. B
eff showed a relatively sharp increase, but tended to saturation. However, increased slowly even after prolonged grinding, and B
eff increased with increase in . When >0.2×10–2, however, B
eff tended to a limit. The limiting values of B
eff were varied from sample to sample. An attempt was made to explain the changes of B
eff and with grinding and compression to large shear by the introduction of various defects into the structure. B
eff was found to give some information on the deformed structure of crystalline powders. 相似文献
18.
P. J. Harrop 《Journal of Materials Science》1969,4(4):370-374
An earlier treatment of temperature coefficient of capacitance,
c [1] has been extended to include most solids. Materials are divided into those with given ranges of permittivity, , and temperature coefficient of polarisability. It appears that, for low dielectric loss, high permittivity glasses, like simple ionic compounds, always have a positive
c, whereas paraelectrics and polymers have negative
c. Ferroelectrics can have any value of
c. Limitations in
c and for given classes of solid are discussed. 相似文献
19.
W. B. Hillig 《Journal of Materials Science》1994,29(4):899-920
When a matrix crack encounters a fibre that is inclined relative to the direction of crack opening, geometry requires that the fibre flex is bridging between the crack faces. Conversely, the degree of flexing is a function of the crack face separation, as well as of (1) the compliance of the supporting matrix, (2) the crossing angle, (3) the bundle size, and (4) the shear coupling of the fibre to the matrix. At some crack face separation the stress level in the fibre bundle will cause it to fail. Other bundles, differing in size and orientation, will fail at other values of the crack separation. Such bridging contributes significantly to the resistance of the composite to crack propagation and to ultimate failure. The stress on the composite needed to produce a given crack face separation is inferred by analysing the forces and displacements involved. The resulting model computes stress versus crack-opening behaviour, ultimate strengths, and works of failure. Although the crack is assumed to be planar and to extend indefinitely, the model should also be applicable to finite cracks.Glossary of Symbols
a
radius of fibre bundle
-
C
2
f
/aE
f
- *
critical failure strain of fibre bundle
- b
bending strain in outer fibre of a bundle
- c
background strain in composite
- f
axial strain in fibre
- s
strain in fibre bundle due to fibre stretching = f
- ()
strain in composite far from crack
-
E
Young's modulus of fibre bundle
-
E
c
Young's modulus of composite
-
E
f
Young's modulus of fibre
-
E
m
Young's modulus of matrix
-
f()
number density per unit area of fibres crossing crack plane in interval to + d
-
F
total force exerted by fibre bundle normal to crack plane
-
F
s
component of fibre stretching force normal to crack plane
-
F
b
component of bending force normal to crack plane
-
G
m
shear modulus of matrix
-
h
crack face opening relative to crack mid-point
-
h
m
matrix contraction contribution to h
-
h
f
fibre deformation contribution to h
-
h
max
crack opening at which bridging stress is a maximum
-
I
moment of inertia of fibre bundle
-
k
fibre stress decay constant in non-slip region
-
k
0
force constant characterizing an elastic foundation (see Equation 7)
-
L
exposed length of bridging fibre bundle (see Equation 1a)
-
L
f
half-length of a discontinuous fibre
-
m, n
parameters characterizing degree of misalignment
-
N
number of bundles intersecting a unit area of crack plane
-
P
b
bending force normal to bundle axis at crack midpoint
-
P
s
stretching force parallel to bundle axis in crack opening
-
Q()
distribution function describing the degree of misalignment
-
s
f
fibre axial tensile stress
-
s
f
*
fibre tensile failure stress
-
S
stress supported by totality of bridging fibre bundles
-
S
max
maximum value of bridging stress
-
v
fibre displacement relative to matrix
-
v
elongation of fibre in crack bridging region
-
u
coh
non-slip contribution to fibre elongation
-
U
fibre elongation due to crack bridging
-
v
overall volume fraction of fibres
-
v
f
volume fraction of bundles
-
v
m
volume fraction matrix between bundles
-
w
transverse deflection of bundle at the crack mid-point
-
x
distance along fibre axis, origin defined by context
-
X
distance between the end of discontinuous fibre and the crack face
-
X
*
threshold (minimum) value of X that results in fibre failure instead of complete fibre pullout
-
y
displacement of fibre normal to its undeflected axis
-
Z()
area fraction angular weighting function
-
tensile strain in fibre relative to applied background strain
- *
critical value of to cause fibre/matrix debonding
-
angle at which a fibre bundle crosses the crack plane
-
(k
0/4EI)1/4, a parameter in cantilever beam analysis
- vm
Poisson's ratio of matrix
-
L (see Equation 9)
-
shear stress
- *
interlaminar shear strength of bundle
- d
fibre/matrix interfacial shear strength
- f
frictional shear slippage stress at bundle/matrix interface
-
angular deviation of fibre bundle from mean orientation of all bundles
-
angle between symmetry axis and crack plane 相似文献
20.
In this paper the second-order differential equation with time-dependent damping coefficientx + cos (2t) x + x = 0,will be studied. In particular the coexistence of periodic solutions corresponding with the vanishing of domains of instability is investigated. The coexistence of -periodic solutions occurs for 4n
2 where n is integer. This implies that the instability area which is emanating from =4n
2 in the – stability diagram disappears. In applications, this equation can be considered as a model equation for the study of rain-wind-induced vibrations of a special oscillator.on leave as a PhD reseacher at Delft University of Technology, The Netherlands 相似文献