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1.
B. A. Kolovandin N. N. Luchko T. V. Sidorovich V. A. Sosinovich 《Journal of Engineering Physics and Thermophysics》1982,42(1):36-40
The problem of universal simulation of the dynamics of a turbulent velocity field (universal in the sense of arbitrary values of the Reynolds turbulence number) is treated on the basis of the moment model in the second approximation.Notation ¯q2
i
2
double the kinetic turbulence energy
-
u
2
=5v¯q2/u
Taylor turbulence scale squared
- u=v1/xk)2>
kinetic-energy dissipation function
- NRe,=¯q2u /
Reynolds turbulence number
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 46–52, January, 1982. 相似文献
2.
Deformation approach to the evaluation of the period of initiation and growth of fatigue macrocracks
We performed experimental investigation of the opening displacements of the contours of stress concentrators (notches and cracks) for various amplitudes of cyclic loading. On the basis of experimental results, we propose a new deformation parameter
t
which is a function of the notch (crack) tip opening displacement , namely,
t
/(+d*), where is the radius of the tip of the notch andd* is the characteristic size of the prefracture zone. It is shown that this parameter uniquely determines the number of cyclesN
l to the initiation of a fatigue macrocrack independently of the geometry of the specimens and stress concentrators in elastic and elastoplastic materials, i.e., the dependence of
t
onN
1 is a characteristic of the material. It is experimentally demonstrated that this dependence enables one to quantitatively describe the process of fatigue fracture both in the stage of initiation of macrocracks and their propagation.Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 31, No. 5, pp. 7–21, September – October, 1995. 相似文献
3.
Kazutaka Kudo Takashi Noji Yoji Koike Terukazu Nishizaki Norio Kobayashi 《Journal of Low Temperature Physics》2003,131(3-4):725-729
We have investigated the magnetic susceptibility, , and the thermal conductivity, , in magnetic fields for the four-leg spin-ladder system La2Cu2O5 single crystal. The in a magnetic field parallel to the ladder exhibits a kink at 130 K in correspondence to the magnetic ordering. The along the ladder exhibits a peak at 25 K and a shoulder at 14 K, which are probably related to the thermal conductivity due to magnons, magnon, and that due to phonons, phonon, respectively. The perpendicular to the ladder, on the other hand, exhibits only one broad peak related to phonon. The observed large anisotropy of has been explained based upon the anisotropy of magnon. 相似文献
4.
I. R. Whitaker D. G. McCartney N. Calder W. M. Steen 《Journal of Materials Science》1993,28(20):5469-5478
The microstructural development of the Al-Li-Cu-Mg-Zr alloy 8090 has been studied after autogenous CO2 laser welding. Sheets ranging in thickness from 1–4 mm were welded at speeds of between 20–120 mm s–1 and powers from 1.5–3.8 kW. Optical microscopy, scanning and transmission electron microscopy were used to study the as-received base metal, the heat-affected zone and the solidified fusion zone. The base metal was supplied in a superplastically formable condition and thus had an unrecrystallized grain structure containing 1–2 m sized sub-grains with sub-micrometre and precipitates in the matrix. In the fusion zone, the as-solidified grain structure was columnar at the interface with the base metal but became equiaxed in the central region of the weld pool. The weld depth and top bead width both increased with decreasing welding speed and increasing beam power within the limits investigated. The fusion zone microstructure was cellular-dendritic. Intermetallic precipitates, which are rich in copper, magnesium, silicon (and presumably lithium), formed in the cell/dendrite boundaries. Very fine-scale precipitates were present in the as-solidified -Al matrix but there was no evidence for the , S and T1 phases. The heat-affected zone was only 100 m wide and was characterized by regions of partial melting. Radiographs of welds reveal that porosity occurred predominantly along the weld centre-line. In partial penetration welds, two types of pores were observed: near spherical and irregular. However, in fully penetrating welds, only the spherical type of porosity was present. Overall volume fractions of porosity were measured from metallographic sections and were found to vary with welding speed and weld type, i.e. partial or full penetration. 相似文献
5.
J. R. White 《Journal of Materials Science》1981,16(12):3249-3262
The two-site model is developed for the analysis of stress relaxation data. It is shown that the product of d In (–
)/d and (-
i) is constant where is the applied stress,
i is the (deformation-induced) internal stress and
= d/dt. The quantity d In (
)/d is often presented in the literature as the (experimental) activation volume, and there are many examples in which the above relationship with (-
i) holds true. This is in apparent contradiction to the arguments that lead to the association of the quantity d In (–
)/d with the activation volume, since these normally start with the premise that the activation volume is independent of stress. In the modified theory presented here the source of this anomaly is apparent. Similar anomalies arise in the estimation of activation volume from creep or constant strain rate tests and these are also examined from the standpoint of the site model theory. In the derivation presented here full account is taken of the site population distribution and this is the major difference compared to most other analyses. The predicted behaviour is identical to that obtained with the standard linear solid. Consideration is also given to the orientation-dependence of stress-aided activation. 相似文献
6.
The interaction of grain size and precipitation strengthening has been studied in a Ti-8 wt % Al-0.25 wt %Si alloy. Grain sizes varying from 9 to 90m were produced by warm-working and annealing the alloy in the single--phase field. A uniform distribution of the coherent
2 particles in the matrix was produced by ageing the alloy in the two-phase ( +
2) field. The yield strength Hall-Petch slopes of the alloys with and without the 2 precipitates were found to be nearly equal, indicating that the precipitation and grain-boundary strengthening are linearly additive. While specimens containing no precipitates exhibited a high ductility for all grain sizes, the ductility of the specimens with the
2 particles decreased drastically with increasing grain size. TEM examination of the specimens containing the precipitates revealed a highly planar, localized slip and SEM examination of the fracture surfaces of these specimens revealed a transition in fracture behaviour from highly dimpled to mixed cleavage and intergranular with increasing grain size. 相似文献
7.
M. Wang N. H. Ladizesky K. E. Tanner I. M. Ward W. Bonfield 《Journal of Materials Science》2000,35(4):1023-1030
Hydroxyapatite reinforced high density polyethylene composite (HAPEX) has been developed for bone substitution. To improve its mechanical properties, HAPEX was hydrostatically extruded at different extrusion ratios after compression moulding. Substantial increases in the tensile and flexural properties of both unfilled polyethylene and HAPEX were achieved. It was evident that the higher the extrusion ratio, the stiffer and the stronger the extruded rods. The ductility of HAPEX was also significantly enhanced by hydrostatic extrusion. Hydrostatically extruded HAPEX possesses mechanical properties that are within the bounds for human cortical bone, which indicates its potential for load-bearing skeletal implant applications. 相似文献
8.
Masaaki Isobe Koji Kimoto Eiji Takayama-Muromachi 《Journal of Low Temperature Physics》2003,131(3-4):737-741
We have studied the magnetic state from a viewpoint of crystallographic features of the 1-D chain compound Ca0.824CuO2. A possible spin-hole arrangement in the magnetically coexisting state was determined by analyzing the local structural distortion in the CuO2 chain by means of a modulated-crystal-structure analysis. The essential periodic sequence expected is (: up- and down-spin, : hole), which can be regarded as a kind of spin-1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain. 相似文献
9.
Å. Karlsson 《Journal of Low Temperature Physics》1969,1(1):59-64
De Haas-van Alphen frequencies not previously reported have been measured for -PdIn and -CuZn. The results for PdIn suggest a reinterpretation of some of the previous results and offer an explanation of a previously unexplained set of de Haas-van Alphen frequencies in PdIn and AgZn. A recent nonlocal pseudo-potential model by Taylor can account for the experimental results reported here as well as the earlier data.National Research Council of Canada Postdoctorate Fellow. 相似文献
10.
The indentation hardness and elastic modulus of leadframe materials that consist of Cu alloy substrate and Ni/Pd bi-layer films of differing thicknesses are characterised using the micro-hardness and nano-indentation tests. The true hardness of the individual substrate and film layers is evaluated based on the empirical relationship between the measured composite hardness and the volume of plastically deformed material of film layers. It is found that the composite hardness determined from the nano-indentation test increases rapidly toward a peak at extremely low indentation depth of less than about 20–30 m for all materials studied, due mainly to the finite value of the indenter tip radius and the rough surface of the specimen on the nano-scale. The composite hardness for the coated specimens decreases with further increasing indentation depth toward the hardness value of the substrate, because of the strong influence of the film/substrate interaction and the indentation size effect. The nano-indentation test in general gives higher true hardness values than those obtained from the micro-hardness test. Nevertheless, the relative hardness values of the substrate and films determined from the two tests are consistent. The hardness of Ni film is about 20 to 50% greater than that of Cu alloy, whereas the hardness of Pd film is 7 to 11 times the Ni film in the nano-indentation test. 相似文献
11.
A. E. Koshelev 《Journal of Low Temperature Physics》2005,139(1):111-125
No Heading In presence of the Josephson vortex lattice in layered superconductors, small c-axis magnetic field penetrates in the form of vortex chains. In general, structure of a single chain is determined by the ratio of the London [] and Josephson [J] lengths, = /J. The chain is composed of tilted vortices at large s (tilted chain) and at small s it consists of crossing array of Josephson vortices and pancake-vortex stacks (crossing chain). We study chain structures at the intermediate s and found two types of phase transitions. For 0.6 the ground state is given by the crossing chain in a wide range of pancake separations a [2–3]J. However, due to attractive coupling between deformed pancake stacks, the equilibrium separation can not exceed some maximum value depending on the in-plane field and . The first phase transition takes place with decreasing pancake-stack separation a at a = [1 – 2]J, and rather wide range of the ratio , 0.4 0.65. With decreasing a, the crossing chain goes through intermediate strongly-deformed configurations and smoothly transforms into the tilted chain via the second-order phase transition. Another phase transition occurs at very small densities of pancake vortices, a [20 – 30]J, and only when exceeds a certain critical value 0.5. In this case small c-axis field penetrates in the form of kinks. However, at very small concentration of kinks, the kinked chains are replaced with strongly deformed crossing chains via the first-order phase transition. This transition is accompanied by a very large jump in the pancake density.PACS numbers: 74.25.Qt, 74.25.Op, 74.20.De 相似文献
12.
The interaction of an applied stress with the displacive shear during the martensitic transformation determined theK-S variants which formed in three types of tensile specimens, with tensile directions of 0°, 45° and 90° to a rolling direction respectively. The 3–6, 4–5 and 1–3 variants in a 0°-specimen, 1–5 and 4–5 variants in a 45°-specimen and 4-4 and 3–6 variants in a 90°-specimen are chosen asK-S variants which have the maximum value ofU/ in respective tensile directions. These variants are related to the occurrence of martensite with particular orientations as (100), (110) and (211). 相似文献
13.
The structure at room temperature of a quenched TA6V titanium alloy has been investigated. This structure is + or + according to the treatment temperature; it is always metastable. During ageing the grains decomposed by the reaction + + +; this decomposition was accompanied by a large increase of the 0.2% yield stress. No structural modification was observed in. The and phase of TA6V were separately investigated in the form of single-phase alloys. The hardness of was insensitive to ageing, while was considerably hardened by and; we deduced that the strengthening of the minor phase during ageing is mainly responsible for the hardening of TA6V. 相似文献
14.
The problem of freezing of pure water in a round pipe is treated with due regard for convection under asymmetric thermal boundary conditions in the absence of motion along the pipe. The problem is solved numerically using the control volume approach, SIMPLER algorithm, and the enthalpy method. Results are obtained for three Grashof (Gr) and six Biot (Bi) numbers: Gr = 1.55 × 106, Bi = 0.305 (0 < ), Bi = 0.044 ( < 2); Gr = 1.24 × 107, Bi = 0.610 (0 < ), Bi = 0.087 ( < 2); Gr = 9.89 × 107, Bi = 1.220 (0 < ), Bi = 0.174 ( < 2). The correctness of calculation of the problem disregarding free-convection flows is analyzed. 相似文献
15.
V. L. Sergeev A. S. Strogii V. A. Tsurko 《Journal of Engineering Physics and Thermophysics》1982,42(1):25-30
Results are presented from a numerical analysis and experimental study of the enthalpy and velocity distributions along and across a subsonic plasma air jet.Notation x, r
axial and radial coordinates
- u, v
axial and radial components of velocity
-
density
-
viscosity
-
emissivity
- r0.5
radius at which local value of velocity or enthalpy is half its axial value
- ,
radii of dynamic and thermal boundary layers
- q
heat flux, kW/m2
- h, hw
stagnation enthalpy and enthalpy at wall temperature, kJ/kg
- p, p
stagnation pressure and static pressure, Pa
- R
radius of curvature of spherical front part of body
Indices 0
teconditions at nozzle edge
- m
conditions on jet axis
-
conditions on outer boundary of jet
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 34–39, January, 1982. 相似文献
16.
B. A. Grigor'ev A. M. Ishkhanov 《Journal of Engineering Physics and Thermophysics》1981,41(3):998-1005
The thermal conductivity of hydrocarbons in the naphthene group has been experimentally determined. An equation is now proposed for calculating the thermal conductivity over the given temperature and pressure ranges.Notation
thermal conductivity
- 20 and 30
values of the thermal conductivity at 20 and 30°C, respectively
- t0,P0
thermal conductivity at t0, p0
- t p
thermal conductivity at temperature t and under pressure P
-
change in thermal conductivity
- P
pressure
- Pmelt
melting pressure
- P0
atmospheric pressure
- t0
20°C temperature
- T, t
temperature
- Tcr
critical temperature
-
temperature coefficient of thermal conductivity
- 20
temperature coefficient of density
-
density
- 20
density at 20°C
- cr
critical density
- M
molar mass
- =T/Tcr
referred temperature
- v
specific volume
- v0
specific volume at 20°C
- v
change in specific volume
- 3 0
a coefficient
- B (t)
a function of the temperature
- S
a quadratic functional
- Wi,
weight of the i-th experimental point
- i
error of the i-th experimental value of thermal conductivity
- B y, =0.6
value of B (t) at T = 0.6Tcr
- B
= B (t)/B, =0.6
referred value of coefficient B (t)
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 3, pp. 491–499, September, 1981. 相似文献
17.
Effect of crystalline phase, orientation and temperature on the dielectric properties of poly (vinylidene fluoride) (PVDF) 总被引:1,自引:0,他引:1
The effect of crystalline phase, uniaxial drawing and temperature on the real () and imaginary () parts of the relative complex permittivity of poly (vinylidene fluoride) (PVDF) was studied in the frequency range between 102 and 106 Hz. Samples containing predominantly and phases, or a mixture of these, were obtained by crystallization from a DMF solution at different temperatures. phase samples were also obtained from melt crystallization and from commercial films supplied by Bemberg Folien. Different molecular orientations were obtained by uniaxial drawing of and phase samples. The results showed that the crystalline phase exerts strong influence on the values of and , indicating that the a relaxation process, associated with the glass transition of PVDF, is not exclsively related to the amorphous region of the polymer. An interphase region, which maintains the conformational characteristics of the crystalline regions, should influence the process decisively. The molecular orientation increased the values of for both PVDF phases and modified its dependence with temperature over the whole frequency range studied. The influence of the crystallization and molecular orientation conditions on the dc electric conductivity (dc) were also verified. The value of dc was slightly higher for samples crystallized from solution at the lowest temperature and decreased with draw ratio. 相似文献
18.
Precipitation characteristics in a powder metallurgy (Al-4wt% Cu)-SiC whisker composite were investigated using transmission electron microscopy, differential scanning calorimetry, and macrohardness measurement. The results of macrohardness measurement show that the peak ageing is significantly retarded in the SiC whisker-reinforced Al-Cu alloys. It is shown that the suppression of formation plays an important role in the retarded age hardening. The suppression of formation is attributed to a high density of dislocations due to the difference in the thermal contraction between the whiskers and matrix. Numerical analysis was performed to estimate the misfit strain generated during cooling near the whiskers. The results indicate that a high density of dislocations should be developed by the relief of the misfit strain. 相似文献
19.
M. G. Boguslavskii V. Ts. Vol'pert E. E. Sharova V. M. Éliashberg 《Measurement Techniques》1973,16(6):830-832
Conclusions The designed highly sensitive autocollimator with automatic aiming has a reading stability of ±0.01 and a linearity of ±0.02 within an automatic aiming range of ±6.The system has a response time =0.1 sec and a static aiming error less than 0.005.To realize the maximum measuring accuracy of which the autocollimator is capable, the instrument must be protected from temperature fluctuations and air currents, and placed on a stable fixed base.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 25–26, June, 1973. 相似文献
20.
Phase relationships in Si3N4-AIN-MxOy systems involving -sialon, where M represents lithium, magnesium, calcium, yttrium, neodymium, samarium, gadolinium, dysprosium, erbium and ytterbium are outlined. Their implications for the formation and fabrication of single-phase -sialon and two-phase : sialon ceramics are discussed. 相似文献