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排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Experimental results of the study of superplastic behaviour in Zn-0·35 wt. % Al-0·25 wt. % Cd alloy are presented. The attention has been paid to the influence of temperature on stress-strain curves, ductility, strain rate sensitivy parameterm and activation energy of superplastic flow. The best superplastic properties have been established at temperatures T370 K (0·53 Tm): ductilityA=600% and parameterm=0·56. A fast grain growth observed at temperaturesT 380 K has been suggested to be responsible both for the decrease in ductility and parameterm values and for the origin of an anomaly in the decreasing temperature dependence of flow stress. The measurements of activation energy have shown an expected decrease in activation energy at the transition from the non-superplastic region at lower temperatures to the superplastic region at higher temperatures. Significant transient effects after strain rate changes have been observed. The experimental results obtained in the Zn-Al-Cd alloy have been compared with those obtained in binary Zn-1·1 wt. % Al alloy and discussed from the point of view of possible models of structural superplasticity. 相似文献
992.
993.
994.
Expressing the influence of reservoirs (lattice modes, solvent etc.) on the exciton or electron propagation in homogeneous systems via two relaxation times in the Agranovich and Galanin model, the convolutionless Generalized Master Equations for the site occupation probabilities are derived. Two different projection operator techniques are used. Identity of the two approaches is verified for a dimer and physical contents of the result are discussed. 相似文献
995.
Hardening in modulated structure is evaluated using the periodic approximation. The critical shear stress increment due to the periodic structure is calculated in the constant line energy approximation. The results are applicable to any periodic structure (concentration waves must be neither homophase nor symmetric) exerting on the dislocation local glide forces with an amplitude smaller than ( denotes the line energy of corresponding straight dislocation directed along the concentration variations with the wave vector). In the zero approximation, the critical forceb is then simply the glide force on the straight dislocation averaged along its length in its most hardened position. 相似文献
996.
The thermal expansion coefficient of cadmium fluoride crystals has been measured over the temperature range of 300 to 1070 K. The data fit well to measurements done by other authors in the range 80–300 K. At temperatures above 1070 K the thermal expansion coefficient shows an anomalous behaviour which has been attributed to the formation of cadmium oxide on the surface of the sample. 相似文献
997.
The paper deals with the influence of a magnetic field on the function of a thermionic energy converter. It derives a relation for the effect of the magnetic field on the converter current in a diffusion regime and gives measurements for a quasi-vacuum and diffusion regime of the converter. 相似文献
998.
A. Kochanovská 《Czechoslovak Journal of Physics》1965,15(7):513-525
In this paper the possibility is analyzed of using the ratio method to determine the biaxial stress component
x
in an arbitrary direction from two photographs, one taken with the primary beam incident perpendicularly and rotating film holder and the second photograph with the primary beam incident obliquely and film holder stacionary or oscillating in a small angular range. A relation is derived for the value of
x
based on measurements of the diameters of the diffraction circles in the corresponding azimut, and a relation for estimating the magnitude of the percentual error of the value of
x
thus determined as compared with the real value of
x
.It is shown in the case of aluminium in three typical stress states (circularly symmetrical stress distribution, unaxial state, torsional stress) that the error in determining
x
, caused by using the ratio method, is quite unimportant for application in technical practice and is much smaller than when applying the ratio methods to the determination of the sum of the two principal stresses from one photograph taken with the primary beam incident perpendicularly. The application of the ratio method for determining
x
gives simultaneously the possibility of using this method for solving the general problem, i.e. of determining the two principal stresses as to their magnitude and direction. 相似文献
999.
Miroslav Voříšek 《Czechoslovak Journal of Physics》1955,5(1):89-90
1000.
, - 17,6 , . , (8±4)·10–23, (7±4)·10–23 (4±2)·10–23
2. , - . 相似文献