摘要:

Copper and aluminum samples were subjected to cyclic stress and run to fatigue while being held in an x‐ray beam. Small angle scattering intensities were recorded at various stages of the fatigue life. These intensities were found to increase with the number of elapsed stress cycles.The observed angular dependence and intensity of the scattered radiation agrees most nearly with a double Bragg scattering mechanism. The relation of the fatigue mechanism to the formation of small angle subgrain boundaries responsible for the double Bragg scattering is not clear‐cut. However, the evidence favors the view that the formation of subgrains, while probably necessary to the propagation of the fatigue crack, is not sufficient either for its formation or propagation. Complete annealing of the scattering was not possible, indicating that recrystallization does not take place following cyclic stress of the order of one‐fourth the yield stress. No evidence exists for a widespread formation of voids in the fatigued specimen.

ISSN:0021-8979    

DOI:10.1063/1.1735212

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The work functions of a number of commercial‐grade silicon‐carbide single crystals have been obtained in high vacuum (p<10−9mm Hg). Low‐energy electron‐diffraction studies have also been made for one of these samples. Surfaces cleaned by argon‐ion bombardment and annealing appeared to contain an excess of carbon. Heating for long periods of time at 1000°C also appeared to produce surfaces which were nonstoichiometric. Oxygen was adsorbed at room temperature on the ion‐bombardment cleaned surfaces with a sticking coefficient of the order of 0.01. Differences in adsorption properties were noted which were probably associated with asymmetry in atomic species on different crystal faces. Work‐function values on opposite faces of any crystal were the same. Hydrogen exposure resulted in work‐function decreases only in the presence of a heated filament. Under similar conditions of ion bombardment and high‐temperature heating, the SiC surfaces appeared to be more stable than those of silicon crystals.

ISSN:0021-8979    

DOI:10.1063/1.1735213

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Current shape charge theory and experiment do not provide the requisite basis for the development of a slug‐free charge suitable for oil well perforation. Considerations and experiments are discussed which have led to the design of a new type charge. Basically the charge has a thicker than conventional liner containing a low melting point metal which melts during collapse, forming a liquid slug which is dispersed.

ISSN:0021-8979    

DOI:10.1063/1.1735214

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The case of a uniform electric field, infinite in extent, abruptly applied to the plane face of a semi‐infinite conductor is considered. The amplitude of the field as a function of distance into the conductor and of time is then determined for different conductivities. The time element and distance for ignoring the displacement current term in Maxwell's equations is determined. Finally the time and space nature of the applied electric field at distances far removed from the semi‐infinite conductor is considered.

ISSN:0021-8979    

DOI:10.1063/1.1735215

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The magnetostatic solutions of ferrimagnetic resonance in ferrite spheres are briefly derived. General and specific solutions are given for values ofnup to five for the magnetostatic potentials, rf distributions of magnetization, and fields for resonance. Some experimental results are given and compared with the theory.

ISSN:0021-8979    

DOI:10.1063/1.1735216

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The influence of the shape of the specimen upon the measured value of magnetostriction is a matter of importance. The classical thermodynamical calculation of Becker applies to specimens in like magnetic fields and consequently compares bodies with unlike intensities of magnetization. In the present paper use is made of the principle of virtual work to make a calculation of the form effect as dependent upon the intensity of magnetization. The form effect for an ellipsoid in an extended uniform field is found to be a constrictive strain of the magnitude&Dgr;A11=−(1−2&mgr;)ENI22, where &Dgr;A11is the form effect in strain, &mgr; is Poisson's ratio,Eis Young's modulus,Nis the coefficient of self‐demagnetization, andIthe intensity of magnetization. Above saturation the form effect is&Dgr;A11=−(1−2&mgr;)ENIs22, whereIsis the saturation value ofI.The meaning of the term form effect has been expanded to include not only the change in strain in the specimen resulting from the shape of the specimen itself, but also the change resulting from the position of the specimen relative to the magnetizing apparatus. A calculation of the form effect in this extended sense is made for two useful experimental arrangements; one where a specimen is sandwiched between two movable rods and the other where the specimen is situated in the fixed gap of a magnet. For the first case it is found that the form effect depends upon the self‐demagnetization of the entire ferromagnetic arrangement and not of the specimen itself. In the second case, the form effect is dependent upon the ratio of gap energy to the volume of the ferromagnetic system and can be small, subject to the qualification that the form effect does not include the effects of any stresses that develop within the gap.

ISSN:0021-8979    

DOI:10.1063/1.1735217

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The figure of merit for a single stage Peltier heat pump is optimized in the region of partial Fermi degeneracy. A more rigorous treatment is presented of the properties of a cascade operating at maximum coefficient of performance. Finally, the heat leak in the absence of current flow is called to attention as a serious problem in devices with excess capacity.

ISSN:0021-8979    

DOI:10.1063/1.1735218

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

An investigation has been made to determine the conditions under which the voltage sustained by a 2‐ft length of ion‐accelerator tube may be made proportional to the length of the tube. It has been found that such linearity may be obtained if the tube is segmented at 4½‐in. intervals by diaphragms which are so arranged that no straight path is possible from one end of the tube to the other. No significant deterioration in performance of the tube was observed when axial holes were made in each diaphragm up to ¾ in. in diameter. The voltage gradient realized on these tests was 60 kv/cm.

ISSN:0021-8979    

DOI:10.1063/1.1735219

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

An experimental study has been made of the properties and characteristics of a glow discharge to a nearly spherical hollow cathode. Current densities in excess of 0.5 amp/cm2can be drawn from the cathode with negligible deterioration from sputtering. In neon, the discharge exhibits a stable and reproducible negative volt‐ampere characteristic at currents of a few milliamperes. At these currents, probe measurements indicate the plasma in the hollow contains ∼1‐v electrons in concentrations greater than 1013/cm3.

ISSN:0021-8979    

DOI:10.1063/1.1735220

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The theory of mechanical breakdown in bundles of Class A‐2 fibers, whose strength depends on the speed of measurement, is used to find the conditions under which time‐dependence effects can be neglected in calculations of relationships between the strength of bundles and the strength of their constituent filaments. (The classical theories of the strength of bundles do not consider time dependence.) Tables and graphs are presented which give the ratio, &egr;A, of the strength of an infinite ideal bundle to the mean strength of its filaments as a function of the coefficient of variation, &sgr;1/E1{f*}, in the strength of the filaments. It is shown that, under certain limiting conditions, &egr;Afor an infinite bundle of Class A‐2 fibers is the same as it would be for an infinite bundle of classical fibers with an equal value of &sgr;1/E1{f*}, and a numerical investigation is made of the rapidity with which this limiting behavior is approached.

ISSN:0021-8979    

DOI:10.1063/1.1735221

出版商:AIP    

年代:1959

数据来源: AIP