摘要:

In this article an attempt is made to examine the goals of current and of possible future types of research concerned with the non‐elastic deformation of metals. It is found that an understanding of non‐elastic deformation would be enhanced by research upon the following topics: 1. The anelasticity associated with the viscous behavior of grain boundaries and the at least temporary viscous behavior of slip bands. 2. The mechanics of the initiation and growth of twin bands. 3. The mechanics of the initiation and growth of slip bands, including the drop in resistance to deformation which accompanies the initial slip bands. 4. The mechanics of the segregation of solute atoms in solid solution, such as of carbon and nitrogen in iron. 5. The conditions under which strain hardening is not removed by recovery or by recrystallization, and hence under which a mechanical equation of state exists, i.e., under which a relation exists between strain rate, strain, stress, and temperature. 6. Variation of the heat of activation for plastic strain rate upon stress and upon the microstructure. 7. Anisotropy introduced by deformation.

ISSN:0021-8979    

DOI:10.1063/1.1707696

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

In this report a review is made of the possible types of future research which might lead to an understanding of the fracture of metals, and hence to an increase of the strength level to which metals may be raised without danger of fracture. It is found that an understanding of fracture would be enhanced by research upon the following topics: 1. The effects of the following variables on the virtual fracture stress: (a) Strain; (b) strain rate; (c) temperature; (d) stress distribution; (e) structure; (f) mechanical history (i.e., fatigue). 2. A comparison of the fracture characteristics of metallic crystals with those of non‐metallic crystals, such as rocksalt. 3. The hindrances of plastic deformation by sharp stress gradients. 4. The introduction of stress concentration by: (a) Non‐metallic inclusions; (b) precipitates; (c) slip bands; (d) twin bands; (e) grain boundary deformation. 5. The effect of reversal of stresses upon the properties of slip bands.

ISSN:0021-8979    

DOI:10.1063/1.1707697

出版商:AIP    

年代:1946

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707698

出版商:AIP    

年代:1946

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707690

出版商:AIP    

年代:1946

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707692

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

The exact mathematical treatment of non‐linear mixers of the type used in very‐high frequency and ultra‐high frequency superheterodynes is difficult. If, however, the non‐linear element is simplified to the extent that it is fully described by a plotted current‐voltage characteristic, several ways of determining the output become evident. Some of the most fundamental methods are described in the following, and their shortcomings pointed out. The methods are then tried out on a ``guinea pig'' characteristic and the results critically compared with respect to accuracy, amount of labor, required mathematical tools, and other factors. It is found that no ``best'' method exists and that all methods require simplifying assumptions and approximations that frequently lead the converter designer to consider practical measurements, or special methods, such as the one provided by the frequency conversion diagram technique.

ISSN:0021-8979    

DOI:10.1063/1.1707693

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

A method is described for supporting airborne particles upon thin glass fibers where they build up in chains and may be examined in the electron microscope. With no supporting membrane, the contrast and resolution are increased in the micrographs. The specimens are particularly useful for stereoscopic studies. A special reference is made to the study of carbon particles mounted in this fashion. The carbons examined are formed by pyrolysis of acetylene and occur naturally in pronounced chains. Reproducible particle size data for the carbons can be secured by measurements made on individual particles at ×200,000. Evidence for the crystalline nature of this carbon is rendered visible in the micrographs.

ISSN:0021-8979    

DOI:10.1063/1.1707694

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

The application of electron diffraction reflection methods and the electron microscope to investigations of metallurgical structures is reported. It is shown that these instruments can yield valuable information concerning very small amounts of secondary phases and impurities in metals. Thus, for example, when martensite decomposes at 200°C, the slow etching component is highly dispersed Fe3N. The decomposition at 400°C yields the usual Fe3C. Further, the Fe3N formed at 200°C transforms to Fe3C when annealed at 350°C. Other examples are presented. The successful application of these instruments is dependent upon the production of clean, etched surfaces. Surface preparation is discussed and a satisfactory technique for rinsing etched surfaces is described. In some alloy systems, the etching reaction may result in the redeposition of a component onto the etched surface. In the case of a &bgr;‐brass containing 0.0005–0.001 percent silver, the silver is deposited in the form of spherical particles about 1000A in diameter. Aluminum alloys appear to offer a serious problem in discovering satisfactory etchants due to the position of aluminum in the electromotive series relative to copper, silver, etc.

ISSN:0021-8979    

DOI:10.1063/1.1707695

出版商:AIP    

年代:1946

数据来源: AIP