摘要:

An attempt is made to go beyond an idealized description of the process of metal removal. The details of two‐dimensional orthogonal cutting are investigated, and several concepts and hypotheses are introduced which apply equally well to the most general cutting operation. Of these, the most significant is the great importance of the small time available for the plastic deformation to occur. Ekstein's paradox is explained, and the influences of speed of cutting, depth of cut, and rake angle are correlated by the consideration of dynamic plasticity. In addition, the effect of non‐homogeneity of the material is analyzed and shown to account for the gradual change from the discontinuous to the continuous type of chip as the cutting speed is increased, and for the marked increase in the specific cutting force as the depth of cut is decreased. A partial theoretical analysis of the state of stress, in the chip and the workpiece, and energy considerations are also found helpful in the description of what probably happens when metal is cut.

ISSN:0021-8979    

DOI:10.1063/1.1698265

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A new type of open‐wire line is described for which many disadvantages, notably radiation and unbalance, are overcome by replacing one of the physical conductors by the image of the other in a semi‐infinite, highly conducting plane.The characteristics of a line driven at both ends and loaded at the center are examined; it is shown that the impedances measured on both sides of such a line are equal and simply related to the load impedance, provided that electrical symmetry is maintained about the load point. The double‐ended drive requires no dielectric supports and permits the line conductor to continue past the load.The construction and operation of an image line with double‐ended drive is described. The characteristics of the new line compare very favorably with those of a good coaxial measuring line.Finally, use of the line in the measurement of the apparent impedance of a cylindrical dipole antenna as a function of the line spacing is described.

ISSN:0021-8979    

DOI:10.1063/1.1698266

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Small‐scale experiments have been carried out for determining the minimum vertical thermal gradient which is required to cause convection in liquids entrapped in porous media. Observations relative to the onset of convective flow in unconsolidated sands indicate that the present theories predict minimum gradients which are excessive by considerable amounts, possibly because they neglect the temperature‐dependence of viscosity. The ratio of theoretical to observed gradients is found to be roughlyR=(Kh2&mgr;AV/k&rgr;&agr;)0.51,whereh2is the thermal diffusivity, &mgr;Avis average viscosity,kis flow‐permeability, &rgr; is density of liquid, &agr; is the coefficient of cubical expansion of the liquid, and whereK= 10−3sec.2per cm2°C for c.g.s. units. By extrapolation, it is possible to strengthen the earlier conclusion that convection occurs in the Woodbine sand near the Mexia fault zone.

ISSN:0021-8979    

DOI:10.1063/1.1698267

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A new reflection method is described for determining pole figures of flat samples with a Geiger counter x‐ray spectrometer. The chief advantage of the method is that the experimental data may be used directly without corrections for changes in geometry during rotation of the sample. Beginning from an initial position identical with the usual reflection arrangement the sample is rotated about an axis defined by the intersection of the sample surface with the plane of the spectrometer. During this motion a randomly oriented sample of sufficient thickness will yield a constant counting rate because the absorption and effective scattering volume of the sample remain unchanged. As a result, no correction formula is required. The experimental arrangement requires three horizontal slits; two are used to collimate the incident beam, and the third is placed in front of the counter. A mathematical analysis of the optical elements of the arrangement is given together with the results from a practical application.

ISSN:0021-8979    

DOI:10.1063/1.1698268

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A method employing a diverging x‐ray beam is described for the determination of preferred orientation in flat transmission samples with a Geiger counter x‐ray spectrometer. It is shown that for a certain range of sample thickness the counting rate is independent of the rotation of the samples, and therefore, no correction formula is required.

ISSN:0021-8979    

DOI:10.1063/1.1698269

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

In calculating elastic constants of viscoelastic media from transverse wave propagation, it has been customary heretofore to assume a plane disturbance in a medium of infinite extent. Equations have now been derived for conditions which approach much more closely the experimental arrangement, namely, propagation from a finite source plate in a rectangular cell, and representative numerical calculations have been made. The new theory shows that the finite dimensions of cell and source should have very little influence on the wave‐length as determined from observations of strain double refraction, but the attenuation should be perceptibly different from that of the plane wave case. Experimental data confirm these conclusions. Nevertheless, the simple plane theory is adequate within present experimental error for the majority of cases. Only in certain specified ranges of mechanical consistency will it be necessary to apply corrections taking into account the sizes of the cell and source.

ISSN:0021-8979    

DOI:10.1063/1.1698270

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

An investigation has been carried out on the mechanism of sintering of metallic particles. Single layers of spherical copper particles have been sintered under varying conditions of time and temperature in a dry hydrogen atmosphere. Analysis of the rate of interface contact between the particles has shown metallic sintering to be a diffusion process, in agreement with the theory of Kuczynski. The heat of activation of self‐diffusion of copper has been calculated and found to be 55,000 cal./mole. This is in close agreement with Kuczynski and also values obtained by other workers using the radioactive tracer method.

ISSN:0021-8979    

DOI:10.1063/1.1698271

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The Duffing equationx¨+&agr;x+&bgr;x3=Fcos&ohgr;t(&agr;>0) is known to possess periodic solutions with frequency &ohgr;/nfor all integraln, provided that &bgr; is sufficiently small. Forn=1 and n≠1, these solutions are designated in the literature as harmonic and subharmonic solutions respectively. In this paper, a classification of the various types of periodic solutions is given, in which it is shown that there are two types of harmonic solutions and two types of subharmonic solutions for sufficiently small &bgr;. The perturbation method is employed to find the approximate response curves for each of the four types of periodic solutions. A comparison is made between the response curves obtained in the non‐linear case (&bgr;≠0) and linear case (&bgr;=0) and some properties of the solutions in the non‐linear case are discussed. A comparison is then made between the perturbation method and the Rauscher method, which is an iteration method that assumesFsmall instead of &bgr;. This comparison is not made in all generality, but only for one particular type of subharmonic solution. The main result obtained is that forFsmall, the two methods yield similar results for larger values of &bgr; than might have been anticipated.

ISSN:0021-8979    

DOI:10.1063/1.1698272

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

It is shown that then‐power law describing a true stress‐strain curve, normally written asS=k&dgr;n, can be placed in the formS=S0(e&dgr;/n)nwhereS0is the engineering tensile strength. The application of this new expression to tensile curves is discussed.A plot ofS/S0as a function ofn, for a fixed value of the logarithmic strain &dgr;, provides a general description of the behavior of all materials in plastic deformation. Experimental data from the literature are in good agreement with the curves.

ISSN:0021-8979    

DOI:10.1063/1.1698273

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The nature of grease as a dispersion of solid particles in oil is briefly discussed, and the value of the electron microscope in studying this solid phase is pointed out. The requirements of a satisfactory grease specimen mounting technique are outlined and a new technique fulfilling these requirements is described. Electron micrographs are presented which demonstrate the usefulness of the technique in disclosing pertinent information on grease structure. The factors involved in the preparation of powder specimens for electron micrography are discussed in relation to the adoption of a modification of the grease mounting technique for this purpose. The modified technique for powders is outlined and illustrated with micrographs.

ISSN:0021-8979    

DOI:10.1063/1.1698274

出版商:AIP    

年代:1949

数据来源: AIP