摘要:

A positive‐replica technique for electron microscopy has been developed, which reproduces the contour variations of the specimen surface, and permits direct visual interpretation of elevation. The method utilizes two resins, each mutually insoluble in the solvent for the other, specifically, polyvinyl alcohol plus Formvar. Shadow casting of the Formvar positive replica enhances detail and highlights the areas in relief in the original surface. Examples are given, in particular, applied to wear‐test specimens.

ISSN:0021-8979    

DOI:10.1063/1.1698333

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A phenomenological law of optical birefringence, induced by small strain in viscoelastic materials, is formulated and applied to an idealized medium. The resulting optical‐stress‐strain‐time‐temperature relations are used in finding conditions under which models made of viscoelastic materials may be employed in the photoelastic method of solving boundary value problems in the linear theory of elasticity.

ISSN:0021-8979    

DOI:10.1063/1.1698334

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The friction on a surface moving through air at high speed has been measured over a pressure range from 0.5 to 200 microns. A rotating cylinder type apparatus was used in which the inner cylinder was rotated at very high speed by means of an air turbine arrangement similar to that used in an air driven vacuum type ultracentrifuge. The outer cylinder completely surrounded the inner cylinder and was supported coaxially with it by means of a torsion fiber so that the frictional torque on the rotating cylinder could be measured with precision. Observations were made at rotor speeds varying from 400 r.p.s. to 1700 r.p.s. which corresponds to a linear velocity at the periphery of the rotor varying from 400 to 1700 ft./sec. It was found that at all pressures the observed torque varied in an essentially linear fashion with the rotor speed. The relationship between torque and pressure at constant speed yielded a smooth curve indicative of ordinary viscosity, and this general form held for all speeds tested. However, the results could be explained by kinetic theory treatment of viscosity only at pressures lower than 10 microns; i.e., below the point where the intermolecular collision frequency predominates over that of the collisions between the molecules and the walls.

ISSN:0021-8979    

DOI:10.1063/1.1698335

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698337

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698338

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698339

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698341

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698343

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698344

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698345

出版商:AIP    

年代:1949

数据来源: AIP