Abstract
A microscope provided with a six-times micrometer eyepiece and objectives of 32 and 48 mm. focal length is suitable for measuring the cross-sectional dimensions of rubber test specimens. The width of specimens is usually greater than that of the die with which they were cut. The thickness of soft compounds as determined by the microscope is greater than that indicated by a gage of the plunger type. A MICROSCOPE of low power, equipped with a micrometer eyepiece, affords a convenient and practical means for accurately measuring the dimensions of rubber test specimens, and at the same time permits the inspection of specimens for defects. The equipment here described was designed particularly for measuring the width of the familiar dumb-bell shaped tensile test strips. At the present time no convenient and accurate gage is available for this purpose, and it is common practice to assume that the width of the specimen is the same as the die with which it was cut. The same equipment has been found satisfactory for determining the thickness of test strips, and is generally applicable for the measurement of dimensions up to about 6.4 mm. (0.25 inch). This use of the microscope embodies no original features. The method and equipment, however, are here described in some detail, since they may be of interest to investigators who may have occasion to make accurate mechanical measurements on rubber.
Performance Characteristics and Plasma Features of Low Power Hall Thrusters with Circular Cross-Sectional Discharge Chambers
