Methods for determination of the mass of warp and weft per unit area of fabric

Abstract These experiments indicate that softeners can influence abrasion resistance, as measured by laboratory machines, in some manner other than by altering the stress-strain properties of the rubber. One possible explanation is that the softener acts as a lubricant to the abrasive surface. Since this surface, in laboratory abrasion-testing machines, is relatively small, and comes repeatedly into contact with the rubber under test, it seems possible that it may become coated with a thin layer of softener that reduces its abrasive power. It would be interesting in this connection to try an abrasive machine in which a long continuous strip of abrasive material was used, no part of it being used more than once, so as to eliminate or minimize this lubricating effect. The fact that the effect of the softener is more pronounced on the du Pont than on the Akron-Croydon machine lends support to the lubrication hypothesis, because on the former machine the rate of wear per unit area of abrasive is much greater. Thus in the present tests the volume of rubber abraded per hr. per sq. cm. of abrasive surface ranges from 0.03 to 0.11 cc. on the du Pont machine and from 0.0035 to 0.0045 cc. on the Akron-Croydon machine. On the other hand, if the softener acts as a lubricant, it would be expected to reduce considerably the friction between the abrasive and the rubber and hence the energy used in dragging the rubber over the abrasive surface. The energy figures given in the right-hand columns of Tables 1 and 3, however, show that there is relatively little variation between the different rubbers. As a test of the lubrication hypothesis, it would be of interest to vary the conditions of test so that approximately the same amount of rubber per unit area of abrasive is abraded in a given time on both machines; this should show whether the phenomena observed under the present test conditions are due solely to the difference in rate of wear or to an inherent difference in the type of wear on the two machines. This could most conveniently be done by considerably reducing the load on the du Pont machine. In the original work on this machine the load was standardized at 8 pounds, but no figures are quoted to show how abrasion loss varies with the load. As an addition to the present investigation, it is proposed to examine the effect of this variation with special reference to rubbers containing various amounts and types of softener. Published data on the influence of softeners on the road wear of tire rubbers do not indicate anything like such large effects as are shown by the du Pont machine. This throws some doubt on the value of this machine for testing tire tread rubbers, a conclusion which is confirmed by information obtained from other workers.

Download Full-text

IX. The thermal emissivity of thin wires in air

Philosophical Transactions of the Royal Society of London. (A.) ◽

10.1098/rsta.1892.0009 ◽

1892 ◽

Vol 183 ◽

pp. 371-405 ◽

Cited By ~ 8

Keyword(s):

Unit Area ◽

Large Change ◽

Horizontal Cylinder ◽

The Body ◽

Excess Temperature ◽

Thermal Emissivity ◽

Thin Wires ◽

Valuable Book ◽

The Wire

In 1884 it was observed experimentally that whereas the electric current required to maintain a thick wire of given material, under given conditions, at a given temperature, was roughly proportional to the diameter of the wire raised to the power three-halves, the current was more nearly proportional to the first power of the diameter if the wire were thin . When this difference in the behaviour of a thick and a thin wire was first noticed it was regarded as quite unexpected. But, as pointed out by one of us in the course of a discussion at a meeting of the Royal Society, the unexpected character of the result was due to people having assumed that the loss of heat from radiation and convection per square centimetre of surface per 1° excess temperature was a constant for a given kind of surface and independent of the size and shape of the cooling body, although as early as 1868 Box had drawn attention to the great difference that existed between the rate of loss of heat from unit area of a horizontal cylinder and per unit area of a sphere. The interchange of heat between unit area of a body and the enclosure might be independent of the shape of the body as far as radiation alone was concerned, but it seemed nearly obvious that the cooling by convection must be materially affected by the shape of the cooling body. The very valuable investigations that have been made on emissivity by Mr. Macfarlane, Professor Tait, Mr. Crookes, Mr. J. T. Bottomley, and by Mr. Schleiermacher, had for their object the determination of the variation of the emissivity with changes of the surface and with change in the density of the gas surrounding the cooling body, but it was not part of these investigations to determine the change in the emissivity that is produced by change in the shape and size of the cooling body. Indeed, so little has been the attention devoted to the very large change that can be brought about in the value of the emissivity by simply changing the dimensions of the cooling body, that in Professor Everett’s very valuable book on Units and Physical Constants, the absolute results obtained by Mr. Macfarlane are given as the “results of experiments on the loss of heat from blackened and polished copper in air at atmosphere pressure,” and no reference is made either to the shape or to the size of the cooling body.

Download Full-text