This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1891 Excerpt: ...up to between 280 to 330 and then fall. For the "Union" material (III) the minimum value of $„ is attained only at 300, and the curve afterwards rises, a maximum occurring at 400. Similar differences are also to be observed in the character of the curves for 8t. The following Table, compiled from the mean observed values, gives the ratios in per cent. of 8, to 3, for various temperatures:--In Fig. 8 the stress diagrams for material of quality II are reproduced. The limit of stretch, in each diagram, is denoted by Stress Diagrams For Quality II And Temperatures--20 To 600. S, the point of maximum stress by B, the point of fracture by Z. At 400 the material has assumed the character of the soft metals, zinc for instance. The irregularities at the points a and b occurred when the flow extended to the shoulders of the test-piece, beyond the actual test-length. The variations in the contraction of area are extraordinarily great. For all three qualities of material the smallest value of q, the reduction of area, occurs at 300. The stress at the limit of proportionality increases with rising temperature between--20 and-4-20, reaching a maximum about + 20, it then falls slightly to 100, and at 200 attains a second higher maximum, subsequently falling rapidly. The elongation at the limit of proportionality 8, is subject to no appreciable alterations. For the stresses usual at ordinary temperatures the engineer may therefore reckon, in steel heated even up to 200, on elongations proportional to the load and on sufficient safety. It would, however, scarcely be safe to draw conclusions from the results of these experiments as to the admissible working stress for temperatures over 200, or for frequent changes of temperature ranging from 150 to 3503. Reli...