SUMMARY OF RESULTS OF THE A. P. A. SERIES OF TESTS.
A peculiarity between transverse and tensile tests
which the A. F. A. series of tests displays, lies in an increase of transverse strength per square inch, and a decrease of tensile strength, in opposite directions, according as areas of cross sections are enlarged. For illustration, take the unfinished bar, test No. 2, Table 115, page 558, which is 1.20 diameter, giving an area of 1.13 inches, and compare its strength per square inch in an approximate way with test No. 8, which has an area of 16.90 inches, and we find that the larger body has 52.7 per cent, greater strength per square inch of cross section or area than the smaller body. In the case of tensile tests, we find, by an examination of Table 126, opposite page, that an average of all the 1.14 diameter unfinished bars gave 57,250 pounds greater strength per approximate square inch than an average of the 2.27 diameter unfinished bars. Were the bars larger than 2.27 diameter, we would find the same principle to hold good.
The results show that in the construction of machinery, etc., we may expect greater strength per square inch in transverse strains and less in tensile, as areas of cross sections are enlarged, and further demonstrate that cast iron castings are best constructed to stand transverse strains. Why it is that the reverse of results should be obtained between transverse and tensile tests as shown is largely due to the principle "in union there is strength," being applicable to transverse and not to tensile strains.he above analyses of Table 127 were determined from drillings obtained from i" square dry sand bars, taken from the respective casts.gth per square inch and table 127 gives the analyses, both of which are fully explained on page 555.SlolrlciiKc .i! : •,» l'fjii]-.y!v,iu;.i M.ii!« ,«!.'.. <•*'•, t«.Mii«! i v, I'it l:,l.ui>;, P,i,ll. The chilland j^reen sand showedast on end, us such will tfive truer results than the [J4™inch round bar in general practice, especially in making comparison <>i; the widest ranges in grades.temper '' or damp- ,| |