THROW-TESTING- MACHINE FOE REVERSALS OF MEAN STRESS. 
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T1 ie method used was to plot all the results ol a set of tests and then draw a curve 
through the best results, that is, those giving the greatest number of reversals. 
These are indicated by the small circles in the diagram. To prevent confusion, points 
lying much below the curves are not shown. 
The results obtained by Wohler and Baker were plotted on the same scale as 
Diagram I., but on a much larger sheet. It was found that none of Baker’s and 
only three of Wohler’s results came on that part of the sheet included in Diagram II. 
The three points corresponding to Wohler’s figures will be found on tire diagram. 
The results chosen from Wohler’s experiments were those carried out on rotating 
bars (steel axles) made by Messrs. Vickers, Sons & Co. The tenacity of this material 
ranged from 26'3 to 2IF2 tons per square inch, and the percentage extension from 
15*8 to 19’5. The material experimented on by Baker was soft steel of tensile 
strength 26'8 to 28'6 tons, and percentage extension 28. 
The results of Wohler and Baker for their materials are 
given in the following 
tables :— 
Number of bar. 
Maximum stress. 
Minimum stress. 
Range of stress. 
Repetitions before 
fracture. 
Wohler’s. 
63 
16-3 
-16-3 
32-6 
51,240 
64 
15-3 
15 - 3 
30-6 
72,940 
65 
14-3 
14-3 
28-6 
205,800 
66 
13-4 
13-4 
26-8 
278,740 
67 
12-4 
12-4 
24-8 
564,900 
68 
FI-5 
11-5 
23-0 
3,275,860 
69 
10-5 
10-5 
21-0 
8,660,000 
(Not broken.) 
Baker’s. 
1 
16-1 
- 16M 
32-2 
40,510 
9 
16-1 
16-1 
32-2 
60,200 
o 
15*2 
F5 • 2 
30-4 
68,400 
4 
15-2 
15-2 
30-4 
92,070 
5 
15 -2 
15-2 
30-4 
107,415 
6 
15-2 
15-2 
30-4 
128,650 
7 
15-2 
15-2 
30-4 
155,295 
8 
11-6 
11-6 
23-2 
14,876,432 
The materials used by Wohler and Baker in their tests given above, do not 
correspond very well with that used in the tests carried out by the author, but they 
are, however, the only results which could be reasonably, used for the purposes of 
comparison. 
It appears from Diagram 1. that the range ol' stress for a- definite number of 
reversals diminishes rapidly as the periodicity of the reversals increases. The 
