Table No. 22. The Transverse Strength Of Cast-Iron Test-Bars Loaded At The Centre, On Supports 36 Inches Apart
Description
This section is from the book "Notes On Construction In Mild Steel", by Henry Fidler. Also available from Amazon: Notes On Construction In Mild Steel.
Table No. 22. The Transverse Strength Of Cast-Iron Test-Bars Loaded At The Centre, On Supports 36 Inches Apart
Nominal size of bar, 2 inches deep x 1 inch wide.
No. of Test. | Actual dimensions of test-bar as cast. Inches. | Actual breaking load at centre. Pounds. | Deflection at fracture. Inches. | Equivalent breaking load of 2" X 1" bar calculated in the proportion of BD2 Pounds. | |
Depth. | Breadth. | ||||
1 | 2.06 | 1.06 | 3046 | 0.33 | 2715 |
2 | 2.08 | 1.07 | 2934 | 0.30 | 25401 |
3 | 2.11 | 1.05 | 3203 | 0.30 | 27441 |
4 | 2.06 | 1.07 | 4278 | 0.35 | 3770 |
1 Flaw on underside.
No. of Test. | Actual dimensions of test-bar as cast. Inches. | Actual breaking load at centre. Pounds. | Deflection at fracture. Inches. | Equivalent breaking load of 2" x 1" bar calculated in the proportion of BD2. pounds. | |
Depth. | Breadth. | ||||
5 | 2.06 | 1.06 | 3875 | 0.30 | 3452 |
6 | 2.1 | 11 | 2329 | 0.25 | 19211 |
7 | 2.06 | 1.07 | 5734 | 0.55 | 50402 |
8 | 2.04 | 1.02 | 4726 | 0.40 | 4457 |
9 | 207. | 1.09 | 4300 | 0.50 | 3683 |
10 | 2.07 | 1.10 | 3472 | 0.28 | 29471 |
11 | 2.06 | 1.08 | 3516 | 0.30 | 30691 |
12 | 2.08 | 1.06 | 5465 | 0.50 | 4768 |
13 | 2.07 | 1.07 | 2822 | 0.15 | 24621 |
14 | 2.06 | 1.08 | 4009 | 0.35 | 3500 |
15 | 2.07 | 1.06 | 4054 | 0.33 | 3500 |
16 | 2.05 | 1.06 | 3584 | 0.30 | 3218 |
17 | 2.10 | 1.07 | 4278 | 0.35 | 3626 |
18 | 2.00 | 1.00 | 3940 | 0.41 | 3940 |
19 | 2.00 | 1.00 | 3800 | 0.44 | 3800 |
20 | 2.00 | 1.00 | 3780 | 0.41 | 3780 |
21 | 2.00 | 1.00 | 3830 | 0.38 | 3830 |
22 | 2.00 | 1.00 | 4490 | 0.44 | 4490 |
23 | 2.00 | 1.00 | 4320 | 0.39 | 4320 |
24 | 2.01 | 1.06 | 3113 | 0.45 | 2909 |
25 | 2.02 | 1.00 | 3875 | 0.40 | 3800 |
26 | 2.00 | 1.00 | 3300 | 0.41 | 3300 |
27 | 2.00 | 1.00 | 3390 | 0.41 | 3390 |
28 | 2.00 | 1.00 | 3290 | 0.41 | 3290 |
29 | 2.00 | 1.00 | 3150 | 0.38 | 3150 |
30 | 2.00 | 1.00 | 3140 | 0.37 | 3140 |
31 | 2.00 | 1.00 | 3160 | 0.38 | 3160 |
32 | 2.00 | 1.00 | 4010 | 0.47 | 4010 |
33 | 2.00 | 1.00 | 3820 | 0.42 | 3820 |
34 | 2.00 | 1.00 | 3390 | 0.43 | 3390 |
35 | 2.00 | 1.00 | 3550 | 0.46 | 3550 |
36 | 2.00 | 1.00 | 3360 | 0.45 | 3360 |
37 | 2.00 | 1.00 | 3820 | 0.42 | 3820 |
38 | 2.00 | 1.00 | 3640 | 0.41 | 3640 |
39 | 2.00 | 1.00 | 3710 | 0.42 | 3710 |
40 | 2.00 | 1.03 | 4050 | 0.43 | 3927 |
41 | 2.00 | 1.00 | 4210 | 0.49 | 4210 |
42 | 2.00 | 1.03 | 3490 | 0.40 | 3384 |
43 | 2.00 | 1.00 | 3610 | 0.43 | 3610 |
44 | 2.00 | 1.00 | 3780 | 0.41 | 3780 |
45 | 2.00 | 1.00 | 3710 | 0.45 | 3710 |
46 | 2.00 | 1.00 | 3674 | 0.43 | 3674 |
47 | 2.00 | 1.00 | 3150 | 0.35 | 3150 |
48 | 2.00 | 1.00 | 3000 | 0.29 | 3000 |
1 Flaw on underside.
2 Flaw on upper half.
No. of Test. | Actual dimensions of test-bar as cast. Inches. | Actual breaking load at centre. Pounds. | Deflection at fracture. Inches. | Equivalent breaking load of 2" X 1" bar calculated in the proportion of BD2. Pounds. | |
Depth. | Breadth. | ||||
49 | 2.00 | 1.00 | 3350 | 0.40 | 3350 |
50 | 2.00 | 1.00 | 3100 | 0.30 | 3100 |
51 | 2.12 | 1.07 | 4233 | 0.35 | 3519 |
52 | 2.06 | 1.09 | 3785 | 0.30 | 3274 |
53 | 2.11 | 1.05 | 3248 | 0.25 | 27811 |
54 | 2.07 | 1.07 | 4278 | 0.35 | 3736 |
55 | 206 | 1.07 | 4188 | 0.32 | 3690 |
56 | 2.12 | 1.08 | 4435 | 0.40. | 3654 |
57 | 2.00 | 1.00 | 3303 | 0.28 | 3303 |
58 | 2.00 | 1.00 | 3472 | 0.30 | 3472 |
59 | 2.00 | 1.00 | 3610 | 0.33 | 3610 |
60 | 2.00 | 1.00 | 3582 | 0.36 | 3582 |
61 | 2.00 | 1.00 | 3580 | 0.415 | 3580 |
62 | 2.00 | 1.00 | 3990 | 0.454 | 3990 |
63 | 2.00 | 1.00 | 3200 | 0.390 | 3200 |
64 | 2.00 | 1.00 | 3530 | 0.416 | 3530 |
65 | 2.00 | 1.00 | 3889 | 0.455 | 3889 |
66 | 2.00 | 1.00 | 3950 | 0.450 | 3950 |
67 | 2.00 | 1.00 | 3580 | 0.437 | 3580 |
68 | 2.00 | 1.00 | 3750 | 0.455 | 3750 |
69 | 2.00 | 1.00 | 3640 | 0.437 | 3640 |
70 | 2.00 | 1.00 | 3528 | 0.375 | 3528 |
71 | 2.00 | 1.00 | 3696 | 0.437 | 3371 |
72 | 2.00 | 1.00 | 4032 | 0.437 | 3371 |
73 | 2.00 | 1.00 | 4032 | 0.437 | 3371 |
74 | 2.00 | 1.00 | 3360 | 0.437 | 3360 |
75 | 2.00 | 1.00 | 3528 | 0.375 | 3528 |
76 | 2.00 | 1.00 | 3808 | 0.437 | 3808 |
77 | 2.00 | 100 | 3584 | 0.375 | 3584 |
78 | 2.00 | 1.00 | 3528 | 0.375 | 3528 |
79 | 2.00 | 1.00 | 3360 | 0.437 | 3360 |
80 | 2.00 | 1.00 | 3416 | 0.375 | 3416 |
81 | 2.00 | 1.00 | 3584 | 0.437 | 3584 |
82 | 2.00 | 1.00 | 3304 | 0.375 | 3304 |
83 | 2.00 | 1.00 | 3584 | 0.437 | 3584 |
84 | 2.00 | 1.00 | 3360 | 0.375 | 3360 |
85 | 2.00 | 100 | 3426 | 0.437 | 3426 |
86 | 2.00 | 1.00 | 3696 | 0.375 | 3696 |
87 | 2.00 | 1.00 | 3864 | 0.375 | 3438 |
88 | 2.00 | 1.00 | 3528 | 0.375 | 3528 |
89 | 2.00 | 1.00 | 3584 | 0.375 | 3584 |
90 | 2.00 | 1.00 | 3696 | 0.500 | 3472 |
91 | 2.00 | 1.00 | 3192 | 0.343 | 2902 |
92 | 2.00 | 1.00 | 3472 | 0.406 | 3270 2 |
1 Flaw on underside.
2 Retest of No. 91.
No. of Test. | Actual dimensions of test-bar as cast. Inches. | Actual breaking load at centre. Pounds. | Deflection at fracture. Inches. | Equivalent breaking load of 2" X 1" bar calculated in the proportion of BD2. Pounds. | |
Depth. | Breadth. | ||||
93 | 2.00 | 1.00 | 3304 | 0.375 | 3158 |
94 | 2.00 | 1.00 | 3248 | 0.406 | 3102 |
95 | 2.00 | 1.00 | 4144 | 0.500 | 4020 |
96 | 2.00 | 1.00 | 3472 | 0.437 | 3360 |
97 | 2.00 | 1.00 | 3584 | 0.375 | 3360 |
98 | 2.00 | 1.00 | 3360 | 0.406 | 3304 |
99 | 2.00 | 1.00 | 3584 | 0.437 | 3528 |
100 | 2.00 | 1.00 | 3584 | 0.437 | 3472 |
In tests Nos. 69 to 100 the dimensions of the test-bar are nominal only. In all cases the breaking load is reduced in the last column in the proportion of BD2.
It is not unusual to find specifications for cast-iron work which combine a specified ultimate resistance in direct tension with a specified transverse breaking load on a standard bar.
The discrepancy between the calculated fibre stress (using the ordinary formula) and the ultimate resistance in direct tension has been long known from the days of the earlier experimenters to the present time, and much has been written upon the subject, including the influence of the form of cross-section upon the ratio. The subject, which is one of great interest, and affects not only cast iron, but also the permissible working fibre stress in small wrought-iron and mild steel beams, cannot be further alluded to here, but the practical lesson to be drawn as regards the drawing up of specifications for the strength of cast iron appears to be, that where the ultimate transverse resistance is stipulated, it is wiser to avoid direct reference to the ultimate tensile resistance, or vice versa. Either standard of strength may be chosen, but not both, unless the purchaser is prepared to establish to his own satisfaction, and that of the contractor, the precise ratio which in any given bar should obtain between ultimate transverse resistance and ultimate tensile strength.
It is customary to find the test-bar as cast to vary fractionally both in breadth and depth from the nominal dimensions, and it therefore becomes necessary to allow for the variation in the observed breaking load, and to reduce to a common standard in the proportion of breadth X depth2. This has been done in the foregoing table, and the mean value of the breaking load at the centre of a bar 2 inches deep by 1 inch wide, on supports 36 inches apart, is found to be from the above experiments (omitting those with flaws on the underside) 3568 lbs., and the mean deflection at the centre, 0.394 inch.
The test-bar may also be found to vary from a true rectangular shape, being thicker at top than at bottom, and the way in which such a bar is placed in the testing machine should be observed,
Numerous published chemical analyses of cast iron will be found in the literature of this subject, but the following analysis of a test-bar of the dimensions given in the foregoing table will serve to afford the student a fair idea of the chemical differences between cast iron and cast steel.
The analysis presents no very marked difference from the normal composition of cast iron, save that the proportions of manganese and phosphorus are somewhat high.
Chemical Analysis Of Cast-Iron Test-Bar
Per cent. | |
Graphite | 2.215 |
Combined carbon ... | 1.802 |
Silicon | 2.028 |
Sulphur | 0.101 |
Phosphorus | 1.192 |
Manganese | 0.965 |
Iron (by difference) | 91.697 |
100.000 |
The test-bar from which the analysis was taken gave a breaking weight of 28 cwt. at centre of standard bar (2" X 1" at 36" span) with ⅜ inch deflection.
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