32
Molesworth’s pocket-book
Experiments on Steel for Ship-büilding.
(Naval Architects, 1878. B. Martell.)
1. Iron plates with butt straps and double chain riveting,
holes punched, linear tensile strain 17 • 9 tons, broke through
rivet holes.
2. Steel plates not annealed after punching, 16-I tons per
square inch, rivets sheered.
3. Same as 2, but with zigzag riveting, 19’2 tons.
4. Steel plates, same as 3, with steel rivets, 22-5 tons per
square inch; rivets shearing in some cases, plates breaking in
others.
5. Steel plates very thin suffer less from punching than
iron.
6 Difference in loss of strength by punching steel and iron
does not require special precautions up to i inch thick.
7. Above 5 inch thick the loss to iron varied from 20 to 23
per cent., and in steel from 22 to 33 per cent.
' 8. By annealing after punching the whole of the lost
strength was restored, and in some cases greater relative
strength was obtained than existed in the original plate.
(Dr. Siemens is of opinion that nothing is gained by annealing.)
9. The steel was only Injured a small distance round the
punched holes, and by riming from to J round the holes
the injured part was removed, *i<l no loss of strength was
observed any more than if the hole had been drilled. In
drilled plates no appreciable loss of tensile strength was
observed:—
Boiler plate .. .. 7-618 specific gravity.
Mild steel .. .. 7*820 „ „
Proportional Strength of “ Ship ” and “ Bridge ”
Steel, (Adamson.)
d.s
Mild Ship Steel
Bridge Steel .. |
J> e.
S3
ns
1
18| to 22|
35jto46j
•09
•420