It has already been stated that the strength and elasticity of wrought iron depend not only upon its quality, but upon the treatment to which it has been subjected in working, and upon other surrounding circumstances.
The following Table shows concisely the effect produced by different modes of working, by changes of temperature, etc.
The conclusions given are founded upon a large number of experiments by Mr. Kirkaldy and others. Those by Mr. Kirkaldy are clearly classified in Mr. Kinnear Clarke's Hides and Tables for Mechanical Engineers.
Turning or removing skin..
No alteration .
Reduced from between
4.1 and 43.8 per cent
Stress suddenly applied ...
Reduced 18.5 per cent
Reduced in nearly all cases.
Cold rolling - plates..
Increased 50 per cent
Reduced 60 per cent.
Effect of frost 23° F...
Reduced 2.3 per cent
Reduced 8 per cent.
Effect of frost, stress suddenly applied
Reduced 3.6 per cent
Reduced between 0 and 30 per cent.
Sir William Fairbairn found that the strength of wrought iron was practically the same at all temperatures between 0. and 400° Fahr.6
1 Kennedy, Iron, 11th May 1883. 2 Institute Mechanical Engineers, 4th August 1885. 3 Architect, 18th February 1882. 4 Stoney. 5 Downing.
6 Useful Information for Engineers, Series ii.