1911-12.] The Elastic Strength of Flat Plates. 
383 
Dimensions such that Set begins almost from the first Application 
of Pressure. — Diagram 12 gives the deflection-pressure curve for a 
rectangular plate 8 in. by 6 in., '064 in. thick. The elastic straight line 
cannot be discerned with accuracy. It is not only short, but is involved 
with the zero error. 
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Summary of Results. 
The results of this research, for flat plates fixed at the edges and under 
uniform load on their areas, are : — 
1. The analytical formulae for stress, strain, and deflection in circular 
plates are correct. 
2. The elastic strength of the circular plate is determined by the 
maximum principal strain rather than the maximum principal stress. 
3. The formulae for deflection given by Grashof for rectangular and 
square plates are practically correct. 
4. In consideration of the practical results obtained for curvature, it 
would be well, in the case of rectangular and square plates, to multiply 
Grashof ’s formulae for maximum stress by 125. 
