369 
1911-12.] The Elastic Strength of Flat Plates. 
The Rectangular Plate. 
The following are the results for deflection for various size rectangular 
plates, for a pressure of 20 lbs. per sq. in. : — 
Rectangular 
plate. 
Thickness. 
Reference 
number. 
Deflection 
corrected for 
zero error. 
Theoretical 
deflection. 
8x4 
•0615 
16 
•026 
•02192 
8x4 
•061 
17 
•027 
•02247 
8x4 
•054 
18 
•033 
•03238 
7x4 
•0615 
19 
•023 
•02105 
7x4 
•061 
20 
•026 
•02158 
6x4 
•0605 
21 
•018 
•02043 
6x4 
•065 
22 
•020 
•01648 
5x4 
•061 
23 
•019 
•01693 
5x4 
•0615 
24 
•014 
•01652 
4x4 
•060 
14 
•015 
•01254 
4x4 
•0635 
15 
•013 
•01058 
The results for the five plates may be stated concisely as follows : — 
Rectangular 
plate. 
Average 
experimental 
deflection. 
Average 
theoretical 
deflection. 
8x4 
•0287 
•02559 
7x4 
•0245 
•02131 
6x4 
•019 
•01845 
5x4 
•0165 
•01672 
4x4 
•014 
•01156 
Grand average . 
•0205 
•01872 
It therefore appears that Grashof’s theoretical deflection formula for 
the rectangular plate is nearly correct. However, it seems to the author 
that, as the length of the long side increases, the formula gives a value 
rather too low. The difference is, however, too slight to be of any 
practical importance. 
Actual readings for set are given below. It is to be borne in mind 
that it is only the pressure at which set commences that is of any 
importance in the present investigation. 
Rectangular 
plate. 
Pressure. 
Set at centre. 
Thickness 
of plate. 
8x4 
20 
•0002 
•060 
25 
•0004 
8x4 
20 
•0001 
061 
5x4 
25 
•0001 
30 
•0002 
•060 
35 
*0005 
VOL. XXXII. 
24 
