METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS 123 
Table 11. — Speed of operation of testing machine 
Length of specimen 
Maximum 
cross-head 
speed 
Inches 
1.00 -. 
Inches per 
minute 
0.05 
3.00 or greater 
0.10 
I 
12. In making tests to determine the elastic limit in compression of metallic 
materials, the crosshead speed of the testing machine shall in no case exceed the 
allowable speed of head for the corresponding tension test of the material, as 
given in sections 18 and 19 of the tentative methods of tension testing of 
metallic materials (serial designation E 8-27 T) of the American Society for 
Testing Materials (15). (See p. 111.) 
Testing 
Balls with 
Retainer- 
T' 
■§> 
<-- 2 > < 2 
JL- 
Machine 
-Hardened Block 
I I 
hardened 
T 
-Icy 
> 
=n4- 
..... 7 
FIG. 61. — Compression tool 
THE DETERMINATION OF ELASTIC LIMIT, YIELD POINT, AND 
COMPRESSIVE STRENGTH 
13. (a) The term "elastic limit" in compression is defined the same as in 
tension, as follows : 
Elastic limit. — The greatest stress which a material is capable of developing 
without a permanent deformation remaining upon complete release of the 
stress. 
(b) The same general methods for determining elastic limit, as given in 
section 20 of the tentative methods of tension testing of metallic materials 
(serial designation, E 8-27 T, see p. Ill) of the American Society for Testing 
Materials (5) shall be used. For compression tests, method 2, or a still more 
precise method, seems generally suitable. 
