Overstrain  and  Recovery  of  Aluminium,  etc. 
389 
the  extensometer-reading  taken,  and  the  pull  almost  entirely 
removed  again,  the  total  time  of  application  being  under  10 
seconds.     The  results  of  tests  of  this  kind,  before  and  after 
Table  VIII. 
Load  3  tons.     Before  overstrain. 
Table  IX. 
Load  3  tons.     After  overstrain. 
Eeading  of 
Time  in 
Extensometer  in 
Minutes. 
— r—  inch,  units. 
50,000 
0 
414 
5 
424 
10 
429 
22 
433 
47 
438 
72 
440 
157 
445 
Time  in 
Minutes. 
0 
5 
10 
17 
25 
30 
35 
41 
164 
Eeading  of 
Extensometer  in 
l 
50,000 
inch  units. 
420 
433 
438 
441 
445 
447 
449 
450 
469 
Table  X. 
Load  5'5  tons.     Before  overstrain. 
Table  XI. 
Load  5-5  tons.    After  overstrain. 
Time  in 
Minutes. 
Reading  of 
Extensometer  in 
50J0O   iaCh  UnltS- 
0 
596 
7 
610 
15 
618 
21 
622 
30 
629 
35 
631 
48 
637 
68 
644 
139 
662 
188 
671 
203 
673 
Time  in 
Minutes. 
Reading  of 
Extensometer  in 
50^00   in°h  UnltS- 
? 
5 
10 
15 
22 
32 
37 
52 
167 
197 
230 
626 
639 
653 
662 
669 
675 
682 
686 
694 
731 
738 
743 
overstrain,  are  shown  in  Table  XII.  and  are  plotted  in  fig.  8. 
For  convenience  in  setting  the  load  without  loosening  the 
wedge  grips  which  hold  the  specimen,  the  load  was  reduced 
to  0*1  ton  instead  of  zero.  The  curve  A  represents  the 
material  before  overstrain  and  the  condition  immediately  after 
an  overstraining  load  of  11  tons  is  shown  by  curve  B.  In  these 
tests  the  permanent  set  (or  rather  extension,  which  does  not 
disappear  in  10  minutes  from  the  removal  of  the  load)  begins 
