Humboldt H-2911 — H-2919 Compressometers / Extensometers - Manual (Page 4)

8 Remove the two spacer rods
9 Remove the three metal blocks from under the lower ring.
10 Zero the axial strain dial indicator with the stem close to the fully extended position.
Zeroing can be done (I) by rotating the dial face after loosening the lock screw on the
upper right hand side of the dial indicator or (2) by adjustment of the contact post
that fits into the lower lock ring.
11 Zero the diametrical strain dial indicator with its stem close to the fully pushed-in
position. (The stem is going to extend by the diametrical deformation of the
specimen). Zeroing of the dial can be done by rotating the dial face or by
adjusting the contact point.
Calculation
1 To Calculate the modulus of elasticity, to the nearest 50,000 psi (344.74 MPA)
as follows:
E = (S
2
- S
1
) / (
e
2
- 0.000050)Where:
E = chord modulus of elasticity, psi
S2 = stress corresponding to 40 percent of ultimate load or corresponding to
appropriate strain value from Table 1 (below), psi
SI = stress corresponding to a longitudinal strain, e
1
, of 50 millionths, psi
e
2
= longitudinal strain produced by stress S2.
2 To Calculate the poison's ratio, to the nearest 0.01 as follows:
m= (e
t2
- e
t2
) / (e
2
- 0.000050)
Where:
e
t2
= transverse strain at midheight of the specimen produced by stress S2.
e
t1
= transverse strain at midheight of the specimen produced by stress S1.
Unit Weight @ Time of Test Strain @ Age Indicated, Max. Millionths
lb/ft 3 CK/M 3 7 Days or More Less Than 7 Days
205 3280 and Over 300 200
165 to 204 2640 to 3264 375 250
135 to 164 2160 to 2624 450 300
115 to 134 1840 to 2144 525 350
105 to 114 1680 to 1824 600 400
95 to 104 1520 to 1664 675 450
85 to 94 1360 to 1504 750 500
75 to 84 1200 to 134 825 550
Table 1: Maximum Strain Values