MTS Series 609 Alignment Fixture - Manual (Page 46)

Series 609 Alignment Fixture Product Information 46
Calculating Bending Strain—Notched Round Thin
Specimen Preparation
1. Calculate the average axial strain for each level.
Use this formula to find the average axial strain (A):
Where: ε
1
through ε
6
are the strain readings from gages 1 through 6
Au is the average strain of the upper gages
Al is the average strain of the lower gages
2. Calculate the bending strain for each axis and each level.
Use these formulas to determine the bending strain (B):
Where: ε
1
through ε
6
are the strain readings from gages 1 through 6
bu is the bending strain of the upper gages
bl is the bending strain of the lower gages
subscript
0
is the bending strain of the 0° axis
subscript
120
is the bending strain of the 120° axis
subscript
240
is the bending strain of the 240° axis
3. Determine the tensile direction for each level.
Determine the two most positive (tensile) results for each level from Step 2.
• Call the largest b
1
.
• Call the second largest b
2
.
4. Calculate the direction of the maximum strain for each level.
Use this formula to find the direction ( φ) of the maximum (most tensile)
bending strain:
Au
ε
1
ε
2
ε
3
+ +
3
---------------------------- = Am
ε
4
ε
5
ε
6
+ +
3
---------------------------- =
Upper Gages Lower Gages
bu
0 °
ε
1
A – =
bu
120 °
ε
2
A – =
bu
240 °
ε
3
A – =
bm
0 °
ε
4
A – =
bm
120 °
ε
5
A – =
bm
240 °
ε
6
A – =
Upper Gages Lower Gages
φ arc
bu
1
bu
2
-------- 0.5 +
0.866
----------------------- tan = φ arc
bl
1
bl
2
------- 0.5 +
0.866
--------------------- tan =
Upper Gages Lower Gages