MTS Series 609 Alignment Fixture - Manual (Page 36)

Series 609 Alignment Fixture Product Information 36
Calculating Bending Strain—Round Thin Diameter
Specimen Preparation
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:
Where:
( φ) is measured from the highest reading (most tensile) strain
gage toward the second highest reading strain gage
b
1
is the highest strain reading of a given level
b
2
is the second highest reading of a given level
The bending strain directions for all levels should generally agree if you
have satisfactorily removed the “S” bend.
5. Calculate the maximum bending strain for each level.
Use this formula to find the maximum bending strain (B) at this gage level:
Where:
Bu is the bending strain of the upper gages
Bm is the bending strain of the middle gages
Bl is the bending strain of the lower gages
b
1
is the highest strain reading of a given level
6. Calculate the percent bending strain for each level.
Use this formula to find the percent bending strain (PBS):
Where:
Bu is the bending strain of the upper gages
Bm is the bending strain of the middle gages
Bl is the bending strain of the lower gages
Au is the average strain of the upper gages
Am is the average strain of the middle gages
Al is the average strain of the lower gages
φ arc
bu
2
bu
1
-------- 0.5 +
0.866
----------------------- tan = φ arc
bm
2
bm
1
---------- 0.5 +
0.866
------------------------ tan = φ arc
bl
2
bl
1
------- 0.5 +
0.866
--------------------- tan =
Upper Gages Middle Gages Lower Gages
Bu
b
1
θ cos
------------ =
Bm
b
1
θ cos
------------ = Bl
b
1
θ cos
------------ =
Upper Gages Middle Gages Lower Gages
PBS
Bu
Au
------- 100 × = PBS
Bm
Am
-------- 100 × = PBS
Bl
Al
----- 100 × =
Upper Gages Middle Gages Lower Gages