MTS Series 609 Alignment Fixture - Manual (Page 41)

Calculating Bending Strain—Flat Thin Specimens
Series 609 Alignment Fixture Product Information Specimen Preparation 41
Calculating Bending Strain—Flat Thin Specimens
This section shows how to calculate the bending strain for round specimens with
four gages at each level.
Gage Placement
1. Calculate the bending strains for each level.
Use these formulas to find the x axis (B
x
) and y axis (B
y
) bending strains of
each level:
Where: ε
1
through ε
12
are the strain readings from gages 1 through 12
w is the width of the specimen
d is the distance from the specimen edge to the middle of the gage
Bu
x
is the bending strain of the x axis of the upper gages
Bm
x
is the bending strain of the x axis of the middle gages
Bl
x
is the bending strain of the x axis of the lower gages
Bu
y
is the bending strain of the y axis of the upper gages
Bm
y
is the bending strain of the y axis of the middle gages
Bl
y
is the bending strain of the y axis of the lower gages
Do not ignore the sign of negative numbers.
2. Calculate the percent bending strain for each level.
Use this formula to find the percent bending strain (PBS):
Bu
x
1
4
--- ε
1
ε
2
ε
3
– ε
4
– + ( ) =
Bu
x
w
4
----
ε
1
ε
2
ε
3
– ε
4
– +
w 2d –
---------------------------------------
⎝ ⎠
⎛ ⎞
=
Bm
x
1
4
--- ε
5
ε
6
ε
7
– ε
8
– + ( ) =
Bm
x
w
4
----
ε
5
ε
6
ε
7
– ε
8
– +
w 2d –
---------------------------------------
⎝ ⎠
⎛ ⎞
=
Bl
x
1
4
--- ε
9
ε
10
ε
11
– ε
12
– + ( ) =
Bl
x
w
4
----
ε
9
ε
10
ε
11
– ε
12
– +
w 2d –
----------------------------------------------
⎝ ⎠
⎛ ⎞
=
Upper Gages Middle Gages Lower Gages
PBS
x
4 Bu
x
( )
ε
1
ε
2
ε
3
ε
4
+ + +
--------------------------------------- 100 × = PBS
x
4 Bm
x
( )
ε
5
ε
6
ε
7
ε
8
+ + +
--------------------------------------- 100 × = PBS
x
4 Bl
x
( )
ε
9
ε
10
ε
11
ε
12
+ + +
---------------------------------------------- 100 × =
PBS
y
4 Bu
y
( )
ε
1
ε
2
ε
3
ε
4
+ + +
--------------------------------------- 100 × = PBS
y
4 Bm
y
( )
ε
5
ε
6
ε
7
ε
8
+ + +
--------------------------------------- 100 × = PBS
y
4 Bl
y
( )
ε
9
ε
10
ε
11
ε
12
+ + +
---------------------------------------------- 100 × =
Upper Gages Middle Gages Lower Gages