1. Stress/Strain Measurement
OPTI421/521L

2. Materials Aluminum beam (1ea) Milling machine clamp (1set)
Ruler and/or Vernier calipers (1ea)
Strain gage (4ea)
Resistance (4ea)
Bread board (1 ea)
Power supply (1ea)
Digital volt meter (1ea)
Loctite (1ea)
Lead wires (1set)
Scotch tape (1ea)
Pencil (1ea)
Soldering iron and lead (1ea)
Light Box (1ea)
Acrylic beam (1set)
Polarizer (1ea)
Weight (1ea)
Dowel pins and fixture (1set)

3. How to glue the a strain gage
Locate where the strain gage to be glued
Where is the maximum strain observed in a cantilever beam (or simply supported beam)?
Clean the surface using acetone and alcohol then wait until the surface is completely dry
Mark the position where the strain gage to be glued using a pencil and ruler.
Position a strain gage and apply a piece of Scotch tape on it temporarily
Lift one end of the Scotch tape until the strain gage is exposed
Apply a drop of Loctite and press the Scotch tape from a side
Squeeze Loctite out to build a thin bond layer
Wait until the Loctite to be fully cured
Peel off the Scotch tape from a side and inspect the Strain gage

4. Strain Gage Lab
Check nominal gage resistance and gage factor from the specification
Gage resistance (Ω):
Gage factor:
Measure the dimensions of the aluminum beam
Length (in):
Width (in):
Thickness (in):
Glue 4 strain gages on an aluminum beam as a cantilever beam
Two strain gages on each side
Location of the strain gages from the fixed(or supported) point of the beam (in):
Build a wheatstone bridge on the bread board using given resistances
Check voltage output between C and D

5. Strain Gage Lab Quarter Bridge Half Bridge
Configure a Quarter bridge by substituting R1 to one of strain gages
Measure Vout with no load condition
Vout (V):
Apply load by hanging a weight at the end of the cantilever beam (or the center of the simply supported beam)
Weight (lb):
Measure Vout under loading
Measure the deflection at the end of the beam
Deflection (in):
Configure a Half bridge by substituting
R1 and R2 (R3 and R4) to the two strain gages on the same side
R1 and R3 (R2 and R4) to the two strain gages on the opposite side
Measure Vout with no load condition
Vout (V):
Apply load by hanging a weight at the end of the cantilever beam (or the center of the simply supported beam)
Weight (lb):
Measure Vout under loading
Measure the deflection at the end of the beam
Deflection (in):

6. Strain Gage Lab Full Bridge Result
Configure the Full bridge by substituting R1~R4 to the strain gages
Measure Vout with no load condition
Vout (V):
Apply load by hanging a weight at the end of the cantilever beam (or the center of the simply supported beam)
Weight (lb):
Measure Vout under loading
Measure the deflection at the end of the beam
Deflection (in):
Apply the strain gage equation and find measured strain
Quarter bridge :
Half bridge :
Full bridge:
Apply Stress-Strain relation to find measured stress
Quarter bridge (psi):
Half bridge (psi):
Full bridge (psi):
Write a beam equation and find the deflection under the given loading condition
Deflection (in):
Does it match to your measurement?
Calculate the stress where the strain gages are using the beam equation
Stress (psi):

7. Photo Elasticity Install the light box and polarizer
Configure a cantilever beam using the transparent Acrylic beam in front of the light box
Install the polarizer and observe the pattern through the beam
Take a photo
Apply load by hanging a weight to the end of the beam
Show the two photos and discuss about your observation
Install the light box and polarizer
Configure a simply supported beam using the transparent Acrylic beam in front of the light box
Install the polarizer and observe the pattern through the beam
Take a photo
Apply load by hanging a weight to the center of the beam
Show the two photos and discuss about your observation