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MECH3362 3 Point bending Flynn Gould
Materials 2 bending lab report 311225977
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Aim:
To determine the flexural strength and modulus of the glass
slide using a three point bending test.
Results
1) Both sides of the glass sanded with coarse sand paper.2)
3)
4) Fracture load P = 22.79N
Geometry of Specimen:
L 50 mm
t 25.513 Mm
c 0.513 Mm
I 2.29627E-12 m^4
Flexural Strength
P 22.79 N
M 0.284875 Nm
fb63.64 MPa
Flexural Modulus
K = P/v 57900 N/m
E 65.66 GPa
y = 0.0559x
-0.005
0
0.005
0.01
0.015
0.02
0.025
0 0.1 0.2 0.3 0.4 0.5
Load
(kN)
Deflection (mm)
Load vs deflection diagram
Series1
Linear (Series1)
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MECH3362 3 Point bending Flynn Gould
Materials 2 bending lab report 311225977
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Using the data from the tables in section 2 and the formulas
above the flexural strength was
calculated to be
Flexural Strength(fb)= 63.64 MPa
5) Load deflection diagram along the linear portion from 0.1mm
to 0.2mm
Therefore: dp/dv = 0.056 kN/mm = 56000 N/m
Using the slope taken from the diagram, the geometry of the
specimen and the formulas
above the flexural modulus was calculated to be
Flexural Modulus (E)= 63.51 GPa
y = 0.056x - 0.0017
R = 0.9997
0
0.002
0.004
0.006
0.008
0.01
0.012
0 0.05 0.1 0.15 0.2 0.25
Load
(kN)
Deflection (mm)
Load vs Deflection diagram
Series1
Linear (Series1)
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MECH3362 3 Point bending Flynn Gould
Materials 2 bending lab report 311225977
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6)
Discussion
Discussion:
1) By observing the force vs displacement curve, it can be seen
that it is not completelylinear. Which would suggest that the
components within the crosshead which have some
backlash or is picking up interference as the specimen begins to
crack.
The specimen suffered from brittle fracture suddenly with a loud
crack. The displacement
was only 0.4mm.
After calculating the slope of the graph several times the most
linear section was selected
as seen by the R^2 values of the trend line.
Name (MPa) E (GPa) Treatment
Robert 83.50 71.12 None
andi 60.69 67.79 None
cat 65.43 67.08 Top Side, Compression
Miao 59.78 67.34 Bottom Side, Tension
Junting 71.22 72.53 Both Side
HongJian 57.37 61.59 Top Side, Compression
Joey 44.57 56.40 Bottom Side, Tension
Kevin 105.48 84.92 Both Siderunming 62.66 66.61 Both Side
dixon 74.58 62.81 Top Side, Compression
flynn 63.64 63.51 Both Side
Average Stress (MPa) 68.08
Average E (GPa) 67.42706174
Standard Deviation () 15.92391202Standard Deviation (E)
7.342137271
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MECH3362 3 Point bending Flynn Gould
Materials 2 bending lab report 311225977
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2) The calculated values of both the flexural strength and
modulus were lower than theaverage. This is most likely due to the
range of different treatments that were
applied to the glass slides as well as pre-existing defects. If
all the slide has no
treatment or a controlled method of applying one type of
treatment the averagewould be closer together.
Both values, however, fall roughly within the range as specified
by a material science
website. For example, the expected value for the flexural
modulus of glass is between
5090GPa; my value was 63.51Gpa.
Conclusion: Two key properties of the glass material were
determined which would have otherwise
been difficult using a regular stress-strain test. These
properties were the flexural modulus and
strength, which were 63.51GPa and 63.64MPa respectively.
