MECH33623 Point bendingMaterials 2bending lab reportAim:To determine the flexural strength and modulus of the glass slide using a three point bending test.Results1) Both sides of the glass sanded with coarse sand paper.Geometry of Specimen:

L50mm

t25.513Mm

c0.513Mm

I2.29627E-12m^4

Flexural Strength

P22.79N

M0.284875Nm

fb63.64MPa

2)

Flexural Modulus

K = P/v57900N/m

E65.66GPa

3)

4) Fracture load P = 22.79N

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 beFlexural Modulus (E) = 63.51 GPa

6) Name (MPa)E (GPa)Treatment

Robert83.5071.12None

andi60.6967.79None

cat65.4367.08Top Side, Compression

Miao59.7867.34Bottom Side, Tension

Junting71.2272.53Both Side

HongJian57.3761.59Top Side, Compression

Joey44.5756.40Bottom Side, Tension

Kevin105.4884.92Both Side

runming62.6666.61Both Side

dixon74.5862.81Top Side, Compression

flynn63.6463.51Both Side

Average Stress (MPa)68.08

Average E (GPa)67.42706174

Standard Deviation ()15.92391202

Standard Deviation (E)7.342137271

DiscussionDiscussion:1) By observing the force vs displacement curve, it can be seen that it is not completely linear. 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.

2) The calculated values of both the flexural strength and modulus were lower than the average. 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 average would 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.

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