1. Lecture 9 – Deformation and Damage
Review of terms:
Normal stress, σ:
Normal strain, ε:
Plastic strain:
Elastic strain:
Degree of plasticity:
Degree of elasticity:
Modulus of elasticity, E:
Tangent Definition:
Poisson’s Ratio, μ:
Shear stress:
Shear strain:
Shear Modulus, G:
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BAE2022/BAE4400 Physical Properties of Biological Materials

2. Lecture 9 – Deformation and Damage
To determine the elastic modulus, E…
for steel flat plate:
for steel spherical indentor:
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BAE2022/BAE4400 Physical Properties of Biological Materials

3. Lecture 9 – Deformation and Damage
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BAE2022/BAE4400 Physical Properties of Biological Materials

4. Lecture 9 – Deformation and Damage
Example of plate deformation:
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BAE2022/BAE4400 Physical Properties of Biological Materials

5. Lecture 9 – Deformation and Damage
Example of spherical object deformation:
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BAE2022/BAE4400 Physical Properties of Biological Materials

6. Lecture 9 – Deformation and Damage
Stacked particles (grain, seeds, dirt clods)
Figure 5.1
Dropped particles
Grain bin and handling damage
Figure 5.3 – Table 5.13: example of product testing.
Broken or damage material: determined using sieves.
Bruised fruit: determined by visual inspection, spectral reflectance, Magness-Taylor pressure tester.
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BAE2022/BAE4400 Physical Properties of Biological Materials

7. BAE2022/BAE4400 Physical Properties of Biological Materials
Lecture 9
HW#6 Assignment
Problem 1:
Explain in YOUR OWN WORDS how an osmometer works and give an example of how one might be used in food engineering. (you will need to do some outside research…web, library…) Limit your answer to one page in MSWord 12pt. Font, double spaced, 1” margins
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BAE2022/BAE4400 Physical Properties of Biological Materials

8. BAE2022/BAE4400 Physical Properties of Biological Materials
Lecture 9
HW#6 Assignment
Problem 2:
An apple is cut in a cylindrical shape 28.7 mm in diameter and 22.3 mm in height. Using an Instron Universal Testing Machine, the apple cylinder is compressed. The travel distance of the compression head of the Instron is 3.9 mm. The load cell records a force of N. Calculate the stress εz , and strain σz on the apple cylinder.
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BAE2022/BAE4400 Physical Properties of Biological Materials

9. BAE2022/BAE4400 Physical Properties of Biological Materials
Lecture 9
HW#6 Assignment
Problem 3:
A sample of freshly harvested miscanthus is shaped into a beam with a square cross section of 6.1 mm by 6.1 mm. Two supports placed 0.7 mm apart support the miscanthus sample and a load is applied halfway between the support points in order to test the Force required to fracture the sample. If ultimate tensile strength is 890 MPa, what would be the force F (newtons) required to cause this sample to fail?
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BAE2022/BAE4400 Physical Properties of Biological Materials

10. BAE2022/BAE4400 Physical Properties of Biological Materials
HW#5 Assignment
Problem 4:
Ham is to be sliced for a deli tray. A prepared block of the ham has a bottom surface of 10 cm x 7 cm. The block is held securely in a meat slicing machine. A slicing blade moves across the top surface of the ham with a uniform lateral force of 27 N and slices a thin portion of meat from the block. The shear modulus, G, of the ham is 32.3 kPa. Estimate the deflection of the top surface with respect to the bottom surface of the block during slicing.
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BAE2022/BAE4400 Physical Properties of Biological Materials

11. BAE2022/BAE4400 Physical Properties of Biological Materials
HW#5 Assignment
Problem 5:
Sam, the strawberry producer, has had complaints from the produce company that his strawberries are damaged during transit. Sam would like to know the force required to damage the strawberries if they are stacked three deep in their container.
The damage occurs on the bottom layer at the interface with the parallel surface of the container and also at the point of contact between the layers of strawberries.
An hydrostatic bulk compression test on a sample of Sam’s strawberries indicates an average bulk modulus of 225 psi. Testing of specimens from Sam’s strawberry crop shows a compression modulus E of 200 psi. The average strawberry diameter is 1.25 inches and the axial deformation due to the damage in transit averages 0.23 inches. The modulus of elasticity for Sam’s variety of strawberries is reported to be 130 psi.
Estimate the force Sam’s strawberries may be encountering during transit. (Hertz method)
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BAE2022/BAE4400 Physical Properties of Biological Materials

12. Problem 6: HW question 5.1 Part a on page 187 of your book.
HW#5 Assignment
Problem 6:
HW question 5.1 Part a on page 187 of your book.
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BAE2022/BAE4400 Physical Properties of Biological Materials