9. SIMPLE HARMONIC MOTION (SHM) (PART 2) Flashcards
1
Q
- Are many biological materials anisotropic or isotropic?
Give 2 examples.
A
- they are anisotropic
EG: oesophagus, small intestine
2
Q
- Which bones in the body are most resistant to any form of stretching?
A
- the bones in the leg
3
Q
- Which formula for stress (σ) is valid until the stress reaches its maximum capacity before a fracture occurs?
A
- σ = Yε
4
Q
- What is the Ultimate Compressive Stress (UCS)?
A
- it is the amount of stress a bone can withstand before it fractures
5
Q
- What is the ultimate compressive stress for a compact bone?
A
- 170 MPa
6
Q
- How do we work out how much the bone has shortened by?
A
- ▵L = σ. L original / Y
- ▵L = change in length
- σ= stress
- Lo/Loriginal= the original length of the bone before
the applied stress - Y = Young’s Modulus
7
Q
- Up until when is the Hookean Stress- Strain relation valid in tension and compression?
Hookean Stress- Strain: Y = σ/ε
A
- it is valid up until a limiting stress
- this is where a fracture happens
8
Q
- Up until which point is there Elastic Hookean Behaviour?
A
- up until Point P
- this is the Proportional limit
9
Q
- What can be said about the slope up until Point P?
A
- it is constant
10
Q
- What happens at higher stresses?
A
- the stress-strain relationship becomes nonlinear
11
Q
- What can the object do up until the elastic limit?
A
- the object an return to its initial length when the stress is removed
- it does no go through deformation
12
Q
- What happens for stresses beyond the elastic limit?
A
- there is permanent or plastic deformation
- this is irreversible
- the object can no longer return to its initial length after the stress has been removed
13
Q
- What is the yield point?
A
- it is a stress higher than the elastic limit
14
Q
- What can occur after the Yield point?
A
- much elongation can occur
- without much increase in the load
15
Q
- What can the material do up until the Ultimate Tensile Stress (UTS)?
A
- the material can remain intact for larger stresses up until this point
- the larger the breaking point:
- the stronger the material
16
Q
- What does the application of stress result in at point F?
A
- a fracture in the material/object
- this occurs at a strain called the Ultimate Strain
- this is also known as the Ultimate Percent Elongation (UPE)
17
Q
- Why do the stress -strain relations look qualitatively different for ceramics, metals and elastomers?
A
- each of these has very different microscopic structures
- they have different Young Moduli
18
Q
- What kind of stress-strain relationship do ceramics have?
A
- they have a linear stress-strain relationship
- it has a large Young Modulus slope
- this means it is a tough material
19
Q
- What can be said about the fracture point of ceramics?
A
- it appears only a little into the nonlinear elastic region
- it appears for smaller values of strain
(values less than 0.1)
20
Q
- Is bone similar to ceramic?
A
- yes
21
Q
- What can be said about the properties of metals?
A
- they have a smaller Young Modulus
- they are less tough than ceramics
- they have a larger non-elastic and plastic region
- they have a larger Ultimate Percent Elongation
22
Q
- What can be said about the properties of elastomers?
A
- they distort greatly
- even when small stresses are placed on them
- it takes much larger stresses to increase the strain further after a certain point
- they have a very large ultimate percent elongation
( it is usually greater than 1)
23
Q
- What are some examples of Elastomers?
A
- rubber, polymers, blood vessels
24
Q
- What can be said about the plastic deformation phase of ductile materials?
A
- it is extensive
25
Q
- Give 4 examples of ductile metals?
A
- modelling clay
- chewing gum
- plastic
- most metals
26
Q
- What can be said about the plastic deformation phase of brittle materials?
A
- they have a limited or essentially no plastic phase
27
Q
- What are 5 examples of brittle materials?
A
- glass
- ceramics
- cast iron
- bone
- teeth
28
Q
- What resists tension in cartilage?
A
- solid components
29
Q
- What resists compression in cartilage?
A
- solid and liquid components
30
Q
- In ligaments and tendons, is there resistance to both tension and compression?
A
- no
- there is only resistance to tension
31
Q
- Where do fractures occur?
A
- at the ultimate compressive stress (UCS)
- this is different from the Ultimate Tensile Stress
32
Q
- What does compact bone (cortical/dense bone) have with regards to its Young’s Modulus?
What does this mean with regards to resistance to compression and tension?
A
- it has a large Young’s Modulus
- this is comparable to that of other strong materials
- it can withstand more stress in compression than in tension
33
Q
- What can be said about the Young’s Modulus of spongy or cancellous bone?
A
- it is more porous
- it has a very small Young’s Modulus
34
Q
- Which aspects of the human body are hard materials with similar stress-strain curves that are ceramic like?
A
- bones
- teeth
- nails
35
Q
- Which aspects of the human body have more elastomer like properties?
A
- tendons
- cartilage
- resting muscles
- skin
- arteries
- intestines
36
Q
- Name 6 body materials that cannot be modelled as Hookean springs?
A
- collagenous tissues
- tendons
- mesentery
(the folds attached to intestines and the dorsal
abdomen) - sclera
- cartilage
- resting skeletal muscles
37
Q
- Read through this summary.
Does everything make sense?
A
- yes
38
Q
- Read through this summary.
Does everything make sense?
A
- yes
39
Q
- Read through this summary.
Does everything make sense?
A
- yes
40
Q
- Read through this summary.
Does everything make sense?
A
- yes
41
Q
- Read through this summary.
Does everything make sense?
A
- yes
42
Q
- Read through this summary.
Does everything make sense?
A
- yes
43
Q
- Read through this summary.
Does everything make sense?
A
- yes
44
Q
- Read through this summary.
Does everything make sense?
A
- yes
45
Q
- Read through this summary.
Does everything make sense?
A
- yes
46
Q
- Read through the summary.
Does everything make sense?
A
- yes