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ANAT2012 > Mechanical Properties of Materials > Flashcards

Mechanical Properties of Materials Flashcards

1
Q

What are 4 concepts in regards to mechanical properties of bone

A
  1. Bone has good fracture toughness = strong = risk of fracture
  2. 1 downward force on the compressive surface = shorter (drawn together)
  3. 2 upward forces on the tensile surface= longer
  4. Neutral axis/plane: the place where the forces are neither compressive or tensile
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2
Q

Why are having hallow bones important?

A
  • Has a resistance for bending
  • Larger diameter= stronger = more resistant
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3
Q

Why is an oval cross section for bone is better than round-cross section?

A

Pixel of bones are further away = increased distance = increased pixel of bones with resistance

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4
Q

What is stress?

A

Force/area

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5
Q

What is strain?

A

change in length/original length

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6
Q

What is permanent set/offset?

A

Damage of material- Doesn’t go back to original

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7
Q

What is elasticity?

A
  • The ability of a solid to recover its shape when the deforming forces are removed
    • Regardless of stiffness
  • Deformation depends on Hooke’s law
    • Deformation is proportional to the applied stress up to a certain point= elastic limit/yield point
    • Beyond this point, will cause permanent deformation
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8
Q

What is compliance?

A

Ability to deform under force

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9
Q

Tendons have a _____ structure.

A

helical

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10
Q

2 components of tendons

A
  1. • Tropo-collagen strands to become larger and larger structures
    • Start with collagen Microfibrils fibrils fibres fascicle tendon
  2. When a crimp is straightened, tendons behave elastically until failure
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11
Q

What is viscoelasticity?

A
  • • Relationship between stress and strain dependent on time
  • Constant stress = strain with time (creep)
  • Constant strain = stress with time (relaxation)
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12
Q

When loaded slowly, reacts in a ____ fashion

A

Ductile

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13
Q

When loaded quickly, react in a ____ fashion

A

Brittle

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14
Q

The effective stiffness depends on _______ of the load. Why?

A

rate of application

  • Higher the loading rate = the stiffer, stronger and more energy stored
    • More cracks or pieces created o Area under the curve = energy stored
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15
Q

If cyclic loading is applied, _______ occurs dissipation of mechanical energy

A

hysteresis (a phase lag)

  • Tendon gets stretched and recoiled
  • 95% of energy can be reused
  • 5% is lost as internal friction (heat)
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16
Q

Rebound of an object following impact is less than ____%

A

100%

  • Heel fat pads held together by collagen
  • Rebound is 70%, allowing them to recover/reform between foot-strike
  • Provides cushioning during repeated loading and unloading
17
Q

What is an isotrophic material?

A

A homogenous material that looks the same in every direction and exhibits material properties that are not orientation-dependent

18
Q

What is an anisotrophic material?

A
  • Behaviour changes based on microstructure
  • Orientation-dependent
  • Eg. bone is better at resisting longitudinal load than other directional load
19
Q

Ligaments have a fairly _____ structure.

A

Uniform

20
Q

4 components of ligaments

A
  1. Similar length pieces of collagen
  2. Short
  3. Bone to bone (over joints)
  4. Contains elastin o modulus
    • extensibility o strength
21
Q

Ligaments VS tendons during failure

A
  • Ligaments break in parts = graded failure
    • If loading stops, might recover
    • Tendons break all together = abrupt failure
22
Q

Ligaments have a ___ failure.

A

Graded failure - break in parts If loading stops, might recover

23
Q

Tendons have a ____ failure

A

Abrupt failure- break all together

24
Q

_____ held in a pressurized fluid-gel matrix in cartilage

A

Collagen fibrils

25
Q

Collagen is resistant to ______ forces.

A

Compressive

26
Q

Cartilage has ______ to decrease wear and tear.

A

Synovial fluid. With synovial fluid = low coefficient of friction= smooth movements = little wear and tear (except osteoarthritis)

27
Q

Most cells have a _____ no. of times that they can repair and regenerate. ______ occurs when the tissue has been worn out

A

finite Cell death

28
Q

What is mechanotransduction?

A

• Physical adaptation • Pathological fracture healing • Therapeutic distraction osteogenesis Includes 4 stages: 1. Mechanocoupling o transduction of physical forces to a mechanical signal, which is sent to the sensor cells 2. Biochemical coupling o mechanical signal is converted into a biochemical signal 3. Transmission of signal from sensor cell to effector ell 4. Effector cell response • Mechnical stimulation of specific pathways and genes can enhance proliferation and differentiation of osteoblasts

ANAT2012 (31 decks)

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