Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Basic Science > Biomechanics > Flashcards

Biomechanics Flashcards

(58 cards)

Start Studying
1
Q

What is an isotropic material?

A
  • The material behaves similarly in all directions of force
  • e.g. metals / alloys
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an anisotropic material?

A
  • A material shows directionally dependent behaviour e.g most living tissue. -cortical bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define stress ?

A
  • Force per unit area
  • In Newton / metre 2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is strain?

A
  • Change in length of a material/ original length
  • it has NO UNITS
  • doesn’t take into account x sectional area of material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is young’s modulus?

A
  • Stress /strain
  • N/m2
  • Gradient of stress/ strain graph
  • idea of stiffness I material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is stiffness?

A
  • Deflection under a given load.
  • The steeper the stress- strain curve the stiffer the material .
  • The less steep the curve the more flexible the material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the Yongs modulus of

cartilage

Tendon

Cancellous bone

UMWPE

Pmma

bone cement

Cortical bone

Ti alloy

Stainless steel

Colballt chrome

A

cartilage 0.02

0.5 Cancellous bone

1 UMWPE

Pmma bone cement 2

Cortical bone 20

Ti alloy 100

Stainless steel 200

Cobalt chrome 200

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is hook’s law

A
  • Where stress is proportional to strain such that deformation is recoverable- elastic portion of graph
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is yield stress ?

A
  • The stress necessary to produce a specific amount of permanent deformation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is yield point?

A
  • Point in the graph where plastic deformation starts-
  • the point at which further deformation is no longer recoverable
  • In ortho this is close to the yield stress
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What’s is strain hardening?

A
  • Where plastic deformation actually increases Materials resistance to further deformation
  • e.g. cold working of metal alloys
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is fracture stress?

A
  • A stress level at which a material’s integrity is breeched and is fractured
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the ultimate tensile stress?

A
  • The max amount of stress a material can with stand before fracture is imminent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is brittleness ?

A
  • Brittle materials do not deform plastically but display elastic behaviour right up to failure- e.g ceramic
  • yield stress almost = to fracture stress
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is ductility ?

A
  • A ductile material undergoes a large amount of plastic deformation before failure- e.g.metals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is strain energy?

A
  • The area under a stress- strain curve.
  • Combines recoverable strain energy - elastic region of curve and absorbed strain energy ( plastic region of curve)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is toughness?

A
  • The energy per unit volume that a material can absorb before failure.
  • The area under a stress/ strain graph
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is hardness?

A
  • Ability of the material to resist stratching and indentation on the surface
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is fatigue failure ? How is it demonstrated?

A
  • Failure of a material with repetitive loading at stress levels below the ultimate tensile strength
  • In a SN CURVE LOG STRESS VS LOG OF NUMBER OF CYCLES ( millions)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the endurance limit ?

A
  • Stress at which a material can withstand 10 million cycles without experiencing Fatigue failure typically hip operate above endurance limit, TKR operate at limit esp polyethylene -> fatigue failure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

In regard to materials shape what is stiffness and rigidity ?

A
  • Stiffness-the materials Ability to resist deformation
  • Rigidity- the structures ability to resist deformation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is notch sensitivity ?

A
  • **Is the extent at which the sensitivity of a material to fracture is increased by the presence of a surface inhomogeneity **
  • eg ductile materials (SS) have low notch sensitivity cf brittle materials such as ceramic/titanium have HIGH notch sensitivity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is Viscoelasticity?

A
  • Time dependent behaviour which is characterised by
  • CREEP
  • STRESS RELAXATION
  • TIME DEPENDENT STRAIN BEHAVIOUR
  • HYSTERESIS
  • ie in CARTILAGE, LIGAMENTS AND INTERVERTEBRAL DISCS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is creep?

Study These Flashcards
A
  • Time DEPENDENT DEFORMATION IN RESPONSE TO A CONSTANT LOAD
25
What is stress relaxation ?
* **TIME DEPENDENT DECREASE IN LOAD REQUIRED TO MAINTAIN A MATERIAL AT A CONSTANT STRAIN**
26
What is hysteresis?
* **The difference in a stress strain curve between loading and unloading is due to strain energy lost in heat from internal friction forces**
27
What is bending rigidity?
Second moment of area x young's modulus Incorporates the materials shape, size and structure Ie choosing a material that is stiff x2 chrome cf Ti makes a rectangular plate have a increased sma and. So rigidity increased by a third power ie 2 to the power 3 = 8
28
Describe time dependent strain behaviour?
* Behaviour of plastine * Gradually pull apart a blob of plastine -\> a long thin thread of plastine before it eventually breaks into two * however if we pull the plastine apart quickly, then the plastine breaks quickly * the strength required to break the plasticine is higher when pulling the plastine apart * the rate of change of length of plasticine ( the strain rate) affects the behaviour * the faster the strain rate m the higher the stress at a given level of strain * conversely a low strain rate requires more time but less stress to fx the material
29
When do tensile stresses occur?
When 2 forces pull away from each other along the same line
30
When do compressive stresses occur?
When 2 forces push towards each other along the same libe
31
What is Hooke's Law?
The force needed to extend or compress a spring by some distance is proportional to that distance. That is, F= Kx where k is a constant factor characteristic of the spring, its stiffness ie stress proportional to strain- the linear portion of the stress/strain graph where Young's modulus is constant
32
Draw a stress -strain curve and label the regions?
Diagram
33
What is the elastic region? What can you determine here in this part of the graph?
The stress- strain relationship is linear. Hooke's law is obeyed- stress proprtional to strain Young's Modulus- the stiffness increases as the gadient of the line increases ALL the deformation in this part of the graph is ELASTIC ie RECOVERABLE
34
What is the toe region? name an example?
* The initial portion of the curve where there is a no linear relationship uncrimping of collagen fibres in tendons- as the tendon is stretches the collagen unfurl until they are straight and then stiffness increases quickly
35
What is the plastic region of the graph? Where does this commence from?
AT this point further deformity is NO LONGER RECOVERABLE ie PLASTIC At the YIELD POINT
36
What is the YIELD POINT?
Where there is A DRAMATIC INCREASE IN STRAIN WITH LITTLE INCREASE IN STRESS
37
What follows the yield point?
A PEFECT PLASTIC REGION then a region where STRAIN HARDENING occurs
38
What is the STRAIN HARDENING ?
The phenomon where PLASTIC DEFORMATION ACTUALLY INCREASES THE MATERIALS RESISTANCE TO FURTHER DEFORMATION e.g.- COLD WORKING OF ALLOYS
39
What is YIELD STRESS?
The STRESS NECESSARY TO PRODUCE A SPECIFIC AMOUNT OF PERMANENT DEFORMATION i.e 0.002 - 2%- very close in ortho to the yield point
40
What is strength of a material?
* It represents the **DEGREE OF RESISTANCE TO DEFORMATION OF A MATERIAL** * a material is strong if it has a high ULTIMATE TENSILE STRENGTH
41
What is Hardness of a material?
The SURFACE PROPERTY OF A MATERIAL; THE ABILITY OF A MATERIAL TO RESIST STRATCHING AND INDENTATION ON THE SURFACE not determined by the stress strain curve
42
What are the underlying mechanisms responsible for disco-elastic behaviour?
FRICTION internally between micro-elements in the structure. Movement of interstitial fluid through the material creates a drag that produced the viscoleastic behaviour
43
What is a shearing force?
* **IS A force applied PARALLEL to or in line with the SURFACE OF AN OBJECT**
44
When do SHEAR FORCES occur?
* **2 FORCES are directed to parallel to each other but not along the same line or the same direction**
45
When do tensile stresses occur?
* When 2 forces pull away from each other along the same line
46
What is shear modulus?
* **Shear modulus = shear stress/ Shear strain** * shear modulus is between **30-50% of the elastic modulus for most materials** * bone is weakest against shear forces ( also tensile), while strong in compression * Bone tends to fail in shear
47
What is the neutral axis of a beam?
* A cross section area of a beam, there is graduation of stresses from extreme edges of the beam, where the compressive ( posterior) and tensile forces ( anterior) respectively towards the centre of the beam. * The midpoint where there is no resulting force is the neutral axis
48
How do we calculate the bending stress?
* _Applied force x distance from neutral axis_ _​_ second moment area of material
49
what is the second moment area of material? What affects it?
* Is a variable that decribes the spatial distribution of a material within a structure * the type of material does not affect the SMA * Organisation and shape of the material affects SMA
50
What is the second moment area of material for a rectangle?
* The perpendicular distance away from the neutral axis h has a **third power effect** on SMA
51
what is the second moment area of material for a solid circular cross section?
* **The radius ( which the distance from the neutral axis) has a _4th power_ effect on the SMA**
52
What is the effect on SMA with a hollow circular cross section?
* The total SMA = **the SMA of the Solid portion - SMA of the missing inner hollow portion**
53
What is the larger SMA for a solid or hollow pipe?
* Comparing the SMA of a solid rod to a hollow rod, the SMA is larger for the **hollow pipe** * **As a result the hollow pipe deforms less ( ie stronger) than the solid pipe of the same cross sectional area** * e.g as bone ages the outward appostional growth enlarges the medullary canal and increases the overall girth of the whole bone. * **this increase the SMA and with it the strength and resistance to fatigue to fx**
54
What is bending rigidity?
* **SMA x Youngs modulus** * rigidity then incorporates both the nature of the material and its shape, size and structure * e.g doubing the thickness of a rectangular plate -\> increase in SMA and increase rigidity by a third power of the multiplication * ie doubling plate **23 = 8**
55
What is a torsional force?
* _Equal and opposite shear forces_ as applied to a cyclinder constrained in space-\> twist= torsional force
56
How do you calculate the shear stress generated by the torque forces at any given point ?
* Shear stress= Applied torque x distance from axis of twist/ polar moment of intertia
57
What is the polar moment of internia?
* Similar to SMA * is a variable parameter related to size and shape of a structure but not the material from which it is constructed
58
What is torsional rigidity?
* = PMA x Shear modulus * a measure of the resistance of a material in a particular size nad shape to torsional forces * so a cylinder the PMA varies to the power 4 radius * so IM rod that is tiwce at thick has 24=16 x the rigidity * when cf nails of the same diameter & length , cannulation or slotting of the nail decreases the PMA according to the earlier formula * so torsional rigidity of slotted nails is lessened although bending ridigity is affected only minimally

Basic Science (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions