Material Properties

Question 1

Definition of a load?

Answer 1

Force that acts on a body

Question 2

Def of stress?

Answer 2

Force per unit area (intensity of an internal force) - Pascals

Question 3

Strain definition?

Answer 3

Change in length/ original length

Question 4

What is elastic deformation?

Answer 4

REVERSIBLE changes in shape of a material due to a load

Question 5

What is plastic deformation?

Answer 5

IRREVERSIBLE changes in shape of an object in response to a load

Question 6

Def of toughness?

Answer 6

Amount of energy/ unit volume

= Area under the tree/strain curve

Question 7

What is creep?

Answer 7

Time dependant deformation under a CONSTANT LOAD

Question 8

What is load relaxation?

Answer 8

Decrease in applied stress under CONSTANT STRAIN

Question 9

What is hysteresis?

Answer 9

Loading curve does not follow the unloading curve = energy dissapation
Found in viscoelastic materials

Question 10

What is the elastic zone?

Answer 10

Part of the SSC where a material will return to its original shape

Question 11

What is the Toe region

Answer 11

Found in tendons and ligaments - represents the crimped fibres uncrimping

Question 12

What is the Yield point?

Answer 12

Change point between elastic and plastic deformation

Question 13

What is the plastic zone?

Answer 13

Zone in which object will not return to its original shape for given amount of stress

Question 14

What is the ultimate tensile strength?

Answer 14

Load to failure

Question 15

Hookes law?

Answer 15

Material in the elastic zone - stress is directly proportional to strain

Question 16

What is the Youngs modulus?

Answer 16

Measure of stiffness of materials in the elastic zone

Slope of the SSC

Question 17

List the Young’s modulus of metals and biologics from 1-11

Answer 17

1. Ceramic
2. Alloy (Cobalt)
3. Stainless steel
4. Titanium
5. Cortical bone
6. Matrix polymers
7. PMMA
8. Polyethylene
9. Canacellous
10. Tendon/ligament
11. Cartilage

CAST CMP PCT C

Question 18

What is a brittle material?

Answer 18

Exhibits linar SS relationship until failure
ONLY ELASTIC DEFORMATION
LITTLE/NO PLASTIC DEFORMATION

Question 19

Define a viscoelastic material?

Answer 19

SS relationship depends on duration and rate of applied load

Ligament and Bone

Question 20

Isotropic materials possess?

Answer 20

Same mechanical properties in all directions

Question 21

Anisotropic materials possess?

Answer 21

Different mechanical properties depending on direction of applied load

Question 22

What is necking?

Answer 22

Localized reduction in cross sectional area in a specimen under a tensile load

Question 23

Where is necking located on the SS curve?

Answer 23

Between ultimate tensile strength and fracture/rupture