Material Properties (Yr 11 stuff)

Question 1

Types of Hardness testing

Answer 1

1. Brinell
2. Vickers Pyramid
3. Rockwell

Question 2

what is the Rockwell hardness test?

Answer 2

• is a test to the hardness of a material.
• this is a test vis indentation
• forces an indenter into the material and the number derived depends on how far the indenter sank into the material
• the larger the number the harder the material is

Question 3

What is a notched bar impact test?

Answer 3

The Izod and Charpy impact test are used to measure the capacity of a material to resists shock loadings
- Charpy is a common measurement to toughness

Question 4

What is Strength (general)?

Answer 4

is one of the most important mechanical properties since it determines the ability of a material to withstand stress without failure.

Question 5

What is tensile strength?

Answer 5

This is the maximum amount of pull that a material will withstand before breaking.

Question 6

What is compressive strength?

Answer 6

Compressive strength is a measure of the maximum crushing stress a material can endure before failure

Question 7

What is shear strength?

Answer 7

Shear strength is a measure of the resistance materials offer to forces which tend to cause sliding of one part of the materials over another part.

• is measured is megapascals or kilopascals

Question 8

What is Hardness?

Answer 8

This is the materials ability to resist indentation, scratching.

Question 9

What is Brittleness?

Answer 9

the property of a materials which permits no permanent distortion before breaking. Cast iron, which breaks easily, is an example of a brittle metal.
- or glass

Question 10

What is Ductility?

Answer 10

This is the ability of the material to be permanently deformed without breaking. - Metals such as copper may be drawn into wire, are ductile materials.

Question 11

What is Toughness?

Answer 11

This is the property of a metal to withstand shock or impact. Toughness is the opposite condition to brittleness.

Question 12

What is Elasticity?

Answer 12

This is the ability of a metal to return to its original shape after any force, acting upon it has been removed.

• derived from the load

Question 13

What is stress?

Answer 13

defined as the distribution of internal force per unit area within the specimen

Question 14

what is the stress formula?

Answer 14

s = P where: s = stress (Pa: Pascal)
A P = load (N)
A = area(mm2 for Mpa)
(m2 for Pa)

Question 15

What is Strain

Answer 15

defined as the change per unit length in a linear dimension

• strain is the change in shape of a material due to an applied load

Question 16

What is the strain formula?

Answer 16

D = e = WL . = change in length where: D = strain (no units)
L L original length WL = elongation (change in length)
L = original gauge length

Question 17

what is Young’s Modulas?

Answer 17

is a mechanical property that measures the stiffness of a solid material. It defines the relationship between STRESS (force per unit area) and STRAIN (proportional deformation) in a material in the linear elastic region.

Question 18

What does Young’s theory state?

Answer 18

states that up to the elastic limit the slope of the curve is a measure of the stiffness of the material.

Question 19

Young’s Modulus equation

Answer 19

E = \frac{\sigma}{\varepsilon}
E = Young’s modulus, pressure units
\sigma = uniaxial stress, or uniaxial force per unit surface, pressure units
\varepsilon = strain, or proportional deformation (change in length divided by original length), dimensionless

• the higher the value the stiffer the material

Question 20

What is Proportional limit?

Answer 20

defined as the point up to which the stress and the strain are directly proportional

Question 21

what is elastic limit?

Answer 21

Ma stress a material can endure before deformation, the material no longer has elastic behaviour

Question 22

what is the yield point?

Answer 22

the amount of stress present in the material before permanent deformation