Mechanical properties of mater

Question 1

What is the symbol for tensile stress?

Answer 1

sigma

Question 2

What is the equation for tensile stress?

Answer 2

sigma = F/A

Question 3

What does strain tell us?

Answer 3

How much something has changed by compared to it’s original length.

Question 4

What is the symbol for strain?

Answer 4

Epsilon

Question 5

What is the equation for strain?

Answer 5

Epsilon = x/L where x is the extension and L is the original length.

Question 6

What are the units for stress?

Answer 6

Nm^-2

Question 7

What are the units for strain?

Answer 7

Doesn’t have any units.

Question 8

What is the symbol for Young’s modulus?

Answer 8

E

Question 9

What is the equation to calculate Young’s modulus of a material?

Answer 9

E = stress/strain

Question 10

What is the typical YM of steel?

Answer 10

210GPa

Question 11

What is Young’s modulus a measure of?

Answer 11

The stiffness or a material.

Question 12

What are the units for YM?

Answer 12

Pa or Nm^-2

Question 13

Define Tensile stress.

Answer 13

The tension force per unit cross-sectional area of a material.

Question 14

Define Tensile strain.

Answer 14

The extension per unit length of a material

Question 15

Define Young’s modulus.

Answer 15

The tensile stress per unit tesnile strain.

Question 16

Sketch a stress-strain graph labelling with the elastic limit, yield point, limit of proportionality and UTS.

Answer 16

Look at notes!

Question 17

Define UTS.

Answer 17

Ultimate Tensile strength- the maximum stress a material can withstand before fracture.

Question 18

Define Elastic limit.

Answer 18

The value if stress or force beyond which elasrtic deformation becomes plastic deformation; the material will not retun to its original shape and size when the stress or force is removed.

Question 19

What can strain of 0.012 be written as?

Answer 19

1.2%

Question 20

How would you describe copper?

Answer 20

Ductile

Question 21

Define brittle.

Answer 21

A material that distorts very little even when subject to a large stress and does not exhibit much plastic deformation; for example, concrete or glass.

Question 22

Define polymetric.

Answer 22

Materials that consist of long molecular chains; they experience a high strain beofre braking.

Question 23

Define ductile.

Answer 23

Materials that have a large plastic region and therefore they can be drawn into a wire; for example copper.

Question 24

Draw a hysterisis loop for: rubber, polyethene and a matal wire.

Answer 24

Look at notes!

Question 25

Define a hysteresis loop.

Answer 25

A loop-shaped plot obtained when loading and unloading a material produce different deformations.

Question 26

When determining the YM what do you do with the diameter of the wire?

Answer 26

Measure it in 3 different places along the wire using vernier callipers.

Question 27

What is the best value for L which is the length from the block to the marker?

Answer 27

The longest possible value you can get will give you more accurate results.

Question 28

How would you clauclate the YM using the gradient from the graph x against mg?

Answer 28

E = L/A x gradient.