Lectures 4-7

Question 1

Hardness

Answer 1

The property of a material that enables it to resist plastic deformation, penetration, indentation and scratching.

Question 2

Moh’s scale

Answer 2

A scale using minerals which increasing with hardness

Question 3

What are the three hardness test?

Answer 3

Brinell, Vickers and Rockwell

Question 4

Brinell

Answer 4

-Static load, 100-3000kgf
-Ball diameter, 1-10mm
Dwell time, 10-30 seconds

Question 5

How do you calculate and write Brinell’s number?

Answer 5

BH=force/impression of indentation

Number/sphere type/diameter/load/time

Question 6

Vickers

Answer 6

Load:
-Micro- 10g-1kg
-Macro-1-100kg
Dwell time 10-15s
a diamond with an edge at 136 degrees

Question 7

VH calculation and number?

Answer 7

VH=force/surface area of impression

Number/HV/loadkgf

Question 8

Rockwell

Answer 8

Load:
Minor:10kgf
Major:60, 100 and 150kgf
Uses a minor load to cause an indentation and then the major load is added to make an impression.

Question 9

Specific heat capacity

Answer 9

The amount of energy used to change the temperature of an object per unit mass
Q=mcΔT
c=secifitic heat capacity

Question 10

How to calculate the linear heat coefficient of thermal expansion?

Answer 10

-ε=a*change in temperature

a=change in length/ original length*change in temperature

Question 11

How does the linear, area, and volume coefficient to thermal expansion change with each dimension?
(what the equation?)

Answer 11

Change in length=achange in temperature
Change in area=2achange in temperature
Change in volume3a*change in temperature

Question 12

Fourier’s law

Answer 12

heat flux=thermal conductivity/temperature gradient

q=-k(dT/dx)

Question 13

Thermal stress

Answer 13

σ=Ea*change in temperature

E=youngs modulus

Question 14

Lattice

Answer 14

A three-dimensional array of points with the identical surrounding.

Question 15

Unit cell

Answer 15

The smallest repetitive volume which contains the complete lattice pattern of the crystal.

Question 16

SC
BCC
FCC

Answer 16

Four in cube
four in a cube with one in the middle
four in a cube, with one in between each cube.

Question 17

what are the four-point defects

Answer 17

• vacancies
• interstitial atom
• Small substitution atom
• Large substitution atom

Question 18

Line defects

Answer 18

Dislocation: screw and edge

produce permanent plastic deformation

Question 19

Grain boundaries

Answer 19

Are the 2D representation of the material.

Effects conductivity and strength of an object

Question 20

Binary system

Answer 20

A system consisting of two materials

Question 21

Gibbs phase rule

Answer 21

F+V=C+n
V=variance
C=number of components
F=number of phases that coexist
n=physucal variables
-For constant pressures 
F+V=C+1

Question 22

The Lever Rule

Answer 22

-Shows the amount of liquid to solid ratio.
Wa=R/R+Q
R+Q=100%
R=ratio of liquid
Q=ratio of solid

Question 23

Binary system

Answer 23

A material with two or more substances, represented using a graph with percentage of weight on the x-axis