Second Year Class Tests Flashcards
The bonding energy is:
The energy required to break a bond between atoms
The strength of metals may be increased by:
Decreasing the grain size Conducting a cold work process
The engineering stress is also called
The nominal stress
The constant of proportionality in the elastic region of a stress-strain diagram is
The Young’s modulus/ elastic modulus
Strongly bonded materials have
High elastic modulus, high melting temperature and low Coefficient of thermal expansion
What are elastic moduli
Bulk modulus Shear modulus Young’s modulus
Crystalline materials…
Tend to be densely packed, and have a long range order
Permanent deformation of a material begins to occur when the tensile (or compressive) uniaxial stress
Exceeds the yield strength
The AISI-SAE steel designation system uses four digits XYWZ:
X= Group Y=Alloy WZ=Concentration of Carbon
The stress concentration factor (Kt) depends on
Geometrical proportions (D/d and r/d)
Matensitic steels (weld?)
Martensitic steels can be welded, you need to be careful with the cooling rate (not recommended)
When an eutectoid carbon steel is cooled down from the austenized region and under equilibrium conditions the resultant microstructure is
100% pearlite
The hardenability of a metal can be determined with the use of
A Jominy test
The spherodizing heat treatment..
Is conducted to enhance the ductility of pearlite and bainite
To recover some ductility of a steel with 100% martensite in it structure we should conduct
A tempering process
In a normalizing heat treatment…
The sample is cooled outside the furnace by air (normally room temp)
A Jominy distance represents
A cooling rate
Dislocations…
make industrial forming treatment possible,are mobile under externally applied stress, and allow plastic deformation to occur
Which phases you will expect in a hypo-eutectoid carbon steel that was heated to austenite region and cooled to room temperature under equilibrium conditions?
Ferrite + pearlite
The tendency of a steel to form martensite can be measure through
a harden-ability test.
The three stages of the annealing process are:
Recovery, Recrystallization, Grain growth
Isothermal transformation diagrams are also called..
TTT (Time-Temperature-Transformation) diagrams.
What are the classifications of a metal regarding the percentage of carbon? (steels/irons)
A wrought iron has less than 0.008 wt% C, A steel has a wt% C between 0.008% and 2.14%, A cast iron has wt% C between 2.14% and 6.70%
The maximum solubility of carbon in austenite at 1148 C is:
2.11%
Which steels has more tendency to form martensite?
Medium carbon steels (wt.%C between 0.25% and 0.6%), High carbon steels (wt.%C between 0.6% and 1.4%)
The recrystallization temperature is..
The temperature at which recrystallization just reaches completion in 1 hour.
The following microstructure corresponds to :
A eutectoid carbon steel in an annealed condition
The Miller indices for the plane shown in this unit cell are;
(2 1 1)
The Miller indices for direction shown in this cubic cell are
[1 0 2]
Is powder metallurgy techniques are used to make polymers components by combining temperature and pressure?
NO!
Does creep strain increases when temperature or stress increases
Yes!
What is heated to 700 oC for about 30 hours to recover some ductility?
White Iron
To ensure that a material is not susceptible to brittle fracture under specific conditions, we would preform a…?
Charpy test or Izod test
What do high temperatures have an effect on?
Vacancies concentration
Mobility of atoms
Creep rate
Does the microstructure of the parent material changes depending on the welding process used?
nope!
Does the addition of Mg or Ce to a white iron produce changes in the graphite’s shape?
No
Which aluminium series can be age harded?
2XXX, 6XXX and 7XXX
What does this picture represent in terms of a failure?
Some necking.
Not fully ductile or brittle
What are characteristics of fatigue failure surface?
Striations, Beach marks, Final fracture zone
What can the ability of a material to absorb vibration be measured through?
A damping test
What is is the chief ore of aluminium?
What are characteristics of transient creep?
Creep rate decreases with time,
Deformation is fast at early stages,
Deformation rate becomes slower as it approaches a fixed value
What does the type of fracture depend on?
The environment the component is working in.
This is why DBTT are important to know when selecting a material.
Why is the flow ability property of the green sand used in sand casting process imortant?
To allow the sand to shape easily around intrinsic shapes of the model
How does the transition temperature and impact energy change as the %C in a steel increases?
Transition temperature increases
The impact energy decreases
What are mechanical failures?
Some are:
Fracture,
Fatigue,
Corrosion,
Creep
What is the formation of graphite in the cast iron promoted by?
The addition of silicon,
slow cooling temperature
The description of a stress-strain curve of brittle material is:
A curve where only the elastic region (small toughness) is observed and probably small plastic region
