final Fall 2018

A 1020 steel wire is drawn 10% to a diameter of 9mm, and successively further drawn to a diameter of 8mm. Calculate the total percent cold work done on the wire.

%CW=[(Ao-Af)/Ao]*100 answer is 28.9% but that isn't an answer choice???

From the back page Figure 2 for the iron-iron carbide phase diagram, calculate the percent a and Fe3C for steel 1040 (0.4% carbon content) for the temperature at 726C, just below the Eutectoid line.

%a=(6.7-0.4)/(6.7-0.022) D) a=94% Fe3C=6%

The following are slip systems in a BCC metal

(011)[111-], (101)[111-], (11-0)[111], (110)[1-11]

In a Brinell hardness test, a 1500-kgf load is pressed into a specimen using a 10-mm diameter hardened steel ball. The resulting indentation has a diameter of 3.2 mm. Determine the Brinell hardness number for the metal

(P=1500, D=10, d=3.2) 182 BHN

Which of the following is not a common ingredient in cemented carbide cutting tools (2 correct answers)

(a) Al2O3 (c) CrC

Which of the following are the two main functions of a cutting fluid in machining (2 best answers)

(c) reduce friction at the tool-chip interface (d) remove heat from the process

Which of the following manufacturing processes are classified as material removal processes (2 correct answers)

(e) grinding (f) machining

Which statement/s is/are TRUE about weaknesses of optical microscopy techniques?

(probably wrong) Rarefraction of light through lenses can scatter light and reduce image quality AND Magnification is limited to light intensity

You are given a piece of brass that is cold worked 25% and currently has a cross sectional area of 0.04 in^2. Based on this information, you know the original cross sectioned area in square inches is:

0.053

Rank the following in ascending (lowest to highest) order of their hardness (and tensile strength): Bainite; Martensite; Tempered Martensite; Course Pearlite

1-Course pearlite; 2-Bainite; 3-Tempered Martensite; 4-Martensite

Plain carbon steels are designated in the AISI code system by which of the following?

10XX

What statements are TRUE for our casting lab?

??????????????????????????????

Brittle fracture is characterized by:

Abrupt (catastrophic) failure with little or no warning.

What process cannot be done by a lathe?

Adding a chamfer to the end of a square cross section bar of a workpiece

Which of the following processes can increase the yield strength of steel? Tempering; Hot working; Adding alloying elements; Quenching

Adding alloying elements and quenching

Which of the following will affect the hardenability of steel? Amount of alloying; Quenching medium; Cooling rate

All of the above

In general, which one of the following materials has the highest machinability: Aluminum; Cast iron; Copper; Low carbon steel; Stainless steel; Titanium alloys; Unhardened tool steel

Aluminum

What is the best way to measure specimen strain during a tensile test?

An extensometer OR determine it from cross head displacement and time measurements

At the back page Figure 1 for the TTT diagram, what line you need to follow for the heat treatment that will give you 50% pearlite, 50% martensite?

B

What are the safety concerns in the 361 lab?

Burns from hot equipment or samples; Damaged eyes from flying metal parts; Crushed fingers from equipment with "pinch" or "crush" zones; Cuts and abrasions from machining equipment

At below, what statement/s is/are true for Endurance Limit or Fatigue Limit?

Certain materials, primarily Body-Centered Cubic steels can have Endurance Limit or Fatigue Limit

During the metal cutting process, there is a self-excited vibration occur, which is called ____________.

Chatter

Which one of the following plate metals produces the hardest surface on a metallic substrate:

Chromium

What kind of bond is in the polymer backbone?

Covalent

Ductile fracture process does not involve:

Crack propagates through grains (transgranular fracture)

___________ is a phenomenon that having small voids during the plastic deformation on polymers which is perpendicular to uniaxial tensile stress direction

Crazing

Solid solutions have higher yield strength that corresponding pure metals because:

Dislocations are more difficult to move

The purpose of drilling a pilot hole is to....

Ease the drill bit into the work piece and prevent drill bit drift and slipping off-center

A stage of a process that relief some of the internal strain energy of a previously cold-worked metal is called recrystallization. (T/F)

FALSE

Activation energy is the energy which is required to initiate a reaction for recrystallization. (T/F)

FALSE

All crystalline metals become brittle at very low temperature (~10K). (T/F)

FALSE

Amorphous is a crystalline structure (T/F)

FALSE

It is OK to keep at least two indent diameter spacing between the hardness readings (T/F)

FALSE

Material properties are dependent on elemental composition only and not microstructure. (T/F)

FALSE

Weld failures always occur in the fusion zone of the weld joint, since this is the part of the joint that has been melted (T/F)

FALSE

Welding can only be performed on metals that have the same melting point; otherwise the metal with the lower melting temperature always melts while the other metal remains solid (T/F)

FALSE

You can have viscosity on thermosets if you increase the temperature (T/F)

FALSE

Which crystal structure is most likely not to exhibit ductile to brittle behavior as the temperature is lowered?

FCC

Bainite is a microstructure that consists of a-Ferrite and a fine dispersion of Cementite (T/F)

False

Cementite is a Body-Centered Cubic iron (T/F)

False

Decreasing the grain diameter increases the DBTT (T/F)

False

Eutectoid reaction is a reaction wherein, upon cooling, a liquid phase transforms isothermally and reversibly into two new solid phases that are intimately mixed. (T/F)

False

All of the following are true regarding to our machining lab, except........

Feed force is a thrust or radial force acting perpendicular to the machined surface.

What can NOT be obtained from tensile test data?

Fracture toughness

An increase in the carbon content of plain carbon steel generally does what to the DBTT?

Increases it

What is the result of "Rapid Quenched Steel" after Austenite?

Martensite

Which one of the following will have a highest hardness value? Annealed brass; Medium carbon steel austenized at 850 C and slow cooled; Medium carbon steel quenched and tempered at 400C; Medium carbon steel austenized and quenched in water; Impossible to tell

Medium carbon steel austenized and quenched in water

What should not affect the actual hardness of an alloy steel? Fractional amount of proeutectic and eutectic phases; Carbon level; Pealite colony size (width of finite Fe3C layers); Level of temper

None of the above bc all will affect hardness

Which of the following do you believe would characterize a hot-worked steel part in comparison to a cold-worked part? Higher Yield Strength; Better Surface Finish; Greater Hardness; Less Ductility

None of the above!

During your heat treatment lab, on the initial stage of the annealing process, there was a small increase on the hardness of your material. It was due to _________________.

Polyganization

The difference between the stress-strain behavior of a ductile metal and a thermoplastic polymer (T>Tg) is:

Polymers exhibit a "drawing" region and metals do not

The fatigue strength can be increased by:

Reducing stress concentration in structure design

During cold working, at certain value of thickness dimension reduction there was some degree of increase at the thickness after the rolling. That phenomenon is called ___________.

Springback

During the hardness test, minor load established reference depth and removes slack from machine. (T/F)

TRUE

Knurling is performed on a lathe, but it is not a metal cutting operation (T/F)

TRUE

There is a good correlation between Brinell hardness and tensile strength for steel (T/F)

TRUE

What statements are true about hardness numbers may correlate? Tensile strength; Wear resistance; Ductility; Young's Modulus

Tensile strength, wear resistance

What can you say about the mechanical properties of material A shown in the plot below? (number 34 in practice test)

The DBTT is around 10 to 20C

What statements are NOT true for Recrystallization?

The smaller the deformation, the lower the recrystallization temperature; The higher the temperature, the less time required for recrystallization

When you heated/soaked the bolts for the heat treatment of the steel lab, what was the purpose of the austenizing step?

To dissolve iron carbide (Fe3C)

For an alloy system displaying a eutectoid, an alloy for which the concentration of solute is less than the eutectoid composition is called Hypoeutectoid alloy (T/F)

True

When you do annealing, you increase the ductility and the electrical resistivity (T/F)

True

In a peritectic reaction, upon cooling

a solid phase and a liquid react to form a solid

Most sheet metalworking operations are performed as which one of the following:

cold working

The sample on the right failed from (its the cup neck thing question 75 on practice test)

ductile fracture under uniaxial tension

As an alloying ingredient in high-speed steel, tungsten (ie. W) serves which of the following functions? (2 answers)

forms hard carbides to resist abrasion AND increases hot hardness

Which of the following are advantages and characteristics of hot working relative to cold working (4 answers)

fracture of workpart is less likely; isotropic mechanical properties; lower deformation forces are required; more significant shape changes are possible

Of all of the current material addition rapid prototyping technologies, which one is the most widely used with hobbyist-level 3D Printers utilizing PLA or ABS filament:

fused deposition

In a sand-casting mold, the V/A ratio of the riser should be ________________ than the V/A ratio of the casting itself (volume to area ratio)

greater than

Thermal energy is normally associated with which of the following changes in an altered metallic layer (3 best answers)

hardness variations; heat affected zone; recrystallization

Work hardening is the result of:

increase in dislocation density upon deformation

Choose the structure of Polycarbonate

its the one with the two hexagons

Which are the most important criteria for the materials selection process of a beverage can? (2 answers)

loading conditions AND Corrosion resistance & reactivity with the beverage

The units for strain rate are:

m/m/s

Which one of the following manufacturing processes will likely result in the best surface finish?

machining

An outside micrometer would be appropriate for measuring which of the following (2 correct answers)

part length AND shaft diameter

An alloy has a composition of 60% B. The microstructure after slow cooling from liquid to room temperature can be described by

the one with full beta chunks and the a+B stripes (figure A)

The fracture surface morphology on the right represents (number 73 on the practice test)

transgranular fracture (maybe)

A 20cm long steel rod with a diameter of 20mm is loaded with a 5000N weight. If the diameter is reduced to 18mm under this load, determine the engineering strain.

use constant volume to find final length, then engr strain=(Lo-Lf)/Lo