Chapter 5 and 6 quiz questions

Assuming all process/mold parameters are the same, ceramic molds have better melt fluidity the plaster molds. True False

False

Castings with small specific surface areas require shorter solidification times. (challenge question) True False

False

Expendable molds are more likely to result in isotropic material properties in the castings compared to permanent molds. True False

False

Expendable molds are used to make only one part (casting) per production cycle. True False

False

Investment casting process is most suitable for making large parts at high production volumes. True False

False

Laminar flow is more preferred over turbulent flow in metal casting since it is not associated with known casting defects. True False

False

Overall, continuous casting involves a simpler setup than conventional casting processes. True False

False

Slower cooling rates are more likely to result in isotropic structure. True False

False

Some metals will expand during solidification process due to excessive porosity in the castings process. True False

False

The maximum amount of shrinkage in metal casting occurs during liquid-to-solid phase transformation. True False

False

Unlike external chills, internal chills are more effective in reducing porosity due to turbulent melt flow. True False

False

Using fine sand grains in making sand molds reduces the potential for casting porosity. True False

False

Assuming all process/mold parameters are the same, plaster molds have better melt fluidity than metal molds. True False

True

Hot tearing defect in metal castings can be reduced by increasing the collapsability of sand molds. True False

True

Plaster molds offer better fluidity than shell molds for the same mold/cavity design. True False

True

Pure metals offer better fluidity than their alloys (under same casting conditions). True False

True

Wax patterns in expendable pattern casting process result in worse melt fluidity compared to conventional wood/metal patterns. True False

True

Which of the following statements is true for flat rolling? a. workpiece velocity decreases with increasing friction between the rolls and workpiece b. roll velocity decreases with increasing back tension c. angle of acceptence increases with rolling pressure d. roll velocity increases with increasing front tension e. None of the statements is true.

e. None of the statements is true.

Continuous casting is best performed with: a. Sand mold casting b. Investment casting c. Die casting d. Pressure casting e. None of the these

e. None of the these

Solidification time is a function of all of the following parameters, except: a. surface area of the casting b. size of the casting c. shape of the casting d. mold material e. casting fluidity

e. casting fluidity

The presence of workpiece inclusions is likely to result in one of these defects during deformation: a. cold-shuts in forging b. rolls flattening c. rolls deflection d. residual stresses in rolling e. center cracking in extrusion

e. center cracking in extrusion

The main concern (challenge) in using internal chills over external chills is: a. lower recyclability b. slower heat transfer c. higher microporosity d. higher cost e. effective bonding/fusion with the melt

e. effective bonding/fusion with the melt

The average flow stress in rolling processes increases with: a. increasing the roll radius b. applying front or back tension c. increasing rolling speed d. increasing friction e. increasing draft

e. increasing draft

The type of melt flow (laminar versus turbulent) during metal casting is influenced by the following, except: a. melt viscosity b. melt density c. melt pouring rate d. mold (cavity) geometry e. mold permeability

e. mold permeability

(Same Process in Previous Question) In a drawing process of an aluminum rod on a 80 hp drawing machine to a final diameter of 0.25 inch. Assuming perfectly plastic behavior with a yield strength of 40 kpsi, calculate: 3. Maximum drawing stress in psi

40,000 (with margin: 0)

In a drawing process of an aluminum rod on a 80 hp drawing machine to a final diameter of 0.25 inch. Assuming perfectly plastic behavior with a yield strength of 40 kpsi, calculate: 4. Energy per unit volume at maximum reduction in diameter

40,000 (with margin: 0)

(Same Process in Previous Question) In an open-die forging of a 2-in diameter cylindrical workpiece (K=30 kpsi, n=0.2) from an initial height of 4-inch to a final height of 2-inch, using a press with 100 hp capacity. 5. Calculate the forging time at maximum capacity in seconds.

Between 0.3 and 0.36

(Same Process in Previous Question) In a drawing process of an aluminum rod on a 80 hp drawing machine to a final diameter of 0.25 inch. Assuming perfectly plastic behavior with a yield strength of 40 kpsi, calculate: 2. Maximum initial diameter

Between 0.4 and 0.42

In an open-die forging of a 2-in diameter cylindrical workpiece (K=30 kpsi, n=0.2) from an initial height of 4-inch to a final height of 2-inch, using a press with 100 hp capacity. 1. Calculate the deformation strain.

Between 0.68 and 0.71

(Same Process in Previous Question) In a rolling operation of a 24-inch wide Aluminum plate (K=28,500 psi, n = 0.23) from an initial thickness (h0 = 1.5") to a final thickness (hf = 0.5") using a roll radius (R = 3") at N=100 rpm, and a coefficient of friction (μ = 0.4). 2. Calculate the deformation strain.

Between 1 and 1.2

In a rolling operation of a 24-inch wide Aluminum plate (K=28,500 psi, n = 0.23) from an initial thickness (h0 = 1.5") to a final thickness (hf = 0.5") using a roll radius (R = 3") at N=100 rpm, and a coefficient of friction (μ = 0.4). 4. Calculate the rolling force in lbf.

Between 1,000,000 and 1,200,000

(Same Process in Previous Question) In a drawing process of an aluminum rod on a 80 hp drawing machine to a final diameter of 0.25 inch. Assuming perfectly plastic behavior with a yield strength of 40 kpsi, calculate: 5. Drawing force at maximum reduction in diameter

Between 1,950 and 1,970

In a rolling operation of a 24-inch wide Aluminum plate (K=28,500 psi, n = 0.23) from an initial thickness (h0 = 1.5") to a final thickness (hf = 0.5") using a roll radius (R = 3") at N=100 rpm, and a coefficient of friction (μ = 0.4). 1. Calculate the roll gap in inches.

Between 1.7 and 1.75

(Same Process in Previous Question) In an open-die forging of a 2-in diameter cylindrical workpiece (K=30 kpsi, n=0.2) from an initial height of 4-inch to a final height of 2-inch, using a press with 100 hp capacity. 3. Calculate the average forging force in lbf.

Between 109,000 and 110,000

In a drawing process of an aluminum rod on a 80 hp drawing machine to a final diameter of 0.25 inch. Assuming perfectly plastic behavior with a yield strength of 40 kpsi, calculate: 1. Maximum drawing ratio

Between 2.7 and 2.75

(Same Process in Previous Question) In an open-die forging of a 2-in diameter cylindrical workpiece (K=30 kpsi, n=0.2) from an initial height of 4-inch to a final height of 2-inch, using a press with 100 hp capacity. 2. Calculate the average flow stress in psi.

Between 23,000 and 24,000

(Same Process in Previous Question) In a rolling operation of a 24-inch wide Aluminum plate (K=28,500 psi, n = 0.23) from an initial thickness (h0 = 1.5") to a final thickness (hf = 0.5") using a roll radius (R = 3") at N=100 rpm, and a coefficient of friction (μ = 0.4). 3. Calculate the average flow stress (assume no change in width) in psi.

Between 27,000 and 27,500

(Same Process in Previous Question) In a rolling operation of a 24-inch wide Aluminum plate (K=28,500 psi, n = 0.23) from an initial thickness (h0 = 1.5") to a final thickness (hf = 0.5") using a roll radius (R = 3") at N=100 rpm, and a coefficient of friction (μ = 0.4). 5. Calculate the total rolling power in HP.

Between 3,000 and 3,200

(Same Process in Previous Question) In an open-die forging of a 2-in diameter cylindrical workpiece (K=30 kpsi, n=0.2) from an initial height of 4-inch to a final height of 2-inch, using a press with 100 hp capacity. 4. Calculate the maximum forging velocity in inch/min.

Between 340 and 380

Ideally, when applying back tension in flat rolling, a. neutral point shifts down b. approach angle decreases c. rolling torque decreases d. rolling draft decreases e. None of the statements is true.

c. rolling torque decreases

Which of the following statements is FALSE in rolling process? a. Applying equal front and back tensions simultaneously lowers the location of the neutral point towards the center. b. The roll gap increases with increasing the draft. c. Slipping between the rolls and the workopiece in flat rolling process is the highest at the entry and exit points. d. Higher friction between the rolls and the workpiece allows for higher reduction in thickness (draft). e. Rolled threads have better corrosion resistance than machined threads.

a. Applying equal front and back tensions simultaneously lowers the location of the neutral point towards the center.

In flat rolling, which of the following statements is TRUE about the neutral point? a. None of the options is correct b. Rolling draft is the lowest at the neutral point c. Overall rolling power is the highest at the neutral point d. Roll velocity is the highest at the neutral point e. Workpiece velocity in the lowest at the neutral point

a. None of the options is correct

Which of the following statements is TRUE in rolling process? a. None of the statements is true. b. Cogging operation is preferred over flat rolling due to its higher speed. c. As friction increases in rolling process, the roll gap decreases. d. The workpiece velocity increases between the entry and the neutral point and then starts to decrease towards the exit point. e. Residual stresses in rolled parts are detrimental to the mechanical properties and surface finish.

a. None of the statements is true.

In flat rolling, edge cracks are usually associated with: a. Rolls deflection b. Rolls flattening c. Thermal cambering of the rolls d. Residual stresses e. Stretching of roll stand

a. Rolls deflection

An advantage of cold forming over hot forming: a. slower tool wear in cold forming b. lower tooling cost in cold forming c. All of the above d. higher production rate in cold forming e. lower forming energy in cold forming

a. slower tool wear in cold forming

Which of the following statements is FALSE in forging process? a. Flash in closed die forging results in good surface finish. b. Cold shut defect in closed die forging is mainly due to high porosity in the workpiece. c. Barreling defect in open-die forging is less likely under cold forming conditions. d. Barreling in open die forging is affected by the surface finish of the workpiece ends. e. Initial tooling cost is lower for hot working conditions than cold working conditions.

b. Cold shut defect in closed die forging is mainly due to high porosity in the workpiece.

Which of the following statements is TRUE in wire drawing process? a. None of the statements is true. b. Low carbon steel (K= 530MPa, n=0.26) has better drawability (i.e., maximum reduction in diameter) than 6061-T6 Aluminum (K=410 MPa, n=0.05). c. The average flow stress is corrected for plane strain condition by a factor of 1.15. d. The ideal force component can be reduced by modifying the die design. e. The reduction in diameter increases with increasing the die angle.

b. Low carbon steel (K= 530MPa, n=0.26) has better drawability (i.e., maximum reduction in diameter) than 6061-T6 Aluminum (K=410 MPa, n=0.05).

Which of the following expendable casting processes is only suitable for low melting point metals? a. Green sand mold casting b. Plaster mold casting c. Shell mold casting d. Slush casting e. Aluminum mold casting

b. Plaster mold casting

Hydrostatic extrusion is commonly used for: a. coaxial extrusion b. brittle materials c. ductile materials d. strain hardening materials e. perfectly plastic materials

b. brittle materials

Flash in closed die forging is often used for: a. high fluidity metals b. complex shapes c. soft metals d. simple shapes e. rigid-perfectly plastic metals

b. complex shapes

Fastest shrinkage in metal casting processes is most likely to occur during: a. cooling of the liquid melt b. liquid-to-solid transformation c. cooling of the solid to room temperature d. A and C e. B and C

b. liquid-to-solid transformation

In wire drawing, which of the following statements is true for a rigid-perfectly plastic material? a. Drawing force increases with increasing drawing speed b. Average flow stress increases with increasing drawing speed c. Average flow stress is constant d. Average flow stress increases with increasing strain hardening coefficient e. Average flow stress increases with increasing strain hardening coefficient

c. Average flow stress is constant

In closed die forging, flash can be desired since it: a. Improves workpiece ductility b. Multiple answers are correct c. Increases workpiece strength d. Improves tooling useful life e. Decreases forging force

c. Increases workpiece strength

The most suitable expendable mold casting process for making small parts at a large production volume is: a. Shell mold casting b. Sand mold casting c. Investment casting d. Expendable pattern (lost foam) e. Die casting

c. Investment casting

Chevron cracks in extrusion process can be reduced by: a. modifying the extrusion speed b. modifying the workpiece temperature c. Multiple options are correct d. modifying the extrusion ratio e. modifying the die design

c. Multiple options are correct

Slow cooling rate in metal casting results in: a. higher strength and hardness b. lower microporosity c. None of the options d. isortropic properties e. lower hot tearing

c. None of the options

In flat rolling, which pair of the following problems have opposite effects on the workpiece? a. Wavy edges and rolls flattening b. Thermal cambering and spreading c. Rolls deflection and rolls thermal cambering d. Rolls flattening and stretching of the roll stand e. Edge cracks and thermal cambering

c. Rolls deflection and rolls thermal cambering

The type of sand mold which combines high surface rigidity and good collapsability is: a. Skin-dried cold box sand molds b. Cold-box sand molds c. Skin-dried sand molds d. Green sand molds e. Baked sand molds

c. Skin-dried sand molds

Which of the following parameters improves melt fluidity? a. higher melt density b. higher freezing range c. higher mold temperature d. higher melt viscosity e. higher cooling rate

c. higher mold temperature

The main advantage of internal chills over external chills is _____________ in the troubled area. a. improving melt fluidity b. improving mold strength c. reducing mass of the melt d. None of the these e. increasing casting strength

c. reducing mass of the melt

The maximum ratio of diameters (D0/Df) for wire drawing of a perfectly plastic material is approximately: a. 0.36 b. 2.73 c. None of the above d. 1.64 e. 0.63

d. 1.64

Which of the following metals experiences expansion during solidification? a. Lead b. Low density Aluminum c. Brass d. Grey cast iron e. Zinc-Copper alloys

d. Grey cast iron

Which of the following expendable mold casting processes can be used with an external force to fill the mold? a. Die casting b. Pressure casting c. Squeeze casting d. Lost foam/wax patterns e. Investment casting

d. Lost foam/wax patterns

In flat rolling, increasing friction between rolls and workpiece results in: a. increased entry/exit pressure b. increased flash c. increased hot tearing d. None of the options e. increased spreading

d. None of the options

Plane strain conditions are often assumed in the case of: a. low strain wire drawing b. high strain wire drawing c. closed die forging d. None of the options is correct e. hydrostatic extrusion

d. None of the options is correct

Which of the following molds has the lowest permeability? a. Skin-dried sand molds b. Shell molds c. Green sand molds d. Plaster molds e. Baked sand molds

d. Plaster molds

The following metal casting processes use sand as a raw material to make the molds, except: a. Expendable pattern (lost foam) b. Vacuum casting c. Shell mold casting d. Slush casting e. Cold-box molds

d. Slush casting

In closed die forging, cold shut defect is mainly attributed to: a. Heat transfer b. High forces and energy c. Flash design d. Tooling design e. Pre-existing workpiece defects

d. Tooling design

Which of the following expendable mold casting processes produces low porosity castings with sharp corner details? a. Die casting b. Pressure casting c. Shell mold casting d. Vacuum casting e. Ceramic mold casting

d. Vacuum casting

Porosity due to trapped gas in metal castings can be reduced by: a. internal or external chills b. expendable molds c. internal chills d. pressure casting e. external chills

d. pressure casting

For a strain hardening materials (n=0.3), the maximum possible strain in a wire drawing process is: a. 0.73 b. 0.7 c. 1 d. 2.67 e. 1.3

e. 1.3

Which of the following sand molds offers the worst performance against hot tearing? a. Shell molds b. Green sand molds c. Skin-dried sand molds d. Cold-box sand molds e. Baked sand molds

e. Baked sand molds

Metal casting processes are often classified based on the following, except: a. Mold designs/structure b. Mold materials c. Mold filling mechanisms d. Processing setup e. Casting finish

e. Casting finish