MSE Exam 1 and 2
List three disadvantages of hot working (compared to cold working)
- bad surface conditions - expensive - tools do not last as long
List three advantages of hot working (compared to cold working)
- can form more intricate and complex designs - can help brittle materials be able to be formed - less energy required than cold working
Write any three-desired property of Mold material used for Injection Molding?
-able to retain heat well enough so it doesnt harden before it reaches the part but doesn't burn the polymers - the mold must not degrade quickly over time so it can be reused - must be a surface where polymers won't stick to it
Write the steps used to make titanium alloys from the ore of titanium. You do not need to write chemical reactions.
1. React TiO2 with Cl2 to make TiCl4 (g) 2. Condense TiCl4 (g) to TiCl4 (l) 3. React TiCl4 (l) with Mg (l) to form Ti (s) and MgCl2 4. Electrolysis of MgCl2 to separate them 5. Melt Ti with other alloys to make Ti (alloy)
For most metals: A. The strain hardening exponent decreases as temperature increases B. The strain hardening exponent is independent of temperature C. The strain hardening exponent increases as temperature increases
A
Martensite is obtained by: A. Rapid cooling (quenching) the austenite phase B. Slow cooling the austensite phase C. Annealing the ferrite phase at a temperature less than the eutectoid temperature
A
The ductility of a metal is measured by: A. Strain at failure B. Ultimate tensile strength C. Yield Strength
A
The predominant metals used in modern societies are: A. Ferrous Metals B. Non-ferrous metals C. Aluminum Alloys
A
Which of the following is a technique of Thermoforming that can be used to give the highest draw ratio? A. Match Die forming B. Drape forming C. Plug-assist forming D. Reverse Draw forming
B
Which of the following is associated with Extrusion Molding? A. Surging B. Shark skin C. Uneven thickness D. Rupture
B
Which of the following processes are associated with the production of plastic sheet film A. Thermoforming B. Blown film extrusion C. Blow molding
B
Which of the following type of die will you use for Blown Film Extrusion A. T-shaped slot dies B. Annular Die C. Spider Die
B
In Rotomolding if we produce an unfused product which of the following physical properties/ property are highly affected: A. Modulus of Elasticity B. Impact strength C. Tensile strength D. Elongation
B, D
Everything else being equal, the force required for warm working is: A. More than that for cold working B. Equal to that for cold working C. Less than that for cold working
C
For a metal rod subjected to compressive stresses: A. The true stress is more than the engineering stress B. The true stress is the same as the engineering stress C. The true stress is the less than as the engineering stress
C
For a steel of the eutectoid composition, as you cool thru the eutectoid temperature: A. One liquid phase transforms to a two solid phases B. One solid phase transforms to a liquid phase and a solid phase C. One solid phase transforms to two solid phases
C
In a binary system that exhibits a eutectic composition: A. The melting temperature at eutectic composition is more than the melting temperatures of the two pure elements B. The melting temperature at eutectic composition is between than the melting temperatures of the two pure elements C. The melting temperature at eutectic composition is lower than the melting temperatures of the two pure elements
C
Injection molding can be used for: A. Thermoplastic B. Thermoset C. Both a and b
C
Which of the following methods can be used to make a large trash can such that the product has thick corners? A. Extrusion molding B. Blow molding C. Rotomolding D. Injection molding
C
Which one property makes PET highly desirable to make soda bottles A. Crystallinity B. High Gas permeability C. Low Gas permeability D. Ductility
C
Which of the following(s) decreases with an increase in crystallinity of polymers. A. Density B. Tensile strength C. Impact toughness D. Transparency
C, D
What are the types of twin screw extruders? State one function of each type of twin screw extruder.
Corotating: better compounding/ mixing, and better thermal efficiency Counter rotating: more efficient pumping
How do we obtain Thermoforming processing window?
Heat thermoplastic film until it is pliable but doesn't fall apart then it can be used to thermoform. The window is at different times for different materials because when they become pliable is dependent on their crosslinking or lack there of
What are the types of Mold release agents used for Rotomolding?
Silicones, semi-permanent, permanent
Compared and contrast injection and extrusion molding.
Similar: machine costs Adv Extrusion: mixing, tool cost, more types of resins can be used Adv Injection: no uniform cross section, creates more complex shapes
If you cast a sphere and a cube of the same volume which will take more time to solidify? Why? Assume that both castings are from the same metal poured at the same temperature and the mold material is identical
Sphere would take longer because it has less surface area than a cube and for solidifying time volume is divided by area so more surface area the shorter the solidifying time
The four primary reactants in a blast furnace are air, CaCO3, and ______ and ______
carbon and Fe2O3
The chemical reaction which is associated with crosslinking is called ______.
curing
The geometries possible with injection molding is limited to ____________ dimensions.
three
Which method of thermoforming is used to form parts with hollow regions which may be foam filled _________.
twin sheet
The geometries possible with extrusion is limited to ____________ dimensions.
two
What is the importance (in terms of properties of final product) of having fully fused part in Rotomolding?
will not break easily, higher mechanical properties
Which of the following Thermoforming method is used to design products with high optical clarity, for example canopies of racing vehicles? A. Pressure forming B. Free forming C. Drape forming D. Match Die forming
B
Which of the following is a Thermoplastic Elastomer? A. Butadiene B. Styrene- Butadiene-Styrene C. Phenol-formaldehyde resins D. Polypropylene
B
Which of the following statements are true about thermosets? A. Thermosets initially soften at elevated temperatures for molding B. At higher temperatures thermosets undergo a chemical reaction that hardens the material C. Thermosets can be subjected to repeated heating and cooling cycles D. Thermosets can be shaped into a variety of products
A, B
Which of the following statements are true about thermoplastics? A. Thermoplastics are solid materials at room temperature B. Thermoplastics are viscous liquids at a few hundred degrees C. Thermoplastics cannot be subjected to repeated heating and cooling cycles D. Thermoplastics can be shaped into a variety of products
A, B, D
Which of the following applies to a highly crystalline polymer? A. High tensile strength B. Highly crosslinked C. High impact toughness D. High density
A, D
Which of the following are related to Injection molding? A. Reciprocating Screw B. Ejector Pins C. Spider Die D. Ram Injector
A, D
One of the most common alloy of titanium has _____ and _____.
Al and V
Due to strain on the extruder which polymer property improves? A. Thermal conductivity B. Tensile strength C. Resilience D. Chemical resistance
B
If you want to design tiger cub figurines which of the following methods would you use? A. Extrusion Molding B. Injection Molding C. Rotomolding
B
In plain carbon steel, as the carbon content increases: A. The elastic modulus increases B. The elastic modulus remains the same C. The elastic modulus decreases
B
In the list below, which metal has the highest density: A. Titanium B. Steel C. Aluminum
B
The shot sizes are higher, cost is low, and used to design larger products in Injection Molding. A. Reciprocating screw B. Ram extrusion
B
The significance of the biaxial rotation that is used in Rotomolding is related to: A. Provide centrifugal force so the material will stick to the walls B. Provide uniform heating C. Enable uniform coating on the mold
B
The use of a parison is associated with which one of the following plastic shaping processes: A. Injection molding B. Blow molding C. Rotomolding D. Thermoforming
B
The use of a parison is associated with which technique? A. Injection Molding B. Blow Molding C. Rotational Molding D. Thermoforming
B
What is die swell and what will be the steps you can take to reduce Die Swell?
Die Swell is when a polymer remembers its former shape so when it comes out of the die it reverts back to its former shape, also called viscoelasticity. To reduce the die swell: extrusion rate decreased or increase channel length pf the die
What are the advantages of Extrusion Blow Molding over Injection Blow Molding?
Extrusion blow molding is a faster cycle, wider choice of resins. Injection better transparencies
T or F: Addition of a plasticizer hardens the polymer and decreases flow.
False
T or F: Adiabatic heating in Extrusion process is due to the external heating elements
False
T or F: For metals, the yield stress decreases as the plastic strain increases.
False
T or F: In plain carbon steels, as the carbon content increases, the hardness decreases.
False
T or F: In steels, hardenability is defined as the maximum hardness that can be attained.
False
T or F: Sand casting is preferred over investment casting to make intricate shapes.
False
T or F: Thermoforming is good for highly crystalline polymers.
False
T or F: The main advantage of aluminum us that it can be used at higher temperatures (compared to other common metals)
False (low not high)
What are the steps in thermoforming, and state the advantages of using pressure forming over vacuum.
Thermoplastic film heated until pliable, then use vacuum or forced air to shape the film around the mold. Advantages of pressure less air bubbles, less warped, more control.
T or F: For the same metal and same amount of plastic deformation during processing, the yield strength of the cold rolled component is higher than that of the hot rolled component.
True
T or F: In Extrusion Blow Molding we have higher trim scrap compared to Injection Blow molding.
True
T or F: Metals are good conductors of heat.
True
T or F: The carbon content of cast iron is more than that of steel.
True
T or F: The distinguishing alloying element in stainless steel is chromium.
True
T or F: The specific strength of titanium alloys is higher than that of steel.
True
T or F: We can use direct flame heating for the Rock and Roll Rotomolding machine.
True
T or F: We will use a longer compression zone in the Extrusion process for a polymer resin with a high molecular weight distribution and amorphous in nature.
True
What polymer production process would you use to manufacture the following: a. Kayaks: B. Plastic soda bottles
a. Rotomolding 1. Load resin, heating cycle and rotating mold, cooling cycle and rotating mold, unloading the part b. Injection Blow molding 1. melt resin 2. Making the preform 3. heating the preform 4. blowing into the mold 5. cool and release
Thermoforming temperature of a amorphous polymer is ________ (above/below) the Glass Transition Temperature.
above
In addition to commercially pure (CP) titanium, the other two common alloys are ______ and ______.
alpha-beta and beta
What is the sequential change in the mechanical state of an amorphous polymer. A. Rubbery Solid, Glass, Viscous liquid B. Glass, Rubbery Solid, Viscous liquid C. Viscous liquid, Rubbery Solid, Glass
b
What is the role of cores in casting?
enables for parts to be hollow when casting
Two examples of bulk deformation processes are: _________ and ________
extrusion and rolling
What is the role of a riser in casting?
fill up cast during melting because shrinking occurs and risers contain liquid metal to help with shrinkage
In rotomolding _________ mold is used for heat sensitive resins to avoid direct heat.
jacketed
A low molecular weight polymer additive that enhances flexibility and workability is a __________.
plasticizer
The two types of alloys are _______ and ______.
solid solution and intermediate phase
In injection molding the channel that leads from the nozzle to the part is called the ____________.
sprue
Polymerization reaction in which oligonmers steadily increase in size and polymer average molecular weight increases as the reaction proceeds is ____________. (chain growth/ step growth polymerization)
step growth polymerization
Why is runner design important in Injection Molding?
streamline flow
