mse practice q
t/f: In ductile metals, the Yield Stress is always higher than the Ultimate Tensile Stress
false, for ductile they are the same
How does the change in cross-sectional area of a test specimen in a compression test differfrom its counterpart in a tensile test specimen?
In a compression test, the specimen cross sectional area increases as the test progresses; while in a tensile test, the cross sectional area decreases
Which one of the following prototyping technologies uses solid sheet stock as the starting material:
LOM
With the use of a convex-shaped positive mold, a. Thermoformed part is designed with a thick base and thin periphery b. Thermoformed part is designed with a thin base with thick periphery
a
Select which of the following applies to rotomolded parts. a. Rotational molding can create parts with high precision in dimension. b. Rotational molding cannot create parts with high precision in dimension. c. Rotational molding cannot design hollow parts. d. Rotational molding is only used to design large parts which exceed a capacity of 100 gallons
b
Select the characteristics you will require in the resin you would use in roto molding (Circle all that applies) a. Low MFI b. High MFI c. High Fusibility d. Low Fusibility e. High Molecular weight f. Low Molecular weight g. Amorphous resin h. Semi-crystalline resin
b, c, f, h
An elastomer cannot be used in which of the following processing techniques, Extrusion molding Injection molding Blow molding
blow
Use of a parison is associated with which plastic shaping processes?
blow molding
Which of the following processes would be applicable to produce hulls for small boats (threebest answers)
blow molding, rotational, vacuum thermoforming
A thermoforming mold with a convex form is called which one of the following: (a) a die,(b) a negative mold, (c) a positive mold, or (d) a three-plate mold?
c
Which of the following processing technique you would use to design a basketball, a. Thermoforming b. Injection molding c. Rotomolding d. Foaming
c
The term encapsulation refers to which one of the following plastics shaping processes
casting
Which of the following is a processing method used widely to encapsulate electronics inside plastic containers?
casting
To design a foamed part with less dense foam and lighter you will ____________(increase/ decrease) the amount of foaming agent.
decrease
A very important parameter while thermoforming,
draw ratio
Which one of the following types of stress strain relationship best describes the behavior of metals at room temperature
elastic and strain hardening
The main difference between extrusion blow molding and injection blow molding is:
existence of preform
Significant disdvantages of thermoforming,
expensive starting material large amount of scrap
blow ratio is higher in a. extrusion BM b. injection BM
extrusion
While designing playground equipment using rotational molding, you would prefer to use apolymer resin with low MFI (True/False)
false
t/f: In Stereolithography there is use of UV light to sinter the powered resin.
false
t/f: In order to get the plastic powder to stick to the sides of the mold it is important to mix in adhesive additives into the powder before processing.
false
t/f: In rotational molding, centrifugal force is used to force the polymer melt against the surfaces of the mold cavity where solidification occurs:
false
The plastic region of the stress-strain curve for a metal is characterized by a proportional relationship between stress and strain: (a) true or (b) false?
false, elastic region uses this
n casting, there is the use of only thermoplastics for the encapsulation of electrical wires,(True/False)
false, thermoplastic or thermoset
Processing technique which was used to design light weight parts like seat cushions
foaming
For larger parts designed in blow molding, we need _______blow ratio
higher
in which of the following properties do plastic parts often compare favorably with metals
impact resistance, strength-to-weight ratio
With increase in temperature, ductility of the metal __________ (
increase
With increase in plastic strain, yield strength will _________ (increase/decrease).
increase, due to strain hardening
Most hardness tests involve pressing a hard object into the surface of a test specimen andmeasuring the __________ (or its effect) that results
indentation
What is strain hardening?
is the strengthening of a metal or polymer by plastic deformation.
What is the starting material for fused deposition modeling?
long filament of polymer or wax
Can you thermoform a thermoset sheet ?
no
Can you thermoform an extruded sheet of Nylon with high percent crystallinity?
no
Which of the following is NOT an example of a part that is thermoformed Clam shell food containers Plastic fork and plastic eating utensils Trash can Truck bed liner
plastic fork and plastic eating utensils
The two most common polymer foams are which of the following
polyurethane, polystyrene
in thermoforming a part with higher draw ratio you would use a. Straight vacuum thermoforming b. Pressure thermoforming c. Mechanical thermoforming
pressure thermoforming
Which processing technique used photosensitive liquid polymer as starting material?
stereolithography
Matched die forming is related to
thermoforming
Which of the following processing technique uses sheet or film as the starting material
thermoforming
Both flexible and rigid foams can be open celled or closed cell (True/ False)
true
If strain measurements were made during a tensile test, ______ will have highervalue: (a) engineering strain, or (b) true strain
true strain < eng strain
If stress values were measured during a tensile test, which of the following would have thehigher value: (a) engineering stress or (b) true stress?
true stress > eng stress
In what case does the strength coefficient have the same value as the yield strength?
when n =0 (perfectly plastic)
Tensile testing is not appropriate for hard brittle materials such as ceramics. What is the testcommonly used to determine the strength properties of such materials?
- bending test/flexing test - specimen is placed between 2 supports and a load is applied at its center
What is the difference between engineering stress and true stress?
Engineering stress divides the load (force) on the test specimen by the original area; whiletrue stress divides the load by the instantaneous area, which decreases as the specimen stretches.
State Hooke's Law.
For a stress-strain relationship there are two regions 'elastic and plastic'. Stress and strain is linear for elastic region.Therefore strain(e) is proportional to stress(s) by a multiple of the modulus of elasticity. s=Ee
What is the correct definition of ultimate tensile strength, as derived from the results of a tensile test on a metal specimen:
The maximum load divided by the original area of the specimen.