445 Midterm
The flow curve describes the property of metals known as strain hardening.
Which of the following types of stress-strain relationship best describes the behavior of most metals at room temperature? elastic and perfectly plastic elastic and strain hardening perfectly elastic none of the above
Engineering stress in the plastic region will be greater in which of the following tests? compression test tensile test torsion test
An inside micrometer is used to measure inside dimensions of a part. A depth micrometer is used to measure the depths of holes.
In the measurement of surface roughness, the cutoff length is defined as a filter that separates waviness from roughness deviations.
A problem with the Ra computation is that waviness may get included. To deal with this, a parameter called the cutoff length is used as a filter to separate waviness from roughness deviations.
Three basic types of static stress to which a material can be subjected: Compression, shear, tensile
The strength coefficient and strain hardening exponent measured in a tensile test for a given metal are nearly identical to those measured in a compression test.
Precision is the degree of repeatability in the measurement process.
Measurement instruments are considered to be graduated measuring devices: slide caliper, vernier caliper, steel rule
A mold shift refers to a defect in sand casting caused by a sidewise displacement of the core inside the casting before it solidifies. False
Which of the following are some of the factors that affect the fluidity of a molten metal during pouring into a mold cavity? pouring temperature above the melting point, metal alloy composition, viscosity of the liquid metal, heat transfer to the surroundings
What is the limitation of permanent mold casting processes that does not apply to expendable mold casting processes? the need to open the mold to retrieve the part
What properties determine the quality of a sand mold for sand casting? Strength, permeability, thermal stability, collapsibility, reusability
Investment casting has which two of the following advantages compared to most other casting processes: close dimensional control, parts of great complexity can be cast
Which two of the following casting processes are expendable mold operations? investment casting, sand casting
Wheels and pulleys are examples of castings that are made by semicentrifugal casting.
Which two of the following casting processes are permanent mold operations? centrifugal casting, slush casting
Which one of the following expendable mold processes is known as a precision-casting process? investment casting
As the temperature increases, the strain rate sensitivity exponent of a material decreases. False.
Lubricants used in hot working are the same as those used in cold working. False
Strain rate sensitivity is greatest under hot working.
Sticking friction is when the work surface adheres to the surface of the tool rather than slides against it; it occurs when the friction stress is greater than the shear flow stress of the metal. It is generally associated with hot working.
The applied force in an extrusion operation is based on average flow stress.
The dividing line between warm working and cold working is usually taken to be which one of the following temperatures relative to the melting point of the given metal, where T = the melting temperature on an absolute temperature scale? 0.3Tm
Near net shape and net shape processes are ones in which little or no additional machining is required to complete the part. Since cold working provides good surface finish and tolerances, it is a near net shape or net shape process.
The no-slip point, also known as the neutral point, in a rolling operation is the point along the contact arc where work velocity equals roll velocity.
Which of the following are/is help(s) in reducing the force in at rolling? use hot rolling, reduce draft in each pass, use smaller diameter rolls
Advantages of thread rolling over thread cutting (machining): higher production rates, better material utilization, stronger threads due to work hardening, smoother surfaces better fatigue resistance due to compressive stresses introduced by rolling
Average flow stress is used in the computation of rolling force?
The maximum possible draft in a rolling operation depends on the coefficient of friction between roll and work, roll diameter
A specialized hot working process for making seamless thick-walled tubes using two opposing rolls is called roll piercing.
The significantly higher forces in impression-die forging compared to open-die forging are caused by flash formation and more complex part shapes.
The shape factor in extrusion is defined as the ratio of the pressure required to extrude a cross section of a given shape relative to the extrusion pressure for a round cross section of the same area.
An internal crack that develops as a result of tensile stresses along the centerline of the work part during extrusion is called centerburst.
In a direct extrusion operation, the portion of the billet that remains in the container and cannot be forced through the die opening is called butt.
Which cross-sectional shape would require the greater extrusion pressure? a) round circle, or b) a round tube shape with the same cross-sectional area? a round tube shape with the same cross-sectional area
