MEEM3600 Quizzes

The ASTM grain size number n is a measure of the grain size in polycrystalline materials. A grain size of n=7 generally is acceptable for sheet metals used to make car bodies. n=7 corresponds to ______ grains/mm^2

1024

What is the extrusion ratio if a metal billet 200 mm in diameter is extruded to a diameter of 50 mm:

16

What is the cutoff wavelength of a surface specified by the following symbol?

200

Two strain hardening specimens are tested with tension tests, and the logarithmic true stress-strain curves are plotted as shown. Which material has higher strain hardening coefficient 𝑛?

A

Which of the following friction mechanism involves material transfer (diffusion) from on surface to another?

Adhesion

Which of the following friction mechanism involves material transfer (diffusion) from one surface to another?

Adhesion

Which of the following metals would typically be used in die casting?

Aluminum, tin, zinc

In powder metallurgy, which of the following powder production methods requires melting the metal into liquid form:

Atomization

For strain hardening material, the work of deformation in ideal upsetting (no friction) depends on (refer to the work estimation equation)

Average Flow Stress

In the above plot, which material has a higher strength coefficient K?

B

Which of the following test is commonly used for brittle materials?

Bending test

Which of the following are advantages of die casting over sand casting?

Better surface finish, closer tolerances, higher production rates, mold can be reused.

Which of the following lubricating regimes has the highest friction:

Boundary

Which of the following lubricating regimes has the highest friction?

Boundary

Shell molding is best described by which one of the following:

Casting process in which the mold is a thin shell of sand bonded by a thermosetting resin

Aluminum foil is produced by rolling of aluminum sheet. During this process, what manufacturing parameters would you prefer:

Cold working, small diameter roll

Of the following abrasive materials, which one has the highest hardness:

Cubic Boron Nitride

According to the empirical equation ϕ=45∘+α/2−β/2, an increase in rake angle would have which of the following results, if all other factors remaining the same (two best answers):

Decrease in power requirements. Increase in shear plane angle.

Which of the following casting processes is permanent-mold operation?

Die Casting

Which factors affect chevron cracking in extrusion?

Die angle, Friction, and Extrusion ratio

Compared with hot-worked parts, cold worked parts generally have a rougher surface finish.

False

During the solidification process, the largest density change and volume shrinkage occur during phase change of a material from liquid to solid

False

Hardness is related to strength and wear resistance, so it is one of the fundamental properties of a material.

False

Hot Isostatic Pressing (HIP) is suitable for making parts with complex geometries.

False

If we monitor the temperature rise in the machining process, the highest temperature usually occurs at the tool tip

False

In a 90 degree bending operation, a material with higher Youngs Modulus will spring back more than one with lower modulus.

False

In a rolling process, to the left of the neutral point, the workpiece moves faster than the roll surface. (Assume the workpiece moves from left to right)

False

In indirect extrusion, the die moves along the same direction as the metal flow.

False

In rolling process, front tension shifts the neutral point towards the exit

False

Materials with bcc crystal structures are generally more brittle than those with hcp crystal structures.

False

Residual stresses are those which remain in a part after it has been deformed and all external forces have been removed. Therefore, residual stresses are always undesirable.

False

The arithmetic mean value Ra is a complete description of the surface roughness.

False

The arithmetic mean value Ra is the complete description of the surface roughness.

False

The coefficient of friction u is a material property.

False

The coefficient of friction u is material property.

False

The elastic constants are sensitive to crystal lattice defects.

False

The root-mean-square average Rq is a complete description of the surface roughness.

False

The root-mean-square average Rq is the complete description of the surface roughness.

False

When measuring the surface roughness with styles profilometers, a 2um radius stylus will always reports the same roughness values as a 20um stylus.

False

When measuring the surface roughness with stylus profilometers, a 2um radius stylus will always report the same roughness value as a 20um stylus.

False

When punching out a sheet metal part, the shearing force is proportional to the parts area

False

You are given the K and n values of two different materials. This information is sufficient to determine with material is tougher?

False

Which of the following bulk deformation processes is usually used to manufacture discrete parts:

Forging

The size distribution of particles in PM is important. It can be characterized by cumulative distribution. In the figure shown, which curve represents powders with more uniform particle size distribution?

Green Curve

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

Grinding and Machining

Which of the following is NOT a fundamental mechanical property of a material

Hardness

For bulk deformation processes, the coefficient of friction is determined experimentally by the ring compression test. High coefficient of friction is indicated by

High Reduction in inner diameter

In order to absorb as much energy as possible during an impact, we need to choose a suitable material for the frame of a truck. The preferred mechanical property of the material is

High Toughness

Choose the desirable mechanical properties for a staple

High ductility and Low yield stress

Choose the desirable mechanical properties for an elevator cable.

High elastic modulus and high yield stress

For bulk deformation processes, the coefficient of friction is determined experimentally by the ring compression test. High coefficient of friction is indicated by

High reduction in inner diameter

High extrusion rate requires

Higher extrusion force

Which of the following processes increase the ductility in the work piece?

Hot Work

Which test is typically useful for determining the forgeability of steels?

Hot-Twist test

Which of the following forging instruments has the lowest operation rate?

Hydraulic presses

Which of the following processes will you suggest to produce a deep cup with a relatively brittle material:

Impact Extrusion

When it is subjected to a state of uniaxial tension stress and in the elastic range, the volume of a metal specimen (given Poisson's ratio v=0.3) will

Increase

The die angle has an important effect on forces in extrusion. Increase die angle will

Increase the redundant deformation

LEGO blocks are made with Acrylonitrile Butadiene Styrene (ABS) which is an engineered thermoplastic. What process would you choose to manufacture the LEGO blocks?

Injection Molding

In injection molding, ejection pins are used to push the plastic products out of the die cavity. The ejection pins usually leave ejection pin marks on the ______ surface of the product.

Inner Surface

When a wire is drawn through a die, its cross-section is decreased. What do you think about its yield strength?

It will increase.

Which one of the following is the best definition of bend allowance

Length before bending of the straight sheet metal section to be bent

The figure shows the elimination of residual stresses by further stretching. Would it be possible to eliminate residual stresses by further compression instead? Assume that the piece of material is elastic-perfect plastic, and will not buckle under the uniaxial compressive force.

Possible

In rolling process, the roll force depends on

Roll radius, average flow stress, average thickness of the workpiece, change in thickness of the workpiece

Friction can be reduced by

Selecting materials that exhibit low adhesion, using lubricants, coating the surface in contact.

Friction can be reduced by

Selecting materials that exhibit low adhesion, using lubricants, coating the surfaces in contact.

If a workpiece is measured 5 mm in thickness, it is considered as __________ in manufacturing processes?

Sheet

A screw extruder is used to extrude thermoplastic into a bar with circular cross-section. The designed bar diameter is 20 mm. What should be the diameter of the die?

Smaller than 20mm

Shape factor (SF) is a measure of the ratio of the surface area of the particle to its volume-normalized by reference to a spherical particle of equivalent volume. SF=(A/V)Deq In which A is the surface area, V is the volume, Deq is the diameter of a spherical particle that has the same volume as the particle being considered. Which of the following shapes has the lowest value of shape factor?

Spherical Particle

Friction is not a material property, it is a system property that involves

Surface Roughness, Lubricant, Environment, Temperature, Sliding Speed.

Friction is not a material property, it is a system property that involve:

Surface roughness, Lubricant, Environment, Temperature, Sliding Speed

In upsetting, barreling can occure due to inhomogeneous deformation of the workpiece, the possible reasons are

Temperature difference between the workpiece and die surfaces, Friction between workpiece an die surfaces

Aluminum and magnesium alloys are suitable for precision forging, because

The forging loads and temperature required are relatively low, die wear is low, good surface finish.

If you pull and break a tension-test specimen rapidly, where would the temperature be the highest?

The neck region.

The elastic modulus of several materials is plotted in the following bar chart. Which of the following comments can be addressed?

Thermoplastics, thermosets and rubbers are orders of magnitude lower than metals and other non-metals

Which type of plastic products can not be reshaped/reformed by heating?

Thermoset

A slip plane containing a dislocation requires low shear stress to cause slip, comparing to a slip plane with a perfect lattice.

True

Due to oxidation, the hardness of a metal surface is generally higher that the bulk.

True

Due to oxidation, the hardness of the metal surface is generally higher than the bulk.

True

During the sintering stage, the volume of the green compact will shrink if the sintering mechanism is dominated by solid-phase material transport.

True

Extrusion pressure decreases with extrusion speed.

True

For the same amount of deformation, the friction force in direct extrusion is usually much larger than indirect extrusion.

True

Generally, high strain rate increases a materials strength.

True

Grinding force increases with the increasing depth of cut

True

Hot working can help to reduce the residual stress within the workpiece.

True

In a tensile test, true stress would have a higher value than the engineering stress.

True

In drawing process, the residual stresses on the surface of a workpiece is compressive when the drawing ratio is small.

True

In manufacturing processes such as forging and extrusion, the normal force on the interface between the workpiece an dies is huge, so the friction is no longer proportional to the normal force.

True

In rolling process, compressive residual stresses on the surface of the workpiece can be produced by small rolls and/or small reduction in height.

True

In the rolling process, larger radius roll is preferred for large thickness reduction.

True

One reason to the extensive application of cutting fluids in machining operations is that they can reduce forces and energy consumption.

True

Plastic products are usually designed with uniform thickness in order to achieve uniform solidification.

True

Properties measured by compression tests are subjected to inaccuracy because of barreling due to the presence of friction.

True

Properties measured by compression tests are subjected to inaccuracy due to barreling which is caused by friction.

True

The higher the compacting pressure, the closer the density of the green compact to the density of the bulk material.

True

The surface of a part may considerably different properties compares to its interior.

True

The surface of a part may have considerably different properties compares to its interior.

True

The temperature rise in a grinding process is generally higher than that in a metal cutting process.

True

The tensile strength of the compact part increases with the density of the compact.

True

For 90∘ bending of sheet metal, which operation is preferred?

Wiping die bending

Mechanical properties measured by tension test include

Yield stress, Poisson's ratio, elastic modulus, UTS, Ductility

Extrusion and Drawing are similar in terms of

both are continuous processes

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

cold working

Which one of the four types of chip would be expected in a turning operation conducted at low cutting speed on a brittle work material

discontinuous

Which of the following crystal structures will generally be more brittle?

hcp

The cutting force in a sheet-metal blanking operation depends on which mechanical property of the metal

modulus of elasticity

The two basic mechanisms by which plastic deformation may take place in crystal structures are

slip and twinning

The two basic mechanisms by which plastic deformation may take place in crystal structures are:

slip and twinning

Which of the following material properties is sensitive to crystal lattice defects:

yield strength