ME 3243 midterm 2

Which of the following are the three basic types of static stresses to which a material can be subjected (three correct answers):

(a) compression (d) shear (e) tensile

Hooke's Law defines which one of the following regions of the stress strain relationship for engineering materials

(a) elastic region

Which one of the following materials has the highest hardness:

Alumina Ceeamic

If engineering stress and true stress were measured simultaneously during a tensile test, which would have the higher value: (a) engineering stress or (b) true stress?

True stress

The modulus of elasticity is also known as which one of the following: (a) elastic limit, (b) strain hardening exponent, (c) strength coefficient, or (d) Young's modulus?

Young's modulus

Hooke's Law defines which one of the following regions of the stress strain relationship for engineering materials: (a) elastic region, (b) plastic region, or (c) neither?

elastic region

Which one of the following materials has the highest modulus of elasticity

(b) diamond

The plastic region of the stress-strain curve for a metal is characterized by a proportional relationship between stress and strain

(b) false

Which one of the following types of stress strain relationship best describes the behavior of brittle materials such as ceramics and thermosetting plastics

(c) perfectly elastic

Which one of the following is the correct definition of ultimate tensile strength, as derived from the results of a tensile test on a metal specimen:

(c) the maximum load divided by the original area of the specimen

The modulus of elasticity is also known as which one of the following

(d) Young's modulus

The flow curve describes the property of metals known as which one of the following:

(d) strain hardening

Depicted below are five different steady-state concentration profiles for the same gas across five separate and identical plastic membranes at the same temperature. Which concentration profile results in the highest diffusion flux through the membrane? (a) (b) (c) (d) (e)

(e)

Depicted below are five different steady-state concentration profiles for the same gas across five separate and identical plastic membranes at the same temperature. Which concentration profile results in the lowest diffusion flux through the membrane? (a) (b) (c) (d) (e)

(e)

As temperature decreases, the fraction of the total number of atoms that are capable of diffusion motion A. Decreases B. Increases

A. Decreases

As temperature decreases, the fraction of the total number of atoms that are capable of diffusive motion A. Decreases B. Increases

A. Decreases

The figure below features diffusion profiles that developed within four separate plain-carbon steel specimens of equivalent geometry after they separately experienced a carburization process. The specimens were prepared such that the scenario of a one-dimensional semi-infinite solid applies as a solution to Fick's 2nd Law of Diffusion. Each part originally contained a uniform distribution of carbon, and each part was processed using the same carburization time. In the figure, corresponds to the surfaces of the steel parts that were exposed to the carbon-rich atmosphere during the diffusion process. Answer True or False for each of the following statements. (a) The carburization surface was maintained at slightly less than 0.25 wt% carbon for each specimen. True or False (b) Comparing the finished specimens at a depth of 0.20 mm, specimen A features the lowest carbon concentration. True or False (c) Comparing the finished specimens as a whole, specimen D features the lowest overall amount of carbon. True or False (d) Specimen B experienced a higher carburization temperature compared to specimen A. True or False (e) The initial concentration of carbon in each part (prior to carburization) was approximately 1.00 wt% carbon. True or False

A. False B. True C. False D. True E. False

A low activation energy indicates easy diffusion. A. True B. False

A. True

Activation energy for interstitial diffusion is low and rate of diffusion is fast. A. True B. False

A. True

The figure below features diffusion profiles that developed within four separate plain-carbon steel specimens of equivalent geometry after they separately experienced a carburization process. The specimens were prepared such that the scenario of a one-dimensional semi-infinite solid applies as a solution to Fick's 2nd Law of Diffusion. Each part originally contained a uniform distribution of carbon, and each part was processed using the same carburization temperature. In the figure, corresponds to the surfaces of the steel parts that were exposed to the carbon-rich atmosphere during the diffusion process. Answer True or False for each of the following statements. (a) The carburization surface was maintained at 1.00 wt% carbon for each specimen. True or false (b) Comparing the finished specimens at a depth of 0.75 mm, specimen A features the largest carbon concentration. True or false (c) Comparing the finished specimens as a whole, specimen A features the lowest overall amount of carbon. True or false (d) Specimen B experienced a longer carburization time compared to specimen C. True or false (e) The initial concentration of carbon in each part (prior to carburization) was a little less than 0.25 wt% carbon. True or false

A. True B. False C. True D. False E. True

Hooke's Law defines which one of the following regions of the stress strain relationship for engineering materials. A.Elastic region B.Plastic region, or C.Neither

A.Elastic region

Which one of the following materials has the highest hardness: (a) alumina ceramic, (b) gray cast iron, (c) hardened tool steel, (d) high carbon steel, or (e) polystyrene?

Alumina ceramic

Concentration gradient refers to: A. Change of concentration with respect to time B. Change of concentration with respect to space C. Change of concentration with respect to temperature D. None of the mentioned

B. Change of concentration with respect to space

Diffusion by which mechanism occurs more rapidly in metal alloys? A. Vacancy diffusion B. Interstitial diffusion

B. Interstitial diffusion

The material with the highest elastic modulus is A.Steel B.Diamond C.Tungsten D.Platinum E Gold

B.Diamond

Which of the following are the three basic types of static stresses to which a material can be subjected: (a) compression, (b) hardness, (c) reduction in area, (d) shear, (e) tensile, (f) true stress, and (f) yield?

Compression, tensile, shear

Which one of the following materials has the highest modulus of elasticity: (a) aluminum, (b) diamond, (c) steel, (d) titanium, or (e) tungsten?

Diamond

Which one of the following types of stress strain relationship best describes the behavior of metals at temperatures above their respective recrystallization points: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above?

Elastic and perfectly plastic

Which one of the following types of stress strain relationship best describes the behavior of most metals at room temperature: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above?

Elastic and strain hardening

If engineering strain and true strain were measured simultaneously during a tensile test, which would have the higher value

Engineering strain

If engineering strain and true strain were measured simultaneously during a tensile test, which would have the higher value: (a) engineering strain or (b) true strain?

Engineering strain

Viscosity can be defined as the ease with which a fluid flows

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 It is the elastic region that is characterized by a proportional relationship between stress and strain. The plastic region is characterized by a power function - the flow curve

Viscosity can be defined as the ease with which a fluid flows: (a) true or (b) false?

False Viscosity can be defined as the resistance with which a fluid flows:

A Newtonian fluid is a fluid best defined by which one of the following: (a) its viscosity decreases as shear rate increases, (b) its viscosity decreases as temperature increases, (c) its viscosity increases as shear rate increases, (d) its viscosity increases as temperature increases, (e) its viscosity remains constant as shear rate changes, or (f) its viscosity remains constant as temperature changes?

Its viscosity remains constant as shear rate changes.

The shear strength of a metal is usually (a) greater than or (b) less than its tensile strength?

Less than it's tensile strength S=0.7(TS)

The shear strength of a metal is usually

Less than its tensile strength

The transverse rupture strength is a property usually associated with which one of the following material types

Metals

The transverse rupture strength is a property usually associated with which one of the following material types: (a) ceramics, (b) metals, (c) plastics, or (d) rubber?

Metals*

Which one of the following types of stress strain relationship best describes the behavior of brittle materials such as ceramics and thermosetting plastics: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above?

Perfectly elastic

The formation of new strain-free grains in a metal that has been heated to an elevated temperature is called which one of the following:

Recrystallization

The formation of new strain-free grains in a metal that has been heated to an elevated temperature is called which one of the following: (a) hot hardness, (b) recrystallization, (c) strain hardening, or (d) strain softening?

Recrystallization*

Hardness is best defined as which one of the following

Resistance to permanent indentation

Hardness is best defined as which one of the following: (a) energy absorbed by a material when an object strikes its surface, (b) resistance to bending, (c) resistance to permanent indentation, or (d) resistance to scratching?

Resistance to permanent indentation

The flow curve describes the property of metals known as which one of the following: (a) ductility, (b) engineering strain, (c) fracture stress, (d) strain hardening, or (e) tensile strength?

Strain hardening

Which one of the following is the correct definition of ultimate tensile strength, as derived from the results of a tensile test on a metal specimen: (a) the stress encountered when the stress-strain curve transforms from elastic to plastic behavior, (b) the maximum load divided by the final area of the specimen, (c) the maximum load divided by the original area of the specimen, or (d) the stress observed when the specimen finally fails?

The maximum load divided by the original area of the specimen

The shear strength of a metal is commonly determined in which one of the following tests:

Torsion Test

Most hardness tests involve pressing a hard object into the surface of a test specimen and measuring the resulting indentation or its effect:

True

Viscoelasticity can be defined as the property of a material that determines the strain it experiences when subjected to combinations of stress and temperature over time:

True

Most hardness tests involve pressing a hard object into the surface of a test specimen and measuring the resulting indentation or its effect: (a) true or (b) false?

True Most hardness tests involve pressing a hard object into the surface of a test specimen and measuring the resulting indentation or its effect.

Viscoelasticity can be defined as the property of a material that determines the strain it experiences when subjected to combinations of stress and temperature over time: (a) true or (b) false?

True Viscoelasticity can be defined as the property of a material that determines the strain it experiences when subjected to combinations of stress and temperature over time.

If engineering stress and true stress were measured simultaneously during a tensile test, which would have the higher value

True streas

Which one of the following types of stress strain relationship best describes the behavior of metals at temperatures above their respective recrystallization points

elastic and perfectly plastic

Which one of the following types of stress strain relationship best describes the behavior of most metals at room temperature

elastic and strain hardening

A Newtonian fluid is a fluid best defined by which one of the following:

its viscosity remains constant as shear rate changes

The shear strength of a metal is commonly determined in which one of the following tests: (a) bending test, (b) compression test, (c) flexure test, (d) tensile test, or (e) torsion test?

torsion test thin-walled tubular specimen is subjected to a torque. As torque is increased, the tube deflects by twisting, which is a shear strain for this geometry.