Worksheet: Stress and Strain: Material Properties

In this worksheet, we will practice describing the properties of solid materials and the ways that they affect how objects respond to applied stresses.

Q1:

What is a critical crack length most associated with?

  • Ahigh ductility
  • Bnon-protective oxide films
  • Cplastic yielding
  • Dfast fracture
  • Ecreep permanent strain

Q2:

What is the behavior of secondary creep?

  • ASecondary creep exhibits a decreasing strain rate.
  • BSecondary creep exhibits an increasing strain rate followed by material failure.
  • CSecondary creep exhibits a constant strain rate.
  • DSecondary creep is an incubation period in which little strain occurs.
  • ESecondary creep exhibits an exponentially increasing strain rate with time.

Q3:

How do brittle materials differ from ductile materials?

  • ABrittle materials have a higher ultimate tensile strength than ductile materials.
  • BBrittle materials fail more suddenly under stress; ductile materials yield before fracture.
  • CDuctile materials have a lower yield stress than brittle materials.
  • DBrittle materials have a lower modulus of elasticity than ductile materials.
  • EDuctile materials fail more suddenly under stress; brittle materials yield before fracture.

Q4:

How do yield and fracture processes generally vary with temperature?

  • ABoth yield and fracture become more likely at higher temperatures.
  • BBoth responses have unpredictable variations with temperature.
  • CFracture becomes more likely at lower temperatures, and yield becomes more likely at higher temperatures.
  • DBoth yield and fracture become more likely at lower temperatures.
  • EYield becomes more likely at lower temperatures, and fracture becomes more likely at higher temperatures.

Q5:

How does creep vary with temperature?

  • AIt increases exponentially with increasing temperature.
  • BIt increases linearly with increasing temperature.
  • CIt increases with the square root of temperature.
  • DIt increases with the fourth power of temperature.
  • EIt increases with the reciprocal of temperature.

Q6:

How do the processes leading to fracture differ from those causing yield?

  • AFracture results from steady stress, and yield results from time-varying stress.
  • BFracture depends more upon shear stresses, and yield depends more upon normal stresses.
  • CYield depends more upon shear stresses, and fracture depends more upon normal stresses.
  • DFracture depends more upon shear stresses, and yield depends more upon normal stresses.
  • EBoth phenomena result from the same forces.

Q7:

How is strain rate related to primary creep?

  • APrimary creep exhibits a decreasing strain rate.
  • BPrimary creep exhibits an increasing strain rate.
  • CPrimary creep is an incubation period in which little strain occurs.
  • DPrimary creep exhibits an exponentially increasing strain rate with time.
  • EPrimary creep exhibits a constant strain rate.

Q8:

In the linear-elastic regime, how does the stress required for fracture scale with the size of the initiating defect?

  • AIn proportion to the square root of the size of the defect.
  • BInversely with the square root of the size of the defect.
  • CIn proportion to the size of the defect.
  • DInversely with the first power of the size of the defect.
  • EInversely with the square of the size of the defect.

Q9:

How does creep deformation differ from cyclic fatigue?

  • ACreep occurs on time scales of years; cyclic fatigue occurs on time scales of days.
  • BCyclic fatigue occurs on time scales of years; creep occurs on time scales of decades.
  • CCreep only occurs at low temperatures, but cyclic fatigue can occur at all temperatures.
  • DCyclic fatigue is slow, plastic flow from a constant stress; creep is weakening from repeated or oscillatory loading.
  • ECreep deformation is slow, plastic flow from a constant stress; cyclic fatigue is weakening from repeated or oscillatory loading.

Q10:

For an end-loaded cantilevered beam, how does the bending moment depend upon position along the length of the beam?

  • AIt increases quadratically from the load end to the cantilevered end.
  • BIt decreases quadratically from the load end to the cantilevered end.
  • CIt decreases linearly from the load end to the cantilevered end.
  • DIt is constant.
  • EIt increases linearly from the load end to the cantilevered end.

Q11:

What is the most important property for a creep resistant material to have?

  • Aa high elastic modulus
  • Ba long fatigue life
  • Ca high thermal coefficient of expansion
  • Da high melting temperature
  • Ea high yield strength

Q12:

What design considerations can reduce or limit the effects of cyclic fatigue?

  1. Keeping the material in compression rather than tension
  2. Keeping the material in tension rather than compression
  3. Alleviating stress by drilling holes in the part at regions of high stress
  • AI only
  • BI and III
  • CII and III
  • DIII only
  • EII only

Q13:

What is meant by the phrase "composite material" in engineering mechanics?

  • AA material consisting of two or more phases or materials at a molecular level
  • BA material that is improperly mixed
  • CA material that fractures unevenly when exposed to stress
  • DA material that deforms in stages when exposed to stress
  • EA material that is glued together from plates or fibers

Q14:

Under what condition is creep deformation particularly a concern?

  • Aat high pressures
  • Bwhen vibration is present
  • Cat low temperatures
  • Dwhen materials are in an oxygen-rich environment
  • Eat high temperatures

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