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?

  • Anon-protective oxide films
  • Bhigh ductility
  • Cfast fracture
  • Dcreep permanent strain
  • Eplastic yielding

Q2:

What is the behavior of secondary creep?

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

Q3:

How do brittle materials differ from ductile materials?

  • ADuctile materials have a lower yield stress than brittle materials.
  • BBrittle materials have a lower modulus of elasticity than ductile materials.
  • CBrittle materials fail more suddenly under stress; ductile materials yield before fracture.
  • DDuctile materials fail more suddenly under stress; brittle materials yield before fracture.
  • EBrittle materials have a higher ultimate tensile strength than ductile materials.

Q4:

How do yield and fracture processes generally vary with temperature?

  • AYield becomes more likely at lower temperatures, and fracture becomes more likely at higher temperatures.
  • BBoth yield and fracture become more likely at higher temperatures.
  • CBoth yield and fracture become more likely at lower temperatures.
  • DBoth responses have unpredictable variations with temperature.
  • EFracture becomes more likely at lower temperatures, and yield becomes more likely at higher temperatures.

Q5:

How does creep vary with temperature?

  • AIt increases linearly with increasing temperature.
  • BIt increases exponentially 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 depends more upon shear stresses, and yield depends more upon normal stresses.
  • BBoth phenomena result from the same forces.
  • CYield depends more upon shear stresses, and fracture depends more upon normal stresses.
  • DFracture results from steady stress, and yield results from time-varying stress.
  • EFracture depends more upon shear stresses, and yield depends more upon normal stresses.

Q7:

How is strain rate related to primary creep?

  • APrimary creep is an incubation period in which little strain occurs.
  • BPrimary creep exhibits an increasing strain rate.
  • CPrimary creep exhibits a decreasing strain rate.
  • 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 size of the defect.
  • BInversely with the square root of the size of the defect.
  • CIn proportion to the square root of 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 only occurs at low temperatures, but cyclic fatigue can occur at all temperatures.
  • BCreep occurs on time scales of years; cyclic fatigue occurs on time scales of days.
  • CCreep deformation is slow, plastic flow from a constant stress; cyclic fatigue is weakening from repeated or oscillatory loading.
  • DCyclic fatigue is slow, plastic flow from a constant stress; creep is weakening from repeated or oscillatory loading.
  • ECyclic fatigue occurs on time scales of years; creep occurs on time scales of decades.

Q10:

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

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

Q11:

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

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

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
  • AII only
  • BI only
  • CIII only
  • DI and III
  • EII and III

Q13:

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

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

Q14:

Under what condition is creep deformation particularly a concern?

  • Aat high pressures
  • Bat low temperatures
  • Cwhen materials are in an oxygen-rich environment
  • Dat high temperatures
  • Ewhen vibration is present

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