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Lesson: Stress and Strain: Material Properties

Worksheet • 14 Questions

Q1:

What is a critical crack length most associated with?

  • Afast fracture
  • Bhigh ductility
  • Cplastic yielding
  • Dnon-protective oxide films
  • Ecreep permanent strain

Q2:

What is the behavior of secondary creep?

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

Q3:

How do brittle materials differ from ductile materials?

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

Q4:

How do yield and fracture processes generally vary with temperature?

  • AFracture becomes more likely at lower temperatures, and yield becomes more likely at higher temperatures.
  • BBoth responses have unpredictable variations with temperature.
  • CBoth yield and fracture become more likely at higher temperatures.
  • DYield becomes more likely at lower temperatures, and fracture becomes more likely at higher temperatures.
  • EBoth yield and fracture become more likely at lower temperatures.

Q5:

How does creep vary with temperature?

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

Q6:

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

  • AYield depends more upon shear stresses, and fracture depends more upon normal stresses.
  • BFracture results from steady stress, and yield results from time-varying stress.
  • CFracture depends more upon shear stresses, and yield depends more upon normal stresses.
  • DBoth phenomena result from the same forces.
  • EFracture depends more upon shear stresses, and yield depends more upon normal stresses.

Q7:

How is strain rate related to primary creep?

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

Q8:

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

  • AInversely with the square root of the size of the defect.
  • BIn proportion to the size of the defect.
  • CInversely with the first power of the size of the defect.
  • DIn proportion to the square root 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 deformation is slow, plastic flow from a constant stress; cyclic fatigue is weakening from repeated or oscillatory loading.
  • BCyclic fatigue occurs on time scales of years; creep occurs on time scales of decades.
  • CCyclic fatigue is slow, plastic flow from a constant stress; creep is weakening from repeated or oscillatory loading.
  • DCreep occurs on time scales of years; cyclic fatigue occurs on time scales of days.
  • ECreep only occurs at low temperatures, but cyclic fatigue can occur at all temperatures.

Q10:

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

  • AIt increases linearly 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 increases quadratically from the load end to the cantilevered end.
  • EIt is constant.

Q11:

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

  • Aa high melting temperature
  • Ba high thermal coefficient of expansion
  • Ca high elastic modulus
  • Da long fatigue life
  • 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
  • BIII only
  • CI and III
  • DII only
  • EII and III

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 glued together from plates or fibers
  • CA material that is improperly mixed
  • DA material that fractures unevenly when exposed to stress
  • EA material that deforms in stages when exposed to stress

Q14:

Under what condition is creep deformation particularly a concern?

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