Theory of Failure List of Questions with Answers

  1. σ_1 is the only stress to use to find the factor of safety by the maximum normal stress theory of failure
    • True
    • False
  2. A load is changing on a part from 1,000 lb to 5,000 lb, the average and range loads are
    • 6,000 lb and 4,000 lb
    • 5,000 lb and 1,000 lb
    • 3,000 lb and 2,000 lb
    • 1,000 lb and 5,000 lb
  3. A part is loaded under service stress for 25,000 reversals, then under a higher stress for 35,000 reversals until failure. If the total life under the larger stress alone is 36,000 reversals, what is the estimated life under the service load?
    • 900,000 reversals
    • 37,000 reversals
    • 50,000 reversals
    • 60,000 reversals
  4. Brittle materials fail in yielding
    • True
    • False
  5. By applying 10,000 in.lb torque to this non-rotating shaft, the torque reactions are
    • T1=5,000 in.lb; T2=5,000 in.lb
    • T1=6,000 in.lb; T2=4,000 in.lb
    • T1=4,000 in.lb; T2=6,000 in.lb
    • None of the above
  6. For a ductile material, the yield stress in shear is the same as it is for tension
    • True
    • False
  7. For a loaded part, the state of stress is σ_x=2,000 psi, σ_y=-8000 psi, τ_xy=0. If σ_yp=45,000 psi, what is the factor of safety using the maximum normal stress theory of failure?
    • 5.625
    • 22.5
    • 4.5
    • 7.5
  8. For a safe design in an alternating loading situation by the modified Goodman approach, two equations must be satisfied
    • True
    • False
  9. For a shaft that is transmitting 145 HP while turning at 1,200 rpm, the torque is
    • 760.2 in.lb
    • 6722 in.lb
    • 7615.5 in.lb
    • 2235.3 in.lb
  10. For a shaft under torque, the only type of deformation that will result is the rotation of the cross-sections with respect to each other
    • True
    • False
  11. For a brittle material, there are two curves for the stress-strain relationship–one for the tension and the other for compression.
    • True
    • False
  12. If a part fails by yielding, it will sustain permanent deformation
    • True
    • False
  13. In order to apply one of the failure theories to estimate the factor of safety, we have to
    • use the state of stress
    • find the principal stresses
    • calculate the maximum shear stress
    • find the yielding stress of the material
  14. Maximum shear theory of failure only applies to brittle materials
    • True
    • False
  15. Stress concentration factors are functions of
    • Load
    • Geometry
    • Material
    • Geometry and type of loading
  16. Stress concentration factors must be applied when we are using brittle materials
    • True
    • False
  17. The principal stresses for a part are σ_1=20 MPa, σ_2=5 MPa. What is the factor of safety using the Mises Henckey theory of failure if σ_yp=100 MPa?
    • 6.1
    • 6.5
    • 5.55
    • 8.23
  18. The shear stress on a cross-section of a shaft under torsion is linearly proportional to its radius
    • True
    • False
  19. A torque applied to one end of a shaft, while the other end is keyed against rotation. The torque along the shaft will be proportional to the length
    • True
    • False
  20. Ultimate stress is the same as yielding stress
    • True
    • False
  21. When solving for the factor of safety in a combined steady and alternating loading situation, stress concentration factors must be applied for both average and range stresses.
    • True
    • False
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