MECH325 - Homework Hints, Answers, and Extra Requirements

Homework 9 (Chapter 12)

TO ENHANCE YOUR LEARNING, PLEASE TRY TO WORK THE PROBLEMS FIRST WITHOUT LOOKING AT THE HINTS AND ANSWERS BELOW.

MAKE SURE YOU SATISFY ALL REQUIREMENTS LISTED BELOW AND IN THE ORIGINAL PROBLEM STATEMENTS (UNLESS INDICATED OTHERWISE BELOW).

NOTE - BECAUSE MOST ANSWERS ARE PROVIDED, IT IS VERY IMPORTANT THAT YOU SHOW ALL STEPS IN YOUR WORK.  THE GRADING WILL BE BASED ON THE COMPLETENESS, CLARITY, AND CORRECTNESS OF YOUR WORK, NOT JUST THE ANSWERS YOU PROVIDE.

12.4
[10 pts]
  • assume the material is plain carbon steel
  • ΔT = 297 in-lb
  • Δτ = 49.9 ksi
12.12
[20 pts]
  • Fs = 3160 N
  • τs = 443 MPa
  • use Su = 1225 MPa (but explain where it comes from)
  • the spring should return to its original length
12.21
[30 pts]
  • the spring mean diameter is different from the outer diameter
  • use Su = 1550 MPa   and   Ks = 1.06  (but explain where they come from)
  • (a)  Fmax = 122 N
  • (b)  k = 3.22 N/mm
  • (c)  Lf = 61.9 mm
  • (d)  no buckling should occur
12.29a,b
[40 pts]
  • based on clash allowance and Fmax,  Fs = 712.5 N
  • based on the specified τs,  CKw = 8.93
  • use C = 7.4 (but explain where it came from)
  • (a)  D = 33.3 mm;  N = 2.44;  Ls = 20.0 mm;  Lf = 35.8 mm
  • (b)  no buckling should occur;  no surge should occur;
    • plot the τmax- τmin diagram with the load point and load line
    • SF = 1.1