Question 6.44: Write and test computer subroutines or procedures that will ......

Write and test computer subroutines or procedures that will implement

(a) Table 6–2, returning a, b, C, and {\bar{k}}_{a} .

(b) Equation (6–20) using Table 6–4, returning k_{b}.

(c) Table 6–11, returning α, β, C, and \bar k_{c}.

(d) Equations (6–27) and (6–75), returning \bar k_{d} and C_{kd}.

 

k_{b}={\left\{\begin{array}{l l}{(d/0.3)^{-0.107}=0.879d^{-0.107}}&{0.11\leq d\leq2\operatorname*{in}}\\ {0.91d^{-0.157}}&{2\lt d\leq10\operatorname{in}}\\ {(d/7.62)^{-0.107}=1.24d^{-0.107}}&{2.79\leq d\leq51\ \operatorname*{mm}}\\ {1.51d^{-0.157}}&{51\lt 254\operatorname*{mm}}\end{array}\right.}                                      (6-20)

k_{d}=0.975+0.432(10^{-3})T_{F}-0.115(10^{-5})T_{F}^{2}+0.104(10^{-8})T_{F}^{3}-0.595(10^{-12})T_{F}^{4}                                         (6-27)

{k}_{d}=\bar{k}_{d}{{L N}}(1,0.11)                        (6-75)

Table 6–2
Parameters for Marin Surface Modification Factor, Eq. (6–19)

k_{a}=a S_{u t}^{b}           (6-19)

Surface Finish Factor a Exponent b
S_{u t}, kpsi S_{u t}, Mpa
Ground 1.34 1.58 -0.085
Machined or cold-drawn 2.70 4.51 -0.265
Hot-rolled 14.4 57.7 -0.718
As-forged 39.9 272 -0.995
Table 6–4
Effect of Operating
Temperature on the
Tensile Strength of
Steel.* (S_{T} = tensile
strength at operating
temperature; S_{R T} = tensile strength
at room temperature; 0.099\leq{\hat{\sigma}}\leq0.110)
Temperature, °C S_{T}/S_{R T} Temperature, °F S_{T}/S_{R T}
20 1.000 70 1.000
50 1.010 100 1.008
100 1.020 200 1.020
150 1.025 300 1.024
200 1.020 400 1.018
250 1.000 500 0.995
300 0.975 600 0.963
350 0.943 700 0.927
400 0.900 800 0.872
450 0.843 900 0.797
500 0.768 1000 0.698
550 0.672 1100 0.567
600 0.549
*Data source: Fig. 2–9.
Table 6–11
Parameters in Marin Loading Factor
Mode of Loading \mathrm{k_{c}}=\alpha\,\mathrm{S_{ut}^{-\beta}}\,\mathrm{LN}(1,{C}) Average

K_{c}

\alpha {{{\beta}}} C
kpsi Mpa
Bending 1 1 0 0 1
Axial 1.23 1.43 -0.0778 0.125 0.85
Torsion 0.328 0.258 0.125 0.125 0.59
fig. 2.9
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The results of Probs. 6-41 to 6-44 will be the basis of a class computer aid for fatigue problems. The codes should be made available to the class through the library of the computer network or main frame available to your students.

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