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 |
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.