Question 6.40: From your experience with Prob. 6–39 and Ex. 6–19, you obser......
From your experience with Prob. 6–39 and Ex. 6–19, you observed that for completely reversed axial and bending fatigue, it is possible to
- Observe the COVs associated with a priori design considerations.
- Note the reliability goal.
- Find the mean design factor .nd which will permit making a geometric design decision that will attain the goal using deterministic methods in conjunction with {\bar{n}}_{d}.
Formulate an interactive computer program that will enable the user to find {\bar{n}}_{d}. While the material properties {S}_{u t},\,{S}_{y}, and the load COV must be input by the user, all of the COVs associated with {\phi}_{0.{30}},\,{k}_{a},\,{k}_{c},\,{k}_{d},\,{and}\,{K}_{f} can be internal, and answers to questions will allow {{C}}_{\sigma} and {{C}}_{S}, as well as {{C}}_{n } and {\bar{n}}_{d}, to be calculated. Later you can add improvements. Test your program with problems you have already solved.
Each computer program will differ in detail. When the programs are working, the experience should reinforce that the decision regarding {\bar{n}}_{f} is independent of mean values of strength, stress or associated geometry. The reliability goal can be realized by noting the impact of all those a priori decisions.