A mechanical spring used in a scale was designed with a safety factor of 4.0 based on the mean strength divided by the mean load. Its design strength has a lognormal distribution with a median of 300...

A mechanical spring used in a scale was designed with a safety factor of 4.0 based on the mean strength divided by the mean load. Its design strength has a lognormal distribution with a median of 300 Ib and a shape parameter of .3592. The load placed on the spring also has a lognormal distribution with a median of 40 pounds and a shape parameter of 1.1774. (a) What is the static reliability? (b) If the design strength is a constant 300 pounds, and the above stress is applied periodically at a mean rate of once every two days, what is R(30 days)?