NEW APPROXIMATIONS FOR SORM INTEGRALS

New and simple closed form approximations for SORM integrals which can be used for reliability estimations of rare and common events are pro posed and compared with exact results, Breitung's asymptotic and Tvedt 's three-term formulas. In numerical examples, it is shown that the pr oposed approximations are yielding very good results and better than t he available ones for all values of beta and for all curvatures. Thus SORM reliability estimations can be performed more accurately using th e developed formulas even in the case of small or negative beta values .