Paper: (2014010)MODIFYING THE MODIFIED GOODMAN DIAGRAM

The Modified Goodman Diagram (MGD) has been used since the 1960s to establish allowable loads and stresses that should be applied to API grade sucker rods.  A previous review of factors that affected the fatigue response for sucker rods has been published.  This work showed that very conservative nature of the MGD for fatigue performance of rods and prompted that much higher allowable loads/stresses could be applied without causing increases in field failures.  This paper will discuss the prior publications and combine the responses from current fatigue testing to recommend a higher allowable loading for the industry using the tensile strength divided by 2.8 versus the prior MDG using the tensile strength divided by 4.0.