Small sample test approach for obtaining P-S-N curves based on a unified mathematical model

Abstract

[Formula: see text] curves provide the essential reference data for fatigue life prediction and reliability evaluation of mechanical component. In practical applications, [Formula: see text] curves can be transformed as a group of straight lines in the dual-logarithm coordinates system. Based on such a characteristic and according to the basic principle that two points that do not coincide can uniquely determine a straight line, a small sample test approach for determining [Formula: see text] curves from the viewpoint of geometry is proposed. The proposed approach can derive the [Formula: see text] curves of mechanical component from a unified mathematical model, which can significantly reduce the fatigue test time and the number of specimens. The fatigue test data of engine connecting rod under four stress levels are applied to verify the proposed approach. Compared with traditional group test approach, both the number of specimens and fatigue test time are decreased by 42.11%, but the average relative error of the proposed approach is less than 7%. Furthermore, the proposed approach has the advantages of mathematically being simple and easy to be used in engineering.