[JP2]Based on the Von Mises yield criterion

plastic deformation theory

and distortion energy theory

this study an-alytically demonstrates that

under the action of triaxial stress during actual pipeline operation

the equivalent strain is always greater than the circumferential strain.Therefore

replacing circumferential strain with equivalent strain more accurately reflects the creep behavior of pipelines under a three-dimensional stress state.Furthermore

building on the creep measurement points defined in current standards

this paper proposes a novel "dual-cross-section" creep measurement design.This approach enables the measurement of both circumferential and axial strains

from which radial strain can be inferred using the condition of constant volume.The equivalent strain is then computed accordingly.By substituting equivalent strain for circumferential strain in the creep deformation life loss model

the life assessment method is refined

resulting in improved evaluation accuracy.[JP3]The refined formula is .