Creep strain measurements using an Alternating Current Potential Drop method: A Nondestructive approach

Online assessment of the state of creep damage of a component in service is very useful in ensuring safety of structures, estimation of remaining life for life extension programs. Thus, in-situ monitoring of the progress of creep damage in such components is very important and a challenging task. Alternating current potential drop (ACPD) technique along with Linear Variable Differential Transducers (LVDT’s) was employed to measure voltage drop during creep tests of Alloy 718 at 600-700°C and 600-750MPa. The ACPD voltage drop data were subsequently converted into creep strain using appropriate formula and compared with the creep strain measured using LVDT’s. It has been observed that the creep strains derived from the ACPD data match well with the creep strains measured using LVDT for all the test conditions. This study demonstrates that the ACPD technique has a potential to be employed as an effective non-destructive tool for in-situ monitoring of creep strain in components