Direct Current Potential Drop Method for the Identification of Fatigue Damage in Triply Periodic Minimal Surfaces Structures for Heat Exchangers

This paper presents a methodology for monitoring fatigue damage in Triply Periodic Minimal Surface (TPMS) lattice structures using the Direct Current Potential Drop (DCPD) technique. The aim of the paper is to validate an experimental setup capable of interrupting fatigue tests at the early propagation phase, before a crack propagation through the entire wall thickness, which is considered as the operational failure condition for TPMS-based heat exchangers. An in-house developed LabVIEW program, to account for the effect of temperature variations, is described. The validation of the proposed methodology is supported by analyzing the fracture surfaces of specimens whose tests were interrupted using the technique. The DCPD method is also employed to gain insights into the stages of fatigue life—nucleation and propagation. The results of the DCPD are compared with common methods of fatigue test monitoring—that is, axial stiffness drop, highlighting the superior capabilities of the DCPD.