Electrical impedance characterization for damage detection in highly conductive additively manufactured metal mesh structuresAbigail Gilmore, Saptarshi Mukherjee, Tammy Chang, David StobbeLawrence Livermore National LaboratoryIn the past decade, the ability to additively manufacture highly conductive metal structures has become increasingly advanced. Predominant approaches such as direct metal laser sintering (DMLS) have the ability to produce fine mesh geometries to provide lightweight interior support for metal parts, at a level of granularity and complexity that is not possible to machine. However, with the increasing level of structural complexity, there is a need to reliably assess their manufacturing quality and detect potential defects. Current nondestructive evaluation (NDE) methods such as ultrasonic inspection and X-Ray computed tomography are high in computational cost and suffer from low sensitivity towards defects in highly conductive metal structures. Alternatively, a current injection-based method could be used to inject alternating current signals into the metal structures and detect discontinuities in impedance due to defects, using electrical impedance tomography (EIT).Despite its promise, current EIT systems require efficient current injection so as to record high-fidelity electrical signals that can be used in a tomographic reconstruction algorithm for imaging defects. This is significantly difficult in additive manufacturing due to several factors such as printing inconsistencies, available space for electrode placement, and variance of the material’s conductivity.This paper discusses efficient current injection and voltage measurement strategies in order to obtain consistent high-fidelity measurements from such metal structures. Several factors such as determining the variance of the electrical conductivity from measurements, electrode placement and design for optimum current injection into the mesh geometries, and validation of experiments with an electrostatic numerical model will be discussed as part of this research. Preliminary results show good correlation between the simulated and measured voltages. Additionally, we investigate the capability of the experimental system to detect damages in cobalt chromium DMLS rectangular mesh structures. Finally, the feasibility of reconstructing the damage location by computing the sensitivities of the measured boundary voltages utilizing an adjoint field method is investigated and discussed. This research lays the foundation for a high-fidelity EIT system for NDE of additively manufactured metal structures.Prepared by LLNL under Contract DE-AC52-07NA27344. The document release number is LLNL-ABS-821777.

Electrical Impedance Characterization for Damage Detection in Highly Conductive Additively Manufactured Metal Mesh Structures

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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