Near-Surface Residual Stress-Profiling With High Frequency Eddy Current Conductivity Measurement

Hillmann, Susanne; Heuer, Henning; Baron, H.-U.; Bamberg, Joachim; Yashan, André; Meyendorf, Norbert

doi:10.1063/1.3114113

Cited by 15 publications

(14 citation statements)

References 2 publications

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“…The results obtained on some nickel-based superalloys (IN718) demonstrate that the relationship between the electric conductivity depth profile and the residual stress profile is very sensitive to the state of precipitation hardening [25,26]. Similarly, in the examined strain-hardenable aluminium alloys, interaction of dislocations and precipitates of solute atoms (Cu in AA-2024, Mg in AA-5083 and Zn in AA-7075) lead to dynamic strain ageing (PLC effect) during the PD of alloys [27], whereupon the mobile dislocations first are pinned on the precipitates and then are released in avalanche-like event owing to energy of growing applied stress.…”

Section: Resultsmentioning

confidence: 97%

Elastic and plastic strain effects on eddy current response of aluminium alloys

Morozov

Tian

Withers

2013

Nondestructive Testing and Evaluation

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This paper presents the study of correlation between elasto-plastic state of metallic components and their eddy current (EC) response. Aluminium alloy samples are plastically deformed by tensile loading up to 10% of plastic strain with step of 0.5%, and elastic dependencies of EC response are obtained for each plastic state. The method demonstrates capability of separating elastic EC responses according to the amount of plastic strain. The real part of EC response is found to be sensitive mainly to elastic stress. In contrast, the imaginary part of EC response is sensitive mainly to plasticity, with dependence being monotonic in the absence of strain-hardening. Strainhardenable materials represent some challenge for the method due to non-uniform plastic flow.

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Section: Resultsmentioning

confidence: 97%

Elastic and plastic strain effects on eddy current response of aluminium alloys

Morozov

Tian

Withers

2013

Nondestructive Testing and Evaluation

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“…Despite the significant potential of EC, several challenges have been identified against development of the measurement technique for residual stress characterization. In particular, it has been found in recent studies that the EC responses of Inconel 718 to shot peening depend on the underlying microstructures [5][6][7][8]. These findings indicate the confounding effects of metallurgical factors on EC residual stress measurements, and raised doubts about the applicability of the empirical piezoresistivity relationship to shotpeened surfaces without modification or compensation for the competing effects of peening-induced changes in the material conditions.…”

Section: Introductionmentioning

confidence: 85%

Effects of cold work on near-surface conductivity profiles in laser shock peened and shot peened nickel-base superalloy

Lesthaeghe¹,

Larson²,

Chandrasekar³

et al. 2013

AIP Conference Proceedings

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This paper reports on a study of the effects of cold work induced by surface enhancement treatment on conductivity profiles in nickel-base superalloys, as part of the on-going efforts aimed at evaluating the feasibility of characterizing near-surface residual stress profiles in peened engine components using a swept frequency eddy current (SFEC) technique. The approach is based on the empirical piezoresistivity effect that correlates conductivity changes with residual stress, but recent studies have shown that conductivity changes induced by peening processes are also influenced by metallurgical factors such as cold work. In this study, conductivity deviation profiles were obtained by model-based inversion of SFEC signals from a set of aged Inconel 718 samples, which were either shot peened or laser shock peened to produce different residual stress and cold work profiles. The laser shock peened samples exhibit a larger increase in surface conductivity and deeper conductivity profiles, which are attributed to a smaller amount of surface cold work and deeper residual stress profiles created by laser shock peening than by shot peening. ABSTRACT. This paper reports on a study of the effects of cold work induced by surface enhancement treatment on conductivity profiles in nickel-base superalloys, as part of the on-going efforts aimed at evaluating the feasibility of characterizing near-surface residual stress profiles in peened engine components using a swept frequency eddy current (SFEC) technique. The approach is based on the empirical piezoresistivity effect that correlates conductivity changes with residual stress, but recent studies have shown that conductivity changes induced by peening processes are also influenced by metallurgical factors such as cold work. In this study, conductivity deviation profiles were obtained by model-based inversion of SFEC signals from a set of aged Inconel 718 samples, which were either shot peened or laser shock peened to produce different residual stress and cold work profiles. The laser shock peened samples exhibit a larger increase in surface conductivity and deeper conductivity profiles, which are attributed to a smaller amount of surface cold work and deeper residual stress profiles created by laser shock peening than by shot peening.

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“…Shadowing effects Backside contamination sensitivity towards conductivity changes, the Eddy Current generated by high frequency offers not only high density but also a variety of inspection depths [4]. Particularly, backside has been more difficult to investigate than surface in conventional solar cell inspection methods.…”

Section: Inhomogeneitiesmentioning

confidence: 99%

Eddy current imaging for electrical characterization of silicon solar cells and TCO layers

et al. 2015

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Eddy Current Testing has been mainly used to determine defects of conductive materials and wall thicknesses in heavy industries such as construction or aerospace. Recently, high frequency Eddy Current imaging technology was developed. This enables the acquirement of information of different depth level in conductive thin-film structures by realizing proper standard penetration depth. In this paper, we summarize the state of the art applications focusing on PV industry and extend the analysis implementing achievements by applying spatially resolved Eddy Current Testing. The specific state of frequency and complex phase angle rotation demonstrates diverse defects from front to back side of silicon solar cells and characterizes homogeneity of sheet resistance in Transparent Conductive Oxide (TCO) layers. In order to verify technical feasibility, measurement results from the Multi Parameter Eddy Current Scanner, MPECS are compared to the results from Electroluminescence

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Near-Surface Residual Stress-Profiling With High Frequency Eddy Current Conductivity Measurement

Cited by 15 publications

References 2 publications

Elastic and plastic strain effects on eddy current response of aluminium alloys

Elastic and plastic strain effects on eddy current response of aluminium alloys

Effects of cold work on near-surface conductivity profiles in laser shock peened and shot peened nickel-base superalloy

Eddy current imaging for electrical characterization of silicon solar cells and TCO layers

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