Conductivity profile determination by eddy current for shot-peened superalloy surfaces toward residual stress assessment

Shen, Yuping; Lee, C.; Lo, C. C. H.; Nakagawa, N.; Frishman, Anatoli M.

doi:10.1063/1.2403970

Cited by 35 publications

(19 citation statements)

References 16 publications

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“…Eddy current (EC) method has been studied regarding its potential for measuring subsurface and surface residual stress based on the empirical piezoresistivity effect [2][3][4][5][6]. It has been reported that shot peening-induced change in conductivity measured using the EC method is affected by the microstructure of the material [5,[7][8].The objective of this study is to understand how the microstructure of the samples affect the eddy current measurements.…”

Section: Introductionmentioning

confidence: 99%

Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

Chandrasekar¹,

Lo²,

Frishman³

et al. 2012

AIP Conference Proceedings

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This paper reports on a microstructural study of a nickel-base superalloy, Inconel 718, with a focus on quantifying precipitate density and their effects on conductivity variations. The study is motivated by eddy current (EC) characterization of residual stresses, where observed EC signals are attempted to correlate with stress profiles of shot peened superalloy surfaces. It has been observed that the correlation is less universal than anticipated, and in fact strongly influenced by the material hardness, or the aging conditions. For example, the soft sample surface exhibits significantly stronger EC signals than the fully hardened sample when both are shot peened at the same Almen intensity. Thus, the objective of the present study is to examine this complex material response against aging and shot peening treatments at the microstructure scale, by the use of techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We will describe preparations of a series of Inconel 718 samples that was aged and shot peened at various conditions, and present microstructural data obtained from SEM and TEM images such as precipitate densities, correlated with bulk properties such as the hardness and conductivity. ABSTRACT. This paper reports on a microstructural study of a nickel-base superalloy, Inconel 718, with a focus on quantifying precipitate density and their effects on conductivity variations. The study is motivated by eddy current (EC) characterization of residual stresses, where observed EC signals are attempted to correlate with stress profiles of shot peened superalloy surfaces. It has been observed that the correlation is less universal than anticipated, and in fact strongly influenced by the material hardness, or the aging conditions. For example, the soft sample surface exhibits significantly stronger EC signals than the fully hardened sample when both are shot peened at the same Almen intensity. Thus, the objective of the present study is to examine this complex material response against aging and shot peening treatments at the microstructure scale, by the use of techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We will describe preparations of a series of Inconel 718 samples that was aged and shot peened at various conditions, and present microstructural data obtained from SEM and TEM images such as precipitate densities, correlated with bulk properties such as the hardness and conductivity.

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Section: Introductionmentioning

confidence: 99%

Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

Chandrasekar¹,

Lo²,

Frishman³

et al. 2012

AIP Conference Proceedings

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“…Using this method, the authors previously showed that the electromagnetic properties of the surface of alloy tool steel, Japanese Industrial Standard (JIS) SKD61, peened by CP varied with processing time [10]. Also using this method, the electrical conductivity in shot-peened nickel-base superalloys was found to vary [8,9]. Blodgett and Nagy used an eddy current method to show that the electrical conductivity varied with axial stress [5].…”

Section: Introductionmentioning

confidence: 93%

“…There are a number of methods that use electromagnetic properties to evaluate the residual stress in the surface layers of metallic components, such as the potential drop technique [6], the Barkhausen method [7], and the eddy current method [5,8,9]. In the present paper, we examine the eddy current method in order to establish a rapid nondestructive test for measuring stress in the surface layers of various metallic materials, including paramagnetic and ferromagnetic materials.…”

Section: Introductionmentioning

confidence: 98%

Evaluation of Equibiaxial Compressive Stress Introduced into Austenitic Stainless Steel Using an Eddy Current Method

Sekine

Soyama

2011

J Nondestruct Eval

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Equibiaxial compressive residual stress is introduced into steel after peening in order to improve both its resistance to stress corrosion cracking and its fatigue strength. Thus, a nondestructive and relatively quick method to evaluate the equibiaxial compressive residual stress in a surface layer modified by peening is required in order to evaluate the peening intensity needed to enhance the integrity of structural components. The purpose of the work reported here is to establish an eddy current method to evaluate equibiaxial compressive stress which can be applied to the residual stress introduced into various non-ferromagnetic materials after peening. To this end, hydraulic jacks were used to elastically deform specimens of the austenitic stainless steel, Japanese Industrial Standard (JIS) SUS316L, thereby introducing an equibiaxial compressive stress. In the case of SUS316L steel, stress-induced martensitic transformation is rare. The electromagnetic properties of these specimens were then measured. In addition, the eddy current signals from peened specimens were compared with these. The results demonstrate that it is possible to establish a method for evaluating the equibiaxial stress utilizing eddy current signals.

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“…It is observed in the present study that increase or decrease in electrical conductivity can be under predicted, if material isotropy is assumed. Shen et al (2007) observed that anomalous negative conductivity changes in the near surface region in shot peened nickel alloys is due to, among other factors, anisotropic deformation of the stressed material. Morozov et al (2010) investigated anisotropic in-plane longitudinal and transverse electrical conductivity inversion for −2% variations using directional probes.…”

Section: Introductionmentioning

confidence: 96%

Investigation of 3D anisotropic electrical conductivity in TIG welded 5A06 Al alloy using eddy currents

Shakoor

Zhou

2011

Journal of Materials Processing Technology

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Conductivity profile determination by eddy current for shot-peened superalloy surfaces toward residual stress assessment

Cited by 35 publications

References 16 publications

Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

Quantification of precipitates and their effects on the response of nickel-base superalloy to shot peening

Evaluation of Equibiaxial Compressive Stress Introduced into Austenitic Stainless Steel Using an Eddy Current Method

Investigation of 3D anisotropic electrical conductivity in TIG welded 5A06 Al alloy using eddy currents

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