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Materials Science and Engineering

Internal stresses

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Full-Text Articles in Physics

Effects Of Cold Work On Near-Surface Conductivity Profiles In Laser Shock Peened And Shot Peened Nickel-Base Superalloy, Tyler J. Lesthaeghe, Brian F. Larson, Ramya Chandrasekar, Anatoli M. Frishman, Chester C.H. Lo, Norio Nakagawa Jul 2012

Effects Of Cold Work On Near-Surface Conductivity Profiles In Laser Shock Peened And Shot Peened Nickel-Base Superalloy, Tyler J. Lesthaeghe, Brian F. Larson, Ramya Chandrasekar, Anatoli M. Frishman, Chester C.H. Lo, Norio Nakagawa

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

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 ...


Self-Consistent Swept Frequency Eddy Current Measurements For Characterization Of Near Surface Material Conditions, Chester C.H. Lo, Anatoli M. Frishman, Y. Shen, Norio Nakagawa Jul 2008

Self-Consistent Swept Frequency Eddy Current Measurements For Characterization Of Near Surface Material Conditions, Chester C.H. Lo, Anatoli M. Frishman, Y. Shen, Norio Nakagawa

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

This paper reports on a self‐consistent, swept frequency eddy current (SFEC) technique for characterizing surface and sub‐surface conditions of materials, with specific applications to detecting residual stresses in shot‐peened Ni‐base superalloys and surface oxidation in engineering components. The technique involves measuring lift‐off normalized vertical component signal to suppress lift off noise and instrumentation effect. Theoretical study shows that the vertical component signals are insensitive to coil dimensions, thus enabling EC measurements in separate frequency bands using multiple coils, while yielding continuous broad‐band data so that both the bulk conductivity and near‐surface conductivity profile ...


A Scaling Law For Nondestructive Evaluation Of Shot Peening Induced Surface Material Property Deviations, Anatoli M. Frishman, Chester C.H. Lo, Y. Shen, Norio Nakagawa Jul 2008

A Scaling Law For Nondestructive Evaluation Of Shot Peening Induced Surface Material Property Deviations, Anatoli M. Frishman, Chester C.H. Lo, Y. Shen, Norio Nakagawa

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

Shot peening is frequently used to improve mechanical characteristics of metallic components’ surfaces. The physical properties of shot peened surfaces exhibit deviations from their bulk values. This paper shows that there exists a scaling law (universality) among seemingly unrelated material property deviations and among different peening conditions. We present examples and support for scaling behaviors based on experimental data on Almen strip deflection, cold work and residual stress profiles of a shot peened nickel‐base superalloy (Waspaloy), and swept frequency eddy current signals used for NDE studies of another shot peened nickel‐base superalloy (Inconel 718). In addition, a fast ...


Shot-Peening Intensities Vs. Eddy Current Signals As Seen In Iterative Treatment-Measurement Experiment, Norio Nakagawa, Anatoli M. Frishman, Y. Shen, Chester C.H. Lo Jul 2008

Shot-Peening Intensities Vs. Eddy Current Signals As Seen In Iterative Treatment-Measurement Experiment, Norio Nakagawa, Anatoli M. Frishman, Y. Shen, Chester C.H. Lo

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

We report on progress in a swept high frequency eddy current (SHFEC) technique for characterization of surface residual stress on shot‐peened superalloy surfaces. Our aim here is to demonstrate the sensitivity of our measurement for practical shot peening intensities, i.e. at 4 ∼ 6 A. First, we present our improved probe and instrumentation being sufficiently sensitive to resolve the surface conditions at these low Almen intensities, where our earlier measurements encountered noise problems. The previous coil was also larger (18 mm in diameter) than desirable. Our new probe integrates smaller coils (12 mm in diameter, forming an AC bridge ...


Large Magnetically Induced Strains In Ni50mn28.7ga21.3 Driven With Collinear Field And Stress, A. Malla, M. J. Dapino, Thomas A. Lograsso, Deborah L. Schlagel Mar 2006

Large Magnetically Induced Strains In Ni50mn28.7ga21.3 Driven With Collinear Field And Stress, A. Malla, M. J. Dapino, Thomas A. Lograsso, Deborah L. Schlagel

Ames Laboratory Publications

Despite the huge magnetic-field-induced strain (MFIS) of up to 9.5% exhibited by certain Ni–Mn–Ga alloys, their usefulness in applications is severely hindered by the electromagnet device needed for driving the alloys with a magnetic field and orthogonal loading stress. In this paper we present macroscopic measurements obtained from a single crystal of Ni50Mn28.7Ga21.3 which demonstrate a large reversible MFIS of −4100 ppm when the alloy is driven with quasistatic magnetic fields and fixed compressive stresses applied collinearly along the [001] axis. This collinear configuration marks a fundamental difference with prior ...