Conductivity Profile Determination by Eddy Current for Shot Peened Superalloy Surfaces Toward Residual Stress Assessment

The Effect of Hardness on Eddy Current Residual Stress Profiling in Shot-Peened Nickel Alloys

“…Both techniques indicated that at any given frequency the measured AECC corresponds roughly to the actual electric conductivity at half of the standard penetration depth assuming that (i) the electric conductivity variation is limited to a shallow surface region of depth much less than the probe coil diameter, (ii) the relative change in electric conductivity is less than a few percents, and (iii) the electric conductivity depth profile is continuous and fairly smooth. Alternatively, best fitting of the measured electric coil impedance with the known analytical solution can be used assuming that the conductivity profile can be characterized by a small number of independent parameters [24]. Finally, the sought residual stress profile is calculated from the electric conductivity profile based on the piezoresistivity coefficient of the material, which is determined separately from material calibration measurements using known external applied stresses [17].…”

“…Therefore, we cannot fully reconstruct the critical near-surface part of the residual stress profile in moderately peened components using only typical inspection frequencies below 10 MHz. In such cases, special high-frequency inspection techniques are needed to extend the frequency range up to 50-80 MHz, i.e., beyond the range of commercially available instruments [22][23][24][25][26].…”

“…A recent paper by the authors reviewed four previously unreported experimental observations of anomalous materials behavior and proposed further research efforts to better understand the underlying physical mechanisms and to mitigate the adverse influence of these [25]. The most important case of apparently anomalous behavior was observed in precipitation-hardened IN718 material that is very different from those of the commercial versions reported in the literature [15,[18][19][20][21][22][23][24]. Figure 3 shows typical AECC spectra measured in (a) annealed IN718, (b) precipitation-hardened IN718, and (c) Ti-6Al-4V specimens shot-peened to different intensities.…”

Effect of deep cold rolling on mechanical properties and microstructure of nickel-based superalloys

“…Shot Peening (SP) uses spherical balls called shots or projectiles to impact the part surface at high velocities. SP has been traditionally used for nickel-based superalloys including IN718, waspaloy, IN100 and RR1000 [6][7][8][9][10][11][12][13]. Shot peening typically produces highly deformed surface layer, consisting of nanocrystalline structure and high density of statistically distributed dislocations, which improves fatigue life of the components.…”

Numerical Simulation on Stress Measurement with Eddy Current Thermography

“…Compared to traditional stress measurement of nondestructive testing methods like ultrasonic etc., eddy current thermography method have abilities to obtain the noncontact testing result of a single large detection area; achieve high detection precision and resolution of complex geometry component; use the distribution of residual stresses for prior detection in a wide range. In recent years, the application of eddy current thermography detection method to stress detection technology are popularity [13][14][15][16][17] , many studies are focus on the stress distribution and temperature response curve in thermal image graph with different stress states and various conductive.…”