Nondestructive Evaluation Of Residual Stress Research Articles

Nondestructive evaluation of residual stresses in welded joints on the base of a combination of ultrasonic testing and speckle-interferometry

Nondestructive evaluation of residual stresses in welded joints on the base of a combination of ultrasonic testing and speckle-interferometry

Spatially resolved Raman piezospectroscopy for nondestructive evaluation of residual stress in β-Ga2O3 films

In this paper, the piezospectroscopic effect for β-Ga2O3, i.e. the spectral band shift in response to strain/stress, has been calibrated by the indentation method using spatially resolved Raman spectroscopy for quantitative stress evaluation of Ga2O3 devices, taking advantage of the crack-tip tensile stress field and the spatial probe deconvolution. A series of Vickers indentation prints were introduced on (010) and () Ga2O3 single crystals, and the relationships between observed band shifts and residual stresses were clarified to determine the phonon deformation potentials of the Raman bands. Accordingly, a quantitative analysis of the residual stress field in a Ga2O3 thin film grown on (0001) sapphire by plasma-assisted pulsed laser deposition, which revealed the presence of a gradient of incompletely released stress in the depth direction of the film, is shown as an example.

Deep learning-based monitoring of surface residual stress and efficient sensing of AE for laser shock peening

• A multi-channel acoustic emission real-time efficient signal detection method and acquisition system. • A novel spatio-temporal complementary model (CNN-LSTM) for fusion of time-varying AE signal. • Dual circulation LSTM explains the decay mechanism of AE using temporal sampling points. • Stronger correlation between information from AE attenuation profile and surface quality. Laser shock peening (LSP) is one of the main anti-fatigue technologies in high-end manufacturing industries. However, guaranteeing its quality consistency is difficult due to its process complexity. Acoustic emission (AE) is a promising solution to accurately monitoring the surface quality of LSP, although, the large scale of monitoring data is still challenging for industrial applications. This paper studied the in-situ evaluation of surface residual compressive stress (SRCS) for 7075 aluminum alloy in LSP and the efficient sensing of AE based on deep learning methods. Firstly, a monitoring system of LSP with four types of AE sensors was developed in order to simultaneously acquire both the ultra-high and ultra-low amplitude of shock wave. The performance of those sensors is further quantitatively evaluated via long-short term memory (LSTM). Then, a new spatio-temporal parallel CNN-LSTM model for SRCS classification was proposed and experimentally validated to outperform CNN and LSTM after parameters optimization. Finally, aiming to efficient sensing of AE, the importance of different frames of AE signal was analyzed by means of the proposed dual circulation LSTM (DC-LSTM) model, which can accurately locate the key frame of time series signal. Besides, the effects of different frames of AE on classification performance was discussed. It was found that the broadband AE sensor without attenuator shows the highest classification accuracy, while the fast decay stage of AE signal has more contribution to the SRCS classification. This paper provides guidance for real-time non-destructive evaluation of residual stress via AE in laser manufacturing.

A theoretical simulation for MBN testing: Modeling microscopic local magnetization jumps in magnetic domain movement

Magnetic Barkhausen Noise (MBN) signals are adoped for the non-destructive evaluation of residual stress and plastic deformation due to their sensitivity to micro defects in material. Such MBN signals originate from discontinuous magnetization jumps accompanied by blocking of the pinning effect on the magnetic domain. This paper analyzes the influencing factors and laws of MBN non-destructive evaluation by numerically simulating discontinuous magnetization jumps. The pinning effect on the movement of the magnetic domain is considered as a random barrier field with a Gaussian distribution, and the discontinuous magnetization jumps are described as a transition in the local magnetization state. Solving Maxwell equations under varying current excitations based on the finite difference method allows simulating the magnetization evolution during non-destructive testing based on an iterative algorithm to realize MBN signal analysis. The theoretical analyses combined with existing experimental data show that the simulations can predict the influence of the excitation frequency, plastic deformation and stress level on the MBN signals, while also give explanations on some basic experimental phenomena and laws. This proposed theoretical simulation method is available to describe the mechanisms and causes of the MBN signals from a microscopic perspective for magnetic jump events.

Influence of residual plastic strain on the thermoelastic behavior of a titanium alloy

The thermoelastic effect that manifests as a change in temperature of a body undergoing adiabatic elastic deformation has been utilized for full-field stress analysis in solids using the infrared thermal imaging technique. This technique has been used for nondestructive evaluation of residual stresses in components. The present study endeavors to examine the effect of residual plastic strain, due to a previously imposed plastic deformation, on the thermoelastic behavior of solids. Near-α titanium alloy specimens have been plastically deformed, and after reaching a plastic strain level, the test has been interrupted. The thermoelastic response of the interrupted specimens has been examined. The infrared thermal imaging technique has been used to capture the spatiotemporal evolution of the surface temperature of the specimens. It has been observed that the thermoelastic coefficient of the alloy increases as a function of prior/residual plastic strain for small deformations. It has been shown that the theoretical framework used to explain the effect of residual stress on the thermoelastic coefficient assuming a perfect crystal lattice is not applicable to explain the effect of residual plastic strain on the thermoelastic coefficient. A modification of the existing theory has been proposed to explain the dependence of the thermoelastic coefficient on the residual plastic strain. A thermodynamic framework considering the local entropy and internal energy density has been developed to study the behavior. The microscopic aspects of the energetic of thermoelasticity have been discussed and based on this a continuum dislocation dynamic model has been proposed to explain the variation in the thermoelastic coefficient.

Nondestructive evaluation of residual stress via digital holographic photoelasticity

The nondestructive evaluation of residual stress forms a very important aspect of structural engineering. In this context, as per the theory underlying digital holographic photoelasticity, the residual stress field in a transparency can be efficiently and nondestructively evaluated with high accuracy by varying the polarization direction of the reference light beam. In this study, we use a setup to experimentally verify the above mentioned hypothesis. We first record digital holograms before and after heating optically transparent specimens at four different corresponding positions of the reference light polarization. We next solve the four resulting light intensity equations after digital image processing of the four digital holograms to obtain the residual stress. A comparison of our experimental results with those of the drilling method (the conventional approach to determine residual stress) indicates that our digital holographic photoelasticity method can be suitably applied to the nondestructive evaluation of residual stress in transparencies.

Experiment and numerical simulation for laser ultrasonic measurement of residual stress

Laser ultrasonic is a most promising method for non-destructive evaluation of residual stress. The residual stress of thin steel plate is measured by laser ultrasonic technique. The pre-stress loading device is designed which can easily realize the condition of the specimen being laser ultrasonic tested at the same time in the known stress state. By the method of pre-stress loading, the acoustoelastic constants are obtained and the effect of different test directions on the results of surface wave velocity measurement is discussed. On the basis of known acoustoelastic constants, the longitudinal and transverse welding residual stresses are measured by the laser ultrasonic technique. The finite element method is used to simulate the process of surface wave detection of welding residual stress. The pulsed laser is equivalent to the surface load and the relationship between the physical parameters of the laser and the load is established by the correction coefficient. The welding residual stress of the specimen is realized by the ABAQUS function module of predefined field. The results of finite element analysis are in good agreement with the experimental method. The simple and effective numerical and experimental methods for laser ultrasonic measurement of residual stress are demonstrated.

Improvement in accuracy of the measurements of residual stresses due to circumferential welds in thin-walled pipe using Rayleigh wave method

To achieve an acceptable safety in many industrial applications such as nuclear power plants and power generation, it is extremely important to gain an understanding of the magnitudes and distributions of the residual stresses in a pipe formed by joining two sections with a girth butt weld. Most of the methods for high-accuracy measurement of residual stress are destructive. These destructive measurement methods cannot be applied to engineering systems and structures during actual operation. In this paper, we present a method based on the measurement of ultrasonic Rayleigh wave velocity variations versus the stress state for nondestructive evaluation of residual stress in dissimilar pipe welded joint. We show some residual stress profile obtained by this method. These are then compared with other profiles determined using a semi-destructive technique (hole-drilling) that makes it possible to check our results. According to the results, we also present a new method for adjusting the ultrasonic measurements to improve the agreement with the results obtained from other techniques.

Nondestructive Evaluation of Residual Stresses by Heating Method (Simultaneous Estimation of Rate of Heat Release and Residual Stresses)

In the heating method which can be available for nondestructive and in situ measurements of residual stresses, a new method is proposed for simultaneous estimation of the heat flux and residual stresses. The approach is formulated as an inverse problem by using the surface displacements relieved by local heating and the resulting nonlinear least square problem is solved by Levenberg-Marquardt method. In this procedure, the displacements of the direct problem are computed by FEM. The approach is applied to estimation of uniaxial and biaxial stresses in a plate. The numerical results show the effectiveness of the proposed method.

In-depth analysis of residual stress in an alumina coating on silicon nitride substrate using confocal Raman piezo-spectroscopy

Confocal Raman piezo-spectroscopy was applied to the non-destructive evaluation of residual stresses as they develop in a chemical-vapor-deposited Al 2O 3 coating on a Si 3N 4 ceramic substrate. According to a selected confocal configuration of the optical probe, with its focal plane set to in-depth scan the sample, the residual stress could be measured at various depths along the thickness of both coating and substrate. The residual stresses stored in the Al 2O 3 coating layer were measured using both the Cr 3+ fluorescence band, located at 14,400 cm −1 (R 1), and the Al 2O 3 Raman band at 417 cm −1. When the R 1 fluorescence band was used, no variation could be resolved for the residual stress along the coating depth direction; in contrast, a clear in-depth stress distribution was observed when the 417 cm −1 Raman band was used. The minimum stress magnitude was located at the coating external surface and the maximum at the coating/substrate interface. Given the high transparency of the Al 2O 3 coating, the residual stress field stored within the Si 3N 4 substrate could also be measured as a function of depth (according to the piezo-spectroscopic shift of the 206 cm −1 Raman band of Si 3N 4). A deconvolution procedure of confocal spectra was proposed, which is based on the knowledge of the probe response functions of both coating and substrate materials. Laser probe deconvolution enabled us to retrieve the actual in-depth stress distribution from the stress distribution experimentally observed by defocusing experiments.

207 加熱法によるパイプ溶接残留応力の非破壊評価 : 熱流速と残留応力の同時推定と解析的検証(OS6-1 非破壊評価と構造モニタリング,OS6 非破壊評価と構造モニタリング)

207 加熱法によるパイプ溶接残留応力の非破壊評価 : 熱流速と残留応力の同時推定と解析的検証(OS6-1 非破壊評価と構造モニタリング,OS6 非破壊評価と構造モニタリング)

Use of neutron and synchrotron X-ray diffraction for evaluation of residual stresses in a 2024-T351 aluminum alloy variable-polarity plasma-arc weld

The residual stress fields associated with variable-polarity plasma-arc (VPPA) welds in 2024-T351 aluminum alloy plates have been measured nondestructively using neutron and synchrotron X-ray diffraction. Neutron diffraction allows in-depth measurements of the full strain tensor to be made in thick components; synchrotron X-rays allow for rapid measurements of strains inside components, although their penetration is less than that of the neutrons and constraints arising from the diffraction geometry generally lead to only two strain components being easily measurable. Hence, a combination of the two techniques, applied as described herein, is ideal for a detailed nondestructive evaluation of residual stresses in plates. The residual stresses in a 12-mm-thick VPPA-welded aluminum 2024-T351 alloy plate have been measured using neutron diffraction. The stresses were then remeasured by a combination of neutron and synchrotron X-ray diffraction after the plate had been reduced in thickness (or, skimmed) to 7 mm by machining both sides of the weld, mimicking the likely manufacturing operation, should such welds be used in aerospace structures. A strong tensile residual stress field was measured in the longitudinal direction, parallel to the weld, in both the as-welded and skimmed specimens. There was only a slight modification of the residual stress state on skimming.

Magnetic Technique for Nondestructive Evaluation of Residual Stresses

A technique has been designed for measuring planar components of stray fields from ferromagnetic samples placed in a constant magnetizing field. The technique is based on recording the field of magnetization reversal of a thin magnetic film with the small coercive force being the sensor device of a microwave detector. The possibility of measuring the deformation inhomogeneities caused by mechanical treatment when manufacturing products from ferromagnetic materials is demonstrated. The results of the magnetic measurements agree with the data from X-ray diffraction analysis.

Thermoelectric Nondestructive Evaluation of Residual Stress in Shot-Peened Metals

This paper presents a noncontacting thermoelectric method that can be used to characterize the prevailing residual stress in shot-peened specimens. This novel method is based on magnetic detection of local thermoelectric currents in the compressed near-surface layer of metals when a temperature gradient is established throughout the specimen. Besides the primary residual stress effect, the thermoelectric method is also sensitive to the secondary “material” effects of shot peening (local texture, increased dislocation density, hardening), but it is entirely insensitive to its “geometrical” by-product, i.e., the rough surface topography. Our experimental results in copper indicate that the developed method is more sensitive to residual stress effects than to the secondary material effects, but unequivocal separation of residual stress relaxation from the parallel decay of secondary cold-work effects is generally not feasible. However, since the ratio of residual stress to cold work is primarily determined by the material and the specific surface treatment used, the thermoelectric method still offers the unique capability of nondestructively monitoring thermomechanical relaxation below the treated surface. Preliminary results on IN100 nickel-base superalloy are also presented to demonstrate that the proposed method might be applicable to a wide range of alloys including high-strength, high-temperature engine materials.

Thermoelectric Nondestructive Evaluation of Residual Stress in Shot-Peened Metals

This paper presents a noncontacting thermoelectric method that can be used to characterize the prevailing residual stress in shot-peened specimens. This novel method is based on magnetic detection of local thermoelectric currents in the compressed near-surface layer of metals when a temperature gradient is established throughout the specimen. Besides the primary residual stress effect, the thermoelectric method is also sensitive to the secondary ``material'' effects of shot peening (local texture, increased dislocation density, hardening), but it is entirely insensitive to its ``geometrical'' by-product, i.e., the rough surface topography. Our experimental results in copper indicate that the developed method is more sensitive to residual stress effects than to the secondary material effects, but unequivocal separation of residual stress relaxation from the parallel decay of secondary cold-work effects is generally not feasible. However, since the ratio of residual stress to cold work is primarily determined by the material and the specific surface treatment used, the thermoelectric method still offers the unique capability of nondestructively monitoring thermomechanical relaxation below the treated surface. Preliminary results on IN100 nickel-base superalloy are also presented to demonstrate that the proposed method might be applicable to a wide range of alloys including high-strength, high-temperature engine materials.

Thermoelectric Nondestructive Evaluation of Residual Stress in Shot-Peened Metals

Thermoelectric Nondestructive Evaluation of Residual Stress in Shot-Peened Metals

Nondestructive evaluation of residual stress for thermal barrier coated turbine blades by Cr3+ photoluminescence piezospectroscopy

Nondestructive evaluation of residual stress for thermal barrier coated turbine blades by Cr3+ photoluminescence piezospectroscopy

Residual Stresses in Steel and Zirconium Weldments

Three-dimensional scans of residual stress within intact weldments provide insight into the consequences of various welding techniques and stress-relieving procedures. The neutron diffraction method for nondestructive evaluation of residual stresses has been applied to a circumferential weld in a ferritic steel pipe of outer diameter 114 mm and thickness 8.6 mm. The maximum tensile stresses, 250 MPa in the hoop direction, are found at mid-thickness of the fusion zone. The residual stresses approach zero within 20 mm from the weld center. The residual stresses caused by welding zirconium alloy components are partially to blame for failures due to delayed hydride cracking. Neutron diffraction measurements in a GTA-welded Zr-2.5Nb plate have shown that heat treatment at 530°C for 1 h reduces the longitudinal residual strain by 60 percent. Neutron diffraction has also been used to scan the residual stresses near circumferential electron beam welds in irradiated and unirradiated Zr-2.5Nb pressure tubes. The residual stresses due to electron beam welding appear to be lower than 130 MPa, even in the as-welded state. No significant changes occur in the residual stress pattern of the electron-beam welded tube, during a prolonged exposure to thermal neutrons and the temperatures typical of an operating nuclear reactor.

Modeling the stress dependence of Barkhausen phenomena for stress axis linear and noncollinear with applied magnetic field (abstract)

The almost linear dependence of the maximum Barkhausen noise signal amplitude on stress has made it a tool for nondestructive evaluation of residual stress. Recently, a model has been developed to account for the stress dependence of the Barkhausen noise signal. The model uses the development of Alessandro et al. who use coupled Langevin equations to derive an expression for the Barkhausen noise power spectrum. The model joins this expression to the magnetomechanical hysteresis model of Sablik et al., obtaining both a hysteretic and stress-dependent result for the magnetic-field-dependent Barkhausen noise envelope and obtaining specifically the almost linear stress dependence of the Barkhausen noise maximum experimentally. In this paper, we extend the model to derive the angular dependence observed by Kwun of the Barkhausen noise amplitude when stress axis is taken at different angles relative to magnetic field. We also apply the model to the experimental observation that in XC10 French steel, there is an apparent almost linear correlation with stress of hysteresis loss and of the integral of the Barkhausen noise signal over applied field H. Further, the two quantities, Barkhausen noise integral and hysteresis loss, are linearly correlated with each other. The model shows how that behavior is to be expected for the measured steel because of its sharply rising hysteresis curve.

Non-destructive evaluation of residual stresses in hard metals (In German) : Schneider, E.; Kern, R. Fraunhofer-Gesellschaft zur Foerderung der Angewandten Forschung e.V., Munich (Germany), TIB/A91-00056/GAR, 25pp. (1988)

Non-destructive evaluation of residual stresses in hard metals (In German) : Schneider, E.; Kern, R. Fraunhofer-Gesellschaft zur Foerderung der Angewandten Forschung e.V., Munich (Germany), TIB/A91-00056/GAR, 25pp. (1988)