Residual stress measurement using the slitting method via a combination of eigenstrain, regularization and series truncation techniques

Salehi, Saba; Shokrieh, M.M.

doi:10.1016/j.ijmecsci.2019.01.011

Cited by 23 publications

(13 citation statements)

References 33 publications

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“…Typical methods for solving the inverse problem enforce some smoothing to handle noise in the strain data, but here the discontinuity should not be smoothed. Various inverse methods have been used to allow for discontinuities across layers with this type of inverse problem [39][40][41][42][43]. We chose the pulse-regularization method [44], which handles noisy data robustly and can handle a discontinuity with a simple adaptation.…”

Section: Analysis Methodsmentioning

confidence: 99%

“…The pulse-regularization methodology for layers from [41,46] is reviewed, starting with the traditional pulse-regularization method [44] before moving onto the formulation that allows for discontinuities. Before adding regularization, the pulse method is equivalent to the "integral method," historically used for hole drilling [47].…”

Section: Pulse-regularization With Allowance For Discontinuitiesmentioning

confidence: 99%

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Residual Stress Measurements in Extreme Environments for Hazardous, Layered Specimens

et al. 2022

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Background In nuclear fuel plates of low-enriched U-10Mo (LEU) clad with aluminum by hot isostatic pressing (HIP), post-irradiation stresses arising during reactor shutdown are a major concern for safe reactor operations. Measurement of those residual stresses has not previously been possible because the high radioactivity of the plates requires handling only by remote manipulation in a hot cell. Objective The incremental slitting method for measuring through-thickness stress profiles was modified, and a system for automated, remote operation was built and tested. Methods Experimental modifications consisted of replacing electric-discharge machining (EDM) with a small end mill and strain-gauge measurements with cantilever displacement measurements. The inverse method used to calculate stresses was the pulse-regularization method modified to allow discontinuities across material interfaces. The new system was validated by comparing with conventional slitting on a depleted U-10Mo (DU) fuel plate. Results The new system was applied to two measurements each on six as-fabricated (pre-irradiation) LEU miniature fuel plates. Variations between the measurements at two locations in the same plate were strongly correlated with measured geometrical heterogeneity in the plate—a tilt in the fuel foil. Compressive stresses in the U-10Mo were shown to increase from 20 to 250 MPa as the ratio of aluminum thickness to U-10Mo thickness increased causing increased constraint during cooling. Faster cooling rates during processing also increased stress magnitudes. Conclusions The measurements trends agreed with data in the literature from similar plates made with DU, which further validates the method. Because other methods are impractical in a hot cell, the modified slitting method is now poised for the first measurements of post-irradiation stresses.

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Section: Analysis Methodsmentioning

confidence: 99%

Section: Pulse-regularization With Allowance For Discontinuitiesmentioning

confidence: 99%

Residual Stress Measurements in Extreme Environments for Hazardous, Layered Specimens

et al. 2022

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“…In recent years, the subject of the study experienced a regression—especially since the available measurement and numerical technique [ 16 , 17 ] allows for efficient estimation of stress levels. One of the most widespread experimental methods is the slitting method [ 6 , 18 , 19 , 20 ] which is used as a primary investigation method in the presented paper. In the light of the works [ 14 , 15 ], the nature of the process optimization possibilities arises, not so much from a change in the isothermal conditions of the cooling, but from a process medium that allows receiving heat at different speeds, thus clearly influencing the overall cooling conditions.…”

Section: Introductionmentioning

confidence: 99%

The Mechanical Investigation of Filament-Wound CFRP Structures Subjected to Different Cooling Rates in Terms of Compressive Loading and Residual Stresses—An Experimental Approach

et al. 2021

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Although cooling at ambient temperature is widely used and is said to be safe and convenient, faster cooling may have an influence not only on the time of the manufacturing process but also on the mechanical response, especially the residual stress. The study aimed to investigate the influence of the cooling rate after curing on the mechanical response of filament-wound thick-walled carbon fiber reinforced polymer (CFRP) rings. Three cooling rates were taking into consideration: cooling with the oven, at room temperature, and in the water at 20 °C. The splitting method was used to examine the residual strains. In the radial compression test, the mechanical response was investigated between the rings with different cooling regimes. The FEM analysis of the compression test in elastic range was also performed. Both the splitting method and the radial compression test showed no significant difference in the mechanical response of the CFRP rings. The presented results showed that the fast-cooling rate slightly decreases the mechanical performance of the filament-wound rings.

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“…The slitting method has been successfully extended to layered and composite materials [6], and utilizing pulse functions or piecewise polynomials resolves impediments to the use of this method for materials containing discontinuous residual stress fields [7]. In recent years, eigenstrain as the source of the residual stresses has also been utilized to obtain the residual stresses for both isotropic [8,9] and composite materials [10,11].…”

Section: Introductionmentioning

confidence: 99%

Full-Field Measurement of Residual Stresses in Composite Materials Using the Incremental Slitting and Digital Image Correlation Techniques

et al. 2020

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Background The slitting method is a widely used destructive technique for the determination of residual stresses. Because of the rich data content of the full-field methods, optical techniques such as digital image correlation (DIC) are replacing strain gages for surface measurements. Objective The objective of the current paper is to overcome the difficulties that arise in using the DIC technique combined with the slitting method. The present noise, low signal-to-noise ratio, and systematic errors are the main impediments to the use of DIC in the slitting method. Methods An approach based on the eigenstrain concept was exploited to ascertain the optimum region of interest (ROI) for the analysis. After that, a robust procedure was implemented to utilize the DIC method while excluding the rigid body motion and rotation artifacts from the obtained displacements. Results Different slitting steps may cause dissimilar rigid body motions and rotations of the specimen. The proposed method was able to eliminate all of these different shears and stretches in the images simultaneously. The slitting experiment was conducted on a symmetric cross-ply composite specimen, and the slit progressed down to half the thickness. Although some rigid body motions were large, the method managed to exclude all of them for eight slitting steps. Conclusion A comparison made between the results of the current method and those of the strain gage technique shows that they are in acceptable agreement with each other, and this full-field method can be extended to smaller scales or other destructive techniques.

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Residual stress measurement using the slitting method via a combination of eigenstrain, regularization and series truncation techniques

Cited by 23 publications

References 33 publications

Residual Stress Measurements in Extreme Environments for Hazardous, Layered Specimens

Residual Stress Measurements in Extreme Environments for Hazardous, Layered Specimens

The Mechanical Investigation of Filament-Wound CFRP Structures Subjected to Different Cooling Rates in Terms of Compressive Loading and Residual Stresses—An Experimental Approach

Full-Field Measurement of Residual Stresses in Composite Materials Using the Incremental Slitting and Digital Image Correlation Techniques

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