Hole-Drilling Method in Residual Stress Diagnostics

Relieved strains due to drilling hole in a ring sample cut from an autofrettage cylinder are measured. Measured strains are then transformed to residual stresses using calibration constants and mathematical relations of elasticity based on ASTM standard recommendations (American Society for Testing and Materials, ASTM E 837-08, 2008, “Standard Test Method for Determining Residual Stresses by the Hole-Drilling Strain-Gage Method,” American Society for Testing and Materials). The hydraulic autofrettage is pressurizing a closed-end long cylinder beyond its elastic limits and subsequently removing the pressure. In contrast to three-dimensional stress state in the autofrettage tube, the stress measurement in hole drilling method is performed on a traction free surface formed from cutting the ring sample. The process of cutting the ring sample from a long autofrettaged tube is simulated using finite element method (FEM) and the redistribution of the residual stress due to the cut is discussed. Hence, transformation of the hole drilling measurements on the ring slice to the autofrettage residual stresses is revealed. The residual stresses are also predicted by variable material properties (VMP) method (Jahed, H., and Dubey, R. N., 1997, “An Axisymmetric Method of Elastic-Plastic Analysis Capable of Predicting Residual Stress Field,” Trans. ASME J. Pressure Vessel Technol., 119, pp. 264–273) using real loading and unloading behavior of the test material. Prediction results for residual hoop stress agree very well with the measurements. However, radial stress predictions are less than measured values particularly in the middle of the ring. To remove the discrepancy in radial residual stresses, the measured residual hoop stress that shows a self-balanced distribution was taken as the basis for calculating residual radial stresses using field equations of elasticity. The obtained residual stresses were improved a lot and were in good agreement with the VMP solution.

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Incremental Hole-Drilling Method Vs. Thin Components: A Simple Correction Approach

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.996.283 ◽

2014 ◽

Vol 996 ◽

pp. 283-288 ◽

Cited By ~ 4

Author(s):

Esther Held ◽

Simone Schuster ◽

Jens Gibmeier

Keyword(s):

Residual Stress ◽

Thin Metal ◽

Hole Drilling ◽

Depth Profiles ◽

Hole Drilling Method ◽

Incremental Hole Drilling ◽

Metal Sheets ◽

Drilling Method ◽

Measured Strain ◽

The Impact

The incremental hole-drilling method is a widely used technique to determine residual stress depth profiles in technical components. Its application is limited in respect to the components geometry, for instance the components thickness. In this paper, a direct correction of the measured strain relaxations is proposed to consider the impact of deviant geometries, here the component thickness, on the residual stress evaluation that moreover, allows the application of commercially available evaluation software. The herein proposed approach is based on finite element simulation of the incremental hole drilling. The simulated strain relaxations for thin metal sheets are evaluated with an algorithm as used in commercially available evaluation software (i) for uncorrected data as well as (ii) for strain data corrected by the proposed correction procedure. It is shown that the correction approach leads to a significant improvement of the measurement accuracy. Further, by means of the approach residual stress depth profiles in thin metal sheets can be as usual determined using commercial evaluation software for the incremental hole-drilling method regardless of the algorithm used, i.e. differential or integral.

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Achievements in Micromagnetic Techniques of Steel Plastic Stage Evaluation

Advances in Materials Science ◽

10.2478/adms-2020-0002 ◽

2020 ◽

Vol 20 (1) ◽

pp. 16-55 ◽

Cited By ~ 1

Author(s):

M. F. de Campos

Keyword(s):

Residual Stress ◽

Plastic Deformation ◽

Elastic Deformation ◽

Magnetic Measurements ◽

Soft Magnetic Materials ◽

Hysteresis Curve ◽

Hole Drilling ◽

Hole Drilling Method ◽

Drilling Method ◽

The Difference

AbstractThe investigation of plastic deformation and residual stress by non-destructive methods is a subject of large relevance for the industry. In this article, the difference between plastic and elastic deformation is discussed, as well as their effects on magnetic measurements, as hysteresis curve and Magnetic Barkhausen Noise. The residual stress data can be obtained with magnetic measurements and also by the hole drilling method and x-ray diffraction measurements. The residual stress level obtained by these three different methods is different, because these three techniques evaluate the sample in different depths. Effects of crystallographic texture on residual stress are also discussed. The magnetoelastic term should be included in micromagnetic methods for residual stress evaluation. It is discussed how the micromagnetic energy Hamiltonian should be expressed in order to evaluate elastic deformation. Plastic deformation can be accounted in micromagnetic models as a term that increases the coercive field in soft magnetic materials as the steels are.

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