Role of Quantitative NDE Techniques in Life Management of Gas Turbine Components

2006 ◽  
Author(s):  
Michael Gorelik ◽  
Waled T. Hassan ◽  
Harry Kington
Keyword(s):  
Residual Stress ◽  
Stress Gradient ◽  
Surface Residual Stress ◽  
Major Barrier ◽  
Near Surface ◽  
Life Management ◽  
Surface Residual Stresses ◽  
Engine Components ◽  
Nondestructive Measurements ◽  
Non Destructive

A number of earlier publications discussed the benefits of probabilistic analysis and probabilistic lifing in application to critical rotating engine components. One of the important variables in both probabilistic and deterministic lifing analysis is the level of residual stress in the component. Near surface residual stresses directly influence the fatigue life of critical engine rotating components. Depending on sign and magnitude a near surface residual stress gradient can either inhibit or accelerate fatigue initiation and crack propagation. A major barrier to introducing subsurface residual stress information into the life calculation process is the necessity to make accurate and reliable nondestructive measurements on as produced hardware. The paper reviews several NDE technologies that could be candidates for both production and in-service non-destructive residual stress measurements. The importance of having accurate residual stress information and its use in the probabilistic design and life management process is illustrated on several examples. A linkage with several ongoing industry R&D programs is discussed.

Measurement of Near Surface Residual Stresses Using Electric Discharge Wire Machining

1994 ◽  
Vol 116 (1) ◽  
pp. 1-7 ◽  
Author(s):  
W. Cheng ◽  
I. Finnie ◽  
M. Gremaud ◽  
M. B. Prime
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Electric Discharge ◽  
Theoretical Approach ◽  
Stress Measurement ◽  
Stress Gradient ◽  
Experimental Results ◽  
Residual Stress Measurement ◽  
Near Surface ◽  
Surface Residual Stresses

In previous work it has been shown that near surface residual stresses may be deduced from surface strains produced by making a cut of progressively increasing depth. The process of electric discharge wire machining (EDWM), by providing very narrow cuts, greatly improves the ability of the method to resolve a stress gradient near the surface. However, the EDWM process may also introduce residual stresses. In the present work a model for estimating the influence of EDWM is presented, and a procedure for eliminating its effect on residual stress measurement is developed. Experimental results validate the theoretical approach.

Determination of Real Space Residual Stress Distributions σij(z) of Surface Treated Materials with Diffraction Methods Part II: Energy Dispersive Approach

2006 ◽  
Vol 524-525 ◽  
pp. 37-44 ◽  
Author(s):  
Ingwer A. Denks ◽  
Manuela Klaus ◽  
Christoph Genzel
Keyword(s):  
Residual Stress ◽  
Stress Gradient ◽  
Depth Resolution ◽  
Real Space ◽  
Stress Distributions ◽  
Surface Residual Stress ◽  
Multilayer Systems ◽  
Near Surface ◽  
Gauge Volume

The detection of near surface residual stress gradients in real space requires high depth resolution for any orientation of the diffraction vector with respect to the sample co-ordinate system. In order to meet this demand, the slits are no longer being fixed in the laboratory co-ordinate system as in strain scanning experiments but directly coupled with the sample. Hence, the gauge volume orientation within the sample remains constant and allows performing depth-resolved sin2ψ measurements in real space. The method’s accuracy is determined by the gauge volume definition, which is investigated in detail. Apart from the evaluation of the σ(τ) versus σ(z) relation, which is of fundamental interest in X-ray residual stress gradient analysis, the method will be shown to have a unique applicability in rather delicate sample geometries such as multilayer systems.

Sin2ψ-based residual stress gradient analysis by energy-dispersive synchrotron diffraction constrained by small gauge volumes. II. Experimental implementation

2013 ◽  
Vol 46 (3) ◽  
pp. 619-627 ◽  
Author(s):  
M. Meixner ◽  
M. Klaus ◽  
Ch. Genzel
Keyword(s):  
Residual Stress ◽  
Stress Gradient ◽  
Energy Dispersive ◽  
Narrow Slit ◽  
Surface Residual Stress ◽  
Near Surface ◽  
Experimental Implementation ◽  
Gauge Volume ◽  
Small Gauge ◽  
Residual Stress Gradient

On the basis of the theoretical concept for the use of small gauge volumes to study near-surface residual stress fields with high spatial resolution [Meixner, Klaus & Genzel (2013).J. Appl. Cryst.46, 610–618], the experimental implementation of the approach is demonstrated. It is shown that specifically designed slit systems are required to avoid effects such as diffuse scattering at the slit blades and total external reflection, both giving rise to a reduced resolution. Starting from the characterization of the small gauge volume, practical guidance on how to control the alignment of the sample relative to the gauge volume for different geometrical conditions of energy-dispersive diffraction is given. The narrow-slit configuration as well as the formalism for data evaluation introduced in the first part of this series is applied to the analysis of a very steep in-plane residual stress gradient in a shot-peened Al2O3ceramic sample. The results are compared with those obtained by means of a conventional wide-slit setup using the classical universal plot method for residual stress analysis on the one hand, and with the simulations performed in the first part on the other hand.

Micro-slotting technique for reliable measurement of sub-surface residual stress in Ti-6Al-4V

2018 ◽  
Vol 53 (6) ◽  
pp. 389-399 ◽  
Author(s):  
Elizabeth Burns ◽  
Joseph Newkirk ◽  
James Castle
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Image Correlation ◽  
X Ray Diffraction ◽  
Surface Residual Stress ◽  
Near Surface ◽  
X Ray ◽  
Measurement Volume ◽  
Surface Residual Stresses

Micro-slotting, a relaxation residual stress measurement technique, has recently been shown to be an effective method for measuring local residual stresses in a variety of materials. The micro-slotting method relies on a scanning electron microscope–focused ion beam system for milling and imaging, digital image correlation software to track displacements due to residual stress relaxation after milling, and finite element analysis for displacement–stress correlation and calculation of the original stress state in the imaged region. The high spatial resolution of the micro-slotting method makes it a promising technique for obtaining near-surface residual stress data in Ti-6Al-4V components for input into fatigue life models and crack growth simulations. However, use of the micro-slotting method on this alloy has yet to be evaluated against more established measurement techniques. In this study, spatially resolved sub-surface residual stress measurements were obtained on shot peened and low-stress surface-machined Ti-6Al-4V planar coupons using the micro-slotting method and were compared to measurements obtained using the conventional X-ray diffraction depth profiling technique. The sub-surface measurements were in good agreement for the shot peened sample. Observed differences in the measured near-surface residual stresses on the surface-machined sample were attributed to the larger measurement volume of the X-ray diffraction method, suggesting that the micron-sized measurement volume of the micro-slotting method may be more suitable for capturing shallow stress profiles and steep stress gradients. Prior to performing the micro-slotting measurements, finite element modeled displacements were used to verify the measurement procedure and to address uncertainties in the milled slot geometries. The results of this study demonstrated the validity of the micro-slotting procedure and established the technique as a reliable method for measuring sub-surface residual stresses in Ti-6Al-4V.

scholarly journals Comparison Between Surface and Near-Surface Residual Stress Measurement Techniques Using a Standard Four-Point-Bend Specimen

2021 ◽  
Author(s):  
S. Rahimi ◽  
I. Violatos
Keyword(s):  
Residual Stress ◽  
Strain Gauge ◽  
Measurement Techniques ◽  
Nominal Stress ◽  
Hole Drilling ◽  
Surface Residual Stress ◽  
Near Surface ◽  
Surface Residual Stresses ◽  
Drilling Technique ◽  
Strain Gauge Rosette

Abstract Background Determination of near-surface residual stresses is challenging for the available measurement techniques due to their limitations. These are often either beyond reach or associated with significant uncertainties. Objective This study describes a critical comparison between three methods of surface and near-surface residual stress measurements, including x-ray diffraction (XRD) and two incremental central hole-drilling techniques one based on strain-gauge rosette and the other based on electronic speckle pattern interferometry (ESPI). Methods These measurements were performed on standard four-point-bend beams of steel loaded to known nominal stresses, according to the ASTM standard. These were to evaluate the sensitivity of different techniques to the variation in the nominal stress, and their associated uncertainties. Results The XRD data showed very good correlations with the surface nominal stress, and with superb repeatability and small uncertainties. The results of the ESPI based hole-drilling technique were also in a good agreement with the XRD data and the expected nominal stress. However, those obtained by the strain gauge rosette based hole-drilling technique were not matching well with the data obtained by the other techniques nor with the nominal stress. This was found to be due to the generation of extensive compressive residual stress during surface preparation for strain gauge installation. Conclusion The ESPI method is proven to be the most suitable hole-drilling technique for measuring near-surface residual stresses within distances close to the surface that are beyond the penetration depth of x-ray and below the resolution of the strain gauge rosette based hole-drilling method.

Study Progress on Grinding Surface Residual Stresses for Nano-Ceramic Coatings

2013 ◽  
Vol 753-755 ◽  
pp. 277-280 ◽  
Author(s):  
Wei Xiang Liu
Keyword(s):  
Residual Stress ◽  
High Hardness ◽  
Ceramic Materials ◽  
Ceramic Coatings ◽  
Grinding Process ◽  
Monitoring And Control ◽  
Surface Residual Stress ◽  
Surface Residual Stresses ◽  
Process Monitoring And Control ◽  
Grinding Mechanism

Nano-ceramic materials had high hardness and wear resistance. Combined with current technology and cost saving, nanostructured coatings technology were carried out, using HVOF ( high velocity oxygen fuel) or plasma spraying technique can obtain high quality ceramic coating on metal substrate. Ceramic coatings produced cracks in the grinding due to grinding surface residual stress. the coatings grinding surface residual stress of engineering ceramics have been researched, grinding surface residual stress in the nanostructured ceramic coatings are being researched. the researches in this field include grinding process modeling, abrasives and grinding parameters, grinding process monitoring and control and realization of the software, the grinding mechanism and grinding damage on the surface, grinding force prediction, on-line detection, grinding on nanocoating material is a multivariable complex process.

Non-destructive Surface Residual Stress Profiling by Multireflection Grazing Incidence X-Ray Diffraction: a 7050 Al Alloy Study

2020 ◽  
Vol 60 (4) ◽  
pp. 475-480
Author(s):  
V. A. N. Righetti ◽  
T. M. B. Campos ◽  
L. B. Robatto ◽  
R. R. Rego ◽  
G. P. Thim
Keyword(s):  
Residual Stress ◽  
Grazing Incidence ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
Surface Residual Stress ◽  
X Ray ◽  
Non Destructive
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