Residual Stress Measurement Methods Research Articles

The development of tools and methods to manage residual stresses in the future design of nuclear plant

A long-term UK research programme [1–3] on residual stresses was launched in 2004. It involves Rolls-Royce plc and Serco Assurance, supported by UK industry and academia. The programme involves the use of finite element analysis to simulate welding processes and supporting experimental validation [4] using a variety of residual stress measurement techniques. This programme is aimed at progressing the understanding of residual stresses in nuclear plant components, whilst developing weld modelling analysis tools and residual stress measurement methods. These analysis tools will then be used to develop strategies to minimise welding residual stresses and distortions in the design and manufacture of future plant. This paper describes the research that has been carried out to date and the tools and methods which are currently being used and developed to assist the engineer in determining the residual stress distribution in welded components as required by assessment procedures such as BS7910 [5], R6 [6] and FITNET [7].

Quantitative Thermographic Methodology for fatigue assessment and stress measurement

The Thermographic Method, which takes temperature increment as the fatigue indicator, enables to predict the fatigue limit of materials and mechanical components in a relative short time. This research paper advances this Quantitative Thermographic Method for residual fatigue life assessment and nonlinear stress measurement. The developed approach was used to assess the fatigue parameters (fatigue limit, S– N curve, residual fatigue life, applied stress) of a mild steel A36, achieving good predictions. Moreover, the lock-in thermographic technique was applied for analysis of stress concentration zones to specimens, made of the same steel, with central flat-bottom hole.

Dual-Axis Hole-Drilling ESPI Residual Stress Measurements

A novel dual-axis ESPI hole-drilling residual stress measurement method is presented. The method enables the evaluation of all the in-plane normal stress components with similar response to measurement errors, significantly lower than with single-axis measurements. A numerical method is described that takes advantage of, and compactly handles, the additional optical data that are available from the second measurement axis. Experimental tests were conducted on a calibrated specimen to demonstrate the proposed method, and the results supported theoretical expectations.

Residual stress measurement method in MEMS microbeams using frequency shift data

The dynamical behaviour of a set of gold microbeams affected by residual stress has been studied. Experimental frequency shift curves were obtained by increasing the dc voltage applied to the specimens. Comparison with different analytical and numerical models has been carried out in order to identify both analytical and finite element models in the presence of residual stress. Residual strain and stress, due to the fabrication process, have been widely reported in the literature in both out-of-plane microcantilevers and clamped–clamped microbeams by using mainly the value of pull-in voltage and static deflection data. In the case of a microcantilever, an accurate modelling includes the effect of the initial curvature due to microfabrication. In double-clamped microbeams, a pre-load applied by tensile stress is considered. A good correspondence is pointed out between measurements and numerical models so that the residual stress effect can be evaluated for different geometrical configurations.

D-68 Application of Different Methods for Residual Stress Measurement of a Casting Component of an EN-AC 44000 Alloy

D-68 Application of Different Methods for Residual Stress Measurement of a Casting Component of an EN-AC 44000 Alloy

Improvement of magnetic residual stress measurements based on Fourier transform

A more convenient magnetic residual stress measurement method was proposed with an improved data processing method using a Fourier transform. The effects of demagnetisation, grinding and excitation frequency were also investigated. It is found thati) the application of a Fourier transform makes the rotation of the magnetic probe redundant and leads to more convenient stress measurementsii) residual magnetisation exerts a great influence on the measurement results and thus demagnetisation is necessary for more accurate measurementsiii) the stress measurement depth can be adjusted by altering the excitation frequency. The authors' investigation provides a more convenient magnetic stress measurement method.

Correction of errors introduced by hole eccentricity in residual stress measurement by the hole-drilling strain-gage method

The accuracy of the hole-drilling strain-gage technique, the most widely used method for residual stress measurement, is directly related to: (1) the eccentricity between the hole center and rosette center, respectively, and (2) the accuracy of corrections for integration tendency of the strain gages. Although the drilling tool is optically aligned, the eccentricity always cannot be zero and it is a source of error, affecting the accuracy of this technique. An equation for correction of the data affected by hole eccentricity has been proposed by A. Ajovalasit, but it is not precise enough, because it is founded on the wrong hypothesis that in the strain-gage area there is a uni-axial state of stress, instead bi-axial one. The paper presents a new equation for data correction, which take account of the plane (bi-axial) state of stress in the strain-gages area. After the hole drilling and data acquisition, the hole eccentricity will be measured, using an optical microscope. Knowing the eccentricity, the data will be corrected using the proposed equation. This equation is more precise, because it is founded on a realistic hypothesis (bi-axial state of stress in the strain-gages area).

An alternative micro-area X-ray diffraction method for residual stress measurement of Pb(Zr,Ti)O 3 film

An alternative X-ray diffraction method for micro-area residual stress measurement was proposed by means of the analysis of a single diffraction ring, which was performed on a laboratory X-ray microdiffraction system equipped with a 2D planar detector. The microdiffraction experiments were employed to evaluate the residual stress in sol–gel-derived Pb(Zr,Ti)O 3 film before and after Ag electrode deposition. The tensile stresses of about 2.3 GPa and 1.2 GPa were calculated in the micro-area of film without and with electrode, which was related to a top electrode stress relaxation effect.

Comparison of methods of residual-stress measurement

Methods used for the measurement of stresses in pipelines operating under conditions favorable to development of stress-induced corrosion cracking are compared.

RESIDUAL STRESS ESTIMATION OF BONE TISSUE USING X-RAY IMAGING TECHNIQUE

INTRODUCTION X-ray diffraction residual stress measurement method has shown that bone possesses some inherent stress as ‘residual stress’ [1]. In more advanced application of X-ray diffraction, two-dimensional detectors called imaging plate are being used to obtain the diffracted Debye rings directly. These Debye rings are distorted by stress and the degree of distortion gives the basis for strain measurement.

Evaluation of Residual and Actual Stress Levels of Steel Columns in Existing Building Structures due to Working Loads

A wide variety of residual stress measurement methods can be used to measure the axial stress in a column. One of the most widely used techniques for measuring residual stress is slotting method since it is relatively simple and cost-effective to implement at vertical columns in field. However, the slotting method is considered to be semi-destructive or destructive method depending on the amount of material to be removed. Therefore, in this paper, optimal depth of slots for measuring actual stress is presented to minimize the amount of material to be removed. Finite element method is used to estimate the minimum depth of the slot in H-shaped steel column. By performing actual saw cutting, optimality of the simulated depth of the slot is investigated.

Sensitivity analysis of full field methods for residual stress measurement

The hole drilling technique is a well known experimental method for residual stress investigation. This technique is usually used in combination with electrical strain gauges but there is no reason to enforce this choice and other approaches, in particular some full-field optical techniques, can be advantageously used. Since all these techniques give full field data, it becomes important to properly use this redundant information content to increase the robustness and reliability of the analysis. In this work, various well known approaches to the hole drilling/full-field data analysis will be investigated using a two-step approach. In the first one, a sensitivity analysis will be performed on the simpler algorithms and then the reliability of the methods will be estimated by Montecarlo analysis using a known displacement field as a reference.

Deep Hole Drill Residual Stress Measurement Technique Experimental Validation

This paper presents the results of an experimental validation of the deep hole drill residual stress measurement method. A validation test specimen was fabricated and plastically loaded to impose a permanent residual stress field within the specimen. The validation test specimen was designed to provide a variety of stress profiles as a function of location within the specimen. A finite element analysis of the validation test specimen was performed in order to provide a reference solution for comparison to the deep hole drill experimental results. Results from experimental testing of the validation test specimen agree well with the finite element analysis reference solution, thereby providing further validation of the deep hole drill method to measure residual stresses.

A Wet Etching Method Coupled With Finite Element Analysis-Based Compliance Function to Determine Residual Stress in High-Speed Milling

High-speed milling (HSM) is widely used in the automotive and aerospace industries in fabricating mechanical components. HSM induced residual stress may significantly impact fatigue life and the corrosion resistance of machined components. Traditional methods of residual stress measurement are very time consuming and expensive. In this paper we presents a wet etching approach to obtain strain as a function of slot depth introduced in the subsurface. The strain readings were collected from a strain gauge mounted on the specimen surface near the slot edge. A compliance function can be conveniently calculated by simulating slot cutting using a finite element method via a Legendre polynomial subroutine as the applied load. The calculated compliance functions and measured strain values at different depths were used as inputs into a program to calculate residual stress. This leads to a faster and less expensive method of determining residual stress when compared with the traditional methods. The capability of this new approach was demonstrated by high-speed milling 6061-T651 and 7050-T7451 aluminum alloys. A design-of-experiment method was used to conduct milling tests with three levels of cutting speed, feed rate, and DOC. Residual stress profiles with 12 data points with the spatial resolution as small as 1μm in the subsurface were then obtained. Residual stress sensitivity to cutting conditions was investigated. In addition, subsurface microstructure and microhardness were also measured to characterize surface integrity in a broad sense.

An advanced method for measuring the residual stress of deposited film utilizing laser spallation technique

Residual stress of thin diamond films deposited by chemical vapor deposition (CVD) method was measured using a new method for residual stress measurement we developed. Compressive residual stresses of CVD diamond films were determined from the height and diameter of protuberance of film delaminated by pulse laser spallation technique. We produced the protuberance with different diameter and height by changing the laser energy. Compressive stresses were calculated from the momentum balance of atmospheric pressure and internal compressive force of the film. The residual stress of the well-faceted diamond film was measured as −338±22 MPa and agreed well with the stress (−348±17 MPa) measured by the X-ray diffraction method. In three other polycrystalline diamond films with different grain structure, the compressive stresses decreased from 300 to 147 MPa with decreasing the grain size from a few microns to tens of nanometers. Small compressive stresses of fine grain films are correlated with the grain boundary structure according to visible Raman spectra study conducted.

引張り矯正による金極細線の直進性改善

With the recent advances in the semiconductor industry, the demand for gold, copper and aluminum bonding wires has been increasing. Wire diameter has been decreasing due to the market demand for small and highly functional products. Also, a high degree of wire straightness is required to prevent short-circuit defects caused by contact between looped wires. Although methods of improving the straightness of superfine wires by tensile straightening have been examined, the number of such studies is limited and the mechanism of improving the straightness of wires has not yet been clarified. In this study, tensile straightening was carried out for superfine gold wires to examine the change in wire straightness under various conditions. We proposed a residual stress measurement method that allows us to quantitatively measure the residual stress in a wire specimen, which obtained by removing a part of the wire using a focused ion beam (FIB). We also demonstrated the relationship between straightness and residual stress. Furthermore, the effect of tensile strain on the crystalline structure was examined to clarify the effect of the tensile strain on the straightness of the wire and the crystal orientation rate.

Effect of Geometry and Materials on Residual Stress Measurement in Thin Films by Using the Focused Ion Beam

Recently, a new method for residual stress measurement in thin films by using the focused ion beam (FIB) has been proposed by the authors. It is based on the combined capability of the FIB imaging system and of high-resolution strain mapping software (VIC-2D). A simple equation based on two-dimensional elasticity is used to evaluate the residual stress from the displacements due to introducing a slot. The slot length is assumed to be much larger than the slot width or depth. And the effect of the slot width was neglected. However, it is often hard, depending on film materials, to introduce a narrow and deep slot by FIB. In this work some practical issues regarding the slot geometry are addressed. Through two- and three-dimensional finite element analyses, it is explored how the slot length, width and measurement location affect the displacements which are the basic data for residual stress evaluation. As a result, the validity and limit of the equations based on two-dimensional elasticity are evaluated. Also, the effect of material dissimilarity between film and substrate is explored. Finally, examples for a diamond-like carbon film on glass substrate and an aluminum oxide film thermally grown upon an alloy are presented.

A new residual stress measurement method using ultra-wide micromachined bilayer cantilevers

A new method is proposed to improve thin-film stress measurement using micromachined bilayer cantilevers. Our previous studies demonstrated that the width does affect the bilayer cantilever deflection, and the effect of width disappears as the width exceeds a critical value, which is usually far larger than the bilayer cantilever length. The existing methods, which employ the narrow micromachined bilayer cantilever to measure the residual stresses, do not consider the width effect, and hence may generate some uncertainties in their measurement results. To remove these uncertainties, a cantilever with a very large width is introduced and used in this proposed method. Its corresponding model, based on the plate theory, has been derived and applied to this new measurement procedure. Following the measurement procedure suggested in this paper would provide measurement results more reliable than the traditional ones which use the narrow bilayer cantilever in determining the stresses of thin films.

放射光および中性子回折法による実用材料の応力評価法の開発(S06-2 材料内部の非破壊応力評価,S06 放射光による応力測定と残留応力評価)

The purpose of this study is development of residual stress measurement method which can observe the residual stress distributions on the practical materials accurately using synchrotron radiation and neutron diffraction. Welded specimen was fabricated by using SNC631 steel, and then the residual stress distributions of this sample was measured by using both sources. Residual stresses measured using both sources were almost correlated by solving the problems such as the systematic error, statistical error, and so on. On the other hand, the residual stresses near the weld zone were different between surfaces and inside. Therefore, it was considered that the large stress gradient was existed near the weld zone.

Validation of the Contour Method of Residual Stress Measurement in a MIG 2024 Weld by Neutron and Synchrotron X-ray Diffraction

The contour method is a newly-invented destructive technique of residual stress measurement and has been receiving increasing interest. It is advisable to validate such new methods by comparison with other well-established techniques. For this purpos