Non-destructive Residual Stress Measurement Research Articles

Non-Destructive Hardness Indentation Measurement of Residual Stress on Large Aerospace Forged Components at the Engineering Site Based on Impact Hardness Tester.

Large forgings are crucial in aerospace applications; however, the residual stresses generated during their forming and heat treatment seriously affect their serviceability. Therefore, the non-destructive detection of residual stresses in large forgings is of far-reaching significance for ensuring the quality of forgings and realising precision machining. Although a variety of detection methods are available, there is still a lack of a programme that can comprehensively, accurately and non-destructively measure the residual stresses in large forgings. This study is dedicated to exploring the application of the bouncing impact indentation method in the non-destructive testing of residual stresses in large forgings. Through in-depth finite element simulations and orthogonal scheme analyses, we found that the elastic modulus, yield strength and work hardening indexes have significant effects on the impact indentation process. Further, we establish the dimensionless function of residual stress and indentation parameters, and successfully obtain the inversion algorithm of residual stress. The relative error of the calculated values of the indentation curves hm and hr in the simulation with reference values is not more than 3%, and the relative error of the corrected Pm inversion values for most virtual materials is not more than 5%. The folding elastic modulus and apparent elastic modulus obtained by inversion are controlled within 10%, which demonstrates a high value for engineering applications. In addition, we innovatively express the research results in the form of 3D stress diagrams, realising the digital expression of 3D residual stresses in large forgings based on feature point measurements and contour surface configurations, which provides intuitive and comprehensive data support for engineering practice.

UltraMARS system for non-destructive measurement of residual stresses: New developments

UltraMARS system for non-destructive measurement of residual stresses: New developments

Comparison of Non-Destructive Residual Stress Measurement Methods for Additive Manufactured Alsi10mg Alloys

Comparison of Non-Destructive Residual Stress Measurement Methods for Additive Manufactured Alsi10mg Alloys

Measurement Method of Internal Residual Stress in Plastic Parts Using Terahertz Spectroscopy

Since internal residual stress in polymers causes dimension errors over time, a measurement method for residual stress in polymers, especially in opaque engineering plastics, is strongly required. In this study, we propose to utilize terahertz (THz) spectroscopy to non-destructively measure internal residual stress in polymers. To verify the validity of the proposed method, we manufactured polytetrafluoroethylene ring samples with and without residual stress, and studied them with THz time domain spectroscopy system. THz spectra of samples without residual stress showed almost no polarization difference, whereas spectra of samples with residual stress showed clear polarization difference. Dimension changes between the samples with and without residual stress were also estimated and it was found that the change had a correlation with THz polarization difference. These experimental analyses confirm the validity for the proposed non-destructive measurement of residual stress in polymer.

Kontrolisanje zaostalih napona - razvoj najnovijih inženjerskih metoda za merenje bez razaranja i povoljnu preraspodelu zaostalih napona

Welding is used widely in the automotive industry for joining a variety of structural components and parts. Of paramount importance in these structures are their engineering properties, such as fatigue life, distortions, dimensional stability and corrosion resistance that can be affected considerably by the presence of residual stresses (RS). The knowledge of RS and the ability to control their distribution in welded structures is critical when evaluating their fatigue life and preventing catastrophic failures. An engineering concept of residual stress management (RSM) has been developed that addresses all aspects of residual stresses in structural elements. RSM includes three major stages in stress management, i.e. RS determination, RS analysis and RS redistribution. Using this approach, stresses in structures and materials can be evaluated in each specific case either theoretically or experimentally and the performance and fatigue behavior of such structures optimized. This paper is built as an overview of the RSM concept and its application in the fields of non-destructive measurement of residual and applied stresses and in treatment of structures with residual stresses to achieve better performance and longer fatigue life. All three stages of the RSM concept will be discussed and for each of the stages practical engineering approach examples will be given. An example of a project in which the residual stress distribution in a filet welded joint was measured, analyzed and changed by post-weld treatment will be presented to demonstrate the effectiveness of the RSM approach. The advancements in the modern tools used in this project for non-destructive measurement of residual stresses using an ultrasonic computerized complex for residual stress measurement and the ultrasonic peening for redistribution of the residual stresses that allowed improving the quality of the welds and increasing their fatigue life will also be presented.

Influence of the Measurement Parameters on Depth-Resolved Residual Stress Measurements of Deep Rolled Construction Steel using Energy Dispersive X-ray Diffraction

Abstract In this study, the influence of different measurement parameters of energy dispersive residual stress measurements on the obtained residual stress depth profiles of deep rolled construction steel S355 G10+M was investigated. Especially the diffraction angle θ and afterwards the measuring time t per inclination angle ψ were varied. A diffraction angle of θ = 20° shows an acceptable compromise between achievable information depth and detected total intensity of diffracted X-ray quanta. Furthermore, a measuring time per inclination angle ψ of t = 2,400 s leads to an acceptable standard deviation regarding the determined residual stress states. With these parameters for the energy-dispersive measurement, a comparison between angle-dispersive and energy-dispersive determination of residual stress depth profiles was carried out. Quantitative similarities between these two methods were observed, whereby the energy-dispersive determined residual stress depth profiles are rather discontinuous. A possible explanation could be found in the model used for the calculation of the net-plane-dependent radiographic elastic constants (XEC). In general, the energy-dispersive residual stress measurement was qualified for the determination of residual stress depth profiles of deep rolled construction steel. Based on the findings, a time-efficient non-destructive residual stress measurement can be carried out in the future with the discussed measurement parameters at maximum possible information depth.

The Effect of Low Temperature Range Heat Treatment on the Residual Stress of Cold Gas Dynamic Sprayed Inconel 718 Coatings via Neutron Diffraction

There has been considerable interest in the application of cold gas dynamic spray (CGDS) to deposit nickel-based superalloy coatings for the repair and development of high-value components that operate under extreme environmental conditions. The CGDS process introduces residual stresses in the coating layers, but inherently effects the subsurface of the substrate in a similar manner. The present study investigates the effect of low temperature range heat treatments (100-400 °C) on the residual stress of CGDS Inconel® 718 deposited onto a presolution-treated Al7075-T651 substrate. High spatial resolution nondestructive residual stress measurements were carried out via neutron diffraction on both the CGDS deposit and substrate. The low temperature range heat treatments displayed a significant effect on both the substrate and coatings. Residual stress relaxation was exhibited in coatings that were heat-treated at the lowest temperature, whereas an increased heat treatment temperature displayed an opposite effect, increasing both the compressive residual stress in the IN718 coating and the residual tensile stress in the substrate. It is proposed the difference in thermal expansion coefficient of the two materials was the main factor responsible for the residual stresses. The effect of post-heat treatment on coating microhardness and porosity is also presented.

Determining Prestrains in an Elastomer Through Elliptical Indentation

Residual stresses or prestrains could strongly affect the properties and functionalities of soft materials and tissues. However, non-destructive measurements of residual stresses or prestrains in materials are generally challenging. Previous studies have shown that residual stresses or prestrains can affect indentation tests of different materials, including metals, glassy polymers, soft elastomers, and gels. Nevertheless, an indentation method for determining the state of residual stresses or prestrains of large magnitude in an elastomer is not yet available. In this article, we propose to use elliptical indentation to measure large prestretches in a Neo-Hookean elastomer. We have analytically derived the relationship between the indentation force and indentation depth for both a flat-ended elliptical indenter and an ellipsoidal indenter. We have further shown that such a relationship greatly depends on the rotational angle of the indenter with respect to the direction of principle stretches in the elastomer. Based on the derived analytical results, we construct two diagrams for the flat-ended elliptical indenter and ellipsoidal indenter, respectively, which can be directly used to determine quantitatively large prestrains in an elastomer.

Novel applications of centreless X-ray diffractometers for non-destructive pole figure measurements

Centreless X ray diffractometers are specially designed for non-destructive residual stress measurements. The similarity between the X-ray diffraction-based stress and texture measurement methods led us to introduce a new method on non-destructive (sample cutting-free) stress measurement devices to studies on crystallographic texture. The method that determines texture characteristics from residual stress data has recently been introduced. Afterwards, a method with which pole figures (fully equivalent to conventionally measured pole figures) at high Bragg-angles can be constructed with centreless diffractometers were developed. The paper gives an illustration of the new methods’ utilization on the field of archaeometry. In that area, only non-destructive testing modes are permitted. In the case of archaeological finds, knowing the crystallographic texture assists to reconstruct the ancient process technology (hammering, rolling, annealing) that was applied during the manufacturing. The new methods are suitable to be used on valuable and unique objects both in the automotive industry, archaeometry and in the space applications.

Robotic Ultrasonic Measurement of Residual Stress in Complex Curved Surface Components.

The automatic measurement, especially for products with complex shapes, has always been one of the most important application areas of robots. Aiming at the challenge of measuring residual stress under curved surface, in this paper, the residual stress ultrasonic measuring robot system with two manipulators is constructed, which is based on combining industrial robot technology with residual stress ultrasonic nondestructive measuring technology. The system is mainly composed of a motion control system, an ultrasonic detection system, and a data processing system. The robotic arm controls the movement of the two ultrasonic transducers along the set scanning path which is based on the geometric model of components and adjusts the transducer's posture in time according to the shape of the workpiece being measured. The configuration information based on workpiece coordinate system is transformed into a position data that takes into consideration the first critical angle and can be recognized by the robot. Considering the effect of curvature, the principle model of residual stress measuring by the critical refraction longitudinal wave is established. The measured signal including the stress state of the measured region, as well as the actual position and posture information of the transducers, is processed by the computer in real time, which realizes automatic nondestructive measurement of residual stress under curved surface.

Residual stress measurement by strain gauge and X-ray diffraction method in different shaped rails

Abstract It is well known that rails are the most important part of railway infrastructure. Besides good wear and fatigue resistance, appropriate residual stress value in rails is required to improve performance of rails. The knowledge of residual stress types and distributions gives prediction the mechanical properties of materials for manufacturer. This study aims to make comparison between destructive and non-destructive residual stress measurement techniques and to investigate the influence of rail head geometry on residual stress by the use of two different quality rails. One of the rails is R260 grade and the other one is R260 grooved rail. In addition to residual stress measurement with strain gauge (cutting) and X-ray diffraction method, microstructures of the specimens were examined. Results show that grooved rail has higher residual stress and different types of stress were observed for samples which are supported by X-ray and strain gauge method.

Industrial application of a quick, non-destructive anisotropy characterisation method

Centerless X-ray diffractometers are specially designed for non-destructive residual stress measurement. The residual stress, and the crystalline anisotropy are induced by elastic deformation and are stored within the crystal structure. The similarity between residual stress and pole figure measurement led to the idea of developing the texture test method for centreless diffractometers. After the determination of identical lattice plane series distribution that can be measured with centreless and conventional diffractometers, advanced anisotropy measurements techniques were invented. In some cases, to characterize the sample from the aspect of crystalline anisotropy it is enough to make measurements in the specific directions (e.g. χ cuts in the rolling, cross and diagonal direction). With our centreless X-ray diffractometer, we managed to measure a χ cuts in the rolling direction under two minutes without sample cutting. The implementation of this non-destructive technique into the production line can be possible, consequently monitoring of the texture evolution even on industrial-sized aluminium coils. In this paper we compare the conventional X-ray diffraction measuring technique with our developed method on the example of a cold rolled aluminium sheets at different reductions.

Utilization of spatial resolved qualitative texture assessment method on an object of the Seuso Treasure

Centerless X ray diffractometers are specially designed for nondestructive residual stress measurements. The similarity between the X-ray diffraction based stress and texture measurement methods has led us to introduce measurement method for nondestructive (sample cutting-free) stress measuring devices, to describe the texture. After the determination of identical lattice plane series distribution with centerless and conventional diffractometers, advanced anisotropy measurements techniques were invented. The new examination methods were applied for a Late Roman silver artefact, the Perfume Box from the Seuso treasure. The spatial resolved qualitative assessment of the texture provided valuable insight on the processing of the material and manufacturing of the different parts of the artefact. The developed techniques are completely nondestructive, therefore the examined artefacts suffer no harm. The methods inherit the privileges of centerless diffractometers such as no object size limits.

An iterative approach to remove the influence of light ray bending from micron-scale scattered light tomography

Abstarct We present numerical experiments to test an iterative approach which can remove refraction-induced errors form scattered light tomography. Gradient scattered light tomography is the first method capable of direct non-destructive residual stress measurement in chemically strengthened glass. The method is based on an oblique incidence scattered light photoelasticity combined with an iterative approach to remove the influence of light ray bending from the scattered light method. In this article further numerical experiments are performed which demonstrated that the iterative approach grants the removal of the influence of light ray bending from stress profiles that have complicated shapes. Two classical examples of stress profiles in chemically strengthened glass were studied: (1) unusual stress profile, where the outermost layers of the surface are in tension (tensile surface stresses being 300 MPa), rather than compression; (2) relaxed compressive stresses in the outermost surface layer with a depth of 20 µm. We found that the nature and rate of convergence of the iterative process were notably different for compressive and tensile stresses. The analyzed stress profiles were taken from literature and hence are realistic representations of the ones that researchers might come across in glass science. Refraction induced reconstruction error Δ σ as a function of surface stress and incidence angle were simulated.

Influence of Heat Treatment on the Conductivity of Nickel-Based Superalloys

Non-destructive measurement of residual stress at the subsurface of nickel-based alloys using eddy current method has been limited by its sensitivity to its microstructure, especially to the precipitates. This paper investigates the effect of heat treatment on the electrical conductivity of RR1000, a nickel-based superalloy with a large fraction of γ’ precipitates. Different heat treatment conditions, ranging from solution heat treatment to precipitation hardening with different aging times and temperatures, are used to achieve varying initial microstructures. Hardness of the samples is measured first to quantify the heat treated samples followed by the measurement of electrical conductivity using the conductivity probes of frequencies between 1 MHz and 5 MHz. The relationship between the hardness and conductivity of the heat treated samples is then correlated further. The results highlight the significant influence of heat treatment on the sample hardness and the electrical conductivity of RR1000.

Thermal Recovery of Plastic Deformation in Dissimilar Metal Weld

Stainless steel has been widely used in challenging environments typical to nuclear power plant structures, due its excellent corrosion resistance. Nickel filler metals containing high chromium concentration, including Alloy 82/182, are used for joining stainless steel to carbon steel components to achieve similar high resistance to stress corrosion cracking. However, the joint usually experience weld metal stress corrosion cracking (SCC), which affects the safety and structural integrity of light water nuclear reactor systems. A primary driving force for SCC is the high tensile residual stress in these welds. Due to large dimension of pressure vessel and limitations in the field, non-destructive residual stress measurement is difficult. As a result, finite element modeling has been the de facto method to evaluate the weld residual stresses. Recent studies on this subject from researchers worldwide report different residual stress value in the weldments [5]. The discrepancy is due to the fact that most of investigations ignore or underestimate the thermal recovery in the heat-affect zone or reheated region in the weld. In the current study, the effect of heat treatment on thermal recovery and microhardness is investigated for materials used in dissimilar metal joint. It is found that high equivalent plastic strains are predominately accumulated in the buttering layer, the root pass, and the heat affected zone, which experience multiple welding thermal cycles. The final cap passes, experiencing only one or two welding thermal cycles, exhibit less plastic strain accumulation. Moreover, the experimental residual plastic strains are compared with those predicted using an existing weld thermo-mechanical model with two different strain hardening rules. The importance of considering the dynamic strain hardening recovery due to high temperature exposure in welding is discussed for the accurate simulation of weld residual stresses and plastic strains. Finally, the experimental result reveals that the typical post-buttering heat treatment for residual stress relief may not be adequate to completely eliminate the residual plastic strains in the buttering layer.

The Potential of Ultrasonic Non-Destructive Measurement of Residual Stresses by Modal Frequency Spacing using Leaky Lamb Waves

This paper investigates the potential of ultrasonic non-destructive measurements of residual stresses using the modal frequency spacing method based on the interference spectrum of leaky Lamb waves as an alternative to the commonly used flight-time approach in ultrasonic methods. Extensive experiments were carried out to verify the viability and robustness of the technique using an instrumented leaky Lamb wave setup with uniaxial stressed samples and welded steel samples. To improve the signal-to-noise ratio, multiple sets of raw signals of specularly reflected and leaky Lamb waves were acquired and then averaged in the time domain. The acquired data in the time domain were then transformed into the frequency domain to form the interference spectrum of leaky Lamb waves with a good repeatability. The acoustoelastic coefficient of carbon steel is then derived from the measured relationship of wave velocity and applied stress. Finally, a welded steel plate was examined and residual stress was evaluated. The current work demonstrates the feasibility and the potential of the proposed method in measuring residual stresses in welded plates and thin-walled structures.

ICONE19-43348 MEASUREMENT OF NON-EQUIBIAXIAL RESIDUAL STRESS FIELD BY INDENTATION TECHNIQUE USING ASYMMETRIC INDENTER

The instrumented indentation technique (IIT) has received much attention as an alternative evaluation method for nondestructive measurement of residual stresses in recent years. In the past, however, the measurement of residual stresses by indentation technique has been limited to an equibiaxial residual stress states because of a symmetric indenter used in this method. In the present study, the effects of the shapes of asymmetric indenters on differences in indentation loads between a stress-free state and residual stress states are discussed by theoretical approaches. These approaches are progressed by focusing on the effect of deviator residual stresses. A method for evaluating non-equibiaxial residual stress field are proposed by using these results. In addition, the proposed method is applied to bead-on-welded plate. The evaluation results by the proposed method are in agreement with the evaluation results by X-ray diffraction method.

Nondestructive Residual Stress Measurement Inside Engineering Materials

Nondestructive Residual Stress Measurement Inside Engineering Materials

On non-destructive residual stress measurement in glass panels

A portable scattered light polariscope SCALP has been developed, which permits measurement of the residual stress profile through the thickness of glass panels. At a glass factory strength assessment of glass panels of different thermal treatment was carried out using both residual stress measurement with SCALP and the traditional four-point bending tests. Linear correlation between the residual surface stress and the bending strength was observed. At another glass factory residual stress in glass panels was measured before performing the traditional fragmentation test. The results of the fragmentation test were extremely scattered and had almost no correlation with the values of the residual stre ss. It is concluded that sufficiently reliable assessment of the strength of glass panels is obtained by measuring the residual stress at the surface.