Determination Of Residual Stresses Research Articles

X-ray Diffraction for the Determination of Residual Stress of Crystalline Material: An Overview

Though there are a variety of experimental techniques available for residual stress measurements, diffraction-based measurements have the unique advantage of estimating the individual components of the residual strain matrix in a crystalline material. This is then converted to residual stresses with appropriate continuum elasticity model(s) and X-ray elastic constants. In particular, measurements based on electron or neutron diffractions have their complexities or availability issues. The laboratory X-ray diffraction, on the other hand, may provide an easy resource and an effective tool. Such measurements range from two tilt methods to more extended d-sin2ψ measurements and multiple {hkil} grazing incident X-ray diffraction. Measurements can even be conducted on single crystals with micro-Laue diffraction and extended to stress ODF (orientation distribution function) calculations. These techniques are unquestionably extremely specialized, where measurement uncertainty plays an important role in the effectiveness plus reproducibility of the data. Unfortunately, standard textbooks or review articles typically describe some, but not all, of the techniques. In this overview, different techniques of X-ray diffraction for the determination of residual stresses in crystalline material have been summarized. It is hoped that potential users may benefit from the deliberations.

Influence of the processing conditions of 6061 aluminium alloy thick plates on the distortion of the machined finished parts

The distortion in machining aluminium alloy parts is one of the serious challenges for the aluminium industry, and the residual stresses resulting in the processing steps are the main cause. Two 6061 aluminium alloy samples of parts, representing the same part with a special configuration, in two different stages of machining, were analysed to establish the influence of the processing conditions that can determine the changes in characteristics in the final machining process. Metallographic analysis, porosity determinations by the liquid penetrant inspection, tensile tests and determination of residual stresses by the Hole-Drilling method were performed. All the results obtained were correlated with the processing conditions of aluminium alloy plates. They indicated the role of the processing conditions on the residual stresses and distortion in the machined finished aluminium alloys parts.

Estimation of residual stress distribution in railway axles

The manufacturing process of railway axles usually includes axle surface treatment to induce compressive residual stress on the axle surface to increase impact resistance and fatigue lifetime. A proper determination of residual stress enables to obtain correct input data for other procedures, e.g., optimization of specialized treatment or lifetime estimation, which sets safe, but not unnecessary frequent, maintenance intervals of the axles. The most common methods for residual stress determination used by R&D centers of axle manufacturers are the hole drilling method and X-ray diffraction. However, we can use these methods for the determination of surface or close-to-surface residual stress only. In the case of large components like railway axles, it is essential to have information about the residual stress in the whole cross-section, not only from the axle surface, especially if the residual stress is developed by induction hardening, which can influence the residual stress distribution in a considerable depth.The work presented in this paper aims to develop a reliable methodology for determining residual stress in the whole cross-section of a railway axle with reasonable equipment prices or commonly used equipment. Two presented methods follow the defined methodology. They combine well-known destructive methods (layer removal and sectioning methods) with X-ray diffraction and numerical simulations to evaluate correct residual stress distribution. Both ways are applied to the case of an induction-hardened railway axle from the EA4T steel. Results of both methods are then compared to results obtained by neutron diffraction technique and other experimental methods to validate the plausibility of the proposed scenarios.

Inverse Identification of Residual Stress Distribution in Aluminium Alloy Components Based on Deep Learning

Residual stress within a structural component can significantly affect the mechanical performance and stability of a structure. Therefore, it is crucial to find a way to determine the residual stress distribution to maintain the normal working of structures. Conventional methods for residual stress determination primarily include experimental testing, finite element simulations and inverse identification. However, these methods suffer from disadvantages of high testing costs, long calculation time and low inverse efficiency. To avoid these shortcomings, this study developed a high-performance method based on a deep learning technique. In this method, an artificial neural network was used to replace the finite element calculation in the finite element model updating (FEMU) technique and the residual stress distribution of structural components was inversely obtained based on the measured residual stresses of a finite number of measuring points. Compared with the conventional FEMU technique, the calculation efficiency of the proposed method was considerably improved. Furthermore, the accuracy and efficiency of the method were verified by simulated four-point bending experiments considering an elastic-plastic material.

Quantitative and nondestructive determination of residual stress for SiO2 thin film by laser-generated surface acoustic wave technique

The laser-generated surface acoustic wave (SAW) technique is a promising method to measure the mechanical properties of thin films quickly and nondestructively. Residual stress is inevitable during the processing and manufacturing of integrated circuits, which will have a major impact on the physical and mechanical properties of the thin film materials and cause deterioration to the structural strength. In this study, the SAW technique based method is proposed for quantitative and nondestructive measuring the residual stress in the nanostructured films. The method is verified by the experiment measuring the SiO2 films in the thickness range of 100–2000 nm. The experimental procedures, including signal excitation, reception and processing, are described in detail. By matching the SAW experimental dispersion curve with the calculated theoretical dispersion curve containing the residual stress, the residual stress of the SiO2 films along [110] and [100] crystallographic orientation of the Si wafer is successfully quantified. The determination results are ranged from −65.5 to 421.1 MPa and the stress value increases as the film thickness decreases, revealing the residual stress of the SiO2 film is compressive. Meanwhile, the conventional substrate curvature method as a comparison is used to verify the correctness and superiority of the proposed SAW method for the residual stress determination.

Determination of the through-thickness residual stress in thick duplex stainless steel welded plate by wavelength-dependent neutron diffraction method

In this study, a wavelength-dependent neutron diffraction method used to measure the residual stress in thick duplex stainless steel (DSS) welded plate was proposed, which was validated by contour method. By choosing appropriate wavelength, the penetration capability of neutron was improved. The neutron with appropriate wavelengths was then applied to investigate the through-thickness volume fraction, macroscopic and phase-specific residual stress in a 55 mm thick DSS welded plate. The results showed that a wavelength at 2.395 Å had more superiorities than the conventionally-used wavelength at 1.593 Å in the measurement of longitudinal and transverse stresses of a thick DSS plate. In general, high tensile stresses were generated in austenite while high compressive stresses were found in ferrite. For elastic mismatch residual stresses, their maximum values in austenite and minimum values in ferrite were located near the mid-thickness region. Reasons for the formation and characteristics of the phase-specific stresses were also discussed. Besides, large tensile macroscopic stresses were found near the surface whilst significant compressive stresses were found to generate in the mid-thickness of weld metal.

Residual stress determination by the layer removal and X-ray diffraction measurement – correction method

Very often a manufacturing process is followed by some surface treatment. Such a process induces residual stress into the manufactured component. Compressive residual stress is desirable for enhancing the fatigue properties of the component. The residual stress is often measured only at the surface, if at all. However, residual stress is equilibrating in the whole component. Therefore, compressive residual stress at the surface induces undesirable tensile stress inside in the component. Knowledge of the residual stress distribution in a body can be very useful in engineering applications. The authors found this knowledge necessary for a proper description of fatigue crack propagation in railway axles described in the original paper [1]. With the onset of modern surface treating technologies, e.g. induction hardening, which can affect the entire cross-section of the component, the residual stress determination is even more critical.The presented paper aims to describe a procedure developed for proper residual stress determination. The procedure can be easily used e.g. in R&D centers, where X-ray diffraction residual stress measurement is already in use. The procedure is suitable for the residual stress determination in sizable cylindrical bodies or components, e.g. railway axles. It uses X-ray diffraction residual stress surface measurement and layer removal by machining. Results experimentally obtained are corrected by a general procedure developed in MATLAB software in order to obtain the original residual stress state in the cylindrical body.•More accurate procedure for a residual stress determination in cylindrical bodies.

Determination of Original In-Plane Residual Stress and Eigenstrain in Laser Peened Thin Sheet Using Unit Pulse Function and Equilibrium Constraint

Determination of Original In-Plane Residual Stress and Eigenstrain in Laser Peened Thin Sheet Using Unit Pulse Function and Equilibrium Constraint

Determination of Original In-Plane Residual Stress in Laser Peened Thin Sheet Using Unit Pulse Function and Equilibrium Constraint

Determination of Original In-Plane Residual Stress in Laser Peened Thin Sheet Using Unit Pulse Function and Equilibrium Constraint

A semi-analytical method for the calculation of double-ellipsoidal heat source parameters in welding simulation

Structural integrity assessment of welded components requires the determination of residual stress and deformations induced by the welding process. The implementation of both a numerical static mechanical analysis and a thermal transient analysis is needed in order to accurately determine stress and strain fields. The most faithful representation of the heat flow provided by the welding torch in thermal simulations is realized with Goldak’s double ellipsoid, especially in case of MIG/MAG and combined TIG-MIG/MAG welding. The correct determination of the temperature trends during the welding process simulation is essential for the subsequent mechanical FEA. In order to obtain the above-mentioned temperature trends, some parameters must be determined ex ante, e.g., the geometrical characteristics of Goldak’s double ellipsoid. Generally, a large number of trial simulations must be performed in order to define these parameters. However, manual fitting is often complicated. To overcome such difficulties, in this work, it is reported a combined analytical and numerical method to determine the parameters using the genetic algorithm NSGA-II. First-attempt parameters are obtained through the solution of the Fachinotti’s analytical formulation. This first stage requires a restricted set of experimental data, such as weld pool extension and one temperature trend in the proximity of the seam. Afterwards, first-attempt parameters and experimental data are used to determine the final parameters by means of a set of numerical thermal simulations guided through the genetic algorithm optimization. To confirm the good-functioning of the method, a numerical analysis for the simulation of the experimental data and another FE simulation performed with the final results of the method are presented.

Experimental and simulative determination of residual stress during heat treatment of 7075-T6 aluminum

Part distortion is caused by the release and redistribution of the residual stresses generated by machining and manufacturing processes applied before machining. This work aims to simulate part distortion in machining of 7075-T6 aluminum alloy. A model of heat treatments (quenching and tempering) has been developed by FEM and validated using the removal layer and contour methods. This model was applied to predict the residual stresses distributions generated by heat treatments. These stresses distributions were used in a machining model to simulate part distortion. Then, the comparison between the simulated and measured distortions permitted to validate the methodology.

AN EVALUATION OF PARTS’ FATIGUE RESISTANCE AFTER SURFACE THERMO CHEMICAL MACHINING

In order to raise a fatigue resistance the calculation-experimental method of parts surface thermo chemical machining efficiency has been carried out. The employment of two types of reference specimens in experiments has been substantiated. The employment of smooth reference specimens for a determination of residual stresses in a surface layer and of corset reference specimens for fatigue tests has been recommended. The results of experimental study of two types of thermo chemical machining (cementation and nitriding) influence on a fatigue resistance of corset specimens made of high-strength allows ВКС-5 и ВНС-17 have been used in the work. . The calculations of the study have been carried out by the Finite Elements Modeling method using the calculation complexes ANSYS and PATRAN/NASTRAN. The residual strained state modeling is carried out by thermo elasticity method. On grounds of conducted calculation its been stated that an axial residual stresses distribution in a dangerous (smallest) section of a corset specimen doesnt practically differ from a similar distribution in smooth specimens. An endurance limit increment due to corset specimens hardening was determined with use of the average integral residual stresses criterion. Carried out results let also maintain that the optimal regimes of thermo chemical machining are the regimes under which average integral residual stresses are maximum.

Neutron diffraction residual stress determinations in titanium aluminide component fabricated using the twin wire-arc additive manufacturing

In recent years, twin wire-arc additive manufacturing (T-WAAM) technique has been considered as a promising method of fabricating and shaping titanium aluminide components with high efficiency and low cost. However, excessive thermal input of the non-consumable tungsten electrode arc deposition induces significant residual stresses in the buildup component, thus accurate measurement of residual stresses is necessary for T-WAAM buildup part quality assessment. In the present research, non-destructive neutron diffraction residual stresses measurements on as-fabricated and heat-treated T-WAAM produced Ti48Al titanium aluminide components are performed. To exclude the influence of initial large T-WAAM residual stresses on d 0 hkl sample alignment, different d 0 hkl sample dimensions are designed: one is normal thin slice and the other is the meshed sample. According to the obtained results, the conducted post-production heat treatment has partially released initial residual stresses. Also, the meshed design of d 0 hkl sample shows better measurement accuracy than the simple sliced d 0 hkl sample. In addition, T-WAAM fabricated titanium aluminide wall component performs featured tensile-compressive alternating residual stress distribution induced by the layer-by-layer arc deposition.

Effects of the Temperature-Time Regime of Curing of Composite Patch on Repair Process Efficiency.

Repair procedures with the use of composite patches are considered to be the most effective among the current technologies of repair of the structures of various applications. In the process of moulding-on of a patch made of polymeric composite material by means of curing, technological stresses arise in the patch. Determination of residual technological stresses is a priority task for the modelling of the repair process. Reduction of residual stresses can be achieved by optimization of the mode of repair patch curing. For meeting this objective, the method for determination of technological stresses, which arise in the structure under repair in the process of curing of a composite patch, has been developed. The method takes into account the shrinkage, change in physico-mechanical characteristics, rheological processes occurring in the binder during moulding process, and determination of stresses in the structure under repair at any time. Therefore, premature failure of the repair joint at the stage of repair can be avoided. It is shown that the method adequately describes the level of deformations and stresses in the structure being repaired at the stage of heating and holding of the composite patch. Increase in the moulding temperature leads to a reduction in residual stresses in the structure under repair. However, current stresses at the stages of heating and temperature holding are increased significantly. Reliability of assumptions and developed method is confirmed by the comparison with the experimental data. The obtained experimental graph of total deformation of the composite patch allowed us to clearly determine the moment of residual stress occurrence in the structure under repair. This moment matches quite exactly (with the discrepancy not exceeding 5 min) the gel point determined analytically based on dependence of the degree of curing on the moulding mode. Consequently, the research together with the results previously obtained allows making an integrated choice of geometric parameters of the repair composite patch and temperature–time regime of its curing in order to ensure the specified level of strength and stiffness of the structure under repair.

Residual Stress in Engineering Materials: A Review

The accurate determination of residual stresses has a crucial role in understanding the complex interactions between microstructure, mechanical state, mode(s) of failure, and structural integrity. Moreover, the residual stress management concept contributes to industrial applications, aiming to improve the product's service performance and life cycle. In this regard, the industry requests rapid, efficient, and modern methods to identify and control the residual stress state. This review article contains three main sections. The first section covers different residual stress determination methods and reports the advancements over the recent decade. The second section includes the role of residual stresses in the performance of a broad range of materials including metallic alloys, polymers, ceramics, composites, and biomaterials. This is presented by classifying different science areas dealing with residual stresses into two main groups, including “origins” and “effects” of residual stresses. The range of topics covered are “welding, machining, curing/cooling, and spray coating processes,” “medical and dental sciences,” and “fatigue and fracture mechanisms.” The third section summarizes various strategies to effectively control residual stresses through different manufacturing procedures. It is hoped that the data provided herein serves as a valuable up‐to‐date reference for engineers and scientists in the field of residual stress.

Determination of residual stresses in a single FBG fiber/epoxy composite system

A new approach to determine residual fiber and matrix stresses in single fiber Bragg grating (FBG) fiber polymer matrix composites is developed based on the earlier work by Hoffman et al., 2020 [( Hoffman et al., 2020) 1] and Khadka et al., 2020 [( Khadka et al., 2020) 2]. In this new study, our already measured fiber strains in the composites based on room temperature (RT) and higher temperature (HT) epoxies were used to determine the stresses in the fibers. The total manufacturing residual stresses in the fibers were also separated for the curing and cooling parts of the manufacturing cycles. The cooling stresses for both epoxy systems were then independently verified through single fiber thermal numerical models. Subsequently, using our new methodology based on the Eshelby misfit approach and the single fiber thermal models, the total residual stresses in the matrix were found and then separated into the curing and cooling stresses. The maximum axial stresses at the matrix/fiber interfaces were found to be increasing with an increase in the curing temperature of the RT epoxy. For the highest curing temperature of the RT resin (70 °C), the residual axial stresses in the matrix (20 MPa) were close to the stresses in the HT epoxy (25 MPa) at the curing temperature of 121 °C. The curing matrix stresses were observed to be significant for both epoxy systems with their contributions to the total stress ranging from 28% to 48% depending on the resin type and curing conditions.

Residual stress determination using full-field optical methods

Residual stresses are created in engineering components during fabrication and processing. Such stresses can strongly influence structural behavior. They are generally found by experimental means. A widely used way of finding residual stresses is removal of a small volume of material containing stresses and measurement of the strains that develop in surrounding material as a result of stresses being released. The strains can then be used to compute residual stresses. Drilling a small shallow hole is the most common way of implementing this approach, with strains measured by nearby strain gages adhered to the surface. This paper provides an overview of how full-field optical methods can be used instead of strain gages with hole drilling, overcoming limitations associated with gages and expanding capabilities of the hole drilling approach. The methods considered are holographic and electronic speckle pattern interferometry, Moire interferometry and digital image correlation. Advantages of using optical methods to find residual stresses are shown. A variety of applications is presented, ranging from determination of stresses in underground piping to stresses in microscale specimens. In addition, optical approaches employing different ways of material removal for stress release are reviewed, as well as several non-destructive optical methods for determining residual stresses.

Determination of Residual Stress with Diffusion MR Method in Cortical and Trabecular Sections of Human Vertebral Bone Tissue

Determination of Residual Stress with Diffusion MR Method in Cortical and Trabecular Sections of Human Vertebral Bone Tissue

Determination of Residual Stresses in Cylindrical Components by the Hole-drilling Method

Determination of Residual Stresses in Cylindrical Components by the Hole-drilling Method

Mitigating Cutting-Induced Plasticity Errors in the Determination of Residual Stress at Cold Expanded Holes Using the Contour Method

BackgroundThe split sleeve cold expansion process is widely used to improve the fatigue life of fastener holes in the civil and military aircraft industry. The process introduces beneficial compressive residual stresses around the processed hole, but uncertainties remain about the character of the stress field immediately adjacent to the bore of the hole.ObjectiveThe primary objective of this study was to implement the contour method with minimising error associated with cutting-induced plasticity to provide detailed and reliable characterisation of the residual stress introduced by the split sleeve cold expansion process.MethodsA systematic FE study of plasticity effects by simulating different contour cutting strategies (a single cut, two sequential cuts and a 6-cut sequence) for a cold expanded hole in an aluminium alloy coupon was conducted. The identified ‘optimum’ cutting strategy was then applied experimentally on coupons containing a hole that had been processed to 3.16% applied expansion.ResultsThe FE study of different cutting simulations show that the locations of the stress error is consistent with the location where cutting-induced plasticity accumulated and that the magnitude and locations of stress re-distribution plasticity can be controlled by an optimised cutting strategy. In order to validate this hypothesis a high quality contour measurement was performed, showing that accurate near bore stress results can be achieved by the proposed 6-cut approach that controls cutting induced plasticity.ConclusionsThe present work has demonstrated that detailed FE simulation analysis can be a very effective tool in supporting the development of an optimum cutting sequence and in making correct choices of boundary conditions. Through optimizing these key aspects of the cutting sequence one is much more likely to have a successful, low error contour residual stress result.