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This study investigates the impact of cutting parameters on residual stress in components made from AA7075 material, which were hot forged and subsequently subjected to T6 heat treatment. Using the Taguchi experimental design, two distinct cutting cases—face turning and circumferential turning—were devised to assess residual stress at different sections of the part. During the turning process, force measurements were conducted with a dynamometer, and residual stress was subsequently measured using the X-ray diffraction method. The results indicate that both mechanical and thermal loadings significantly influence residual stress. Notably, spindle speed has the most substantial effect on residual stress in both face turning and circumferential turning, with an observed increase of up to 30% and 20%, respectively, in tensile residual stress for Case 1 and Case 2. When thermal loads are predominant, residual stress tends to be tensile, with measurements reaching as high as 89 MPa. [ABSTRACT FROM AUTHOR]

Laser peen forming (LPF) is an appealing technique for forming metal sheets using high-energy, shortduration laser pulses. The deformation of the target metal plate is closely related to the magnitude and distribution of laser-induced residual stress. Consequently, the relationship between process parameters and residual stress is worth researching. In this research, two process parameters in LPF, laser energy and coverage ratio (spot distance essentially), and one workpiece parameter, plate thickness, were examined through an element method (FEM) of multiple square-spot laser shock peening (SSLSP). Corresponding experiments of SSLSP on aluminum alloy 2024-T351 test blocks were conducted, together with an X-ray diffraction (XRD) residual stress measurement and a surface morphology observation. The FEM simulation and experimental results show that congested laser spots had a significant influence on the magnitude of compressive residual stress; higher laser energy was beneficial to the depth of the compressive stress layer but could decrease its magnitude. Therefore, for better forming ability, higher laser energy and a higher coverage ratio are beneficial; for surface strengthening, laser energy should not be too large, and the coverage ratio should be larger than 100% to ensure that the residual stress on the treated surface is compressive, resulting in better surface integrity. [ABSTRACT FROM AUTHOR]

The present study proposes machining Ti-6Al-4V with graphite nanopowder mixed electric discharge machining (NPMEDM) process using deionized water (6 gm/L) as the dielectric. A comparative analysis is performed with conventional electric discharge machining (EDM) and NPMEDM processes with peak current (IP), pulse on time (TON), and gap voltage (GV) as input parameters. Surface integrity, recast layer thickness (RLT), material removal rate (MRR), chemical analysis, and residual stress are investigated by different characterization techniques such as field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). FESEM study reveals that the addition of nano graphite powder leads to a glossy surface finish, lesser micro-cracks, and micro-holes. Recast layer thickness (RLT) improved drastically by 69% with the addition of graphite powder. The investigation also revealed an improvement in surface roughness by 74.75% in NPMEDM compared to conventional EDM. Further, the induced residual stress is investigated by XRD analysis. Obtained results reveal substantial improvement in residual stress from (340.5 ± 12.6) to (239.9 ± 62) MPa, which diminishes the chance of failure of the component. [ABSTRACT FROM AUTHOR]

Aluminum 6061-T6 sheets with a Ti–6Al–4V titanium alloy interlayer were investigated using friction stir welding (FSW) to achieve strong bonding. The influence of welding parameters on welding quality and strength was assessed by varying rotational speeds and traverse speeds, the optimal welding conditions. Welded samples with a cross section of 28 mm and excellent surface smoothness were prepared and analyzed to measure the residual stress using X-ray diffraction (XRD) techniques. This study investigated the effect of tool geometry and type on residual stresses in welded specimens and highlighted the importance of choosing the appropriate tool geometry and type to minimize residual stresses. Furthermore, finite element simulation of the FSW process was conducted using a thermal modeling approach to calculate the heat generated and predict residual stresses using ABAQUS software. Comparison of the residual stress values obtained from numerical simulations with experimental measurements demonstrated the model's ability to predict residual stresses in FSW adequately. The experimental and numerical results revealed that an increase in rotational speed and tool feeding led to higher stresses in the welded region due to an increased thermal gradient. Examination of the microstructure shows that during the welding process, the weld cross-section has become smaller than the base metal. The ultimate tensile strength and microhardness obtained in optimal conditions were 245 MPa and 108.2 HV, respectively. Examining the fracture surfaces from the tensile tests showed the soft fracture type, which is characterized by the presence of holes and depressions in the three-layer sheet. [ABSTRACT FROM AUTHOR]

In this study, premature damage in cylindrical roller bearings made of 100Cr6 (SAE 52100) was investigated. For this purpose, full bearing tests were carried out using two different lubricant formulations with similar viscosities. Published research has pointed out the occurrence of tribo-chemical reactions that cause lubricant degradation and the release of hydrogen in tribo-contact. Hydrogen content measurements were conducted on tested samples, and these measurements showed dependence on the lubricant formulations. Hydrogen diffusion and trapping were identified as significant factors influencing premature damage. The measurement of trapping energies was conducted by thermal desorption spectroscopy, whereas residual stresses, which influence hydrogen diffusion and accumulation, were measured using X-ray diffraction. The measured trapping energies indicated that rolling contact caused the creation and release of hydrogen traps. Over-rolling resulted in changes in residual stress profiles in the materials, demonstrated by changes in stress gradients. These can be directly linked to subsurface hydrogen accumulation. Hence, it was possible to determine that the location of the microstructural damage (WEC) was correlated with the residual stress profiles and the subsurface von Mises stress peaks. [ABSTRACT FROM AUTHOR]

To predict the failure of mechanical parts, it is necessary to understand the residual stress and its source, i.e., inherent strain. In this study, the distribution of three-directional residual stress components in a carburized 18NiCrMo14-6 cylindrical roller test piece with a diameter of 80mm and length of 240 mm, was measured using the extended contour method (XCM), which combines the contour method and X-ray diffraction. Thereafter, an inverse analysis was applied to the measured residual stress to reproduce the associated inherent strain distribution. First, it was shown through numerical experiments of a carburized cylindrical specimen that the distribution of the three-directional residual stress components can be accurately reproduced using XCM. Next, it was demonstrated that the distribution of the three-directional residual stress components could be obtained using general-purpose equipment by physically measuring the same type of specimen. The inherent strain distributions were evaluated. Compressive residual stress and corresponding tensile inherent strain were detected in the carburized layer. By contrast, tensile stress and inherent contraction strain were determined in the non-carburized layer just before the carburized crust. Finally, the mechanism of inherent strain generation was investigated using a thermal--elastic--plastic analysis. Possible explanations include (i) increase in transformation strain due to a change in carbon content, (ii) delay in martensitic transformation, and (iii) decrease in the martensitic transformation rate due to a decrease in the cooling rate at the core. [ABSTRACT FROM AUTHOR]

The aim of this study is to measure residual stresses, specifically in wear protection coating, using the sin2ψ based on the X-ray diffraction technique. The combination of silicon carbide substrate and aluminium oxide (SiC-5wt.% Al2O3) is used as the wear protection coating, and AlNi alloy represents the bond coat, which is formed by the flame spraying method on the mild steel substrate. This in turn has enabled to reduce the thermal expansion constant between the substrate and composite ceramic layer. The diffraction angle, 2θ, is measured experimentally, and the lattice spacing is calculated using Bragg's Law using the measured diffraction angle and the known X-ray wavelength. Interestingly, stress calculations for the samples demonstrate a linear relationship of a slop proportionate to stress same as to homogenous isotropic samples in a bi-axial stress. Thus, the relationship between dspacing and sin2ψ is demonstrated as a straight line with a slope proportional to stress. However, the oscillatory trend showed the existence of in-homogeneous stress distribution. To resolve this challenge, X-ray elastic parameters are deployed instead of Poisson ratio (v) and Young's modulus (E) values. The value of the residual stresses for these coatings calculated is compressive residual stresses of (-594.029 MPa). [ABSTRACT FROM AUTHOR]

Iron and steel industry descale rolls long-term high-pressure water erosion, high temperature, easy to wear, corrosion failure and other problems, the continuous production of steel rolling impact, descale rolls base wall thickness is the main cause of cracking of the surfacing gradient lap organization. This article combines numerical simulation and experimental testing, the use of CALPHAD method to calculate the surfacing material temperature change physical parameters, based on the double ellipsoid heat source model, the establishment of the descale roller submerged arc surfacing process of multi-field coupling three-dimensional numerical model, calculations and reveal the descale roller submerged arc surfacing process of the temperature field, the stress field, the phase change field and the flow field of the transient evolution of the law, and further analyze the descale roller wall thickness of the surfacing process of the influence of the mechanism. Calculation results show that the depth of melting of the surfacing matrix is positively correlated with the width of the double ellipsoid heat source, and the larger the wall thickness, the faster the cooling rate, the greater the formation of residual stress. The austenite and martensite phase transformation of the overlay welding process is greatly influenced by the wall thickness. At the same time, SEM, EDS, XRD material science microcharacterization experiments were carried out to observe the micro-morphology, phase and elemental composition of the cladding layer. This study lays an important theoretical foundation for optimizing the submerged arc surfacing process of descale roller. [ABSTRACT FROM AUTHOR]

X-ray diffraction (XRD) and the finite element technique (FET) to measure the residual stresses (RS) inside Al1060 rods produced by forming operation at three different half extrusion angles (HEA = 20°, 40°, and 60°) were applied. The results of the experimental work and FET illustrate a good convergence in terms of the relationship between extrusion force and displacement with an error ratio reaching 15 %. The effect of HEA = 20° on extrusion force is the lowest compared to others. Moreover, the behavior of the obtained residual stresses from XRD and FET is in good agreement with the existence of some variation in their values. The profile of these stresses is in a tensile state near the rod surface and a compressive state near the axis at HEA = 20° and 40°. In contrast, compressive residual stresses are obtained close to the surface and center of the extruded rod at HEA = 60°. [ABSTRACT FROM AUTHOR]

Laser shock peening (LSP) is a technique similar to shot peening that improves the mechanical properties, such as fatigue performance of metallic structures, by introducing compressive residual stresses. This study aims to present a 3D finite element simulation for simulating residual stress field after laser shock peening without absorbent coating (LSPwC) in real applications. Also, the residual stress distribution induced by LSPwC in a Rene 80 Ni-based superalloy was obtained via X-ray diffraction and hole drilling measurements. The excellent correlation between the simulated residual stress values and experimental test results proved this model reliable. Laser peening Rene-80 superalloy samples with single LSP impact at a laser power density of 6 GW/cm2 led to a significant increase in the compressive residual stress (-405 MPa) compared to the unpeened sample. The yield strength of laser-peened samples was improved by ~ 16% and a reduction of ~ 12% in the failure strain compared to the baseline sample. Similarly, the laser peening increased microhardness by 26% compared to the untreated samples. Scanning electron microscopy (SEM) was also utilized to interpret the failure mechanism of samples examined before and after LSP. [ABSTRACT FROM AUTHOR]

The present article addresses the influence of surface mechanical attrition treatment (SMAT) parameters such as a size of the balls (2, 5 and 8 mm ∅ 316L stainless steel (SS) balls) and treatment time (15, 30, 45 and 60 min) on the microstructural features, deformation characteristics, surface roughness and compressive residual stress induced on EN 8 steel. The effective deformation is ~ 25 μm from the top surface along with elongated grains in the near subsurface region. The decrease in crystallite size and an increase in micro-strain become more pronounced during SMAT using balls with a larger diameter and for a longer treatment time. A similar trend is observed in surface roughness. This is mainly attributed to the involvement of higher kinetic energy imposed by SMAT on EN 8 steel. The residual stress induced during SMAT of EN 8 steel measured by x-ray diffraction (XRD) measurements is higher when treated using 2 mm ∅ SS balls when compared to those treated using 5 and 8 mm ∅ SS balls for a similar time duration. Irrespective of the size of the balls, an increase in treatment time has led to a decrease in the residual stress of EN8 steel. Over working of EN8 steel that creates surface cracking has been considered responsible for the decrease in residual stress of EN8 steel treated using 5 and 8 mm ∅ SS balls for any given time duration as well as with an increase in treatment time for a given size of the balls. The development surface cone cracks and material removal from the surface evidenced from the microstructure validates such as an occurrence. When the duration of SMAT is limited to 15 min, a large difference in residual stress values is observed for the EN8 steel treated using 2, 5 and 8 mm ∅ balls, whereas with a further increase in treatment time, the difference between them becomes marginal. Hence, in order to achieve better mechanical properties, the treatment time employed for SMAT of carbon steels should be carefully optimized. The other option available is to choose lower size balls for SMAT. The change in residual stress of EN8 steel as a function of process parameters employed for SMAT and the correlation between the ball size and treatment time with the residual stress are discussed. [ABSTRACT FROM AUTHOR]

Constrained thermal expansion and contraction during welding cause a compression-tension cycle and plastic deformation in the heat-affected zone, leading to work hardening. The nature of this hardening effect—isotropic or kinematic—determines the final local yield stress and thus affects the residual stress state. Therefore, mechanical hardening must be modeled correctly in welding simulations for accurately predicting welding residual stresses. Previous studies, relying on comparisons with experimental ex situ results, led to different recommendations regarding the choice of the hardening model and thus require clarification. In this work, the stress evolution in the heat-affected zone of a tungsten inert gas weld is studied in situ using energy-dispersive x-ray diffraction and a novel method of stress analysis based on crystallite anisotropy. Additionally, microstructural information is gathered through line profile analysis. Results are shown for both austenitic and ferritic high-alloy steels and compared to ex-situ results including a validation of the new method of stress analysis. Finally, conclusions on the nature of work hardening are drawn. [ABSTRACT FROM AUTHOR]

Residual stress is responsible for various engineering failures in cases where the magnitude of residual stress exceeds the ultimate strength. With the aim of minimizing the residual stress induced in the machining of AISI 1045 steel, different machining parameters (speed, feed, depth of cut) and the output variables were experimentally investigated in this research. Series of specimens were produced using different machining parameters, and the residual stress in each was measured. When a material is subjected to external forces or thermal treatments, residual stresses can be introduced due to changes in the lattice spacing of the material. These changes in lattice spacing are detected using a non-destructive method based on the x-ray diffraction (XRD) technique. The equipment used is iXRD with MGR40P- Stress measurement system, PROTO CANADA make. The PROTO XRDWIN 2.0 software was an integral part of the XRD machine, which records all the necessary data, calculations and provides the user with surface residual stresses values. Data analysis and the process parameters were optimized using Taguchi L9 orthogonal design of experiments. To determine the effects of the machining parameters on residual stress, Analysis of Variance (ANOVA) was used. The results indicate that the feed rate is only statistically significant parameter on the residual stress with the largest main effect. The optimal setup of machining parameters that cause the lowest residual stress of − 145.4 MPa was identified, with a speed of 710 m/min, a feed of 80 mm/min, and a DOC of 0.2 mm. [ABSTRACT FROM AUTHOR]

Polycrystalline diffraction is a robust methodology employed to assess elastic strain within crystalline components. The Extended Caking (exCaking) method represents a progression of this methodology beyond the conventional azimuthal segmentation (Caking) method for the quantification of elastic strains using Debye–Scherrer 2D X-ray diffraction rings. The proposed method is based on the premise that each complete diffraction ring contains comprehensive information about the complete elastic strain variation in the plane normal to the incident beam, which allows for the introduction of a novel algorithm that analyses Debye–Scherrer rings with complete angular variation using ellipse geometry, ensuring accuracy even for small eccentricity values and offering greater accuracy overall. The console application of the exCaking method allows for the accurate analysis of polycrystalline X-ray diffraction data according to the up-to-date rules presented in the project repository. This study presents both numerical and empirical examinations and error analysis to substantiate the method's reliability and accuracy. A specific validation case study is also presented to analyze the distribution of residual elastic strains in terms of force balance in a Ti-6Al-4V titanium alloy bar plastically deformed by four-point bending. [ABSTRACT FROM AUTHOR]

Laser shock peening (LSP) is a powerful technique for improving the fatigue performance of metallic components by customizing compressive residual stresses in the desired near-surface regions. In this study, the residual stress distribution characteristics of 6061-T6 aluminum alloy induced by LSP were identified by the X-ray diffraction method, and their dependent factors (i.e., LSP coverage, LSP energy, and scanning path) were evaluated quantitatively by numerical simulations, exploring the formation mechanism of LSP residual stresses and the key role factor of the distribution characteristics. The results show that LSP is capable of creating anisotropic compressive residual stresses on the specimen surface without visible deformation. Compressive residual stresses are positively correlated with LSP coverage. The greater the coverage, the higher the residual stress, but the longer the scanning time required. Raising LSP energy contributes to compressive residual stresses, but excessive energy may lead to a reduction in the surface compressive residual stress. More importantly, the anisotropy of residual stresses was thoroughly explored, identifying the scanning path as the key to causing the anisotropy. The present work provides scientific guidance for efficiently tailoring LSP-induced compressive residual stresses to improve component fatigue life. [ABSTRACT FROM AUTHOR]

Surface residual stress is generated during the micro-milling thin-walled parts of nickel-based superalloy Inconel 718. Because of the low rigidity, deflection of thin-walled parts is easy to occur under residual stress, which makes it difficult to ensure the dimensional accuracy of thin-walled parts. Additionally, the performance of thin-walled parts is directly impacted by the residual stress state. At present, the research on the prediction of residual stress in micro-milling thin-walled parts is still blank. In this paper, the Inconel 718 mesoscopic thin-walled parts are taken as the machining objects. Firstly, a simulation model of micro-milling thin-walled parts process is established by using the finite element program ABAQUS, which realizes the prediction of residual stress in micro-milling thin-walled parts based on process simulation. And the validity of the prediction results of residual stress is verified by XRD experiments. Then, a four-factor and three-level L9 orthogonal simulation experiment is designed, which uses spindle speed, feed per tooth, axial cutting depth, and radial cutting depth as influencing factors. The prediction model of surface residual stress of Inconel 718 micro-milling thin-walled parts is built based on the results of orthogonal simulation experiments. And the model is verified by variance test and experimental validation. Finally, the optimization of cutting parameters for micro-milling Inconel 718 thin-walled parts is achieved with the maximum residual compressive stress as the optimization objective. [ABSTRACT FROM AUTHOR]

This study investigates the sintering mechanism of commercially pure Magnesium (Mg) using the Field Assisted Sintering Technique (FAST). Powder morphologies are in a vast variety of spherical to flake, as well as nano to fine grain as in powder size and mechanically milled (MM) between 0-108 hours. The MM'ed Mg particles were sintered by FAST with at 350-425°C for 5-20min. Relative densities (93-99%) and compressive strength up to 369MPa were obtained from FAST'ed Mg samples depending on MM durations and particle geometries which significantly influenced the sintering mechanism. SEM and XRD analysis identified four distinct bonding and sintering mechanisms influenced by particle geometry, residual stress, and microstructure developed through mechanical milling. The combination of mechanical milling and FAST exhibited significant effects on the microstructural and mechanical properties of Mg powders, with the Mg36 sample displaying promising strength and hardness. [ABSTRACT FROM AUTHOR]

Grinding of hardened components always bears the risk of detrimental thermo-mechanical modifications in the surface/sub-surface region. For the non-destructive detection of these damages also known as grinding burns, micromagnetic methods have found increasing interest. Existing studies on the detectability of grinding burn by Barkhausen noise evaluation point out the need for a combination of different characteristic values to distinguish between damage-free surfaces and different pronounced damages. Besides Barkhausen noise, the 3MA-II-method offers three additional measurement techniques that were also investigated in this study. Results show the potential of a combination of Incremental permeability and Harmonic analysis for the detection and distinction of different classes of grinding damages. On the other hand, no clear definition exists to categorize different levels of damages. The classification provided by the observed grey-scale after nital etching is often used, which is rather subjective and cannot be quantitatively described in terms of surface-near properties. Therefore, the present study gives a new attempt to define a parameter that describes quantitatively the existing surface state and its level of damage based on X-ray diffraction analysis. It describes the surface state characterized by the peak width, related to hardness and residual stresses in one single parameter. The investigations show that this approach could be validated for different workpieces and heat treatment conditions, and could allow a quantitative classification of damages thus making non-destructive analysis easier to apply. [ABSTRACT FROM AUTHOR]

Surface Mechanical Attrition Treatment (SMAT) is one of the processes used to improve surface properties. In the present study, the effect of process parameters such as the diameter and number of shots, working height, and SMAT time on the residual stresses and the mechanical properties of the AZ31 magnesium alloy surface is investigated. This analysis was performed using Minitab software, experimental tests, Taguchi test design (array L9), and signal-to-noise analysis. In this research, investigating the microstructure using a scanning electron microscope (SEM), determining the phases and crystal structure using an X-ray diffraction (XRD) pattern, measuring the hardness of the samples using the Vickers method, and evaluating the wear behavior of the samples using the wear test method by peening on the disc were considered. Samples 1 and 3 had the minimum and maximum mass reduction, accompanied by a 32 and 57 % increase in wear resistance compared to the raw sample. By performing the SMAT process during the L9 experiments, the nanocrystallization of the grains caused a 35 and 46 % increase in the hardness of samples 1 and 3 with minimum and maximum hardness, and as a result, an increase of 32 and 57 % in wear resistance was seen compared to the raw sample. According to the results, time was considered the most important parameter of the process, and it affected the residual stress, surface hardness, and wear resistance by 63 and 64 %, respectively. This relates to the fineness of the grains on the surface and the microstrains created by the SMAT process. [ABSTRACT FROM AUTHOR]

Residual stresses significantly influence the integrity and performance of welded structures. Accurate measurement and understanding of these residual stresses are essential to ensure the reliability and safety of welded parts. There are several methods used to measure residual stresses in welds, including the Center Hole Drilling (CHD) technique, Deep-Hole Drilling (DHD) technique, Contour method (CM), and Block Removal, Splitting, and Layering (BRSL) technique. Additionally, non-destructive measurement procedures like X-ray diffraction (XRD), neutron diffraction (ND), and synchrotron X-rays are used for analyzing residual stresses in welded components. The wire-cut electrical discharge machining technique is frequently utilized for small, precise cuts. Wire-cut electrical discharge machines are typically used to cut materials with hard structures and delicate geometries. Since this machining method is non-conventional, there is no contact between the tool (wire) and the workpiece, which is its main advantage. This gives it an advantage over other machining procedures and makes the procedure competent for machining even weakly structured and delicate materials. The function of wire electrical discharge machine in cutting has been discussed in this study to measure residual stresses in weldments by the contour method. [ABSTRACT FROM AUTHOR]

The residual stress field induced by interference-fit riveting in aircraft panel structures significantly affects the fatigue performance around the rivet holes. Common residual stress analytical models often overlook the non-uniformity of interference between the rivet and the hole, which impacts the applicability of these models. Addressing this issue, an analytical model of residual stress around the rivet hole is proposed for a typical single-riveted structure based on the thick-walled cylinder theory and Lame's equations, considering the non-uniform interference along the axis of the rivet hole. This novel model is then extended to multi-riveted structures in fuselage panels. Using vector synthesis, analytical models for single-row double-rivets and double-row quadruple-rivets configurations were derived. The established analytical models provide a three-dimensional characterization of the residual stress field in typical riveted structures. Finally, the accuracy of the model is verified through X-ray diffraction experiments and FEM simulation results. [ABSTRACT FROM AUTHOR]

This work explores the advantages and disadvantages of a methodology using high-energy X-ray diffraction to determine residual stresses in multilayer structures produced by atmospheric plasma spraying. These structures comprise a titanium alloy substrate (Ti64), a bonding layer (Ni-Al), and an abrasive coating (Al2O3). This study focuses on analyzing the residual stress gradients within these layers. The presented method is used to determine stresses across the entire thickness of multilayer structures. Experiments were carried out using a high-energy rectangular beam, operating in transmission mode, on the cross-section of the sample. The results indicate variable stresses throughout the depth of the sample, particularly near the layer interfaces. The semi-automatic methodology presented here enables us to follow stress evolution within the different layers, providing indications of the load transfer between them and at their interfaces. The sin2ψ method was used to analyze the diffraction data and to determine the stresses in each phase along the sample depth. However, interpreting results near the interfaces is complex due to the geometric and chemical effects. We present a discussion of the main advantages and disadvantages of the methodology for this kind of industrial sample. [ABSTRACT FROM AUTHOR]

The identification of residual stresses (RS) in components made by selective laser melting (SLM) is necessary for subsequent technological optimization. The presented research is devoted to evaluating the influence of the combination of laser power (P), scanning velocity (v) and the rarely considered number of layers (nL) on surface residual stresses in SLM stainless steel SS 316L. Experimental parameters were set based on the Design of Experiment (DoE) method, with follow-up X-ray diffraction (XRD) measurements and data processing using analysis of variance (ANOVA) and regression analysis. The obtained data are a valuable stepping-stone for the subsequent design of research focused on the application of sustainable eco-friendly Abrasive Water Jet (AWJ) peening for RS modification in the evaluated material. [ABSTRACT FROM AUTHOR]

This paper presents a novel computer‐aided computational framework to determine the optimum shape parameters in a welding heat source model using a coupled supervised Gaussian process regression (GPR) and genetic algorithm (GA) approach in estimating the welding residual stresses. The experimental X‐ray diffraction (XRD) approach validates the optimization‐improved thermal–mechanical simulation method. The validation of the proposed approach includes the welded plates with simple geometry to welded pipe‐to‐plate and the circular hollow section joints with complex topologies. The optimization‐derived shape parameters in a welding heat source model lead to close estimates of the temperature history and the welding residual stresses for these types of welded joints considered in this study. [ABSTRACT FROM AUTHOR]

Background: Excessive levels of residual stresses (RS) in metallic components of flexible pipes can lead to failure by fatigue or stress-corrosion cracking (SCC) mechanisms. Accurate measurements of residual stresses are essential in order to support comprehensive integrity assessments of these structures. Objective: This paper aims at proposing a methodology for in-field evaluation of the residual stresses in the tensile armour of flexible pipes. This methodology is evaluated by comparing results from the contour method (CM), a portable (PXRD) and a benchtop (BXRD) X-ray diffractometer. Methods: A set of samples with a controlled RS state was used to evaluate PXRD depth-profiles by comparison with BXRD measurements. CM was used to investigate stress values elsewhere in the cross-section of the samples. PXRD was then used to measure the total stress on a full-scale flexible riser. Results: Strong texture was seen in XRD measurements due to the preferential orientation in the samples, but a method to overcome this is proposed. RS measurements with PXRD were in close agreement with BXRD values in all samples. Total stress profiles obtained by PXRD on a tensile armour of flexible pipe are given. CM did not provide reliable results in the near-surface region of shot-peened samples, but reasonable agreement was found with BXRD after manual adjustment of a smoothing parameter when depths from 0.3 mm to 1.5 mm were analyzed. Conclusion: A methodology has been established for non-destructive in-loco profiling of the total stress state in tensile armours of flexible pipes with PXRD; in a real application scenario it could provide valuable information that could help to understand damage initiation mechanisms. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) is a type of additive manufacturing (AM) technique characterized by multiple localized thermal processes that result in rapid heating and cooling. The thermal variations observed in the LPBF process can generate residual stress (RS) inside the fabricated part, impacting the surface integrity and geometric tolerances of the manufactured components. To reduce thermal variation during manufacturing, heat-assisted AM was employed, thereby minimizing RS and any thermal distortion that could occur during the fabrication of materials. The present research utilizes non-destructive x-ray diffraction to analyze the influence of an in-situ heated building plate and processing parameters on the RS distribution in Inconel 718 (IN718) fabricated by LPBF. This study examines the impact of two scanning procedures and three laser power levels and offers critical insights into both measurement techniques and RS characterization. By understanding the effect of the processing parameters on RS, we aim to enhance the quality of manufactured parts through process optimization. Post-processing heat treatment consistently reduced RS in all samples, regardless of laser power levels or scanning strategies. Combining a chess scanning strategy with 270 W laser power resulted in the most significant RS reduction in IN718. [ABSTRACT FROM AUTHOR]

The role of the initial residual stresses (IRS) induced by the milling on the efficacy of laser shock peening (LSP) was investigated numerically on IN718 specimens. Three milling conditions exhibiting high (3.5 μm), medium (1.1 μm), and low (0.6 μm) surface roughness were considered for LSP. Experimentally measured (from XRD) milling-induced sub-surface (up to 60 μm depth) residual stresses were introduced into the simulations of LSP as predefined fields. The role of spot diameter with the IRS on the LSP-induced residual stress was studied systematically. For most cases, the tensile IRS from milling caused a significant decrease in the magnitude of maximum compressive residual stresses induced by LSP. [ABSTRACT FROM AUTHOR]

The continued interest in developing more accurate finite element models of the cold expansion process has driven the need for better measurement methodologies. This work details an x-ray diffraction (XRD) procedure explicitly designed to determine the residual stresses around a cold expanded hole. Aluminum coupons from two different alloys (2024-T351 and 7075-T651), with nominally 12-mm-diameter holes, were cold expanded to two different levels of applied expansion and measured using XRD. The results of a limited interlaboratory study highlight the reproducibility that one may expect to achieve by its application. For the majority of data points, the residual stresses characterized at each of the two laboratories were in agreement within the bounds of the residual stress determination experimental uncertainties, which were generally ± 15 MPa or less. After examining the differences between results obtained at each laboratory as a function of radial distance from the hole, it was found that no significant systematic error exists between data sets. Thus, the proposed novel procedure appears to provide a more precise and accurate determination of the residual stresses around cold expanded holes with a significant reduction in measurement uncertainty compared to conventional XRD measurement procedures. The results obtained using this novel procedure will be useful in calibrating new computational material models of the expansion process. [ABSTRACT FROM AUTHOR]

This study evaluates the effect of two different quench practices on distortion, sensitivity to quench cracking, development and distribution of residual stress, microstructural uniformity, and hardenability of standardized test castings. Navy C-rings made of AISI 4340 were quenched in this experiment. Some rings were quenched in a conventional draft tube immersion quench bath, and others were quenched in an intensive quench spray system to compare with the results from the conventional immersion quench bath. The rings were measured with a coordinate measuring machine, for distortion and flatness, before and after quenching. Hardness profiles of the quenched rings showed through hardness of 57.0-59.0 HRC, and the microstructures were largely martensitic. DANTE modeling software was used to predict the quenched properties of the rings, simulating microstructural transformation and residual stresses for each quench practice. XRD was used to measure surface residual stress distribution of the quenched rings, and results were compared to the predicted values by the modeling software. The surface residual stress was tensile for the conventional immersion quench and compressive for the intensive spray quench. Crack initiation correlated to areas of large tensile stress concentration and microstructural heterogeneity. [ABSTRACT FROM AUTHOR]

This study investigates the relationship between residual stresses, cutting parameters, and machining performance in the milling process of compacted graphite iron (CGI). X-ray diffraction (XRD) analysis is employed to measure residual stresses on the cast and milled surfaces, while cutting force modeling is utilized to calculate the tangential force, power, and active work. The results demonstrate that tensile residual stresses are predominant on the milled surfaces, attributed to the both mechanical and thermal loads generated during milling. By analyzing various cutting conditions, it is observed that lower feeds contribute to reduced plastic deformation, resulting in lower residual stress levels. Additionally, higher cutting speeds lead to higher temperatures, but due to the shorter machining time, heat accumulation is limited, resulting in higher residual stresses, especially at low feeds. At high feeds, residual stresses decreased as the cutting speed increased. The interplay between cutting parameters and residual stresses highlights the need for optimizing cutting conditions to enhance fatigue strength in CGI components. These findings provide valuable insights for process optimization and quality control in the milling of CGI materials. [ABSTRACT FROM AUTHOR]

Maraging steels are a family of Fe-Ni-Co-Mo alloys, and Ti addition to promote precipitation hardening with Ni and Mo. By adjusting the chemical composition and aging parameters maraging steels may be produced in classes of resistance from 200 to 400 ksi of ultimate tensile strength. As a concept, these alloys must present a combination of high strength and fracture toughness and are, for this reason, used in the manufacture of components and parts that must withstand large loads. Although maraging steels have good machinability as solution treated, the literature is scarce in studies on grinding machining processes of this type of steel with conventional grinding wheels. This work aims to analyze the results of residual stresses and surface finishing of maraging 350 steel machined by surface grinding process using a conventional sol-gel grinding wheel. Subsequently, the roughness of the machined surfaces was analyzed and residual stresses were measured by x-ray diffraction, using the sin2ψ method. The feed speeds increase in the range of 11-17 m/min contributed to a decrease in the magnitude of compressive residual stresses in the surfaces. The feed speeds and infeed did not exert a significant influence on the roughness results. [ABSTRACT FROM AUTHOR]

Layer removal with electropolishing is a well-established method when measuring residual stress profiles with lab-XRD. This is done to measure the depth impact from processes such as shot peening, heat treatment, or machining. Electropolishing is used to minimize the influence on the inherent residual stresses of the material during layer removal, performed successively in incremental steps to specific depths followed by measurement. Great control of the material removal is critical for the measured stresses at each depth. Therefore, the selection of size of the measurement spot and electropolishing parameters is essential. The main objective in this work is to investigate how different electrolytes and electropolishing equipment affect the resulting surface roughness, geometry, microstructure, and consequently the measured residual stress. A second objective has been to establish a methodology of assessing the acquired electropolished depth. The aim has been to get a better understanding of the influence of the layer removal method on the accuracy of the acquired depth. Evaluation has been done by electropolishing one ground and one shot peened sample of a low-alloy carbon steel, grade 1.1730, with different methods. The results showed a difference in stresses depending on the electrolyte used where the perchloric acid had better ability to retain the stresses compared to the saturated salt. Electropolishing with saturated salt is fast and results in evenly distributed material removal but has high surface roughness, which is due to a difference in electropolishing of the two phases, ferrite, and pearlite. Perchloric acid electropolishing is slower but generates a smooth surface as both ferrite and pearlite have the same material removal rates but may cause an increased material removal for the center of the electropolished area. In this work, it is suggested to use perchloric acid electropolishing for the final layer removal step. [ABSTRACT FROM AUTHOR]

Surface residual stresses in welded specimens significantly influence properties such as fatigue resistance, fracture toughness, and the superplasticity of joints. In this study, we employed friction stir welding, a well-established joining method, to weld dissimilar titanium alloys. By combining two distinct titanium alloys, we aimed to harness their unique properties when subjected to cyclic loading, impact, or superplastic forming processes. Utilizing X-ray diffraction, macroscopic surface stresses were assessed in dissimilar titanium alloys (Ti-6242 standard grain (SG) and Ti-54M) welded via friction stir welding, assuming a linear lattice distortion. The study accounted for misalignment, significant distortion, and grain refinement in the stir zone. Macroscopic surface residual stresses were quantified on the weld surface and at a depth of 1.5 mm beneath it within a square cross-section (1 × 1 mm2) by oscillating the specimen in the (X-Y) direction. The sin2φ method, implemented through the LEPTOS® (v7.8) software, was employed for residual stress measurement. The analysis of the results was conducted with respect to different rotation and traverse speeds. It was noted that at the center (CEN) of the weld, commonly referred to as the weld nugget, approximately 50 MPa of tensile stress was observed under the lowest values of both tool rotation speed and traverse speed. Tensile residual stresses were evident at the boundaries and within the stir zone. No discernible pattern was observed at the specified locations. Notably, the resultant values of residual stress, influenced by rotation and traverse speeds, exhibited asymmetry. [ABSTRACT FROM AUTHOR]

The heat‐induced microstructure evolution of nanomultilayers (NMLs) with metallic components is widely studied due to its critical importance in ensuring the reliable application of these nanomaterials. The thermal degradation of NMLs is controlled by mass transport of one of the NML components from the NML volume to its surface. The outflow occurs at temperatures well below the melting point of metal, offering new opportunities for the engineering of innovative NML‐based brazing fillers. A combined experimental‐modeling approach for the quantitative analysis of silver (Ag) outflow kinetics in Ag/AlN NMLs is presented. The method is based on in situ monitoring of the X‐ray diffraction intensity evolution of Ag acquired from the near‐surface region of NML (grazing incidence geometry) upon annealing in the temperature range of 230–425 °C (atmosphere of N2). The experimental data are compared to model predictions of Ag diffusion. It is assumed that Ag diffusion is driven by the relaxation of residual stresses in Ag nanolayers. Due to the multilayer geometry, the surface outflow kinetics are mainly defined by the kinetics of Ag diffusion along Ag/AlN interphase boundaries. The parameters defining the Ag surface outflow kinetics, i.e., diffusion coefficients and activation energy for diffusion, are derived. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) by using direct metal deposition (DMD) often causes erratic distortion patterns, especially on large parts. This study presents a systematic distortion analysis by employing numerical approaches using transient–thermal and structural simulations, experimental approaches using tomography, X-ray diffraction (XRD), and an analytical approach calculating the buckling distortion of a piston. The most essential geometrical features are thin walls situated between massive rings. An eigenvalue buckling analysis, a DMD process, and heat treatment simulation are presented. The eigenvalue buckling simulation shows that it is highly dependent on the mesh size. The computational effort of the DMD and heat treatment simulation was reduced through simplifications. Moreover, artificial imperfections were imposed in the heat treatment simulation, which moved the part into the buckling state inspired by the experiment. Although the numerical results of both simulations are successful, the eigenvalue and DMD simulation cannot be validated through tomography and XRD. This is because tomography is unable to measure small elastic strain fields, the simulated residual stresses were overestimated, and the part removal disturbed the residual stress equilibrium. Nevertheless, the heat treatment simulation can predict the distortion pattern caused by an inhomogeneous temperature field during ambient cooling in an oven. The massive piston skirt cools down and shrinks faster than the massive core. The reduced yield strength at elevated temperatures and critical buckling load leads to plastic deformation of the thin walls. [ABSTRACT FROM AUTHOR]

An experimental study on the distribution of residual stresses induced by shot peening on samples of SAE 1020 steel with pre-existing compressive stresses is presented. Two samples with similar geometries were subjected to a heat treatment to relieve stress. Then, one of the samples was subjected to a cementation process to introduce compressive residual stresses. Both samples, with and without cementation, were subjected to the same shot peening treatment. Using X-ray diffraction and electrolytic polishing to remove superficial layers, the depth-resolved residual stress distribution was obtained. It was concluded that the effect of pre-existing compressive stresses should be considered as a factor that influences the final distribution of the residual stresses induced by shot peening, namely the maximum of shot peening induced residual stresses moves closer to the surface in a sample with large initial compressive stresses and its value is greater than the maximum value for a specimen with lower initial compressive stresses.

Scalmalloy® is an Al-Mg-Sc-Zr-based alloy specifically developed for additive manufacturing (AM). This alloy is designed for use with a direct aging treatment, as recommended by the manufacturer, rather than with a multistep treatment, as often seen in conventional manufacturing. Most work with Scalmalloy® is conducted using powder bed rather than powder-fed processes. This investigation seeks to fill this knowledge gap and expand beyond single-step aging to promote an overall balanced AM-fabricated component. For this study, directed energy deposition (DED)-fabricated Scalmalloy® components were subjected to low-temperature treatments to minimize residual stresses inherent in the material due to the layer-by-layer build process. X-ray diffraction (XRD) indicated the possibility of stress minimization while reducing the detriment to mechanical strength through lower temperature treatments. Microstructural analyses consisting of energy dispersion spectroscopy (EDS) and electron backscatter diffraction (EBSD) revealed the presence of grain growth detrimentally affecting the strength and elongation made possible by very small grains inherent to AM and rapid solidification. Tensile testing determined that treatment at 175 °C for 1 h provides the best relief from the existing residual stresses; however, this is accompanied by a diminishment in the yield and tensile strength of 19 and 9.5%, respectively. It is noted that treatment at 175 °C for 2 h did not provide as great of a decrease in residual stresses, theorized to be the result of grain growth and other strengthening mechanisms further stressing the structure; however, the residual stresses are still significantly diminished compared with the as-built condition. Furthermore, a minimal reduction of the tensile strengths indicates the possibility of finding a balance between property diminishment and stress state through the work proposed here. [ABSTRACT FROM AUTHOR]

In this study, soapstone waste originated from craftsmanship activities was used as an alternative filler (0–30 wt%) for a high‐density polyethylene (PE) matrix. The aim of this paper is to understand the effect of the filler particles on crystallinity, thermal stability and thermo‐mechanical properties of this newly developed composite material. Physico‐chemical characterization was performed by x‐ray diffraction (XRD) and Fourier‐transform infrared (FTIR) spectroscopy. Thermogravimetric analysis (TGA), oxidation induction time (OIT) and dynamic mechanical thermal analysis (DMA) were performed to assess the effect of the filler on the themo‐mechanical properties of PE. Thermal stability, measured by TGA, was enhanced, while OIT values reduced with filler content. A significant increase on the storage modulus of the composites (up to 148% in comparison with unfilled PE) was observed and this reinforcing effect was even more prominent at higher temperatures. XRD analysis revealed that the degree of crystallinity improved significantly with soapstone loading, which explains the substantial increase in stiffness observed. Increased crystallinity is also associated with higher strength, reduced residual stress, and better dimensional stability of end products, which can be particularly attractive for pressure pipe applications. [ABSTRACT FROM AUTHOR]

Railway wheels are usually attached to axles by press-fitting; therefore, the mechanical processes taking place during operation can result in failure, with fatal consequences for the axle seats. This manuscript describes the effect of laser hardening on the residual stress state, microstructural parameters (lattice defects—dislocations, crystallites, microstrains, etc.), and mechanical properties of laser-hardened EA1N steel railway axles under fatigue life conditions. Differences were found between ground, single-track, and multi-track hardened surfaces. Tensile residual stresses, low dislocation densities and hardnesses, and different microstructures (tempered cubic martensite) were found at the overlapped tracks and at the boundary of the heat-affected zone and bulk surface compared with the hardened zone. As a result, the surface treatment of axle seats by laser hardening improved the fatigue failure resistance compared with untreated seats. Optimal properties of the integrity of the axle seat surface were achieved, including fatigue resistance, which seems to be positively influenced mainly by sufficient hardness and the appropriate microstructure. The influence of the other investigated parameters was not evident, and was reduced by the presence of fretting corrosion and press-fitting. [ABSTRACT FROM AUTHOR]

In order to enable and promote the adoption of novel material processing technologies, a comprehensive understanding of the residual stresses present in structural components is required. The intrinsically high energy input and complex thermal cycle during arc-based additive manufacturing typically translate into non-negligible residual stresses. This study focuses on the quantitative evaluation of residual stresses in an Al–6Cu–Mn alloy fabricated by wire and arc-directed energy deposition. Thin, single-track aluminum specimens that differ in their respective height are investigated by means of energy-dispersive high-energy X-ray diffraction. The aim is to assess the build-up of stresses upon consecutive layer deposition. Stresses are evaluated along the specimen build direction as well as with respect to the lateral position within the component. The residual stress evolution suggests that the most critical region of the specimen is close to the substrate, where high tensile stresses close to the material's yield strength prevail. The presence of these stresses is due to the most pronounced thermal gradients and mechanical constraints in this region. [ABSTRACT FROM AUTHOR]

Using X-ray diffraction, there were determined the residual stresses on the surface of the AISI 310S stainless steel carrier tape used in manufacture of the second generation high temperature superconducting (2G HTS) wires at the National Research Center "Kurchatov Institute," from delivery to deposition of the main buffer layer YSZ between the tape and the superconducting layer, and the residual stress in the buffer layer YSZ itself. The compressive stress of –0.8 GPa induced by rolling was found on the surface of the tape as-delivered. During processing, it varies from –0.5 to –1.1 GPa. At each stage, its depth distribution was found down to 10 μm, and the residual stresses caused by processing were determined. The residual stress in the YSZ layer deposited using the ABAD technology is compressive and amounts to –3.29 GPa. The layer has a defective single-crystal structure in type to radiation swelling with the unstressed lattice period of 5.1820 Å, 0.9% larger than in ordinary crystal. The results obtained are in agreement with the data of the earlier neutron diffraction study of residual stresses inside the carrier tape. [ABSTRACT FROM AUTHOR]

Residual stresses are usually not considered in engineering calculations of components and structures, however, they are present more or less in most of components, such as castings, welded components, components produced by rolling, bending, etc. The main objective of presented research is to determine the residual stresses in seamless thin-walled pipes, i.e. in ring specimens cut out from hot-rolled pipes. Pipe Ring Notched Bend specimens cut out from a pipe are considered as an alternative to the standardized Single Edge Notched Bend specimen used for determination of pipe material fracture toughness. In this research, residual stresses in ten ring specimens are measured by two methods: Incremental Hole Drilling Method (IHDM) and X-Ray Diffraction (XRD). Hoop residual stress is considered as the most important one in pipes. Principal stresses, as well as orientation of principal coordinate system, are determined by IHDM, and subsequently, hoop residual stress is calculated. Direct residual stress in hoop direction is measured by XRD. All results are shown on diagrams up to the depth of 1 mm from outer surface of each ring. Direct comparison of results referring to residual stresses obtained by both methods of measurement is presented to conclude that measurement with XRD shows uncertainty at some depths of measurement, since that method of measurement gives results with some large local oscillations. [ABSTRACT FROM AUTHOR]

This study is focused on analysing residual stresses (RSs) after turning high-tempered bearing steel through the use of the X-ray diffraction (XRD) technique. Phase transformations expressed in terms of the near-surface white layer (WL) and the corresponding microhardness profiles are correlated with the RSs as well as the depth of the RS profiles. Normal and shear components of RS and FWHM (full width at half maximum) of the diffraction peaks are analysed as a function of cutting insert flank wear as well as the cutting speed. It was found that the influence of tool wear prevails over cutting speed, RSs tend to shift into the compressive region with increasing tool flank wear, and the valuable shear components of RSs can be found in the near-surface region when the cutting inserts of lower flank wear are employed. The increasing flank wear also increases the depth in which the compressive RSs can be found. Furthermore, surface RSs are affected by the phase transformation process (formation of re-hardened WL) as well as the superimposing mechanical and thermal load. [ABSTRACT FROM AUTHOR]

Shot peening (SP) is a surface cold hardening process used on metals to enhance life under cyclic stress. In this case, SP was applied to SAE5160H samples of steel quenched tempered in oil at 460 °C used for leaf springs. This study shows the residual surface stresses measured through X-ray diffraction (XRD) and the microhardness variation through the perpendicular-to-the-peened surface using a combination of metallographic preparation and Vickers microhardness (HVN). This combination of techniques makes possible measuring the SP effect in perpendicular-to-the-treated surface. A residual stress of -365.8 ± 78 MPa measured by XRD and a maximum microhardness of 525± at 92.7 HVN on the surface were obtained for the SP material. Alternatively, an average of 54.2 ± 54.3 MPa residual stress measured by XRD and 433 ± 39.5 HVN were obtained for the As-it-is samples. In addition, corrosion electrochemical potential tests showed that SP increases the corrosion potential, which makes this process undesirable if the SP component is exposed to aggressive environments. Moreover, the As-it-is samples presented not statistically significant HVN difference in the measured points. The combination of experimental techniques allows estimating hardness change in perpendicular-to-the treated surface separated by as little as 10 µm but with a simpler specimen preparation than other techniques such as XRD or strain gauges. Such a combination can be an alternative for estimating residual stresses through depth. [ABSTRACT FROM AUTHOR]

The present experimental study introduced NTA-WAAM system for fabricating thin-layered structures using ER70S-6 wire. The study is directed towards determining the Sw in the manufactured parts, considering varying level of TS (0.17, 0.19, and 0.24 m/min) and BL (2, 3, 7 layers). The Sw is computed through image processing using canny edge detection method. Increasing the BL from 2 to 7 and reducing TS from 0.24 to 0.17 m/min, the resulting Sw is increased from 1.05 to 2.69 mm. So with high BL, TS should be more to suitably control the Sw because of high heat dissipation and low fluidity of molten pool. In addition to the morphological attributes, microstructural evolution, XRD, Rietveld refinement, tensile, and wear testing are incorporated to present the feasibility and stability of part fabricated through NTA-WAAM. Crystallite size, dislocation density, and residual stress are computed through XRD. It is observed that when approaching the top section from bottom zone of deposition, crystallite size is reduced from 23.43 to 21.85 nm, whereas dislocation density (2.83 × 1012 to 6.52 × 1012m−2) and residual stress (−263.72 to −300.12 MPa) are increased. It indicates the adverse effect of crystallite size towards dislocation density and residual stress, which is primarily attributed to varying level of heat transfer during deposition. The deposit exhibits an ideally refined crystal structure than initial filler wire as χ2≈1 (from Rietveld analysis). Compressive residual stress development further improves the fabricated part's tensile characteristics. Formation of equiaxed dimples, characterises the ductile failure phenomena, whereas the enhancement in their dimensions reflects the improvement in ductility. [ABSTRACT FROM AUTHOR]

Large temperature gradients inherent to additive manufacturing (AM) processes induce large residual stress (RS) in the final part. Because RS can influence the tribological properties, this study focuses on the relationship between wear sliding properties and RS in IN718 coatings. Such coatings were deposited with a Laser metal deposition (LMD) machine using two different scanning strategies. The wear resistance and RS state were investigated after surface milling. RS were measured before and after wear tests on a reciprocating sliding test apparatus. Two different X-ray diffraction techniques were employed to measure the surface and subsurface state RS: Laboratory Energy Dispersive X-ray Diffraction (LEDXD) and Synchrotron X-ray Energy Dispersive Diffraction (SXEDD). Due to the milling process, the coatings show similar depth distributions of RS from 22 to 92 µm depth, but exhibit different magnitudes depending on the scanning strategy used. Reciprocating sliding wear tests induced high compressive residual stresses that erased the initial RS state, and a similar wear behavior was observed in the two samples. These samples possess similar texture and grain morphology. This demonstrates that the influence of RS on wear resistance is a second-order effect. Nevertheless, it was observed that RS can still impact the wear performance at the early testing stages of the repaired parts. [ABSTRACT FROM AUTHOR]

Objectives: To assess the effect of glass–ceramic coated zirconia versus alumina air-abraded zirconia on the shear bond strength (SBS) of resin cement and investigate the residual stresses present on both mechanically pre-treated surfaces. Materials and Methods: A total of 180 zirconia disks, with diameters of 10 mm and 5 mm, were divided into two groups: DCMhotbond glass–ceramic coated, followed by hydrofluoric acid etching (DCM), and alumina air-abraded (AB). All mechanically pre-treated disks were conditioned with G-Multi Primer and bonded using G-Cem Linkforce Cement. Ninety specimens were immersed in distilled water for 24 h and subsequently allocated into three groups based on aging conditions (n = 15/subgroups): immediate testing, 5000 thermal cycles, and 10,000 thermal cycles. Then, the shear bond strength was assessed, and the obtained data were subjected to analysis using a two-way ANOVA, followed by a one-way ANOVA and Tukey's HSD post hoc test (α = 0.05). The residual stresses present on both mechanically pre-treated surfaces were examined using X-ray diffraction analysis. Results: The mean SBS values of the DCM and AB groups showed no significant difference under each aging condition. The SBS of DCM groups was not affected by thermal cycles, whereas the SBS of AB groups exhibited a significant decrease following thermal cycles. Glass–ceramic coated surfaces exhibited higher compressive stresses than alumina air-abrasion. Conclusions: The DCMhotbond glass–ceramic coated zirconia showed comparable bond strength to the alumina air-abrasion technique. Clinical Relevance: The DCMhotbond glass–ceramic coating technique is a promising alternative for zirconia surface pre-treatment. However, further investigations are needed before suggesting its clinical use. [ABSTRACT FROM AUTHOR]