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Circular saw blades, a large diameter-to-thickness ratio tool, are widely used in the aerospace and transportation sectors. However, it is limited due to its thinning tendency and weak stiffness. In this study, a novel tool tensioning technique was developed using the ultrasonic surface rolling process (USRP) to improve the tool performance of circular saw blades by changing the microstructure and residual stress distribution. Archimedean spiral curve textures were successfully created on both sides of a circular saw blade using an ultrasonic rolling experimental platform. The results show that USRP induced a gradual change in the dislocation structure from a microstrip mixing pattern to a lamellar band structure, accompanied by an increase in high-angle boundaries and a decrease in dislocation cell size. These textures result in a "low–high-low" trend in the radial residual stress distribution along the radius of the circular saw blade, and this residual stress variation improves the tool dynamic performance of the circular saw blade by more than 10% based on real-time x-direction (feed direction) cutting vibrations. In addition, a rolling tensioning evolution mechanism is proposed to explain how the synergistic effect of ultrasonic vibration and rolling force generates the residual stress field. This study elucidates the evolutionary mechanism of USRP-induced tensioning of thin circular saw blades, paving the way for a high-quality, cost-effective tensioning process. [ABSTRACT FROM AUTHOR]

Helical milling is widely used in aerospace as a key processing technology for Carbon fiber reinforced polymer (CFRP). However, the eccentric machining characteristics lead to an unusually complex pattern of cutting force and residual stress distribution on the work-piece during helical milling processing. Based on the Hashin failure criterion, a 3D FEM model of CFRP helical milling was built for analyzing the changing law of cutting force, then the three factors and three levels orthogonal tests were used to investigate the influence of machining parameters on the axial force, radial force, and minimum principal residual stress, finally, the multi-objective optimization based on grey correlation analysis was realized. The results showed that the errors of axial force and radial force obtained by simulation and experiment were 10.68% and 12.26%, respectively. The axial force and radial force were negatively correlated to the spindle speed, positively correlated to the axial cutting depth, and uncorrelated to the feed per tooth. The minimum principal residual stress was negatively correlated to the spindle speed, positively correlated to the feed per tooth, and uncorrelated to the axial cutting depth. The degree of influence on optimization of machining parameters was: spindle speed > axial cutting depth > feed per tooth. The corresponding average grey correlation degree differences were 0.280981, 0.216859, and 0.013422, respectively. The maximum value of grey correlation degree in the orthogonal test was 0.874372, and the corresponding optimal parameters combination was the spindle speed 8000 r/min, feed per tooth 0.03 mm/z, and axial cutting depth 0.2 mm/r. [ABSTRACT FROM AUTHOR]

Effect of the external surface layer on the phase transition (PT) between the low pressure phase and high pressure phase (HPP) in a NiAl bicrystal is investigated. Using a phase field model, the external surface layer is included, within which the elastic properties and surface energy are properly distributed. After resolving a stationary layer, the coupled phase field and elasticity equations are solved to capture the HPP evolution. Residual stress concentrator is included as a shear band representing an inelastic shear strain. Due to the small grain size, the surface layer can influence the stress distribution and consequently, the critical inelastic shear strain γ cr for the HPP growth. Above a certain applied pressure, the surface layer width Δ ξ shows no effect on γ cr , e.g., P = 10 GPa for the grain size of L = 20 nm. For lower pressures, γ cr increases as pressure reduces. Due to the interplay of size addition by the surface layer and size reduction by the transformation strain, γ cr reduces versus Δ ξ and then increases for larger Δ ξ . For smaller grain sizes, the surface layer effect is promoted as it is imposed to a larger transformation work. The lowest γ cr is obtained for P = 19 GPa, in good agreement with the theoretical pressure of 20 GPa. Combining the external shear on pressure adds an extra shear term to the transformation work, which allows for the relaxation of the shear band and results in a nonlinear reduction of the PT pressure versus applied shear. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) enables the production of complex geometries that are not accessible by conventional processes. Fused deposition modeling (FDM) 3D printing is an important choice for many industries, particularly for additive manufacturing of microelectronic systems. The various physical properties of printing polymer materials, such as geometry, rheological behavior, and others, need to be taken into account in the printing process. In our study, a semi-crystalline polypropylene polymer PP is used in the FDM process, as it is characterized by deformability due to crystallization. We investigate the thermomechanical behavior of a semi-crystalline polymer PP (polypropylene) with different material deposition geometries ranging from a parallelepiped filament to a cylindrical filament in a numerical model developed. A coupling (to temperature vs. time evolution during printing) of solid mechanics, heat transfer, and crystallization kinetics equations was considered to build the Multiphysics numerical model capable of predicting temperature profiles, residual stresses, and degree of crystallization during the FDM process. The results obtained with the numerical model provide a reliable approach to predicting and adjusting the actual thermomechanical behavior of a printed electronics package. The values are calculated and compared to the six points in the two samples. The results show that the change in deposit shape resulted in a maximum deviation of 3.3 MPa for residual stress and 0.376 for the degree of crystallization, while a decrease was observed in the selected points with an average deviation of 1.81 MPa and 0.193 for residual stress and the degree of crystallization, respectively. This is due to the effects of the modification of the shape model on the temperature profile model, with the change in the 3D structures of the printed polymer material; the methodology presented in this paper allows the numerical model to be validated with an experimental study of the literature. The paper proposes future work and an experimental study to validate the results of the numerical model. [ABSTRACT FROM AUTHOR]

A computational model of ternary ion exchange (IOX) for strengthening glass is proposed to predict the cation concentration and residual stress distributions in glass after ternary IOX. The comparison between theoretical predictions and experimental results indicated the validates the model. Additionally, it provides a method to determine ion diffusivity and volume expansion through ternary IOX experiments. Simulations of K–Na–Li ternary IOX were conducted using the parameters calibrated based on experimental results from a thick silicate glass. Then the process parameters were changed to clarify their influences. Key findings reveal that for thick glass (where lateral expansion is negligible), the optimum ratio of K+ and Na+ concentrations in a molten salt is 2:1. We further consolidate the effects of process parameters by training a neural network (NN) and demonstrate that the NN can be a surrogate model to replace the time‐consuming simulations, which could be more adaptable by the glass industry. [ABSTRACT FROM AUTHOR]

The ultrasonic rolling processing technology has been shown to significantly reduce surface roughness and enhance the residual stress of parts, thereby improving their surface properties and extending their service life. This technology is particularly effective for the precision machining and surface strengthening of ultra-high-strength steel 42CrMo. This study aims to investigate the impact of turning pre-processing on the distribution of residual stress during ultrasonic rolling, a simulation model incorporating turning pre-processing was developed and used to conduct ultrasonic rolling simulation experiments, enabling the analysis of residual stress distribution patterns. Concurrently, ultrasonic rolling strengthening experiments were performed to validate the accuracy of the simulation model. The results confirm that with increasing rotational speed and feed rate, residual stress decreases, whereas with increasing static pressure and amplitude, residual stress increases. The residual stress variation obtained from the simulation of combined turning and ultrasonic rolling closely matched the results of experimental ultrasonic rolling tests. This consistency validates the accuracy of the simulation model. This study offers a novel approach for simulating and experimentally validating ultrasonic rolling processes, particularly for shaft-like parts that undergo turning as a pre-processing step. [ABSTRACT FROM AUTHOR]

This paper presents a study on residual stress measurement in wire-arc additively manufactured (WAAM) titanium samples using the non-destructive method of phased array ultrasonics. The contour method (CM) was used for the verification of the phased array ultrasonic results. This allowed for a comparison of measurement methods to understand the effects on the distribution of residual stress (RS) within Ti-6Al-4V samples and the effectiveness of measurement of residual stress using phased array ultrasonics. From the results of the experiments, the phased array ultrasonic data were found to be in good agreement with the CM results and displayed similar residual stress distributions in the samples. The results of the individual elements of the phased array were also compared and an improvement in accuracy was found. From per-element results, anomalies were found and could be mitigated with the ability to average the results by using phased array ultrasonics. Therefore, based on these results, there is a strong case for the benefits of using phased array ultrasonics as a method of residual stress measurement for WAAM Ti-6Al-4V components over other existing residual stress measurement techniques. [ABSTRACT FROM AUTHOR]

Lattice structures become the focus for scholars to research due to its unique lightweight, high impact resistance and ideal noise reduction. Selective laser melting has become a very effective and convenient method for preparing lattice structures of excellent quality. However, it is imperative to acknowledge that rapid heating and cooling processes inherent to the method can generate excessive residual stresses within the lattice structures, thereby significantly compromising their mechanical properties. To address this issue, the present study seeks to elucidate the patterns and characteristics of distribution of residual stresses and deformations within simple cubic lattice structures, employing a combination of experimental techniques and finite element analysis. The fabrication of these simple cubic lattice structures is accomplished through selective laser melting. The investigation encompasses both two methods, involving X-ray measurements at discrete points on the structure, and finite element simulations to depict the overall stress distribution. The results show that the residual stress and deformation are more likely concentrated on the initial surface to be processed, and residual stress on the substrates is bigger than that on bars. Specifically, the biggest stress concentrates on the Z-bars, up to 1393 MPa. However, in terms of the overall state of stress distribution in the structure, the residual stress on the substrate is slightly higher than that on the lattice structure. [ABSTRACT FROM AUTHOR]

Lightweight door impact beams utilise roll forming with high-strength steels and require an additional roll-flattening process for direct bolt joints. However, conventional sheet designs fabricated using this approach are susceptible to various defects, including twisting, edge wrinkling, and cracking. This study proposes two notch designs for coil sheets: one featuring an internal hole, and the other having a dog-bone shape. The stress and strain states experienced by the sheet during the roll pass were analysed using finite element analysis. The results demonstrated that each notch design effectively altered the internal stress and strain distributions, leading to a reduction in the twist or edge defects. The internal hole design achieved a 77% reduction in edge compressive strain, mitigating wrinkling, and a 65% reduction in waviness height. However, it suffers from high longitudinal strain and strain concentration at the edge, potentially causing bow and fracture defects, respectively. The dog-bone design achieved a 78% reduction in residual longitudinal stress, preventing bow, and a 41% reduction in plastic strain at the edge. While this design leads to a two-fold increase in waviness height due to underdeformation, this remains within acceptable limits as subsequent press machine stages can address insufficient flattening. [ABSTRACT FROM AUTHOR]

Thin-walled aerospace parts have the characteristics of large size, thin wall thickness, and complex shape, etc. In the process of machining, poor rigidity and high material removal rate are easy to cause machining deformation due to uneven distribution of residual stress, and conventional detection methods and regulation means cannot meet the needs of on-site production. In order to solve these problems, an effective method of ultrasonic nondestructive in situ stress detection and ultrasonic stress regulation is proposed in this paper. Firstly, the ultrasonic residual stress detection and ultrasonic stress regulation are analyzed theoretically, and their working principles are explained, which provides a theoretical basis for the subsequent use of the equipment. Then, according to the deformable sections of large thin-walled parts in the production site, the typical characteristics are extracted to complete the design of the experimental part, and the residual stress detection and regulation of the whole machining process are studied. Finally, through two groups of comparison experiments, the changes of residual stress values in different depth ranges of parts and the changes of the flatness of the final parts are analyzed. The results show that the ultrasonic critical refraction longitudinal wave (LCR wave) method can be used to detect the residual stress of thin-walled parts in different depth ranges, and the ultrasonic stress regulation method can reduce and homogenize the stress of thin-walled parts, and the machining deformation and conformal ability of the parts are significantly improved after the stress regulation. [ABSTRACT FROM AUTHOR]

The restoration of large support rollers poses an industrial challenge due to the high energy consumption of traditional repair methods. Consequently, a novel approach for repairing support rollers has been introduced and tested on thick-walled components. Finite element simulations aided the study of welding repairs for large thick-walled components, examining element distribution, microstructure, mechanical properties, and residual stress distribution across various processes. The results indicate that employing ABAQUS2023 finite element software to analyze stress variations under different working conditions, the Dynamically Controlled Low-Stress No-Distortion method effectively mitigates residual stresses both during and post welding, reducing average transverse residual stresses by 14.5% and average longitudinal residual stresses in the weld zone by 29.1%. The Dynamically Controlled Low-Stress No-Distortion method narrows the high-temperature range of the heat source, consequently decreasing the size of the heat-affected zone by 33.3% compared to conventional welding. The microstructure featured dendrites and equiaxed columnar crystals, with the Dynamically Controlled Low-Stress No-Distortion method capable of grain refinement, transforming some equiaxed columnar crystals into cellular structures. As grains were refined, microhardness improved, with the covering layer's microhardness rising by 14.68%. A comparison between simulated and measured values of lateral and longitudinal residual stresses at corresponding points revealed discrepancies of 14.6% and 20.5% in accuracy, respectively. [ABSTRACT FROM AUTHOR]

Advanced high-strength steels (AHSSs) with Zn coatings are commonly joined by the resistance spot welding (RSW) technique. However, Zn coatings could possibly cause the formation of liquid metal embrittlement (LME) cracks during the RSW process. The role of a Zn coating in the tensile–shear fatigue properties of a welding joint has not been systematically explored. In this study, the fatigue properties of tensile–shear RSW joints for bare and Zn-coated advanced high-strength steel (AHSS) specimens were comparatively studied. In particular, more severe LME cracks were triggered by employing a tilted welding electrode because much more stress was caused in the joint. LME cracks had clearly occurred in the Zn-coated steel RSW joints, as observed via optical microscopy. On the contrary, no LME cracks could be found in the RSW joints prepared with the bare steel sheets. The fatigue test results showed that the tensile–shear fatigue properties remained nearly unchanged, regardless of whether bare or Zn-coated steel was used for the RSW joints. Furthermore, Zn mapping adjacent to the crack initiation source was obtained by an electron probe micro-analyzer (EPMA), and it showed no segregation of the Zn element. Thus, the failure of the RSW joints with the Zn coating had not initiated from the LME cracks. It was concluded that the fatigue cracks were initiated by the stress concentration in the notch position between the two bonded steel sheets. [ABSTRACT FROM AUTHOR]

Hybrid titanium carbon laminates (HTCLs) are a new type of fiber metal laminates, that are attracting extensive attention due to their comprehensive mechanical and physical properties. The curing stress is an important factor affecting the manufacturing performance of HTCLs. Based on viscoelastic mechanics and temperature variation characteristics of materials in this work, the multi‐physics field coupling modeling and simulation are conducted, and the stress evolution mechanism during HTCLs curing process is investigated. Furthermore, the interlayer interfacial damage of HTCLs induced by the curing stress is analyzed combined with the microscope images. Results show that the restriction of metal layers and the stacking sequence of carbon fiber prepregs are the primary reasons for generating significant stress during HTCLs curing. The secondary insulation stage of HTCLs curing process has a positive effect on suppressing the curing stress, by which the interfacial stress between the different metal layers and prepregs layers can decrease by 10.53%, 4.06%, 10.24%, and 1.11%. From the beginning of cooling to the end of curing, the residual stress in HTCLs increases rapidly, and the maximum can increase by 197%. Stress concentration is easily generated on the edges of HTCLs, and the interfaces near the bottom of HTCLs are more prone to forming cracks and delamination. Highlights: A multi‐physics field coupling model for HTCLs curing process is established.The viscoelastic mechanics and the temperature variation characteristics of materials are considered in this model.The stress evolution mechanism during HTCLs curing is studied.The interface damage of HTCLs induced by the curing stress is analyzed combined with experiments. [ABSTRACT FROM AUTHOR]

Soft tissue growth is crucial across various physiological applications, with mathematical modelling playing a pivotal role in understanding the underlying processes. The volumetric growth theory serves as a commonly used mathematical framework in this context. Our previous research on volumetric growth theory primarily concentrated on defining the incremental growth tensor in loaded and stressed configurations, revealing that this approach closely aligns with experimental observations of residual hoop stress distribution. However, given the assumptions employed, the approach has limitations in accurately predicting the growth timeline. In this work, we address these issues by incorporating the effect of initial residual strain and introducing a new mixed trigger growth evolution law. In this growth law, we do not use growth saturation as an upper limit, as this assumption cannot represent many physiological conditions. Instead, we propose that growth in soft tissues leads to a new equilibrium state. To illustrate this idea, we introduce a growth incompatibility function, denoted as I. We establish the analytical relationship between I and the opening angle in a simplified cylindrical geometry resembling the structure of the heart or arteries. We put forth a revised growth law that is both stress and incompatibility driven/Our results show that by using this mixed trigger growth law, tissues will not grow indefinitely. Instead, a stress-driven homeostasis incompatibility state will be reached. In addition, by accounting for the initial opening angle in the model, we can accurately trace the growth history of the heart, aligning with experimental data obtained from measuring the opening angle in young pigs from birth to maturity. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the effect of countersunk rivet head dimensions on the fatigue performance of the riveted specimens of 2024-T3 alloy. Design/methodology/approach: The relationship between rivet head dimensions and fatigue behavior was investigated by finite element method and fatigue test. The fatigue fracture of the specimens was analyzed by scanning electron microscopy. Findings: A change of the rivet head dimensions will cause a change in the stress concentration and residual normal stress, the stress concentration near the rivet hole causes the fatigue crack source to be located on the straight section of the countersunk rivet hole and the residual normal stress can effectively restrain the initiation and expansion of fatigue cracks. The fatigue cycle will cause the rivet holes to produce different degrees of surface wear. Originality/value: The fatigue life of the specimens with the height of the rivet head of 2.28 mm and 2.00 mm are similar, but the specimens with the height of the rivet head of 1.72 mm were far higher than the other specimens. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced plastic (CFRP) is a lightweight material. The automotive industry has focused on producing a steel/CFRP hybrid part to reduce overall weight. After manufacturing, delamination can occur at the interface between the CFRP and steel owing to the hybrid part constituting dissimilar materials. However, most studies have focused only on designing the manufacturing processes for the hybrid part or evaluating the adhesive used at the interface. Therefore, it is necessary to predict the behavior of the interface after demolding the hybrid part. This study aimed to predict the interface behavior of a steel/CFRP hybrid part by considering its forming and cohesive properties. First, double cantilever beam (DCB) and end-notched flexure (ENF) tests were performed to obtain cohesive parameters, such as energy release rate of modes I and II (GI, GII). The experimentally obtained properties were applied to the bonding area of the hybrid part. Subsequently, a forming simulation was performed to obtain the stress of the steel blank in the hybrid part. The stress distribution after forming was utilized as the initial condition for spring-back simulation. Finally, the interface behavior of the hybrid part was predicted by a spring-back simulation. The simulation was conducted using the residual stress of steel outer and the cohesive properties on the interface, without the application of any external forces. The cases of spring-back simulation were divided as delamination occurrence and attached state. The simulation results for prediction of delamination occurrence and bonding showed good agreement in both cases with experimental ones. The proposed method would contribute to expanding the manufacturing of the hybrid part by stamping and reducing the manufacturing cost by prediction of delamination occurrence. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V titanium alloy is known as one of the most difficult metallic materials to machine, and the machined surface residual stress distribution significantly affects properties such as static strength, fatigue strength, corrosion resistance, etc. This study utilized finite element software Abaqus 2020 to simulate the two-step cutting process of titanium alloy, incorporating stages of cooling, unloading, and de-constraining of the workpiece. The chip morphology and cutting force obtained from orthogonal cutting tests were used to validate the finite element model. Results from the orthogonal cutting simulations revealed that with increasing cutting speed and the tool rake angle, the residual stress undergoes a transition from compressive to tensile stress. To achieve greater residual compressive stress during machining, it is advisable to opt for a negative rake angle coupled with a lower cutting speed. Additionally, in two-step machining of titanium alloy, the initial cutting step exerts a profound influence on the subsequent cutting step, thereby shortening the evolution time of the Mises stress, equivalent plastic strain, and stiffness damage equivalent in the subsequent cutting step. These results contribute to optimizing titanium alloy machining processes by providing insights into controlling residual stress, ultimately enhancing product quality and performance of structural part of titanium alloy. [ABSTRACT FROM AUTHOR]

The main objective of this study is to evaluate residual stresses in AISI 316L and 18Ni Maraging 300 functionally graded materials with continuous variation of composition within a single layer using the contour method. The manufacture of this kind of layer-level continuous functionally graded materials by employing a Powder Bed Fusion-Laser Beam system utilizing a blade/roller-based powder spreading technique has only been recently devised and a proper residual stress analysis is still required. In fact, as the mechanical properties of additively manufactured samples are significantly influenced by the direction of construction, the same holds true for the direction along which the compositional variation is made. Furthermore, in this study, the impact of solution annealing and aging heat treatment, which are necessary for enhancing the mechanical properties of martensitic steel, on residual stresses was explored. Additionally, the effect of adopting material-differentiated process parameters was investigated. The results indicated that each specimen displayed areas of tensile stress concentration on the upper and lower surfaces, balanced by compression in the center. The application of heat treatment led to a decrease in the maximum tensile stress of 8% and provided a uniform and significant stress reduction within the maraging steel. Finally, the implementation of material-specific process parameters for the three composition zones in conjunction with the heat treatment resulted in a reduction in the maximum residual stress of 35% and also a significantly lower residual stress field throughout the specimen. [ABSTRACT FROM AUTHOR]

This paper develops an approximate stress distribution in a conical heap of jammed dry granular material loaded by gravity. An Eulerian formulation of elastic-inelastic response is used to explain why the residual stresses in the heap can be approximated by the current state of stress in the material. The proposed normalized stress components are functions of the normalized radial and vertical coordinates and are parameterized by only the angle of repose. It is shown that the vertical stress distribution applied to the base of the heap compares well with experiments using a rain procedure for sand deposition. [ABSTRACT FROM AUTHOR]

To evaluate the residual stresses of Stellite−6 dissimilar layers on the water erosion-prone regions of low-pressure last-stage blades, the effects of the microstructure, microhardness and cladding passes on the residual stress distributions of cladding layers are investigated carefully. Although the cladded blades undergo stress relief heat treatment, the residual tensile stress in the cladding Stellite−6 layer is 200 ~ 300 MPa, and the residual compressive stress in the substrate is − 100 ~ − 150 MPa. Due to the microstructure and property mismatch between the cladding layer and substrate, there is a great residual stress gradient at the interface of the Stellite−6 alloy layer and substrate. The addition of cladding passes on the concave side of the blade can increase the peak tensile stress to 374 MPa in the other side cladding layer; however, the cladding pass significantly reduces the residual stress gradient at the interface of the Stellite−6 alloy layer and substrate. The reduced residual stress gradient of the interface indicates that adding a cladding layer is beneficial for improving blade service safety. [ABSTRACT FROM AUTHOR]

The purpose of this study is to identify the integrity challenges encountered by buried pipeline steels, specifically to address Circumferential Near-Neutral pH Corrosion Fatigue (C-NNpH-CF). Damage to the pipeline's protective coating and corrosion conditions increase the risk of service failures caused by C-NNpH-CF. (Note that this mechanism has previously been termed near-neutral pH stress corrosion cracking.) Unlike axial cracking, circumferential cracking is primarily influenced by residual stress from pipeline bending, geohazards, and girth welds. External corrosion pits often lead to dormant cracks, with growth ceasing around 1 mm depth due to reduced dissolution rates. Investigating the impact of bending residual stress (an appropriate source of axial residual stress) and cyclic loading (simulated pipeline pressure fluctuation), the study employs the digital image correlation (DIC) method for stress distribution analysis. Factors like applied loading, initial notch depth, and bending conditions influence crack initiation and recovery from the dormancy stage by affecting stress distribution, stress cells, and stress concentration. Cross-sectional and fractographic images reveal time/stress-dependent mechanisms governing crack initiation, including dissolution rate and hydrogen-enhanced corrosion fatigue. The study emphasizes the role of various residual stress types and their interactions with axial cyclic loading in determining the threshold conditions for crack initiation. [ABSTRACT FROM AUTHOR]

Direct bonding is an attractive technique to join material components without the use of intermediate adhesive medium. Usually, the bonding interface can experience high level of residual stress concentration due to entrapped nano-scale particulate contamination. Existing theoretical models are not capable of analyzing such residual stress concentration, since they fail to consider the localized material inhomogeneity formed between the bonding pairs as result of thermal and diffusion processes. This paper proposes a new theoretical model to analyze the residual stress concentration in the bonding interface with the consideration of localized material inhomogeneity. Following the idea of Selvadurai and Singh (Int. J. Fract. 25:69–77, 1984), the nano-scaled particulate contamination induced interfacial defect is simulated as a penny-shaped crack indented by a smooth rigid disc inclusion. This mode I crack-inclusion model is interpreted as a three-part mixed boundary value problem in the theory of elasticity, which is solved by a series expansion technique. Mathematical difficulties associated with modelling arbitrary localized material inhomogeneity are overcome by the use of the General Kelvin Solution (GKS) based method. Exact analytical solutions for the stress intensity factors (SIFs) and resultant force on the inclusion are obtained. Our results show that the inclusion-crack radius ratio and the localized material inhomogeneity can have significance effect on the residual stress concentration at the bonding interface. [ABSTRACT FROM AUTHOR]

Lightweight thin-walled parts are widely used in the aviation and aerospace industries, and with the further increase in the complexity of their features, the traditional manufacturing process can no longer fully meet the high requirements of industrial component manufacturing. In this work, thin-walled parts are processed by Laser based powder bed fusion of metals (PBF-LB/M), and the effects of process parameters on residual stress, hardness, mechanical properties and microstructure of thin-walled parts are systematically investigated. The simulation results show that the maximum equivalent residual stresses are distributed in the combination of the solid and the substrate, and the minimum equivalent residual stresses are mainly distributed in the top two ends and the middle part of the solid, and the stress distribution is symmetrical. In addition, the maximum equivalent residual stress increases with the increase of laser power, and decreases with the increase of scanning spacing or scanning speed. The experimental results show that with the increase of laser energy density, the tensile strength and yield strength of thin-walled parts show a tendency of increasing first and then decreasing. Finally, high-quality thin-walled parts were successfully fabricated by the optimized process parameters, and their tensile and yield strengths were increased by 6.1% and 15.9%, respectively. [ABSTRACT FROM AUTHOR]

This study aims to improve the quality of titanium alloy structural components by introducing a remelting process into conventional selective laser melting (SLM) fabrication. To address common defects such as porosity, roughness, and stress deformation, a twofold study was conducted by developing a three-dimensional finite element model together with experimental verification. First, through a series of experiments and numerical simulation, the influence patterns of the remelting process parameters on the melt pool behavior and surface quality were investigated. The results show that excessive remelting power and insufficient remelting speed lead to an unstable melt pool, resulting in the formation of keyholes inside the melt pool and increased porosity in the formed parts. On the other hand, insufficient remelting power and excessive remelting speed can result in short exposure time of the molten pool and limited laser penetration capability, leading to incomplete melting of powder particles, thus increasing the surface roughness of the formed part. Furthermore, through experimental investigation and simulation analyses, the influence patterns of remelting strategies on the temperature field and stress distribution of the melt pool were investigated. The investigation reveals that the introduction of remelting strategies can reduce the temperature gradient of the melt pool. Because of the variation of thermal conductivity in the surrounding area, the temperature gradient at the edges was higher than that at the center for all strategies. Different laser scanning directions also resulted in varying magnitudes of residual stress in the X- and Y-directions under each strategy. In the spiral remelting path, high thermal stresses were observed at the center, resulting in higher residual stresses than those at the edges. These findings provide essential guidance for optimizing the SLM fabrication process and enhancing the quality of formed components. [ABSTRACT FROM AUTHOR]

The residual compressive stress ratio of high-strength steel (HSS) members with welded sections is significantly lower than that of common mild steel (CMS) members. However, current codes apply the residual stress results of CMS members to HSS members without adjustment. This study investigated the membrane residual stress distribution of a Q690 HSS welded H-section. The membrane residual stresses of five specimens of different sizes were measured using the sectioning method, resulting in simplified membrane residual stress distribution models. The influences of the width-thickness ratio of the flange and web and the thickness of the flange and web were analyzed. The results indicated that while the welding membrane residual stress satisfied the self-equilibrium of the section, the self-equilibrium of the plates followed an inconsistent pattern. A three-dimensional thermal elastic–plastic finite element model (3DTEFEM) was established to simulate the specimen welding process, and the measured results were used to verify the 3DTEFEM. This model was then used to conduct parameter analysis on the plate width-thickness ratio of the H-section, leading to the development of a unified membrane residual stress pattern for the Q690 steel welded H-section member. [ABSTRACT FROM AUTHOR]

Ultrasonic impact treatment (UIT) is a kind of mechanical assistive technology that can reduce the residual stress of the as-deposited metal parts. Up to now, the mechanism of ultrasonic characteristics affecting the residual stress has not been revealed distinctly. In this work, the 1Cr12Ni3MoVN deposition layer was treated by UIT with multiple ultrasonic characteristics. The results show that UIT transforms the residual tensile stress of the LMD deposition layer into compressive stress. As the amplitude increases from 20 to 30 μm, the maximum and depth of transverse residual stress observed in the vertical direction increased from 354 to 381 MPa and from 0.364 to 0.523 mm. The maximum and depth of longitudinal residual stress increased from 258 to 318 MPa and from 0.482 to 0.785 mm. As the frequency increases from 15 to 25 kHz, the maximum and depth of transverse residual stress observed in the vertical direction increased from 207 to 406 MPa and 0.301 to 0.395 mm. The maximum and depth of longitudinal residual stress increased from 240 to 326 MPa and from 0.341 to 0.517 mm. The influence of ultrasonic frequency is not as prominent as ultrasonic amplitude. The maximum impact velocity of the pin is the major factor determining the residual compressive stress field. The acceleration of the pin is positively correlated with the downward velocity of the horn. Increasing the ultrasonic amplitude can effectively increase the velocity of the horn. Once the impact energy is large enough, the σmax is basically unchanged, but the increase of impact energy can still increase the d. This work is of guiding significance for the elimination and control of residual stress in parts manufactured by LMD and other additive manufacturing methods. [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]

This study examined the joining of monolithic SiC by Si-C reaction bonding using a 100 µm-thick filler tape prepared using different SiC/C compositions (30/70, 50/50, and 70/30 wt%). Joining was performed at 1450, 1500, and 1550 °C for 1 h in a vacuum without pressure after inserting the filler tape followed by molten-Si infiltration. The sample joined at 1500 °C using a SiC/C = 70/30 filler tape revealed a dense joint morphology without pores or cracks, showing the highest joint strength of 254 MPa. A larger amount of SiC in the filler tape resulted in less residual Si at the joining interface and higher joint strength. Moreover, the distribution of residual stresses at the joint was simulated using finite element analysis, which was well-suited to experimental observations based on micro-Raman spectroscopy. [ABSTRACT FROM AUTHOR]

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Progressive induction hardening is an in-line steel heat treatment method commonly used to surface harden powertrain components. It produces a martensitic case layer with a sharp transition zone to the base material. This rapid process will induce large residual stresses, where a compressive state in the case layer will shift to a tensile state in the transition zone. For fatigue performance, it is important to quantify the magnitude and distribution of these stresses, and moreover how they depend on material and processing parameters. In this work, x-ray diffraction in combination with a layer removal method is used for efficient and robust quantification of the subsurface stress state, which combines electropolishing with either turning or milling. Characterization is done on C45E steel samples that were progressively induction hardened using either a fast or slow (27.5 or 5 mm/s, respectively) scanning speed. The results show that although the hardening procedures will meet arbitrary requirements on surface hardness, case depth and microstructure, the subsurface tensile stress peak magnitude is doubled when using a fast scanning speed. However, the near-surface compressive residual stresses are comparable. In addition, the subsurface tensile residual stress peak is compared with the on-surface tensile stresses in the fade-out zone. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical properties and residual stress of dissimilar AA3105/ AA2024 friction stir welds have been investigated. The formation of voids was observed at high rotational speeds and low transverse speeds due to the high weld heat input and abnormal stirring. The precipitate fragmentation was noticeable at higher tool rotational speed. The highest hardness was obtained at the AA2024 side of the joints due to the presence of precipitates. The results showed that the welding transverse speed has more effect on UTS than the rotational speed. Tensile residual stresses were found at the AA2024-T6 side and the welding line; while residual stresses at the AA3105 side were compressive. [ABSTRACT FROM AUTHOR]

Cold spray additively manufactured (CSAM) aluminum 6061 components are characterized by heterogeneous compressive residual stresses induced during manufacturing. This heterogeneity is further compounded by spatial variations in microstructures and mechanical properties, leading to poor inter-particle (intersplat) bonding and significant marring of overall component performance. Thermal post-processing is a keenly researched method for recovering mechanical toughness by enhancing intersplat bonding and altering highly concentrated residual stress distributions. The current work incorporates a modified microscale–mesoscale material model into a viscoplastic self-consistent simulation framework to capture material response in the as-sprayed and post-processed states. The updated model incorporates physically informed parameters emphasizing residual stresses measured experimentally through X-ray diffraction. The model calibrated using experimental tests and published literature was able to predict the stress–strain response of CSAM parts at post-heat-treated conditions. Results of the parametric study showed the significance of intersplat boundary effects on the overall yield and strain hardening of the CSAM parts. Without any information on the processing conditions of CSAM parts, the modified plasticity model predicted the deformation response using information gathered from microstructure characterization. [ABSTRACT FROM AUTHOR]

The hole-drilling method is one of the most widespread techniques to measure residual stresses. Since the introduction of the Integral Method to evaluate non-uniform stress distributions, there has been a considerable improvement in the instrumentation technology, as step increments of about 10 microns are now achievable. However, that spatial resolution makes the ill-posedness of the problem stand out among other sources of uncertainty. As the solution becomes totally dominated by noise, an additional regularization of the problem is needed to obtain meaningful results. Tikhonov regularization is the most common option, as it is also prescribed by the hole-drilling ASTM E837 standard, but it has only been studied in the reference case of a hole with no eccentricity with respect to the strain rosette. A recent work by Schajer addresses the eccentricity problem by defining a correction strategy that transforms strain measurements, allowing one to obtain the solution with the usual decoupled equations. In this work, Tikhonov regularization is applied to the eccentric hole case through the influence functions approach, in order to avoid the introduction of new error-compensating functions and bias-prone interpolations. Some useful general considerations for a practical implementation of the procedure and an experimental test case on an aluminum specimen are presented. [ABSTRACT FROM AUTHOR]

Residual stress is a key factor affecting the properties of ceramic/metal brazed joints. In this work, the residual stress of sapphire/Ti6Al4V alloy joints brazed with CuTi+B composite filler after cooling and reheated to 400 °C was calculated by finite element numerical simulation method. The effect of the B content in the filler and the filler thickness on the residual stress distribution of brazed joints after cooling was studied. The results show that the residual stress is mainly concentrated in the area near the filler layer. The maximum von Mises stress is located in the filler layer and a large Z-axial (the direction perpendicular to the brazed surface) tensile stress is on the sapphire near the filler layer. The B content and the filler thickness have no significant effect on the distribution of residual stress, but they have a certain effect on the value of residual stress of the sapphire near the filler layer. The von Mises stress and the Z-axial stress of this area increase with the increase of B content, and they decrease first and then increases with the increase of filler thickness. When the sapphire/Ti6Al4V joint is reheated to 400 °C, its residual stress significantly reduces and the residual stress on the periphery of the filler layer changes from compressive stress to tensile stress. As the B content is 1 and 3 wt%, the sapphire/Ti6Al4V joint with a smaller residual stress can be obtained. The microstructure observation and shear tests of the joints show that cracks appear in the high stress concentration area and the fracture starts from the area with maximum axial tensile stress, which verifies the accuracy of the simulation results. [ABSTRACT FROM AUTHOR]

Residual stresses in sheet metal parts are internal stresses that remain after the release of elastic strains at the end of metal forming operations. When the formed sheet metal part is removed from the forming tools, it not only springs back but also acquires a through-thickness residual stress distribution. Residual stresses for monolithic aluminum sheets and aluminum/polypropylene/aluminum sandwich laminates after springback of a U-channel formed by draw bending are presented in this paper. The forming stresses at the end of punch travel and residual stresses at the end of punch withdrawal are numerically determined using LS-DYNA, a well-established nonlinear finite element software. The through-thickness forming stress distribution is determined using an explicit forming simulation, following which the through-thickness residual stress distribution is determined using an implicit springback simulation. Stress distributions are studied at the die corner, punch corner and along the wall of the U-channel. Both forming and residual stresses in the sandwich laminate are found to be lower than those in monolithic aluminum of equivalent thickness. In sandwich laminates with the same skin thickness, higher residual stresses are observed in the skin layers as the core thickness is increased. The residual stresses at the punch corners of the formed U-channels are more influenced by changes in the die and punch corner radii than at the die corner. [ABSTRACT FROM AUTHOR]

In this paper, a mechanics-based phase-field model at the microscale is introduced for microstructure evolution during solidification. The couple phase-field model consists of Allen–Cahn equation for phase order parameter, Cahn–Hilliard equation for composition, heat conduction and elasticity equations. The introduced elastic energy allows for volumetric inelastic strains due to melting/solidification as well as a thermodynamically consistent solid-melt interface stress and consequently, residual stresses during solidification at the microscale and deformation can be captured. The computational microcell is considered at the melt-solid interface and the temperature as a time dependent function is used for its boundary conditions to solve the coupled phase-field model. Using COMSOL FE code, examples of columnar growth are studied. As result, the suppressive effect of elastic driving forces and the reduction in solidification rate, due to the volumetric inelastic strains, on solidification are revealed. The inelastic surface stress, concentrated inside the interface, can change the morphology of solidified structure but does not show a remarkable effect on the solidification rate. The thermal strain was included which reduced the effect of volumetric transformation strain and consequently, the internal stresses near constrained regions were decreased. The effect of undercooling was studied which showed that increasing the undercooling increased the temperature gradient in the vertical direction and near the interface and solidification rate and significantly changed the morphology of solidified structure, as a homogeneous growth was resolved for larger undercooling while a columnar growth was obtained for smaller undercooling. Solidification was studied under mechanical loading which showed external loading changes the stress distribution and magnitude and the morphology of solidified structure. Effect of an inclusion on solidification was also investigated. The inclusion represented a more homogeneous distribution of stress and temperature with different magnitudes compared to the rest of the sample, creating a directional solidification toward the inclusion. [ABSTRACT FROM AUTHOR]

The effectiveness of high-frequency mechanical impact (HFMI) treatment is studied in this paper considering the reasons of the fatigue life improvement of S335 steel T-welded joints with non-load transverse stiffeners. The main attention is paid to the synergic effects of macroscopic and microscopic residual stresses induced by HFMI post-weld processing as the key factors for superior fatigue life. Macroscopic residual stresses and their distribution nearby (at a distance of 3 mm) and away from (13 mm) the weld toe or the HFMI-produced groove were studied by electronic speckle interferometry and x-ray diffraction (sin2ψ-based method). It was established that HFMI treatment resulted in the transformation of the welding-induced tensile residual stresses (of about yield stress (~ 0.9 σY)) into compressive ones (of ~ 0.9 σY) near the weld toe, while the stresses did not relax away from the HFMI-formed groove. Microscopic residual stresses induced by HFMI were studied as a factor affecting the physical broadening (full width on half maximum—FWHM) of the x-ray diffraction maxima. The correlations of microscopic stresses (lattice micro-strains) with dislocation density, strain-induced dissolution of cementite, and carbon content in the ferrite lattice observed by TEM and the HFMI-induced crystallite refinement with surface hardness are discussed. For various HFMI treatment working speeds employed (1, 5, and 10 mm/s), the hardened layer depths of the S335 steel specimens were in the range of 0.6–1.0 mm. After HFMI, the fatigue strength of the T-welded joint of the S335 steel was observed to be increased by 54% (from 163 to 251 MPa) at 2 × 106 cycles, and fatigue life prolongs by 10 times. [ABSTRACT FROM AUTHOR]

In contact mechanics analysis, load, deformation, friction, and residual stress are important variables that need to be considered to understand the behavior of materials under contact for application in biomedical industry. This study investigated the effect of load, diameter ratio, and friction coefficient on the contact behavior between two hemispheres of equal hardness. The finite element method (FEM) used in this study incorporated variations in load (2500 N, 5000 N, and 8000 N) and friction coefficient (0, 0.05, 0.1, 0.4, 0.8) to detect the impact of these factors on residual stress and deformation springback in the diameter ratio ranging from 1 to 5. The upper hemisphere had a constant diameter, while the diameter of the bottom hemisphere was varied according to the chosen diameter ratio. The results showed that an increase in the diameter ratio caused a decrease in the deformation ratio, indicating that smaller hemispheres experienced an increase in deformation. The study also found that the model showing springback will decrease with increasing load and diameter ratio. The load and diameter ratio affected the springback and residual stress of the hemispheres. Large loads led to reduced springback and high residual stress. Higher diameter ratios resulted in lower springback and wider residual stress distribution in the bottom hemisphere and reduced residual stress distribution in the upper hemisphere. The friction coefficient also affected the residual stress distribution. Therefore, appropriate load, diameter ratio, and friction coefficient selection are crucial factors for producing high-quality products in biomedical industry. [ABSTRACT FROM AUTHOR]

Large temperature gradient will produce high residual stress during laser powder bed fusion (LPBF). In metal matrix composites (MMCs), the thermal-induced stress distributes complexly. It is indispensable to study the interfacial stress of MMCs during LPBF process. In this study, a multi-phase finite element model was established to reveal the temperature and stress distributions of TiB2/Al-Si composites fabricated by LPBF. Influences of particulate geometries on the residual stress were also analyzed in the model. The numerical results indicate that the residual stress in the composites was induced by high temperature gradient and coefficient of thermal expansion mismatch simultaneously. TiB2 reinforcing particles suffer large compressive stress perpendicular to the interface. In the matrix, the stress component at the interface is negative and increases rapidly with distance from the particle increases. The interfacial compressive stress lessens the mean tension stress in the nearby regions of the matrix. Maximum von Mises stress is generated at the interface in the matrix, which may cause defects and cracks. High interfacial stress was generated in the vicinity of the vertex of cubic particles and the internal stress large in ellipsoidal particles, indicating that particles with fewer edges and smaller slenderness ratio possess greater thermal shock resistance. [ABSTRACT FROM AUTHOR]

Using finite element methods, residual stresses were estimated in pipe welds. Experiments were also conducted to verify the numerical results. An alternative to a three-dimensional model was used to simplify the numerical calculation for residual stresses investigation. Model predictions were validated by measuring residual stresses using X-ray diffraction. As compared to measured residual stress distributions, the computational approaches developed in this study can accurately predict welding residual stress distributions. The focused welding parameters have a significant impact on residual stresses even when all the other parameters are the same. [ABSTRACT FROM AUTHOR]

A new method to achieve friction stir processed parts with higher wear resistance and lower residual stress values was presented. The underwater stationary shoulder FSP process (USSFSP) was investigated using experimental and numerical methods. Also, the presented process was compared with the conventional underwater FSP method (UCFSP). An improved CEL simulation method was used to prevent errors in the contact boundary between Eulerian and Lagrangian domains. Heat input was reduced significantly and resulted in a fine microstructure with higher microhardness and lower residual stresses. Temperature field was concentrated around the pin and caused a symmetrical residual stress distribution. The distribution area of Von-Mises and longitudinal stresses during the USSFSP was significantly narrower than the UCFSP process. The stress distribution around the UCFSP tool was compressive, and tensile stress was produced at further distances. However, the longitudinal stress distribution in the USSFSP was completely opposite. Tensile stress was generated in the lower part of the thickness and compressive stress in the upper part and in locations away from the centerline. This method caused the formation of a compressive residual stress region and considerably reduced the width of the tensile residual stress zone. By increasing the hardness and decreasing the residual stress level, the USSFSP proved to be instrumental in improving the material's wear resistance. The wear rate in the stir zone undergoes a substantial reduction, decreasing from 5.6 × 10−3 mm3/m in UCFSP to 1.4 × 10−3 mm3/ m in USSFSP. [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]

Additive friction stir deposition (AFSD) is an emerging solid-state additive manufacturing process with a high deposition rate. Being a non-fusion additive manufacturing (AM) process, it significantly eliminates problems related to melting such as cracking or high residual stresses. Therefore, it is possible to process reactive materials or high-strength alloys with high susceptibility to cracking. Although the residual stresses are lower in this process than with the other AM processes, depending on the deposition path, geometry, and boundary conditions, residual stresses may lead to undesired deformations and deteriorate the dimensional accuracy. Thermal cycling during layer deposition, which also depends on the geometry of the manufactured component, is expected to affect mechanical properties. To this day, the influence of the deposit geometry on the residual stresses and mechanical properties is not well understood, which presents a barrier for industry uptake of this process for large-scale part manufacturing. In this study, a stepped structure with 4, 7, and 10 passes manufactured via AFSD is used to investigate changes in microstructure, residual stress, and mechanical property as a function of the number of passes. The microstructure and defects are assessed using scanning electron microscopy and electron backscatter diffraction. Hardness maps for each step are created. The residual stress distributions at the centreline of each step are acquired via non-destructive neutron diffraction. The valuable insights presented here are essential for the successful utilisation of AFSD in industrial applications. [ABSTRACT FROM AUTHOR]

Belt grinding is commonly applied for precision manufacturing of difficult-to-machine materials like GH4169, owing to its satisfactory elastic grinding properties, high efficiency, and strong adaptability. Abrasive belt wear is a common occurrence during the grinding process; however, its mechanism and effect on machining quality, particularly its influence on residual stress (RS), remain unclear. In order to compensate for these shortcomings, by means of experimentation, this paper studies how the RS distribution of GH4169 plate is affected by abrasive belt wear during robotic belt grinding, and the influence mechanism is analyzed from the perspectives of grinding force and heat. Firstly, the whole life cycle of the abrasive belt is determined through a wear test, then a novel evaluating index based on relative material removal rate is proposed to quantitatively characterize the wear conditions of belt. Secondly, according to the new division criteria, abrasive belts at various wear stages are created, and then, comparative grinding experiments of the GH4169 plate are carried out. Finally, based on the experimentally measured data, this paper fully analyzes and discusses the surface and subsurface RS distribution differences of grinding traces. The experimental findings suggest that the effect of abrasive belt wear on the surface RS distribution is notable in the grinding direction, but not in the vertical direction of the grinding traces. Additionally, as the belt conditions deteriorate, the overall grinding force ratio decreases while the accumulation of grinding heat increases, which leads to the generation of surface residual tensile stress (RTS) in the grinding direction. Furthermore, as a result of the uneven heat diffusion, the surface RS along the vertical direction of the grinding traces is distributed in an approximately symmetrical manner, with higher RS values in the center and lower values on the sides. As for the subsurface RS distribution, on the whole, with the progression of belt wear, the values of the subsurface residual compressive stress (RCS) layer decrease. [ABSTRACT FROM AUTHOR]

The threshold stress intensity factor (Δ K th) has dependent on the crack size during the propagation of microfatigue cracks. Ando et al. proposed a new surface crack nondamaging technology to evaluate this dependence. This technology has been validated in situations where the stress ratio is positive (R > 0). However, to expand the application range of this technology, it is necessary to verify its applicability in the case of stress ratio R < 0. Therefore, this applicability was examined based on the results of the previous experiments. This study aims to investigate the effect of the residual stress distribution (RS1) of cavitation peening (CP) in the case of R < 0 on the harmless crack size ( a hml ) of steel with crack-like surface defects. To compare with the residual stress distribution (RS1) of CP, two types (RS2 and RS3) with different residual stress distributions were used. The surface residual stresses of RS1, RS2, and RS3 were the same, but the distribution of depth from the surface was different. Compressive residual stress is the dominant factor that renders surface defects harmless. The depth of the residual stress significantly influenced a hml . Moreover, the trend of the defect size that can be rendered harmless, estimated based on fracture mechanics, was slightly larger than that of the experimental results. However, surface crack nondamaging technology can be applied even when the stress ratio is negative (R < 0). [ABSTRACT FROM AUTHOR]

The stress distribution in sealing glass is one of the most concerning issues for glass‐to‐metal (GtM) seals. In this study, photoluminescence spectroscopy was applied by exploiting the piezospectroscopic effect of Cr‐doped α‐Al2O3 (ruby), and the overall stress distribution along the radius of a concentric seal was detected and analyzed. It was discovered that the compressive stress first increased and then decreased at the edge of the seal. The maximum compressive stress of 91 MPa was detected at ∼20 µm from the interface and was ascribed to the interaction between the glass and surface oxide film of the metal. Stress distributions in pore regions were also investigated and obvious stress fluctuations were observed clustering around pores. A circle of compressive stress was observed around the pores in a single glass without a metal housing; for the pores in the center of the concentric seal, the stress distribution was dominated by the inner contraction of the metal housing; and for the pores near the edge of the seal, the concentration of tensile stress located perpendicular to that of the compressive stress. This study demonstrates a high‐resolved and nondestructive method to detect the stress field and explores the potential for future tailorability of stress distribution in GtM seals. [ABSTRACT FROM AUTHOR]

The current investigation involves the fabrication of fifteen samples of austenitic stainless steel 316 L (SS316L) utilizing laser powder bed fusion technology to evaluate the residual stresses through the impact of energy density, which was varied between 30 J/mm3 and 111 J/mm3 by varying process parameters, notably scanning speed and laser power. The energy density range suggested by existing literature has been found to have samples with significant mechanical properties, apart from its impact on residual stress, which can affect the service life of the product. The primary focus of this study is to identify the optimal window for achieving residual stress at various locations within the sample. The study discovered differences in residual stress development at all tested locations. When employing lower laser powers of 140 W and 160 W, residual stress formation remained consistent. Furthermore, when the laser power exceeds 140 W to 160 W, a substantial temperature gradient develops, leading to a considerable rise in tensile stress magnitude. The variation in energy density does not affect residual stress, while there is a variation in two process parameters, laser power and scanning speed, simultaneously. A laser power range of 140 W to 160 W, combined with scanning rates ranging from 500 mm/s to 1100 mm/s, results in a consistent range of minimal residual stress formation across multiple locations. The key outcomes of the study show the crucial role of laser power and scanning speed in residual stress development, which has implications for improving mechanical characteristics and product service life by generating minimal residual stresses. [ABSTRACT FROM AUTHOR]

This study examines the impact of cutting parameters on the fatigue properties of FeCoCrNiAl0.6 high‐entropy alloy under bi‐directional micro‐cutting. Utilizing Abaqus/fe−safe for analysis, we evaluated surface roughness, internal stress distribution, and fatigue longevity. Enhanced cutting speed resulted in smoother surfaces, whereas increased cut depth intensified surface roughness. Optimal cutting at 60,000 mm/min and 40 μm depth yielded a notable 91% rise in compressive stress (207 MPa) compared to slower speeds (108 MPa at 30,000 mm/min). Yield strength remained stable at 700 MPa across conditions. Fatigue resistance improved post‐bi‐directional cutting, with a 21.8–26.6% boost in life cycles, highlighting a consistent 10% advantage over single‐direction cutting. Highlights: The influence of bilateral micro‐cutting on fatigue performance was studied.The influence of micro‐cutting parameters on fatigue properties is studied.The release and transformation mechanism of residual stress in bilateral micro‐cutting is studied. [ABSTRACT FROM AUTHOR]

This study explores the numerical analysis of effective stress and distortion (dimensional variations) in bulk deposited structures of Inconel 625 alloy with seven different deposition strategies using wire arc additive manufacturing (WAAM) process. Due to the challenges in detecting in-situ stress changes during bulk deposition, numerical analysis is employed to approximate stress distribution. The goal is to investigate stress and distortion (dimensional variations) in the build direction (BD), longitudinal and transverse directions, and understand their impact on anisotropy and asymmetry. The findings reveal distinct patterns in effective stress, with initial decrease in bottom, followed by a gradual increase at the middle and rapid increase thereafter, regardless of deposition strategies. Parallel and contour deposition strategies exhibit lower effective stress compared to spiral strategies. Distortion (dimensional variations) along the BD increases with height, and parallel strategies result in higher distortion. The parallel strategies show increasing distortion from one edge to the other, while spiral and contour strategies lead to high distortion at the center. The parallel and contour deposition strategies exhibit higher compressive stress at the bottom and middle compared to the spiral strategies. Anisotropy analysis indicates higher stress anisotropy in parallel and contour patterns, but lower distortion anisotropy compared to spiral patterns. Empirical equations are developed to understand the relationship between stress, distortion (dimensional variations) and hardness. The study suggests that higher effective stress can adversely affect material yielding behavior. This study undertakes a comparison between FEA and analytical model which reveals a close alignment in the residual stress distributions in the build direction. [Display omitted] ● Residual stress and distortion behaviour of seven deposition strategies are numerically analyzed. ● Residual stress in bulk deposition decreases at bottom, increases in middle and top. ● Parallel strategies result in lower horizontal stress and distortion compared to spiral and contour. ● The compressive stress in the parallel and contour strategies is significantly higher than that the spiral. ● Parallel and contour strategies exhibit greater stress anisotropy but lower distortion anisotropy. [ABSTRACT FROM AUTHOR]