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The use of thin films made of alloys, i.e., containing multiple metal species, can enhance their properties. However, as with single-element films, residual stress in the films can limit their performance. A model is proposed for relating the stress in alloy thin films to the processing conditions (growth rate, temperature, and sputter-gas pressure), material properties (composition, atomic and defect mobilities, and elastic moduli), and microstructure (grain size and grain growth kinetics). The model is based on stress-generating processes that occur during film growth at grain boundaries and due to energetic particle impacts. While the equations are similar to those proposed for single-element films, the alloy kinetic parameters now contain the effects of the different atomic species. The model is used to explain the growth rate and composition dependence of in situ stress evolution during the deposition for various concentrations in the tungsten–vanadium system. [ABSTRACT FROM AUTHOR]

The dynamics of residual stress (RS) within glass-to-metal (GTM) seals play a crucial role in their operational efficacy, with the progression of RS in response to temperature variations being a critical aspect in engineering applications. This research utilizes fiber Bragg grating sensors and temperature-calibrated photoluminescence spectroscopy techniques for the in situ monitoring of RS changes within GTM seals during heating. Initially, the glass body exhibited a compressive stress of −203 MPa, while the stress in the glass close to the interface was −367 MPa at room temperature. With increasing temperature, RS within both the glass body and in the glass close to the interface transitions through three distinct phases: a near-linear decrease, a rapid decrease, and a shift from compressive to tensile stress. By 540 °C, tensile stresses of approximately 11 MPa within the glass body and 36 MPa in the glass close to the interface were observed. The study elucidates that RS evolution is intricately linked not only to the thermal expansion properties of the constituent materials but also to the β-relaxation phenomenon within the glass structure and the presence of an oxide layer at the interface. Finite-element analysis simulations were conducted to corroborate the experimental findings, illustrating a congruent RS evolution pattern and delineating the transition from a compressive to a tensile state. This investigation provides empirical data and analytical insights concerning the management of RS in GTM seals, underscoring the significance of RS control in maintaining seal integrity. [ABSTRACT FROM AUTHOR]

We present a method for computing locally varying nonlinear mechanical properties in particle simulations of amorphous solids. Plastic rearrangements outside a probed region are suppressed by introducing an external field that directly penalizes large nonaffine displacements. With increasing strength of the field, plastic deformation can be localized. We characterize the distribution of local plastic yield stresses (residual local stresses to instability) with our approach and assess the correlation of their spatial maps with plastic activity in a model two-dimensional amorphous solid. Our approach reduces artifacts inherent in a previous method known as the "frozen matrix" approach that enforces fully affine deformation and improves the prediction of plastic rearrangements from structural information. [ABSTRACT FROM AUTHOR]

A study of residual mechanical stresses in the surface layer of the HgCdTe/CdTe/ZnTe/GaAs structure based on the registration of the second harmonic signal characteristics of reflected IR laser radiation from the surface of the studied sample passed through a nonlinear crystal was carried out. It is shown that such a sensitive method makes it possible to obtain information about the anisotropy of the polarization of the reflected radiation, caused by the residual deformation. Observations of the fine structure of the angular sweep of the second harmonic signal suggest a complex structure of residual stresses related to the presence of misoriented areas. The results were compared with data obtained from measurements of the azimuthal dependence of the self-reflected second harmonic signal from the sample surface. [ABSTRACT FROM AUTHOR]

The AA2219 is an Al-Cu alloy with widespread engineering applications. The sheet parts of this alloy are produced by metal forming and are subjected to age hardening (e.g., T6 temper) for strengthening. The cold work in metal forming affects the ageing behavior of alloy and hence the resulting mechanical properties. In this research, a novel forming technique namely Incremental Forming with three different forming-ageing routes is employed to produce age-hardened AA2219 parts. The resulting microstructure evolution, mechanical properties, and residual stresses are examined. The results reveal that forming imposed cold work (35% plastic strain) enhances the sheet strength and hardness to a certain extent, which can be further enhanced by opting an optimum forming-ageing route. Similarly, the residual stresses also show sensitivity to the forming-ageing route opted. Based upon extensive analysis of the experimental results, it is concluded that the [O-IF-ST-T6] route is the most appropriate route for producing age-hardened parts with high strength, hardness and ductility, and low residual stresses (where O, IF, ST, and T6 represent parent, incremental forming, solution treatment and T6 ageing, respectively). This route is found to offer a gain of 238% in the tensile yield strength, 151% in the ultimate tensile strength, and 200% in the hardness with respect to the parent metal. Further, from several correlations drawn between mechanical properties and microstructural quantities, namely grain size, and precipitate's size and density, strengthening mechanism is revealed for the reported gains. [ABSTRACT FROM AUTHOR]

To alleviate residual stress of ZrO 2 /GH536 brazed joints, the micro-scale structures were fabricated on ZrO 2 via selective laser melting technology before its vacuum brazing with GH536 superalloy. The effects of micro-scale structures on the interfacial microstructure and residual stress of brazed joints were studied. The characterization results indicated that due to its reaction with excessive Ti elements from filler, the micro-scale structures prevented the detrimental effect of over-thick brittle reaction layer on the mechanical properties of joints. Furthermore, the Invar effect of the micro-scale structures facilitated the transfer of residual stress from the ceramic side to the micro-scale structures. According to the numerical simulation results, the maximum residual stress in the brazed joint with micro-scale structures decreased from 622 MPa to 310 MPa. As a result, the fracture path was changed from the flat shape to zigzag. This work reveals the stress-relaxed mechanism of micro-scale structures and provides a new method for fabricating the ceramic/metal joints with low residual stress. [ABSTRACT FROM AUTHOR]

This study examines the impact of the bonding temperature parameter on the quality of diffusion brazing joints of B 4 C ceramics using a Ni-Cr-Si-Fe-B interlayer. Various factors including shear strength, hardness, microstructure, interfacial phenomena, elemental diffusion patterns, formed compounds and phases, and fracture surfaces of the samples were analyzed and compared. The brazed sample at 1110 °C for 1/2 h exhibited the highest shear strength of 62 MPa. Increase of the bonding temperature to the optimum level (1090–1110 °C) enhances the fluidity of the molten interlayer, facilitating its diffusion into the porosities of the ceramic components. This increase also promotes higher interactions within the system, creating favorable conditions for element diffusion. However, surpassing the optimum temperature (1110–1130 °C) may lead to increased destructive reactions and intensify the impact of the coefficient of thermal expansion (CTE) mismatch, resulting in residual stresses and a subsequent decrease in bond strength. The excessive increase in the bonding temperature (1130–1150 °C) can lead to the excessive fluidity of the molten interlayer, potentially causing effusion onto the joint's fixture and damaging the samples. The results indicate the formation of various compounds between the elements of the interlayer and carbon and boron elements, including SiC, Ni 4 B 3 , CrB 2 , Fe 2 B, Ni 6 Si 2 B, and B 2 Fe 3 Ni 3 , at the fracture surface of the sample bonded at 1110 °C. The more substantial peaks of these compounds, compared to other samples, could be a reason for the higher strength of this particular sample. [ABSTRACT FROM AUTHOR]

To minimize bowing in a gallium nitride (GaN) template, which is caused by differences in the properties of the GaN film and the sapphire substrate, we studied how to offset bowing by directly growing GaN using the hydride vapor phase epitaxy (HVPE) method on the frontside of a pre-strained sapphire substrate prepared using a backside grinding process. The relationships between the respective thicknesses and stresses of the undamaged sapphire, damaged sapphire, and GaN layers were analyzed by deriving the bow formula, which is a modification of Freund's equation, and the theoretical formula-derived results were compared with experimentally determined values. The bow of the GaN template was measured using a micrometer, and the residual stresses in the GaN and sapphire, carrier mobilities, and GaN crystal qualities were measured using a micro-Raman spectrophotometer. The results confirmed the annealing effect on the damaged sapphire layer, and the introduction of pre-strained GaN templates facilitated easier bow control compared to that afforded by a conventional GaN template. Additionally, we identified trends and optimal conditions for changes in residual stress, carrier mobility, and crystal quality in GaN and the damaged sapphire layer based on layer thickness and stress variations. We explain the mechanisms responsible for changes in bow, stress, carrier mobility, and crystal quality of the GaN template. [Display omitted] • A pre-strained sapphire was introduced to minimize the bow in the GaN template. • The bow of the pre-strained GaN template was counterbalanced by epitaxial GaN growth. • Relationships between composed layers were interpreted using the induced bow formula. • Residual stress, carrier mobility, and crystallinity trends in GaN were analyzed. • Mechanisms governing bow and optical properties were elucidated. [ABSTRACT FROM AUTHOR]

Surface integrity—comprising abrasive embedding, work hardening, and residual stress—is crucial for the performance of nickel-based superalloy components milled by abrasive waterjet (AWJ). Effective evaluation of this integrity is therefore essential. First, the effects of pure waterjet and small-size AWJ on the milled surface were analyzed, with abrasive embedding as a key indicator. It was found that small-size AWJ significantly reduced both the number and depth of abrasive particles embedded. Next, single-factor experiments determined the influence of AWJ process parameters on abrasive embedding, leading to the identification of optimal modification schemes (modification scheme 1 and modification scheme 2) for minimizing the number and depth of abrasives. Recommended processing parameters are waterjet pressure = 100 MPa, and step-over distance = 0.38 mm. Finally, it was observed that both modification schemes decreased surface hardness while significantly increasing residual compressive stress compared to the unmodified surface. These findings offer a theoretical and practical foundation for achieving high surface integrity in the milling of nickel-based superalloys using AWJ. [ABSTRACT FROM AUTHOR]

Electrochemical drilling (ECD) offers excellent potential for processing deep holes because it does not wear tools, does not create a remelting layer on the machined surface, and does not produce residual stress during machining. However, a normal single-hole tube electrode easily forms a spike at the bottom of the drilling hole, thereby destroying the flatness at the bottom. This phenomenon is clearly visible when drilling blind holes with large diameters. In this study, a tube electrode with multiple outlet holes is proposed to eliminate the spike and improve the flatness at the bottom of the hole. Specifically, a single outlet hole was discretized into multiple small-diameter outlet holes. The effects of the arrangement of the outlet holes on the electric field distribution over the workpiece surface and the flow field distribution in the machining gap were numerically investigated. The results generated according to the electric field showed that the outlet holes should be as small as possible and appropriately overlap to flatten the surface. The results generated according to the flow field indicated that increasing the number of outlet holes and their overlap ratio increased the electrolyte flow rate, but it also caused the flow fields to interfere with each other, resulting in an uneven distribution. Different tools were experimentally verified using stainless steel 20Cr13, and the stability of the process and machining quality were analyzed. The results showed that, for the given test parameters, higher machining quality and processing stability were obtained using a tool with 16 non-overlapping outlet holes. Furthermore, the discrete tube electrode was optimized using chamfered outlet holes. For a voltage of 25 V, feed speed of 0.8 mm/min, and electrolyte pressure of 0.2 MPa, a deep blind hole with a diameter of 22.43 ± 0.04 mm and depth of 71.28 mm was machined using the optimal tool, which had a roundness of 0.0201 mm, flatness of 52.46 µm, and taper of 0.1296°. [ABSTRACT FROM AUTHOR]

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]

B4C particle-reinforced Al matrix composite (B4Cp/Al) has excellent properties and is expected to become the mainstream of composites in the future. Due to the complex meso-structure of B4Cp/Al, this increases the difficulty of material precision machining. In addition, the current research on the PRMMCs generally focuses on SiCp/Al and the effects of machining parameters on cutting force and temperature, while the research on the effects of tool geometry parameters on material cutting is relatively rare. Therefore, the cutting mechanism of B4Cp/Al is studied by finite element simulation. Firstly, based on the meso-structure of B4Cp/Al, a three-dimensional (3D) model of the material is established. Then the mechanism of surface formation of B4Cp/Al was studied by combining cutting simulation and turning experiment. Use the simulation to study the effect of tool rake angle on material cutting surface quality. It was found that the removal mode of B4C particles, the residual stress in Al matrix after cutting, and the plastic deformation would be affected by the tool rake angle, thus affecting the cutting surface quality. After a comprehensive comparison, it is found that when the rake angle is − 5°, the cutting quality is the best. [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]

The mechanical performance of MoW‐HfN, a surrogate cermet for MoW‐UN Nuclear Thermal Propulsion (NTP) fuel, was characterized from room temperature to 1600°C. The modulus of elasticity and flexure strength were obtained from four‐point bend tests. Those tests revealed a loss of stiffness with increasing temperature and systematic increase in ultimate strength up to about 1400°C. This was followed by loss of ultimate strength and the onset of plastic deformation, attributed to the increased ductility of the MoW matrix above 1400°C. Chevron notch tests show that failure originates from features with a critical flaw size of ∼30 εm, which is comparable to the mean particle size of the ceramic phase. X‐ray diffraction (XRD) and Williamson–Hall (WH) analysis suggest that residual stress may contribute to the observed strength‐versus‐temperature behavior. [ABSTRACT FROM AUTHOR]

Highlights During the manufacturing of thermoset‐based carbon fiber‐reinforced polymer (CFRP) structures, a curing process involving thermal, chemical, and mechanical interactions occurs. This process gives rise to micro‐scale residual stresses due to differences in fiber and resin properties, leading to decreased mechanical properties compared to nominal values. A trans‐scale analysis method utilizing the reduced order model (ROM) is applied in this study to establish a connection between the manufacturing and in‐service processes for unidirectional CFRP (UD‐CFRP). By employing this method, the evolution of residual stresses at the micro‐scale during UD‐CFRP manufacturing is predicted, and the impact of these residual stresses on structural performance during service is assessed. Specifically, the manufacturing‐induced residual stresses reduce the material strength by a minimum of 19.31%, while also exploring the correlation between macro‐scale and micro‐scale failures. Notably, the computational cost of this method is significantly lower, with a reduction factor of 103 compared to the finite element method. Empirical evidence supports the effectiveness of this method in accurately predicting outcomes throughout both the manufacturing and in‐service processes. Trans‐scale analysis method links composites manufacturing simulation to in‐service performance. Highly efficient trans‐scale method excels in cost, accuracy, consistency, and convergence. Residual stresses from the curing process significantly impact matrix safety. [ABSTRACT FROM AUTHOR]

Man‐made ceramics generally undergo harsh manufacturing conditions (e.g., high‐temperature sintering). In contrast, mineral structures with superior mechanical strength are generated in organisms under mild biocompatible conditions. Herein, it is reported that ceramic objects can be directly produced and strengthened by drying purely inorganic gels (PIGs), mimicking the biological tactic of fabricating continuous monoliths from hydrated amorphous precursors. The overall process is easy and biocompatible in that solutions of common iron and molybdate salts are mixed to generate a PIG, consisting of 80 wt% liquid water and amorphous mineral nanoparticles (hydrated iron molybdate: FeMo2H7O11), which, upon drying under mild temperature, turns into a residual stress‐strengthened ceramic block that displays a high mechanical performance (with a hardness/elastic modulus of 1.7/17.5 GPa). Analogous to the well‐known Prince Rupert's drop reinforced by residual stress upon quenching, the uneven volume shrinkage from the outside inwards during dehydration builds up residual stress that enables amorphous mineral fusion (with the assistance of hydration water) and strengthening. Furthermore, a dramatic bandgap reduction is achieved in the dried objects due to local structural changes of the Fe atoms under residual stress. This PIG‐dehydration approach holds promise for green ceramic manufacturing and offers insights into biomineralization puzzles. [ABSTRACT FROM AUTHOR]

The current study investigates the effects of powder homogenization on the characteristics of polycrystalline diamond (PCD) sintered with molybdenum (Mo) at high pressure-high temperature (HPHT). PCD combines excellent properties, such as high hardness, wear resistance, and good thermal conductivity. Furthermore, it has greater fracture toughness when compared to a single-crystal diamond, which makes it suitable as a cutting tool. The properties of PCD, however, are sensitive to the preparation conditions, which include the particle size of the initial powders, contaminants, and dispersion of the binder phase. Bearing this in mind, in order to study the effects of the preparation conditions on the properties of PCD, the blends were homogenized by a manual method, such as High-Energy Ball Mills (HEBM), at different times: 30s, 60s, and 90s. Data regarding micromorphology, phase transformations, resulting residual stresses, and thermostability were determined. According to the results, the blends prepared by HEBM showed superior phase dispersion, greater effectiveness in the formation of molybdenum carbides, and good densification. The thermoanalytical data showed that composites with superior thermal performance to commercial PCD were obtained, with thermostability between 802 °C and 837 °C. [ABSTRACT FROM AUTHOR]

A self-built automatic platform was built to evaluate the thermal shock performances of Cansas-III SiC fibers at 1200 °C in air up to 500 cycles, the corresponding oxidation and damage mechanisms were then revealed. The results showed that oxide scale was formed during thermal shock with a thickness of about 1 μm, the core was not oxidized via its protection. The fiber roughness increased before 100 cycles due to the decomposition of the amorphous SiC x O y phase, and then decreased as the formation of oxide scale. Within Cansas-III SiC fibers, structural defects of free carbon increased as the increasing I D /I G values, in addition, the TO peak shifted to the left, which both demonstrated that the relative movements occurred among SiC grains and residual stresses were then emerged. To clarify the axis and radial cracking of the oxide scale, a modified formulation considering nonzero shear strain components was then proposed to calculate the related residual stresses. The peeling and cracking of the oxide scale was ascribed to the residual stresses of GPa level among SiC grains and the thermal expansion mismatch between the oxide scale and the core. [ABSTRACT FROM AUTHOR]

We study the response of a class of transversely elastic bodies, wherein the Green–Saint Venant strain tensor is a function of the second Piola–Kirchhoff stress tensor, when the body is residually stressed. The notion of such non-Cauchy elastic bodies being transversely isotropic is defined in Rajagopal (Mech. Res. Commun. 64, 2015, 38–41), and by a body being residually stressed, we mean the interior of the body is not in a stress-free state although the boundary is free of traction as considered by Coleman and Noll (Arch. Ration. Mech. Anal. 15, 1964, 87–111) and by Hoger (Arch. Ration. Mech. Anal. 88, 1985, 271–289). [ABSTRACT FROM AUTHOR]

The surface geometry of polycrystalline diamond compact (PDC) cutters has a considerable influence on their rock-cutting mechanism. In the study reported here, to study the mechanism for rock crushing by saddle PDC cutters, two-dimensional and three-dimensional finite-element models of such cutters cutting granite were established. The two-dimensional simulation results were used to analyze the crack generation and expansion forms when a saddle PDC cutter cuts rock, and the results show that it mainly crushes the rock via joint tensile and shear action. Next, the wear resistance and cutting performance of saddle PDC cutters were analyzed by simulation and experiment, and both were better than those of conventional PDC cutters. The residual stresses on the surface of a notch cut by a saddle PDC cutter were extracted from the 3D model, and it is concluded that they are mainly compressive stresses. Cutting models for mixed arrangements of saddle and conventional PDC cutters were established, and analyses were conducted of how the cutting-depth difference between the front and rear cutters in the same-track cutting scheme and the spacing of the front cutters in the different-track cutting scheme affect the cutting force of the rear cutters, the mechanical specific energy, and the cutting stability. The results show that for the same-track cutting scheme, the optimum cutting depth difference between the front and rear cutters is 0.1–0.2 mm, and for the different-track cutting scheme, the optimum spacing between the front cutters is 17 mm. Finally, the characteristics of the cutting damage areas of different types of PDC cutters are discussed. The present results help in revealing the rock-breaking mechanism of saddle PDC cutters and provide theoretical support for designing hybrid PDC bits. Highlights: The generation and propagation modes of rock cracks during the cutting of rock by saddle PDC cutters are revealed and compared with those of conventional PDC cutters. By extracting and comparing the residual stresses on their cut surfaces, the impacts of saddle and conventional PDC cutters on the surrounding rock are analyzed. The wear resistance, cutting stability, and other factors of saddle and conventional PDC cutters are investigated, and the results show that saddle PDC cutters have superior performance. The optimal parameters for a mixed cutter arrangement of saddle and conventional PDC cutters are determined via simulation, and the geometric influence coefficient n is defined. [ABSTRACT FROM AUTHOR]

Shakedown analysis with Melan's theorem is an important approach to predicting the ultimate load-bearing capacity of heterogeneous materials under varying loads. However, this approach entails dealing with a large-scale nonlinear mathematical programming problem with numerous element-wise yielding constraints and unknown time-independent beneficial residual stress variables, resulting in a substantial computational burden. The well-known basis reduction method expresses the unknown time-independent beneficial residual stress as a linear combination of a set of self-equilibrium stress (SES) bases, and the corresponding coefficients are the unknowns. This method is effective only if the set of SES basis vectors is small and easily available. Based on the representative volume element (RVE) and FEM-cluster based analysis (FCA) method, this paper proposes a FEM cluster-based basis reduction method to fast predict the shakedown domain of heterogeneous materials. The novel data-driven clustering method is introduced to divide the RVE into several clusters. The SES basis is constructed by applying the cluster eigenstrain to RVE under periodic boundary conditions. Numerical experiments show that the unknown time-independent beneficial residual stress can be well represented with this small set of SES basis vectors. In this way, the unknown variables are reduced dramatically. In addition, to further reduce the number of nonlinear constraints, a constraint reduction strategy based on the reduced-order model of FCA is implemented to remove the element-wise yielding constraints for the elements far from yielding. Several numerical examples demonstrate its efficiency and accuracy. [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]

Background: A recent revision to the ASTM E837 standard for near-surface residual stress measurement by the hole-drilling method describes a new thickness-dependent stress calculation procedure applicable to "thin" and "intermediate" workpieces for which strain versus depth response depends on workpiece thickness. This new calculation procedure differs from that of the prior standard, which applies only to thick workpieces with strain versus depth response independent of thickness. Objective: Herein we assess the new calculation procedures by performing hole-drilling residual stress measurements in samples with a range of thickness. Methods: Near-surface residual stress is measured in a thick aluminum plate containing near-surface residual stress from a uniform shot peening treatment, and in samples of different thickness removed from the plate at the peened surface. A finite element (FE) model is used to assess consistency between measured residual stress across the range of sample thickness. Results: Measured residual stress varies with sample thickness, with thinner samples exhibiting smaller near-surface compressive stress and a larger gradient of subsurface stress. These trends are consistent with both observed bending (curvature) of the removed samples and the trend in FE-calculated expected residual stress. The measured and expected residual stresses are in good agreement for samples of intermediate thickness, but the agreement decreases with sample thickness. Measured residual stress is invariant with gage circle diameter. Conclusion: The new thickness-dependent stress calculation procedure for hole-drilling provides meaningful improvement compared to thick-workpiece calculations. [ABSTRACT FROM AUTHOR]

Dimensional tolerances for high-speed-machined aluminum products continue to tighten due to the demand for automated assembly of complex monolithic parts in aerospace and other industries. Understanding the contribution of inherent residual stress in wrought Al 7050-T7451 plate, common in aircraft manufacture, to distortion of high-aspect-ratio machined parts is critical but remains problematic due to the alloy's low residual stress magnitude over large geometries. Prior investigations into residual stress effects on machined part distortion suffer inadequate characterizations of the wrought material stress field, either because of low fidelity due to "slitting" methods, confounding effects in machined-layer removal methods, or small sample size when using neutron diffraction (ND). In this work, inherent residual stress is measured via ND at 860 locations in a 90.5 mm thick Al 7050-T7451 plate having dimensions 399 mm in the rolling direction and 335 mm in the transverse direction. Unlike prior studies, the ND residual stress is reconstructed using an iterative algorithm to ensure fully compatible, equilibrated 3D field prior to examining its effect on distortion. The findings from simulations and experiments show that inherent residual stress alone could distort a high-aspect-ratio part beyond aerospace industry requirements, that slitting measurements may not sufficiently characterize residual stress for predicted distortion, and that parts machined from different plate thickness locations could exhibit reversed distortion patterns. Thus, research into distortion prediction that considers machining should carefully characterize and reconstruct inherent residual stress so that the coupled machining effects are accurately modeled. [ABSTRACT FROM AUTHOR]

Gears represent a fundamental component of automotive transmissions, the performance of which is directly influenced by flank surface integrity. With the exception of grinding, gear production does not require the use of lubricants. The elimination of oils in the final finishing phase represents an important opportunity to greatly improve process sustainability and reduce production costs. However, dry grinding presents several challenges, including dimensional tolerances and roughness requirements, microstructural defects due to excessive heat generation, and maintaining the overall surface integrity of flanks such that wear resistance is not compromised. The present work investigates the geometric accuracy, microstructure, and wear resistance of FIAT 500 4/6 speed gears manufactured by FCA/Stellantis, comparing conventional wet grinding with two alternative processes including superfinishing and dry grinding. The material and manufacturing processes employed prior to grinding were the same in all cases, with grinding then performed by the same manufacturer. The dimensional accuracy, roughness, microstructure, residual stress state, and wear resistance of gear flanks were then analyzed to compare the overall performance of each grinding process. The obtained results show that dry grinding can produce gears with acceptable geometric accuracy, no microstructure defects and greater wear resistance than gears finished with conventional wet grinding or superfinishing. As a result, the complete elimination of lubricant in gear production is possible, leading to a more sustainable process without compromising gear performance. [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]

This paper focuses on the difficulties in high-quality and high-efficiency micro-milling nickel-based superalloy micro thin-walled parts. The second-generation Non-dominated Sorting Genetic Algorithm (NSGA-II) is improved. A central composite experiment is designed, and a surface roughness prediction model is developed for micro-milling thin-walled parts. A prediction model for surface residual stress on thin-walled parts is developed using an L9(34) orthogonal simulation experiment. Using the NSGA-II algorithm, the four cutting parameters (spindle speed, feed per tooth, axial cutting depth, and radial cutting depth) are optimized to achieve low surface roughness and high material removal rate, while stable cutting and surface compressive residual stress are considered constraints. Finally, the high-quality and high-efficiency micro-milling of the Inconel 718 cross-shaped thin-walled parts is realized. [ABSTRACT FROM AUTHOR]

The notch effect significantly influences the fatigue response of components and is particularly relevant for parts produced with additive manufacturing (AM) processes, characterized by complex geometries and possible geometric discontinuities inducing local and critical peak stresses. Moreover, the low surface quality, as well as manufacturing defects and residual stresses, interacts with the local peak stress induced by geometric discontinuities, complicating the assessment of the notch effect for AM parts and requiring extensive experimental fatigue investigations. In the present paper, the notch sensitivity of as‐built AlSi10Mg specimens produced with the laser beam powder bed fusion in the Very High Cycle Fatigue regime is investigated. Ultrasonic fatigue tests up to 109 cycles have been carried out on rectangular bars and rectangular bars with a central through‐thickness hole. The notch effect has been found to significantly affect the fatigue response of the investigated AlSi10Mg specimens, with surface defects having a main role and pointing out the influence of the surface quality on the crack formation. Highlights: Notch sensitivity on the very high cycle fatigue (VHCF) response of AlSi10Mg specimens is investigated.The AlSi10Mg VHCF fatigue response is strongly influenced by the notch.The experimental fatigue notch factor is close to that computed with literature models.Experimental tests are recommended to account for the large experimental scatter. [ABSTRACT FROM AUTHOR]

In this study, multifunction cavitation (MFC) was performed on low‐alloy steel (AISI 4140 steel) rods with different hardnesses to increase their fatigue limit. It was found that a high compressive residual stress was generated on the surface of steel rods by MFC and that the magnitude of the compressive residual stress tended to increase with increasing specimen hardness, which resulted in a higher fatigue limit. However, fatigue cracks are known to be initiated from the pits and red rust that form on the surface during MFC treatment in water. Furthermore, relaxation of the compressive residual stress was also investigated during the fatigue test to elucidate the mechanism for improving the fatigue properties. The results showed that the fatigue limit for MFC‐treated steel rods was accurately estimated by considering residual stress relaxation, hardness, and pit formation. Validation of the fatigue limit estimation was also conducted through comparison with Murakami's equation. Highlights: MFC generated compressive residual stress on the surface of steel rods.MFC increased the fatigue limit for steel rods.The fatigue limit of MFC‐treated steel rods with different hardnesses was estimated.Fatigue cracks were initiated at surface pits formed by MFC. [ABSTRACT FROM AUTHOR]

Residual stress of a welding joint based on finite element simulation was predicted to gain popularity in the process equipment industry. As for the nuclear power industry, the weldment located in a primary coolant system should be evaluated to verify the boundary integrity. The weld residual stress is an important load for leaks before break or fatigue crack growth estimation. Heat input is a key factor to accurately simulate the weld's residual stress. Hence, heat transfer activities of weld beads, based on the theoretical volume heat generation rate of the weld element, were simulated using finite element analysis. The traditional method of controlling heat input in finite element method simulation of the welding process is achieved by setting the temperature monitoring point. When the melting temperature is reached, the calculation for weld bead melting is terminated. However, it does not comply with the real welding process because too many assumptions are involved. Therefore, a novel heat input function to modify the temperature differences of weld beads and weld layers was proposed to predict the temperature and residual stress field. Four simulations based on the modified heat input methods and traditional approaches were performed to predict the weld residual stress field of a butt-welded joint for thick-walled pipe and were compared with experimental data. Results show that more accurate thermal fields and weld residual stress fields were achieved using the proposed heat input approach. [ABSTRACT FROM AUTHOR]

The investigation carried out in the current study illustrates the dissimilar gas tungsten arc welding (GTAW) between Inconel 718 (IN 718) and austenitic stainless steel (ASS 304L) utilizing three different filler materials. This study utilizes Ni-based fillers (ERNiCrCoMo-1 (IN 617) and ERNiFeCr-2 (IN 718)), and austenitic filler ASS 304L and characterizes the relationship among microstructural and mechanical characteristics using identical weld parameters. The obtained dissimilar weld joint using Ni-based filler materials depicts no weld solidification cracking, whereas austenitic filler causes the weld solidification cracks. The microstructural characterizations were examined using optical and FESEM revealing the occurrence of columnar, cellular, and equiaxed dendritic structures in all three weld metals. FESEM/EDS analysis illustrates the occurrence of Mo and Cr-rich phases (M23C6 and Mo6C) in ERNiCrCoMo-1 weld metal, NbC, Mo/Ti–rich, and laves phases in ERNiFeCr- 2 weld metal and Cr- rich carbides in ASS 304L weld metals. EBSD assessment shows the improved texture of the weld metals through IPF and PF maps. The Vickers microhardness demonstrates the highest hardness value (271 HV5) for the ERNiFeCr- 2 weld metal due to the existence of the brittle intermetallic phases, and minimum in the case of ASS 304L weld metals (156 HV5). The ambient temperature tensile test exhibits the maximum (649 MPa) and minimum (404 MPa) UTS corresponding to ERNiCrCoMo-1 and ASS 304L weld metals respectively. The tensile specimens for all the weld metals experience fracture from the weld metals. The Charpy toughness values of the weld metals show lower values (ERNiCrCoMo-1 (70 J), ERNiFeCr-2 (56 J) and ASS 304L (32 J)) than the BMs (IN 718 (135 J) and ASS 304L (228 J). Residual stress analysis was conducted employing the deep hole drilling (DHD) technique, indicating that the highest residual stress occurs 2 mm below the top weld face, classified as tensile stress for all three used filler materials. [ABSTRACT FROM AUTHOR]

Double‐layer thermal barrier coatings are one of the development directions of thermal barrier coatings technology. LaYbZr2O7 (LYZO) has high toughness and low thermal conductivity, making it promising for use as a high‐temperature thermal barrier coating. However, its relatively poor mechanical properties, especially low fracture toughness, limit its further application. Therefore, we prepared a double‐layer coating of LYZO and Y2O3 partially stabilized ZrO2 (YSZ) using atmospheric plasma spraying, with the inner layer being YSZ and the outer layer being LYZO. The results showed that after spraying, LYZO was in the metastable fluorite phase, while YSZ was in the tetragonal phase. LYZO and YSZ had good chemical compatibility, and an interaction layer formed at the interface between them, with its thickness increasing with the sintering time. Eventually, after 100 h of heat treatment, the thickness reached 12 µm. The hardness of the LYZO/YSZ interface increased with the sintering time, reaching a maximum value after sintering at 1300°C for 10 h. When evaluating the interfacial bonding strength using indentation method, the length of cracks caused by indentation significantly decreased with the increase of sintering time. The increase in bonding strength can be attributed to the formation of a reaction layer and the reduction of thermal residual stresses. Raman spectroscopy was used to measure the thermal residual strain at the LYZO/YSZ interface. Unbalanced distribution of thermal residual stress and M phase was observed near the interface. As the sintering time increased, both thermal residual stress and M phase content decreased. In summary, the double‐layer thermal barrier coating of LYZO/YSZ has good potential for development. [ABSTRACT FROM AUTHOR]

The key to understanding the shear failure mechanism of prestressed concrete girders lies in how to properly deal with the combined effects of the applied load, the support reaction, as well as the prestressing force. This paper firstly conceptualizes a combined stress field model, which integrates these effects by manifesting several subfields to disclose the potential failure patterns at different locations in the short shear span. Then, shear tests of four full-scale pretensioned concrete T-girders with a height of 1.6 m and two kinds of shear-span-to-depth ratios were carried out. The test results showed that all the specimens failed in a web-crushing pattern near the support accompanied by a bond-slip of the deflected strands. By analyzing the deviated compression subfields in the highly stressed webs and introducing a failure criterion for cracked concrete, the ultimate shear strength of pretensioned concrete girders was formulated. Finally, the shear strength evaluated by the proposed formula and by some other design codes were compared, and it was proved that the results of the proposed model were closer to the test. [ABSTRACT FROM AUTHOR]

• Flexoelectricity and surface effect on piezoelectric nanolaminates were reported. • Analytical solution of bending deformation and vibration were obtained. • Effects of residual surface stress and the flexoelectric coefficient were examined. • Effects of aspect ratio and plate thickness on bending behavior were examined. In this paper, a model of double-layer rectangular piezoelectric nanolaminates with different upper and lower surface properties is established. The bending and vibration behavior of the piezoelectric nanolaminates are evaluated and analyzed, taking into consideration the flexoelectric and surface effects. Utilizing the surface piezoelectric model, flexoelectric theory, and Kirchhoff plate theory, this study provides analytical solutions for the bending deflection and natural frequency of rectangular piezoelectric nanolamination materials under various boundary conditions. The results indicate that the effects of flexoelectric and surface influences on piezoelectric nanolaminates are associated with residual surface stress and flexoelectric coefficients. These effects can enhance the bending stiffness and decrease the natural frequency of the piezoelectric nanolaminates. Furthermore, altering the residual stress on the upper and lower surfaces of the laminates separately will result in different trends in bending deflection, while causing a consistent trend in natural frequency change. When the electric potential direction of piezoelectric nanolaminates is different, the bending deflection of piezoelectric nanolaminates will change accordingly. The natural frequency of piezoelectric nanolaminates is determined by the absolute value of the flexoelectric coefficients, and is independent of their positive or negative values. Both the surface effect and the flexoelectric effect are influenced by size-dependent behaviors. When the thickness of the laminates is sufficiently large, both the surface effect and flexoelectric effect can be disregarded. This paper's research methods and results provide theoretical models and analytical methods for the microstructure design, multi-physical field characterization, and bending deformation behavior of intelligent components containing rectangular piezoelectric nanolaminates. [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]

The welding process adopted for nuclear vessels is important from temperature and residual stress. In, this study stainless steels material was used to simulate the weldability with respect to reaching the melting at the Fusion zone with respect to the weld input power and process time. Static thermoelastic process simulation was done using 3D-Finite Element Analysis using ANSYS. For a representative 3 mm plate butt welding process, isotherms in the transverse weld bead area were used to identify melting and solid to solid phase change points in Fusion and HAZ. The distributions evaluated at Fusion, HAZ and in base material along the longitudinal direction, transverse and along the thickness. The residual stress evaluated along the transverse direction is compared with yield strength to evaluate weldability. Also, the transverse analysis leads to an understanding of structural stability. A single-pass weld process limit was obtained for a feasible time and power source and the thermoelastic distributions studied. [ABSTRACT FROM AUTHOR]

The article presents a study on the effects of ultrasonic treatment on residual welding stresses (RWS). Ultrasonic treatment was administered from three orientations: external, internal, and bilateral. Six samples, each with a thickness of 8 mm and composed of steel grade 09G2S, were prepared. The welding of these samples was executed using semi-automatic equipment and adhered to regulatory and technical guidelines. The magneto anisotropic technique, foundational to the operation of the Stress Vision Lab device, was employed to measure residual stresses. Given that this device quantifies residual stress values in arbitrary units, a calibration table was devised to translate these measurements into megapascals (MPA). This calibration was established by correlating values obtained from the ZW-100 testing machine with those measured by the Stress Vision Lab, necessitating the preparation of three additional samples of the same steel grade. Experimental investigations revealed that ultrasonic treatment applied internally to the samples facilitated the most significant reduction in residual (tensile) stresses, with reductions of 37.5% from external application and 27% from internal application. Leveraging the data acquired, a device has been developed to mitigate residual welding stresses within the inner wall of the near-seam zone of pipelines. [ABSTRACT FROM AUTHOR]

Highlights This study investigates the effect of the annealing treatment for carbon fiber reinforced Polyether‐ketone‐ketone (CF/PEKK) composite structures under flexural and compressive loadings through reference, pre‐damaged, and annealed sample sets. Significant recovery of pre‐existing damage is observed after the annealing process, following both flexural and compressive loading. Acoustic emission (AE) inspection is employed to monitor the failure behavior and assess the impact of pre‐damage and annealing on CF/PEKK composite. Initially, AE inspection reveals that the reference CF/PEKK material exhibits a notable fiber‐related failure with 85% of cumulative AE counts under flexural load, whereas matrix‐related failures are more pronounced with 92% cumulative AE counts under compressive load. Pre‐damages in the matrix alter the cumulative count percentages and initiation time that are related to matrix, interface, and fiber‐related failures, under flexural and compressive loadings. After annealing, each cumulative AE count percentages are comparable to reference sample values, due to changes in microstructure and relieving of residual stresses. The annealing effect is further validated through dynamic scanning calorimetry (DSC) analysis results with increased glass transition temperature (Tg) and degree of crystallization (Xc). Overall, these findings indicate that annealing treatment effectively restores structural integrity and improves the mechanical performance of CF/PEKK composites. Annealing aims for damage recovery in CF/PEKK under flexural and compressive loads. Significant damage recovery in CF/PEKK is seen after annealing. Annealing raises Tg and crystallinity, and enhances CF/PEKK structural integrity. [ABSTRACT FROM AUTHOR]

Residual stresses existing on the surface of a structural component can be accurately and non-destructively assessed using the instrumented indentation technique, which is crucial for the safety assessment of in-situ structures. In this study, a novel instrumented spherical indentation model based on the equivalent material assumption and the principle of energy density equivalence is proposed for determining the equi-biaxial residual stresses of isotropic power-law hardening metallic materials. The model establishes the correlations between equi-biaxial residual stresses, total work of indentation, and constitutive parameters. Finite element analysis is utilised to determine the model constants by calculating the total work of indentation. Furthermore, the equi-biaxial residual stresses predicted by the model are close to the reference equi-biaxial residual stresses provided by finite element simulations under various equi-biaxial residual stress states for multiple power-law hardening materials. Subsequently, the instrumented spherical indentation experiments are conducted on specimens without equi-biaxial residual stress and on bending cross-shaped specimens with multilayer equi-biaxial residual stresses for six types of metallic materials. The equi-biaxial residual stresses applied by the tests agree well with those predicted by the novel indentation model. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper assesses the impact of utilizing statistically defined residual stress fields from cold expansion (Cx) in linear elastic, multi‐point fracture mechanics analyses using the spatial analysis of residual stress (SpARS) methodology. There is significant value and interest in leveraging the increased fatigue life afforded by Cx, but it is imperative to quantify the variability of the residual stress to understand the expected variability in benefit due to Cx. Comparisons of the predicted fatigue lives from SpARS‐produced statistical residual stress fields are made to fatigue test data. Results demonstrated that the less compressive 95% upper bound from the mean residual stress would be a reasonable strategy as it supplies a compromise between safety and inherent material and process variability while still producing a sizable improvement in predicted fatigue life. In this study, using SpARS to incorporate statistically representative residual stress fields in fatigue crack growth analyses demonstrates a methodology to aircraft structural engineers for improved fleet management and allow increased aircraft availability through fewer inspections. [ABSTRACT FROM AUTHOR]

The effect of plastic deformation on the hydrogen embrittlement behavior of high-strength martensitic steels was investigated using a U-bend test. The hydrogen embrittlement susceptibility appeared to be enhanced with increasing plastic strain. Based on fractographic and stress-strain analyses, the maximum principal stress dominated the hydrogen embrittlement fracture. Although an apparent enhancement with increasing plastic deformation was observed, the origin of this enhancement was increased residual stress arising from the evolution of graded plastic strain during U-bending. We conclude that residual stress, rather than plastic strain induced by plastic deformation strongly affects hydrogen embrittlement susceptibility in deformed high-strength steel components. • Hydrogen embrittlement susceptibility of U-bend specimens was independent of plastic strain. • Maximum principal stress was the primary criterion for the hydrogen embrittlement susceptibility. • The apparent decrease in hydrogen embrittlement resistance with reduced bending radii was due to increased residual stress. [ABSTRACT FROM AUTHOR]

Remarkable casting properties and superior mechanical characteristics of cast iron make it an ideal material for a wide range of industrial applications. However, the production of cast iron components may result in the formation of cracks and defects, posing a significant threat to their structural integrity. Repair welding is a promising solution to resolve cast iron production defects. However, repair welding cast iron components poses unique challenges that stem from residual stress (RS) formation and the possibility of cracking during the repair process. Moreover, research on cast iron repair is scarce. To overcome these challenges, this paper presents a thermo-mechanical model validated by experiments to reduce RS in cast iron repair welding through the optimization of welding parameters and weld sequences as well as the geometry of the repair area. An experimental bead-on-plate weld is set up in order to validate the developed thermo-mechanical model. The temperature distribution in the weld is measured using thermocouples placed around the weld line. An X-ray diffraction technique is used to measure the axial and transverse RS at different points around the weld line. The developed finite element model is employed to simulate the repair welding process and analyze the effect of inter-pass temperature, the number of welding passes, welding sequences, and groove geometry on the RS. The numerical approach applied in this study provides a framework for repair welding optimization of cast iron and other materials, fostering the development of more efficient and reliable repair methods for industrial applications. [ABSTRACT FROM AUTHOR]

Nickel alloys are widely used in aerospace and defense industries due to their excellent high-temperature characteristics. In order to increase fatigue resistance and oxidation corrosion resistance, aerospace curved surface parts always need to be strengthened using laser shock peening technology on five-axis machines. However, it is easy to generate dense laser spots in certain regions during the process, which might lead to an uneven distribution of residual stress on surfaces of the component. To address this issue, the study investigates the problem of excessive spot overlap rate at large curvature positions caused by a mismatch between the surface curvature of curved components and the dynamic performance of equipment, then proposes an optimization algorithm for motion control based on linear interpolation principles. By analyzing the relationship between the feed rate of the program segment and the actual feed rate, the speed of each axis of the machine tool is confirmed and adjusted, and the control flow of the optimization algorithm is established. The feasibility of the algorithm is preliminarily verified by comparing the changing trend of feed rate before and after optimization through simulation. In actual laser shock peening experiments on nickel alloy spherical shell elements, the laser spot distribution on the surface of the component is uniform, and the relative error range between the actual overlap ratio and the theoretical value can be controlled within 5%, demonstrating the correctness of the optimization algorithm. This study can significantly improve the surface machining quality of curved components and have practical applications. [ABSTRACT FROM AUTHOR]

Efficient lubrication and cooling are crucial in machining operations to enhance tool life and workpiece quality. Sustainable methods like minimum quantity lubrication (MQL) and dry cutting often face limitations in cooling efficiency and chip evacuation, especially under high-speed conditions or when machining difficult-to-cut materials such as stainless steel. This study introduces the novel pressurized injection lubrication (PIL) technique designed to address these challenges by optimizing lubrication, cooling, and chip evacuation during the turning operations of stainless steel 304. Using flaxseed oil as the lubricant, the PIL system employs a 0.26 mm stream diameter at a pressure of 16 bar to provide the necessary cooling and lubrication to the cutting zone. Cutting temperature and surface roughness were selected as the primary responses. Experimental runs were designed using the Taguchi L9 method. Analysis of variance showed that the lubrication method significantly affected the cutting temperature, with a contribution percentage approaching 94%. The experimental results demonstrated that PIL reduced the cutting temperature by up to 55%, while MQL reduced it by about 48%, both compared to dry cutting at the highest utilized speed. The lubrication method was also found to be the most significant factor affecting surface roughness, with a contribution percentage of 72.8%. Experimentally, PIL improved surface roughness by a maximum of 16.2% compared to MQL. Additionally, PIL maintained low oil consumption (0.9 l/h) and energy usage (< 0.017 kWh). The cost-effective PIL setup, priced under 65 USD, underscores its potential as a sustainable and efficient alternative for machining processes. The system's components are readily available, facilitating easy integration into existing metal-cutting machines. Finite element analysis (FEA) modeling was used to predict residual stresses under different lubrication methods. The FEA model indicated that PIL and MQL reduced residual stresses by about 81.2% and 76.6%, respectively, compared to dry cutting at a speed of 500 rpm. These findings suggest that PIL can significantly enhance machining performance and sustainability, offering a viable solution to modern manufacturing challenges. [ABSTRACT FROM AUTHOR]

The surface residual stress of the parts has an important influence on their performance. The generation mechanism of surface residual stress in ultrasonic vibration-assisted grinding (UVAG) of bearing steel was investigated, and the correlation between processing parameters and residual stresses was obtained. Based on the ultrasonic vibration-assisted grinding force and thermal model and the flow stress model considering the initial material microstructure, the mechanical and thermal stresses of the material were calculated. Finally, the theoretical model of residual stress is established based on the yield theory and experimentally verified. High-speed ultrasonic aerostatic spindle for ultrasonic vibration-assisted grinding, change the inlet pressure to realize the ultrasonic amplitude and frequency adjustment, the experimental results show that the cutting direction and the vertical cutting direction of the residual stress test results and the model prediction results of the average relative error of 11.4% and 11.7%, and the rule of change is more consistent. Based on the experimental results, the influence pattern of process parameters on the experimental results was analyzed. The results show that the residual compressive stress on the surface of ultrasonic vibration-assisted grinding is directly proportional to the grinding depth, feed rate, and inlet pressure of pneumatic ultrasonic wave and inversely proportional to the linear speed of the grinding wheel. This study provides a theoretical basis for the analysis of UVAG residual stress and optimization of UVAG process parameters. [ABSTRACT FROM AUTHOR]

Currently, there is a significant need for affordable coatings that are both authentic and ecofriendly, with the goal of reducing pollution. In order to mitigate frictional loss, researchers have produced hybrid coating based on carbon through the utilization of the high‐velocity oxygen fuel (HVOF) spray technique. The results showed that the coefficients of friction (COFs) varied in the range of 0.1–0.5, and the wear rates ranged from 40 to 115 μm. The experiments were performed under different situations, encompassing temperatures ranging from 50°C to 200°C, loads ranging from 40 to 55 N, and sliding speeds ranging from 0.3 to 1.2 m/s. The corrosion tests showed a decrease in mass loss from 0.15 to 0.02 g after 1 h of immersion and from 0.20 to 0.04 g after 5 h of immersion. The tribological testing revealed significant improvements in various properties. The microhardness increased by 78.7%, residual stress decreased by 78%, mass loss due to corrosion decreased by 60% after 1 h and 62.5% after 5 h, coefficient of friction decreased by 76.9%, and wear rate reduced by 62.5%. [ABSTRACT FROM AUTHOR]

In this investigation, Taguchi's grey relational analysis (GRA) is utilized to optimize parameters in an orthotropic steel deck section subjected to thermo‐mechanical tensioning. In this study, it is aimed to determine optimal values for deck thickness, welding sequence, and welding speed, which are evaluated through finite‐element analysis based on outputs such as longitudinal stress, transverse stress, and deflection. In this study, a previously validated numerical simulation model is extended by conducting a parametric analysis to investigate the influence of varying parameters on the model's behavior. An analysis of variance is conducted to identify the most significant variable affecting the input parameters. Additionally, a confirmatory test is also performed to validate the characteristics of the Grey Relational Grade. In the results, it is indicated that faster welding speeds result in increased deflection of the deck plate. Furthermore, the transition from compressive to tensile longitudinal stress is more abrupt in thinner decks (9–10 mm) compared to thicker decks (11–12 mm). This redistribution of residual stresses is attributed to the increasing thickness of the deck plate. Optimal input levels (A2–B1–C1: 10 mm deck thickness, welding sequence case 1, and 0.005 m s−1 welding speed) are determined using GRA. Welding speed contributes the maximum to the optimization results among the evaluated variables. [ABSTRACT FROM AUTHOR]

Mechanical behavior of B 4 C - HfB 2 particulate ceramic composite doped with CrB + Cr 3 B 4 chromium boride compounds were studied by nanoindentation. Hardness, Young's modulus, and indentation stress - indentation strain behavior of B 4 C and HfB 2 phases was computed. It was found that hardness and Young's modulus of B 4 C matrix phase in B 4 C - HfB 2 doped with Cr - B was increased as compared to those hardness and Young's modulus of pure B 4 C. It was also found that indentation stress was relieved by "pop-in" events in some of the B 4 C grains, however, the "pop-in" discontinuous events were always observed upon indentation of HfB 2 grains, that lead to a decrease in hardness of HfB 2 from 40 to 50 GPa before "pop-ins" to 28–32 GPa after "pop-ins". The obtained results can be further used in calculations of thermal residual stresses in B 4 C and HfB 2 phases of B 4 C - HfB 2 particulate ceramic composite. [ABSTRACT FROM AUTHOR]

The high residual stress and low toughness of ceramic matrix composite/metallic brazed joints poses severe challenges for the stable operation of high-speed aircraft under harsh conditions. This article innovatively tackles this issue with electrophoretic deposition (EPD), creating a CNT covered Cu foam composite interlayer for brazing C f /SiC and Nb with an Ag–Cu–Ti alloy filler. A layer of mass ratio-controllable and percolated CNTs was physically adsorbed on the surface of the Cu foam substrate. EPD time was systematically investigated for its impact on the microstructure and mechanical properties of the joints. Results indicate that during brazing, the CNTs reacted with the active Ti element, transforming into ultrafine TiC grains with particle sizes ranging from 6 to 16 nm. These were dispersed evenly in the Ag solid solution. The elastic recovery rate of the cluster regions showed an increase of 123 % compared to the Ag solid solution, showing improved toughness of the seam. When the EPD time was 80 min, the shear strength of the joint produced with the composite interlayer reached 128.6 MPa, a 69 % increase over the directly brazed joint. Moreover, the fracture location of the joint shifted from the brazed seam towards the interior of the bulk C f /SiC. Additionally, finite element analysis was utilized to confirm a significant decrease in residual stresses within the joint, and verified the findings. [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]