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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]

Residual stresses and surface roughness have been recognized to play a critical role in the fatigue strength of metal components. Machining processes can induce different roughness and residual stress conditions depending on the parameters used in the process. Therefore, it is essential to develop knowledge that helps to predict the residual stresses and roughness that would be obtained from different machining conditions. Due to the growing interest from the industry in the use of 42CrMo4 steel because of its excellent mechanical properties, the main objective of this work is to establish two phenomenological models to accurately predict the residual stress and roughness values in turned specimens of this material. The models are derived from data of four process variables: (a) insert tip radius; (b) feed rate; (c) cutting speed; and (d) depth of cut. For this purpose, a wide experimental campaign has been developed, which includes the machining of 68 specimens under various cutting scenarios, and their subsequent measurement of residual stresses and roughness. Once the experimental data were obtained, the response surface method based on the central composite design was used to fit the models, obtaining a correlation index R 2 higher than 0.9 in both cases. In this article, it is concluded that feed rate and insert radius have a greater effect on the residual stress and roughness obtained, while cutting speed and depth of cut have a lesser impact on the results. It is hoped that the findings will establish a groundwork for the machining of this material type, ensuring controlled conditions of residual stress and roughness. [ABSTRACT FROM AUTHOR]

In this study, robust silicon carbide (SiC)-niobium (Nb) joints were obtained using a composite filler consisting of a novel type of negative thermal expansion (Sr 0.2 Ba 0.8)TiO 3 particle–reinforced Cu composites (SBT-Cu) and an AgCuTi active filler. A systematic investigation was conducted to analyze the brazing temperatures and SBT-Cu thickness affect the microstructure and mechanical properties of brazed joints. The results indicated that the shear strength of SiC–Nb joints brazed with AgCuTi +80 μm SBT-Cu composite filler increased to 64 MPa at 900 °C for 15 min, which was an improvement of 146 % over the strength of joints brazed without SBT-Cu. The addition of the SBT-Cu interlayer relieved the coefficient of thermal expansion mismatch among SiC, AgCuTi and Nb. Meanwhile, the calculation results verified that the residual stresses in the joints were substantially reduced and that the coefficient of thermal expansion of the composite filler was reduced. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) provide thermal protection for high-temperature components of aero-engines and steam turbines, but are susceptible to failure under thermal cyclic loads. The effective design of interfacial texture is one of the approaches to enhance the lifetime of ceramic TBCs. In this study, four types of interfacial textures were designed on the surface of substrates, and 8YSZ coatings of equal thickness were prepared using atmospheric plasma spraying, and thermal cycling tests were carried out. Meanwhile, the thermal cycle lifetime, microstructure evolution, residual stress, and energy release rate criterion were also studied. The optimal morphology and parameters of the texture are determined. It is found that the lifetime of the concave trapezoidal texture is the longest, with a deflection angle of 67°, diameter of 700 μm, depth of 500 μm, and spacing of 5 mm. This study can provide theoretical guidance for the interfacial texture design of ceramic TBCs. [ABSTRACT FROM AUTHOR]

Temperature-dependent nano SiC obtained from the polymer-derived ceramics method was used to modify ZrC coating by supersonic atmosphere plasma spraying. The crystallinity and grain size of SiC increased with increasing annealing temperatures. SiC annealed at 1400 °C exhibited the lowest crystallinity of 48.4 %, which led to massive re-pyrolyzing gas spillage from the modified ZrC coating during ablation, causing penetrating cracks. SiC annealed at 2100 °C exhibited the largest grain size of 190.4 nm, which could produce locally massive amounts of SiO 2 , accelerating the sintering of ZrO 2 in the coating and leaving maximum residual stress. SiC annealed at 1800 °C possessed a medium crystallinity of 81.5 % and a grain size of 12.2 nm, which was favorable to improve the ablation resistance of ZrC coating for forming fine-grained ZrO 2 scale with minimum residual stress. Our work provides a novel perception of the microstructure-property relationship for ablation-resistant coating under extreme conditions. [ABSTRACT FROM AUTHOR]

In this work, we use a simple and efficient method to introduce "TiO 2 –Al" interfacial layers between the B 4 C particles and aluminium (Al) matrix in TiO 2 @B 4 C/Al composites by combining the ball milling dispersion process with the pressure infiltration technology. It is anticipated that it would improve the mechanical properties and corrosion resistance. The work demonstrates that the coefficient of thermal expansion (CTE) of the "TiO 2 –Al" interfacial layer is between those of the matrix and the reinforcement. Thus, it relieves the residual stresses in the composites. Furthermore, the low residual stress of the composites achieved by introducing the "TiO 2 –Al" interfacial layer results in delayed failure and the low corrosion tendency. The composites containing "TiO 2 –Al" interfacial layers show remarkable bending properties (a strength of 668.6 MPa) and good corrosion resistance (a low corrosion current density of 6.81 μA cm−2). Thus, the TiO 2 @B 4 C/Al composites exhibit remarkable mechanical properties and corrosion resistance compared with the composites reported in the literature. [ABSTRACT FROM AUTHOR]

The shot peening procedure enhances the mechanical characteristics with the transformation of compressive residual stresses which helps in the increment of operational lifespan of the product. The study comprehensively analyzed the effect of consecutive shot peening procedures up to four peening passes with the coverage increases 100% on each peening pass up to 400% on the laser powder bed fused austenitic stainless steel and compared with the as-built condition focusing on surface characteristics, mechanical characteristics, and corrosion potential. Surface damage of the peened samples was found very minimal with the absence of visible scan tracks and unmelted powder particles due to the controlled peening parameters. The inducement of compressive residual stresses (−625 MPa) was observed to be higher at the fourth consecutive peening passes without strain-induced martensite, with an increment of hardness proportion of 29.12% with a depth of 1 mm, and increment of corrosion resistance across each peening pass. [ABSTRACT FROM AUTHOR]

The matrix cracking of carbon fiber reinforced epoxy resin based composites (CFRPs) at cryogenics (such as liquid nitrogen temperature) is a major issue affecting the normal operation of deep space and deep‐sea detectors, as microcracks caused by the thermal residual stress of both can reduce the structural integrity of the devices. In this work, we report an epoxy (EP) nanofiller CuO nanorods (CuO NRs) with negative thermal expansion properties at cryogenics. Experiments showed that CuO NRs can effectively inhibit the shrinkage of EP at cryogenics and improve the mechanical properties of EP at cryogenics. A temperature dependent prediction model for the tensile strength of EP/CuO NRs was proposed, and the predicted results were in good agreement with experimental results. Finally, through a combination of experiments and theory, it was demonstrated that the tensile strength of EP/CuO NRs at cryogenics is jointly enhanced by the enhancement effect of the nanomaterials and the axial compressive thermal residual stress between EP and CuO NRs. Highlights: Successfully prepared CuO nanorods with negative expansion properties at low temperatures, and found that they can effectively inhibit the shrinkage of epoxy resin at cryogenics.At cryogenics, the expansion of CuO nanorods enhances their interface effect with epoxy resin and improves the tensile strength of epoxy resin composites.The theory of tensile strength of epoxy resin at cryogenics was proposed for the first time. Theoretical analysis shows that the low temperature residual thermal stress between CuO nanorods and epoxy resin is the main factor to improve its tensile strength. [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]

Gray cast iron (GCI) brake rotors are prone to corrosion, particularly in electric vehicles (EVs), owing to their regenerative braking systems. Ferritic nitrocarburizing (FNC) heat treatment has been used to improve the corrosion resistance and cleanability of GCI rotors. However, pre-existing residual stresses in the rotors can lead to distortion after FNC processing, thereby affecting the functional and tolerance requirements. This study investigated the effects of stress-relief (SR) heat treatment and natural aging (NA) on the natural frequency, damping properties, surface roughness, and geometric tolerances of GCI brake rotors before and after FNC treatment. The GCI brake rotors were subjected to SR and NA processes, followed by FNC treatment. The natural frequency, damping Q-factor, surface roughness, and geometric tolerances were measured and analyzed using two-way ANOVA at a 95% confidence level (α = 0.05). The results showed that SR heat treatment significantly reduced the effect of residual stresses and improved geometric tolerances compared to NA. The FNC treatment increased the surface roughness and slightly improved the damping properties but had an insignificant effect on the natural frequency. The combination of SR and FNC treatments provided the best overall performance in terms of quality, geometric tolerance, and surface finish. This study highlights the importance of SR heat treatment for optimizing the manufacturing process of FNC-treated GCI brake rotors for EVs. [ABSTRACT FROM AUTHOR]

Large residual stress induced by significant difference in the coefficient of thermal expansion compromises the mechanical performance of a brazed joint between the WC–Co cemented carbide (YG20) and 3Cr13 stainless steel in a cutting tool of shield machine. In this study, a melamine formaldehyde foam precursor was utilized to produce a 3D hollow carbon foam (HCF) used as interlayer through a high‐temperature carbonization process to aid in the brazing process of YG20 and 3Cr13. First, the morphology and microstructure of the HCF interlayer were revealed as a defect‐rich carbon shell with a hollow structure. Afterward, the effects of introducing the as‐prepared HCF interlayer on the joint microstructure and shear performance were investigated. Results indicate that the HCF interlayer contributed to phase homogenization and, moreover, the residual stress relieving through in situ forming a core (metallic matrix)–sheath (ceramic shell) structure. This method outperformed the direct brazing approach without using an interlayer, with a 41% increase in the joint shear strength due to the synergistic strengthening mechanism of the HCF through residual stress reliving and joint seam toughening. Based on the results, in spite of the residual stress, the fast load transfer and the compensation from the matrix core to the ceramic sheath are responsible for the improved mechanical performance of the joint. [ABSTRACT FROM AUTHOR]

The effect of boron (B) on stress corrosion resistance of S31254 in the presence of residual stresses has been studied. The microstructure and corrosion resistance of S31254 containing B at different levels of cold deformation are analyzed in this study. In the results, it is shown that B favors the improvement of deformation uniformity of S31254. The grain boundary (GB) and slip bands have better corrosion resistance at 5% deformation, and the overall corrosion resistance is better than that of the undeformed state, with smaller passivation current density and narrower width of GB corrosion grooves, especially for the 40B samples. At 30% deformation, the overall corrosion resistance of 40B S31254 is better than 0B due to improved deformation uniformity. [ABSTRACT FROM AUTHOR]

Residual stress (RS) significantly impacts the mechanical performance of components. Measurement of RS often provides incomplete data in terms of components of stress and spatial density. Employing such fields in finite element simulations results in significant modification of the field to achieve equilibrium and compatibility among strains. To overcome this, an iterative stress reconstruction algorithm (ISRA) is developed to estimate 3D RS fields that satisfy equilibrium, are stress component-wise complete, and represent the characterized data sampled. An Al 7075-T651 plate and an additively manufactured (AM) A36 steel wall are considered for RS reconstruction using measurement data from the literature. A maximum variation of ~2.5 MPa in the Al plate, and ~10 MPa in the steel wall are observed between the reconstructed and measured stresses. Furthermore, unknown stress components emerge and reach significant magnitudes (upto ~2.3 MPa in the Al plate and ~45 MPa in the AM wall) during ISRA. Indeed, it is found that minor errors in measurement or data processing are eliminated through the physical requirements during ISRA. Employing a reconstructed RS field is hence not just more accurate given its compatibility, but it additionally corrects for minor errors in measurement. Furthermore, it is found that spatially dense measurement data result in convergence with fewer iterations. Finally, although ISRA yields a nonunique solution dependent on boundary conditions, measurement errors, fitting errors, and mesh density, it accommodates for uncertainties and inaccuracies in measurement, as opposed to failing to reach a physically realistic converged solution. [ABSTRACT FROM AUTHOR]

Titanium Grade 2 strips or sheet metal, a commercial alloy used extensively in airframes, aircraft engines, marine applications, tubing and orthopedic implant/prosthetics, has been manufactured employing Large Strain Extrusion Machining (LSEM) process. LSEM is one of the severe plastic deformation processes (SPD), involving very large strains and shear forces, converting bulk material into very thin strips or sheets in a single pass. The strips or sheets produced by LSEM have improved bulk mechanical properties over the raw material owing to severe plastic deformation. The current work focusses on the influence of cutting speeds on the fabricated Titanium Grade 2 strips by LSEM on surface integrity in terms of surface microstructure, hardness, surface roughness, induced surface residual stresses and corresponding surface corrosion. The study showed that variation in cutting speed has significant bearing on surface characteristics of the strips produced employing LSEM. At comparative lower cutting speeds, surface quality and corrosion resistance of the produced strip is enhanced. [ABSTRACT FROM AUTHOR]

A novel sintered-joining of Al 2 O 3 and AlN is achieved for the first time using micro-Ag particle interlayers in air. In comparison with reactive air brazing, this method addresses the issue of reduced strength caused by air holes in brazed joints. Also, this sintered-joining method can be performed at a lower temperature (920 °C), improving the joint strength by relieving the residual stresses. The sintering effect of micro-Ag particles and their high density of dislocations promote the recovery and recrystallization of the Ag interlayer, as well as the interdiffusion of Ag and ceramic. Ag–O clusters formed at the interface can be embedded into oxygen vacancies on the ceramic surface, playing a key role in interfacial joining. By optimizing joining temperature, assembly pressure and holding time, a maximum joint shear strength of 85.2 MPa is achieved at 920 °C for 30 min with an assembly pressure of 1 MPa. This study successfully prepares Al 2 O 3 /AlN joints with excellent mechanical properties, providing a reliable foundation for the fabrication of power integrated circuits with efficient operation. [ABSTRACT FROM AUTHOR]

Ball burnishing (BB) is a surface finishing process that involves moving the tool while pressing it against the workpiece under rolling contact. We investigated the effects of BB on the fatigue strength of an aluminum alloy with a semicircular slit simulating an initial surface defect. After performing BB under a typical condition, compressive residual stress was induced to a depth of 0.4 mm, with a reduction in surface roughness by 81%. Consequently, the fatigue strength increased by 22%. BB prevented the fatigue strength reduction caused by the 0.1 mm deep slit. The result indicated that BB could render the below 0.1 mm deep surface defect harmless in terms of fatigue strength. The maximum depth of surface defect that can be rendered harmless is 0.18 mm according to fracture mechanics, which is in agreement with the experimental results. Highlights: Ball burnishing (BB) can introduce large compressive residual stress along with smoothing.BB can render a 0.1 mm deep slit harmless in terms of fatigue strength.Defect size rendered harmless can be estimated based on fracture mechanics.Compressive residual stress is the main factor rendering the surface defect harmless. [ABSTRACT FROM AUTHOR]

Despite the many advantages that additive technologies have over subtractive ones, low porosity levels, good mechanical properties, and low residual stresses remain the most pressing issues that need further research. In particular, the latter can cause a mismatch between the desired geometry and the geometry that can be achieved. In this work, a process window for the Laser Powder Bed Fusion (LPBF) process of Ti-6Al-4V alloys, has been identified. The micro-warping phenomenon, which causes the deformation of the printed part during the printing job and the failure of the process, was taken into account together with the parts' strength, ductility, and porosity. The occurrence of micro-warping phenomena was assessed by the new Warping Alert (WA) parameter, which depends on the parameters P and v. It was found that, before balling, micro-warping limits the process window in the laser power (P) – laser velocity (v) plane. However, optimal mechanical performances can be found in the proximity of the micro-warping zone, thus making it extremely important to determine the WA threshold value to the process design. [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]

The laser powder bed fusion additive manufacturing (LPBF-AM) technique enables the production of near-net-shaped metal components, but the concentrated heat input employed during manufacturing leads to the development of significant internal residual stresses. These residual stresses may cause considerable issues such as distortion, crack initiation during fabrication, and premature failure during service. In this study, neutron diffraction experiments were performed on a nickel-based superalloy, Hastelloy-X, to evaluate the state of residual stresses below and near the surface of as-built specimens as a function of LPBF-AM core process parameters. In addition, a crystal plasticity method was used to determine the diffraction elastic constants to provide a better estimation of residual stresses for textured specimens. The results indicate large tensile residual stresses of about 660 MPa along the scanning direction, counterbalanced by compressive ones below the surface. It is shown that internal and surface residual stresses increase with the laser specific energy. The use of various diffraction peaks for determining residual stresses is discussed and it is shown that while trends do not change, the magnitudes of measured stresses vary. [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]

The buckling curves, which enable the prediction of buckling resistance of steel structural elements, are physically connected with their type of cross-section, initial out-of-straightness, and the magnitude of residual stresses due to the different manufacturing technologies. It is known that hot-dip galvanisation changes and relives residual stresses, but so far the current design provisions do not take directly into account the impact of hot-dip galvanising on the reduction of residual stresses, and thus the reduction the generalised imperfection in the Ayrton-Perry model. The paper presents the difference between the relative buckling resistance of steel angles with residual stresses resulting from hot rolling and the same elements in which the magnitude of residual stresses was decreased by the hotdip galvanising process. Carried out tests and geometrically and materially non-linear analyses with imperfections (GMNIA) have shown that angles with residual stresses reduced by heat treatment caused by hot-dip galvanising have higher buckling resistance compared to those with residual stresses after hot rolling. This increase ranges from 2 to 7%. The analyses carried out confirmed that the predicted reduction factors c exhibit values closer to the buckling curve 'a', but these values do not reach the 'a0' curve recommended by the EN 50341-1 standard. [ABSTRACT FROM AUTHOR]

The Experimental study investigates the impact of ultrasonic-assisted face turning (UAFT) on cutting forces, tensile residual stress, and surface topography. The primary objective is to identify optimal cutting parameters that yield a smoother surface finish while concurrently reducing cutting forces and tensile residual stress. The tests were conducted on a lathe machine equipped with ultrasonic assistance, using 1.7225 steel as the workpiece material. Various cutting parameters, including feed rate, spindle speed, and turning state, were varied. The results illuminate the significant efficacy of ultrasonic assisted face turn (UAFT) in improving surface topography, compared to conventional turning (CT). The optimal turning parameters for achieving the smoothest surface finish were determined to be a higher spindle speed and lower feed rate. Moreover, the introduction of ultrasonic vibration led to a substantial reduction in cutting forces, primarily attributable to the diminished attrition between the cutting tool insert and the work part. Overall, the experimental study demonstrates the effectiveness of ultrasonic-assisted face turning in enhancing surface topography, with an improvement of approximately 39%. Additionally, the study demonstrated a reduction in cutting forces by approximately 50% and a decrease in tensile residual stress by approximately 33.8%. These findings underscore the potential of ultrasonic vibration as a tool for optimizing cutting parameters to achieve desired surface finishes in machining applications. [ABSTRACT FROM AUTHOR]

Grinding is one of the most complex techniques of removing material from parts by the countless number of hard and sharp abrasive grains. Grinding creates a substantial amount of heat, which causes surface or subsurface damage, thermal damage, change in the metallographic structure of the material surface. In order to lesson these phenomena, cutting fluids are frequently used in the grinding zone. Minimum Quantity Lubrication (MQL) was suggested as a cost-effective and environmentally friendly lubrication for reducing heat and the expenses of grinding fluid. Despite the fact that MQL plays a crucial role in increasing machining performance, reviews on its use in high-speed machining are conflicted. This review article examines some of the most frequent nanofluids used in MQL systems during grinding processes. Nanofluids in MQL technique are a cutting-edge and eco-friendly approach that substitutes both traditional MQL and flood coolant in the grinding process. The effects of nanofluids on workpiece surface roughness, tangential force, coefficient of friction, G-ratio, grinding specific energy, wheel wear, grinding temperature, workpiece hardness and residual stress are thoroughly discussed and the findings were compared. After reading this review article, one may quickly gain an overview of existing research in the fields of nanofluids. Finally, this study looks at the thermo-physical characteristics of different nanofluids such as contact angle, thermal conductivity, and viscosity. [ABSTRACT FROM AUTHOR]

The present study is focused on the investigation and simultaneous optimisation of MQL-turning parameters with the application of the weighted Mayfly algorithm for sustainable machining of Nimonic 75. The nanofluid used for the experimental work is graphene oxide dispersed rice bran oil. The parameters of cutting velocity, feed rate, nozzle angle, and nozzle distance were considered for processing characteristics of force, roughness, and residual stress. The weight in the Mayfly algorithm is determined using a grey relational coefficient (GRC). The weight importance calculated for each response is compared with the different schemes in the algorithm. The result showed that the parameters with these schemes had different optimal values. At optimal factor levels determined using GRC in the Mayfly, the algorithm improved 'F-value = 0.40' compared to factor levels in other methods. Compared to experimental results, the optimised value reduces the surface roughness, cutting force, and residual stress by 30%, 3%, and 10%, respectively. The feed rate, cutting velocity, and nozzle distance are the most vital parameters for optimising the output response with the GRC-Mayfly process. [ABSTRACT FROM AUTHOR]

The author aimed to enhance the functional characteristics of the proposed Ti–Ni shape memory alloy (SMA) with a functionally graded property by ultrasonic shot peening (USP) treatment. To the author’s knowledge, this was the first study in which USP treatment was utilized for manufacturing functionally graded SMAs; previous studies relied on powder metallurgy and hot rolling techniques. By examining the various properties of the specimens, the author confirmed the effects of hot rolling and USP treatment. Hot rolling and USP treatment led to an increased Vickers hardness. Hot rolling primarily contributed to densification, while USP treatment induced work hardening, resulting in increased hardness. The surface of TiNi SMA sintered bodies experienced compressive residual stress up to 300 MPa because of the USP treatment. The transformation peaks in differential scanning calorimetry curves shifted toward lower temperatures as the Ni content increased. Therefore, the transformation properties of the functionally graded shape memory alloys were unaffected by the USP treatment. The USP treatment work-hardens the sintered TiNi SMA produced through hot rolling. The effect was more pronounced in the high-Ni-concentration region, resulting in the development of a functionally graded behavior of deformation resistance. [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]

The study aims to investigate the effects of carburizing (C), carburizing and nitriding (C+N) sequential treatment on microstructure, microhardness distribution, residual stress distribution and rolling contact fatigue (RCF) properties of M50NiL bearing steel. The results showed that the fatigue limit of the C+N samples was 14.4% higher than that of the C samples. According to analyses of fatigue crack initiation and propagation behavior of RCF specimens revealed that the failure mechanism of the C specimens was deep spalling caused by fatigue crack in a large-angle propagation mode; whereas the C+N specimens had higher surface hardness and residual compressive stresses, which suppressed fatigue crack initiation and propagation, and the failure mechanism was changed to fatigue crack in a small-angle propagation mode caused by shallow spalling. Transmission electron microscopy analysis of C+N specimens after RCF experiments revealed that the dislocations proliferate and shear the carbonitride precipitation phases during the RCF experiments, and the microstructure and precipitation phases of the M50NiL steel are refined, which effectively inhibited the rate of fatigue crack initiation and propagation, and substantially enhanced the RCF life of M50NiL steel. [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. [ABSTRACT FROM AUTHOR]

Thermal residual stress generated during curing is known to be detrimental to mechanical performance of a carbon composite. Fiber prestressing technique has been developed for decades to counterbalance these negative effects. Although there have been some achievements in development of the prestress mechanisms, these are mainly based on the extrapolations from macroscopic mechanical characterizations, lack of direct evaluation of the in‐situ in‐plane strain or stress evolution mechanisms, in order to reveal the impact induced by different prestressing methods. Here, we investigated the in‐situ strain evolution mechanisms in producing a prestressed carbon composite. Since clamping of the uncured prepreg is the most challenging, both the strain evolutions with and without precured prepreg edges were evaluated to reveal the underlying mechanisms induced by stress relaxation during fiber prestressing. Mechanical tests in terms of Charpy impact and three‐point bending, as well as fractured morphology were carried out to evaluate the prestress effects. The underlying mechanisms were then proposed to reveal the fundamentals in producing a prestressed composite. These are expected to revolutionize industrial production and applications of prestressed polymeric composites, indicating detrimental mechanisms on precuring strip ends following conventional prestress procedures. Highlights: There is an optimal prestrain level to maximize properties of a composite.Internal strain development is dependent on the fiber clamping methods.Stress relaxation is beneficial to induce compressive stress within a composite.In‐situ strain evolution mechanics is revealed for prestressed carbon composite. [ABSTRACT FROM AUTHOR]

This study explored the impact of microstructure and residual stresses on the fracture behavior of as‐deposited thermal barrier coatings (TBCs). Two distinct air plasma sprayed TBCs, Coating A (conventional lamellar porous) and Coating B (dense vertically cracked), were investigated. Coating A involved coarser but less dense powders as feedstock and a lower substrate temperature during deposition. Further, Coating A had ∼2.5$\sim 2.5$ times higher randomly oriented porosities, finer grains, lower hardness, and elastic stiffness. Strikingly, however, the fracture strength was higher for the porous as‐deposited Coating A. The answer to this apparent contradiction emerged from the intergranular residual stresses. These were measured using both X‐ray diffraction and high‐resolution‐electron backscattered diffraction. Coating B, deposited at a higher substrate temperature, had clear growth selection of (102)$( {1\ 0\ 2} )$ oriented grains. These also had more out‐of‐plane normal and shear residual stresses. The growth selection induced residual stresses appeared responsible for the decohesion of Coating B from the substrate and, correspondingly, lower fracture strength. [ABSTRACT FROM AUTHOR]

In this study, the Time-Temperature-Crystallinity Superposition Principle (TTCSP) was applied to determine the viscoelastic behavior of Thermo-rheological Complex Materials (TCM), specifically Carbon fibre/Poly-Ether-Ketone-Ketone (CF/PEKK) composites. The study investigated the effects of various parameters on the viscoelastic behavior of the composites, such as the degree of crystallinity after different melting temperatures, relaxation, and crystallization times. The TTCSP was utilized on the relaxation data to generate great-grand master curves for the degree of crystallinity for different laminate lay-ups. Hot press forming was employed to manufacture samples under different processing conditions, including various melting and cold crystallization temperatures. Differential Scanning Calorimetry (DSC) was employed to calculate the degree of crystallinity of CF/PEKK composites, while the Dynamic Mechanical Analyzer (DMA) was used to obtain the relaxation data. The generated great-grand master curves proved effective in predicting the relaxation behavior of the composites consolidated using single and double hold cycles at different melting temperatures and crystallization times, respectively. The great-grand master curves presented in this study can serve as valuable tool to calibrate key viscoelastic and/or thermo-viscoelastic material models for aerospace-grade CF/PEKK composites. These models are crucial for simulations aimed at predicting residual stresses and process-induced deformations during the thermoforming process. [ABSTRACT FROM AUTHOR]

To improve the mechanical properties of the rolling body surface of wind power bearings, extend its service life. In this study, a large-scale molecular/atomic parallel processor LAMMPS was introduced, and then the process of magnetron sputtering technology in the preparation of DLC/Ni-DLC thin films on the 42CrMo substrate material was simulated. The effects of deposition parameters such as sputtering temperature, sputtering voltage, deposition air pressure, and Ni doping on the residual stress, film base bonding, and organizational structure of the thin films were investigated. The simulation results show that for different deposition parameters, the atomic tensile and compressive stresses existed simultaneously in DLC/Ni-DLC films, and the residual stresses were between − 0.504–5.003 Gpa and − 2.11–0.065 Gpa, respectively; the doping of Ni effectively improved the distribution of hybrid structure and the mechanical properties of the DLC films, and the ratio of the sp3 hybrid structure in the film organization was about 2.56 times higher than that of the non-doped films, and the membrane base bonding force was increased by 32.78% and the residual stress is reduced and transitioned from tensile stress to compressive stress. In addition, it was observed that the thickness of the mixed layer of DLC/Ni-DLC films with the substrate was not increased after the thickness of the mixed layer was extended to about 2 nm. Nickel doping and reasonable control of deposition parameters help to reduce the residual stress and improve the bonding strength of the film by changing the organizational structure of the film, which provides an important theoretical and scientific basis for the preparation of low-stress, high-performance and long-life DLC films and the wide application of rolling bodies for wind power bearings under complex working conditions. [ABSTRACT FROM AUTHOR]

Electrodeposited chromium plating continues to be widely used in a number of specialized areas, such as weapons, transport, aerospace, etc. However, the formation of texture, hydrogen content and residual stress can degrade the serviceability and lead to material failure. The effect of post heat treatment processes on the relationship of texture, hydrogen content, residual stress and corrosion resistance of hexavalent [Cr(VI)] chromium coatings deposited on Cr–Ni–Mo–V steel substrates was investigated. Macrotexture was measured by XRD. Microtexture, dislocation density and grain size were studied by EBSD. With the increase of the heat treatment temperature, it was found that the fiber texture strength of the (222) plane tended to increase and subsequently decrease. Below 600 °C, the increase in the (222) plane texture carried a decrease in the hydrogen content, residual stress, microhardness and an increase in the corrosion resistance. In addition, crack density and texture strength were less affected by the heat treatment time. Notably, relatively fewer crack densities of 219/cm2, a lower corrosion current density of 1.798 × 10−6 A/dm2 and a higher microhardness of 865 HV were found under the preferred heat treatment temperature and time of 380 °C and 4 h, respectively. The hydrogen content and residual stress were 7.63 ppm and 61 MPa, with 86% and 75% reduction rates compared to the as-plated state, respectively. In conclusion, in our future judgement of the influence of heat treatment on coating properties, we can screen or determine to a certain extent whether the heat treatment process is reasonable or not by measuring only the macrotexture. [ABSTRACT FROM AUTHOR]

Carburized steel shafts are commonly used in industry due to their good wear resistance and fatigue life. If the surface of carburized shafts exhibits an undesired tensile stress, shot peening treatment may be required to alter the stress condition on the surface. In the present study, the effects of shot peening pressure (3–5 kg/cm2), time (32–64 s), and material (stainless steel, carbon steel, and glass) on the residual stress, retained austenite, microhardness, and surface roughness of the carburized shafts were investigated. The experimental results showed that the surface residual tensile stress was changed into compressive stress after the shot peening treatment. The shot peening effects increased with the increasing peening pressure and time. In addition, a significant decrease in the amount of retained austenite in the subsurface region was observed. Peening with different materials can affect the peening effect. Using glass pellets exhibited the best shot peening effect but suffered massive pellet fracture during processing. In overall consideration, the optimal peening parameters for carburized steel shafts for practical industrial applications involved using the stainless-steel pellets with a peening pressure of 5 kg/cm2 and a peening time of 64 s. The maximum residual stress was −779 MPa at a depth of 0.02 mm, while the highest surface microhardness was 827 HV0.1. [ABSTRACT FROM AUTHOR]

Metal composite parts are widely used in different industries owing to their significant improvement in material properties, such as mechanical strength, electrical conductivity, and corrosion resistivity, compared to traditional single metals. Such composite parts can be manufactured and processed in different ways to achieve the desired geometry and quality. Among various metal forming techniques, drawing is the most commonly used process to produce long composite wires or rods from raw single materials. During the drawing process of composite wires or rods, not only does the core radius ratio change, but the core or sleeve layer may also undergo necking or fracture due to excessive tensile stresses in the softer layer. In this paper, bimetallic rods with AISI-1006 low-carbon steel cores and C10100 oxygen-free electronic copper sleeves are modeled using the finite element software DEFORM. The simulation models are verified by drawing experiments. The effects of initial bonding conditions, the initial core ratio, reduction ratio, semi-die angle, drawing speed, and friction on the plastic deformation behavior of the bimetallic rods are investigated. The results indicate that the initial bonding conditions have a great impact on the deformation behavior of the billets in terms of strain distribution, material flow, residual stress, and the final core ratio. The permissible forming parameters for obtaining a sound product are investigated as well. With the aid of these analyses, the drawing process and the quality of the products can be controlled steadily. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge of ranking the factors that affect the erosion resistance of lightweight alloys, with a specific focus on aluminum alloys. A three-factor, four-level orthogonal experimental design was employed to examine the influence of various sand particle sizes, erosion speeds, and sand concentrations on the abrasion qualities of these alloys. Parameters such as mass loss, depth, residual stresses, and failure mechanisms were assessed to determine erosion performance. Analysis of variance (ANOVA) and regression analysis of the three key factors were performed. Our findings resulted in an erosion rate formula: erosion rate = 0.679 sand particle size +0.067 sand concentration −0.002 erosion velocity +0.285. Our findings indicate that particle size is the most significant factor affecting erosion rate, with sand concentration and erosion velocity being secondary factors. The failure mechanism reveals that larger sand particles tend to produce deeper slides, and higher sand concentrations result in an increased number of slides. A lower concentration leads to the appearance of erosion pits. And the test conditions of high concentration and low velocity lead to more serious brittle fractures of the substrate, often accompanied by the appearance of cracks. [ABSTRACT FROM AUTHOR]

UHMWPE nascent powders have been commercially processed by sintering for decades although key aspects of the mechanisms and kinetics of this process are not fully understood. Herein, the volume change during each stage of the sintering is monitored by in‐situ measurements with other characterization methods. Results indicate that the α‐transition plays a crucial role in the early stages of the sintering process. Without pressure during sintering, a large expansion is observed during heating through the α‐transition well before melting and this apparent volume change is also related to the residual stress resulting from the compaction. However, the application of a moderate pressure during heating leads to a significant densification. Specifically, five distinct processes are identified from the in‐situ measurements via customized pressure sintering apparatus. These include room temperature densification, subsequent densification while heating through the α‐transition, process of melt explosion that involves the enthalpic process of crystal melting and the entropic process density changes during the isothermal sintering of non‐equilibrium melt, and the subsequent recrystallization under pressure. The density evolution offers a comprehensive understanding of the intricate processing of UHMWPE nascent powder and this can be effectively employed to investigate the impact of various processing parameters on the sintering process. [ABSTRACT FROM AUTHOR]

The tensile properties of sintered C f -ZrB 2 /SiC UHTCMCs were investigated for different lamination sequences, revealing ultimate strengths of 570 MPa (0°/0°), 120 MPa (0°/90°), and 40 MPa (90°/90°). The results facilitated modeling the material's non-linear tensile response, characterized by a remarkably prolonged plateau with pseudo-plastic behavior, followed by stiffness recovery before ultimate failure. A simplified analytical model was developed to predict this behavior originated by residual thermal stresses and inelastic phenomena. A complete constitutive law was then developed and implemented in a FE model, utilizing a bi-phasic approach including Drucker-Prager plasticity and orthotropic ductile damage. Two-step analyses were performed, starting with a thermal step to represent the buildup of a self-equilibrating RTS state in the material phases, followed by a mechanical simulation. This demonstrated the model's efficacy in capturing the non-linear response in both homogeneous and cross-ply lay-ups, contributing to advancements in materials engineering and the design of UHTCMCs-based hot structures. [Display omitted] [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. [ABSTRACT FROM AUTHOR]

The effect of shot peening (SP) on pre‐fatigue tested carburized steel was investigated. Plane‐bending fatigue tests were conducted on carburized CrMo steel that was pre‐fatigue tested and treated with SP. Fatigue cracks were induced by pre‐fatigue tests with a stress amplitude of σa = 1000 MPa, and the number of the pre‐fatigue test cycles was 2.0 × 104 (L5 test) and 4.0 × 104 (L15 test). We compared the fatigue lives of the fatigue‐damaged and smooth specimens without fatigue damage treated with the same SP. The fatigue life of the L5 tested specimens with SP was longer than that of the non‐fatigue damaged smooth specimens after SP. Therefore, the fatigue cracks introduced by the L5 test can be rendered harmless by SP. Furthermore, near‐surface material properties were evaluated and the mechanisms of rendering surface cracks harmless were investigated. [ABSTRACT FROM AUTHOR]

Mode II (in-plane-shear) delamination tests are more complex than mode I (opening) due to the presence of a contact force between the two arms. This force is essential for the calculation of the energy release rate (ERR) and is closely linked to friction effects. A novel formulation is presented in this article to estimate the contact force analytically. Specifically, the contact force is derived within the context of the rigid, semi-rigid, and flexible joint models. The analytical solutions consider the case of a generally layered composite laminate with residual hygrothermal stresses and are used to evaluate the ERR. The new formulation is compared with numerical models created using the Virtual Crack Closure Technique (VCCT) and the Cohesive Zone Method (CZM) for a fiber–metal laminate. The results show that the new formulation provides nearly identical ERR predictions to those of the VCCT and CZM models. Additionally, it is demonstrated that the effect of friction on the ERR is less than 1%. [ABSTRACT FROM AUTHOR]

The cure‐induced residual stresses have a significant influence on the deformation and mechanical properties of composites. Moreover, the cure‐induced residual stresses exhibit multi‐level and multiscale distributions due to the complexity of micro‐structure of composites and anisotropic characteristics. In this paper, a computationally efficient multiscale procedure is proposed to predict the microscopic residual stresses induced by cure temperature, cure shrinkage and macroscopic residual stresses, which is based to the linear viscoelastic theory combined with the micro‐mechanics method. The instantaneous microscopic residual stresses are expressed as a linear combination of the instantaneous temperature increment, degree of cure increment and macroscopic strain increment at all times of the cure process until to the current time. The proposed method is verified in comparison with the published results in literature and the microscale FEA at different length scales, respectively. The results show that the proposed method is about a thousand times faster than directly using FEA in the microscale RVE model once the influence coefficient matrices are determined. At length, the microscale stresses of all nodes of the entire macroscale model are examined by using the proposed method. It is found that the thermal‐chemical‐mechanical loads lead to serious microscopic stresses for the matrix and interphase constituents, especially for those due to the macroscopic residual stresses. Highlights: Microscale residual stress is written as a linear combination of macroscale loads.Applying macroscale loads on microscale FEA model to obtain influence matrices.The presented model avoids repeatedly FEA microscopic to improve the efficiency.The online time required for the proposed model is much less than microscale FEA.The microscale stress increases the risk of matrix cracking and interface bonding. [ABSTRACT FROM AUTHOR]

Highlights In this study, an optimum process parameter space is proposed by comparing autoclave, oven curing and vacuum infusion process of manufacturing of GFRP composites. The process parameters, such as the degassing time of resin‐hardener mix, single or double vacuum bagging (DVB), fiber volume fraction and condition of the vacuum pump (VP) were considered. The novelty of the study shows that a VP Off and 5 min degassing condition exhibited 27%, 18% and 27% increase in tensile modulus, tensile strength and interlaminar shear strength as compared to the other methods. The normalized tensile strength, on the other hand, was comparable with DVB, oven and autoclave curing. A magnitude of 1.5 MPa of residual stress was measured with the help of x‐ray diffraction (XRD). This was verified by a Raman Spectroscopy, which showed a residual strain of 0.2% at a spectral peak of 1186 cm−1. The proposed methodology would assist the industries in choosing the right combination of process parameters required for a targeted tensile and interlaminar performance. Effect of out‐of‐autoclave and autoclave processes on the performance of GFRP was studied. Degassing time, vacuum bagging and Vacuum pump conditions were investigated. Vacuum pump Off and 5 min degassing time were found to be optimal. Tensile and Interlaminar shear strength were improved by 18% and 27% at optimal condition. [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]

Reducing non‐radiative recombination caused by defects at buried interfaces is crucial to the development of efficient and stable perovskite solar cells (PSCs). Herein, supramolecular cucurbit[5]uril (CB[5]) is introduced into the SnO2 layer, where it engages in host–guest interactions to suppress oxygen vacancies in SnO2, prevent particle aggregation, and enhance the electron mobility of SnO2. By serving as a bridging agent at the buried interface between SnO2 and the perovskite layer, CB[5] reduces the defect density and improves the carrier extraction efficiency. It also reduces the surface energy of the SnO2 substrate, facilitates the formation of large grains in the perovskite film, alleviates residual lattice stresses, and enhances the film quality. Consequently, the PSC with CB[5] shows a champion power conversion efficiency of 24.83%. Moreover, an unencapsulated device incorporating CB[5] retains more than 87% of its initial PCE under continuous illumination at the maximum power point tracking for 1000 h. This study pioneers the utilization of cucurbiturils in PSCs and provides insights into how supramolecular compounds can regulate buried interfaces. [ABSTRACT FROM AUTHOR]

In this study, composites obtained through low-temperature carbonization of elastomeric matrix highly filled with graphite, carbon black and short carbon fibers were studied for the purpose of determining residual stresses at different scales using a combination of several complementary methods. The state-of-the-art techniques included X-ray stress analysis using the sin2 ψ method, the micro-ringcore technique via Focused Ion Beam milling and Digital Image Correlation (FIB-DIC), the contour method, the strain gauge method, and the hole drilling technique with digital laser speckle pattern interferometry (DLSPI). It was found that the contour method could not be used implemented for residual stress evaluation due to the low electrical conductivity of composite. Moreover, the DLSPI hole drilling method did not reveal any fringes indicating significant residual stress level exceeding a few MPa. The strain gauge method also revealed a narrow residual stress distribution with an average value of approximately zero. In contrast, the X-ray sin2 ψ method as well as FIB-DIC technique both returned values of about 150-250 MPa. A hierarchical model of the composite is proposed based on the Davidenkov Type I-II-III stress classification that provides an explanation of these observations. [ABSTRACT FROM AUTHOR]