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: Simulate Additive software was used to simulate and analyze the additive manufacturing processes of a typical large-sized thin-walled component--exhaust pipe. The results show that the SLM formed exhaust pipe parts without constraints have high residual stress and significant deforma¬tion. The post-processing releases residual stress in the parts, but the overall deformation of the parts further increases to 3.5 mm, with a maximum deformation of 9 mm. A lattice structure was intro-duced with high specific strength and stiffness as an auxiliary structure for controlling deformations, and a lattice processing scheme was designed with sufficient resistance to deformation and may be removed through post-processing. The cell type is QuadDiamond, the rod diameter is as 1.3 mm, the od length is as 19 mm, and the width of the lattice region is about 60 mm. The SLM test results of he exhaust pipe parts under lattice constraints are quite consistent with the numerical simulation results. The cloud image results of the three-dimensional scanning show that the overall deformation of he part is about 1 mm, and the maximum deformation does not exceed 2.5 mm, meeting the require¬ments for the part use. The above results show the effectiveness of using lattice structure in deformaton control of large-sized thin-walled parts formed by SLM. [ABSTRACT FROM AUTHOR]

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The current study uses a Finite Element (FE) Method to forecast residual stresses and deformation caused by the GTA welding process. The authors use a 5 mm thick stainless steel plate for the analysis. Residual stress and distortion predictions are made by successfully coupling thermal and mechanical studies. Mechanical and thermal analyses of moving heat source-exposed plates were conducted sequentially. Applications such as ANSYS and SOLIDWORKS are used to do the FE analysis. In transient thermal analysis, the arc's heat input has been modeled using a Gaussian distribution. Consideration of temperature-dependent physical and mechanical parameters is integral to the modeling process. The welding heat in stainless steel welding and how it behaves inside the joint has significant effects in determining the welding joint distortion, mechanical properties, and the weldments fit with the design criteria due to stainless steel thermal properties. Subsequent mechanical analysis is fed the transient thermal histories to the model. Analyzing mechanical systems involves using the big displacement hypothesis. How restrictions influence distortion and residual stresses is quantitatively investigated. The anticipated stresses and distortion values are presented and discussed for various scenarios. Welding distortion was minimized when a copper backing plate was used, as shown by a lower maximum deformation measured compared to situations without the plate. The backing plate reduced maximum stress values and lowered residual stresses. A backing plate also made the fusion zone smaller and the temperature drop from the peak welding temperature to room temperature steeper. According to the research, using a copper backing plate during stainless steel welding may significantly reduce deformation and residual stresses. The results could improve stainless steel welding by choosing the best materials for backing plates and improving welding. Investigation results and the mathematical models of welding simulation can significantly improve stainless steel deformation-reducing techniques in many applications and introduce particular techniques to predicate the impacts of backing plates in such welding processes as food, chemical, Pharmaceutical, Oil and Gas, and water treatment industries. [ABSTRACT FROM AUTHOR]

In aircraft panel assembly, the interference fit unevenly distributed along the axial direction of the rivet holes leads to an uneven stress–strain field around the rivet holes. The uneven stress–strain fields of single rivets, when accumulated through multiple rivets, result in overall bending and twisting deformation, severely impacting the assembly coordination quality of the panel. This study introduces a numerical model using a single row of multiple rivets to explore cumulative deformation during both sequential and changing order riveting. The results show that the deformation in sequential riveting is mainly bending-oriented towards the driven head side, with the maximum displacement exhibiting a fluctuating accumulation trend as the number of rivets increase. In contrast, a changing riveting order can lead to a reduction in deformation accumulation. To reveal the technological mechanism behind deformation accumulation during the riveting process, a model correlating to the residual stress field was established. It was indicated that the continuous increase in the maximum equivalent bending moment in the axial section is the primary factor leading to deformation accumulation. Based on this finding, a pre-bending suppression method aimed at reducing the local maximum equivalent bending moment was proposed. Numerical calculations and experimental results showed that the maximum displacement of the specimen was reduced by 73.27%, proving that this method can effectively suppress the cumulative increase in deformation. [ABSTRACT FROM AUTHOR]

Thin-walled parts processed by five-axis CNC machine tools are widely used in aerospace and other fields due to their excellent performance. However, due to the weak rigidity of thin-walled parts, they are prone to deformation during milling, which poses great difficulties for efficient and precise machining of thin-walled parts. This paper introduces the classification and corresponding machining methods of thin-walled parts. By analyzing the causes and evolution mechanisms of errors in the machining process of thin-walled parts, and combining modeling methods with factors such as milling force, residual stress, and cutting chatter, the current research status of domestic and foreign scholars on deformation factors is summarized. At the same time, two deformation control methods, adaptive machining and error compensation, were introduced. Finally, the overall research status of thin-walled parts machining was summarized, and prospects for efficient and precise machining of thin-walled parts were proposed based on actual machining conditions. [ABSTRACT FROM AUTHOR]

Given the deformation issues in machining segmented equal-base bevel gears, this paper investigates the variations of additional stress during the machining process, considering the gear blank material, residual internal stress, and gear blank design. A model for calculating internal additional stress and torque during gear machining has been developed. The calculation formula for the bending deformation of the gear blank has been derived using the torque–area method. By analyzing the time-varying stiffness of the blank, a calculation model for the bending deformation of the gear blank has been constructed, and the projection analysis of gear stock deformation has been completed. Based on the cumulative superposition effect of its deformation projection, a calculation model for the overall deformation of the segmented gear blank has been formulated. The deformation calculation model has been validated through finite element simulation, deformation calculation, actual machining, and measurement verification. [ABSTRACT FROM AUTHOR]

It is of significant theoretical and practical value to study the deposition process and deformation behavior of cold-sprayed particles to find the deposition mechanism of cold-sprayed coatings, further improve the coating performance, and expand its application scope. However, observing the deposition process and particle behavior through experiments is difficult due to the brief deposition duration of cold spray particles. Numerical simulation offers a means to slow the deposition process and predict the critical velocity, deformation behavior, bonding mechanism, and residual stress of cold-sprayed particles. This paper uses finite element analysis software, including ANSYS LS Dynamic-2022 R1 and ABAQUS-6.14, alongside various prevalent finite element methods for numerically simulating cold spray particle deposition. These methods involve the Lagrange, Euler, arbitrary Lagrange-Euler (ALE), and Smoothed Particle Hydrodynamics (SPH) to investigate the cold spray particle deposition process. The recent literature primarily summarizes the simulation outcomes achieved by applying these methodologies for simulating the deposition process and deformation characteristics of different particles under varying cold spraying conditions. In addition, the reliability of these simulation results is analyzed by comparing the consistency between the simulation results of single-particle and multi-particle and the actual experimental results. On this basis, these methods' advantages, disadvantages, and applicability are comprehensively analyzed, and the future simulation research work of particle deposition process and deformation behavior of cold spraying prospects is discussed. Future research is expected to provide a more in-depth study of the micro-mechanisms, such as the evolution of the inter-particle and internal organization of the particles, near the actual situation. [ABSTRACT FROM AUTHOR]

Structures composed of aviation aluminium alloys, characterized by their limited rigidity and thin-walled configurations, frequently exhibit deformation after processing. This paper presents an investigation into T-shaped components fabricated from pre-stretched 7075-T7451 aviation aluminium alloy sheets, examining the effects of residual stress and the geometrical parameters of T-shaped components on their deformational behavior. A semi-analytical model, developed to elucidate the bending deformation of T-shaped components subjected to residual stress, was validated through finite element analysis and empirical cutting experiments. The experimental results revealed that the bending deformation deflection of the T-shaped specimen was 0.920 mm, deviating by a mere 0.011 mm from the prediction provided by the semi-analytical model, resulting in an inconsequential error margin of 1.2%. This concordance underscores the precision and accuracy of the semi-analytical model specifically designed for T-shaped components. Moreover, the model's simplicity and ease of application make it an effective tool for predicting the bending deformation of thin-walled T-shaped components under a range of residual stresses and dimensional variations, thereby demonstrating its significant utility in engineering applications. [ABSTRACT FROM AUTHOR]

Hardness of nanostructured metallic multilayers (NMMs) are often understood from their dependence on individual layer thickness (h), yet little is known about the impacts exerted by other microstructural factors. In this work, the effects of residual stress and interface coherency on the deformation mechanisms of Al/Ti NMMs with h = 2.5–52 nm were studied via experiments and molecular dynamics simulations. The residual stress was found to be tensile in Ti layers and compressive in Al layers in general, both of which tended to increase with decreasing h. Tensile stress of more than 2 GPa were measured in the Ti layers at h < 10 nm. Such high stress was related to the more coherent interfaces at small h, as confirmed by transmission electron microscopy analysis. Finally, molecular dynamics simulations showed that at h = 2.5 nm, the coherent interfaces were more effective barriers to dislocation initiation and transfer than the incoherent ones. [ABSTRACT FROM AUTHOR]

The design of thin-walled structures is commonly based on the solutions of linear boundary-value problems, formulated within well-developed theories for elastic plates and shells. However, in modern appliances, especially in MEMS design, it is necessary to take into account non-linear mechanical effects that become decisive for flexible elements. Among the substantial non-linear effects that significantly change the deformation properties of thin plates are the effects of residual stresses caused by the incompatibility of deformations, which inevitably arise during the manufacture of ultrathin elements. The development of new methods of mathematical modeling of residual stresses and incompatible finite deformations in plates is the subject of this paper. To this end, the local unloading hypothesis is used. This makes it possible to define smooth fields of local deformations (inverse implant field) for the mathematical formalization of incompatibility. The main outcomes are field equations, natural boundary conditions and conservation laws, derived from the least action principle and variational symmetries taking account of the implant field. The derivations are carried out in the framework of elasticity theory for simple materials and, in addition, within Cosserat's theory of a two-dimensional continuum. As illustrative examples, the distributions of incompatible deformations in a circular plate are considered. [ABSTRACT FROM AUTHOR]

In this paper, the experimental methodology for the single-crystal circular plate deformation measurement and subsequent procedure for the quantitation of its mechanical properties are developed. The procedure is based on a new numerical-analytical solution of non-linear boundary-value problem for finite deformations of a circular anisotropic plate. Using the developed method, a study of the deformation of single-crystal circular plates formed on the basis of a silicon-on-insulator structure was carried out. The values of residual stresses are determined and it is shown that the presence of these stresses increases the flexural rigidity of the plate by several times. [ABSTRACT FROM AUTHOR]

When the dissimilar metal composite plate accumulates inconsistent deformation to a certain degree during the heat treatment process, it indicates bad plate morphology such as warpage. Therefore, it is crucial to explore the mechanism of coordinated deformation between layers under thermal–mechanical coupling during heat treatment. This study investigates the interlayer coordinated deformation mechanism of the stainless-steel clad plate (304/Q235 stainless-steel clad plate) under thermal–mechanical coupling by using three heat treatment methods: rapid cooling process, rapid cooling in the high-temperature stage + slow cooling in the low-temperature stage, and rapid cooling + tempering process. And this study enlightens that the temperature field distribution and the longitudinal stress–strain distribution are obtained by using the Abaqus software. The effects of different tensile and thickness ratios on the residual stress are analyzed. The final experiment found that the maximum longitudinal stress and plastic strain appear on the upper and lower surfaces during heat treatment. The rapid cooling heat treatment process has light warpage and good shape. When the thickness ratio of the composite plate is 1:4, the warpage is the lightest. The increase of set tension will increase the compressive stress value in the residual stress. In contrast, the tensile stress value will decrease. [ABSTRACT FROM AUTHOR]

Copyright of Revista Foco (Interdisciplinary Studies Journal) is the property of Revista Foco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article considers the deformation behavior of Panda optical fiber using different models of material behavior for the tasks of predicting residual stresses after drawing when cooling from 2000 °C to room temperature (23 °C) and indenting the fiber into an aluminum half-space at different parameters. These studies were conducted for single- and double-layer protective coatings (PCs), at different values of external load and thickness of single-layer PC. This paper determined the fields of residual stresses in the fiber formed during the drawing process. They are taken into account in modeling the fiber performance in the further process of this research. This article investigated two variants of PC behavior. The influence of behavior models and the number of covering layers on the deformation of the "fiber-half-space" system was analyzed. This paper establishes qualitative and quantitative regularities of the influence of the external load magnitude and relaxation properties of PCs on the deformation and optical characteristics of Panda optical fiber. [ABSTRACT FROM AUTHOR]

A state-of-the-art review was delivered in the manuscript to analyze the current situations and the advantages/disadvantages of resilient deformation related issues to the unbound granular material (UGM), including testing methods, influencing factors and constitutive models, through which the bottlenecks in UGM resilient deformation characterizations were located and new theories and future research recommendations were proposed. Compared with other testing methods, the hollow cylinder test and true triaxial test are the only two to determine the anisotropic moduli of the UGM. Although significant advantages are observed in more advanced test apparatus such as true triaxial test, further improvements should be made, such as more advanced process identification control algorithm, to more conveniently control the nine independent hydraulic system and accurately measure UGM anisotropic properties. Confusions and conflicts in understanding the influencing factors to UGM resilient modulus were located, such as the stress history, the residual stress, the dry density, the gradation/fine content and the freeze-thaw cycle, based on which future research could be conducted. Through reviewing evolutions of the UGM constitutive models and comparing their representativeness and complexity comprehensively, major drawbacks were discovered and a new theory was proposed afterward to modify the UGM constitutive model, although further validations are still needed. [ABSTRACT FROM AUTHOR]

Few studies have focused on the combined effects of ambient thermal and vehicle loads on the long-term deformation of prestressed concrete bridges. Based on preliminary work, a method for establishing the equivalence of random ambient temperature loads is proposed here. With this method, the temperature distributions of bridges under random weather conditions can be obtained. Subsequently, a concrete creep model considering cyclic thermal and vehicle loads is established. Finally, an analysis method for establishing the long-term deformation of prestressed concrete bridges under ambient thermal and vehicle loads is proposed. This was applied to the example of a prestressed concrete bridge; the meteorological parameters around the bridge were collected, and the equivalent environmental thermal loads were obtained. It was found that higher temperatures made the coupled effect of thermal and vehicle loads more obvious, leading to faster deformation. The long-term deformation of a continuous beam was found to be related to the residual stress after sunshine. The long-term deformation can be affected by the temperature-distribution mode, but the random properties of weather have almost no notable effect. The temperature difference between the inner and outer surfaces of the web and the prestress loss are the main reasons for the cracking of the inner surface of the web. [ABSTRACT FROM AUTHOR]

Due to its extremely high optical uniformity and excellent hot stability, glass–ceramic serves as a key material for ultraprecision imaging of lithography lens, and low‐deformation machining is of significance for achieving high‐quality surface. Aiming at controllable processing, the annealing of different nanoscratches on glass–ceramic was investigated for revealing the mechanism of material removal and damage repair. The volume change of the single‐pass nanoscratch under various normal loads and sliding velocities before and after the annealing was calculated for quantifying the contribution of shear flow, densification, and residual stress to the material removal, respectively. It is found that ductile removal under high normal load or low sliding velocity is dominated by shear flow, thereby improving removal efficiency and reducing machining deformation and defects caused by densification and residual stress. The changes of microstructures beneath the scratches before and after annealing further reveal that the excess processing energy will be absorbed in glass–crystal interface and form micro‐cracks on crystal surface. For comparison, brittle removal under variable cycles was simulated by multi‐pass nanoscratches, and it reveals that the shear flow ratio raises gradually with the increase of cycle number. These findings provide theoretical guidance for ultraprecision processing of glass–ceramic surfaces. [ABSTRACT FROM AUTHOR]

Surface residual stress is made on the aero-engine blades by shot peening to improve the fatigue life of the blades. As the service time increases, the surface residual stress is decreasing due to thermomechanical relaxation and the centrifugal load caused by high-speed rotation. Therefore, the surface residual stress detection is of great importance for predicting the remaining life of aero-engine blades. Up to now, efficient and non-contact detection of surface residual stress is still a challenge. In this paper, an active thermal deformation excitation (ATDE) method for surface residual stress is proposed. According to the thermal deformation theory, the thermal deformation of the material is positively correlated with the surface residual stress, and by measuring the thermal deformation the surface residual stress can be detected and evaluated. The theoretical deformation model was established, and simulation models with different surface residual stresses were constructed. A detection system was proposed to detect the blade deformation with different surface residual stresses. Results show that there was a linear relationship between the blade deformation and the surface residual stress from −636 Mpa to −1403 Mpa. [ABSTRACT FROM AUTHOR]

The current paper focuses on the prediction of residual stresses and distortions in the Laser Powder Bed Fusion (LPBF) built Ti6Al4V thin-walled geometries using Ansys Additive Print (AAP) software which employs a layer-by-layer accumulation of inherent strain to calculate the deformations. Isotropic and anisotropic strain scaling factors were calibrated initially within the APP software for the Ti6Al4V based single cantilever beam geometry. Subsequently, the numerical simulations were performed in APP software and computed the residual stresses and distortions for the varied process parameters including laser power, scan speed and hatch distance while maintaining the layer thickness constant for all the design iterations. The numerical predictions were compared; they were found to match reasonably well with the XRD measurements within the calibrated regime. [ABSTRACT FROM AUTHOR]

The expansion process of the base pipe of the expanded screen pipe includes large displacement elastic-plastic deformation problems such as geometric nonlinearity, material nonlinearity and contact nonlinearity. In this paper, based on the elastic-plastic deformation mechanism of the base pipe of expanded screen pipe, finite element equations are established and numerical simulation is used to construct a finite element simulation model to study the mechanical behavior and deformation law of F203.2 mm base pipe of the expanded screen pipe expansion process. The results show that the expansion rate has no effect on the increase of wall thickness, and the decrease is proportional to the expansion rate. The greater the expansion rate, the greater the residual stress at both ends of the slot. [ABSTRACT FROM AUTHOR]

Large-scale, high-strength aluminum alloy forgings are essential components in the aerospace industry, with benefits including increasing strength and decreasing weight. Accurate shape-property control is the secret to forging quality. This study uses the alloy 7050 to experimentally evaluate the parametric influence of cold compression on residual stress and mechanical characteristics. The evolutions of mechanical properties, microstructure and residual stress are theoretically studied using various cold compression strains from 1% to 5% on an equivalent part, of which the results are further applied on a complicated rib-structured die forging. It is demonstrated that increasing the compression strain reduces the tensile strength of the material, but has little impact on conductivity and fracture toughness. According to the TEM results, compression also encourages the precipitation and growth of precipitated phases, particularly in positions with high dislocation densities after aging. Cold compression significantly reduces residual stress; nevertheless, as compression strain increases, residual stress first decreases and then increases. With the use of rib-structured forging, it is observed that the compression strain for 7050 aluminum alloy ranges from 2% to 4%, and the combined pressing method of the rib and web improves the uniformity of residual stress. [ABSTRACT FROM AUTHOR]

The current work investigates the auxetic tensile deformation behavior of the inversehoneycomb structure with 5 × 5 cells made of biodegradable poly(butylene adipate-coterephthalate) (PBAT). Fused deposition modeling, an additive manufacturing method, was used to produce such specimens. Residual stress (RS) and warpage, more or less, always exist in such specimens due to their layer-by-layer fabrication, i.e., repeated heating and cooling. The RS influences the auxetic deformation behavior, but its measurement is challenging due to its very fine structure. Instead, the finite-element (FE)-based process simulation realized using an ABAQUS plug-in numerically predicts the RS and warpage. The predicted warpage shows a negligibly slight deviation compared to the design topology. This process simulation also provides the temperature evolution of a small-volume material, revealing the effects of local cyclic heating and cooling. The achieved RS serves as the initial condition for the FE model used to investigate the auxetic tensile behavior. With the outcomes from FE calculation without consideration of the RS, the effect of the RS on the deformation behavior is discussed for the global force–displacement curve, the structural Poisson's ratio evolution, the deformed structural status, the stress distribution, and the evolution, where the first three and the warpage are also compared with the experimental results. Furthermore, the FE simulation can easily provide the global stress–strain flow curve with the total stress calculated from the elemental stresses. [ABSTRACT FROM AUTHOR]

Potential for a rapid hybrid additive/subtractive manufacturing technique capable of generating large aluminum components with deep geometrical features exists if, for example, layers of aluminum plates can be deposited and held in place using friction stir welding followed by machining. However, when plates of aluminum are friction stir spot welded together, adjacent material can deform causing a gap between layers. This research investigates how friction stir tool geometry affects the formation of interlayer gaps and the lap shear strength of the weld. For this purpose, residual stresses and microhardness were measured to characterize the weld formation process. While friction stir welding of 6061 aluminum bar stock was carried out on a machining center with three different pin diameters (5.7, 6.4, 7.0 mm) and two pin lengths (8.9, 10.2 mm). In general, outcomes of the research show that lap shear strength trends upward with increasing pin diameter but does not show a strong relation to the pin length. Interlayer gap size increases with pin length, but does not show a clear trend with pin diameter. Compressive residual stresses were observed on the weld shoulder with no significant variations occurring among the studied stir tool geometries. No significant change was measured in microhardness values when the pin length or shoulder diameter were changed, suggesting that the increase in lap shear strength is due to a change in weld cross-section instead of a material property change. This research will guide friction stir tool geometry selection for this hybrid manufacturing process and can be applied more broadly to any application where material deformation around a weld is undesirable. [ABSTRACT FROM AUTHOR]

One factor that plays an important role in the aerodynamic performance of aeroengines is the shape of the blades, which is vulnerable to change resulting from the plastic deformation and the residual stresses induced by the complex manufacturing processes, especially the shot peening. However, few studies were focused on the detailed strategies of shot peening on the complex profile and the superposition effects of residual stresses during the entire manufacturing processes. In this paper, based on the concept of eigenstrains, we investigated the effect of shot peening on residual stresses and deformation of the blade by combining the experimental measurement and the local-global simulation. The results show that the initial residual stresses induced by the previous milling process could be neglected. After the shot peening, the blade has the largest deformation if considering the initial residual stresses during milling with large amount of material removal, compared with the case without considering initial residual stresses and the case considering initial residual stresses after dynamic milling of blades. Furthermore, the in-out sequence of shot peening results in the smallest deformation and the pre-deformation of the blade can effectively offset this deformation. Finally, the shot peening intensity should not be too high in practical blade manufacturing for small thickness in order to avoid compromising the reliability and safety of blades. [ABSTRACT FROM AUTHOR]

To improve the stretch-bend forming precision of aluminum alloy profiles with complex open sections, the relationship stressestrain distribution and the spring-back radius variation were analyzed under different stretch-bend stages. Numerical simulation was performed on the auxiliary mold stretch-bend and spring-back process for the L-section aluminum alloy profile with variable curvature. The effects of cover plate pressure and baffle gap on residual stress, section deformation and spring-back value after forming were investigated. The results show that the stretch-bend warpage can be avoided by setting the cover plate on the straight section of the profile web plate. With the increase of the cover plate pressure, the section distortion of the vertical plate increases by 82%, and the maximum spring-back increases by 71%. A baffle plate was added to the outside of the vertical plate, and the baffle gap is proportional to the amount of section distortion and inversely proportional to the spring-back value. The critical cover force (1 kN) and the critical baffle gap (1 mm) obtained by numerical analysis are used in the stretch-bend forming experiment, and the maximum error between the two results is 2.39%. The numerical simulation has a certain reference value for the rational design of the auxiliary mold stretch-bend process parameters. [ABSTRACT FROM AUTHOR]

The present article establishes a fundamental correlation between surface integrity characteristics of the finished surface with the normal to tangential force ratio (Fn/Ft) in the grinding of Ti-6Al-4V. The subsurface deformation, crystallographic texture, surface redeposition, and residual stress were studied in the surface integrity characteristics. The XRD result indicated deformation-induced texturing of the α-002 basal plane of Ti-6Al-4V. The gradual reduction in texturing along the depth was confirmed by the Gi-XRD investigation. The relative intensity of the 002 peak was utilized as a quantitative indicator of subsurface deformation. The XRD and the metallographic study revealed a considerable amount of subsurface deformation at a higher grinding speed (vs) and an enhanced material removal rate (MRR). Intense surface redeposition was also observed for higher vs and increased MRR grinding conditions. The surface redeposition was identified as an influencing factor that escalates the subsurface deformation and crystallographic texture. In addition, the residual stress was found to be more compressive at enhanced vs and MRR. Further, a higher force ratio Fn/Ft was noticed for the grinding conditions that revealed significant subsurface deformation, strong crystallographic texture, surface redeposition, and more compressive residual stress. Eventually, a correlation was found between the force ratio Fn/Ft and all these surface integrity characteristics. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aluminum alloys are widely used in aerospace products because of their high specific stiffness and high specific strength. In the machining process of thin-walled aluminum ring workpieces, with the removal of materials, the stiffness of the parts decreases and the residual stress (RS) is released, resulting in obvious machining deformation (MD) of workpieces. Taking the typical 2219 aluminum alloy rolled ring as the research object, a new theoretical analysis model and a finite element model coupled with multi-physics and multi-processing are established to analyze the initial residual stress (IRS) distribution and the MD law. The accuracy of simulation prediction results regarding IRS and MD is verified by experiments, while the equivalent theoretical analytical model qualitatively explains the MD of the ring due to IRS. The IRS of the rolled ring is about 40 ~ 80 MPa, which induces a maximum MD of 0.4016 mm (from 89.9985 to 90.4001 mm) and an elliptical cross-section. The relative error of the MD result is 23.92%, while the ellipticity is only 11.30%. [ABSTRACT FROM AUTHOR]

Welding deformation occurs due to non-uniform thermal expansion, thermal contraction, restraint, and phase transformation in a metal by a local welding heat source. This causes problems such as low buckling strength and the reduced workability of the production process. Correcting welding deformations in stainless steel using heat—such as by linear heating—causes metal sensitization, which should be avoided. Herein, welding deformation was reduced by applying tension stress instead of correcting the deformation by heating. A deformation-prevention jig was used to reduce welding deformation during the manufacturing of a cylinder made of STS304 by laser welding. The tensile stress was induced by pushing the cylinder shell outward using the deformation-prevention jig. A thermo-elastoplastic analysis was performed to investigate the effects of the magnitude of the tensile stress on welding deformation. Furthermore, the parametric results—which indicated a reduction in welding deformation—were verified through experiments. The thermo-elastoplastic analysis suggested that deformation did not occur when the magnitude of tensile stress was approximately 50% of the yield stress of the base metal. Moreover, the deformation was experimentally reduced by 11–20% when a tensile stress of 30 MPa was applied to the cylinder, compared with that in the absence of tensile stress. [ABSTRACT FROM AUTHOR]

Warping and dross formation are the main defects of an overhang structure formed by laser powder bed fusion. In order to study these defects, a seven−shaped overhang structure with different lengths and heights of the overhang was printed. The influence of the temperature and stress field on the overhang structure was investigated using a 3D finite element (FE) model. The results of the simulation showed that the molten pool in the powder support zone was much larger than the molten pool in the solid support zone. The molten pool sank due to the actions of gravity and the capillary force. This led to the powder melting, which then formed a droplet−like dross formation on the lower surface. The temperature difference between the regions led to a large residual stress. When the residual stress exceeded the material strength, warping deformation occurred in the top area, affecting the subsequent powder−laying process. The warping zone was remelted when the next layer was processed. As the number of forming layers increased, the thermal conductivity and stiffness increased continuously, and the deformation of the top area gradually decreased. The experiment results showed that the longer the overhanging length was, the more serious the warpage was. When the overhanging length was below 3 mm, the warping of the top area continued to decrease to zero as the building process proceeded. Meanwhile, the dross formation appeared at the bottom of the overhanging area in all experimental groups. Studying the process of warping and dross formation was helpful to understand the defect change process in the manufacturing process of an overhang structure. [ABSTRACT FROM AUTHOR]

In this paper, the effects of material removal strategies and initial stress states on the machining deformation of aluminum alloy plates were investigated through a combination of finite element simulation and experiments. We developed different machining strategies described by Tm+Bn, which removal m mm materials form top and n mm materials from the bottom of the plate. The results demonstrate that the maximum deformation of structural components with the T10+B0 machining strategy could reach 1.94 mm, whereas with the T3+B7 machining strategy was only 0.065 mm, decreasing by more than 95%. The asymmetric initial stress state had a significant impact on the machining deformation of the thick plate. The machined deformation of thick plates increased with the increase in the initial stress state. The concavity of the thick plates changed with the T3+B7 machining strategy due to the asymmetry of the stress level. The deformation of frame parts was smaller when the frame opening was facing the high-stress level surface during machining than when it was facing the low-stress level. Moreover, the modeling results for the stress state and machining deformation were accurate and in good accordance with the experimental findings. [ABSTRACT FROM AUTHOR]

To overcome warping in thin bamboo bundle veneer laminated composites (TBLC), their hydrothermal deformation characteristics were systematically investigated in this study. It was found that TBLCs accelerated the release of internal stress in the thickness direction in a hydrothermal environment, which increased their warpage. TBLCs showed increased warpage in the width and diagonal directions upon increasing the temperature. The warpage of Type E increased by 155.88% and 66.67% in the width and diagonal directions, respectively, when the temperature increased from 25°C to 100°C. The symmetrical TBLC with cross-lay-up and odd layers displayed better hydrothermal stability. We revealed that the deformation of the TBLCs could be regulated under the synergistic effect of water and temperature. These results provide a scientific basis for improving the uniformity of bamboo bundle composite materials and for developing thin bamboo bundle fiber composite materials with designable structures and controllable performance. [ABSTRACT FROM AUTHOR]

Considering the effect of different moulding processes, this paper studies the curing deformation of laminated composites of stiffened panel structures. The curing deformation is assessed after the stiffened panel structures of carbon fiber/epoxy resin composites are created through vacuum bag pressing process by co-curing, co-bonding, and secondary bonding and curing. For different moulding processes, by using an instantaneous linear elastic curing constitutive model and taking residual curing stresses as pre-stress, a finite element simulation method considering different curing methods is proposed, and is also compared and verified with the experimental results. The influences of factors such as moulding processes, layup methods and stiffener thickness on the curing deformation of the stiffened panel structures are analyzed. The results show that moulding processes, layup and stiffener thickness have a great influence on the curing deformation of the structures. The deformation of composite stiffened panel structures decreases considerably by increasing stiffener thickness and adopting an appropriate moulding process through a reasonable layup. [ABSTRACT FROM AUTHOR]

Storage canisters used in nuclear power plants operating in seaside areas—where the salt content in the atmosphere is high—may be susceptible to chloride-induced stress corrosion cracking (CISCC). Chloride-induced stress corrosion cracking is one of the ways in which dry storage canisters made of stainless steel can degrade. Stress corrosion cracking depends on the microstructure and residual stress, and it is therefore very important to improve the surface properties of materials. Laser shock peening both greatly deforms the material surface and refines grains, and it generates compressive residual stress in the deep part from the surface of the material. This study focused on the effect of laser shock peening on the stress corrosion cracking of 304L stainless steel. The laser shock peening was found to induce compressive residual stress from the surface to a 1 mm depth, and the SCC properties were evaluated by a U-bend test. The results showed that the SCC resistance of laser-peened 304L stainless steel in a chloride environment was enhanced, and that it was closely related to grain size, the pitting potential of the cross section, and residual stress. [ABSTRACT FROM AUTHOR]

In this study, the formation and evolution mechanism of residual stress in the process of solution heat treatment of a 316L/Q235B composite plate and the influence law of different factors on residual stress were analyzed by combining experiments and simulation. The results showed that the bending stress caused by interlayer thermal stress was the main factor that formed residual stress in the process of solution heat treatment of a 316L/Q235B composite plate. Tensile load was helpful to reduce the bending deformation of the composite plate during heat treatment, and ultimately improve the uniformity of residual stress distribution in the composite plate. With the increase in the total thickness, the interlayer thermal stress and bending stress between layers increased, and the primary and secondary relationship between them and residual stress was related to the specific thickness. The composite ratio had a great influence on the distribution of residual stress. When the composite ratio increased, the interlayer thermal stress between layers of the base layer increased, while that of the cladding layer decreased. At the same time, the bending stress increased with the increase in the composite ratio, and then affected the residual stress distribution. [ABSTRACT FROM AUTHOR]

Carbonaceous slate inevitably possesses microscopic pores, microcracks, cleavages, and bedding planes in complex geoenvironment during the diagenesis processes. The microstructure of carbonaceous slate changes apparently under the effects of underground water infiltration, tectonic stress, and engineering disturbance, which induces the large deformation of rock mass and influences the stability of geotechnical engineering projects. To investigate the microstructure characteristics and reveal deformation mechanisms of carbonaceous slate under the influence of water pressure and stress, the variations of the pore size distribution(PSD), connectivity of pores, and porosity of samples during water injection and triaxial compression were studied using multiple methods. The results indicated that voids include plate-like micropores and microcracks, which are discontinuous without external stress. The micropores with a size of less than 1 μm dominate in number. The flaky particles were extruded and bent at a confining pressure, which caused the intermediate pores to form and altered the PSD of the samples. Hence, the connectivity dramatically improved and resulted in increased permeability. Water with dissolved clay minerals and small particles could move between micropores and microcracks during the water injection process. The elastic deformation of the particles recovered, and the intermediate pores disappeared when the imbalanced forces on two sides of the particles were narrowed. Pore water pressure affected the effective stress state and decreased the cohesion and stiffness of the rock. In the lower stress state, the porosity had a certain range of decrease (about 0.2%) mainly due to micropore compression, while the microcrack sprouted and expanded with the increase of compressive stress, resulting in the extension of porosity. The interaction of the stress and water seepage on the slate reduced the rock strength and favored the deformation, leading to a large macrodeformation of the soft rock in the long run. [ABSTRACT FROM AUTHOR]

Cu-Ni-Si alloy is the key raw material for the lead frame of large integrated circuits. The disordered grain orientation of alloy billet, high hardening rate, residual stress, and poor surface quality of cold working strips seriously affect its processability. In order to improve the cold-working properties of Cu-Ni-Si alloy, two kinds of C70250 copper alloy strips were produced through hot mold continuous casting (HMCC) and cold mold continuous casting (CMCC) technology. The effects of solidified microstructure on the cold-working deformation behavior, mechanical properties, and residual stress of the alloy were studied. The results show that C70250 copper alloys with columnar grain and equiaxed grain were prepared through HMCC and CMCC. After a 98% reduction in cold rolling, columnar grain strip surface quality was very good, and the elongation was still as high as 3.2%, which is 2.9 times that of equiaxed grain alloy. The residual stress of equiaxed grain strips reached 363 MPa, which is 2.7 times that of columnar grain strips. During the cold rolling process, equiaxed grain strips are prone to cause intersecting plane dislocations, stacking faults, shear bands, and grain breakage during large deformation cold rolling. The columnar grain strip causes parallel plane dislocations, stacking faults, and shearbands. Furthermore, the deformation structure was found to be uniform, and, ultimately, the alloy formed a fibrous structure. Therefore, the elongation and latter distortion of columnar grain strips improved after being put through large deformation cold rolling, which greatly reduced residual stress. [ABSTRACT FROM AUTHOR]

A continuum theoretical model for describing nanotube formation from a self-bending (self-curling) nanofilm driven by surface stress was established in this paper. Surface stress, surface elasticity and anisotropic deformation were considered. A nanofilm was cured along tangential direction to form a nanotube. The other in-plane direction (cylindrical direction) maintains straight state. Isotropic surface stress no longer induces an isotropic bent under this condition. Therefore, isotropic Stoney theory should be modified and the anisotropic deformation should be reckoned in. Curling structure affects radius as well as elongation strain of nanotubes obviously. Film stiffness instead of biaxial modulus in the curling equation means the difference between our theory and Stoney formula (as well as its modified form). If surface elasticity is balance, elongation strain holds isotropic despite the anisotropic curling structure of nanotubes. Since residual strain and stress influence the physical properties within nanotube wall, the residual strain and stress were also analyzed in this paper. [ABSTRACT FROM AUTHOR]

A phase field framework of elasticity, inelasticity, and fracture mechanics is invoked to study the behavior of ceramic materials. Mechanisms addressed by phase field theory include deformation twinning, dislocation slip, amorphization, and anisotropic cleavage fracture. Failure along grain and phase boundaries is resolved explicitly, whereWeibull statistics are used to characterize the surface energies of such boundaries. Residual stress incurred by mismatching coefficients of thermal expansion among phases is included. Polycrystalline materials of interest are the ultra-hard ceramics boron carbide (B4C) and boron carbide-titanium diboride (B4C-TiB2), the latter a dual-phase composite. Recent advancements in processing technology enable the production of these materials via spark-plasma sintering (SPS) at nearly full theoretical density. Numerical simulations invoking biaxial loading (e.g., pure shear) demonstrate how properties and mechanisms at the scale of the microstructure influence overall strength and ductility. In agreement with experimental inferences, simulations show that plasticity is more prevalent in the TiB2 phase of the composite and reduces the tendency for transgranular fracture. The composite demonstrates greater overall strength and ductility than monolithic B4C in both simulations and experiments. Toughening of the more brittle B4C phase from residual stress, in addition to crack mitigation from the stronger and more ductile TiB2 phase are deemed advantageous attributes of the composite. [ABSTRACT FROM AUTHOR]

Continuous efforts are being made to improve the technology and the process involved in part production to meet the demands of society. Advancements in machining, as well as incremental forming, resulted in the generation of a technology that is capable of manufacturing monolithic components in a single setup. Such hybrid technological development, called deformation machining (DM), has the milling process contributing to thin structure generation and single point incremental forming (SPIF) leading to the desired geometrical deformation. Machining a material block to produce thin structure results in unwanted residual stresses in the workpiece, which hinders the part's formability during SPIF. In the current research, stress-relieve annealing of aluminum alloy (Al 6061) is done to compensate for these residual stresses. While doing so, the optimum temperature of reheating is identified, at which the strength of the selected material is not significantly compromised. For this, preliminary microstructural investigations are carried out on the machined components at different temperatures, followed by experimental investigations. The force measurement of different samples was done during the experiments for determining the effects of heat treatment. Geometrical observations suggest that heat treatment results in better forming depth and improved forming angle, however, an increase in surface roughness is observed on the heat-treated parts. [ABSTRACT FROM AUTHOR]

• Deformation characteristics of narrow crack under low compressive stress are investigated. • Influences of unidirectional loading on narrow crack deformation and initiation are discussed. • Different deformation modes and initiation angle at two crack tips are investigated. • Coupled effects of strain rate and inclination angle on narrow crack initiation are investigated. • Coupled effects of strain rate and inclination angle on mechanical properties are investigated. Uniaxial compression tests were carried out on rock-like specimens containing prefabricated narrow crack under various strain rates. Experimental observations and numerical results show that narrow crack will close or partially close or expand under low compressive stress. Due to the unidirectional loading of loading device, the deformation degree of crack tip near the loading end was different with that of crack tip near the bearing end. With the increase of strain rate, the cracking modes can be divided into 3 categories, near vertical splitting failure affected by horizontal crack (α = 0°), anti-N-wing crack (15°≤ α ≤ 60°) and wing crack (60°< α ≤ 90°). Both of the initiation angle θ 1 of crack tip near the loading end and θ 2 of crack tip near the bearing end decreased with the increase of α and strain rate. Specially, when α = 90°, both θ 1 and θ 2 rose with the increase of strain rate. Moreover, the value of θ 2 was greater than that of θ 1 under the same α value because of the different deformation characteristics at two tips. Besides, the mechanical properties of fissured rock including peak compressive stress, residual compressive stress, strain at peak stress, elastic modulus and post-peak softening modulus were significantly influenced by the strain rate and inclination angles. [ABSTRACT FROM AUTHOR]

• The effect of clamping deformation on the material removal amount and cyclic material removal process on the residual stress are determined. • Energy equations under three-dimensional non-uniform residual stress field are established. • Excellent agreements of the machined surface shapes are obtained for predicted and experimental results. • The influence of cutting parameters and strategies on machining deformation is anlyzed. • The evolution of machining deformation in process is investigated. Workpiece deformation under the coupling effect of clamping force, initial residual stress (IRS), and machining residual stress (MRS) is an essential concern in the manufacturing of thin-walled metallic parts. Prediction of machining deformations is critical for ensuring machining quality and has significant guiding implications for producing thin-walled parts. However, most research has been focused on calculating machining deformation caused by a single factor. Based on the energy principle, the effect of clamping deformation on the material removal amount and the effect of the cyclic material removal process on both IRS and MRS are analyzed. To predict the machining deformation of circular metallic plates, energy functions under the three-dimensional non-uniform residual stress field consider the coupling effect of multiple factors, which is established and solved by the Rayleigh-Ritz method. This analysis elucidates the formation mechanism of machining deformation under the single-factor effects of IRS and MRS as well as the coupling effect of clamping force and residual stress. In this article, an analytical prediction model with a prediction error of around 8.5% is established for machining deformation under the coupling effect. Additionally, leveraging the quantitative results of the proposed model, the impacts of cutting parameters and strategies on machining deformation, as well as the evolution of machining deformation throughout the entire material removal process are elicited. [ABSTRACT FROM AUTHOR]

Precise control of machining deformation is crucial for improving the manufacturing quality of structural aerospace components. In the machining process, different batches of blanks have different residual stress distributions, which pose a significant challenge to machining deformation control. In this study, a reinforcement learning method for machining deformation control based on a meta-invariant feature space was developed. The proposed method uses a reinforcement-learning model to dynamically control the machining process by monitoring the deformation force. Moreover, combined with a meta-invariant feature space, the proposed method learns the internal relationship of the deformation control approaches under different stress distributions to achieve the machining deformation control of different batches of blanks. Finally, the experimental results show that the proposed method achieves better deformation control than the two existing benchmarking methods. [ABSTRACT FROM AUTHOR]

In this paper, new suspended-membrane double-ohmic-contact RF-MEMS switch configurations are proposed. Double-diagonal (DDG) beam suspensions, with either two or three anchoring points, are designed and optimized to minimize membrane deformation due to residual fabrication stresses, thus exhibiting smaller mechanical deformation and a higher stiffness with more release force than previously designed single diagonal beam suspensions. The two-anchor DDGs are designed in two different orientations, in-line and 90°-rotated. The membrane may include a window to minimize the coupling to the lower electrode. The devices are integrated in a coplanar-waveguide transmission structure and fabricated using an eight-mask surface-micro-machining process on high-resistivity silicon, with dielectric-free actuation electrodes, and including glass protective caps. The RF-MEMS switch behavior is assessed from measurements of the device S parameters in ON and OFF states. The fabricated devices feature a measured pull-in voltage of 76.5 V/60 V for the windowed/not-windowed two-anchor DDG membranes, and 54 V/49.5 V for the windowed/not-windowed three-anchor DDG membranes, with a good agreement with mechanical 3D simulations. The measured ON-state insertion loss is better than 0.7 dB/0.8 dB and the isolation in the OFF state is better than 40 dB/31 dB up to 20 GHz for the in-line/90°-rotated devices, also in good agreement with 2.5D electromagnetic simulations. [ABSTRACT FROM AUTHOR]

Weak stiffness components were sensitive to the stress, and it was hard to guarantee the flatness after machining. To solve this problem, A MRF process was proposed to improve the flatness. The deformation mechanism of the components was clarified, and the residual stress relaxation was considered as the main cause of the deformations, which was predicted by an established model. The simulation results show that the deformations are about 9.5 µm by single-side machining, while the deformations are about 0.7 µm by turning over machining. Thus, the machining strategy by turning over was proposed based on the simulation deformation results. Experiments were conducted to verify the simulation. The results reveal that serious deformations happen by single-side machining, while the deformations recover by turning over machining, and the flatness converged efficiently. By the turning over machining strategy, the flatness peak and valley(PV) value reduce from 4.6 µm and 5.9 µm to 2.0 µm respectively on a ф 200 x 2 mm weak stiffness flat component of copper. [ABSTRACT FROM AUTHOR]

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A number of manufacturing processes are able to plastically deform the work material and induce residual stresses in different ways, thus affecting the component surface integrity and, consequently, its ability to withstand cyclic loads. Besides the nature of the process, the parameters employed also have a significant influence on the fatigue strength. This work investigates the influence of the turning parameters and deep rolling on the surface roughness, fatigue life, and fatigue fracture of hardened AISI 4140 steel. Fatigue specimens were turned under various cutting speeds, feeds, and depths of cut and further subjected to deep rolling under a constant condition. The results indicated that deep rolling was able to reduce all the roughness amplitude parameters investigated. Regarding the fatigue life of the turned specimens, there was a combined influence of feed and depth of cut, i.e., for the lower feed (0.2 mm/rev), an increase in depth of cut from 0.5 to 1.0 mm promoted an increase in fatigue life; however, the opposite occurred for the higher feed value (0.3 mm/rev). This behavior was more pronounced at higher cutting speeds. Deep rolling increased the fatigue life of the specimens, but a higher number of cycles were applied before the fracture of the specimens turned using the higher feed value, thus suggesting that deep rolling is not be able to completely eliminate the influence of previous turning on the surface integrity. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review on the types of machining deformation and mechanism analysis, as well as the machining deformation control methods of aero-engine thin-walled casings. The different types of machining deformation (e.g. deformation caused by positioning and clamping process, cutting forces, residual stress, and chatter) of thin-walled casings are introduced, and the corresponding deformation mechanism of each type is discussed in the first part. Subsequently, the research progress and academic achievements are summarised in terms of the prediction and control of cutting deformation, dynamic modelling and chatter suppression, and adaptive machining and error control in the field of machining deformation control of thin-walled casings. Then, the specific machining deformation control methods, including cutting force prediction, reduction of residual stress, dynamics modelling, chatter suppression, adaptive machining, and error compensation, are explored in detail. Finally, this review implies the existing challenges and future developing tendencies to control the machining deformation of thin-walled casings. [ABSTRACT FROM AUTHOR]