Accumulation Of Residual Stresses Research Articles

Elasto-plastic residual stress analysis of selective laser sintered porous materials based on 3D-multilayer thermo-structural phase-field simulations

Residual stress and plastic strain in additive manufactured materials can exhibit significant microscopic variation at the powder scale, profoundly influencing the overall properties of printed components. This variation depends on processing parameters and stems from multiple factors, including differences in powder bed morphology, non-uniform thermo-structural profiles, and inter-layer fusion. In this research, we propose a powder-resolved multilayer multiphysics simulation scheme tailored for porous materials through the process of selective laser sintering. This approach seamlessly integrates finite element method (FEM) based non-isothermal phase-field simulation with thermo-elasto-plastic simulation, incorporating temperature- and phase-dependent material properties. The outcome of this investigation includes a detailed depiction of the mesoscopic evolution of stress and plastic strain within a transient thermo-structure, evaluated across a spectrum of beam power and scan speed parameters. Simulation results further reveal the underlying mechanisms. For instance, stress concentration primarily occurs at the necking region of partially melted particles and the junctions between different layers, resulting in the accumulation of plastic strain and residual stress, ultimately leading to structural distortion in the materials. Based on the simulation data, phenomenological relation regarding porosity/densification control by the beam energy input was examined along with the comparison to experimental results. Regression models were also proposed to describe the dependency of the residual stress and the plastic strain on the beam energy input.

Coupling structural, chemical composition and stress fluctuations with relaxation dynamics in metallic glasses

Understanding the atomistic mechanisms of relaxation dynamics in metallic glasses remains a longstanding challenge. Here, using microsecond time scale molecular dynamics simulations, three main relaxation stages in metallic glasses are identified. At about 0.6Tg, chemical composition plays a dominant role in the relaxation, manifested by stress accumulation and only minimal variations in structure. As Tg approaches, the confluence of structural heterogeneity and chemical composition leads to the decoupling of relaxation mechanisms. At this temperature, the relaxation results in a structure with a lower energy state and a lower level of stress. In the supercooled liquid regime, an extensive increase in the number of closed-packed icosahedral clusters is responsible for accelerated structural relaxation while their packing frustration leads to the accumulation of intrinsic residual stresses in the glass. The atomistic origin of these dynamic relaxation modes is discussed in terms of structural, chemical composition and stress variations.

Thermomechanical Analysis and Numerical Simulations of Fused Filament Fabricated Polylactic Acid Parts

This work aimed to investigate the thermal deformation of polylactic acid (PLA) samples 3D-printed by Fused Filament Fabrication. The irreversible thermal strain (ITS) and coefficient of linear thermal expansion (CLTE) of four sets of samples with various sizes and thicknesses of the layer in the three directions of the measurements were investigated. The thermomechanical analysis (TMA) was used for the investigation of thermal deformation. During the study, the dependencies of deformation on temperature were obtained. The samples' CLTE values at various ranges of temperatures were estimated using the obtained dependencies. ITS was observed after heating to 80 ℃ during the first TMA cycle. The values reached 8 – 9 %. The impact of layer thickness and the number of layers in the sample on ITS was noticed. Shrinkage in the X direction and expansion in the Z direction with almost the same values were observed. Finite element code ANSYS was used to simulate the distribution of temperature and accumulation of residual thermal stresses in the printed part. The correlation was obtained between the level of simulated residual thermal stresses for samples with different number of layers and layer thicknesses and measured ITS after annealing.

Experimental Analysis of Pre-Forming Parameters on Abnormalities, Thickness, and Void Content of Glass/Epoxy Composite In VBO-Oven Cure Manufacturing

Autoclave-based production of composite laminates leads to extended time requirements, increased manufacturing expenses, and the accumulation of significant residual stress. These limitations have spurred research and innovation in seeking alternative out-of-autoclave (OOA) processing methods. The present study aimed to measure the impact of distinct and combined pre-forming parameters within the pre-forming process of vacuum bagging with oven curing (VBO-oven curing) on thickness, abnormalities, and void content in cured laminates of conventional, cost-effective glass/epoxy autoclave composite material. The abnormalities were analyzed using ultrasonic C-scan and thickness measurement was done to determine thickness variations. A burn-off test was employed to measure the void content. The relationship between processing parameters was subsequently investigated via analysis of variance (ANOVA). Higher thickness standard deviation was yielded at higher abnormality percentages in the C-scan results, resembling total discontinuities and non-uniformities. Voids were highest in the laminate produced via the standard pre-forming process. Edge breather, release wax, and intensifier reduced the void content by approximately 11.87%, 12.93% and 6.85%, respectively.

Influence of Scanning Strategy and Post-Treatment on Cracks and Mechanical Properties of Selective-Laser-Melted K438 Superalloy

The feasibility of manufacturing high-performance components with complex structures is limited due to cracks in some superalloys fabricated by selective laser melting (SLM). By controlling the main process parameters such as scanning strategy, the adverse effects of cracks can be effectively reduced. In this paper, the effects of two different SLM scanning strategies with island and ‘back-and-forth’ and post-heat treatment on the cracks and mechanical properties of selective-laser-melted (SLMed) K438 alloy were investigated. The results show that the SLM method of the ‘back-and-forth’ scanning strategy had better lap and interlayer rotation angles and a more uniform distribution of laser energy compared with the island scanning strategy. The residual stress accumulation was reduced and crack formation was inhibited under this scanning strategy owing to the cooling and shrinkage process. In addition, the dislocation motion was hindered by the formation of uniformly dispersed MC carbides and γ’ phases during the SLM K438 alloy process, which resulted in the density of the as-built SLMed K438 alloy being up to 99.34%, the hardness up to 9.6 Gpa, and the tensile strength up to 1309 MPa. After post-heat treatment, the fine secondary γ’ phases were precipitated and dispersed uniformly in the Ni matrix, which effectively improved the Young’s modulus and tensile strength of the alloy by dispersing the stress-concentrated area.

Surface Residual Stress Release Behavior of Shot-Peened Springs

Shot peening is the primary method used to improve the fatigue life of springs. In this study, we aimed to quantify the reduction in residual stresses in the shot-peened layer by considering factors such as surface roughness, cyclic loading, and the helix angle, based on the spring’s periodic variation and curvature characteristics. We developed an equivalent replacement algorithm to address the challenge of characterizing the dynamic accumulation and attenuation of residual stresses under cyclic multiaxial stresses. This algorithm accurately modeled the dynamic attenuation of residual stresses and was incorporated into the spring life prediction model. Experimental validation demonstrated the high accuracy of the model for predicting fatigue life.

Simulation of Starch Gel Printing and Deformation Process Using COMSOL.

The food industry holds immense promise for 3D printing technology. Current research focuses mainly on optimizing food material composition, molding characteristics, and printing parameters. However, there is a notable lack of comprehensive studies on the shape changes of food products, especially in modeling and simulating deformations. This study addresses this gap by conducting a detailed simulation of the starch gel printing and deformation process using COMSOL Multiphysics 6.2 software. Additive manufacturing (AM) technology is widely acclaimed for its user-friendly operation and cost-effectiveness. The 3D printing process may lead to changes in part dimensions and mechanical properties, attributable to the accumulation of residual stresses. Studies require a significant amount of time and effort to discover the optimal composition of the printed material and the most effective deformed 3D structure. There is a risk of failure, which can lead to wasted resources and research delays. To tackle this issue, this study thoroughly analyzes the physical properties of the gel material through COMSOL Multiphysics 6.2 software, It simulates the heat distribution during the 3D printing process, providing important insights into how materials melt and solidify. Three-part models with varying aspect ratios were meticulously designed to explore shape changes during both the printing process and exposure to an 80 °C environment, employing NMR and rheological characterization. Using the generalized Maxwell model for material simulation in COMSOL Multiphysics, the study predicted stress and deformation of the parts by analyzing solid heat transfer and solid mechanics physical fields. Simulation results showed that among three models utilizing a gel-PET plastic membrane bilayer structure, Model No. 1, with the largest aspect ratio, exhibited the most favorable deformation under an 80 °C baking environment. It displayed uniform bending in the transverse direction without significant excess warpage in the edge direction. In contrast, Models No. 2 and No. 3 showed varying degrees of excess warpage at the edges, with Model No. 3 exhibiting a more pronounced warpage. These findings closely aligned with the actual printing outcomes.

Influence of shear yield strength of rail material on the shakedown limit in shakedown map

Rail materials with different shear yield strengths can exhibit different rolling contact fatigue (RCF) damage response during cyclic contact loading. The objective of this work is to achieve the actual shakedown limits in the shakedown map for rail materials with different shear yield strengths through RCF simulation tests of wheel-rail, and to investigate the relationship between the shear yield strength (ke) and the shakedown limit. Rolling-sliding tests were performed to investigate the RCF damage states of three types of rail materials with different shear yield strengths. Then, according to the differences of RCF damage states for each rail material and the method of nonlinear curve fitting, the actual shakedown limits for three types of rail materials were obtained. The actual shakedown limits for the three types of rail materials were lower than the original one in the classical shakedown map. With an increase in the shear yield strength (ke) of the rail material, the actual shakedown limit is reduced. Moreover, a relationship emerged which allowed a simple method to be proposed to obtain the actual shakedown limit based on the shear yield strength. The changing process and differences in the impact of different shear stress levels on the microstructural damage transformation of rail materials from the perspective of contact mechanics have been discussed. The behavior of severe accumulation of residual stresses during cyclic loading and more likely initiation of microcracks are the main reasons why rail materials with a higher shear yield strength (ke) under great contact loads are more prone to developing RCF crack damages. That is, the shakedown limit for the material with a higher shear yield strength (ke) is much lower. In view of the application of the shakedown map in the evaluation and prediction for RCF damage of rail materials with different shear yield strengths, different shakedown limits should be applied to different rail materials when analyzing their likely performance.

Bi-layer in-situ phosphorus doped poly-Si films by PECVD for blistering-free high-efficiency industrial TOPCon solar cells

The passivating contact concept stands out as one of the most promising and industrially viable photovoltaic (PV) technologies. Further improving the quality of physical contact has become a focus of ongoing research. The film blistering issue has been identified as one of the major bottlenecks for the polysilicon (poly-Si) films deposited by the PECVD approach. In this study, we investigated how the in-situ phosphorus (P) doping level within the poly-Si films contributes to the occurrence of blistering. Our investigations into the film blistering mechanisms reveal that a high in-situ P-doping suppresses hydrogen release levels and reduces the accumulation of residual stress during annealing, which leads to the blistering-free appearance, especially observed in heavily P-doped poly-Si films. However, as excessive P-doping could weaken the interfacial passivation quality, we propose a bi-layer structure of P-doped poly-Si films which allows the doping profile to be tailored and maintain good quality passivating contacts. Based on the bi-layer structure, we fabricated industrial-sized tunnel oxide passivated contact (TOPCon) solar cells, which attained an average efficiency of 23.84%. Our work not only presents a promising strategy for improving the performance of passivating contacts via the PECVD approach but also underscores the significant potential for its widespread implementation in industrial TOPCon solar cell manufacturing.

Residual stress accumulation in large-scale Ti-6Al-4V wire-arc additive manufacturing

Large-scale additive manufacturing (AM) is of interest in the manufacturing industry to produce components of dimensions on the order of hundreds of millimeters to meters in scale. Wire-arc AM (WAAM) of Ti-6Al-4V (Ti64) is an attractive technique for large-scale AM in the aerospace industry, give the high strength-to-weight ratio of the material and high deposition rate of the process. However, due to the large scale, significant distortion and residual stresses are developed in the material during deposition and cooling, potentially leading to part failure. WAAM of a prototypical large-scale Ti64 machine tool component is studied in this work via finite element analysis (FEA). Element activation/deactivation technique is employed to simulate deposition and the resulting distortion and residual stress (RS) predictions are analyzed to evaluate the possibility of crack formation. Significant distortion (∼10 mm) and RS (>1300 MPa) is predicted, suggesting the formation of cracks and possible crack propagation into the build region. Incorporation of fillets significantly reduces RS concentration regions, thus reducing the possibility of part failure. Material deposition sequence also affects the RS pattern in the build.

Deep reinforcement learning based toolpath generation for thermal uniformity in laser powder bed fusion process

Laser powder bed fusion (LPBF) is a widely used metal additive manufacturing technology. However, the accumulation of internal residual stress during printing can cause significant distortion and potential failure. Although various scan patterns have been studied to reduce possible accumulated stress, such as zigzag scanning vectors with changing directions or a chessboard-based scan pattern with divided small islands, most conventional scan patterns cannot significantly reduce residual stress. The proposed adaptive toolpath generation (ATG) algorithms, aiming to minimize the thermal gradients, may result in extremely accumulated temperature fields in some cases. To address these issues, we developed a deep reinforcement learning (DRL)-based toolpath generation framework, with the goal of achieving uniformly distributed heat and avoiding extremely thermal accumulation regions during the LPBF process. We first developed an overall pipeline for the DRL-based toolpath generation framework, which includes uniformly sampling, agent moving and environment observation, action selection, moving constraints, rewards calculation, and the training process. To accelerate the training process, we simplified the data-intensive numerical model by considering the turning angles on the toolpath. We designed the action spaces with three options, including the minimum temperature value, the smoothest path, and the second smoothest path. The reward function was designed to minimize energy density to ensure the temperature field remains relatively stable. To verify the effectiveness of the proposed DRL-based toolpath generation framework, we performed numerical simulations of polygon shape printing domains. In addition, four groups of thin plate samples with different scan patterns were compared using the LPBF process. The results indicated that using our proposed DRL algorithms for toolpath generation reduced the maximum distortion of the sample by approximate 47% compared to Zigzag patterns, 29% compared to Chessboard patterns, and 17% compared to ATG patterns. Our work demonstrated the effectiveness of implementing machine learning algorithms in the toolpath generation of the LPBF process.

Cyclic degradation mechanisms of Al0.3CoCrFeNi high-entropy alloy under different loading rates

The effect of loading rate on the cyclic degradation behavior of Al0.3CoCrFeNi high-entropy alloy (HEA) was investigated through nanoindentation experiments and molecular dynamics simulations. The evolution of mechanical properties and microstructure characteristics under different loading rates, as well as the mechanisms of cyclic degradation, were revealed. It is found that the increase of the loading rate induces higher hardness and smaller nanoindentation depth of the Al0.3CoCrFeNi HEA, which gradually increases with the cyclic loading of nanoindentation, resulting in a larger difference in characteristic nanoindentation depth among different loading rates. What’s more, a larger loading rate is inclined for nanoindentation depth to reach a steady state. Slip lines and pile-ups are formed around the nanoindentation region at higher loading rates indicating the occurrence of a more localized plastic deformation, while an amorphous transformation occurs at different loading rates after cyclic nanoindentation. Cyclic loading results in the gradual accumulation of residual stress, nanoindentation depth and amorphous structures within the material, and a localized plastic deformation. In summary, cyclic degradation of the Al0.3CoCrFeNi HEA is featured by cyclic softening due to dislocation slipping and the accumulation of amorphous phases.

Residual stresses and distortion in additively-manufactured SS316L-IN718 multi-material by laser-directed energy deposition: A validated numerical-statistical approach

In the present work, a numerical-statistical approach was used to study the distortion and residual stress in the additive manufacturing (AM) of SS316L-IN718 multi-material structure. Also, the structure was fabricated by laser-directed energy deposition (L-DED), and experimental measurements via thermocouple and micro X-ray diffraction were performed to validate the numerical results. In a good agreement with the experiments, the thermomechanical modeling of the process showed that through-thickness residual stresses (build direction) are distributed as a large accumulation of compressive residual stress in the mid-length of the structure-substrate interface and the maximum tensile residual stress at its two free ends. The critical development of longitudinal residual stresses (scanning direction) at the interface of the structure due to the sudden change in properties has caused the formation of the maximum tensile residual stress (up to 475 MPa) in this area and immediately changed its nature to compressive that can easily lead to localized cracking. Besides, Von Mises stress distribution indicated the concentration of stress at the interfaces of structure-substrate and base alloys, in such a way that it causes yielding in the SS316L section. On the contrary, less (plastic) strain occurred in the IN718 section due to higher yield strength. The results of the statistical modeling using multiple response analysis in the response surface method (RSM) also determined the desirable minimum level of longitudinal strain and stress of the structure (about 0.013 and 320 MPa, respectively) in the laser power range of 300–380 W and the powder per unit length of 5–25 g/m. In addition to minimization, it was demonstrated that sharp changes in longitudinal strain and stress at the interface of multi-material structure can be effectively reformed to mild changes by designing compositional gradients through thermodynamic calculations, owing to the approximation of the properties of adjacent layers.

Study of the Relationship between Changes in the Structural, Optical, and Strength Properties of AlN Ceramics Subjected to Irradiation with Heavy Xe23+ Ions.

The purpose of this study is to comprehensively analyze the influence of different fluences of irradiation with Xe23+ heavy ions on alterations in the structural, optical, and strength properties of AlN ceramics and to establish a connection between structural distortions and alterations in the optical and mechanical properties of the ceramics. X-ray diffraction, UV-Vis and Raman spectroscopy, and indentation and single-compression methods were used as research methods. During the study, it was demonstrated that at low irradiation fluences, the main role in the changes in the properties of the AlN ceramics is played by effects related to changes in their optical properties and a fundamental absorption edge shift, which characterizes changes in the electronic properties of the ceramics (changes in the distribution of electron density). A study of the variations in the optical properties of the examined samples in relation to the irradiation fluence showed that when the fluence surpasses 5 × 1011 ion/cm2, an extra-spectral absorption band emerges within the range of 3.38-3.40 eV. This band is distinctive for the creation of vacancy ON-VAl complexes within the damaged layer's structure. The presence of these complexes signifies structural deformations and the accumulation of defective inclusions within the damaged layer. An analysis of changes in the parameters of the crystal lattice showed that structural distortions in the damaged layer are due to the accumulation of tensile residual mechanical stresses, an increase in the concentration of which leads to the swelling and destruction of the damaged layer. Some correlations between the mechanical properties of ceramics and the irradiation fluence indicate the ceramics' remarkable resistance to radiation-induced brittleness and weakening. These effects become apparent only when structural damage accumulates, resulting in the swelling of the crystal lattice exceeding 2.5-3%.

Study of Cooling Medium Variables during Quenching in SAE 4340 Steel Using Statistical and Modeling Tools

Although quenching is one of the most widely used heat treatments in the metal-mechanical industry to improve the mechanical properties of steels, it is also responsible for the generation of residual stress, distortion, and fractures in the treated parts. The high-temperature gradients present during quenching and martensitic transformation are the main failure mechanisms. Cooling is the critical quenching stage where several variables that need to be controlled are involved in reducing these problems. The objective of this research was to evaluate the main variables in the quenching process in SAE 4340 steels, which promote distortion, residual stress accumulation, and fracture failures. A 2ᴷ factorial experiment was designed, samples with C-ring geometry susceptible to changes in quenching variables were used, and the variables studied were the agitation and temperature of the quenching medium. Experimental measurements, statistical tools and modeling were used to evaluate and predict the distortion generated in quenched samples. Such tools include Minitab 21® software and its statistics utilities. Furthermore, a finite element method model was carried out using STFC Deform®. The results suggest that there are optimal conditions in the quenching process to minimize distortion and residual stresses and to improve mechanical properties of quenched parts; therefore, the methods used in this work could be useful to detect and control the appearance of defects in an industrial environment.

Physics of collective cell migration.

Movement of cell clusters along extracellular matrices (ECM) during tissue development, wound healing, and early stage of cancer invasion involve various inter-connected migration modes such as: (1) cell movement within clusters, (2) cluster extension (wetting) and compression (de-wetting), and (3) directional cluster movement. It has become increasingly evident that dilational and volumetric viscoelasticity of cell clusters and their surrounding substrate significantly influence these migration modes through physical parameters such as: tissue and matrix surface tensions, interfacial tension between cells and substrate, gradients of surface and interfacial tensions, as well as, the accumulation of cell and matrix residual stresses. Inhomogeneous distribution of tissue surface tension along the cell-matrix biointerface can appear as a consequence of different contractility of various cluster regions. While the directional cell migration caused by the matrix stiffness gradient (i.e., durotaxis) has been widely elaborated, the structural changes of matrix surface caused by cell tractions which lead to the generation of the matrix surface tension gradient has not been considered yet. The main goal of this theoretical consideration is to clarify the roles of various physical parameters in collective cell migration based on the formulation of a biophysical model. This complex phenomenon is discussed with the help of model systems such as the movement of cell clusters on a collagen I gel matrix, simultaneously reviewing various experimental data with and without cells.

Corrosion behavior and mechanical property of Mg-4Li-1Ca alloys under micro-compressive stress

Biomedical materials may suffer from stress-induced corrosion when performing as implant materials at load-bearing sites, bringing about variations in the microstructure, corrosion resistance, and mechanical properties. In this study, the corrosion behavior and mechanical properties of an extruded Mg-4Li-1Ca alloy were investigated under different micro-compressive stresses (0–6 MPa) using a novel homemade loading device. Under 0–3 MPa of micro-compressive stress, the strong basal texture of extruded Mg-4Li-1Ca alloys was weakened and the internal stress gradient stimulated grain boundary migration to induce grain growth. Meanwhile, increased stress resulted in the precipitation of second-phase particles and the accumulation of residual stress, accelerating the corrosion rate due to preferential corrosion. However, with increasing stress, the volume fraction of the second phase increased, becoming the dominant factor controlling the corrosion rate, and residual stress was released for samples under 4.5–6 MPa of micro-compressive stress. Hence, surface corrosion product films rapidly formed and served as effective physical barriers, weakening the microstructural effect on the corrosion behavior. The yield strength of Mg-4Li-1Ca alloy reached 95.48 MPa under 3 MPa of micro-compressive stress owing to the dual effects of precipitation strengthening and shear-band strengthening. The relationships between microstructure, corrosion behavior, and mechanical property provide a theoretical foundation for understanding the degradation characteristics of the Mg-4Li-1Ca alloy under physiological loading and practical application.

Numerical investigation of residual stresses in thin-walled additively manufactured structures from selective laser melting

Selective laser melting (SLM), a metal laser powder bed fusion additive manufacturing method, involves several cycles of very high temperature gradient heating and cooling during the solidification of each layer, which can cause the accumulation of detrimental residual stresses in the 3D printed structure. This work uses a thermo-mechanical computational modeling approach to investigate the formation of residual stresses in thin-walled structures and also investigates the effects of varying taper on the evolution of residual stress profiles of the build. Three material grades; namely, Titanium alloy (Ti64), Stainless steel (SS316L) and Inconel (IN718) have been used for this study. The results show that varying taper thickness up to a certain value has a considerable effect on residual stress evolutions in thin-wall structures, however, beyond a certain value of the taper level, the residual stresses are observed to converge. Also, it is observed that the tensile stresses at the edges of the wall are almost equal or exceed the yield stress of the materials. Among the three material grades considered, the magnitude of residual stress was higher in Ti64 and the stresses are dominant in the build direction. The simulation framework is also applied to analyze the effect of residual stresses on the mechanical properties of complex thin-wall structures such as TPMS (Triply Periodic Minimum Surfaces) lattice structure, using Schwarz Primitive (SP) as a case study. It is observed that the residual stresses lower the effective elastic properties of the lattice structures by 6% ∼ 10% for the three material grades but has no effect on the effective plastic behavior of the material.

Injection‐compression molding process on optical quality optimization of plastic lens array

AbstractPlastic lens arrays (PLAs) have the advantages of a light weight and a compact size. However, their optical performance is often degraded by warpage, caused by the accumulation of residual stress during the injection molding process. Accordingly, the present study employs mold flow analysis simulations and a Taguchi‐Gray relational analysis (GRA) framework to optimize the processing parameters of the injection compression molding (ICM) process. The analyses focus specifically on the effects of the mold temperature, melt temperature, injection velocity, packing pressure, packing time, and compression gap on the optical path difference (OPD) and lens center displacement (LCD) of the fabricated lens array. The results confirm that the optimized processing parameters significantly improve the OPD, LCD, birefringence, and imaging properties of the PLA compared to those of a PLA fabricated using standard molding conditions.

Revealing sodium storage mechanism of hard carbon anodes through in-situ investigation of mechano-electrochemical coupling behavior

Hard carbon (HC) is considered a promising anode material for sodium-ion batteries due to its relatively low price and high specific capacity. However, HC still suffers from unclear reaction mechanisms and unsatisfactory cycling stability. The study of mechano-electrochemical coupling behavior by in-situ measurement techniques is expected to understand the sodium storage and degradation mechanisms. In this paper, the strain and stress evolution of HC anodes at different sodiation/desodiation depths and cycles are investigated by combining electrochemical methods, digital image correlation, and theoretical equations. The observation by monitoring the in-situ strain evolution during the redox process supports the “adsorption-intercalation/filling” mechanism in reduction and the “de-filling/de-intercalation-desorption” mechanism in oxidation. Further studies have demonstrated that the strain and stress of the electrode show periodic changes accompanied by a continuous accumulation of residual stress during cycles, explaining the capacity degradation mechanism of HC from a mechanical perspective. In addition, when the higher current density is applied, the electrodes experience greater strain and stress associated with the Na+ insertion rate. This work clarifies the Na-storage mechanism and the mechano-electrochemical coupling mechanism of HC anodes by in-situ strain measurement, which helps optimize and design the anode materials of sodium-ion batteries from the perspective of interface microstructure and multi-field coupling, such as in situ integrated interface structure design.