Stress Field Distribution Research Articles

Material removal mechanism of TiCp/Fe composite by multi-diamond-abrasive-grinding considering the random distribution characteristics of particles

The TiC ceramics reinforced Fe matrix composite (TiCp/Fe) exhibits exceptional properties, including high hardness, strength, wear, and heat resistance. This study focuses on investigating the material removal mechanism to achieve high-quality and low-damage surfaces. A three-dimensional particle random distribution algorithm is proposed based on the random distribution characteristics of TiC particles. Furthermore, a multi-diamond-abrasive grinding finite element model is established using the Rayleigh probability distribution model to account for the randomness of undeformed chip thickness during the grinding process. This study combines experimental and simulation analyses to investigate the variations in grinding forces, stress field distributions, and surface and subsurface quality. The results reveal that the material removal process can be categorized into five stages: ploughing of the Fe matrix and TiC particle, TiC particle crack initiation, TiC particle crack extension, and TiC particle fracture. Moreover, the process of removing TiC particles can be further grouped into ductile removal, ductile-brittle removal, and brittle removal, depending on the undeformed chip thickness. This study improves the comprehension of the mechanism of TiCp/Fe composite material and establishes a significant practical guidance for the diamond grinding processing of metal matrix composites.

An online prediction method of three-dimensional machining residual stress field based on IncepU-net

The magnitude and distribution of residual stress field inside thin-walled parts is a critical factor influencing machining deformation. Traditional methods relying on offline data struggle to rapidly and accurately predict evolutionary state of residual stress fields, due to the time-varying and nonlinear characteristics in machining. This paper presents an online prediction method for residual stress in machining thin-walled parts based on deep learning. The multi-channel vector model is proposed to incorporate geometric, physical, and process information as input for deep learning models. A deep learning framework utilizing the IncepU-net network is developed and trained using both experimental and finite element simulation data. Results indicate a mean error of 6.2 MPa compared to experimental values, with an overall prediction time of 0.17 s. The proposed method can online predict the magnitude and distribution of residual stress field in machining, which offers cost-effectiveness and strong generalization capabilities.

Study of the development patterns of water-conducting fracture zones under karst aquifers and the mechanism of water inrush

The hydrogeological conditions of the Qianbei coalfield are complex, and karst water in the roof rock frequently disrupts mining operations, leading to frequent water inrush incidents. Taking the representative Longfeng Coal Mine as a case study, research was conducted on the development pattern of the water-conducting fracture zone and the water inrush mechanisms beneath karst aquifers. On the basis of key stratum theory and calculations of the stratum stretching rate, the karst aquifer in the Changxing Formation was identified as the primary key stratum. It was deduced that the water-conducting fracture zone would develop into the karst aquifer, indicating a risk of roof water inrush at the working face. Numerical simulations were used to study the stress field, displacement field, and plastic zone distribution patterns in the overlying roof strata. Combined with similar simulation tests and digital speckle experiments, the spatiotemporal evolution characteristics of the water-conducting fracture zone were investigated. During the coal mining process, the water-conducting fracture zone will exhibit a "step-type" development characteristic, with the fracture morphology evolving from vertical to horizontal. Near the goaf boundary, the strain gradually decreases, and the instability of the primary key stratum significantly impacts the mining space below, leading to the closure of interlayer voids or the redistribution of water-conducting fissure patterns. Field measurements of the water-conducting fracture zone reveal that postmining roof fractures can be classified into tensile-shear, throughgoing, and discrete types, with decreasing water-conducting capacity in that order, the measured development height of the water-conducting fracture zone (51 m) aligns closely with the theoretical height (51.37 m) and the numerical simulation height (49.17 m). Finally, from the perspective of key stratum instability, the disaster mechanisms of dynamic water inrush and hydrostatic pressure water inrush beneath the karst aquifers in the northern Guizhou coalfield were revealed. The findings provide valuable insights for water prevention and control efforts in the Qianbei coalfield mining area.

Three-dimensional numerical simulations and experimental studies on the viscoelastic rheological and deformation behavior of polymer catheter in gas-assisted extrusion processing

Gas-assisted extrusion is an effective method for improving the deformation behavior of polymer catheters during extrusion. However, the underlying mechanisms that dictate how geometrical and constitutive models influence the complex rheological behavior of the melt are not yet fully understood, which hinders further utilization and optimization. In this study, the three-dimensional (3D) gas–liquid–gas model for catheter gas-assisted extrusion was constructed. Subsequently, the Bird–Carreau model and the Phan–Thien–Tanner (PTT) model were employed in finite element numerical simulations to analyze the complex behavior. For comparative analysis, simplified two-dimensional (2D) model numerical simulations were also conducted. Additionally, experiments on catheter gas-assisted extrusion and parameterization studies of key constitutive model parameters were performed. The findings indicate that the 3D model, when integrated with the PTT constitutive model, demonstrates superior predictability and aligns more closely with experimental results. Furthermore, as the flow rate increases, discrepancies among different models diminish, and the distance required for the melt and gas to achieve motion equilibrium decreases. The internal mechanisms behind these phenomena are elucidated through the analysis of velocity and stress field distributions. This research enhances our understanding of the complex rheological behavior in polymer catheter gas-assisted extrusion, providing valuable insights for both academic research and industrial production in this field.

Correlation between individual phase constitutive properties and plastic heterogeneities in advanced-high strength dual-phase steels

The present study comprehensively investigates the individual phase constitutive properties and plastic heterogeneities in advanced high-strength steels (AHSS), particularly DP590 and DP780 dual-phase (DP) steels. A machine learning-based model is implemented to identify the ferrite and martensite phases in the microstructures of DP590 and DP780. Then, the constitutive properties of ferrite and martensite phases are successfully obtained through a hybrid approach of in-situ neutron diffraction coupled with the crystal plasticity finite element method (CPFEM). The distinct microstructures between DP590 and DP780 result in different macroscopic and microscopic properties among the two materials. Owing to different martensite volume fractions (Vm) in DP590 (Vm = 8.3 %) and DP780 (Vm = 35.4 %), a noticeable dependency of plastic heterogeneities during deformation on martensite fraction and its spatial distribution is revealed. Compared to DP590, the deformed microstructure of DP780 exhibits a more heterogeneous distribution of stress and strain fields, along with significant formation of plastic strain localization leading to a remarkable increase in strain partitioning index. It shows that a lower fraction of martensite with its discrete distribution decreases martensite ability to hinder the ferrite deformation, thus strain localization is primarily concentrated within the ferrite phase as the predominant failure mode in DP590. In contrast, a higher martensite fraction in DP780 causes more pronounced strain localization which occurs in the ferrite and at the ferrite/martensite interface. In addition, interconnect distribution between martensite islands enhances the inhibition of martensite to ferrite deformation, thereby high strain gradient at their interface leads to prevalence of ferrite/martensite interface decohesion in DP780.

Theoretical and numerical analyses of thermal stresses and temperature variations in disc cutter cutting composite strata under thermal-force multi-fields

Composite strata consisting of hard and soft rock are common during shield cutter excavation. The friction cutting process generates a large amount of cutting heat, high temperature will produce thermal stresses and thermal expansion in the disc cutter ring, resulting in wear and deformation of the cutter, reducing its rock breaking performance. From the perspective of thermal-force change in cutter, This study establishes the theory of frictional heat generation and the theory of thermal stress of elastomer to analyse the frictional heat generation and derive the thermal stress theory of elastomer model in cutter. Numerical simulations were carried out to analyse the thermal-force multi-field coupling process considering the influencing factors such as penetration, cutting time, rock strength, etc. Solve the heat conduction equation and radial temperature field distribution from the heat transfer perspective. The comparative study of theoretical analysis, numerical simulation and experimental values shows that the theoretical and numerical results of thermal stress and temperature field distributions are consistent, which verifies the reasonableness of the theoretical derivation and numerical model.

Numerical characterization on fracture evolution behavior of pre-flawed sandstone under monotonic and multilevel cyclic loading

This study employed an improved stress corrosion model within a three-dimensional particle flow program to investigate the mechanical and cracking behavior of fractured sandstone samples with varying rock bridge angles under both monotonic loading and multilevel cyclic loading. Firstly, using the experimental results from intact sandstone under uniaxial compression, we calibrated the microscopic mechanical parameters of the parallel bond model. Then, the model was validated using the experimental results of fractured sandstone under monotonic and cyclic loading. Finally, the initiation, propagation, and coalescence behavior of cracks in fractured sandstone samples under the above two loading paths, as well as the evolution process of the stress field, displacement field, and force chain distribution, were discussed in detail. The results show that the stress–strain curves, strength, deformation parameters, and macroscopic failure modes obtained from numerical simulations are consistent with those from laboratory mechanical tests. The mechanical behavior of fractured sandstone is influenced by both the rock bridge angle and the loading path. As the rock bridge angle decreases, the mechanical parameters of the sample show an increasing trend, and the influence of rock bridge angle on the failure mode is reduced. Cracks in the samples all initiate at the tips of pre-existing flaws, and the rock bridge angle affects the crack propagation and coalescence process: for sandstones with smaller rock bridge angles, cracks gradually extend to the sample’s ends; for sandstones with larger rock bridge angles, direct coalescence of cracks at the rock bridge is observed, then extending to the sample’s ends. Compared with monotonic loading, the damage degree of sandstone samples under multilevel cyclic loading is more severe, and even obvious block spalling is observed. The experimental and numerical simulation results are expected to improve the understanding of the mechanical behavior and fracture behavior of fractured rocks under monotonic and multilevel cyclic loading.

Improving mechanical properties of lattice structures using nonuniform hollow struts

In contrast to constant-strut lattices, the introduction of innovative strut designs has the potential to enhance the mechanical properties of lattice structures. This study presents a Bézier curve-based nonuniform section design for body-centered cubic lattices with hollow struts (BCCH). Periodic boundary conditions are applied to the unit cells, and a finite element (FE) numerical homogenization method is employed to assess their elastic properties. A comprehensive dataset is generated through the FE model, which is subsequently divided into training, validation, and testing sets. The coordinates of the Bézier curve control points serve as inputs to deep learning networks, which are trained on the training dataset. Relative density and elastic properties are treated as two distinct networks, with the validation set utilized to prevent overfitting. The objective function consists of two weighted components: one aims to maximize the relative Young's modulus, while the other ensures that the relative density achieves a specified value. An evolutionary algorithm is employed to optimize the objective function, with variations in the control point coordinates constrained to specific ranges. By leveraging the fast inference ability of the deep learning model, the stiffness and orientation-dependent mechanical properties can be efficiently tailored. Our results demonstrate that the optimized structures demonstrate superior stiffness (+92.8 %) and distributed stress field compared to the benchmark lattice. The design method also enables tailoring of specific mechanical properties, including isotropic elasticity. 3D-printed lattice designs were fabricated and compression tests confirmed agreement with simulation results in terms of stiffness. Additionally, the optimized designs exhibit superior strength (+99.6 %) and toughness compared to the benchmark lattices.

Stress Fields Distribution and Simulation in 3C-SiC Resonators

In this paper the stress field distribution in 3C-SiC (111) resonators has been studied by micro-Raman measurements and COMSOL simulations. The measurements show that the asymmetry of the anchor points configuration produce an asymmetry in the stress filed distribution. This behavior has been confirmed also by the simulations. Furthermore, from the simulations the importance of the reduction of the under etching of the anchor points of the resonators has also been observed. In fact the reduction of this under etch produces a decrease of the stress in the double clamped beams, a small reduction of the resonance frequency, and a large reduction of the Q-factor and then of the oscillation frequency stability of the resonators in closed-loop operation.

In-situ stress field simulation and fracture distribution prediction of middle lower Ordovician in Zone B of Tahe Oilfield, Tarim Basin

This study constructed a heterogeneous rock mechanics model through well seismic joint inversion, set up a dual cycle statement to optimize the application of boundary loads, and obtained the current stress field distribution in Zone B. At the same time, we preferred the rock fracture criterion, carried out the quantitative characterization of different natures of fractures, and used the integrated fracture development rate to portray the integrated fracture development situation. Finally, the horizontal stress difference, stress heterogeneity coefficient, and comprehensive fracture rate were proposed to define the development index of fractured reservoirs. The results show that (1) the maximum horizontal principal stress is 102–144 MPa, and the minimum horizontal principal stress is 85–125 MPa; (2) the development rate of tension fractures is 0.03–0.23, the development rate of shear fractures is 0.15–0.54, and the integrated fracture development rate is 0.28–0.79; (3) the development index of fracture-type reservoirs is >2.3, Class I; 1.8–2.3, Class II; When it is lower than 1.8, Grade III. This article attempts to apply the stress field simulation results to the quantitative prediction of reservoir fractures, adding new ideas for the practical application of stress field results.

Multimodal data fusion enhanced deep learning prediction of crack path segmentation in CFRP composites

Carbon fiber-reinforced polymer (CFRP) composites are extensively used in various engineering applications due to their superior strength-to-weight ratio and excellent mechanical properties. Predicting crack propagation paths in CFRP composites is a complex challenge due to their multiphase nature and intricate microstructural interactions. While finite element (FE) simulations possess significant capabilities for this purpose, they entail substantial computational demands and extended execution times, thereby limiting their viability in applications with high computational requirements. To address this challenge, we propose an end-to-end deep learning framework specifically for predicting crack propagation paths in two-dimensional CFRP composites. Drawing inspiration from semantic segmentation techniques, we employ EfficientNet for feature extraction, enabling the capture of hierarchical and multiscale features from both microstructure images and stress field distributions. A key aspect of our framework is the utilization of multimodal data fusion and self-attention mechanisms to effectively integrate these diverse data sources. The results demonstrate the effectiveness of our multimodal feature integration approach, producing accurate segmentations of crack path. This novel framework offers a promising approach to understanding and predicting failure mechanisms in composite materials, with significant implications for the design and maintenance of advanced composite structures.

Research on thermal-solid coupling behavior of drum brake under emergency braking on slopes

Abstract When a truck makes emergency braking while driving on a slope, the transient impact force generated can easily cause personal injury to passengers and damage the vehicle’s braking system. In order to study the working state of the brake under this working condition, the ANSYS finite element thermal-solid coupling transient analysis method was used to establish the mechanical model and finite element model of the vehicle and brake under the slope emergency braking state, showing the temperature field and stress field distribution rules and interactions of the drum brake under this working condition, and compared with the flat road emergency braking condition. The results show that the maximum temperature of the brake reaches 184.26°C during emergency braking, and the stress field and temperature field are strongly coupled in two directions, which can easily lead to uneven wear of the linings and a reduction in the fatigue life of the brake.

Research on Stability of Mining Roadway of "Three Soft" Coal Seam based on FLAC3D

In order to reduce the serious roadway deformation during mining, the support scheme is optimized. Based on the actual geological data of mining roadway 11070, the plastic zone morphology, stress field and displacement distribution of roadway under different support schemes are analyzed by numerical simulation. The results show that scheme 1 has better supporting effect and higher roadway stability, which provides a reference for the same type of roadway support.

Numerical simulation and properties analysis of Ta10W alloy joints prepared by electron beam welding

Vacuum electron beam welding has the characteristics of concentrated energy, controllable heat input, almost no pollution, and a small heat-affected zone. In this study, the Ta10W alloy was successfully connected by electron beam welding (EBW), and numerical simulations were employed to examine the distribution of temperature and stress fields throughout the welding process. Additionally, the influence of EBW on the microstructure and corrosion resistance of the welded joints was scrutinized. Findings indicate that the welding heat process led to a reduction in grain boundary energy, thereby facilitating thermal activation processes that contributed to grain growth. Grain boundary migration and possible dynamic crystallization led to the appearance of the coarse columnar crystal structure in the welded joint. A three-dimensional, nonlinear, transient, thermo-mechanically coupled finite element model was developed for the electron beam welding of Ta10W alloy. The shape characteristics and size of the weld and transient thermal cycles calculated by numerical simulations were in reasonable agreement with experimental results. Electron beam welding reduced the corrosion resistance of the Ta10W alloy, and the corrosion product was mainly composed of Ta, O and Na.

Non-contact ultrasonic vibration-assisted laser metal deposition manufacturing Fe-based powder: Numerical simulation and experimental investigation

Fe-based powder was manufactured on 42CrMoA steel substrate using non-contact ultrasonic vibration-assisted(UVA) laser metal deposition(LMD) process with different exciting distances(d), and the temperature field and stress field distribution, microstructure and mechanical properties of the deposited layers were investigated. The results show that the distribution of temperature field was more uniform, especially at the bottom of the molten pool, and the gradient of temperature field decreased. Compared with the condition without UVA, the residual stress peak value of the tensile stress area decreased significantly after UVA applied. When d=80 mm, the peak tensile stress and compressive stress were 90.5 MPa and 72.6 MPa, respectively, which were reduced by 45.6 % and 25.2 % compared with the condition without UVA. The length of the columnar crystals and the region of the columnar crystals decreased at the interface after UVA applied. The application of UVA can significantly improved the microhardness of deposition layer. With the reduction of the residual stress at the interface and the improvement of uniformity, the tensile properties of the deposit were also significantly improved. The highest tensile strength was 1281.3 MPa when d=80 mm, which was 30.12 % higher than that without UVA.

Influence of tectonic stress field on oil and gas migration in the Tahe Oilfield carbonate reservoir: Identification of areas favorable for reservoir formation

An understanding of the tectonic stress field distribution in the carbonate reservoirs of the Tahe Oilfield is essential for oil and gas migration and reservoir reconstruction. This study adopts a geological genesis perspective and integrates the unique attributes of the carbonate reservoirs in the Tahe Oilfield to simulate three-dimensional stress fields using the finite element method and Petrel software. The simulation, which takes pore pressure and boundary constraints into consideration, aligns with the findings of acoustic emission tests conducted by previous researchers and validates the model by corroborating the maximum horizontal principal stress direction with imaging logging interpretations. With subsequent utilization of the generalized Coulomb-Mohr shear failure criterion and the Griffith generalized maximum tensile stress criterion, the simulated stress enables the prediction of the total fracture intensity. To complement this analysis, we integrate seismic data and fault formation mechanisms to characterize variations in fracture intensity within distinct regions of the study area. Three key findings emerge from this investigation. First, due to the Hercynian thermal event, X-shaped conjugate faults display a disproportionately high degree of development compared to other primary fractures. Analyzing the mechanisms of formation and development of these X-shaped strike-slip faults reveals discernible differences in deformation characteristics between NW-trending and NE-trending faults, with the former exhibiting a greater propensity for fracture rupture and efficient oil-gas migration. Second, fault intersections are critical and efficient conduits for fluid accumulation and thereby contribute to reservoir formation. Lastly, exclusive of X-shaped conjugate faults, NE-trending faults exhibit the greatest propensity for oil and gas accumulation and migration. Collectively, these findings facilitate the identification of areas favorable for oil and gas migration and provide a crucial mechanical analysis that can inform the exploration and development of the Tahe Oilfield.

Investigation on the interaction evolution and growth behavior of multiple cracks under fatigue loading

In this study, the cracks interaction is investigated on plates with different crack geometry parameters through finite element analysis and experiments. The presence of multiple cracks may lead to an enhancement or shielding effect on stress intensity factors (SIFs) depending on crack relative positions and sizes, thereby potentially accelerating or decelerating the crack propagation rate. When the crack tips of double parallel non-collinear cracks begin to overlap, the interaction between cracks transitions from an enhancement effect to a shielding effect, and the KII values reach their peak at this point, which are explained by the stress field distributions surrounding the cracks. For non-collinear double cracks with an inclined angle α, the shielding effect of inclined cracks becomes increasingly pronounced in comparison to horizontal cracks as the angle α increases. To verify the numerical results, fatigue crack propagation experiments were carried out on Al–Li alloy samples with double non-collinear cracks with different crack vertical distance. The experimental results show that growth direction of two non-collinear cracks underwent a transition when they overlapped, leading to load mode I changing into mixed mode of I + II. Based on both numerical simulations and experimental results, the material parameters C and m in Paris equation are modified, and then a new method for predicting the multiple cracks growth life is presented. By comparing with the experimental values, it was found that this method exhibits high accuracy and reliability.

Experimental and theoretical study of cone angle in alumina tiles under ballistic impact

The ceramic cone formed within the ceramic tiles provides effective ballistic resistance. Although the critical velocity of ceramic cone formation has been extensively studied, the cone angle in ceramic tiles after crack initiation is still unclear, which is important for understanding the anti-penetration process. In this paper, the cone angle in ceramic tiles is systematically investigated both experimentally and theoretically. First, the dynamic failure process of ceramic tiles is characterized by means of ballistic impact experiments, and the results show that the cone angle gradually decreases with the increase of the thickness of the ceramic tile, while it is independent of the impact velocity. Then, based on the minimization of deformation energy and fracture energy, a theoretical model is established for the first time to predict the cone angle, which takes into account the strain rate effect on tensile strength. This model can well explain the effect of the thickness, impact velocity and fracture properties of the ceramic material on the cone angle obtained in experiments. Increasing the thickness of the ceramic tiles results in larger ceramic fragments while the generated fracture energy declines. This leads to a decrease in the cone angle. Moreover, an increase in the fracture toughness or tensile strength of the ceramic material enhances the resistance to crack propagation, and the generated fracture energy decrease, resulting in a decrease in the cone angle. However, the cone angle does not change much with impact velocity because the impact velocity does not change the stress field distribution of the ceramic tile. This study is meaningful for understanding the ballistic resistance of ceramic tiles.

Gradient failure mechanism and control technology of deep roadways under the action of deviatoric stress field

Deformation control of deep roadways is a major challenge for mine safety production. Taking a deep roadway with a burial depth of 965 m in a mine in North China as the engineering background, on-site investigation found that significant creep deformation occurred in the surrounding rock of the roadway. The original supporting U-shaped steel support failed due to insufficient supporting strength. The rock mass near the roadway experienced a transition from triaxial stress conditions to biaxial and even uniaxial stress states as a result of excavation and unloading, leading to a gradient stress distribution in the surrounding rock. From the perspective of the roadway's deviatoric stress field distribution, we investigated the gradient failure mechanism of the roadway and validated it through theoretical analysis and numerical simulations. The study found that the ratio of horizontal principal stress and vertical principal stress determines the distribution shape of the surrounding rock deviatoric stress field. The gradient distribution of the stress field in the roadway will cause time-related deformation of the roadway, which will lead to large deformation and failure of the roadway. Based on this, the control mechanism of roadway gradient failure was studied, and then a combined support technology of CFST supports with high bearing capacity was proposed.

Image driven deep learning method with FFT solver for predicting the microscale full field stress of stochastic boundary composites

AbstractA novel image‐driven deep learning approach embedded with model‐data‐knowledge information can directly predict the full field stress distribution and mechanical properties of composites solely based on initial scanning geometry images. The fiber spatial distribution and morphological features are identified by Scanning Electron Microscopy (SEM) initially. An effective random fiber generation algorithm is further utilized to generate images database comprising equivalent geometric models of various microstructures. Subsequently, the geometry model images database is analyzed by fast Fourier transform (FFT) to produce the database including the elastic modulus parameters and full field stress distributions of composites with distinct microstructures. Finally, an innovative image‐learning comprehensive paradigm uniting convolutional neural networks and convolutional autoencoders is elaborated systematically to learn the inherent laws of geometry images and field images. The results show that the proposed method have capacity to effectively and accurately predict the elastic modulus and full field stress distributions combined with error analysis even for stochastic boundary composites. The proposed methodology is a symbiosis of cutting‐edge image learning and non‐destructive testing techniques for composites, which can directly use the local non‐destructive or scanning images of composite structural components to quickly obtain field information and further predict damage evolution online.Highlights Proposing a novel deep learning approach combined with FFT directly to predict stress distribution of stochastic boundary composites solely based on micro‐images. Adopting equivalent geometric models dispersed by higher pixels mesh density considering extreme thin interface. Incorporate adaptive algorithms for streamlined training optimization. An innovative integration of deep learning and non‐destructive testing technology for the stress distribution and properties prediction online.