Deformation Conditions Research Articles

Real-Time Simulation of Tube Hydroforming by Integrating Finite-Element Method and Machine Learning

The real-time, full-field simulation of the tube hydroforming process is crucial for deformation monitoring and the timely prediction of defects. However, this is rather difficult for finite-element simulation due to its time-consuming nature. To overcome this drawback, in this paper, a surrogate model framework was proposed by integrating the finite-element method (FEM) and machine learning (ML), in which the basic methodology involved interrupting the computational workflow of the FEM and reassembling it with ML. Specifically, the displacement field, as the primary unknown quantity to be solved using the FEM, was mapped onto the displacement boundary conditions of the tube component with ML. To this end, the titanium tube material as well as the hydroforming process was investigated, and a fairly accurate FEM model was developed based on the CPB06 yield criterion coupled with a simplified Kim–Tuan hardening model. Numerous FEM simulations were performed by varying the loading conditions to generate the training database for ML. Then, a random forest algorithm was applied and trained to develop the surrogate model, in which the grid search method was employed to obtain the optimal combination of the hyperparameters. Sequentially, the principal strain, the effective strain/stress, as well as the wall thickness was derived according to continuum mechanics theories. Although further improvements were required in certain aspects, the developed FEM-ML surrogate model delivered extraordinary accuracy and instantaneity in reproducing multi-physical fields, especially the displacement field and wall-thickness distribution, manifesting its feasibility in the real-time, full-field simulation and monitoring of deformation states.

Structure and Mechanical Properties of AlMgSi(Cu) Extrudates Straightened with Dynamic Deformation.

Before artificial ageing, extruded aluminium profiles are subjected to stretching with a small cold deformation in the range of 0.5-2%. This deformation improves the geometrical stability of the extruded product and causes changes in the microstructure of the profile, which leads to the strain hardening of the material after artificial ageing. The work has resulted in the creation of the prototype of an original device, which is unique in the world, for the dynamic stretching of the extruded profiles after quenching. The semi-industrial unit is equipped with a hydraulic system for stretching and a pneumatic system for cold dynamic deformation. The aim of this research paper is to produce advantageous microstructural changes and increase the strength properties of the extruded material. The solution of the dynamic stretching of the profiles after extrusion is a great challenge and an innovation not yet practised. The paper presents the results of microstructural and mechanical investigations carried out on extruded AlMgSi(Cu) alloys quenched on the run-out table of the press, dynamically stretched under different conditions, and artificially aged for T5 temper. Different stretching conditions were applied: a static deformation of 0.5% at a speed of 0.02 m/s, and dynamic deformation of 0.25%, 0.5%, 1%, and 1.5% at speeds of 0.05 and 2 m/s. After the thermomechanical treatment of the profiles, microstructural observations were carried out using an optical microscope (OM) and a scanning electron microscope (SEM). A tensile test was also carried out on the specimens stretched under different conditions. In all the cases, the dynamically stretched profiles showed higher strength properties, especially those deformed at a higher speed of 2 m/s, where the increase in UTS was observed in the range of 7-18% compared to the classical (static) stretching. The microstructure of the dynamically stretched profiles is more homogeneous with a high proportion of fine dispersoids.

N-level complex helical structure modeling method

This paper primarily explores the modeling method of n-level complex helical structures with coal mining machine cables as the research object. The paper first elaborately introduces the modeling method of n-level helix curves based on parametric equations and coordinate transformations, and compensates for the n-level helix curves with corrected pitch, which can obtain more accurate n-level helix curves and improve the accuracy of n-level helix curves modeling. Subsequently, based on this high-precision n-level helix curves modeling method, the paper elaborates on the method of solving pitch and twisting radius of multi-layer helical structure. Calculation scripts were written based on the above methods, which can be used to batch calculate the twisting radius and pitch of each layer structure in multi-layer structures when satisfying the conditions of in-layer tangency, inter-layer tangency, and extrusion deformation, and retain the actual results through logical judgment. Then, based on the above two methods, the paper developed a modeling method for braided structures based on piecewise functions containing fifth-order polynomials, which can effectively avoid the problem of insufficiently dense arrangement of braided lines and easy interference in traditional methods. Finally, a set of modeling tools was developed using C# and Python in Grasshopper to implement the modeling algorithm. Taking the MCPT-1.9/3.3 3120 + 170 + 4 * 10 coal mining machine cable as an example. The cable was modeled using both the method proposed in this paper and the traditional method. Comparative data shows that the method proposed in this paper can reduce errors by 3.31E6 times in the second-level and above helical structures. In addition this paper compares the standard line length, measured line length, and the line length established by the proposed model, showing that the relative errors are both less than 0.1941%. This paper provides a new, systematic, high-precision, and full-process cable modeling method, in which all parameters except the process parameters are accurately solved by equations. It lays a theoretical foundation for the high-precision simulation and intelligent sensing cables, which is of great significance for improving the safety, stability, and efficient development of the coal mining industry. The research results of the paper can not only be applied to the modeling of coal mining machine cables but also can be extended to the modeling of other complex multi-layer helical structures.

Hot Deformation Characteristics and Dynamic Recrystallization Mechanisms of a Semi-Solid Forged AZ91D Magnesium Alloy.

Magnesium alloys show great promise in high-speed transport, aerospace, and military technology; however, their widespread adoption encounters challenges attributed to limitations such as poor plasticity and strength. This study examines the high-temperature deformation of semi-solid forged AZ91D magnesium alloy through a combination of experiments and simulations, with a focus on comprehending the influence of deformation conditions on dynamic recrystallization (DRX). The findings disclose that conspicuous signs of DRX manifest in the yield stress curve as strain increases. Additionally, decreasing the strain rate and temperature correlates with a reduction in both yield stress and peak strain, and the activation energy is 156.814 kJ/mol, while the critical strain and peak strain remain relatively consistent (εc=0.66208εp). Microstructural changes during high-temperature deformation and the onset of DRX are thoroughly examined through experimental methods. Moreover, a critical strain model for DRX and a predictive model for the volume fraction of DRX were formulated. These equations and models, validated through a combination of experiments and simulations, serve as invaluable tools for predicting the mechanical behavior and microstructural evolution, which also establishes a foundation for accurately predicting the deformation behavior of this alloy. By analyzing the hot deformation characteristics and dynamic compression mechanism of the newly developed semi-solid forging AZ91D magnesium alloy, a numerical simulation model can be effectively established. This model objectively reflects the changes and distributions of stress, strain, and rheological velocity, providing a scientific basis for selecting subsequent plastic deformation process parameters and designing mold structures.

A method to represent the strain hardening effect in the hyper-elastic model within a fully Eulerian framework

We propose a method to treat the strain hardening effect in the hyperelastic model. Coupled with the level set interface capturing method and a real ghost fluid method, it is formulated in a fully Eulerian framework. The HLLD approximate Riemann solver is used to obtain the interface state. We use the elastic inverse deformation gradient tensor to track the material deformation state. Once the solid starts to yield, along the normal direction in stress space, an iterative algorithm is used to relax the elastic inverse deformation gradient tensor to target value where the equivalent stress meets the requirement of consistency condition in plasticity. This approach is intuitive and can avoid the use of the physical delay time, which is difficult to calibrate from experiments. We use the Wilkins flying plate impact, cylindrical shell collapse, Taylor impact and the conical-nosed projectile penetration test cases to validate the method. The results show good agreement with the theoretical analysis and experiments. This approach can also apply without further extension when thermal softening effect or damage models are considered.

Compatibilization of Polymer Blends under Conditions of High Pressure and Shear Deformation

AbstractStructural changes in polylactide/polybutylene terephthalate (PLA/PBT) and glycol‐modified polyethylene terephthalate/polybutylene terephthalate (PET‐G/PBT) polymer blends at a pressure of 1 GPa and room temperature in combination with shear deformation are investigated. High pressure torsion (HPT) is chosen as the compatibilization technique. Based on solid‐state NMR data, it is found that the compatibility of immiscible polymers is significantly improved under high pressure conditions in combination with shear deformation. It is assumed that the thickness of the deformed polymer layers decreases to the thickness of the interphase and it can be a fully interphase material.

Increasing the strength of potato digger elevator rods

Abstract Currently, high-quality steels are used to increase the reliability of potato digging machines and the durability of elevator rods. Recently, new materials, new technologies and non-metallic materials that are not inferior in strength to steel have been used in agricultural machines. Such materials significantly reduce the mass of the working parts. This article examines the deformation of a new elevator rod design due to the action of soil and tuber-bearing mass. The rods, covered with double-cavity rubber profiles, vibrate the component of the potato heap. During vibrations, in addition to static deformations, dynamic deformations occur, depending on the magnitude of the impact force. As a result, it was found that to eliminate the loss of tubers between the bars of the separating elevator, given the maximum deflection value of 0.03 m and the weight of the soil-tuber-bearing mass, the rubber bar must have the following parameters: elasticity model E = 50 N/mm2; rod perimeter 11x11 mm; the maximum jump height of a mass weighing 130 kg is no more than 0.6 m.

A multi-mode stretching apparatus for in situ synchrotron x-ray scattering of polymer materials.

A compact and versatile tensile apparatus for polymer materials is designed and fabricated. Three distinct stretching modes are developed: constant speed, cyclic, and sinusoidal, with adjustable speeds ranging from 0.001 to 120 mm/s. To capture the true strain of the central region, a high-speed camera has been integrated into the apparatus. The temperature of the sample chamber is controlled by flowing air, enabling a homogeneous temperature in the range of RT ∼200 °C. The apparatus is particularly suitable for a synchrotron beamline. The structural evolution of natural rubber during sinusoidal stretching is investigated by in situ wide-angle x-ray scattering. Scattering patterns, force, clamp position, and sample images are saved simultaneously during stretching. Notably, the results reveal a sinusoidal variation in the crystallinity of crosslinked natural rubber when a sinusoidal strain was applied to the sample. The integration of advanced measurement techniques and controlled experimental conditions ensures the acquisition of reliable and accurate data, providing valuable insights into the structural evolution of materials under dynamic deformation conditions.

On the contact of an absolutely rigid stamp with a half-plane taking into account static friction

Abstract The plane deformable state of an elastic half-plane into which an absolutely rigid stamp is pressed with friction is considered. It is assumed that the tangential stresses acting in the contact zone are related to normal pressure by the law of dry friction, the coefficient of which is a linear function of the coordinate of the contacting points of the contacting bodies. A determining singular integral equation for the stated problem is obtained, the solution of which is constructed in closed form. Numerical analysis is conducted, and regularities in the variation of contact stresses are determined depending on the ratios of horizontal and normal loads applied to the stamp.

Study of the Generalized Curves of the Static and Cyclic Deformation, Damage, and Fracture

Study of the Generalized Curves of the Static and Cyclic Deformation, Damage, and Fracture

Major depressive disorder elevates the risk of dentofacial deformity: a bidirectional two-sample Mendelian randomization study.

The association between psychiatric disorders and dentofacial deformities has attracted widespread attention. However, their relationship is currently unclear and controversial. A two-sample bidirectional MR analysis was performed to study the causal relationship between dentofacial deformity and eight psychiatric disorders, including major depressive disorder, panic disorder, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, Alzheimer's disease, autism spectrum disorder, and neuroticism. Inverse variance weighted, weighted median, MR-Egger regression, weighted mode four methods, and further sensitivity analyses were conducted. The major depressive disorder affected dentofacial deformity, with an OR = 1.387 (95% CI = 1.181-1.629, P = 6.77×10-5). No other psychiatric disorders were found to be associated with dentofacial deformity. In turn, dentofacial deformity were associated with neuroticism, with an OR = 1.050 (95% CI = 1.008-1.093, P = 0.018). And there was no evidence that dentofacial deformity would increase the risk of other psychiatric disorders. Major depressive disorder might elevate the risk of dentofacial deformities, and dentofacial deformity conditions would increase the risk of the incidence of neuroticism.

Full Picture of Lattice Deformation in a Ge1 - xSnx Micro-Disk by 5D X-ray Diffraction Microscopy.

Lattice strain in crystals can be exploited to effectively tune their physical properties. In microscopic structures, experimental access to the full strain tensor with spatial resolution at the (sub-)micrometer scale is at the same time very interesting and challenging. In this work, how scanning X-ray diffraction microscopy, an emerging model-free method based on synchrotron radiation, can shed light on the complex, anisotropic deformation landscape within three dimensional (3D) microstructures is shown. This technique allows the reconstruction of all lattice parameters within any type of crystal with submicron spatial resolution and requires no sample preparation. Consequently, the local state of deformation can be fully quantified. Exploiting this capability, all components of the strain tensor in a suspended, strained Ge1 - xSnx /Ge microdisk are mapped. Subtle elastic deformations are unambiguously correlated with structural defects, 3D microstructure geometry, and chemical variations, as verified by comparison with complementary electron microscopy and finite element simulations. The methodology described here is applicable to a wide range of fields, from bioengineering to metallurgy and semiconductor research.

Investigation of constitutive models and microstructure evolution during hot deformation and solution treatment of Al–Zn–Mg–Cu alloy

In this paper, isothermal thermal compression tests were carried out on Al–Zn–Mg–Cu alloys at varying deformation temperatures (360°C∼440°C) and strain rates (0.001s−1∼10s−1) using a Gleeble-3500C thermal simulation tester. Based on the true strain stress data obtained from the tests, the flow behavior of Al–Zn–Mg–Cu alloys during thermal deformation was investigated. Through a comprehensive consideration of deformation temperature, strain rate, and strain compensation, a high-precision constitutive model was established. Additionally, the specimens subjected to hot compression were further treated with solution annealing for different durations (0 h–2 h) to investigate the static recrystallization (SRX) behavior and the associated microstructural evolution of the alloy during the solution treatment process. Electron Backscatter Diffraction (EBSD) was employed to characterize the microstructure evolution of Al–Zn–Mg–Cu alloy under various deformation and solution treatment conditions. The EBSD data were further processed and analyzed using the MTEX toolbox. The results revealed that dynamic recovery (DRV) is the predominant softening mechanism during the deformation process, accompanied by a small amount of dynamic recrystallization (DRX). The dynamically recrystallized grains exhibit a random crystallographic orientation. Further investigation showed that low temperature and high strain rate conditions are unfavorable for the occurrence of dynamic recovery and dynamic recrystallization during the thermomechanical processing. However, dislocations accumulated during deformation provided sufficient stored energy for the growth of static recrystallized grains during subsequent solution treatment, with static recrystallized grains predominantly forming at grain boundaries.

Cellulose nanocrystals built multiscale hydrogel electrolyte for highly reversible all-flexible zinc ion batteries

Hydrogel electrolytes are promising for flexible and stable zinc ion batteries (ZIBs), but they lack fatigue resistance and still face challenges in terms of mechanical stability and durability. Herein, inspired by the hierarchical structure of biological networks, multiscale anti-fatigue hydrogel electrolytes with high toughness, high strength, and rapid recovery are constructed by introducing nanoscale cellulose nanocrystals (CNCs) as building blocks into dual-network cross-linking hydroxypropyl chitosan (HPCS) modified polyacrylamide (PAM) hydrogel (denoted as PHC-gel). As a result, the PHC-gel achieves a high fatigue threshold up to 356 J m−2 and with a superior strength and stretchability up to 180 kPa and 3178 %, respectively. In addition, the assembled Zn//Zn cell exhibits long-term cycling stability of 1800 h at 1 mA cm−2/1 mAh cm−2 with a high Coulombic efficiency of 99.4 %. More importantly, the Zn//PHC-gel//MnO2 flexible cell shows remarkable flexibility and capacity retention under different stretching and deformation conditions. This work demonstrates a promising gel chemistry that improves anti-fatigue properties and controls zinc behavior, offering great potential for high-performance flexible and wearable ZIBs and beyond.

Elastic Property Evaluation of Fiberglass and Epoxy Resin Composite Material Using Digital Image Correlation.

This study focused on evaluating the sensitivity and limitations of the simplified equipment used in the Digital Image Correlation (DIC) technique, comparing them with the analog extensometer, based on the mechanical property data of a composite made of fiberglass and epoxy resin. The objectives included establishing a methodology based on the literature, fabricating samples through manual lamination, conducting mechanical tests according to the ASTM D3039 and D3518 standards, comparing DIC with the analog extensometer of the testing machine, and contrasting the experimental results with classical laminate theory. Three composite plates with specific stacking sequences ([0]3, [90]4, and [±45]3) were fabricated, and samples were extracted for testing to determine tensile strength, modulus of elasticity, and other properties. DIC was used to capture deformation fields during testing. Comparisons between data obtained from the analog extensometer and DIC revealed differences of 11.1% for the longitudinal modulus of elasticity E1 and 5.6% for E2. Under low deformation conditions, DIC showed lower efficiency due to equipment limitations. Finally, a theoretical analysis based on classical laminate theory, conducted using a Python script, estimated the longitudinal modulus of elasticity Ex and the shear strength of the [±45]3 laminate, highlighting a relative difference of 31.2% between the theoretical value of 7136 MPa and the experimental value of 5208 MPa for Ex.

Transfer learning-based Gaussian process classification for lattice structure damage detection

This study presents a novel approach for real-time vision-based structural health monitoring, focusing on evaluating the deformation state of lattice structures. The structures are renowned for their remarkable recovery capabilities and exhibit similar mechanical responses under compressive loads. Despite these characteristics, quickly assessing the health status of the applied structure using knowledge from another related lattice structure is usually time-consuming and impractical. To address this, we propose to combine Gaussian process classification with transfer learning, termed TL-GPC, to detect damage states under compressive loads while also achieving uncertainty quantification. By employing structural deformations captured via the optical flow algorithm as inputs, the internal transfer kernel factor in TL-GPC is tailored to model knowledge transfer between source and target domain inputs. Experimental results show that the proposed TL-GPC model can deliver higher damage detection accuracy while ensuring stable uncertainty quantification in scenarios with limited and unbalanced experimental data.

Modal analysis of taipei 101 building

In this paper, a multi-stage modeling and simulation approach incorporating different deformation conditions is used to analyze the structure of the Taipei 101 building. The modeling process mainly involves the formation of an initial simplified model based on the basic geometry, the determination of an accurate model based on the actual dimensions, and finally the introduction of a hollow structure design to mimic the density and mass distribution of the real building. After the model is established, mesh creation and mesh independence study are carried out. The simulation is carried out using Ansys software, which mainly performs the process of selecting boundary conditions, determining the equivalent density, dividing the mesh for modal analysis, and obtaining the modal vibration pattern as well as the corresponding intrinsic frequency. By analyzing the intrinsic frequencies and vibration modes, the structure of Taipei 101 Building is prone to resonance under certain circumstances, and this study provides some significance to the geology of local seismic activities.

Hot deformation and dynamic recrystallization of Mg-Gd-Y-Zn-Zr alloy containing high volume fraction 18R-LPSO phase

The deformation behavior including flow behavior, hot workability and dynamic recrystallization (DRX) mechanism of as-cast Mg-9Gd-3Y-3.75Zn-0.6Zr alloy containing 26.5 % volume fraction 18R long-period stacking ordered (LPSO) phase distributed in continuous network morphology were studied by hot compression experiments at deformation condition of 350 ℃-500 ℃, 0.01–1 s−1 strain rate and 0.75 true strain. The influence of deformation conditions on the microstructural evolution was analyzed by using optical microscopy (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscope (TEM). Results display that stress exponent and deformation activation energy are 5.58 and 241.39 kJ·mol−1 correspondingly, which suggested that dislocation climb is the principal deformation mechanism. The Arrhenius type constitutive equation is established as ε̇=4.09×1016sinh(9.922×10−3σ)5.58exp(−241394RT). Microstructure evolution can be characterized by Zener-Holomon parameter (Z) which reflects the combining effect of temperature and strain rate on microstructure. At low lnZ (lnZ<36), the 18R-LPSO phase dissolves from continuous network to blocks and high DRX volume (>50 %) is realized by particle-stimulated nucleation and discontinuous dynamic recrystallization. At moderate lnZ (36≤lnZ<40), a fine and coarse grains bimodal structure is formed at the original grain boundary by continuous dynamic recrystallization resulting in a DRX volume between 10 % and 50 %. At high lnZ (lnZ≥40), layered 14H‐LPSO phase precipitates and inhibits DRX (DRX volume＜10 %) by absorbing dislocations. With combination of dissipation coefficient, instability factor and microstructure analysis, 400 ℃/0.01–0.05 s−1 and 450 ℃/0.01 s−1 are confirmed as optimal hot working domains for the as-cast alloy, under which conditions bimodal microstructure and equiaxed grains microstructure (average grain size 10.3 μm) can be formed correspondingly.

Prediction on the time-varying behavior of tunnel segment gaskets under compression

The compression force is a critical indicator for assessing the waterproofing capability of ethylene propylene diene monomer (EPDM) rubber gaskets, and the relaxation of EPDM gaskets under compression is a key factor contributing to water leakage in shield tunnels. In this study, detailed accelerated aging tests of gaskets with different precompression openings were conducted. Analytical method and simulation method for predicting the long-term performance of EPDM gaskets considering their different compression states were proposed. First, the compression curve of the gasket was divided into three stages to analyze the mechanism of compression force degradation in depth. Under the action of a compression force, the unrecoverable deformation caused by open holes shortened stage III of the compression curve, which constituted the primary factor influencing gasket compression force relaxation. In addition, the Arrhenius equation was used to establish a conversion relationship between the accelerated aging test conditions and actual service time, and an analytical expression (AE) method for predicting the compression force degradation pattern of gaskets was proposed. Finally, a finite element (FE) method based on the relaxation constitutive model was proposed, enabling simulation of deteriorating tunnel segment gasket performance under complex compression states. Then, the effectiveness and accuracy of the proposed relaxation model were validated by comparing the compression force curves and deformation states obtained from experiments and simulations. Based on the time-varying relaxation constitutive parameters, the variation in the compression force of EPDM gaskets with different joint openings over time was simulated. The results show that the minimum compression force retention rates of gaskets after 100 years of service predicted by the AE method and FE method are 28.5 % and 30.6 %, respectively. This study provides two effective means for predicting the long-term mechanical performance of compressed EPDM gaskets, offering pivotal insights for long-term waterproofing design of shield tunnel joints.

Research on the Dynamic Softening Mechanism of Dual‐Phase Structure During Warm Forming of Fe–8.5Mn–1.5Al Medium‐Manganese Steel

In this article, Fe–8.5Mn–1.5Al medium‐manganese steel is taken as the research object, and Gleeble 3500 thermal simulation testing machine is used to conduct isothermal compression at different deformation temperatures, strain rates, and strains in its austenite ferrite two‐phase zone. A constitutive model and a dynamic recrystallization volume fraction model for materials are established, and finite‐element method is used to simulate the temperature, equivalent strain, and dynamic recrystallization volume fraction distribution in different regions of the workpiece under different deformation conditions. By comparing and analyzing the microstructure, finite‐element simulation results, and hot working diagrams obtained from the experiment, the microscopic mechanism of dynamic softening of the material when ferrite and austenite coexist is explained; the transformation of the dynamic softening mechanism of the two phases with the hot deformation process is also explained. Early deformation mainly occurs in softer ferrite, which preferentially undergoes continuous dynamic recrystallization. Austenite has a lower stacking fault energy, and discontinuous dynamic recrystallization (DDRX) occurs when the dislocation density reaches a certain critical value. At the same time, when the strain reaches a certain level, the dynamic softening behavior of ferrite will also transform into DDRX. The optimal deformation conditions for Fe–8.5Mn–1.5Al medium‐manganese steel during warm processing in the two‐phase zone are a temperature of 720 °C, a strain rate of 0.01 s−1, and a large deformation zone.