Coupled Finite Element Analysis Research Articles

Coupled thermomechanical finite element analysis of ultrasonic hot embossing process

Ultrasonic Hot Embossing of polymers is one of the most attractive manufacturing methods of high-quality and complex microparts needed for biological and chemical processes. A little simulation work has been done to study the deformation mechanism and the required load in the Ultrasonic Hot Embossing of polymethyl methacrylate (PMMA). This paper developed a 2D coupled thermo-mechanical finite element model to simulate the forming behavior of the ultrasonic embossing process of PMMA, optimize the mold microfeature corner, and predict the embossing load as well. VDISP ABAQUS subroutine has been used to describe the downward motion of the mold assisted with ultrasonic vibration. The Arbitrary Eulerian-Lagrangian re-meshing technique has been implemented to refine the deformation zone during simulation to avoid divergence due to localized excessive deformation. Embossing load, temperature, stresses, strains, and energy dissipation have been recorded and analyzed. Simulation results revealed that the coupled thermo-mechanical FE Model efficiently captures the deformation behavior and Embossing load. It also proved that a Mold microfeature corner of 20 μm filet radius is recommended to adequately fill out the area around the mold and maintain uniform temperature and strain distributions.

Fluid-solid coupling model and analysis on pulse wave propagation properties of iliac artery

In this work, we investigated the influence of the bifurcation geometry of the iliac artery on the propagation properties of the pulse wave, and applied software to establish the straight bifurcation and curved bifurcation bi-directional fluid-solid coupling finite element analysis models based on the iliac artery, and compared and analyzed the influence of the bifurcation angle of the blood vessel on the propagation characteristics of the pulse wave. It was found that the bifurcation geometry had a significant effect on the pulse wave propagation in the iliac arteries, and the pressure and velocity pulse wave amplitudes predicted by these two models had a good agreement with that before the vessel bifurcation in a cardiac cycle. The curvilinear bifurcation model predicted the pulse wave amplitude to be lower and the pressure drop to be smaller after the bifurcation, which was more in line with the actual situation of the human body. In addition, the bifurcation point is accompanied by the stress concentration phenomenon in the vessel wall, and there is a transient increase in the velocity pulse waveform amplitude, which was consistent with the fact that the bifurcation site is prone to phenomena such as arterial stenosis and hardening. The preliminary results of this paper will provide some reference for the use of pulse waveforms in the diagnosis of arterial diseases.

Nanocarbon-enabled mitigation of sulfur expansion in lithium–sulfur batteries

Significant lithiation-induced sulfur expansion hinders the development of commercial lithium–sulfur (Li–S) batteries, highlighting a pressing need to comprehend the sulfur lithiation mechanism. Coupled molecular dynamics (MD) and finite element analysis (FEA) simulations were used to unveil the chemo-mechanics of rate-dependent sulfur anomalous volumetric changes. The lithiation-induced sulfur transition was found to proceed in four stages, ranging from sulfur lithiation to the formation of Li2S. Lithiation induced sulfur swelling and shrinking, which were accompanied by increased and decreased lithiation stresses, respectively. Although the precipitation of Li2S4, Li2S2, and Li2S resulted in partial lithiation of the sulfur, the formation of these precipitates in turn buffered sulfur expansion by 48.64 %. A high current density was able to mitigate lithiation-induced sulfur expansion with trade-off in battery-specific capacity degradation. Nanocarbons, characterized by high porosity and outstanding mechanical properties, were robust enough to guide sulfur expansion along their open ends, thus effectively buffering sulfur volume change. Our findings provide a new mechanism for previously unexplained experimental observations, advance the understanding of sulfur expansion-caused cathode deterioration, and offer a new design guideline for high-performance Li–S batteries.

Analysis of pulse-wave propagation characteristics in abdominal aortic sclerosis disease

In this work, a bidirectional fluid‒structure coupling finite element analysis model of the abdominal aorta was established with the various vascular elastic modulus as the main parameter of atherosclerosis, in consideration of blood dynamic viscosity and compressibility. Pressure and velocity pulse-wave propagation were investigated by the application of full-coupling analysis algorithm. The effect of atherosclerosis degree on the propagation characteristics of pulse waves in the bifurcated abdominal aorta was quantitatively analyzed. Arterial bifurcation can cause a substantial attenuation on the peak of pressure pulse waveform and an increase in wave velocity during the cardiac cycle. The elastic modulus and bifurcation properties of the arterial wall directly affected the peak value and wave propagation velocity of the pressure pulse wave. The preliminary results of this work will be crucial in guiding the evolution of the pressure pulse wave and the initial diagnosis of atherosclerotic disease through the waveform.

Exploring the Influence of Climate Change on Earthen Embankments with Expansive Soil

Climate change is known to cause alterations in weather patterns and disturb the natural equilibrium. Changes in climatic conditions lead to increased environmental stress on embankments, which can result in slope failures. Due to wetting–drying cycles, expansive clayey soil often swells and shrinks, and matric suction is a major factor that controls the behavior. Increased temperature accelerates soil evaporation and drying, which can cause desiccation cracks, while precipitation can rapidly reduce soil shear strength. Desiccated slopes on embankments built with such soils can cause surficial slope failures after intense precipitation. This study used slope stability analysis to quantify how climate-change-induced extreme weather affects embankments. Historic extreme climatic events were used as a baseline to estimate future extremes. CMIP6 provided historical and future climatic data for the study area. An embankment was numerically modeled to evaluate the effect on slope stability due to the precipitation change induced by climate change. Coupled hydro-mechanical finite element analyses used a two-dimensional transient unsaturated seepage model and a limit equilibrium slope stability model. The study found that extreme climatic interactions like precipitation and temperature due to climate change may reduce embankment slope safety. The reduction in the stability of the embankment due to increased precipitation resulting from different greenhouse gas emission scenarios was investigated. The use of unsaturated soil strength and variation of permeability with suction, along with the phase transition of these earthen embankments from near-dry to near-saturated, shows how unsaturated soil mechanics and the hydro-mechanical model can identify climate change issues on critical geotechnical infrastructure.

Coupled Finite Element and Artificial Neural Network Analysis of Interfering Strip Footings in Saturated Cohesive Soils

Coupled Finite Element and Artificial Neural Network Analysis of Interfering Strip Footings in Saturated Cohesive Soils

Numerical calculation and analysis of temperature field in ultrasonic welding of polypropylene dialyzer

Ultrasonic plastic welding is widely used in the bonding process of medical device accessories. In this paper, a thermo-force indirect coupling finite element analysis model was established in the ultrasonic plastic welding process between the blood cap and the shell of polypropylene (PP) dialyzer. The temperature field distribution between the blood cap and the shell was simulated and analyzed by using finite element analysis software, and the influence of welding process parameters on the temperature field was studied. The results show that: by changing the ultrasonic amplitude parameters, welding time parameters, initial pressure, etc., the longer the ultrasonic welding time, the temperature of the welding area will increase. In order to ensure the quality of the dialyzer, it should be controlled within 0.8-1 seconds. The increase of ultrasonic amplitude will make the welding temperature continue to rise, and in order to avoid poor welding, the amplitude should not exceed 120 ?m. The initial pressure has little effect on the temperature field.

Fast Calculation of Electromagnetic Vibration of Surface-Mounted PMSM Considering Teeth Saturation and Tangential Electromagnetic Force

In view of the shortcomings of the existing calculation methods of electromagnetic forces, this paper proposes an analytical method (AM) combining the magnetomotive force (MMF)-permeance method and the improved subdomain method. The amplitude of each force density component considering stator teeth saturation and current harmonics is calculated, and the specific order and frequency components in the radial and tangential electromagnetic force densities are analyzed and sorted out. In modal analysis, the stator core and the casing are regarded as cylindrical shells with axial ribs, the natural frequencies of the stator are obtained based on the energy method, and the accuracy is well verified by the modal test. Finally, the frequency response functions of low-order modes of the stator only related to the stator structure parameters are determined, and the vibration accelerations under different working conditions are obtained based on the linear superposition principle by only updating the electromagnetic forces. Compared with the multi-physical coupling finite element analysis, the total calculation time of the proposed AM is reduced by more than 92%, which facilitates the fast prediction and effective reduction of electromagnetic vibrations in the motor design stage.

Modeling of interfacial void closure and prediction of bonding time in solid-state diffusion bonding

An analytical model of the void closure during diffusion bonding was established by coupling finite element analysis (FEA) based on the deformation mechanism and numerical analysis based on the diffusion mechanism. The maximum stress was concentrated at the tip of the microconvex in contact with the bonding interface. With increasing bonding temperature and pressure, the stress concentration region moved from the tip of the microconvex region to the void neck region. The stress distribution was concentrated on the tip of the microconvex region (void neck region) to the opposite direction of the applied bonding pressure. Using the model, the characteristic time parameter (time constant) tc was defined based on the evolution of the void closure. At this moment, the predicted bonded ratio was the sum of (1 −1/e) times the normal limit bonded ratio and 1/e times the normal initial bonded ratio. Furthermore, a model for predicting the bonding time was established by coupling the required bonded ratio and the limitation of the deformation rate, the model can be used to predict the bonding time within the operation window. Contour maps of time constant (tc/min) and the nominal limit bonded ratio (fult/%) were constructed for visual representation.

Modeling De-Coring Tools with Coupled Multibody Simulation and Finite Element Analysis

De-coring is an essential process in the casting process chain, determining the quality and cost of production. In this study, a coupled multibody system (MBS) and finite element modeling (FEM) technique is presented to study the mechanical loads during the de-coring process. The removal of cast-in sand cores from the inner regions of the cast part by de-coring or knocking out is a complex process with dynamic loads. Currently, the process relies upon empirical knowledge and tests. Inorganic sand cores pose additional challenges in the success of the de-coring process. Increasing complexity in geometry and stringent environmental regulations compel a predictive process in the earlier stages of design. Predicting the process’ success is challenged by the dynamic non-linearities of the system. The dynamic characteristics and the interaction between hammer and casting were studied here for the first time using an industrial-based test rig, and a novel modeling approach was formulated. The results of the developed model are in good compliance with the experiments. The methodology presented in this study can be used to include a varying number of hammers and loads. The proposed approach presents the possibility to discretize the process and qualitatively assess the process parameters for optimization.

DLP printing of BT/HA nanocomposite ceramic scaffolds using low refractive index BT crystals

Biological piezoelectric materials have significant potential for bone repair and energy harvesting owing to their excellent biocompatibility and piezoelectric effect. The BaTiO3/Ca10(PO4)6(OH)2 (BT/HA) composite material is an outstanding representative of biological piezoelectric materials, which has not been individually designed using digital light processing (DLP) 3D printing because of the large difference in the refractive index of its components. Therefore, in this work, double-sided-tooth plate-like BT crystals with high curvature were prepared via a hydrothermal process, and BT/HA ceramic slurries were grinded out using dispersed intermittent ball milling scheme, and BT/HA nanocomposite ceramic scaffolds were fabricated by DLP 3D printing technology. The nanostructure, dielectric properties, and piezoelectric energy harvesting performance of the BT/HA nanocomposite ceramic scaffolds were evaluated. The influences of different morphologies and contents for BT on the piezoelectric potential and stress distribution were analyzed based on a multi-physics coupling finite element simulation. The cell proliferation and adhesion abilities were investigated also. The BT/HA nanocomposite ceramic scaffolds present excellent dielectric properties, cell proliferation and adhesion abilities, and an open circuit voltage of 8 V during piezoelectric energy harvesting. The material properties and multi-physics coupling finite element analysis imply that the double-sided-tooth plate-like BT plays an important role for the fastness structure and electric field distribution in the BT/HA nanocomposite. Thus, this work provides a strategy for the application of the customized BT/HA nanocomposite ceramic scaffolds in new-generation orthopedic implants and biological energy harvesting.

Analysis of Cooling Characteristics of Permanent Magnet Synchronous Motor with Different Water Jacket Design Using Electromagnetic–Thermal Fluid Coupled Analysis and Design of Experiment

Electrical losses are converted into thermal energy in motors, which heats each component. It is a significant factor in decreasing motor mechanical performance. In this paper, the motor cooling characteristics were analyzed according to the design factors of the water jacket to investigate the cooling performance of a permanent magnet synchronous motor (PMSM). First, the electrical losses generated in PMSM were calculated using electromagnetic finite element (FE) analysis. Secondly, a 3D electromagnetic–thermal fluid coupled FE analysis was performed to analyze the temperature distribution inside the motor by applying electrical loss as the heat source. Finally, the motor cooling performance according to the design factors of the water jacket was statistically analyzed using the design of experiment (DOE) method. It was found that the mass flow rate of 0.02547 kg/s and six passes of the water jacket with one inlet and two outlets could be considered the optimum conditions in terms of the maximum motor temperature.

A simple machine learning-based framework for faster multi-scale simulations of path-independent materials at large strains

Coupled multi-scale finite element analyses have gained traction over the last years due to the increasing available computational resources. Nevertheless, in the pursuit of accurate results within a reasonable time frame, replacing these high-fidelity micromechanical simulations with reduced-order data-driven models has been explored recently by the modelling community. In this work, two classes of machine learning models are trained for a porous hyperelastic microstructure to predict (i) whether the microscopic equilibrium problem is likely to fail and (ii) the stress–strain response. The former may be used to identify critical macroscopic points where one may fall back to the high-fidelity analysis and possibly apply convergence bowl-widening techniques. For the latter, both a linear regression with polynomial features and artificial Neural Networks have been used, and the required stress–strain derivatives for solving the equilibrium problem have been derived analytically. A weight regularisation is introduced to stabilise the tangent operator and several strategies are discussed for imposing null stresses in undeformed configurations for both regression models. The regression techniques, here analysed exclusively in the context of porous hyperelastic materials, evidence very promising prospects to accelerate multi-scale analyses of solids under large deformation.

The Optimization of Welding Spots’ Arrangement in A-Pillar Patchwork Blank Hot Stamping

With increasingly severe environmental problems, energy saving and environmental protection have become two important issues to be solved in the automobile industry. Patchwork blank hot-stamping technology can be used to obtain light-weight and high-strength parts and is thus increasingly used in the manufacture of autobody parts. Because the main blank and the patched blank need to be connected through spot welding before forming, the welding spots’ arrangement has a great influence on the formability of the part. In this study, a thermal–mechanical coupling finite element analysis model of A-pillar patchwork blanks was established. With the thickness of the patched blank, the distance between the welding spot and the external contour of the patched blank, and the number of welding spots as optimization variables, together with the maximum thinning rate and the maximum welding spot force as objectives, the influence of welding spot arrangement on forming quality was analyzed, and the welding spots’ arrangement was optimized using a central composite design (CCD), the response surface method (RSM), and the genetic algorithm (GA). The results showed that when the initial welding spot was located close to the contour of the patched blank, the bending moment was greater when the weld spot passed through the die corner, leading to the rupture of the welding spot or its surrounding base material due to the greater thinning rate. When the patched blank was thicker than the main blank, the main blank cracked during the forming process due to a greater increase in the thinning rate. The optimal solution of the weld spot arrangement on the A-pillar patchwork blanks was a 1.2 mm thick main blank, 0.8 mm thick patched blank, a distance of 29 mm between the weld spot and the contour line of the patched blank, and 16 weld spots. Hot-stamping experiments were conducted using the optimized weld spots’ arrangement, and high-quality parts were obtained.

Effects of Volute Structure on Energy Performance and Rotor Operational Stability of Molten Salt Pumps

A double-volute molten salt pump with two outlet pipes is proposed based on the original pump model. A numerical approach coupling finite element analysis and computational fluid dynamics (CFD) is implemented to investigate the operational stability and energy performance of two molten salt centrifugal pumps for high-temperature molten salt. The entropy production of the single-volute and double-volute molten salt pumps is investigated. The effects of the volute structures on the mechanical behavior of the impeller and shaft are considered. According to the findings, the local entropy production in the molten salt pump is dominated by the local pulsating entropy production (Spro-T), with the double-volute scheme achieving reduced energy loss. A visualization of the flow field and the local entropy production rate (LEPR) distributions indicate that the LEPR is positively correlated with the complexity of the flow, and higher levels of turbulence intensity lead to greater LEPR. The double-volute scheme enhances the complexity of the flow in the impeller, resulting in an increase in the LEPR compared with the single-volute design. However, the LEPR in the whole double-volute molten salt pump is reduced compared with the single-volute design. It is discovered that the double-volute molten salt pump experiences a less radial hydraulic force. Although the double-volute design has a slightly higher maximum equivalent stress on the impeller than the single-volute scheme, the rotor deformation is significantly less. In general, the double-volute scheme reduces energy loss and ensures better structural stability.

Aeroelastic analyses of functionally graded aluminium composite plates reinforced with graphene nanoplatelets under fluid-structural interaction

This study presents a comprehensive investigation on functionally graded (FG) graphene reinforced aluminium cantilever rectangular plates under aerodynamic loads. Two-way loosely coupled fluid structure interaction (FSI) is implemented by coupling finite element analysis (FEA) and computational fluid dynamics (CFD). FEA models are developed using FG graphene nanoplatelets (GPL) reinforced aluminium composite structures with different GPL distribution patterns. Fluid domain is modelled using finite volume method and FSI module is then used to connect FEA with the CFD code. The simulation results of FSI indicate that the maximum stress of the plate can be efficiently reduced with satisfactory aerodynamic performance after aeroelastic tailoring, depending on specific GPL distribution patterns. It is shown that in conjunction with aeroelastic tailoring technique, the composite plate can achieve optimized structural and aerodynamic performance. The present results of the FG graphene reinforced aluminium plates offer useful design guideline for their applications as the structural components in aeronautical fields.

Design of a temperature-feedback controlled automated magnetic hyperthermia therapy device.

Magnetic hyperthermia therapy (MHT) is a minimally invasive adjuvant therapy capable of damaging tumors using magnetic nanoparticles exposed radiofrequency alternating magnetic fields. One of the challenges of MHT is thermal dose control and excessive heating in superficial tissues from off target eddy current heating. We report the development of a control system to maintain target temperature during MHT with an automatic safety shutoff feature in adherence to FDA Design Control Guidance. A proportional-integral-derivative (PID) control algorithm was designed and implemented in NI LabVIEW®. A standard reference material copper wire was used as the heat source to verify the controller performance in gel phantom experiments. Coupled electromagnetic thermal finite element analysis simulations were used to identify the initial controller gains. Results showed that the PID controller successfully achieved the target temperature control despite significant perturbations. Feasibility of PID control algorithm to improve efficacy and safety of MHT was demonstrated.

Influence of Blood Compressibility on Pulse Wave Propagation Properties Based on Elastic Thin-Walled Tube Theory

Pulse wave carries abundant physiological and pathological data about the human body. Understanding the effect of blood compressibility on the transmission qualities of pulse waves is necessary to detect, cure, and prevent cardiovascular problems. In this research, the fluid–solid coupling finite element analysis model of artery system was developed using COMSOL MultiPhysics software. The influence of blood compressibility on pulse wave propagation properties in the brachial artery was investigated using the blood volume compression modulus. Results show that the influence of blood compressibility on pulse wave propagation is relatively weak and may be ignored when evaluating the compressibility of blood and that the volume compression modulus swings 2GPa over and beyond the typical range of the human body. The influence of blood compressibility on the peak value of pressure pulse wave is minor. The attenuation amplitude of the peak value of a pulse wave is bigger for the case with compressible blood than those of case with incompressible blood, and the difference between compressible and incompressible models is less than 1%. But blood compressibility has a clear impact on pulse wave velocity. It is found that the pulse wave velocity is greater than that of blood flow velocity. These findings will be valuable to investigate deeply for evaluating pressure and velocity pulse waves, as well as in providing a waveform-based preliminary diagnosis of symptoms in human body.

Research on structural type of two-way connection fittings based on valve hall

Based on the research on the structural type of valve hall two-way connection fittings, with the sustained and rapid economic growth, the power demand of various industries increases. While accelerating the construction of UHV backbone power grid, improving the transmission capacity and transmission quality of the existing power grid has become a top priority. In ± 800kV UHV DC transmission project, the rated current is up to 6250A, and the current carrying capacity of valve hall fittings in converter station increases accordingly, which puts forward higher requirements for heat resistance and reliability of fittings. Therefore, it is very necessary to study the operation reliability of valve hall fittings in converter station. In this paper, two structural types of two-way connection fittings are analyzed. The temperature field of two-way connection fittings is simulated by using the electric thermal coupling finite element analysis method. At the same time, the high current temperature rise test is carried out, and the temperature at the key position of two-way fittings is measured by thermocouple. The high current temperature rise test and simulation results show that when 6250A current is applied, there is uneven shunting between the two specimens. Under the condition of meeting the temperature rise limit, the flow through of aluminum strand connection mode is more uniform than that of aluminum row connection mode. The test results are consistent with the simulation results, which provides a reference for the subsequent design of valve hall fittings.

Coupled Eulerian-Lagrangian finite element analysis of penetration processes in silty clay for bucket foundation

ABSTRACT Bucket foundations, as an innovative type of offshore wind turbine foundation, have been widely adopted for their cost competitiveness and time effectiveness in construction and installation. For a successful installation, the penetration process prediction is crucial. This paper investigates the penetration process of both thin-walled and thick-walled bucket foundations in silty clay through small-scale experiments. Based on the experimental results, empirical formulas of penetration resistance are modified. Next, a Coupled Eulerian-Lagrangian (CEL) numerical method is validated and used to simulate the sinking process of engineering prototypes. The penetration resistance obtained by the calculated and numerical methods is in good agreement. Additionally, through the 3D CEL analysis, the disturbance of bulkheads and skirts on soil plugs is gained. The Eulerian volume fraction shows that the soil surface within the outer compartments is prone to rise to form a soil plug, which will bring out a sudden sharp increase in the penetration resistance due to the contact of lid and soil, and consequently affect the ultimate installation depth.