Finite Element Method Simulation Research Articles

Enhancing structural durability in marine concrete piles with initial defects: RS-AAT-induced advection to suppress chloride ion penetration

Chlorine-induced corrosion in unsaturated, cracked, and delaminated reinforced concrete structures is a major cause of lifespan decline in marine wet and dry zones. Reverse-seepage and Saturation based Active Anti-corrosion Technology (RS-AAT) has the scientific basis and application potential to solve this problem due to its unique saturation and reverse-seepage effects provided by structural construction means. This study introduces an analytical framework for understanding time-dependent chloride ion permeation in concrete pipe piles, incorporating the combined impact of cracks, delamination, and RS-AAT anti-corrosion approach. The analytical approach is validated through finite element method simulations and a comprehensive 90-day indoor experiment, which simulate marine submerged and tidal conditions. Extensive parametric analysis further elucidates advection-induced suppression of chloride ion diffusion by RS-AAT in cracked and delaminated conditions, considering chloride ion diffusion coefficient and water permeability coefficient, reverse-seepage pressure, initial crack characteristics and centrifugal stratification. Results show that RS-AAT substantially inhibits chloride ion penetration and lengthens the lifespan of concrete piles, even initially cracked or delaminated. This work provides a basis for RS-AAT’s application and optimization as an innovative approach to enhancing marine concrete infrastructure.

Analysis of curing deformation for resin matrix composite T-shaped stiffened panel

In this work, a multi-field coupled finite element simulation method involving thermochemistry and mechanics was devised to predict the curing deformation (C-DE) of a T-shaped stiffened panel (T-SSPL), a typical aircraft structural component, during the autoclave forming process. A more comprehensive and detailed analysis of the factors affecting the C-DE of T-SSPL is also carried out. The methodology uses the Fortran language to write different user subroutines and establish corresponding mathematical models to simulate the different mechanical states of components, and ultimately simulate the entire molding process of the product in the autoclave. And investigates the effects of process parameters, including heating rate, cooling rate, curing pressure, and structural parameters, including the number of bars and height of stringer on the C-DE of T-SSPL, and obtains the following conclusions: the heating rate and curing pressure are positively correlated with the C-DE, and the cooling rate has little influence on the C-DE, and C-DE hardly changes with the change of cooling rate; C-DE increases with the ribs count; however, it decreases and then increases with the stringer height, and these conclusions provides a theoretical basis for the manufacturing of T-SSPL.

In vivo video microscopy of the rupturing process of thin blood vessels to clarify the mechanism of bruising caused by blunt impact: an animal study

BackgroundThe thresholds of mechanical inputs for bruising caused by blunt impact are important in the fields of machine safety and forensics. However, reliable data on these thresholds remain inadequate owing to a lack of in vivo experiments, which are crucial for investigating the occurrence of bruising. Since experiments involving live human participants are limited owing to ethical concerns, finite-element method (FEM) simulations of the bruising mechanism should be used to compensate for the lack of experimental data by estimating the thresholds under various conditions, which requires clarifying the mechanism of formation of actual bruises. Therefore, this study aimed to visualize the mechanism underlying the formation of bruises caused by blunt impact to enable FEM simulations to estimate the thresholds of mechanical inputs for bruising.MethodsIn vivo microscopy of a transparent glass catfish subjected to blunt contact with an indenter was performed. The fish were anesthetized by immersing them in buffered MS-222 (75–100 mg/L) and then fixed on a subject tray. The indenter, made of transparent acrylic and having a rectangular contact area with dimensions of 1.0 mm × 1.5 mm, was loaded onto the lateral side of the caudal region of the fish. Blood vessels and surrounding tissues were examined through the transparent indenter using a microscope equipped with a video camera. The contact force was measured using a force-sensing table.ResultsOne of the processes of rupturing thin blood vessels, which are an essential component of the bruising mechanism, was observed and recorded as a movie. The soft tissue surrounding the thin blood vessel extended in a plane perpendicular to the compressive contact force. Subsequently, the thin blood vessel was pulled into a straight configuration. Next, it was stretched in the axial direction and finally ruptured.ConclusionThe results obtained indicate that the extension of the surrounding tissue in the direction perpendicular to the contact force as well as the extension of the thin blood vessels are important factors in the bruising mechanism, which must be reproduced by FEM simulation to estimate the thresholds.

Investigating the orientation dependence of local fields around spherical defects using crystal plasticity simulations

The presence of a void or secondary particle plays a crucial role in both the mechanical response and damage evolution of metals. This work presents local stress and strain field predictions in a single crystalline matrix that contains a spherical void or hard particle using crystal plasticity finite element method (CP-FEM) simulations. Simulations demonstrate highly heterogeneous orientation dependent local fields near defects. In particular, we show that matrix decohesion around hard particles will occur first before void growth in pre-existing voids under strain-controlled uniaxial tension and isochoric loading. Furthermore, CP-FEM simulations predict that the [1̄11]-oriented grain is most susceptible for failure, while grains oriented toward the [001] orientation are more resistant to failure. This work provides insights into how grain-scale microstructure with volumetric defects influence the local damage and failure behavior in metal alloys.

Revealing the origin of dendritic deposition regulated solid electrolyte interphase enabled by cation receptor in Zn-ion batteries

Aqueous Zn-metal batteries open up promising prospects for large-scale energy storage due to the advantages of ample components, cost-effectiveness, and safety features. However, the notorious dendritic development and unavoidable hydrogen evolution reaction of Zn have grown to be one of the main barriers inhibiting its further commercialization. Despite substantial studies, the mechanism of nucleation and deposition of Zn2+ ions on zinc layer surfaces remains elusive. Here, inspired by additive, the SnCl2 additive is introduced to initiate the in-situ formation of the ZnS-rich solid electrolyte interphase (SEI) layer on the Zn anode, which creates a protective “shielding effect” that hinders direct contact between water and the zinc surface, suppressing the random growth of Zn dendrites in the whole process. The mechanism of Zn nucleation was revealed by employing high-resolution transmission electron microscopy, consecutive electron diffraction coupled with finite element method (FEM) simulations. Moreover, spontaneously formed 3D architecture consists of micorsized hemispherical Sn particles not only suppresses the Zn dendrite growth by reducing the local current density, but also enables the lateral growth of Zn crystals by increasing the average surface energy. Such an electrolyte enables a long cycle life of over 2000 h in the Zn||Zn cell. Importantly, the assembled Zn||MnVO full cells with SnCl2 electrolyte also delivers substantial capacity (171.1mA h g−1 at 1 A h g−1), presenting a promising application. These discoveries not only deepen the comprehension of fundamental scientific knowledge regarding the microscopic reaction mechanism of the Zn anode but also offer significant insights for optimizing performance.

Thermal Interaction and Cooling of Electronic Device with Chiplet 2.5D Integration

With the development of artificial intelligence (AI) and high-performance computing (HPC), the microelectronic industry is challenged with increased device integration density. Chiplet architecture can break through a variety of limitations on the system-on-chip (SoC) to create a high-computility system. However, chiplet heterogeneous integration suffers from high heat flux and serious thermal interaction problems. The factors affecting thermal interaction are not clear. In this paper, a collective parameter model and a distribution parameter model are developed to clarify the optimization method to mitigate thermal interaction. The trends predicted by the parameter model are consistent with the finite element method (FEM) simulation results. Furthermore, to cool the chiplets, a thermal test vehicle is designed and fabricated, and the cooling performance of the test vehicle with different flow rates, different TIMs (Thermal Interfacial Materials) (DOW5888 vs. liquid metal), and different heat modes is experimentally investigated. Compared with DOW5888, the utilization of liquid metal TIM can mitigate thermal interaction by 56% and 76% at flow rates of 0.2 L/min and 0.8 L/min, respectively. Consequently, at a temperature rise of 60 °C and a flow rate of 0.8 L/min, using liquid metal TIM can achieve heat fluxes of 330 W/cm2 and 520 W/cm2 for two chiplets, respectively.

Foundational Engineering of Artificial Blood Vessels' Biomechanics: The Impact of Wavy Geometric Designs.

The design of wavy structures and their mechanical implications on artificial blood vessels (ABVs) have been insufficiently studied in the existing literature. This research aims to explore the influence of various wavy geometric designs on the mechanical properties of ABVs and to establish a foundational framework for advancing and applying these designs. Computer-aided design (CAD) and finite element method (FEM) simulations, in conjunction with physical sample testing, were utilized. A geometric model incorporating concave and convex curves was developed and analyzed with a symbolic mathematical tool. Subsequently, a total of ten CAD models were subjected to increasing internal pressures using a FEM simulation to evaluate the expansion of internal areas. Additionally, physical experiments were conducted further to investigate the expansion of ABV samples under pressure. The results demonstrated that increased wave numbers significantly enhance the flexibility of ABVs. Samples with 22 waves exhibited a 45% larger area under 24 kPa pressure than those with simple circles. However, the increased number of waves also led to undesirable high-pressure gradients at elevated pressures. Furthermore, a strong correlation was observed between the experimental outcomes and the simulation results, with a notably low error margin, ranging from 19.88% to 3.84%. Incorporating wavy designs into ABVs can effectively increase both vessel flexibility and the internal area under pressure. Finally, it was found that expansion depending on the wave number can be efficiently modeled with a simple linear equation, which could be utilized in future designs.

A New Numerically Improved Transient Technique for Measuring Thermal Properties of Anisotropic Materials

A new transient technique of the thermal conductivity and diffusivity measurement for anisotropic materials is presented and validated. It is based on measuring the through-plane properties using the extended dynamic plane source (EDPS) method and in-plane conductivity employing the transient plane source (TPS) and modified dynamic plane source (MDPS) methods. The key advantage of this technique is that only one pair of specimens is required for measurements. While the EDPS method is implemented on real measurements, the TPS and MDPS are applied to the finite elements method (FEM) simulation of the experiment. The accuracy of the results is enhanced by the application of the FEM and is better than 1% for materials with through-plane conductivity of less than 2 W m−1 K−1 and a specimen thickness of 9 mm.

Target-field design of surface permanent magnets

We present a target-field approach to analytically design magnetic fields using permanent magnets. We assume that their magnetization is bound to a two-dimensional surface and is composed of a complete basis of surface modes. By posing the Poisson’s equation relating the magnetic scalar potential to the magnetization using Green’s functions, we derive simple integrals that determine the magnetic field generated by each mode. This approach is demonstrated by deriving the governing integrals for optimizing axial magnetization on cylindrical and circular-planar surfaces. We approximate the governing integrals numerically and implement them into a regularized least-squares optimization routine to design permanent magnets that generate uniform axial and transverse target magnetic fields. The resulting uniform axial magnetic field profiles demonstrate more than a tenfold increase in uniformity across equivalent target regions compared to the field generated by an optimally separated axially magnetized pair of rings, as validated using finite element method simulations. We use a simple example to examine how two-dimensional surface magnetization profiles can be emulated using thin three-dimensional volumes and determine how many discrete intervals are required to accurately approximate a continuously varying surface pattern. Magnets designed using our approach may enable higher-quality bias fields for electric machines, nuclear fusion, fundamental physics, magnetic trapping, and beyond. Published by the American Physical Society 2024

Scratch visibility modeling on flat & textured polymeric surfaces

Polymer materials have gained widespread usage in the marketplace due to their lightweight properties, versatility, and cost-effectiveness. However, their susceptibility to scratches has been a longstanding issue. To overcome this shortcoming, surface texturing is one of the most low-cost, efficient ways to improve scratch performance by utilizing the inherent moldability of polymers. Textures rely on both the improvement of contact properties in terms of reduction in surface friction and the perceived visibility of scratches by masking the scratch-induced deformations. The current testing of the effectiveness of a particular texture design on scratch resistance requires tedious and costly psychophysical and/or experimental verification. In this paper, we present a comprehensive framework for scratch visibility analysis in virtual reality, integrating a novel scheme and finite element methods simulation. Our approach considers material, topographical, and optical properties, replicating perceived scratch visibility within the virtual space. The FEM model was found to overpredict the scratch depth and underpredict the shoulder height. A parametric study based on the material constitutive and surface properties has been carried out to highlight the effect of different material and surface factors on scratch performance and visibility. This study opens the door for a complete virtual design-development-analysis cycle for scratch performance evaluation of polymers.

Analytical prediction of the open‐circuit magnetic field for the V‐shaped interior PM machine by the improved subdomain method

AbstractThe open‐circuit magnetic field of the V‐shaped interior PM (IPM) machine is predicted by the analytical method. The method is implemented following the basic principle of the subdomain method. The machine model is divided into five different regions, including rotor slot, magnetic barrier, air gap, stator slot, and stator slot opening. To perform the analytical prediction process in the polar coordinate system, these regions should be transformed into the appropriate subdomains. The last four regions can be transformed into the subdomains with the required shape based on the existing method. The rotor slot cannot be treated as a single subdomain, for the shape of which is irregular. Herein, the PM and vacuum region in the rotor slot is divided into several fan‐shaped subdomains. The division method is described clearly. Then, the boundary conditions alongside the interface between adjacent subdomains are derived based on function transformation. On this basis, the open‐circuit magnetic field of the IPM machine can be predicted. The magnetic field of the 6p/36 s V‐shaped IPM machine is obtained by the proposed method, finite element method simulation, and experiment, respectively. Additionally, the comparison results verify the accuracy and efficiency of the proposed method.

Finite Element Method Simulation Study on the Temperature Field of Mass Concrete with Phase Change Material

Phase change materials can be converted between solid, liquid, and gaseous states, absorbing or releasing a large amount of heat. PCM is incorporated into concrete to adjust the temperature difference between inside and outside of concrete, which can reduce cracking. In this paper, the finite element analysis method is used to establish the model of an ordinary concrete structure, doped with phase change materials, on the basis of mechanical properties and a temperature regulation test performed by calculating the adiabatic temperature rise of concrete with different contents of composite phase change material, comparing the experimental and simulation results of the ordinary concrete structures with phase change materials, and analyzing the change in temperature field of the concrete structure with the content of self-prepared composite phase change materials. It is found that the addition of self-prepared composite phase change materials reduces the temperature peak of the concrete structure in the stage of hydration heat and delays the time taken to reach the temperature peak. Then, the temperature field of the phase change mass concrete structure is established, and the influence law of composite phase change material admixture on the temperature field of mass concrete is summarized through the time–temperature curves of different admixture amounts and positions so as to predict the possibility of cracks in mass concrete.

Lifetime prediction of copper pillar bumps based on fatigue crack propagation

2.5D package realizes the interconnection of multiple dies through Si interposers, which can greatly improve the data transmission rate between dies. However, its multi-layer structure and high package density also place higher reliability requirements on the interconnection structure. As a key structure for interconnection, copper pillar bump (CPB) has small size, high heat generation, and thermal mismatch with silicon chips. The thermal fatigue failure of CPB has gradually become the main failure mode in 2.5D package. Due to the small size of CPB and the large proportion of intermetallic compound (IMC) layers, the lifetime prediction method of spherical solder joints is no longer suitable for CPB. Therefore, it is necessary to establish a fatigue lifetime prediction method for CPB. This paper establishes a method for obtaining the lifetime of CPB based on the basic theory of fatigue crack propagation. Using the extended finite element simulation method, the crack propagation lifetime of CPB under thermal cycling was obtained, and the influence of different IMC layer thickness on the fatigue lifetime of CPB was analyzed. The results indicated that the fatigue lifetime of cracks propagating in the IMC layer is lower than that of cracks propagating in the solder layer, and an increase in the thickness of the IMC layer leads to a significant decrease in the fatigue lifetime of CPB. The lifetime prediction method for CPB proposed in this paper can be used for reliability evaluation of 2.5D package, and has certain reference value for the study of the lifetime of CPB.

Discrete differential geometry-based model for nonlinear analysis of axisymmetric shells

In this paper, we propose a novel one-dimensional (1D) discrete differential geometry (DDG)-based numerical method for geometrically nonlinear mechanics analysis (e.g., buckling and snapping) of axisymmetric shell structures. Our numerical model leverages differential geometry principles to accurately capture the complex nonlinear deformation patterns exhibited by axisymmetric shells. By discretizing the axisymmetric shell into interconnected 1D elements along the meridional direction, the in-plane stretching and out-of-bending potentials are formulated based on the geometric principles of 1D nodes and edges under the Kirchhoff–Love hypothesis, and elastic force vector and associated Hessian matrix required by equations of motion are later derived based on symbolic calculation. Through extensive validation with available theoretical solutions and finite element method (FEM) simulations in literature, our model demonstrates high accuracy in predicting the nonlinear behavior of axisymmetric shells. Importantly, compared to the classical theoretical model and three-dimensional (3D) FEM simulation, our model is highly computationally efficient, making it suitable for large-scale real-time simulations of nonlinear problems of shell structures such as instability and snap-through phenomena. Moreover, our framework can easily incorporate complex loading conditions, e.g., boundary nonlinear contact and multi-physics actuation, which play an essential role in the use of engineering applications, such as soft robots and flexible devices. This study demonstrates that the simplicity and effectiveness of the 1D discrete differential geometry-based approach render it a powerful tool for engineers and researchers interested in nonlinear mechanics analysis of axisymmetric shells, with potential applications in various engineering fields.

A Surrogate Model's Decision Tree Method Evaluation for Uncertainty Quantification on a Finite Element Structure via a Fuzzy-Random Approach

A novel additive manufacturing method (AM)) constructs a three-dimensional model from a computer-aided design by adding material layer by layer. This technique produces a lightweight end product with complex geometries and has gained recognition among industrial players. Nonetheless, the mechanical properties and geometry components are the uncertainties that prevail in its structures. An alternative approach using the Finite Element Method (FEM) to analyse these uncertainties demands extensive computational effort and time consumption. Therefore, a machine learning (ML) tool using the surrogate modelling technique offers an alternative way to provide and predict simulation outcomes. This study applies two surrogate modeling approaches, the decision tree (DT) and the Gaussian process regression (GPR) methods. Output data from a FEM simulation with uncertainty elements are obtained for the training purposes of the surrogate models. Both ML methods can predict simulation results with high precision. Both approaches obtained an excellent coefficient of determination value, R2 of 0.998, and Root Mean Square Error, RMSE of 0.012, successfully reducing time consumption and computational effort. The DT method shows better robustness when compared to the GPR method. A value change in the input parameter significantly impacts the surrogate model's prediction performance. An adequate quantity of data input for the training phase of both surrogate models exhibits the FEM results with the presence of uncertainty and robustness.

An improved uncooperative space target de-tumbling method using electromagnetic de-tumbling devices with AC excitation

A large amount of space debris with rotational motion occupies limited orbital resources, necessitating a de-tumbling phase before the capturing phase to mitigate collision risks. To enhance the safety and performance of de-tumbling uncooperative space targets, this paper proposes and investigates a contactless method using electromagnetic de-tumbling devices with alternating current (AC) excitation, which can generate larger de-tumbling torque compared to conventional direct current (DC) excitation. First, the optimal configuration of the devices for de-tumbling the target is studied under the constraint of constant power consumption. Then, the mechanism of de-tumbling torque generated by AC excitation is analyzed, leading to the development of the optimal AC excitation de-tumbling method. Subsequently, the optimal configuration and AC excitation de-tumbling method are validated through finite element method simulations, confirming the advantages of the proposed method. Finally, ground experiments demonstrate the superiority of AC excitation over DC excitation.

Super-resolution based on frequency dependence of echo phase rotation in 3D ultrasound imaging by spatially encoded transmit/receive

Abstract Currently, we are investigating the ultrasound imaging of a single transmitter/receiver system for a puncture microscopy application. The proposed model, consisting of an encoding mask layer with irregular thickness attached to the surface of the transducer, was carried out by a finite element method simulator. To increase the number of measurements, the device was rotated for several rotations. The image for each rotation was constructed separately by numerically solving the linear equation of the image model. In this paper, we introduce a super resolution method (SCM) based on an eigenvalue analysis in order to improve the poor resolution. It was assigned as weights and multiplied by the current image. The simple averaging and coherence factor were applied to compound over a number of rotations to obtain the final image. The results show that the image has a better image resolution and also suppresses the unwanted signals as well.

Increasing Light-Induced Forces with Magnetic Photonic Glasses

In this work, we theoretically and experimentally study the induction of electromagnetic forces in an opal-based magnetic photonic glass, where light normally impinges onto a disordered arrangement of SiO2 spheres by the aggregation of Fe3O4 nanoparticles. The working wavelength is 633 nm. Experimental evidence is presented for the force that results from forced oscillations of the photonic structure. Finite-element method simulations and a theoretical model estimate the magnetic force volumetric density value, peak displacement, and velocity of oscillations. The magnetic force is of the order of 56 microN, which is approximately 500-times higher than forces induced in dielectric optomechanical photonic crystal cavities.

Identification of bored pile defects utilizing torsional low strain integrity test: Theoretical basis and numerical analysis

The torsional low strain integrity test (TLSIT), known for its advantages such as a smaller detection blind zone, improved identification of shallowly buried defects, stable phase velocity for signal interpretation, and better adaptability for existing pile testing. However, it lacks a comprehensive understanding of the authentic three-dimensional (3D) strain wave propagation mechanism, particularly wave reflection and transmission at defects. To address this gap, a novel 3D theoretical framework is introduced in this context to model the authentic 3D wave propagation during the TLSIT. The proposed approach is validated by comparing its results with those obtained from 3D finite element method (FEM) simulations and simplified 1D (one-dimensional) and 3D analytical solutions. Additionally, a parametric study is conducted to enhance insights into the formation mechanism of high-frequency interference observed during the TLSIT. Finally, a defect identification study is performed to provide guidance for interpreting the wave spectrum in terms of defect characteristics.

The crack initiation mechanism of steel disc when paired with Fe-PM pad for high-speed train braking

In this study, the Fe-based powder metallurgy (Fe-PM) brake pad was paired with a cast steel brake disc to conduct braking tests on a full-scale flywheel braking dynamometer. We systematically analyzed the morphologies of the worn surfaces and the disc temperatures during braking, uncovering the friction and wear characteristics of the friction pair. As well as highlighted the changes in contact status between the friction pair throughout the braking process, which further affected the pad wear rate and thermal fatigue damage to the brake disc. The wear rate of the pad was 0.16 cm3/MJ during the braking tests at an initial brake speed (IBS) of 250 km/h. However, it rapidly increased to 0.66 cm3/MJ as the IBS rose to 380 km/h, indicating a severe decline in wear resistance as the speed increased. The curves of the instantaneous coefficient of friction (COF) displayed significant fluctuations throughout the single braking process and got more pronounced with the increase in the IBS, similar phenomena also occurred on the measured temperature during each braking test. These were caused by the constant changing of the contact status arose by dynamic equilibrium of the formation, spalling, and regeneration for the third body layer (TBL) on the contact surfaces. Additionally, the changing of the contact status also resulted in an uneven distribution of temperature on the disc surface, which in turn generated a temperature gradient and thermal stress. Concurrently, as the braking continued, high frequency alternating thermal stress (HFATS) on the disc surface was induced by the continuously changing contact status, which was confirmed by finite element method (FEM) simulation. As a result, the brake disc would undergo thermal fatigue after fewer braking cycles, and thermal cracks would appear on the disc surface.