Finite Element Method Simulation Research Articles

Formation of property gradient in coarse-grained niobium using a wedge tool: Experiment and analysis

We introduce a novel severe plastic deformation process for coarse-grained niobium, which employs a tool with an inclined (wedge) surface for deforming the material by a reverse shear scheme. The process increases the intensity of shear deformations and the depth of plastic deformation in the body of the workpiece when a wedge tool acts on its surface. The essence of the process is in the repeated displacement of the workpiece material in opposite directions during the asymmetrical introduction of a wedge tool until the required degree of deformation is accumulated in the tool-affected volume. This deformation scheme applies a 15° angle wedge tool to a 21-mm high workpiece. After nine cycles of plastic deformation, a gradient of the accumulated degree of deformation in the range of true strain e = 0.3–4.5 was created. At maximum deformation, the microhardness of the workpieces increased by 1.86 times and the tensile strength by 1.6 times. Fractograms show a significant influence of the accumulated degree of deformation on the nature of the fracture. The finite element method simulation of the deformation process showed that creating a uniformly strengthened layer requires at least five deforming operations. For example, the proposed reverse shear process with a wedge tool can be applied to improve the structure of the surface layers of niobium ingots for subsequent forming. Due to the creation of a significant gradient of properties, the reverse shear process can be used as an express method for determining the mechanical characteristics of different materials in a wide range of accumulated degree of deformation.

Effect of Ferrite Core Modification on Electromagnetic Force Considering Spatial Harmonics in an Induction Cooktop

This study investigates the influence of ferrite shape modifications on the performance and noise characteristics of an induction cooktop. The goal is to optimize the air gap dimensions between ferrites and cookware, enhancing efficiency while managing noise levels. Using finite element method (FEM) simulations, we analyze the spatial distribution of magnetic forces and their harmonics. Eight ferrite shape models were examined, focusing on both outer and inner air gaps. Model #8 (reduced outer air gap) and Model #9 (reduced inner air gap) were experimentally validated. Noise measurements indicated that Model #8 reduced 120 Hz harmonic noise components, while Model #9 increased them due to enhanced excitation forces. Current measurements confirmed that Model #9 achieved higher efficiency, with RMS current reduced to 94.54% of the base model. The study reveals a trade-off between performance and noise: inner air gap reduction significantly boosts efficiency but raises noise levels, whereas outer air gap reduction offers balanced improvements. These findings provide insights for optimizing induction cooktop designs, aiming for quieter operation without compromising efficiency.

Multi‐parameter design optimization of crash box for crashworthiness analysis

AbstractThis study focuses on the optimization process of crash box design. The design optimization process is resource‐intensive and requires multiple dynamic simulations. Numerous design parameters can be varied to satisfy the crashworthiness objectives. Therefore an intelligent and robust machine learning (ML) framework has been developed. This framework can be employed to assist in the optimization of various crashworthiness components with different crashworthiness objectives.Here, a reinforcement learning‐based (RL) machine learning framework is developed. It consists of a finite element method (FEM) surrogate and RL environment. The FEM surrogate is trained using data from FEM simulations as well as synthetic data generated by a Generative Adversarial Network (GAN). An inverse problem is solved for optimizing the geometrical parameters of the boundary value problem while the RL is receiving input from the FEM surrogate. RL has proven to be accurate in many fields due to its ability to explore and exploit the learned dynamics. Conventional algorithms require numerous iterations and tuned functions to achieve appropriate results and need to be initialized after a slight change in the problem. Due to an optimization of input parameters in an inverse problem, RL is chosen for the present investigation.For the simulation data needed, the crash box is designed with linear first‐order accurate four nodal shell elements. Also, bilinear elastoplastic material along with geometrical nonlinearity is used to simulate the dynamic deformation process.The RL agents learn to vary the crash box design parameters and search for the optimal parameters. The optimal parameters are based on the user‐defined crashworthiness objectives.

Pediatric occupant-to-occupant interaction responses in side impact conditions using Q-dummy and child human body models

Objective Road safety of children has improved considerably over the past decade; however, there is still much scope to better protect these occupants. Ensuring adequate protection of children seated in the rear seats requires a greater understanding of how children are injured in side crashes. The purpose of this study was to enhance the knowledge of children’s potential injuries in side impact collisions by the investigation of two different child sizes seated in different positions in the rear seats. The injury metrics associated with the occupant-to-occupant or occupant-to-child restraint system interaction was also identified. Methods Finite Elements Method simulations were performed using a validated simplified vehicle model with fully deformable side components. Dynamic virtual tests according to the Euro NCAP Child Occupant Protection Protocol were performed considering three different scenarios in terms of occupants´ distribution in the rear seats. Simulations were conducted with dummy and human body models. The injury metrics associated with near-side and far-side positions and the occupant-to-occupant interaction were analyzed. Results The 10-year-old child seated in the far-side position presented higher injury values, especially in the head due to the contact with the adjacent child or child restraint occupying the near-side seating position. Similar responses were observed in human body and dummies models in terms of head and neck injury values. However, human body models showed an increase in the chest measurements. Conclusions This study highlighted that the potential injuries of a child seated on the rear seats in a side impact crash are likely to be increased by the presence of an adjacent seat occupant, especially when larger children were seated in the far-side seating location or a CRS was installed in the near-side seating position. Results offer insight into the occupant-to-occupant interaction and occupants’ size as relevant factors to improve children safety under side impact conditions.

A new design and analysis of low-profile soft rotary pneumatic actuator for enhanced rotation and torque

Soft actuators producing bending motions have gained significant attention for their advantages in mimicking the properties and movements of human muscles. However, the research on soft rotary actuators has yet to keep pace with other soft actuators. This paper makes two key contributions to the design and modeling of these actuators. First, we introduce a novel design for a soft rotary pneumatic actuator. This design outperforms existing cylindrical shaped soft actuators, especially in terms of torque. Second, we present an analytical model based on finite deformation. This model accurately describes the relationship between rotational movement and corresponding torque. The accuracy of this model is validated through Finite Element Method (FEM) simulations and corresponding tests. By providing a mechanically efficient design and a highly accurate analytical model, this work offers a comprehensive solution for the development of new soft pneumatic actuators.

Investigation of failure analysis on fatigue crack initiation influenced by critical resolved shear stress in X10CrMoVNb9-1 steel

This study investigates the influences of the critical resolved shear stress (CRSS) values on calculating the number of cycles for the fatigue crack initiation cycle of X10CrMoVNb9-1 (P91) under cyclic loading conditions at room temperature while considering varied surface roughness on microstructure models. The micropillar compression test was utilized to calculate the CRSS values, incorporating the Schmid factor, the Frank–Read source together with the Hall–Petch effect, measuring the diameter of the micropillar after compression, and the Mlikota and Schmauder equation. Two primary microstructure surface roughness – plane surface roughness (PS) and surface roughness (SR) with an average of 1 µm – were generated using the Voronoi Tessellation (VT) method. Finite Element Method (FEM) simulations were conducted to identify different stress distributions across these artificial microstructures. These stress distributions were subsequently analyzed using the physics-based Tanaka-Mura model (TMM) to estimate the number of cycles for fatigue crack initiation at several stress amplitudes and six types of microstructure. The number of cycles varies significantly at lower stress amplitudes and convergence at higher stress amplitudes. The study of the CRSS of steel P91 offers a significant advancement in fatigue research, particularly with implications for power plants.

Safety barriers under changing operating conditions–An analysis of impact parameters in Germany

Vehicle restraint systems and especially the impact of a collision on such are subject to various influencing variables. These systems are tested and approved through vehicle impact tests to ensure that safety standards are met as well as to ensure comparability amongst the systems. However, differences in the objectives of the standard DIN EN 1317 and the behaviour in practice have become apparent.There is the standard DIN EN 1317 which defines the impact tests on testing grounds. Nevertheless, there are a number of influencing parameters such as developments in the vehicle fleet over the last years, available safety barriers, including their construction types and the impact itself. Previous research indicates that there could be a gap between these parameters.This research uses an empirical analysis based on chiefly quantitative data sources to evaluate the differences between these parameters. It leads to a partial divergence between static requirements of the standard and the actual road traffic conditions. Additionaly, the differences are developed within a vulnerability analysis and for the purpose of comparison, the advantages as well as the disadvantages of the standardized impact tests are discussed in this paper.As a result, a parameter based suggestion for a reevaluation of impact tests for safety barriers, according to the standard DIN EN 1317, is advisable due to the changing road traffic on the current stock and new barrier systems to be built. This research strives to illuminate the trend for new investigation methods such as the finite element method (FEM) simulation. It gives an outlook to further research needs in safety barriers, principally in the observation of the future development of the impact parameters. At the same time, impulses and potential for improvement can be identified for the future documentation of vehicle impacts on these barriers.

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.

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.

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.