Finite Element Method Software Research Articles

3-D stochastic modeling approach in thermal inactivation: estimation of thermal survival kinetics of Escherichia coli O157:H7 in a hamburger after exposure to desiccation stress.

Desiccation tolerance of pathogenic bacteria is one strategy for survival in harsh environments, which has been studied extensively. However, the subsequent survival behavior of desiccation-stressed bacterial pathogens has not been clarified in detail. Herein, we demonstrated that the effect of desiccation stress on the thermotolerance of Escherichia coli O157:H7 in ground beef was limited, and its thermotolerance did not increase. E. coli O157:H7 was inoculated into a ground beef hamburger after exposure to desiccation stress. We combined a bacterial inactivation model with a heat transfer model to predict the survival kinetics of desiccation-stressed E. coli O157:H7 in a hamburger. The survival models were developed using the Weibull model for two-dimensional pouched thin beef patties (ca. 1 mm), ignoring the temperature gradient in the sample, and a three-dimensional thick beef patty (ca. 10 mm), considering the temperature gradient in the sample. The two-dimensional (2-D) and three-dimensional (3-D) models were subjected to stochastic variations of the estimated Weibull parameters obtained from 1,000 replicated bootstrapping based on isothermal experimental observations as uncertainties. Furthermore, the 3-D model incorporated temperature gradients in the sample calculated using the finite element method. The accuracies of both models were validated via experimental observations under non-isothermal conditions using 100 predictive simulations. The root mean squared errors in the log survival ratio of the 2-D and 3-D models for 100 simulations were 0.25-0.53 and 0.32-2.08, respectively, regardless of the desiccation stress duration (24 or 72 h). The developed approach will be useful for setting appropriate process control measures and quantitatively assessing food safety levels.IMPORTANCEAcquisition of desiccation stress tolerance in bacterial pathogens might increase thermotolerance as well and increase the risk of foodborne illnesses. If a desiccation-stressed pathogen enters a kneaded food product via cross-contamination from a food-contact surface and/or utensils, proper estimation of the internal temperature changes in the kneaded food during thermal processing is indispensable for predicting the survival kinetics of desiccation-stressed bacterial cells. Various survival kinetics prediction models that consider the uncertainty or variability of pathogenic bacteria during thermal processing have been developed. Furthermore, heat transfer processes in solid food can be estimated using finite element method software. The present study demonstrated that combining a heat transfer model with a bacterial inactivation model can predict the survival kinetics of desiccation-stressed bacteria in a ground meat sample, corresponding to the temperature gradient in a solid sample during thermal processing. Combining both modeling procedures would enable the estimation of appropriate bacterial survival kinetics in solid food.

Modeling of Heat and Mass Transfer in Cement-Based Materials during Cement Hydration—A Review

Cement-based materials encompass a broad spectrum of construction materials that utilize cement as the primary binding agent. Among these materials, concrete stands out as the most commonly employed. The cement, which is the principal constituent of these materials, undergoes a hydration reaction with water, playing a crucial role in the formation of the hardened composite. However, the exothermic nature of this reaction leads to significant temperature rise within the concrete elements, particularly during the early stages of hardening and in structures of substantial thickness. This temperature rise underscores the critical importance of predictive modeling in this domain. This paper presents a review of modeling approaches designed to predict temperature and accompanying moisture fields during concrete hardening, examining different levels of modeling accuracy and essential input parameters. While modern commercial finite element method (FEM) software programs are available for simulating thermal and moisture fields in concrete, they are accompanied by inherent limitations that engineers must know. The authors further evaluate effective commercial software tools tailored for predicting these effects, intending to provide construction engineers and stakeholders with guidance on managing temperature and moisture impacts in early-age concrete.

Use of lower tolerance limits for designing chair frames with round-end mortise and tenon joints

ABSTRACT In this study, the reliability of the mortise-tenon (MT) joints was examined experimentally and numerically. The joint strength has been determined empirically and numerically, but the reliability of the joint does not rely on a single asset – mean and standard deviation. The prediction of its strength also refers to a single value in the future population, but tolerance limits are related to a portion of the future population. Therefore, ensuring joint reliability comes into prominence not only for empirical data but also for theoretical and numerical analysis. For this purpose, the moment capacity of the T-shaped MT joints constructed of white oak was determined, and the lower tolerance limits (LTLs) approach was used to construct confidence/proportion (γ/β) levels for reliability. According to the results, the moment capacity of the MT joints was 341 Nm. The LTL values at 0.95/0.95, 0.99/0.95, 0.95/0.99, and 0.99/0.99 γ/β levels were 231, 226, 187 and 181 Nm, respectively. The normal stresses at each γ/β level were calculated based on the moment capacity and tenon sizes and were compared with the finite element method (FEM). Experimental and numerical results varied from 0.3% to 13.4%. Furthermore, a side frame was imposed to a vertical load of 1000 N on the front leg, and the moment of the joint on the side rail to the back post was measured (196 Nm). The side frame was modeled on ABAQUS – FEM software – and subjected to a moment of 196 Nm on the side rail. The theoretical and numerical results of stresses on joints differed from – 4.3% to 5.8%. The study showed that the reliability value is known, and; the joints could be designed by using FEM.

Shallow tunneling's impact on surface settlements

The research described in this paper deals with the impact of shallow tunneling on surface settlements in urban areas. The study focuses on carrying out a numerical analysis and a parametric geotechnical study to investigate the effects of tunnel excavation on the surface ground, particularly with regard to distortion and potential damage to structures above the tunnel. To carry out the study, the researcher used a finite element method (FEM) software package called Plaxis. This software is commonly used for geotechnical analysis and allows simulating and analyzing the subsurface conditions in Algiers underground in the context of excavating a shallow tunnel. The New Austrian Tunnelling Method (NATM) excavation method was chosen for the study. The results of the numerical analysis are presented in terms of displacements. The results indicate that ground flow has a significant influence on ground movement, probably contributing to surface settlement. However, the effect of tunnel excavation on the lowering of the water table and Young's modulus (a measure of soil stiffness) is relatively small in comparison. The research provides valuable information on the potential impacts of shallow tunneling in urban areas and the factors that play a crucial role in determining the extent of ground movement and surface settlement. By using numerical analysis and conducting a parametric geotechnical study, and gives valuable insights into the potential impacts of shallow tunnelling in urban areas and the factors that play a crucial role in determining the extent of ground movements and surface settlements. By using numerical analysis and conducting a geotechnical parametric study, and contributes to a better understanding of the behavior of the ground during tunnelling operations in Algiers. The findings can be helpful in designing future tunnelling projects to mitigate potential risks to structures and infrastructure located above the tunnels.

Estimation of inelastic heat fraction of Ti-6Al-4V alloy using inverse analysis

This work aims to determine the inelastic heat fraction of Ti-6Al-4V alloy by coupling the experimental and Finite Element Method (FEM) results by an inverse analysis approach. The inelastic heat fraction is a crucial factor in revealing information on the deformation mechanism and forms the basis of the microstructural evolution of a material. Hot compression tests on Ti-6Al-4V alloy at various temperatures and strain rates were carried out using the Gleeble thermo-mechanical simulator. An axisymmetric thermo-mechanical modelling was carried out using the FEM package i.e., ABAQUS. The work reveals that the inelastic heat fraction increases with an increase in strain rate and decreases with an increase in deformation temperature. The proposed method is capable of predicting the inelastic heat fraction of a material for a wide range of temperatures and strain rates. The FEM modelling and experimental results exhibit good agreement. The findings of this study can aid in more precise material modelling and contribute to the formation of a thermo-mechanical material database.

A semi-automated pipeline for finite element modeling of electric field induced in nonhuman primates by transcranial magnetic stimulation

BackgroundTranscranial magnetic stimulation (TMS) is used to treat a range of brain disorders by inducing an electric field (E-field) in the brain. However, the precise neural effects of TMS are not well understood. Nonhuman primates (NHPs) are used to model the impact of TMS on neural activity, but a systematic method of quantifying the induced E-field in the cortex of NHPs has not been developed. New MethodThe pipeline uses statistical parametric mapping (SPM) to automatically segment a structural MRI image of a rhesus macaque into five tissue compartments. Manual corrections are necessary around implants. The segmented tissues are tessellated into 3D meshes used in finite element method (FEM) software to compute the TMS induced E-field in the brain. The gray matter can be further segmented into cortical laminae using a volume preserving method for defining layers. ResultsModels of three NHPs were generated with TMS coils placed over the precentral gyrus. Two coil configurations, active and sham, were simulated and compared. The results demonstrated a large difference in E-fields at the target. Additionally, the simulations were calculated using two different E-field solvers and were found to not significantly differ. Comparison with Existing MethodsCurrent methods segment NHP tissues manually or use automated methods for only the brain tissue. Existing methods also do not stratify the gray matter into layers. ConclusionThe pipeline calculates the induced E-field in NHP models by TMS and can be used to plan implant surgeries and determine approximate E-field values around neuron recording sites.

Phase-field damage simulation of subloop loading in TiNi SMA

In practical applications, TiNi shape memory alloys (SMAs) exhibit behavior that can pose a challenge with current constitutive models and their implementations in finite element method (FEM) software. TiNi SMA devices typically operate in the forward or reverse martensitic transformation regime, which is known as subloop loading. During such cyclic loading–unloading, the hysteresis stress–strain loop changes because of material damage, which can be considered the fatigue of TiNi SMAs. During both the loading and unloading processes, the stress plateau decreases. At the same time, the accumulated (residual) martensitic transformation strain increases. In this study, the experimental investigation results and observations of the aforementioned phenomena are presented. Next, the phase-field damage model is employed, along with a modified Lagoudas constitutive model, to simulate the change in stress–strain hysteresis. Furthermore, a fatigue function is used to simulate the accumulation of martensitic transformation strain. The experimental stress–strain response is compared with the simulation results, and good quantitative and qualitative agreement is obtained. The damage and martensitic volume fraction with respect to strain are discussed for full-loop and subloop loading. The observations and conclusions, as well as open questions, are presented. Possible directions for future research are provided.

Parallel FEM for structural analysis of reinforced systems

Calculations in software systems based on the finite element method (FEM), performed with account for genetic nonlinearity, i.e., assembling, are not feasible for a number of construction problems. In particular, in buildings made of factory-made and cast-in-place concrete, the latter is gradually involved in deformation and external load processes. In reconstructed buildings, during the increase in the element cross-section (e.g., reinforced concrete or metal casing), the reinforcing and reinforced materials are also involved in deformation and external load processes at different time. As a result, there are initial stresses and strains in the "old" part of the element by the time its "new" part installation and strength gain. At the same time, in the reinforcing material or cast-in-place element, the stress-strain state is zero until the additional load is applied.Thus, during the structural analysis, a change in the finite element stiffness is required. But FEM software systems have no finite element capable of changing (increasing) the stiffness. This determines the relevance of the developed algorithm for the structural analysis of factory-made and cast-in-place concrete buildings using the parallel FEM.Purpose: The aim of this work is to improve the parallel FEM and develop a calculation algorithm based on it.Research findings: Based on the parallel FEM, the calculation algorithm is proposed for factory-made and cast-in-place concrete buildings. The proposed algorithm accounts for the structural properties of such buildings, including the gradual involvement of different-aged materials in the deformation process. Using the proposed algorithm, the structural analysis is conducted for the reconstructed system, in which the finite element is replaced by the parallel element, and the hinge coupling of elements is simultaneously replaced by a rigid one.

Forward iterative algorithm for fabrication geometry of steel girders in cable-stayed bridges

This paper proposes a forward iterative algorithm designed for determining the fabrication geometry of the steel girder in cable-stayed bridges during the segment installation process. The expression of fabrication geometry control parameters and geometric dimensions for steel girder fabrication is deduced based on the installation geometry. Based on the equivalent plane algorithm for spatial stay cables, this paper establishes a forward iterative algorithm to simulate the construction process of cable-stayed bridges, employing the unstressed cable length as the control calculation parameter. The algorithm is programmed into a finite element method software, enabling a precise and well-converged simulation of the cable-stayed bridge construction process. This method has been successfully applied in a kilometer-scale cable-stayed bridge, facilitating the determination of internal forces and girder geometry throughout the construction process. This also streamlines the acquisition of fabrication parameters for individual girder segments. The application results demonstrate that the research presented in this paper provides an efficient and accurate calculation method for determining the fabrication parameters of steel girders in cable-stayed bridges.

Numerical modelling of the warping behaviour at the first layer-build plate interface in 3D-printed models produced via the fused deposition modelling process

The material structure of 3D-models printed via the fused deposition modelling (FDM) technique is mainly affected in the z-direction of the 3D-print as a result of the layer-by-layer approach which tend to exhibit a deformation behavior corresponding to a type of transversely orthotropic material. Moreover, uncontrolled parameters such as printing temperature and printing speed have been reported to adversely affect 3D-print quality leading to undesired effects such as distortion and warpage. The additive manufacturing process is a relatively new field in advanced manufacturing where further research and innovation are required to overcome the limited strength and structural performance observed in presently 3D-printed components. In line with the above, this study proposes the numerical investigation of the warping behavior in PLA (Polylactic acid) - based 3D printed models by considering the finite element method (FEM) software of LS-DYNA. The warping investigation was specifically centered on the cooling cycle prevailing between the layer-by-layer structures. The findings of this study showed that warpage would most likely occur in the thermal process model corresponding to abrupt change in temperature due to a buildup of strain between the bottom most layers of the 3D model and the build plate. The findings of this study, which shed light on the warping behaviour in 3D-models, has direct implications on the final quality of 3D-printed components.

Dynamic characteristics testing and modeling in electromagnetic-thermal-force coupling of electromagnetic devices using parallel finite element simulation

Electromagnetic systems of Electromagnetic devices involve multiphysics coupling of electromagnetic fields, electrical circuits, mechanical motion, and temperature fields. When the digital prototype model has a large number of meshes, the commercial finite element software also has the disadvantage of long computation time in the simulation of dynamic characteristics of electrical apparatus. This paper proposes a transmission line method (TLM) based digital modeling method for the electromagnetic-thermal-force coupling to test and evaluate the static and dynamic characteristics of electromagnetic devices more accurately and efficiently. The case study is developed on a direct current (DC) contactor, and the dynamic characteristics testing and modeling in the electromagnetic-thermal-force coupling of the contactor are investigated. The numerical results of the finite element method (FEM) model for the electromagnetic system of the contactor are compared with the commercial FEM software Altair Flux and the experimental results, which demonstrate the exceptional accuracy of the proposed digital modeling method for the multiphysics coupling of the DC contactor. Meanwhile, the dynamic characteristics of the DC contactor at different ambient temperatures are measured and evaluated, and the comparison with the experimental measurements shows the applicability of the proposed digital prototype model at different ambient temperatures. Compared with the conventional Newton-Raphson (NR) iteration, when dividing fine mesh and extremely fine mesh, the TLM parallel computing significantly improves the efficiency of solving the dynamic characteristics of multiphysics coupling by about 35 % and 44 % with the same computational accuracy, respectively. The dynamic characteristics evaluation method combined with digital modeling technology and experimental measurements proposed in this paper demonstrates high accuracy and solving efficiency, making a notable contribution to the field of design and optimization of electromagnetic devices.

Interferometric characterization of high-frequency piezoelectric effects in hydroxyapatite thin films

Hydroxyapatite (HAp) qualities such as biocompatibility and piezoelectricity make it an excellent material for biomedical applications. Here, HAp thin film samples were fabricated onto silica substrates to study their piezoelectric behavior with optical interference. Thin solid films were deposited using previously synthesized HAp powder, sol-gel, and spin-coating techniques. The samples were characterized by scanning electron microscopy, energy dispersive X-ray, Raman, and UV-Vis spectroscopies. The statical piezoelectric effect of the samples was studied by using a finite element method and computational software. Additionally, an experimental Bode analysis allows computing the internal electrical components of the films using high-frequency AC voltage. The electrical behavior is related to the equivalent circuit of a piezoelectric crystal, which indicates the range of frequencies where the electromechanical effect is maximum. A Sagnac interferometer was used to characterize the strain in the HAp as a function of the electrical input frequency. The displacement of the interferometric fringe pattern allows us to estimate the change in the thickness of the sample and compute the piezoelectric constant. The synthesis of HAp thin films with piezoelectric properties provides an effective way to produce sensors and actuators for technological applications.

Design, Analysis and Experimental Verification of a Coreless Permanent Magnet Synchronous Motor

The paper presents a new cost-effective magnetic circuit structure of a coreless permanent magnet synchronous motor (PMSM) with 16 poles and 12 coils for a mass production fan drive unit. 2D and 3D numerical models of the coreless PMSM were developed. Optimisation calculations were carried out using the field model of the machine. Multistage calculations were performed using the professional FEM package, ANSYS Maxwell and the author’s proprietary finite element method (FEM) code. On the basis of the conducted tests and analysis of the obtained results, the “optimal” magnetic circuit structure of the PMSM motor was selected. The prototype motor was subjected to measurement to verify the developed models and the proposed design approach that takes advantage of finite element analysis (FEA).

Use of Finite Element Method Software to Assess the Safety of a Newly Designed Electric Motorcycle Frame

Use of Finite Element Method Software to Assess the Safety of a Newly Designed Electric Motorcycle Frame

Laser Surface Transformation Hardening for Automotive Metals: Recent Progress

This article discusses recent advancements in the Laser Surface Transformation Hardening (LSTH) process applied to industrial metals. It focuses on examining the microstructure of the metal surface layer and explores different methods of performing LSTH to evaluate mechanical and surface properties. The study also investigates the utilization of various industrial lasers and simulation software for the LSTH process. The careful analysis of heat transfer and temperature control during LSTH aims to prevent the generation of surface defects like micro-cracks and surface melting. Finite element method (FEM) software effectively simulates the LSTH process. The research provides a comprehensive overview of recent developments in LSTH, categorized based on different metals and subsequent testing, highlighting its applications in the automotive industry. Electrochemical, wear, and microhardness tests are investigated to assess the potential applications of automotive metals.

Dynamic model of tissue electroporation on the basis of biological dispersion and Joule heating

Electroporation is a complex, iterative, and nonlinear phenomenon often studied through numerical simulations. In recent years, simulations of tissue electroporation have been conducted with static models. However, the results of a static model simulation are restricted to a fixed protocol signature of the pulsed electric field. In this paper, we describe a novel dynamic model of tissue electroporation that also accounts for tissue dispersion and temperature to allow time-domain simulations. We have implemented the biological dispersion of potato tubers and thermal analysis in a commercial finite-element method software. A cell electroporation model was adapted to account for the increase in tissue conductivity. The model yielded 12 parameters divided into three dynamic states of electroporation. The thermal analysis describes the dependence of tissue conductivity on temperature. The model parameters were evaluated using experiments with vegetal tissue (Solanum tuberosum) under electrochemotherapy protocols. The proposed model can accurately predict the conductivity of tissue under electroporation from 100 to 1000 V/cm. A negligible thermal effect was observed at 1000 V/cm, with a temperature increase of 0.89 °C. We believe that the proposed model is suitable to describe the electroporation at the tissue level and provides a hint of the effects on the cell membrane.

Additive manufacturing-assisted sintering: Low pressure, low temperature spark plasma sintering of tungsten carbide complex shapes

Tungsten carbide (WC), renowned for its exceptional hardness and wear resistance, plays an essential role in various industrial applications (cutting tools, abrasives, and wear-resistant components). While traditional methods involve hot pressing, Spark Plasma Sintering (SPS) combined with Additive Manufacturing (AM) offers a cutting-edge approach, utilizing high-voltage electric current and mechanical pressure for rapid densification, particularly advantageous for fabrication of complex shape components made from challenging materials like nanosized binderless tungsten carbide. The study encompasses the entire spectrum of the powder's characterization, extending to the development of an intricate finite element simulation tailored for SPS sintering. Sintering cycles underscore the exceptional quality of the powder, demonstrating full density microstructures even under low-temperature (1550 °C) and low-pressure (50 MPa) conditions. The nanosized powder exhibits minimal microstructural coarsening, reflecting the high quality of the initial pure tungsten carbide nano powder. The core of this study revolves around the methodology employed for deriving constitutive parameters, following the Skorohod-Olevsky theory of continuum sintering. The derivation methods include variations in temperature, heating regimes, and stepwise pressure application during SPS. Additionally, a grain growth model is formulated based on microstructural analysis. Critical parameters, including the apparent sintering activation energy (800 kJ/mol) and the creep law stress exponent (n = 4.0), are discussed. The article concludes with the integration of the mechanical sintering model into finite element method (FEM) software, considering thermal and electrical aspects for a comprehensive SPS-AM modeling approach and its application to complex shape production. The research aims to enhance the understanding of SPS for tungsten carbide, providing insights for its application in manufacturing cutting-edge components in challenging environments.

Modeling and Control Simulation of Power Converters in Automotive Applications

This research introduces a model-based approach for the analysis and control of an onboard charger (OBC) system for contemporary electrified vehicles. The primary objective is to integrate the modeling of SiC/GaN MOSFETs electrothermal behaviors into a unified simulation framework. The motivation behind this project stems from the fact that existing literature often relies on finite element method (FEM) software to examine thermal dynamics, necessitating the development of complex models through partial derivative equations. Such intricate models are computationally demanding, making it difficult to integrate them with circuit equations in the same virtual environment. As a result, lengthy wait periods and a lack of communication between the electrothermal models limit the thorough study that can be conducted during the design stage. The selected case study for examination is a modular 1ϕ (single phase) onboard computer (OBC). This system comprises a dual active bridge (DAB) type DC/DC converter, which is positioned after a totem pole power factor correction (PFC) AC/DC converter. Specifically, the focus is directed toward a 7 kW onboard computer (OBC) utilizing high-voltage SiC/GaN MOSFETs to ensure optimal efficiency and performance. A systematic approach is presented for the assessment and selection of electronic components, employing circuit models for the totem pole power factor correction (PFC) and dual active bridge (DAB) converter. These models are employed in simulations closely mimicking real-world scenarios. Furthermore, rigorous testing of the generated models is conducted across a spectrum of real-world operating conditions to validate the stability of the implemented control algorithms. The validation process is bolstered by a comprehensive exploration of parametric variations relative to the nominal case. Notably, each simulation adheres to the recommended operational limits of the selected components and devices. Detailed data sheets encompassing electrothermal properties are provided for contextual reference.

Analysis of Effectiveness of Combined Surface Treatment Methods for Structural Parts with Holes to Enhance Their Fatigue Life

The typical and most widespread stress concentrators in the lower wing panels of aircraft are the drain holes located on the stringer vertical ribs. These are prime sources for the initiation and development of fatigue cracks, which lead to early failure of the wing structure. Therefore, improving fatigue life in these critical areas is one of the significant issues for research. Two combined methods of surface plastic treatment in the location around drain holes are discussed in this paper. Using the finite element method and ANSYS software, we created a finite element model and obtained nonlinear solution results in the case of tension in a plate with three holes. In addition, the development of residual stress due to the surface plastic treatment of the hole-adjacent areas was taken into account. In this paper, it is shown that after surface treatment of the corresponding areas of the holes, residual stress, which exceeds the yield stress for the plate material, is induced. When combined with alternative tensile stress, these reduce the amplitude of the local stresses, thus increasing the number of stress cycles before failure. The benefits of this technology were confirmed by fatigue test results, which include the fatigue failure types of the plates. Graphs showing the impact of applicable surface treatment combined methods on the number of cycles to failure were also plotted.

An Investigation of the Energy Harvesting Capabilities of a Novel Three-Dimensional Super-Cell Phononic Crystal with a Local Resonance Structure.

Using the piezoelectric (PZT) effect, energy-harvesting has become possible for phononic crystal (PnC). Low-frequency vibration energy harvesting is more of a challenge, which can be solved by local resonance phononic crystals (LRPnCs). A novel three-dimensional (3D) energy harvesting LRPnC is proposed and further analyzed using the finite element method (FEM) software COMSOL. The 3D LRPnC with spiral unit-cell structures is constructed with a low initial frequency and wide band gaps (BGs). According to the large vibration deformation of the elastic beam near the scatterer, a PZT sheet is mounted in the surface of that beam, to harvest the energy of elastic waves using the PZT effect. To further improve the energy-harvesting performance, a 5 × 5 super-cell is numerically constructed. Numerical simulations show that the present 3D super-cell PnC structure can make full use of the advantages of the large vibration deformation and the PZT effect, i.e., the BGs with a frequency range from 28.47 Hz to 194.21 Hz with a bandwidth of 142.7 Hz, and the maximum voltage output is about 29.3 V under effective sound pressure with a peak power of 11.5 µW. The present super-cell phononic crystal structure provides better support for low-frequency vibration energy harvesting, when designing PnCs, than that of the traditional Prague type.