Commercial Finite Element Method Software Research Articles

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.

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.

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.

Sliding wear characterization of epoxy composites filled with wood apple dust using Taguchi analysis and finite element method

AbstractIn this research, a new class of composite made up of wood apple dust (WAD) and epoxy is developed using the hand lay‐up process. The impact of WAD filler on the physical and wear characteristics of epoxy‐based composites are examined. The composite samples are prepared by varying the weight content of WAD (0, 3, 6, 9, and 12 wt%). The composites are subjected to dry sliding wear testing in accordance with the L25 Taguchi design to calculate the specific wear rate (SWR). An optimum parametric combination of control factors is established for the composites to have the least amount of wear loss. The SWR of WAD/epoxy composites is also predicted using commercial finite element method (FEM) software ANSYS 2019 R2. The experimental findings are compared with the predicted wear rates of the composites. The results revealed that addition of WAD powder improved the wear resistance of the composites. A remarkable increase in tensile, compressive and flexural strength values of 34.79%, 10.12%, and 22.66% respectively, is observed. Neat polymer has tensile, compressive and flexural strengths of 48, 82, and 22.5 MPa respectively, and the values increased to 64.7, 90.3, and 27.6 MPa with addition of 12 wt% WAD. It is further observed that out of the four control factors the most influencing control factor affecting the wear rate of the composites in decreasing order are WAD content, sliding velocity, sliding distance, and normal load.Highlights In this study a natural fiber‐based waste, wood apple dust (WAD) is successfully used as a potential filler material in epoxy matrix. Physical and mechanical properties of the epoxy‐WAD composites are analyzed. Effects of filler contents on the wear behavior are studied using design of experiment. The wear rate of WAD/epoxy composites is predicted using finite element method.

Biological dispersion in the time domain using finite element method software

Biological tissue exhibits a strong dielectric dispersion from DC to GHz. Implementing biological dispersion in the time domain with commercial finite element method software could help improve engineering analysis of electrical transient phenomena. This article describes the steps required to implement time-domain biological dispersion with commercial finite element method software. The study begins with the presentation of a genetic algorithm to fit the experimental dispersion curve of Solanum tuberosum (potato tuber) to multipoles of first-order Debye dispersion. The results show that it is possible to represent the biological dispersion of S. tuberosum from 40 Hz to 10 MHz in a 4-pole Debye dispersion. Then, a set of auxiliary differential equations is used to transform the multipole Debye dispersion from the frequency domain to the time domain. The equations are implemented in the commercial software COMSOL Multiphysics. A comparison between the frequency and time domain simulations was used to validate the method. An analysis of the electric current with square-wave pulsed voltage was performed. We found that the computer implementation proposed in this work can describe the biological dispersion and predict the electric current.

Statistical Effective Diffusivity Estimation in Porous Media Using an Integrated On-site Imaging Workflow for Synchrotron Users

Transport in porous media plays an essential role for many physical, engineering, biological and environmental processes. Novel synchrotron imaging techniques and image-based models have enabled more robust quantification of geometric structures that influence transport through the pore space. However, image-based modelling is computationally expensive, and end users often require, while conducting imaging campaign, fast and agile bulk-scale effective parameter estimates that account for the pore-scale details. In this manuscript we enhance a pre-existing image-based model solver known as OpenImpala to estimate bulk-scale effective transport parameters. In particular, the boundary conditions and equations in OpenImpala were modified in order to estimate the effective diffusivity in an imaged system/geometry via a formal multi-scale homogenisation expansion. Estimates of effective pore space diffusivity were generated for a range of elementary volume sizes to estimate when the effective diffusivity values begin to converge to a single value. Results from OpenImpala were validated against a commercial finite element method package COMSOL Multiphysics (abbreviated as COMSOL). Results showed that the effective diffusivity values determined with OpenImpala were similar to those estimated by COMSOL. Tests on larger domains comparing a full image-based model to a homogenised (geometrically uniform) domain that used the effective diffusivity parameters showed differences below 2 % error, thus verifying the accuracy of the effective diffusivity estimates. Finally, we compared OpenImpala’s parallel computing speeds to COMSOL. OpenImpala consistently ran simulations within fractions of minutes, which was two orders of magnitude faster than COMSOL providing identical supercomputing specifications. In conclusion, we demonstrated OpenImpala’s utility as part of an on-site tomography processing pipeline allowing for fast and agile assessment of porous media processes and to guide imaging campaigns while they are happening at synchrotron beamlines.

Stress analysis of aluminium die-cast parts including the STL-data of pores

PurposePores and shrink holes are unavoidable defects in the die-casting mass production process which may significantly influence the strength, fatigue and fracture behaviour as well as the life span of structures, especially if they are subjected to high static and dynamic loads. Such defects should be considered during the design process or after production, where the defects could be detected with the help of computed tomography (CT) measurements. However, this is usually not done in today's mass production environments. This paper deals with the stress analysis of die-cast structural parts with pores found from CT measurements or that are artificially placed within a structure.Design/methodology/approachIn this paper the authors illustrate two general methodologies to take into account the porosity of die-cast components in the stress analysis. The detailed geometry of a die-cast part including all discontinuities such as pores and shrink holes can be included via STL data provided by CT measurements. The first approach is a combination of the finite element method (FEM) and the finite cell method (FCM), which extends the FEM if the real geometry cuts finite elements. The FCM is only applied in regions with pores. This procedure has the advantage that all simulations with different pore distributions, real or artificial, can be calculated without changing the base finite element mesh. The second approach includes the pore information as STL data into the original CAD model and creates a new adapted finite element mesh for the simulation. Both methods are compared and evaluated for an industrial problem.FindingsThe STL data of defects which the authors received from CT measurements could not be directly applied without repairing them. Therefore, for FEM applications an appropriate repair procedure is proposed. The first approach, which combines the FEM with the FCM, the authors have realized within the commercial software tool Abaqus. This combination performs well, which is demonstrated for test examples, and is also applied for a complex industrial project. The developed in-house code still has some limitations which restrict broader application in industry. The second pure FEM-based approach works well without limitations but requires increasing computational effort if many different pore distributions are to be investigated.Originality/valueA new simulation approach which combines the FEM with the FCM has been developed and implemented into the commercial Abaqus FEM software. This approach the authors have applied to simulate a real engineering die-cast structure with pores. This approach could become a preferred way to consider pores in practical applications, where the porosity can be derived either from CT measurements or are artificially adopted for design purposes. The authors have also shown how pores can be considered in the standard FEM analysis as well.

Mechanical Performance of 5-speed Manual Transmission Gearshift Bracket

The main purposes of a gear shift bracket for manual transmission are to hold the gear shift cables and acts as pivot during the gear shifting process. During the gear shifting process, the bracket experiences push and pull reciprocating forces which applied by the driver while selecting or shifting gears. This study presents the development of a simulation model to analyze the mechanical performance of a specific manual transmission gearshift bracket. Based on the simulation results, an optimized bracket design was proposed. Commercial CAD software and Finite Element (FE) Method software were used to perform the simulation. Boundary and initial conditions were applied to the FE model which was based on the real-life mechanical movement of the bracket during gear shifting process. The boundary and initial conditions included fixed position, displacement and both select and shifting loads by following actual test requirements which replicated the movement of the actual model during gear shifting process. Specific mechanical ratio formula was used to obtain the magnitude of loads that was experienced by the gear shift bracket in both select and shifting gears action. The simulation of the gearshift bracket provided outcome parameters such as total deformation, maximum stress and safety factor value. Based on the safety factor value, the model was eligible for topology optimization process and it was modified to gain the optimized model. Then, the same simulation setup was used for the optimized model. The modified design bracket was able to provide a 7% reduction in mass, a 25.15% increase in maximum deformation, a 46,78% increase in maximum stress and, a 36.74% decrease in safety factor value by comparing it to the original model. Although the modified model has lower strength, but its safety factor value is still within the minimum requirements. This concludes that the simulation model allows the manufacturer to undertake design iteration and analyze its performance without producing any physical prototypes and conduct any actual test, thus saving development cost and time.

Biomechanical Performance of Mandibular Molars with Deep Mesio-Occlusal-Distal Cavities Rehabilitated with Horizontal Posts: A 3D Finite Element Analysis.

To compare and contrast by three-dimensional finite element analysis the biomechanical performance of deep mesio-occlusal-distal cavities of mandibular molars reinforced by different sizes of horizontal fiber posts. The finite element (FE) stress analysis was performed with the ANSYS, a commercial finite element method package. Based on the evidence-based scientific data and on the mechanical properties of materials, i.e., Young's modulus and Poisson ratio, the model of a mandible and mandibular first molar was replicated. The mandibular molar models replicating the clinical scenarios were simulated, designed, and built, assuming all materials to be homogenous, isotropic, and linearly elastic as follows: Model 1 control: the model of an intact first mandibular molar. Model 2: the prepared cavity mesio-occlusal-distal is replicated by the subtraction Boolean method. The remaining thickness of dentin is 1 mm. Model 3: these were rehabilitated by three different diameters of two horizontal fiber posts. Model 3A: fiber post diameter 1 mm, Model 3B: 1.5 mm and Model 3C: 2 mm. The dimensions of the cavity, the intercuspal distance between buccal walls and lingual walls, and the distance of placement of the post from occlusal reference points were all kept constant for all three subgroups of Model 3. The cavities of Model 3 were restored with Filtek bulk-fill posterior composite. After meshing the models, loads were defined on the buccal and lingual distal cusps with a constant value of 600 N and at an angle of 45°. The results of finite element analysis are expressed as stresses, i.e., tensile compressive, shear, or a combination known as von Mises stresses. The overall von Mises stresses were as follows: Model 1:154.83 Mpa; Model 2: 376.877 Mpa; Model 3A: 160.221 Mpa; Model 3B: 159.488 Mpa; Model 3C: 147.231 Mpa. Statistical analysis of the compiled data was carried out. It was seen that there was a significant difference in stress values from the intact tooth Model 1 and cavity Model 2 (p < 0.05) with means values of 53.1 and 139.22, respectively. The means of all subgroups were comparable but there was a statistically significant difference between Model 3, i.e., 3A (67.74), Model 3B (60.47), Model 3C (53.70), and Model 2. Model 1 and Model 3C had comparable mean values. Rehabilitation of deep mesio-occlusal-distal cavities of molars with intact buccal and lingual walls with the aid of a horizontal post of any diameter has a similar stress distribution to an intact tooth. However, the biomechanical performance of a 2 mm horizontal post was exacting of the natural tooth. Horizontal posts can be included in expanding our restorative option for rehabilitating grossly mutilated teeth.

Hybrid SPH-FEM solver for metal cutting simulations on the GPU including thermal contact modeling

This paper presents a hybrid Smoothed Particle Hydrodynamics (SPH) – Finite Element Method (FEM) solver for metal cutting simulations on Graphics Processing Units (GPU). For the first time in chip formation simulation, the heat transfer between an SPH model of the workpiece, and a transient FEM temperature model for the cutting tool, is established. For validation, the performance of the modeled thermal contact between two numerical domains is compared with a commercial FEM software. The sensitivity of the implemented SPH-FEM contact parameters is investigated for the first time and further insights into the thermal modeling of cutting simulations are generated. Overall, the newly developed hybrid model saves the computational time on the cutting tool side in the pure SPH method and enables more efficient high-fidelity cutting simulations. By clearly defining the thermal contact at the tool-chip interface, the simulated tool surface temperature agrees well with the experimental measurements in the literature.

An improved model of refined zigzag theory with equivalent spring for mode II dominant strain energy release rate of a cracked sandwich beam

In this paper, an improved model, the refined zigzag theory with equivalent tangential spring (RZTES) in conjunction with the sub-laminate approach, for cracked sandwich beam (CSB) is developed. The kinematics of the refined zigzag theory (RZT) assumes that the axial displacements of a sandwich beam follow piecewise linear distribution across the thickness. This theory can accurately model the zigzag displacement in a sandwich beam without delamination. However, the kinematics of the RZT does not meet the deformations near the crack tip, which contain more complicated displacement distributions. It results in underestimations of both the compliance and mode II dominant strain energy release rate (SERR). The RZTES is developed to correct the inaccuracies due to this underestimation. In RZTES, an equivalent spring is inserted to decrease the local stiffness near the crack tip so that the compliance of the CSB is increased. Based on the procedure developed in this study, the equivalent spring constant can be determined according to the Young’s modulus and shear modulus of the core. Then a gap determined from the equivalent spring constant can be determined and be used to re-formulate the continuity conditions at the crack tip of a CSB. In order to validate RZTES, the CSB is calculated by commercial finite element method (FEM) software ANSYS with two-dimensional elements. The compliances are also validated by experiments. The results show that the RZTES can increase both the compliance and strain energy release rate. The case studies with various ranges of geometric parameters and material properties of the CSB are solved by RZT, RZTES and ANSYS. For the case with soft core or thick beam thickness, the calculation results by RZT need more corrections. By comparing RZT, both the compliances and SERRs calculated by RZTES are more accurate.

Electromagnetic scattering of a plane wave by a perfectly conducting elliptic cylinder near a plane surface

In this paper, we present a rigorous analytical and numerical method to evaluate the scattering of a plane electromagnetic wave by an infinite, perfectly conducting elliptic cylinder parallel to a non-perfectly reflecting plane surface. The analytical solution is based on the spectral domain method and the plane-wave expansion of the elliptic cylindrical waves and is applicable in a broad variety of cases in which the properties of the plane surface may be expressed by means of a reflection coefficient. The proposed approach is suitably implemented in a specific computational code to achieve a numerical solution. Results of validation trials, performed by using finite element method commercial software, are provided.

The Effect of the Bridge’s Angle during Porthole Die Extrusion of Aluminum AA6082

During the porthole die extrusion, the separated metal streams are welded together in the welding chamber. The conditions under which this occurs and the integrity of weld seam in the extrudate are impacted by the design of the bridge, including features such as its shape and dimensions. In this research, the commercial finite element method (FEM) software package, DEFORM, was used to run a series of simulation experiments in order to quantitatively understand the relationship between the bridge design and the thermal mechanical history experienced by the material during welding and the impact this has on final weld seam quality. The bridge can be roughly divided into two parts: the lower part, close to the welding chamber, and the upper part, which initially split the billet into metal streams. The results showed that increasing the lower bridge angle led to slightly higher extrusion loads and higher extrudate exit temperatures. As the lower bridge angle increased, creating a streamlined profile to a blunt profile, a dead metal zone formed under the bridge that produced higher strains near the surface of the material. In contrast, changes to the geometry of the upper bridge had little effect on the porthole die extrusion process or the thermal mechanical conditions experienced by the material.

Dynamical analysis and vibration estimation of a flexible plate with enhanced active constrained layer damping treatment by combinatorial neural networks of surrogates

The effective estimation of the vibration of spacecrafts are frontier issues in the aerospace industry. But the vibration of aerospace components such as space solar panels and flexible manipulators under large overall rotating motion is usually very complex due to strong nonlinearity and often requires a lot of repetitive and burdensome calculations. Artificial neural network (ANN) is composed of interconnected neurons, and a surrogate model can be established to effectively predict the mechanical characteristics. In addition, the computational efficiency will be greatly improved if the object is changed from the model that is established by commercial finite element method (FEM) software or numerical calculations to the surrogates. However, the stochasticity of the estimation by single neural network is inevitable, and some neural networks much rely on the initial weight and threshold. This paper will implement a new combinatorial strategy that relies on multiple neural network models, which have different activation functions and regression feedback processes based on reasonable selection of sample points. To solve the elongated training time led by comparing these neural networks, genetic algorithm (GA) is used to optimize the iteration speed of one neural network when finding the optimal output value. Thus, better estimation accuracy will be achieved by designing an algorithm to combine these combinatorial neural networks of surrogates (CNNS). Based on the proposed method, the vibration estimation of a rotating flexible plate with enhanced active constrained layer damping (EACLD) treatment, and the vibration suppression capacity of the composite structure under various operating conditions will be investigated.

ABAQUS and ANSYS Implementations of the Peridynamics-Based Finite Element Method (PeriFEM) for Brittle Fractures

In this study, we propose the first unified implementation strategy for peridynamics in commercial finite element method (FEM) software packages based on their application programming interface using the peridynamics-based finite element method (PeriFEM). Using ANSYS and ABAQUS as examples, we present the numerical results and implementation details of PeriFEM in commercial FEM software. PeriFEM is a reformulation of the traditional FEM for solving peridynamic equations numerically. It is considered that the non-local features of peridynamics yet possesses the same computational framework as the traditional FEM. Therefore, this implementation benefits from the consistent computational frameworks of both PeriFEM and the traditional FEM. An implicit algorithm is used for both ANSYS and ABAQUS; however, different convergence criteria are adopted owing to their unique features. In ANSYS, APDL enables users to conveniently obtain broken-bond information from UPFs; thus, the convergence criterion is chosen as no new broken bond. In ABAQUS, obtaining broken-bond information is not convenient for users; thus, the default convergence criterion is used in ABAQUS. The codes integrated into ANSYS and ABAQUS are both verified through benchmark examples, and the computational convergence and costs are compared. The results show that, for some specific examples, ABAQUS is more efficient, whereas the convergence criterion adopted in ANSYS is more robust. Finally, 3D examples are presented to demonstrate the ability of the proposed approach to deal with complex engineering problems.

Numerical simulation of an electromechanical brake concerning associated difficulties

The biggest challenge in developing any type of brake (or any other actuator) is overcoming its inherent disadvantages. Brakes that use materials whose rheological properties change under the influence of an external magnetic field are called magnetorheological brakes. In addition to the mechanical issues, magnetorheological brakes are troubled with cooling, sealing, settling, fluids' gap size, etc. Furthermore, there are issues with brake’s magnetic field density distribution and propagation. The poor distribution of the magnetic field density through the body of the magnetorheological brake is one of these inherent disadvantages. Magnetorheological’s brake magnetic circuit modeling forms the basis for further development. This paper is part of ongoing research into the feasibility of using magnetorheological brakes in automotive applications. Certain points of the numerical simulation process are addressed. The research uses part of the results from previous numerical simulations, carried out using commercial finite element method software - COMSOL Multiphysics, AC/DC module, and results from the previous experiments.

A SFBEM–FEM coupling method for solving crack problems based on Erdogan fundamental solutions

The boundary element method (BEM) has proven to be an efficient approach for crack analysis in fracture mechanics, while its versatility in application to crack problems of complex structures with irregular boundaries deserves further attention. In this study, to improve the applicability to complex crack analysis, a cracked superelement is first established with BEM to model the near-crack region, and the crack problem is then solved within the frame of finite element method (FEM). The stiffness matrix of the cracked superelement is formulated using the spline fictitious boundary element method (SFBEM) based on the Erdogan fundamental solutions for an infinite plane with a single crack. The proposed superelement is further incorporated into a finite element mesh to simulate the behaviour of the crack zone, and the governing equation of the crack problem is finally established and solved using the typical procedure of FEM. After obtaining the nodal displacements of the superelement, the stress intensity factors (SIFs) of crack tips can be obtained by a backward analysis with SFBEM. The accuracy and efficiency of the proposed SFBEM–FEM coupling method are demonstrated by two numerical examples involving a rectangular plate with a central crack and a square plate with 100 horizontal cracks. The present approach is further applied to the analysis of the SIFs of multiple cracks exposed in a steel anchorage box for a hanger of a suspension bridge, which indicates the merging of the cracked superelements to the commercial FEM software is computationally efficient for the analysis of complex structures with multiple cracks.

Electroforming 4.0 – Significance, Challenges & Optimisation

Since the concept of “Industry 4.0” was introduced the most competitive industrial manufacturers around the world have been trying to secure sustainable, high quality, low-cost technological developments. Alongside the total computerisation of manufacturing and fabrication, new manufacturing technologies will need to arise to replace traditional production lines with more flexible ones able to support the evolved industrial needs of the next transition.Among these technologies, additive manufacturing processes have significantly contributed to the rapid transformation of the industrial landscape during the last decade. In particular, “low-volume/high-value" industrial sectors, such as the aerospace, marine and energy industries, are expected to benefit from this kind of approaches. This is mainly because manufacturing of larger volumes of customised products could be achieved in that manner, followed by a reduction of industrial and economic waste, decrease in the cost of operation and reduction of environmental impact.Electroforming is increasingly gaining recognition as a promising and sustainable additive manufacturing process of the “Industry 4.0” era. Numerous important laboratory-scale studies try to shed light onto the pressing question as to which are the best industry approaches to be followed towards the process’s optimisation. However, for electroforming to be successfully optimised and efficiently applied in industry, systematic scale up studies need to be conducted. Well-informed simulations can provide a much-desired insight into the novelties and limits of the process, and therefore, scaling up modelling studies are of essence.Additive-free nickel electroforming, in particular, could also play an important role in the much-desired “green” transition of lightweight manufacturing. Even within the currently available infrastructure, the same electroforming reactors can remain in use for years if properly maintained, the stainless-steel cathodes (mandrels) and titanium anode baskets are re-usable and recyclable, while process efficiency (especially for sulphamate baths) is usually close to 100%. Hazards arising from the use of nickel can easily be mitigated, while developments on nickel recovery and recycling are increasingly promising.Modelling studies can help further, towards process optimisation at all three (system, process and product) sustainability levels. Since electroforming’s final products can be of various scales and requirements, well-informed modelling studies could assist with efficient tooling and process design for different cases. That way, key process parameters, such as the deposition duration, applied currents, heating and agitation requirements, or even quantitative material requirements, could be fine-tuned on a case-by-case basis.Therefore, to better understand the process and its potential, a systematic nickel electroforming modelling approach was followed; starting from primary current distribution (PCD) simulations which depend solely on the system’s geometry, moving forward to introducing kinetic contributions through secondary current distribution (SCD) studies and, finally, developing tertiary current distribution (TCD) models completed by the introduction of mass transfer effects.In practice, time-dependent nickel electroforming models of different scales were developed and studied using COMSOL Multiphysics®, a finite element method commercial software. The models were experimentally validated. Electrochemical experimental data, collected via polarisation studies, were used as input for the models. The boundary conditions at the cathode and anode were based on the overall nickel reduction and dissolution reactions, respectively. Current-potential data was used to fit the exchange current density, equilibrium potential, limiting current, as well as anodic and cathodic charge transfer coefficients.Modelling and experimental results were interpreted in terms of the deposit thickness distribution and uniformity. PCD modelling offered a preliminary insight into the system’s electrochemical behaviour, confirmed the direct relation between current and thickness distribution, and highlighted the dependence of the simulated results on the setup’s geometrical configuration. SCD simulations were subsequently used for mesh, geometry, and kinetic sensitivity studies, to be followed by TCD simulations involving multiple species and reactions.These studies confirmed that commercial simulation software can reliably model precision electrodeposition processes, such as electroforming. At the same time, the models’ credibility is dependent on good quality input parameters, derived through practical experiments. Among other observations, simplified SCD models were proven to be efficient in modelling processes not affected by tertiary phenomena. Targeted investigations on how the size, geometry and configuration of an electroforming reactor can affect the final product suggested time- and cost-effective modifications of the setup itself which can lead to process optimisation. Overall, computational studies allowed for the development of a study approach aiming to optimise both electroforming simulations and application in production lines. Figure 1

Vibration-Based Approach to Measure Rail Stress: Modeling and First Field Test.

This paper describes a non-invasive inspection technique for the estimation of longitudinal stress in continuous welded rails (CWR) to infer the rail neutral temperature (RNT), i.e., the temperature at which the net longitudinal force in the rail is zero. The technique is based on the use of finite element method (FEM), vibration measurements, and machine learning (ML). FEM is used to model the relationship between the boundary conditions and the longitudinal stress of any given CWR to the vibration characteristics (mode shapes and frequencies) of the rail. The results of the numerical analysis are used to train a ML algorithm that is then tested using field data obtained by an array of accelerometers polled on the track of interest. In the study presented in this article, the proposed technique was proven in the field during an experimental campaign conducted in Colorado. A commercial FEM software was used to model the rail track as a short rail segment repeated indefinitely and under varying boundary conditions and stress. Three datasets were prepared and fed to ML models developed using hyperparameter search optimization techniques and k-fold cross validation to infer the stress or the RNT. The frequencies of vibration were extracted from the time waveforms obtained from two accelerometers temporarily attached to the rail. The results of the experiments demonstrated that the success of the technique is dependent on the accuracy of the model and the ability to properly identify the modeshapes. The results also proved that the ML was also able to predict successfully the neutral temperature of the tested rail by using only a limited number of experimental data for the training.

EpSFEM: A Julia-Based Software Package of Parallel Incremental Smoothed Finite Element Method (S-FEM) for Elastic-Plastic Problems

In this paper, a parallel Smoothed Finite Element Method (S-FEM) package epSFEM using incremental theory to solve elastoplastic problems is developed by employing the Julia language on a multicore CPU. The S-FEM, a new numerical method combining the Finite Element Method (FEM) and strain smoothing technique, was proposed by Liu G.R. in recent years. The S-FEM model is softer than the FEM model for identical grid structures, has lower sensitivity to mesh distortion, and usually produces more accurate solutions and a higher convergence speed. Julia, as an efficient, user-friendly and open-source programming language, balances computational performance, programming difficulty and code readability. We validate the performance of the epSFEM with two sets of benchmark tests. The benchmark results indicate that (1) the calculation accuracy of epSFEM is higher than that of the FEM when employing the same mesh model; (2) the commercial FEM software requires 10,619 s to calculate an elastoplastic model consisting of approximately 2.45 million triangular elements, while in comparison, epSFEM requires only 5876.3 s for the same computational model; and (3) epSFEM executed in parallel on a 24-core CPU is approximately 10.6 times faster than the corresponding serial version.