FEM Technique Research Articles

Numerical Analysis of the Influence of the Rolling Speed on the Cold Rolling under Specific Thermal Condition of the AA 5052-O Aluminum Alloy

In this study, the behavior of the rolling process of the AA 5052 aluminum alloy plate has been investigated using numerical data. An FEM technique was utilized in order to make a prediction regarding the impact that the rolling speed has on the cold rolling of the AA 5052-O aluminum alloy. In order to carry out the simulation procedure, the static structure tool was considered. The geometry of the situation. The total deformation, stresses, including von and normal stresses, and energy have all been the subject of investigation for the simulation that is now being performed. In both the axial and radial directions, the deformation has been investigated using numerical methods. It is possible to get a maximum result of 550 and 140 mm, respectively. at a speed of 200 revolutions per minute, the energy reached 8 kilojoules. It has been established that both normal and von mises stresses have been established. A total of 3.6 and 1.9 MPa are the numerical results that the stress has produced.

Application of FEM and Artificial Intelligence Techniques (LRM, RFM & ANN) in Predicting the Ultimate Bearing Capacity of Reinforced Soil Foundation

In this research paper, the behavior of shallow footing with square and rectangular shapes over geosynthetic reinforced soil was studied. A novel geogrid called “3D tube-geogrid” was utilized for this work. The impact of various reinforcement parameters, including the depth of the final layer (z), length (l), inclination (α), filler material used inside the geogrid tube, relative soil density, and the tensile stiffness of the geogrid (EA), were analyzed by running numerical simulations using PLAXIS 3D V20 software. The simulated data were used to quantify the relationship between the ultimate bearing capacity of the soil and the reinforcement parameters. Several artificial intelligence (AI) techniques, such as linear regression analysis, a random forest model, and an artificial neural network (ANN), were employed on the generated dataset. To evaluate the preciseness of these techniques, various statistical indicators, such as the squared correlation coefficient (R2), mean absolute percentage error (MAPE), mean squared error (MSE), and root-mean-square error (RMSE), were calculated, and error percentages of 20.98%, 12.5%, and 6.4% were obtained for the linear regression, random forest, and ANN, respectively. The numerical study determined the optimal values of the reinforcement parameters length, z/B, inclination, and filling material to be 4B, 3, 0°, and aggregate, respectively.

Evaluation and mitigation of deformable image registration uncertainties for MRI-guided adaptive radiotherapy.

We evaluate the performance of a deformable image registration (DIR) software package in registering abdominal magnetic resonance images (MRIs) and then develop a mechanical modeling method to mitigate detected DIR uncertainties. Three evaluation metrics, namely mean displacement to agreement (MDA), DICE similarity coefficient (DSC), and standard deviation of Jacobian determinants (STD-JD), are used to assess the multi-modality (MM), contour-consistency (CC), and image-intensity (II)-based DIR algorithms in the MIM software package, as well as an in-house developed, contour matching-based finite element method (CM-FEM). Furthermore, we develop a hybrid FEM registration technique to modify the displacement vector field of each MIM registration. The MIM and FEM registrations were evaluated on MRIs obtained from 10 abdominal cancer patients. One-tailed Wilcoxon-Mann-Whitney (WMW) tests were conducted to compare the MIM registrations with their FEM modifications. For the registrations performed with the MIM-CC, MIM-MM, MIM-II, and CM-FEM algorithms, their average MDAs are 0.62±0.27, 2.39±1.30, 3.07±2.42, 1.04±0.72mm, and average DSCs are 0.94±0.03, 0.80±0.12, 0.77±0.15, 0.90±0.11, respectively. The p-values of the WMW tests between the MIM registrations and their FEM modifications are less than 0.0084 for STD-JDs and greater than 0.87 for MDA and DSC. Among the three MIM DIR algorithms, MIM-CC shows the smallest errors in terms of MDA and DSC but exhibits significant Jacobian uncertainties in the interior regions of abdominal organs. The hybrid FEM technique effectively mitigates the Jacobian uncertainties in these regions.

Simulation of viscoelastic free-surface flows with the Particle Finite Element Method

Viscoelastic fluids are central in numerous applications from polymer manufacturing to the pharmaceutical industry and biological research. However, since analytical solutions are generally not available or too complex, it is common practice to study free-surface viscoelastic flows through numerical simulation techniques. This work proposes the use of the so-called particle finite element method (PFEM), a Lagrangian approach combining standard FEM techniques with a remeshing strategy. The PFEM is able to efficiently handle mesh distortion and to accurately track the free-surface evolution. Therefore, it is exploited in this work to deal with large displacements problems in the context of nonlinear viscoelasticity. An implementation of the Oldroyd-B constitutive model in the PFEM framework is here presented including details regarding how to deal with the transfer of the internal variables during remeshing events. Additionally, an innovative approach to impose unilateral Dirichlet boundary conditions ensuring optimal mass conservation is presented. The implementation is verified with two free-surface highly viscous benchmark flows: the impacting drop and the jet buckling problems. The results show perfect agreement with those obtained with other numerical techniques. The proposed framework opens the way for using PFEM in various applications, ranging from polymer extrusion to more sophisticated scenarios involving viscoelastic and viscoelasto-plastic constitutive laws.

First considerations on the supporting structures of FCC-ee booster and collider in the arc regions

In 2022, the FCC Feasibility Study management mandated a working group to analyse the best configuration of the FCC-ee tunnel in the arc regions, in view of the construction of a mock-up of the arc half-cell. One of the main and most challenging goals of the study, named FCC-ee Arc Half-Cell Mock-up Project, was to perform a preliminary investigation on the principles of supporting the Short-Straight Sections and dipoles of the half-cells, both for the booster and for the collider machines. This is an important input needed for the choice of the best configuration of the relative placement of the booster with respect to the collider. The structural stiffness, mass and stability of the supporting structures must be optimized to minimize the vibrations transmitted/transferred to the magnetic system of the accelerators by elements such as pumps, water cooling system, beam thermomechanical stresses, powering elements, etc. To perform the study, tools such as CAD software, FEM and analytical techniques were employed. This paper summarizes the preliminary design concepts and the results of the simulations performed.

Vibration reduction technology using modal energy propagation analysis method

Since the noise generated by mechanical structures affects the merchantability, it is important to predict the noise and vibratory characteristics at the first design stage. The frames and panels or trim parts in automobiles are coupled systems of the rigid and flexible substructure. In these systems, vibration of the flexible structures often becomes one of the major noise sources when the excitation force is applied to the rigid structure. FEM and modal analysis technique are not sufficient to carry out the effective low noise design in higher frequency because of high modal density and complexity of mode shape. Modal energy propagation method, proposed in this paper, is based on the mode synthesis method and the vibration power flow between the eigen modes of the rigid and flexible structures. Previous studies have verified that the vibration level can be reduced by extracting modes that contribute highly to the vibration power flow between subsystems and changing their characteristics. In this report, we present the results of applying this method to a coupled system of a body and panel structures in automobiles and verifying its validity. The structural modifications obtained from this analysis method were verified for their effectiveness in decreasing vibration.

Coach crashworthiness and failure analysis during a frontal impact

Accidents involving coaches may endanger the physical integrity of their occupants, since the driver stands very close to the collision region. In the event of a frontal impact, there is a violation of the driver's residual operational space, which depends on the energy of the crash, and this may jeopardize the driver's safety. The most decisive factors in achieving a successful design of structural vehicles is to design innovative solutions that safely control the high energy released as a consequence of the high accelerations involved during impacts. Long-course coaches currently lack design techniques and technologies to absorb in a controlled way the kinetic energy released in the collision. Thus, to fulfill this gap in the passive safety of these vehicles, it is necessary to conduct structural optimization research, to improve the passive safety in the eventual event of a frontal collision. The main goal of this research is to develop new solutions for passive safety used in coaches. To this end, a feasibility study involving experimental and numerical techniques was conducted to assess the improvement of driver safety in case of a frontal impact. This study addresses the need for improved experimental validation and fills a literature gap by developing a realistic testing system and incorporating advanced monitoring techniques for evaluating frontal collisions in vehicles, so a M3 Class III coach was used to conduct this study. Experimentally, the vehicle was subjected to a frontal crash test, whereby the ECE Regulation R29 was considered as the baseline, despite focusing on the certification of heavy vehicles with separate driver's cab. Since no standards are available focusing on coaches, the ECE R29 was used and adapted to the studied model. The experimental testing setup comprises a 2500kg pendulum supported by two steel bars was used. When released it collides with the structure, anchored to the ground, with an energy of 55kJ. Monitoring techniques were employed to track the structure, namely Digital Image Correlation (DIC), strain gauges, and accelerometers. These were placed at specific points to accurately assess the damage evolution of the structure. The experimental results were used to validate the numerical results, obtained using VPS/PamCrash® by FEM techniques. The frontal crash simulation was performed using the Finite Element Method, with an explicit dynamic analysis. Strain evolution, accelerations, and displacements were obtained and compared with the experimental results. Furthermore, the evolution of the kinetic energy is plotted and compared with the reference value of the standard. Through the different obtained outcomes, a determination could be made whether the current models meet the safety criteria or whether a proposed solution is required to enhance its performance. According to the standard guidelines, the present structure has no potential to meet the essential safety requirements. In the future, new alternatives should be explored, leading to a structure that can efficiently absorb all the energy released in the experiment under controlled conditions.

Prediction of various defects and material flow behavior during dissimilar FSW of DH36 shipbuilding steel and marine grade AA5083 using FE-based CEL approach

Dissimilar friction stir welding (FSW) of steel-Al is a very tedious job. Inappropriate welding process parameters can lead to the initiation of inevitable defects associated with dissimilar FSW processes. These can be presented as tunnel defects, void generation, excessive flash formation, and other surface irregularities. Using conventional experimental trials makes it usually challenging to identify such defects. This research adopted an Abaqus/Explicit® framework utilizing a 3D thermo-mechanical based coupled Eulerian-Lagrangian (CEL) methodology. In order to predict commonly observed defects in the FSW process, the proposed FEM uses the volume of fluid approach. By monitoring the material flow into and out of the computational/void domain, the suggested framework has made it feasible to predict surface, sub-surface, and volumetric defects. Defect formation is studied at a constant tool rotation speed of 875 rpm, welding speed of 90 mm min−1, and tilt angle of 0°. Tilt angles of 0° caused welding joints with a small tunnel defect. Thermal history, axial force variation, and material flow behavior are all strongly aligned with the principle of defect generation. An experimental trial has been conducted to validate the proposed finite element model. The previous analysis found that the average axial force closely matches the welding-related experimental findings with a percentage error of 7.85%. While a proportion error of approximately ∼0.57% was found between the compared numerical and experimental diameters of the pin end-hole defect. Furthermore, the proposed model accurately predicted the process of material flow along the thickness direction of the workpiece. It was seen that the stress generated at the root of the flashes reached a higher value ranging between 485.6 and 582.7 MPa. Finally, a good agreement between the numerical results and the experimental trial was established, showing the robustness of the developed computational FEM technique.

On the fracture behavior of molar teeth with MOD cavity preparation

Mesial-occlusal-distal (MOD) cavity preparations are commonly used to restore damaged teeth. While numerous in vitro cavity designs have been devised and tested, no analytical frameworks for assessing their resistance to fracture seem to exist. This concern is addressed here by resorting to a 2D slice specimen cut from restored molar teeth with rectangular-base MOD cavity. The evolution of damage due to axial cylindrical indentation is followed in situ. The failure begins with a rapid debonding along the tooth/filler interface and continues with unstable cracking from the cavity corner. The debonding load qd is fairly fixed while the failure load qf is insensitive to the presence of filler, increasing with cavity wall thickness h and reducing with cavity depth D. The growth of the corner crack is studied using a 2D fracture analysis in conjunction with the FEM technique. The ratio h = h/D emerges as a viable system parameter. A simple expression for qf given in terms of h and dentin toughness KC is developed that predicts well the test data. In vitro studies on full-fledged molar teeth with MOD cavity preparation show that the fracture resistance of filled cavities often exceeds by a large margin that of unfilled ones. Indications are that this may reflect load sharing with the filler. Thus, the fracture resistance of the unfilled cavity provides a lower bound to a compromised MOD filling after long-term aging in the mouth. This bound is well predicted by the slice model. Finally, it is recommended that MOD cavities be prepared, if applicable, such that h > D regardless of the tooth size.

Ultrasonic and FEM residual stress measurement in dissimilar St37–St52 welding

Numerous industries, like the military, the oil and gas industry, etc., rely heavily on dissimilar welding. The welding process leaves the structure with a variety of defects, such as residual stress, that degrade its performance and static and fatigue properties. Consequently, weld residual stress must be accurately measured. In this study, ultrasonic and finite element techniques are developed to assess the residual stress in dissimilar St37/St52 welding. In addition, hole-drilling technique is employed to confirm FEM and ultrasonic data. Probe fixture is designed and built for ultrasonic stress measurement, and the acoustoelastic coefficient is measured in St37 and St52. In welding finite element analysis, the Goldak model is used as the heat source, the Brekstad model is employed as the heat loss, and the Dflux subroutine is developed to apply the heat source to the weld line using the sedimentary method. The FEM and ultrasonic data are in good correlation with the hole drilling results (maximum error of 9%). The findings indicate that there is a high degree of concordance between the data gathered by FEM and ultrasonic technique (with error less than 1.75% at the weld zone).

Use of Sound "PHONONS' in the modelling and Optimisation of automotive acoustic systems in 3D

Automotive manufacturers demand components with an ever higher acoustic performance combined with lower environmental impact, tuned to the emerging EV market, and are pressured into reducing lead times and prototype investment. Consequently, there is a desire for enhanced simulation techniques, utilizing advanced methods. The three-dimensional aspect of many palliative treatments can be shown to afford significant benefits to their acoustic performance, both in their transmission loss and random incidence absorption characteristics. Virtual system engineering enables construction fundamentals to be created in CAD, but often acoustic treatments are chosen based on flat sample performance or simple power balance models. These do not tell the complete story. Current acoustic simulation techniques such as SEA, may present the model in a 3D environment to aid in visualization but, solving is done on a 2D matrix basis, and does not account easily for diffusion and refractive interaction caused by the complex shape of the component under investigation. BEM and FEM techniques are 3D based simulations but have a host of limitations due to mesh density and available processing power. Constructing models of individual palliatives such as wheel arch liners, dash insulations or carpets using such techniques may be of academic interest but of restricted use in the pressured world of component design and manufacture. It is not helped by the need to furnish the model with accurate, validated, material performance data. A modelling procedure was required that could import component CAD from the product design team and rapidly create an acoustic model that could accurately predict its performance in both a transmission loss suite and associated random incidence "Alpha cabin" absorption test. Thus, short circuit the need for at least one if not more prototype test phases or enable quotations for new business to be formulated with a higher degree of clarity. Subsequently to export results from this model into a range of "full vehicle" modelling environments or compare to prototype test results. After considerable research the authors created and validated a toolbox approach using a combination of open-source code together with bespoke modifications and defined processing procedures.

An X–FEM technique for numerical simulation of variable-density flow in fractured porous media

Solute transport is one of the major topics in geological studies. Fracture is a significant characteristic of natural porous media, where the solute can transport due to its higher density with respect to the density of fluid. As the solute migrates in the medium, the density of the fluid changes with time. In this paper, the mass transport problem in the fractured porous media is modeled using the extended finite element method (X–FEM). An advection-diffusion equation is adopted to define the transport phenomenon in conjunction with the continuity equation of fluid. Transport regimes including diffusion, dispersion and advection are taken into the computational model. The presence of fractures within a porous medium substantially affects the transport behavior. In order to resolve the issue of discontinuity in the field variables, the X–FEM is implemented to discretize the discontinuity of medium. The Newmark integration scheme is adopted to discretize the governing equations in time domain. The nonlinear equations are solved by the Newton-Raphson iterative technique in a fully coupled manner. Finally, in order to illustrate the performance of the proposed computational model, two conventional problems, including the Schincariol problem and the Elder problem as well as the fractured Elder problem are solved numerically. Different patterns of fractures including horizontal and vertical intersecting cracks are adopted to study the effect of fracture density as well as the capability and versatility of the proposed computational model. The method is described in details and the pitfalls of the whole approach are demonstrated.•The density-driven fluid flow in naturally fractured porous media is modeled using an enhanced–FEM technique.•The effect of fractures (faults) in the porous medium is investigated by modeling the transport of saltwater in the fractured Elder problem.•The proposed computational model provides an accurate prediction of subsurface hydrology for a field-scale closed desert basin.

Collapse pressure prediction of mechanically lined pipes using FEM and machine learning techniques

Mechanically lined pipe, which proves to be an economical and reliable way to transport corrosive hydrocarbons, has been used in many offshore projects. The presence of liner and the manufacture-induced changes in mechanical properties for both tubes are expected to affect the collapse performance of lined pipes, which, however, are not suitably captured by the current DNV formula. To this end, a dedicated numerical framework, including the axisymmetric and three-dimensional finite element models, was presented to simulate the manufacturing process and the evolution of the external collapse. Two types of commonly used lined pipes, unbonded (LP) and bonded (LPB), were considered. The results indicate that the DNV prediction mostly overpredicts the collapse pressure of typical LP pipes but underestimates that of the LPB cases. Furthermore, the parametric study of essential variables of the problem reveals that in addition to the strong effect of diameter-to-thickness ratio and initial ovality, the impact of the material hardening and plastic expansion history cannot simply be ignored. Thus, the machine learning technique was applied as a substitute resolution to evaluate the critical collapse capacity of lined pipes. Four algorithms, including RF, MLP, KNN, and SVM, were developed based on a dataset of 86,400 cases involving nine variables. Based on the assessment of typical statistical metrics, it was found that all four machine learning models outperformed the DNV formula. Among them, RF had the best prediction performance, while KNN had the lowest precision among the chosen surrogate models.

MOMENT FINITE ELEMENT FOR SOLVING 3D ELASTICITY PROBLEMS

The implementation of a new 8-node finite element for solving 3D elasticity static problems is considered. The idea of this finite element is based on the projection of a rare mesh FEM scheme into a space of lower dimension. The resulting scheme of the 8-node hexahedral finite element has a number of features compared to the scheme of the classical 8-node polyline element. This is one integration point in the element compared to eight in the classical element, as well as the presence of four parameters that allow you to adjust the convergence of the computational process. In a given finite element, the stresses as well as their moments (three bending and one torsional) are assumed to be constant within the element. Also, the continuity of displacement fields is preserved only in the nodes of finite elements. This circumstance is not a disadvantage and is characteristic of many new numerical FEM schemes (suffice it to mention the recently actively developed direction of the discontinuous Galerkin method). The issues of using this finite element in solving the well-known problem of increased shear stiffness (shear locking) of a number of well-known FEM schemes are discussed. The problem of hourglass instability, which is typical for FEM schemes with reduced integration and a number of other numerical schemes, in particular, the Wilkins scheme, which is popular in solving dynamic elasticity and plasticity problems, is also considered. The implementation of a technique for the numerical solution of three-dimensional static problems of the theory of elasticity on the basis of a given finite element within the framework of the traditional FEM technique using a vector-matrix notation is described. The results of solving test static problems of elasticity theory are presented.

Analysis of the influence of L-PBF porosity on the mechanical behavior of AlSi10Mg by XRCT-based FEM

This work aims to present an XRCT-based FEM methodology to assess the influence of porosity defects on the mechanical behavior and failure of L-PBF AlSi10Mg components. Hence, the influence of defects on performance is estimated by means of XRCT scanning and analysis of porosity features, followed by mechanical FEM modelling of digitalized components. For this purpose, some test specimens with induced artificial porosity were manufactured by L-PBF, according to ASTM E8/E8M. Once this is done, inspection and defect characterization were carried out by means of XRCT. Porosity features such as void size, shape and location, apart from porosity percentage, were analyzed. Then, tensile tests were carried out, followed by further inspections by XRCT in order to research the relationship between the fracture level and the porosity of the as-built sample. Afterwards, virtual tensile tests of XRCT-ed specimens were modeled by FEM technique. Results obtained by the FEM model were well-correlated with the tensile experimental results to predict both ultimate tensile strength and elongation at fracture of each specimen, showing errors below 5.2%. However, the results of the final fracture level predicted by FEM analysis reveal that possibly underestimated and/or non-detected defects on the AlSi10Mg specimens seem to influence the accuracy of the fracture level prediction in some samples. Thus, XRCT arises as an ideal technology for the assessment of L-PBF-ed components.

Defect Detection and Characterization in Concrete Based on FEM and Ultrasonic Techniques.

In order to estimate the crack depth in concrete using time-of-flight, finite element analysis and experiments were performed on non-cracked concrete blocks and 45 mm and 70 mm vertical cracks. As a result of measuring the time-of-flight change by changing the positions of the transmitter and receiver, it was confirmed that the finite element analysis results agreed with the experimental results, and high accuracy was confirmed by various formulas for calculating the depth of defects using the obtained experimental measurements for comparison. In addition to the verification of the simulation and experimental theory, research was conducted through actual field cases, and methodologies for crack detection and depth evaluation for concrete structures were presented, and furthermore, the expected effects of improving the soundness and safety of structures were shown.

Nonlinear radiation phenomena for Casson–Maxwell nanoliquid flow with chemical reactions

The viscoelastic characteristics of an incompressible, axisymmetric Casson–Maxwell nanoliquid flow between two stationary discs were examined in this paper. Two porous discs are constrained for uniform injection. The Christov model is used in conjunction with the Buongiorno model. In an energy equation with a nonlinear form, thermal radiation characteristics are used. In the current continuation, the impact of chemical reactions is taken into account, making the work more adaptable. Using appropriate transformations, the constructed model was transformed into a dimensionless form. The solution is obtained by employing the FEM technique. The related parameters are described using physical results. The radial velocity distribution at the center line was reduced using a magnetic parameter and a Casson parameter. When the Brownian motion constant and radiation parameter are increased, the temperature distribution of nanoparticles enhances. Furthermore, the rate of the reaction increases in the presence of a chemical reaction. Pearson's correlation coefficient was used to discover a relationship between the Sherwood and Nusslet numbers. To determine the linear relationship between variables, the t-test method is used.

Electrical magneto hydrodynamic Jeffrey fluid flow with thermal radiation through stretched cylinder

The current study investigates the effects of electrical and magnetic fields on the stagnation point in Jeffrey fluid flow along a stretched cylinder with thermal radiation and chemical reaction. The Cattaneo-Christov model with double stratification and thermal relaxation was used. Heat and mass transfer are investigated. Governing partial differential equations are converted to ordinary differential equations using similarity transformation. FEM technique is used to calculate the numerical solution of a set of nonlinear coupled equations with coding implementation in MATLAB. The numerical outcomes of current work are more significant when they are correlated with previous work. The interest in computational attempts at the formation of boundary layers for concentration distribution, fluid velocity, and temperature increases as significant parameters are varied. The main outcomes of this study are that increasing electrical effects is to decreases fluid velocity while increasing magnetic parameters is to decreases the flow velocity. Another effect is that an increase in thermal radiation and heat transfer raises the temperature of the fluid. Furthermore, the fluid concentration is reduced due to the increased level of a chemical reaction.

Combined FEM and DIC Techniques for the 2D Analysis of the Stress-Strain Fields and Hydrogen Diffusion Near a Blunt Crack Tip

Combined FEM and DIC Techniques for the 2D Analysis of the Stress-Strain Fields and Hydrogen Diffusion Near a Blunt Crack Tip

Review of Composite Pressure Cylinders used in different Vehicles

Abstract: Natural gas is an eco-friendly source of energy due to its wide availability and safety during operation. It is a viable solution for current environment threat of pollution; however the transportation problem due to low density restricted its wide usage. Burst pressure prediction helps to estimate the load carrying capacity of vessel and prediction of burst pressure in different working condition is cumbersome work. Finite element method and continuum damage mechanics study used to study burst pressure. FEM techniques various model used to predict stress and burst pressure in academic scenario. Keywords: CNG cylinder, Composite, Burst Pressure, FEM, Vehicles