Finite Element-based Model Research Articles

Influences of printing parameters on mechanical properties of recycled PET and PETG using fused granular fabrication technique

This research presents an investigation of the feasibility of recycled polyethylene terephthalate (rPET) and glycol-modified polyethylene terephthalate (rPETG) thermoplastics using the fused granular fabrication (FGF) 3D printing technique. It focuses on the effects of FGF printing parameters on the mechanical properties of rPET and rPETG printed parts using a Gigabot X 3D printer. The design of experiments (DOE) was first performed considering the main FGF 3D printing parameters such as layer thickness, infill density and number of contours. The experimental studies were then carried out to study the effects of printing parameters on the tensile properties based on the DOE. The effect of interlayer bonding of printed parts on the tensile properties was also evaluated using finite element-based multiscale modelling. Scanning electron microscopy (SEM) and Fourier transformation infrared (FTIR) spectroscopy were used to observe the fracture morphology and chemical structure of post-FGF printing products. The tensile test results indicate that the highest tensile strength of 26.4 MPa was obtained for rPET when using a 1.1-mm layer thickness, a 70% infill density, and 3 contours, whereas, for rPETG, the maximum tensile strength of 44.8 MPa was attained with a 1.2-mm layer thickness, a 100% infill density, and 2 contours. FTIR analysis confirms no significant changes of characteristic peaks for PET in the printed products, suggesting that rPET and rPETG are viable materials for FGF printing. Thermal stability studies also reveal that the glass transition temperature and onset degradation temperatures are not significantly affected by the printing parameters. The study demonstrates the potential of rPET and rPETG as sustainable alternatives to virgin materials and provides insights into the optimal processing conditions for achieving high-quality 3D printed parts via the FGF technique.

A traction coefficient formula for EHL point contacts operating in the linear isothermal region

Many mechanical systems including rolling/sliding parts, require traction data across a spectrum of operating conditions to predict their motion effectively. Numerous studies have examined the thermal effects and shear-thinning concerning the traction curve, but only a few have focused on the traction coefficient in the linear isothermal regime for low SRR. In this work, we investigate traction coefficient characteristics of EHL point contacts in the linear isothermal regime, over a wide range of operational conditions. To this end, we conduct numerical simulations utilizing a fully-coupled finite element-based model, resulting in a prediction formula for the traction coefficient slope. With this formula, the traction coefficient slope could be predicted for the operating conditions considered.

Strain engineering of nonlinear nanoresonators from hardening to softening

Although strain engineering and soft-clamping techniques for attaining high Q-factors in nanoresonators have received much attention, their impact on nonlinear dynamics is not fully understood. In this study, we show that nonlinearity of high-Q Si3N4 nanomechanical string resonators can be substantially tuned by support design. Through careful engineering of support geometries, we control both stress and mechanical nonlinearities, effectively tuning nonlinear stiffness of two orders of magnitude. Our approach also allows control over the sign of the Duffing constant resulting in nonlinear softening of the mechanical mode that conventionally exhibits hardening behavior. We elucidate the influence of support design on the magnitude and trend of the nonlinearity using both analytical and finite element-based reduced-order models that validate our experimental findings. Our work provides evidence of the role of soft-clamping on the nonlinear dynamic response of nanoresonators, offering an alternative pathway for nullifying or enhancing nonlinearity in a reproducible and passive manner.

Experimental and Numerical Research on the Splitting Capacity of European Beech Beams Loaded Perpendicular to the Grain by Connections: Influence of Different Geometrical Parameters

In the present work, single- and double-dowel joints following different geometric configurations are experimentally and numerically investigated to derive the splitting behaviour of beech wood (Fagus sylvatica L.), one of the most widespread hardwood species in Europe for structural purposes. The influence of the spacing between dowels, their distance to the supports, and the slenderness of the beams is analysed. The correlation of the experimental failure loads with those predicted numerically by cohesive zone finite element-based models using the fracture properties of the species is discussed. The experimental results are also compared with those obtained from the normative expression included in Eurocode 5 and two other design models reported in the literature. The splitting failure loads predicted by both the analytical and numerical models were found to be conservative, the latter being closer to the experimental values.

Numerical Study of the Effect of Maturation and Extended Chloride Deposition on Chloride Ingress

This study presents the implementation of advanced analytical models designed to account for delayed exposure to chlorides in reinforced concrete structures. These models incorporate the effects of aging, which are known to reduce the rate of chloride ingress over time. The analytical models aim to provide faster predictions of the durability and service life of concrete structures subjected to chloride penetration comparing to finite element based models. To validate the accuracy and reliability of these models, preliminary results have been obtained and compared with those from a reference finite element-based model. The comparative analysis highlights the strengths and limitations of the analytical models, offering insights into their potential application in real-world scenarios. This research contributes to the field of structural engineering by enhancing predictive capabilities for infrastructure exposed to chloride-induced corrosion.

Comparison of novel ionic liquids and pure water for CO2 separation through membrane contactor: CFD simulation and thermal analysis

Industrial application of novel, green and effective liquid absorbents for improving the separation yield of CO2 greenhouse pollutant is an important milestone to reduce its emission to the atmosphere. In this research, the separation performance of three novel and green ionic liquids (ILs) including [bmim][PF6], [bmim][BF4] and [emim][etSO4] are compared with pure water to evaluate the feasibility of their employment to enhance the removal potency of CO2 through the membrane contactor. With the aim of reaching this goal, a finite element-based model and a numerical simulation are developed to solve the momentum/mass transfer equations and predict the results. Based on the modeling/simulation outcomes, the addition of the abovementioned ILs could substantially increase the separation of CO2 molecules compared to pure water. Based on the results, [bmim][BF4] is introduced as the most efficient IL with the separation efficiency of 100 % (100 % [bmim][BF4]> 99 % [bmim][PF6]> 97.5 % [emim][etSO4]> 55 % pure water). Furthermore, the effects of different operational/functional parameters (i.e., gas flow rate, porosity, fibers’ number and packing density) on the CO2 separation efficacy is comprehensively discussed.

Assessment of wellbore integrity failure risk and hazardous zones in depleted reservoirs underground gas storage during the operation processes.

Depleted reservoirs are widely used for underground gas storage due to their advantages of low construction cost and easy development. Under the influence of complex geological conditions and frequent operations, the integrity of the wells in depleted reservoirs is prone to failure, which would potentially lead to gas leakage. In this study, by using a finite element-based computational fluid dynamics model, we have developed evaluation criteria for assessing the severity of the occurred wellbore integrity failure and the risk of the un-occurred wellbore integrity failures respectively to identify hazardous zones potentially prone to wellbore integrity failure. The study results indicate that the gas storage wellbore integrity failure is prone to occur inside the wellbore structure in the direction of the minimum ground stress near the lower boundary of the formation interlayer. The wellbore integrity failure hazardous zones are mainly concentrated at the formation interlayer boundaries. The practical guidelines and solutions derived from current research results can provide an accurate direction for monitoring and protecting work of wellbore integrity and avoid environment pollution problems caused by natural gas leakage.

Modelling Microstructure in Casting of Steel via CALPHAD-Based ICME Approach

Integrated computational materials engineering (ICME) is emerging as an increasingly powerful approach to integrate computational materials science tools into a holistic system and address the multiscale modeling challenges in the processing of advanced steels. This work aims at incorporating macroscopic model (finite element-based thermal model) and microscopic model (CALPHAD-based microstructure model), building an industry-oriented computational tool (MICAST) for casting of steels. Two case studies were performed for solidification simulations of tool steel and stainless steel by using the CALPHAD approach (Thermo-Calc package and CALPHAD database). The predicted microsegregation results agree with the measured ones. In addition, two case studies were performed for continuous casting and ingot casting with selected steel grades, mold geometries and process conditions. The temperature distributions and histories in continuous casting and ingot casting process of steels were calculated using in-house finite-element code which is integrated in MICAST. The predicted temperature history from the casting process simulation was exported as input data for the DICTRA simulation of solidification. The resulting microsegregation by the DICTRA simulation can reflect the microstructure evolution in the real casting process. Current computational practice demonstrates that CALPHAD-based material models can be directly linked with casting process models to predict location-specific microstructures for smart material processing.

Static analysis of shear-deformable aircraft wings using a multilayered functionally graded material model

This study presents a comprehensive investigation of the static analysis of a shear-deformable aircraft wing made of functionally graded materials (FGMs). A finite element-based multilayered FGM model is employed for this purpose. In order to ensure the safe structural design of the aircraft wing, it is crucial to analyze the transverse displacement of the wing under various loading conditions. The presented model employs a power-law distribution based on the rule of mixture to derive the effective material properties of the FGM wing. The analysis focuses on three standard FGM aircraft wing profiles, namely NACA 0009, NACA 2424, and NACA 4415, which are representative of commonly used geometries in aircraft design. Additionally, the study explores the effects of volume fraction index, loading conditions, boundary conditions, and aspect ratio on the static analysis of the shear-deformable FGM aircraft wing. These parameters play a significant role in shaping the static behavior of the wings and offer valuable insights into the design of FGM aircraft wings.

Applications of Wireless Sensor Network for Displacement Monitoring in Opencast Coal Mine Slopes

Coal is the primary source of energy for the production of electricity as well as other industrial purposes. Despite being one of the largest coal producers in the world, India still imports coal to meet domestic demand. Coal is mainly extracted from opencast mines with high mechanization and deeper depths to meet the required coal demand. However, there are many problems with deeper opencast projects, like slope stability and its failure, which can be caused by slope geometry and rock properties. These failures result in equipment damage and human fatalities. It is necessary to monitor the stability of the slope to keep the working conditions safe. Traditional instrument techniques are currently deployed in opencast mines for regular slope monitoring. These traditional instruments usually rely on humans to collect and analyze data offline, which involves huge costs for manpower utilization. Moreover, it only works during daylight, and reliability is also not up to the mark. On the other hand, the latest instruments like Light Detection and Ranging (LiDAR) and Radio Detection and Ranging (RADAR) can efficiently monitor slope movements; those are more expensive and require highly skilled manpower. To eliminate this uncertainty and to obtain real-time data for studying the dynamic behavior of workings, Wireless Sensor Networks (WSN) are introduced. This study uses a node with a sensor and a receiver to collect data based on slope displacement measured in millimeters in a selected opencast mine. Data obtained using a WSN-based monitoring system was observed to be close to the existing total station monitoring method. ANSYS finite element-based numerical modeling software was used for simulating the field conditions and validated the results obtained by the WSN-based sensor's real-time monitoring and existing traditional field monitoring system.

Research on Dynamic Response of Pipeline under the Reeling Process and Laying Process

During the process of laying submarine pipelines using the R-lay (short for reel-lay) method, the interaction between the pipeline and the laying equipment undergoes continual fluctuations, leading to bending in the pipeline induced by the stochastic dynamics of various external loads. Considering the challenge in forecasting the dynamic behavior of pipeline bending moments and ovality throughout this procedure, we constructed a finite element-based shell element model for a 6-inch pipeline. In this paper, a multi-step simulation approach was used to replicate the pipeline laying process, and the dynamic response in pipeline bending moments and ovality during the winding, unwinding, and straightening processes was analyzed. Additionally, the effects of the pipeline’s diameter–thickness ratio and material properties on the dynamic response process were also studied. The results show that the dynamic response in bending moments and ovality is closely related to the curvature of the pipeline; a brief peak will appear at the critical point where the pipeline deforms, and the peak is related to the different bending stages of the pipeline, with the winding stage having a greater impact on the peak than the unwinding stage. During the unwinding process, a reverse bending moment will occur. The dynamic response of pipeline bending moments and ovality is influenced to some extent by the pipeline’s diameter–thickness ratio and material properties, with the diameter–thickness ratio demonstrating a more conspicuous impact.

Thermal creep and fatigue failure of the sintered silver solder in a SiC-IGBT module under power cycling

In this work, the creep samples of sintered silver were prepared by the chemical reduction method. According to the creep testing results, the Anand constitutive model was established to demonstrate the creep characteristics of sintered silver within a certain temperature range. According to the finite element electro-thermal–mechanical coupling analysis, the cyclic creep characteristics of sintered silver solder in the SiC-IGBT module under power cycling were simulated. The results shows that the sintering pressure and temperature can greatly promote the integrity of sintered silver by enhancing inert-particle bonding strength, and the established Anand model can effectively describe the creep behavior of sintered silver. The predicted results from electro-thermal–mechanical simulation were in good agreement with the power cycling testing results under the same condition. The finite element-based creep fatigue model is effective in predicting the creep fatigue life of sintered silver solders.

Towards an automated framework for the finite element computational modelling of directed energy deposition

In the present work, a comprehensive framework for finite element-based computational modelling of Directed Energy Deposition (DED) process is presented. The proposed approach can be fully automated and implemented on a complex real-life part geometry to accurately predict a thermo-mechanical response during the full-scale deposition process. The discrete material deposition modelling in Finite Element Analysis (FEA) leads to artificial increases in temperature gradients in the melt pool domain. A new method is therefore proposed that aims to mitigate these gradients. Additionally, an easy-to-implement free-surface detection algorithm to accurately prescribe the evolving heat transfer boundary conditions is presented. A three-dimensional sequentially coupled thermo-mechanical model of the process is then validated against experimental data obtained in a deposition case study. The simulation results show good agreement with the in-situ temperature measurements taken during the actual deposition. In addition, result analysis showed that the largest tensile residual stresses form in the hoop and axial direction on the outer domain of the thin-wall cylindrical part near the base plate while the inward material is compressed.

Multi-physics coupling simulation of small mobile nuclear reactor with finite element-based models

This paper describes the multi-physics coupling simulation of a small transportable nuclear reactor, SIMONS, using the neutronics/thermo-mechanics coupling three-dimensional high-fidelity code platform FEMAS (FEM-based Multiphysics Analysis Software for Nuclear Reactor). FEMAS builds multi-physics field models utilizing the open-source finite element codes deal.II and FEniCS. Using coupling simulations of neutronics, thermal-conduction, and thermo-mechanics, the SIMONS micro mobile reactor is examined. For the generation of cross-sections libraries, the open-source Monte Carlo code OpenMC is utilized, and the (n,xn) correction and SPH method is developed to maintain neutron equilibrium and eliminate homogenization errors. The approaches yield neutronic solutions that are in good agreement with the reference solutions, as the keff error decreases from 5066 pcm to 7.2 pcm and the maximum relative power error decreases from 5.2% to 0.3%. With a thermal power of 240 kW, the local temperature difference of the entire reactor is 354.68 K, and the deformation rate due to thermal stress is 2.4%, resulting in a reactivity feedback of 4459.6 pcm. At the wall in contact with the outermost fuel rods, where the temperature gradient grows substantially and thermal stress rises, the monolith stress is measured to peak at 9.65 MPa. This research has paved the way for a more thorough multi-physics examination of micro nuclear reactors in the era of high-precision computation.

Estimation of the dissipation due to radiation damping for the pile embedded in soil: A closed-form solution

In the present work, the overall energy dissipation of a pile embedded in the soil, modeled as visco-elastic springs, is thoroughly investigated. The term dissipation is used to measure the rate of decay of amplitude of displacement response in the time domain. The estimation of dissipation in piles is necessary to understand how quickly a pile reaches its steady state or equilibrium under dynamic loads or in cases of free vibration, respectively. A higher level of dissipation indicates a shorter duration of transient vibration, which is a deserving trait for vibration mitigation in extreme events, such as earthquakes, storms, blasts, shocks, etc. The dispersion relation which is a function of wavenumber and free wave frequency is obtained for the pile embedded in the soil medium by implementing the generalized form of Bloch’s theorem. The dispersion relationship is solved in the free-wave approach, in which a real wave number yields a set of complex frequencies. For predicting the overall dissipation of the system from the complex frequency values, an analytical closed-form expression is proposed in this paper. Further, the predicted dissipation is validated with a finite element-based numerical model of the soil–pile system.

Predicting localised corrosion and mechanical performance of a PEO surface modified rare earth magnesium alloy for implant use through in-silico modelling

In this study, the influence of a plasma electrolytic oxidation (PEO) surface treatment on a medical-grade WE43-based magnesium alloy is examined through an experimental and computational framework that considers the effects of localised corrosion features and mechanical properties throughout the corrosion process. First, a comprehensive in-vitro immersion study was performed on WE43-based tensile specimens with and without PEO surface modification, which included fully automated spatial reconstruction of the phenomenological features of corrosion through micro-CT scanning, followed by uniaxial tensile testing. Then the experimental data of both unmodified and PEO-modified groups were used to calibrate parameters of a finite element-based surface corrosion model. In-vitro, it was found that the WE43-PEO modified group had a significantly lower corrosion rate and maintained significantly higher mechanical properties than the unmodified. While corrosion rates were ∼50% lower in the WE43-PEO modified specimens, the local geometric features of corroding surfaces remained similar to the unmodified WE43 group, however evolving after almost the double amount of time. We were also able to quantitatively demonstrate that the PEO surface treatment on magnesium continued to protect samples from corrosion throughout the entire period tested, and not just in the early stages of corrosion. Using the results from the testing framework, the model parameters of the surface-based corrosion model were identified for both groups. This enabled, for the first time, in-silico prediction of the physical features of corrosion and the mechanical performance of both unmodified and PEO modified magnesium specimens. This simulation framework can enable future in-silico design and optimisation of bioabsorbable magnesium devices for load-bearing medical applications.

Numerical Study on the Various Profile Sections of Concrete Filled Steel Tubular Columns Under Compression

The axial load-carrying capacity for a wide range of short concrete-filled steel tubular (CFST) members having different section profiles is evaluated in the presented work. A numerical study has been carried out through Finite-Element based demonstration and it has been accomplished in the ABAQUS package for relevancy of analytically predicted axial load carrying capacity by unified formula as suggested by Yu M. et al. (2010). To validate the results from the unified formula and the experimentally available literature, finite element-based models for hollow and solid sections of CFST columns with circular, octagonal, and square section profiles have been generated. A total of 31 hollow and 24 solid circular columns, 9 hollow, and 9 solid octagonal columns, and in the last 9 hollows and 38 solid square CFST columns are examined for the persistence of the results. After evaluation of obtained results from the modeling existing results are validated, and it is found that the proposed unified formula predicts satisfactory results when compared with the result of established models. Further, it is concluded that displacement in the direction of applied load is not uniform throughout the length of CFST columns thereby using the ring confinement technique for the region of applied force may be reasonable.

Numerical analysis of hydrogen atom diffusion and trapping at an unconstrained dent on pipelines

In this work, a three-dimensional finite element-based mechanics-diffusion coupling model is developed to determine the stress/strain distribution and hydrogen (H) atom concentration at an unconstrained dent on an X52 steel pipe which is to be used for transport of high-pressure hydrogen gas. Both von Mises stress and equivalent plastic strain concentrations and a high hydrostatic stress gradient exist at the dent. The distribution of H atom concentration coincides with that of the hydrostatic stress. The maximum H atom concentration in the steel lattice locates at the dent bottom, while the distribution of the H atom concentration at metallurgical traps is consistent with that of the equivalent plastic strain. A competitive effect exists between the hydrostatic stress and the plastic strain on the H atom distribution. At low initial H atom concentrations (e.g., 0.001 mol/m3), the equivalent plastic strain dominates the distribution of H atoms. At high initial H atom concentrations (e.g., 0.1 and 1 mol/m3), the hydrostatic stress is more important to determine the distribution of H atom concentration. As the dent depth increases, both the von Mises stress and plastic strain at the dent increases, while the total H atom concentration decreases due to decreased hydrostatic stress. When the internal pressure increases from 5 MPa to 15 MPa, there are slightly increases in von Mises stress, equivalent plastic strain and the total H atom concentration.

Study by finite element modeling of hydrogen atom diffusion and distribution at a dent on existing pipelines for hydrogen transport

Pipelines, especially existing natural gas pipelines, provide an efficient and economical means for hydrogen transport, accelerating realization of a full-scale hydrogen economy. However, the existing aged pipelines usually contain dents, which serve as effective traps to accumulate hydrogen atoms, potentially causing hydrogen embrittlement and pipeline failures. To date, there has been a strong interest in development techniques for assessment of hydrogen atom distribution at a dent on pipelines. In this work, a three-dimensional nonlinear finite element-based model was developed to investigate the hydrogen atom diffusion and distribution at a constrained dent on an X52 steel pipe. Parametric effects, including dent depth and internal pressure, were determined. The presence of a dent on pipelines drastically changes the local stress and strain distributions, facilitating diffusion and accumulation of hydrogen atoms at the dent. The minimum hydrogen atom concentration at the crystalline lattice sites, (i.e., 3.8 mol/m3) is located on the outer surface of the dent center, and the maximum hydrogen atom concentration (i.e., 12.1 mol/m3) is found on both sides of the dent with 103 mm from the dent center in the circumferential direction. The hydrogen atom concentration at trap sites at the dent is much lower than that at the lattice sites. The diffusion and accumulation of hydrogen atoms at the dent area is affected by two competitive mechanisms, i.e., hydrostatic stress and plastic strain, depending on the initial concentration of hydrogen atoms entering the interior of the pipe steel. At a low initial concentration such as 0.001 mol/m3, the equivalent plastic strain dominates the distribution of hydrogen atoms at the dent, and the hydrogen atom concentration at the lattice sites is much lower than the concentration at the trap sites. At high initial hydrogen atom concentrations such as 0.1 and 1 mol/m3, the hydrostatic stress is the dominant factor to determine the distribution of hydrogen atoms, which mainly accumulate at the lattice sites. With an increased depth of the dent, both the von Mises stress and plastic strain concentrations increase, and so is the hydrogen atom concentration. The increase of internal pressure from 5 MPa to 15 MPa only slightly elevates the von Mises stress, equivalent plastic strain and the hydrogen atom concentration.

Evaluation of the Interface of Green Bilayer Powder Compact (BPC) of Iron (Fe) Under Different Die Wall Conditions

The current work evaluates cross-sectioned green bilayer powder compact (green BPC) of iron (Fe) under different die conditions. At first, finite element-based (FE) simultaneous compaction modelling is used to model the uniaxial, one-sided compaction of the green BPC of Fe and its interface. A Tri-mesh of 0.03 mm and mesh refinement along the interfacial boundary is set up with the condition of each node from both sides of layers (namely lower layer, L and upper layer, U) is mapped precisely to ensure its mutual interconnection along the horizontal edges of interface. Additionally, the modelling part utilised and validated our recently proposed image analysis under the metallographic technique’s standard framework. Our approach to model the interface to gain the same effect as from the experimental result of green BPC of Fe is in good agreement. It is significantly found that the use of the lubricated die condition contributed to increasing the local RD distribution along the interface of the green BPC of Fe. In contrast, the distribution is gradually dissuaded from the interface for the unlubricated die condition as the applied height: diameter (H:D) ratio increases.