Conventional Finite Element Model Research Articles

Investigation on cutting deformation behavior of Al/SiCp composites considering particle feature distributions

Al/SiCp composite machining is considerably difficult owing to the presence of abrasive particles that results in weak synergetic deformation capacity during cutting. Therefore, to enhance the machinability of Al/SiCp composites, investigations on the cutting deformation behavior are imperative through finite element simulation. Aiming to address the limitations of conventional finite element models in accurately representing the actual microstructure of Al/SiCp composites, this study proposes a realistic microstructure-based finite element model to investigate the cutting deformation and damage behavior. The microstructural characteristics of the composites namely, particle feature distributions, including size distribution, aspect ratio distribution, and spatial aggregation of SiC particles, are analyzed and extracted based on the microstructure image of composite and the Gaussian stochastic model. Then, the particle feature distributions are incorporated into the microstructure-based model for the first time. Besides, all the failure mechanisms (i.e., the brittle fracture of SiC particles, the elastoplastic damage of Al matrix, as well as the particle-matrix decohesion) and the tool-chip contact behavior are comprehensively integrated into the modeling. The experimental results show that as the particle volume fraction and size increase, the chip radius and the number of chip curls decrease, the chips vary from little waviness to prominent saw-tooth type, and more particles are broken or debonded. According to the comparison with experimental results, the finite element model can effectively capture the deformation and failure process, as well as the characteristics of chip morphology, cutting force, and machined surface quality. In addition, the comparisons further demonstrate that SiC particles with large size, slender shape, and aggregation are prone to fracture and detachment in the cutting deformation. Finally, the influences of the particle feature distributions on the machinability of Al/SiCp composites are discussed in detail. It is found that decreasing the dispersion degree of particle size and aspect ratio distribution as well as minimizing the degree of particle clustering degree benefit the machinability of Al/SiCp composites.

FDEM analysis of deep rock mass failure and its impact on horizontal bearing capacity in offshore wind turbine piles

Rock-socketed single piles are integral components of offshore wind turbine foundations in rock-based sea areas. Traditional numerical models have been employed to analyze the failure modes and lateral interactions between piles and the rock medium. However, these do not simulate the decline in the horizontal bearing capacity due to rock breakage, posing potential safety risks. In this study, the combined finite-discrete element method (FDEM) was used to simulate the deformation process of submarine rock masses transitioning from an intact to a fractured state. A notable innovation in the proposed approach is the consideration of the effects of the rock mass fracture and pile-rock cohesion on the load-bearing behavior of single-pile foundations. The FDEM model was validated through full-scale lateral load tests. The results showed a distinctive sequence in failure mechanisms, with the tensile failure of the rock mass around the pile at significant depths preceding the compression failure. Local failure at the contact interface significantly reduced the horizontal bearing capacity—a phenomenon that is inadequately represented by conventional finite element models. Furthermore, the cohesion element embedding method was introduced and used to simulate the influence of the tensile properties inherent in grouting materials on the failure strength and mode of the pile-rock interface. This study highlighted the importance of considering the nuanced effects of rock failure in the design of horizontally loaded piles. Failure to do so could lead to nonconservative designs and compromise the safety and efficacy of offshore wind turbine foundations. By pushing the boundaries of numerical modeling with the FDEM, the study aims to provide a more accurate and reliable framework for the design and assessment of rock-socketed single piles for offshore wind energy applications.

Vibration based single-objective finite element model updating using cooperative game theory approach

This paper introduces a novel approach that focuses on application of cooperative game theory model for automated finite element model updating. The approach involves transforming the conventional single-objective optimization finite element model updating problem into a game theory problem. Among the different alternatives, a cooperative game model is considered to solve the transformed updating problem. This new approach overcomes the limitations of the conventional single-objective optimization formulation, which include challenges related to selecting appropriate weighting factor of residuals and analysing their influence on optimization results. To demonstrate the effectiveness of the proposed approach, an ultralight fibre reinforced polymer footbridge is considered. The numerical model of the footbridge is updated using the experimentally determined inherent properties (natural frequencies and mode shapes) using the proposed approach. A comparison with the conventional sensitivity-based weighted single objective method reveals that the inclusion of the weighting factor in the optimization process under the cooperative game model method allows for more efficient solution of the single-objective updating optimization problem, while maintaining accuracy and quality in the updated model.

Integrated computational modeling of large format additive manufacturing: Developing a digital twin for material extrusion with carbon fiber-reinforced acrylonitrile butadiene styrene

Material extrusion (MEX) continues to be a pivotal additive manufacturing (AM) process, involving the selective heating and layer-by-layer deposition of material. However, conventional finite-element models (finite-element analysis) face limitations in accurately simulating the MEX process, highlighting the need for experimental validation. This paper highlights an advanced material modeling technology that streamlines the development of composite parts using large format AM (LFAM). It specifically focuses on a thermoplastic acrylonitrile butadiene styrene (ABS) matrix composite material enriched with 20% short carbon fibers. The study employs integrated computational materials engineering, integrating (i) the manufacturing process, (ii) the material’s microstructure, (iii) homogenization techniques, and (iv) the performance of the final part. The development of a digital twin for pellet extrusion is proposed, emphasizing the importance of micro-structure characterization to account for warpage and residual stresses that lead to part distortion. The demonstrator manufactured for this study is a wind turbine mold of a blade section. Experimental tests revealed an elastic modulus of 5.5 GPa and a hardening modulus of 2.4 GPa for the composite. The numerical microscopic model showed a 16% error in the elastic modulus compared to experimental results. The study concludes that the homogenization techniques are effective in predicting the elastic properties but lack accuracy in the plastic region. The application of the model to the LFAM process of pellet extrusion is demonstrated, with simulation results showing a maximum deformation close to the center of the wind turbine blade mold.

Non-linear vibration of free spanning subsea pipelines with multi-dimensional mid-plane stretching

In the absence of full-length support, subsea pipelines can experience significant oscillations due to flow induced vortex shedding that may result in the accumulation of fatigue damage over time. Such oscillations reflect the intricate interplay between the structural characteristics of the pipeline and the unsteady flow field, which can generate periodic shedding of vortices and pulsating forces. Conventional finite element models and/or empirical relations (e.g. codes of practice) are usually sufficient to predict the frequencies and modeshapes of vibrating free-spanning pipelines, which facilitates the assessment of their fatigue damage. However, the effects of multi-dimensional mid-plane stretching (i.e. coupled non-linear deformations) on the stability and performance of pipelines are still unknown. Here, we formulate the governing equations of free spanning pipelines experiencing lateral and transversal non-linear deformation that apply to in-line and cross-flow vortex induced vibration (VIV), investigate the effect of lateral mid-plane stretching on the response of the structure when it is partially supported by seabed shoulders and constrained by uneven natural supports or buckle initiators, and demonstrate that transversal mid-plane stretching transforms the pipeline into a non-linear oscillator with hardening stiffness and single well potential energy (i.e. energy potential resembling a well-shaped curve).We found that lateral mid-plane stretching reduces the overall deflection of a free spanning pipeline, increases the frequency of vibration for various axial forces and seabed/support stiffnesses, and reduces the effective length at various seabed stiffnesses and axial forces. In addition, considering the transversal mid-plane stretching and solving the problem using Galerkin’s method showed that the frequency of resonance increases with the amplitude of vibration and the increase is a function of damping and non-linear stiffness. Our results prove that beyond a critical level of forced oscillation, the pipeline experiences a period doubling bifurcation, which has been overlooked in existing predictive tools and codes of practice.

Thermal Crosstalk Analysis of Phase Change Memory Considering Thermoelectric Effect and Thermal Boundary Resistance

Phase change memory (PCM) has emerged as a promising memory for next-generation applications due to its high-speed read and write capabilities as well as non-volatility. However, as PCM scales down to smaller feature sizes, it faces the challenge of thermal crosstalk. During the reset operation, a large amount of heat is generated and dissipated in the PCM array, potentially affecting adjacent memory cells, compromising device stability, and limiting high-density integration. To accurately investigate the thermal crosstalk in the PCM array, the conventional finite element model of the PCM array is improved by incorporating the thermoelectric effect and thermal boundary resistance. Under the 65, 45, 32, and 22-nm process nodes, the improved model reveals the occurrence of thermal crosstalk within the PCM array, whereas the conventional model is unable to detect this phenomenon at the 65-nm node. The improved model proposed in this paper incorporates more comprehensive considerations, providing a more precise analysis of the thermal crosstalk phenomenon in the PCM array, and thereby offering theoretical reference for high-density integration of the PCM.

Finite element analysis and experimental verification of residual stress in brazed diamond with Ni-Cr filler alloy

Residual stress is the main factor affecting the processing performance and service life of brazed diamond tools. Due to the high melting point of Ni-Cr filler alloy, the difference in thermal expansion coefficient between diamond and brazing layer is large during high brazing temperature, and excessive residual stress tends to be generated at the brazed joint. The existing process parameters are difficult to meet the demand for the lower residual stress under high brazing temperature. Suppressing effectively excessive residual stress has become the focus of current researches for process optimization of brazed diamond. In this paper, the conventional spherical finite element model of diamond is replaced by a six-octahedral finite element model of diamond, and a 3D finite element model of brazed diamond is established. The effects of brazing temperature, brazing layer thickness and holding time on the residual stresses in brazed diamond are analyzed. The results show that higher brazing temperatures result in larger differences in thermal expansion coefficients between the diamond and brazing layer, resulting in larger residual stress. The higher brazing layer thickness will enlarge the stress affected area inside diamond and thus generate higher stress. The residual stress decreases with rising holding time, however, the subsequent thermal damage to the diamond increases. Experimental measured tendency of residual stress for brazed diamond through Raman spectroscopy is well consistent with that of calculated results. After observing of the surface morphology for brazed diamond through super-depth of field microscope, the brazed diamond presents the low residual stress, weak graphitization and excellent processing performance at the condition of brazing temperature of 1010 °C, brazing layer thickness of 0.3 mm and holding time of 5 min.

Numerical modelling of shear cutting using particle methods

The use of Advanced High Strength Steel (AHSS) allows for lightweighting of sheet steel components, with maintained structural integrity of the part. However, AHSS grades show limitations in edge crack resistance, primarily influenced by sheared edge damage introduced by the shear cutting process. Numerical modelling of the shear cutting process can aid the understanding of the sheared edge damage, thus avoiding unforeseen edge cracking in the subsequent cold forming. However, the extreme deformations of the blank during the shear cutting process are likely to cause numerical instabilities and divergence using conventional Finite Element modelling. To overcome these challenges, this work presents the use of a particle-based numerical modelling method called the Particle Finite Element Method (PFEM). PFEM accurately solves some of the challenges encountered in shear cutting with the standard Finite Element method, such as large deformation, angular distortions, generation of new boundaries and presents an efficient way of transfer historical information from the old to the new mesh, minimising the results diffusion. The present work shows prediction of cut edge morphology of AHSS using a PFEM modelling scheme, where the numerical results are verified against experiments. With these results, the authors show new possibilities to obtain accurate numerical prediction of the shear cutting process, which promotes further advances in prediction of edge damaged related to shear cutting of AHSS.

Modelling of Creep Rupture in Grade 92 Steel Using a Microstructure-Type Finite Element Mesh

Conventional finite element (FE) modelling, which employed structured mesh, is unable to simulate local damage evolution at microstructure level. This paper aims to investigate the creep rupture and damage behaviour of Grade 92 steel under a creep environment using microstructural-type FE mesh. The idealised microstructures of the material were generated based on the Voronoi tessellation technique. Three notched bar specimens with different notch acuities were modelled in Abaqus v6.13 software and a ductility exhaustion based damage model was employed to estimate the damage state. The influence of the notch constraint on the ductility is accounted for in the simulation. It is found that the results obtained from the proposed technique are in good agreement with the experimental data. All the prediction points fall within the scatter band of +/- factor of 2. The damage was predicted to initiate at a distance offset from the notch tip. As the acuity increases, the damage initiation site shifts further away from the notch.

Structural performance assessment of RC flexural members through crack-based fibre beam-column model updating

For reinforced concrete (RC) structures in service, original finite element models (FEMs) based on design information usually deviate from actual structures due to structural damage such as cracks, displacement and material degradation. Although conventional FEMs can be updated to give results that match the response data used during the updating process, they can hardly predict the subsequent structural performance. In this study, an innovative fibre beam-column model updating method based on static deflection and crack width is proposed. First, the self-developed fibre beam-column finite element program COMPONA-MARC is modified to efficiently simulate the nonlinear cracking behaviour of RC flexural members. Second, sensitivity studies using the discrete central difference method based on the Lagrange interpolation function are conducted to select updating parameters. Third, with the combination of modified COMPONA-MARC and an automation program written in Python, plenty of sample data are obtained, and artificial neural networks (ANNs) are trained by Bayesian Regularization Backpropagation (BRB). Finally, the updated parameters are acquired by inputting the measured static deflections and crack widths. Typical RC beams and RC slabs from the literature are utilized to validate the proposed methodology and explore potential implementation scenarios. The results show that updated FEMs can satisfactorily predict mechanical behaviour and assess structural performance. The proposed method offers enlightening insights about combining structural health monitoring and inspection (SHMI) results with model updating, which can promote the applications of digital twins in performance assessments of RC structures.

Structural finite element model updating considering soil-structure interaction using ls-dyna in loop

In this study, a finite element model updating method which can consider soil-structure interaction was developed to analyze the effect of soil properties on the structural response while considering interaction between the soil and the structure. Additionally, LS-DYNA, a commercial finite element program, was included in the loop of the proposed technique using MATLAB to conveniently utilize the complex structures updated by the model. To validate the performance of the proposed method, a large-scale shake table test was conducted. The objective of the validation test was to seek how accurately the proposed model updating method can detect the change in the stiffness. To compare the result of the proposed method with the conventional method, the model updating procedure was conducted with and without considering soil-structure interaction. The proposed finite element model updating method which considers the soil-structure interaction estimated the stiffness of the structure with maximum accuracy of 91%, while the conventional finite element model updating without considering the soil-structure interaction showed maximum accuracy of 88%. By comparing the proposed method with the conventional method without considering the soil-structure interaction, it was confirmed that the proposed method had an 3% higher accuracy on average.

Steel shear behaviour on bearing strength and failure modes of single-bolt connections

This paper presents an experimental and numerical study to investigate the bearing strength and failure modes of single-bolt connections. A total of 24 single-bolt connection specimens with the end and edge distances ranging from 1.0d0 to 3.0d0 were tested. The tensile and shear regions are proposed and defined as the corresponding part of steel plates based on the experimental observations, and it is verified by finite element (FE) model. Then a FE modelling method considering tensile and shear material properties on the corresponding regions is proposed to explore the bearing behaviour of single-bolt connections. Besides, fracture criterion is incorporated into FE models to investigate the relationship between the bearing strength and failure mode of the bolted connections. The bearing strength exceeding 12% overestimation and incorrect failure mode would be obtained using the conventional FE modelling method for bolted connections under shear dominated stress due to steel shear behaviour. For single-bolt connections subjected to different stress states, the proposed method can accurately predict the whole process behaviour of the connection involving the bearing strength, fracture deformation and failure modes. Furthermore, FE and theoretical models are used to reveal the fracture mechanism of bolted connections. The bearing strength obtained based on Teh model shows a better agreement with experimental results within 7% error, and the failure modes of single-bolt connections can be accurately predicted by Teh model and ASIC specification.

Enabling Part-Scale Scanwise process simulation for predicting melt pool variation in LPBF by combining GPU-based Matrix-free FEM and adaptive Remeshing

• A highly efficient GPU-based matrix-free finite element modeling with adaptive remeshing framework is developed to overcome the high computational expense of l -PBF thermal process modeling, making it feasible to do detailed scanwise thermal simulation for part-scale within days. • The effects of the scanning strategy, geometrical features, and proximity to the turning points on the melt pool size variability and lack of fusion porosity are investigated for two different parts. • The predicted variation in melt pool size and lack of fusion porosity has good correlation with experimental measurements. This work proposes to combine matrix-free finite element modeling (FEM), adaptive remeshing, and graphical processing unit (GPU) computing to enable, for the first time, scanwise process simulation of the Laser Powder Bed Fusion (L-PBF) process with temperature-dependent thermophysical properties at the part scale. Compared to the conventional FEM using the global stiffness approach and a uniform mesh running on 10 CPU cores, l -PBF process simulation based on the proposed methodology running on a GPU card with 5,120 Compute Unified Device Architecture (CUDA) cores enables a speedup of over 10,000x. This significant speedup facilitates detailed thermal history and melt pool geometry predictions at high resolution for centimeter-scale parts within days of computation time. Two parts consisting of various geometric features are simulated to reveal the effects of scan strategy and local geometry on melt pool size variation, which correlate well with melt pool and lack-of-fusion porosity measurements obtained via experiment.

Research on the Dynamic Characteristics of the CFETR Vacuum Vessel Based on the Modal Synthesis Method

The vacuum vessel is the core component of the Chinese Fusion Engineering Testing Reactor (CFETR); its main function is to remove nuclear heating, provide safety shielding, and maintain a high-quality vacuum environment. Therefore, the safety of the vacuum vessel is of great significance to the CFETR, and examining its dynamic performance is necessary. However, the conventional finite element method takes too long to perform the dynamic analysis of the vacuum vessel, which greatly reduces the efficiency of the design and analysis. Based on the modal synthesis method, this study uses ANSYS software to establish a substructure model of the CFETR vacuum vessel. A modal analysis and harmonic response analysis are conducted, and their results are compared with those of the conventional finite element model. The results show that the substructure model not only has the same accuracy as conventional finite element models, but that it also greatly reduces the time of dynamic calculation.

Model updating-based dynamic collapse analysis of a RC cable-stayed bridge under earthquakes

This study proposes a general framework for progressive seismic collapse analysis of reinforced concrete (RC) bridges and it begins with an introduction of the progressive seismic collapse framework, which is mainly composed of five procedures. Subsequently, a 1:12 scale RC cable-stayed bridge together with the measurement system are presented, and the bridge model is subjected to a series of shake table tests. A conventional nonlinear finite element (FE) model, representing the undamaged condition of the cable-stayed bridge, is established, and the FE model is then nonlinearly updated based on the measured data from the measurement system when the bridge model is under small and moderate shake table excitations. The reliability of the updating process is validated through comparisons against another independent group of the measured data during the same moderate excitation. A more destructive ground motion is finally applied to the damaged FE model, where the progressive seismic collapse responses are obtained. The simulated seismic collapse responses based on the nonlinearly updated FE model give a good agreement with the measured data from the shake table tests employing the same destructive excitation, indicating that the model updating strategy proposed in this paper is efficient and reliable.

Effect of pneumatic rubber fenders on the prevention of structural damage during collisions between a ship-shaped offshore installation and a shuttle tanker working side-by-side

ABSTRACT This study investigated the effects of pneumatic fenders on the prevention of structural damage from collisions between a ship-shaped offshore installation and a shuttle tanker during side-by-side offloading operations. A nonlinear finite element modelling technique was developed to simulate the kinetic energy absorption behaviour of pneumatic fenders during collisions. Full-scale pneumatic fenders were physically tested to validate the computational model at various collision speeds. The developed pneumatic fender model was integrated with a conventional finite element model of a hull structure to simulate the crashworthiness of the hull structure in collisions with a shuttle tanker during side-by-side offloading. This integrated computational model was then applied to examine case studies involving a VLCC class ship-shaped offshore installation hull with and without pneumatic rubber fenders colliding with a Suezmax class shuttle tanker. The key findings and insights of these investigations, particularly the collision energy absorption characteristics are summarised.

An Accuracy Comparison of Micromechanics Models of Particulate Composites against Microstructure-Free Finite Element Modeling.

Micromechanics models of composite materials are preferred in the analysis and design of composites for their high computational efficiency. However, the accuracy of the micromechanics models varies widely, depending on the volume fraction of inclusions and the contrast of phase properties, which have not been thoroughly studied, primarily due to the lack of complete and representative experimental data. The recently developed microstructure-free finite element modeling (MF-FEM) is based on the fact that, for a particulate-reinforced composite, if the characteristic size of the inclusions is much smaller than the composite representative volume element (RVE), the elastic properties of the RVE are independent of inclusion shape and size. MF-FEM has a number of advantages over the conventional microstructure-based finite element modeling. MF-FEM predictions have good to excellent agreement with the reported experiment results. In this study, predictions produced by MF-FEM are used in replace of experimental data to compare the accuracy of selected micromechanics models of particulate composites. The results indicate that, only if both the contrasts in phase Young’s moduli and phase Poisson’s ratios are small, the micromechanics models are able to produce accurate predictions. In other cases, they are more or less inaccurate. This study may serve as a guide for the appropriate use of the micromechanics models.

Progressive failure analysis of open-hole composite laminates using FLWT-SCB prediction model

This paper presents the original incorporation of the smeared crack band (SCB) damage model within the full layerwise theory (FLWT) framework, to contribute to the increase of the computational efficiency of the progressive failure analysis of open-hole laminar composites loaded in tension, simultaneously preserving the accuracy of the conventional 3D finite element models. The developed FLWT-SCB prediction model was implemented into an original FLWTFEM framework allowing for the accurate 3D stress fields and excellent visualisation capacity. The response of damaged lamina, in both fiber and matrix directions, was described by distinct bilinear strain-softening curves. The mesh dependency problem was minimized by scaling the fracture energy using a characteristic element length.Both the failure initiation and failure modes were determined using the Hashin failure criterion. To verify the model effectiveness, the obtained results were compared against the experimental and benchmark data from the literature. Mesh dependency was analysed to confirm the benefits of suggested model, as well. The obtained results agreed with the experimental ones and those from the literature.According to the numerical results, FLWT-SCB allows for coarser meshes than those used in the standard finite element models, leading to improved computational efficiency without compromising the accuracy. The model also demonstrated the weak dependency between the size of the structure and the mesh. The advantages of using FLWT-SCB damage model in achieving significant improvements in computational efficiency are highlighted.

The Uncertainty Propagation for Carbon Atomic Interactions in Graphene under Resonant Vibration Based on Stochastic Finite Element Model.

Graphene is one of the most promising two-dimensional nanomaterials with broad applications in many fields. However, the variations and fluctuations in the material and geometrical properties are challenging issues that require more concern. In order to quantify uncertainty and analyze the impacts of uncertainty, a stochastic finite element model (SFEM) is proposed to propagate uncertainty for carbon atomic interactions under resonant vibration. Compared with the conventional truss or beam finite element models, both carbon atoms and carbon covalent bonds are considered by introducing plane elements. In addition, the determined values of the material and geometrical parameters are expanded into the related interval ranges with uniform probability density distributions. Based on the SFEM, the uncertainty propagation is performed by the Monte Carlo stochastic sampling process, and the resonant frequencies of graphene are provided by finite element computation. Furthermore, the correlation coefficients of characteristic parameters are computed based on the database of SFEM. The vibration modes of graphene with the extreme geometrical values are also provided and analyzed. According to the computed results, the minimum and maximum values of the first resonant frequency are 0.2131 and 16.894 THz, respectively, and the variance is 2.5899 THz. The proposed SFEM is an effective method to propagate uncertainty and analyze the impacts of uncertainty in the carbon atomic interactions of graphene. The work in this paper provides an important supplement to the atomic interaction modeling in nanomaterials.

Modelling dynamic interaction of maglev train–controller–rail–bridge system by vector mechanics

The dynamic coupling interaction of maglev train–controller–rail–bridge (TCRB) system has the potential to induce instability of travelling maglev trains. The conventional contact-type finite element model (FEM) method is difficult in modelling the TCRB system in the presence of non-contact levitation between the maglev vehicle and guideway and in incorporating the time-variant mechanism of suspension controllers in a high-dimensional FEM. In this study, we develop a new method, which endeavours to overcome the above difficulties, for modelling the maglev TCRB system and its dynamic interaction in the context of vector mechanics (VM). The VM underlies the principles on formulating vector form intrinsic finite elements (VFIFEs) to solve problems such as large deformation, large displacement, structural discontinuity, and non-contact mechanisms. In the VM formulation, we model the vehicle bodies, suspension bogies, and electromagnets as a collection of mass particles rigidly connected or linked by spring–dashpot units, with the levitation forces between the F-type rail and electromagnets being commanded by feedback controllers. Meanwhile, the guideway, including rail and bridge, is modelled as a group of mass particles linked by VFIFEs. The equations of motion for each mass particle are solved individually without need of assembling a global stiffness matrix, thereby eliminating the problems of ill-conditioning and numerical divergence. The proposed modelling method is validated by comparing the measured vehicle and bridge responses from a full-scale maglev train during its running on a test line with the computed results by the proposed method. After validation, the vertical and pitching resonant characteristics of the maglev system and the condition to invoke levitation gap resonance are evaluated.