Finite Elements in Analysis and Design最新文献

The Cyclic Interface Shear Test (CIST) device was recently developed to evaluate the response of soil–structure interfaces subjected to monotonic or cyclic loading. Numerical models of the CIST have not been documented. Such simulations may be beneficial to help guide the design of experiments, interpret results, and inform the development of further experimental device modifications. In the present paper, a series of interface shear tests utilizing the CIST system on a cohesive soil under monotonic loadings were simulated using a proposed three-dimensional model in the commercial finite element analysis software ABAQUS/Standard. Comparisons of simulations with experimental results are presented for the Mohr–Coulomb and hypoplasticity models for cohesive soils. It is found that (i) the clay-based hypoplasticity model outperformed the simpler Mohr–Coulomb model in terms of predicting the interface shear stress evolution and the soil volume change and (ii) the clay-based hypoplasticity model allows for identification of trends in shear response as a function of normal confining pressures at the soil–structure interface (e.g. soil–structure interface shear zone thickness). Neither of these capabilities have previously been documented or experimentally validated for cohesive soil–structure interface simulations using clay-based hypoplasticity models.

A multiscale computational framework to capture stress concentrations and localized nonlinearity in composite structures is presented. An enriched approximation space, constructed using the generalized finite element method (GFEM), is used to incorporate nonlinear, heterogeneous material behavior into coarse-scale models on the fly. Enrichment functions are constructed using the GFEM with global–local enrichment functions (GFEM${}^{gl}$). The auxiliary local problems associated with the GFEM${}^{gl}$ also define fine-scale constitutive behavior that is inherited by the coarse global problem. This allows a coarse homogenized global problem to learn about material heterogeneity and/or nonlinearity on the fly, considerably increasing the flexibility of the method. On top of the explicit definition of heterogeneity in local problems, the locally defined constitutive law can incorporate further levels of heterogeneity that are not explicitly modeled at the global scale. The proposed GFEM${}^{gl}$ comes with the efficiency and scalability characteristic of the method and greatly increases the flexibility when applied to heterogeneous structures with localized material nonlinearity.

This paper deals with a 3D linear formulation for mono-symmetric composite beams with deformable connection, taking into account non-uniform torsion. To simplify the development of the analytical solution, it is assumed that the warping of each layer of the composite section has no contribution on the stress resultants of each layer. Therefore, the warping function obtained with the classical St-Venant beam theory can be used for each subsection. As a result, the variables associated to both connection shearing plans become uncoupled. Using the virtual work principle, the governing equations are derived, and solved in closed-form. Based on the analytical expressions of the displacement fields, the exact stiffness matrix of the composite beam is computed. In addition, a displacement-based formulation is suggested. Appropriate polynomial interpolation functions are selected to circumvent slip-locking phenomenon. It has been shown that the slip-locking can be avoided by using quadratic shape function for axial displacement interpolations, by providing an additional middle node in each layer. Four examples are investigated in this paper. The prediction as well as the performance of the proposed direct stiffness method, are compared against an existing solution from the literature. In addition, slip-locking problem is addressed and the performance of the displacement-based method against the exact formulation is evaluated. The influence of warping effects on the composite beam response is assessed. Finally, a parametric study is conducted to evaluate the influence of connection rigidity and the coupling of the displacement fields on slip distributions.

A 2D axisymmetric finite element multiphysics model is proposed to study magnetoelectric composite disks. This modeling approach includes a nonlinear magneto-elastic model to replicate the behavior of magnetostrictive materials under static conditions. Additionally, it offers a harmonic regime resolution that considers frequency dependence, including the implicit inclusion of eddy currents in the formulation, as well as electrical load. To validate the model, simulation results regarding the dependence of the static magnetic field and frequency are presented and compared with experimental measurements from literature.

This work studies the solid-shell finite element approach to approximate thin structures using a stabilized mixed displacement–stress formulation based on the Variational Multiscale framework. The work is divided in two parts. In Part I, the numerical locking effects inherent to the solid-shell approach are characterized using a variety of benchmark problems in the infinitesimal strain approximation. In Part II, the results are extended to formulate the mixed approach in finite strain hyperelastic problems. In the present work, the stabilized mixed displacement–stress formulation is proven to be adequate to deal with all kinds of numerical locking. Additionally, a more comprehensive analysis of each individual type of numerical locking, how it is triggered and how it is overcome is also provided. The numerical locking usually occurs when parasitic strains overtake the system of equations through specific components of the stress tensor. To properly analyze them, the direction of each component of the stress tensor has been defined with respect to the shell directors. Therefore, it becomes necessary to formulate the solid-shell problem in curvilinear coordinates, allowing to give mechanical meaning to the stress components (shear, twisting, membrane and thickness stresses) independently of the global frame of reference. The conditions in which numerical locking is triggered as well as the stress tensor component responsible of correcting the locking behavior have been identified individually by characterizing the numerical response of a set of different benchmark problems.

This study aims to optimize topology of structures at macro and micro scales, simultaneously, by using a level set method in an isogeometric analysis (IGA) framework. To achieve this, equilibrium and homogenization equations in the model are solved by IGA method. The level set functions are defined over a grid in parameter space of associating b-splines of the IGA model. Therefore, control net of the model and level set grid are separated and there is no need to refine the control net for having smooth boundaries. Sensitivity analyses for both scales are performed to calculate the velocity of boundary points and the level set functions are updated by solving reaction-diffusion equations. Finally, several 2D and 3D examples with different geometry and boundary conditions are provided to show performance and efficiency of the method. Obtained results show good agreement with examples in literature in terms of both topology and final value of objective function. Also, by using IGA level set method, smooth boundaries are achieved in the final topology of micro and macro structures.

A novel topology optimization method for the design of coated structures infilled with multiple materials is proposed in this paper, where a novel material interpolation model for the topology description is developed based on the ordered SIMP scheme. With the introduction of two special Heaviside projections into the two-step filtering and projection procedure, the external coating and the substrate region can be well identified by using several modified design variables. Then, the material distribution of the multi-material infilling is obtained by multiplying the infill identification field with the piece-wisely projected design variables and optimized via the mathematical programming algorithm under the ordered SIMP framework. Using an eroded density field and its original field, the uniform thickness of the external coating can be well controlled. The proposed approach for optimizing coated structures with multi-phase infill materials is easy to implement due to its implementation relying on those frequently-used filtering and projection operations. Besides, without introducing any additional design variables, the method developed in this paper inherits the advantages of the ordered SIMP method and has great calculation efficiency and stable iteration performance. With the consideration of several issues such as different coating thicknesses and different design parameters, several 2D numerical examples are studied to demonstrate the effectiveness of the proposed approach, as well as a 3D example. The optimization results illustrate that the method developed in this paper is effective for the design of coated structures infilled with multiple materials and the advantages of considering multiple infill materials is also validated.

Polymeric materials find extensive applications across various engineering sectors. Among these, a particularly critical application for these materials is in the field of roller coasters. The wheels are typically made with an aluminum hub and a dense polyurethane coating, which, being in contact with the track, endures dynamic loads at high speeds. Due to the viscoelastic behavior typical of polymeric materials, these loads induce overheating of the coating leading to rapid degradation of the wheel. This results in machine downtime and a significant waste of time and money. In this manuscript, a methodology for finite element thermal-structural analysis has been developed. This method allows for the rapid evaluation of temperatures reached during operational cycles if compared to classical coupled-field thermal-structural analysis. The proposed methodology proves to be useful in selecting the appropriate type of wheels during the design phase requiring short computational time. The study first involved the development of the methodology, followed by validation through a comparison of analysis results with data obtained from experimental tests conducted by the manufacturer.

This study presents a combination approach of the higher-order shear deformation theory, nonlocal strain gradient theory (NSGT) and isogeometric analysis (IGA) for the free vibration of carbon nanotube-reinforced (CNT) magneto-electro-elastic (MEE) nanoplates. To account size-dependent effects at the nanoscale, the classical theory model is extended with two additional scale parameters. However, this extended model necessitates at least the third derivative of the approximation function, which is incompatible with the standard finite element method. So, IGA with NURBS offers higher-order continuity through its basis functions, making it well-suited for this size-dependent model. To simplify computations, a power-law scheme is employed to represent the material properties. Various distribution types of carbon nanotubes (CNTs) including UD, FG-X, FG-O and FG-V are incorporated to investigate their effects on mechanical behaviors of CNT-MEE nanoplates. The governing equations of motion are derived in their weak form using the principle of extended virtual displacement and then solved by isogeometric analysis (IGA). The impact of the magnetic, electric and elastic fields on the coupling behaviors of CNT-MEE nanoplates are studied. Specially, parametric studies are conducted to analyze the influence of geometrical parameters, CNT distributions, CNT volume fraction, matrix volume fraction, electric voltage, magnetic potential, nonlocal and strain gradient parameters on the natural frequencies of the CNT-MEE nanoplates. Comparisons between the results obtained using NSGT and the classical theory reveal significant findings. The natural frequencies calculated by NSGT exhibit dependence on the relative values of the nonlocal and strain gradient parameters.

Numerical simulations in biomechanics, particularly in bone healing, present a cost-effective option compared to experiments that demand prolonged observations with human or with animal models. However, to define in-silico simulations of the bone healing process requires considering multiple factors, such as the implant design and patient’s characteristics. As a result, the current challenge is integrating different numerical methodologies to simulate bone healing, aiming to facilitate the emergence of innovative clinical treatments and new implant designs.

In this paper, we present a patient-specific numerical methodology to simulate the bone healing process, able to consider patient’s load conditions and bone density distribution provided by CT-scans. The main novelty is the combination of the Cartesian grid Finite Element Method (cgFEM) with a bone callus healing model, complemented by a load-condition optimisation scheme to relate implant materials and load conditions while ensuring successful healing outcome.

This numerical methodology creates a finite element model based on the patient’s medical image, serving as a virtual testing tool for investigating the influence of implant materials on gait pattern requirements to ensure an optimal healing outcome. In practice, a personalised bone fracture model was employed to evaluate four distinct implant materials: two conventional materials (stainless steel and titanium) and two bioabsorbable candidates (polylactic acid plastic (PLA) and magnesium). The results offer personalised optimal load conditions for each studied material, showcasing the potential of in-silico studies in minimising uncertainties associated with exploring new clinical treatments.