Generation Of Finite Element Models Research Articles

Influence of pelvic shape on strain patterns: A computational analysis using finite element mesh morphing techniques

The pelvis functions to transmit upper body loads to the lower limbs and is critical in human locomotion. Semi-automated, finite element (FE) morphing techniques eliminate the need for segmentation and have shown to accelerate the generation of multiple specimen-specific pelvic FE models to enable the study of pelvic mechanical behaviour. The purpose of this research was to produce simulated human pelvic FE models representing android, gynecoid, anthropoid and platypelloid morphologies and to isolate differences in strain patterns due to anatomic shape under physiologic loading. Using five initially generated specimen-specific FE models, each specimen-specific FE model was reconfigured into three different morphologies using FE mesh morphing techniques. Significantly different strains were found comparing the gynecoid (classical female pelvis’) to the android (‘true male pelvis’) models (p = 0.040), with strains twice as high in the superior pubic rami. No significant differences were seen in comparing overall strains between the other pelvic shapes (p = 0.61–0.126). The highest strain regions in all models were found in the supra-acetabular regions, with high strains also found in the regions of the superior pubic rami, the greater sciatic notch and sacral regions about the L5 vertebrae. Quantifying the contributions of shape to strain in the pelvis may increase the understanding of sex and patient-specific differences in fracture risk and motivate the consideration of treatment strategies that account for anatomic pelvic differences.

Design of RC joints equipped with hybrid trussed beams and friction dampers

The challenge of this research consists in the first attempt to apply a dissipative friction connection to beam-to-column joints with semi-prefabricated Hybrid Steel-Trussed Concrete Beams (HSTCB) and RC pillars cast in-situ. Nowadays, HSTCBs are widely adopted in civil and industrial buildings and, therefore, it is required to evaluate their compliance with the capacity design criteria and their seismic energy dissipation capability. However, the design of the reinforcement of such beams usually lead to the adoption of large amount of steel within the panel zone which becomes potentially vulnerable to the effects of seismic cyclic actions and dramatically reduce the dissipation capacity of the entire structure. Therefore, the introduction of friction dampers in the HSTCB-to-column joints is investigated in order to evaluate the ability of the device in preventing the main structural elements from damage and limiting the cracking of the panel zone, thanks to the increase of the bending moment lever arm, which reduces the shear forces in the joint. Moreover, the proposed solution thoroughly investigates the connection between the friction device and the beam in order to ensure adequate strength and stiffness to the connection. The feasibility study is firstly conducted through the development of design criteria for the pre-dimensioning of the device and, successively, the proposed solution is validated through the generation of finite element models.

Constitutive Numerical Model of FRCM Strips Under Traction

In this paper the tensile behavior of Fiber Reinforced Cementitious Matrix (FRCM) strips is investigated through Finite Element (FE) models. The most adopted numerical modeling approaches for the simulation of the fiber-matrix interface law are described. Among them, the cohesive model is then used for the generation of FE models which are able to simulate the response under traction of FRCM strips tested in laboratory whose results are available in the technical literature. Tests on basalt, PBO and carbon coated FRCM specimens are taken into account also considering different mechanical ratios of the textile reinforcement. The comparison between FE results and experimental data allows validating the adopted numerical modelling approach. Finally, some considerations are provided on the effects of the fiber fabric mechanical ratio and the strength and stiffness of the interface on the tensile capacity of the FRCM strip.

Set-based parametric modeling, buckling and ultimate strength estimation of stiffened ship structures

There have been a great demand for a suitable and convenient method in the field of buckling analysis of stiffened ship structures, which is essential to structural safety assessment and is significantly time-consuming. Modeling, buckling behaviors and ultimate strength prediction of stiffened panels were investigated. The modeling specification including nonlinear finite element model and imperfections generation, and post-buckling analysis procedure of stiffened plates were demonstrated. And a software tool using set-based finite element method was developed and executed in the MSC. Marc environment. Different types of stiffen panels of marine structures have been employed to investigate the buckling behavior and assess the validity in the estimation of ultimate strength. A comparison between results of the generally accepted methods, experiments and the software tool developed was demonstrated. It is shown that the software tool can predict the ultimate capacity of stiffened panels with imperfections with a good accuracy.

Local–global mode interaction in thin-walled inelastic rectangular hollow section struts part 2: Assessment of existing design guidance and new recommendations

Abstract The second part of the study on the local–global mode interaction in thin-walled inelastic rectangular hollow section struts focuses on design guidance. Based on the validated finite element (FE) model from the companion paper, a framework for fully automating FE model generation, submission and post-processing for geometric and material nonlinear analysis with imperfections is first presented. The ultimate load data for specimens with different cross-section aspect ratios, cross-sectional slenderness, global slenderness and welding options are generated. The current design rules for thin-walled welded RHS struts are assessed using the numerical results and existing experimental results from the literature by means of structural reliability analysis in accordance with the methodology presented in Annex D of Eurocode EN1990. A modified Direct Strength Method (DSM) relationship is then proposed and it is demonstrated to provide superior ultimate load predictions than the current guidelines.

Nanocellulose reinforced polymer composites: Computational analysis of structure-mechanical properties relationships

Structure-mechanical properties relationships of nanocellulose reinforced polymer composites are studied in computational experiments. A code for the generation of 3D unit cell finite element models of nanocellulose reinforced polymers with “snake”-shaped nanocellulose fibrils is developed. The code allows the generation of pre-defined nanocomposites structures, with varied angles between nanocellulose snakes segments and hydrogen bonds between nanocellulose fibrils. In a series of computational studies, it is demonstrated that the nanocellulose reinforcement leads to higher stiffness of the matrix polymer, but makes it more brittle.

Interaktivni algoritam za geometrijsko modeliranje dvojno zakrivljenih brana

A rapid and efficient algorithm for interactive geometric modelling of arch dams is presented. It combines the advantages of the traditional geometricdesign with innovative computational capabilities offering simple procedures for otherwise complex process of laying out double-curvature arch dam-reservoir coupled systems. The key parameters taken into account are: terrain topography, shape and thickness of crown cantilever, reference cylinder, thickness and curvature of individual arches, excavation depth, concrete volume, vertical and peripheral construction joints and automatic generation of finite element and boundary element models. The proposed algorithm was implemented in and runs parallel to the ADAD-IZIIS FEM-BEM, a finite element-boundary element software for structural analyses of concrete arch dams. To demonstrate the performances of the proposed algorithm, an example of a 130m high double-curvature arch dam was considered in a narrow V-shape canyon. The number of graphical options available at the push of a button, such as vertical and horizontal cross sections and 3D perspectives, allows the user to rapidly conduct the dam design within the optimization process.

Development and evaluation of a new methodology for the fast generation of patient-specific Finite Element models of the buttock for sitting-acquired deep tissue injury prevention

The occurrence and management of Pressure Ulcers remain a major issue for patients with reduced mobility and neurosensory loss despite significant improvement in the prevention methods. These injuries are caused by biological cascades leading from a given mechanical loading state in tissues to irreversible tissue damage. Estimating the internal mechanical conditions within loaded soft tissues has the potential of improving the management and prevention of PU. Several Finite Element models of the buttock have therefore been proposed based on either MRI or CT-Scan data. However, because of the limited availability of MRI or CT-Scan systems and of the long segmentation time, all studies in the literature include the data of only one individual. Yet the inter-individual variability can’t be overlooked when dealing with patient specific estimation of internal tissue loading. As an alternative, this contribution focuses on the combined use of low-dose biplanar X-ray images, B-mode ultrasound images and optical scanner acquisitions in a non-weight-bearing sitting posture for the fast generation of patient-specific FE models of the buttock. Model calibration was performed based on Ischial Tuberosity sagging. Model evaluation was performed by comparing the simulated contact pressure with experimental observations on a population of 6 healthy subjects. Analysis of the models confirmed the high inter-individual variability of soft tissue response (maximum Green Lagrange shear strains of 213 ± 101% in the muscle). This methodology opens the way for investigating inter-individual factors influencing the soft tissue response during sitting and for providing tools to assess PU risk.

Point clouds turned into finite elements: the umbrella vault of Castel Masegra

The paper presents a workflow for finite element model generation from point clouds acquired via photogrammetry and laser scanning. The case study is a room with an umbrella vault in Castel Masegra, located in Sondrio (Italy). The complexity of the room required an accurate geometric survey from a set of dense point clouds, from which a detailed BIM as well as 2D drawings were generated. Finally, a tetrahedral mesh was derived from the geometric model and was used to run a finite element analysis. The aim of this work is to describe the procedure developed and illustrate the main challenges found.

Subject specific finite element mesh generation of the pelvis from biplanar x-ray images: application to 120 clinical cases

Several Finite Element (FE) models of the pelvis have been developed to comprehensively assess the onset of pathologies and for clinical and industrial applications. However, because of the difficulties associated with the creation of subject-specific FE mesh from CT scan and MR images, most of the existing models rely on the data of one given individual. Moreover, although several fast and robust methods have been developed for automatically generating tetrahedral meshes of arbitrary geometries, hexahedral meshes are still preferred today because of their distinct advantages but their generation remains an open challenge. Recently, approaches have been proposed for fast 3D reconstruction of bones based on X-ray imaging. In this study, we adapted such an approach for the fast and automatic generation of all-hexahedral subject-specific FE models of the pelvis based on the elastic registration of a generic mesh to the subject-specific target in conjunction with element regularity and quality correction. The technique was successfully tested on a database of 120 3D reconstructions of pelvises from biplanar X-ray images. For each patient, a full hexahedral subject-specific FE mesh was generated with an accurate surface representation.

Análisis modal y dinámico de una pasarela peatonal en servicio

Civil engineering constructions like pedestrian footbridges are structures increasingly slender, ambitious and complex in which the dynamic effects caused by the loads to which they are subjected (pedestrians) may induce service problems and / or significant or repetitive amplifications of the efforts and deformations. This fact together with the current social demands related to the perception and comfort raise the need to integrate the analysis and computer-aided design in the evaluation of the vibrations generated by the loads this type of structures supports. In the specific case of finite element commercial programs, their use has not proliferated as much as in other engineering fields due to the existence of simplified methodologies in numerous national and international guidelines and regulations and the difficulty of making realistic models in the case of complex structures. However, the knowledge generated by the analysis of this type of numerical models would be especially useful in the earlier phases of the design of similar structures, so much initial as of the necessary modifications to solve existing dynamic problems, since it is in these stages when the best solution could be applied from both a technical and an economic point of view. This article describes the process of generation and updating of the mechanical finite element model (FEM) of a footbridge in service and the simulation of two types of load: an excitation generated by a shaker and a pedestrian load, contrasting the results generated by the numerical model with those obtained experimentally.

Analysis of pelvic strain in different gait configurations in a validated cohort of computed tomography based finite element models

The pelvis functions to transmit upper body loads to the lower limbs and is critical in human locomotion. Semi-automated, landmark-based finite element (FE) morphing and mapping techniques eliminate the need for segmentation and have shown to accelerate the generation of multiple specimen-specific pelvic FE models to enable the study of pelvic mechanical behaviour. The purpose of this research was to produce an experimentally validated cohort of specimen-specific FE models of the human pelvis and to use this cohort to analyze pelvic strain patterns during gait. Using an initially segmented specimen-specific pelvic FE model asa source model, four more specimen-specific pelvic FE models were generated from target clinical CT scans using landmark-based morphing and mapping techniques. FE strains from the five models were compared to the experimental strains obtained from cadaveric testing via linear regression analysis, (R2 values ranging from 0.70 to 0.93). Inter-specimen variability in FE strain distributions was seen among the five specimen-specific pelvic FE models. The validated cohort of specimen-specific pelvic FE models was utilized to examine pelvic strains at different phases of the gait cycle. Each validated specimen-specific FE model was reconfigured into gait cycle phases representing heel-strike/heel-off and midstance/midswing. No significant difference was found in the double-leg stance and heel-strike/heel-off models (p=0.40). A trend was observed between double-leg stance and midstance/midswing models (p=0.07), and a significant difference was found between heel-strike/heel-off models and midstance/midswing models (p=0.02). Significant differences were also found in comparing right vs. left models (heel-strike/heel-off p=0.14, midstance/midswing p=0.04).

Modeling of CPACS-based fuselage structures using Python

PurposeThe purpose of this paper is to present some of the key achievements. At DLR, a sophisticated interdisciplinary aircraft design process is being developed, using the CPACS data format (Nagel et al., 2012; Scherer and Kohlgrüber, 2016) as a means of exchanging results. Within this process, TRAFUMO (Scherer et al., 2013) (transport aircraft fuselage model), built on ANSYS and the Python programming language, is the current tool for automatic generation and subsequent sizing of global finite element fuselage models. Recently, much effort has gone into improving the tool performance and opening up the modeling chain to further finite element solvers.Design/methodology/approachMuch functionality has been shifted from specific routines in ANSYS to Python, including the automatic creation of global finite element models based on geometric and structural data from CPACS and the conversion of models between different finite element codes. Furthermore, a new method for modeling and interrogating geometries from CPACS using B-spline surfaces has been introduced.FindingsSeveral new modules have been implemented independently with a well-defined central data format in place for storing and exchanging information, resulting in a highly extensible framework for working with finite element data. The new geometry description proves to be highly efficient while also improving the geometric accuracy.Practical implicationsThe newly implemented modules provide the groundwork for a new all-Python model generation chain, which is more flexible at significantly improved runtimes. With the analysis being part of a larger multidisciplinary design optimization process, this enables exploration of much larger design spaces within a given timeframe.Originality/valueIn the presented paper, key features of the newly developed model generation chain are introduced. They enable the quick generation of global finite element models from CPACS for arbitrary solvers for the first time.

Concept Calculation Tool for Dynamics of Generator Set Common Baseframe

The Natural frequency and vibration response calculation process of a generator set was automatized so that it can be used in a generator set common base frame concept design. The implementation of automatization was to be done so that no profound knowledge about the finite element method is needed to execute calculations and that computation times are short. Substructuring is used for certain parts of the generator set model to reduce the computation times for more a efficient concept design process. The common base frame concept design is implemented to the process by using a design tool in which the finite element model generation from parametric geometry is automatized. Generator set finite element model generation, natural frequency and vibration response calculations and post-processing of analysis results were implemented by developing a calculation tool for this purpose. The calculation tool is an independent application that uses Abaqus simulation software to execute analyses.

Agricultural aircraft wing slat tolerance for bird strike

PurposeThe aim of this study is to assess and describe possible consequences of a bird strike on a Polish-designed PZL-106 Kruk agricultural aircraft. Due to its susceptibility to such events, a wing slat has been chosen for analysis.Design/methodology/approachSmooth particle hydrodynamics (SPH) formulation has been used for generation of the bird finite element model. The simulations were performed by the LS-Dyna explicit finite element analysis software. Several test cases have been analysed with differing parameters such as impact velocity, initial velocity vector direction, place of impact and bird mass.FindingsResults of this study reveal that the structure remains safe after an impact at the velocity of 25 m/s. The influence of bird mass on slat damage is clearly observable when the impact velocity rises to 60 m/s. Another important finding was that in each case where the part did not withstand the applied load, it was the lug where first failure occurred. Some of the analysed cases indicated the possibility a consequent wing box damage.Practical implicationsThis finding provides the manufacturer an important insight into the behaviour of the slat and suggests that more detailed analysis of the current lug design might improve the safety of the structure.Originality/valueEven though similar analyses have been performed, they tended to focus on large transport aircraft components. This investigation will enhance our understanding of structural response of small, low-speed aircraft to a bird impact, which is a realistic scenario for the chosen case of an agricultural plane.

The development of a computational tool for generation of high quality FE models of pipelines with corrosion defects

Corrosion is one of the most common causes of accidents involving pipelines. Unfortunately, the semi-empirical methods currently available are overly conservative for the assessment of some types of corrosion defects in pipelines. Fortunately, the computational simulations through finite element (FE) method are a very efficient and reliable approach to quantify the remaining strength of corroded pipes. However, the process of computational modeling demands intense manual labor from the engineer, and it is also slow and extremely repetitive, especially in cases of multiple defects. The main purpose of this work was to describe an original methodology for the automatic generation of FE models of pipes with corrosion defects (single or multiple). The model discretization uses semi-structured mesh and specific mesh transitions, which demanded even more manual labor. Also, the computational modeling process needs to be robust and efficient to ensure accuracy without excessive number of degrees of freedom. Thus, the tool allows the pre-configuration of mesh transitions and other parameters related to the mesh refinement. This program, called PIPEFLAW, is built-in as a software extension into the MSC.PATRAN commercial software and is written with Patran Command Language. The PIPEFLAW program has a friendly graphical user interface, which allows the user to provide the main parameters of the pipe and defect (or a series of defects), considering several different configurations and geometries. This paper is focused on the automatic generation of 3D FE models of pipelines with a single or a colony of idealized defects with rectangular or elliptical shapes. As result, some examples of FE pipe models with defects generated automatically by the program are shown and some element shape tests were performed to evaluate the final mesh quality of the FE pipe model. The methodology is validated through the comparison of the internal failure pressure of a pipeline with two rectangular defects, obtained using experimental burst test, manually generated FE models, semi-empirical methods and PIPEFLAW generated model. The developed tools lead to a reduction in the modeling procedure in the case presented from 2 weeks, using non-automatic standard procedure normally used in the industry, to 1 min.

Comparison of different bushing applications in composite structures of the aerospace industry

Abstract In this study, four different bushing applications of carbon-epoxy pre-preg laminated composite plates were investigated experimentally and theoretically. The bushings in composite specimens on which the applications were conducted were loaded perpendicular to their plane, and the strength of the assembly was investigated in this way. These applications were compared by using the results of the experiments. The methodology of bushing application was determined for the most durable assembly. The generated finite element model for different bushing assemblies provided contribution for designing process in finite element analysis. While MSC/PATRAN was used for the finite element model generation, MSC/NASTRAN was applied for the finite element analysis.

Research on Finite Element Model Generating Method of General Gear Based on Parametric Modelling

Aiming at the problems of low efficiency and poor quality of gear meshing in the current mainstream finite element software, through the establishment of universal gear three-dimensional model, and explore the rules of unit and node arrangement. In this paper, a finite element model generation method of universal gear based on parameterization is proposed. Visual Basic program is used to realize the finite element meshing, give the material properties, and set the boundary / load conditions and other pre-processing work. The dynamic meshing analysis of the gears is carried out with the method proposed in this pape, and compared with the calculated values to verify the correctness of the method. The method greatly shortens the workload of gear finite element pre-processing, improves the quality of gear mesh, and provides a new idea for the FEM pre-processing.

Automatic CT-based finite element model generation for temperature-based death time estimation: feasibility study and sensitivity analysis.

Temperature-based death time estimation is based either on simple phenomenological models of corpse cooling or on detailed physical heat transfer models. The latter are much more complex but allow a higher accuracy of death time estimation, as in principle, all relevant cooling mechanisms can be taken into account.Here, a complete workflow for finite element-based cooling simulation is presented. The following steps are demonstrated on a CT phantom: Computer tomography (CT) scan Segmentation of the CT images for thermodynamically relevant features of individual geometries and compilation in a geometric computer-aided design (CAD) model Conversion of the segmentation result into a finite element (FE) simulation model Computation of the model cooling curve(MOD) Calculation of the cooling time(CTE) For the first time in FE-based cooling time estimation, the steps from the CT image over segmentation to FE model generation are performed semi-automatically. The cooling time calculation results are compared to cooling measurements performed on the phantoms under controlled conditions. In this context, the method is validated using a CT phantom. Some of the phantoms' thermodynamic material parameters had to be determined via independent experiments.Moreover, the impact of geometry and material parameter uncertainties on the estimated cooling time is investigated by a sensitivity analysis.

RESULTS OF TESTING AND ASSESSMENT OF THE POSSIBILITY OF BUILDING A SYSTEM OF SPECIALIZED SOLUTIONS FOR STRENGTH ANALYSISBASED ON CAE FIDESYS

The possibility of constructing a system of specialized solutions for strength analysis based on CAE Fidesys is considered. The results of testing CAE Fidesys are presented. The finite element method and the spectral element method implemented in CAE Fidesys are discussed for the problems of mechanics of a deformable solid. The opinion is expressed that at this stage of the development of CAE Fidesys it can be used as an alternative CAE for carrying out control calculations, especially when solving non-typical tasks, in the solution of which there is a need to modify and adjust the main computational algorithms incorporated in the software. As a part of CAE Fidesys all the necessary elements are provided to ensure the effectiveness of its application - a preprocessor that provides the generation of finite element models, a modular processor for solving linear and nonlinear static and dynamic problems, buckling problems, estimation effective properties of composite materials, contact problems, postprocessor for visualization and processing of results. The results of testing CAE Fidesys are presented in comparison with the results obtained in ANSYS. The main purpose of the testing was to evaluate the possibilities of CAE Fidesys in terms of: importing geometry from CAD systems; the effectiveness of finite element mesh generator; determination of the stressstrain state of assemblies with a variable contact zone; solving dynamic problems, including modal and harmonic analysis. Testing of CAE Fidesys was performed on test cases representing the problems which are frequently faced in practical work. It is noted that the distinctive feature of CAE Fidesуs is the highorder spectral elements allowing one, in some cases, increase the accuracy of calculation without rebuilding the finite element mesh. It is noted that a comparative analysis of the calculations done on the models with similar finite element meshes conducted in CAE Fidesуs and ANSYS shows good coincidence of the results. The conclusion is that CAE Fidesуs can be used for solving different problems of structural analysis in addition to another CAE software available on the enterprise, and also taking into account the practical needs of active users, it can be considered, when combined with the user’s requirements, as the basis of an industrial solution for a structural analysis.