Survey of Finite Element Method-Based Real-Time Simulations

The finite element method (FEM) has deservedly gained the reputation of the most powerful, highly efficient, and versatile numerical method in the field of structural analysis. Though typical application of FE programs implies the so-called “off-line” computations, the rapid pace of hardware development over the past couple of decades was the major impetus for numerous researchers to consider the possibility of real-time simulation based on FE models. Limitations of available hardware components in various phases of developments demanded remarkable innovativeness in the quest for suitable solutions to the challenge. Different approaches have been proposed depending on the demands of the specific field of application. Though it is still a relatively young field of work in global terms, an immense amount of work has already been done calling for a representative survey. This paper aims to provide such a survey, which of course cannot be exhaustive

Application of the Craig-Bampton model order reduction method to a composite structure: MACco, COMAC, COMAC-S and eCOMAC

The Craig-Bampton model order reduction (CBMOR) method based on the Rayleigh-Ritz approach was applied in a previous work to simulate dynamic behavior of a composite structure (CFRP) using the modal assurance criteria (MAC) and cross orthogonality (XOR) to validate the correlation. Different coordinate modal assurance criteria are applied to complement and verify the eigenfrequencies and eigenvectors obtained of the full and reduced models using substructures (super-elements). An improvement is observed per paired mode-sensor with the MAC per coordinates criterion (MACco) in a CFRP once the stiffness parameters are updated in the full model applying a mix-numerical experimental technique (MNET) using a design of experiments (DOE). The coordinate modal assurance criteria (COMAC) and the scaleCOMAC (COMACS) results of the full models display the best results respect to the reduced model. Furthermore, slight improvement of the enhanced COMAC (eCOMAC) results are observed in the reduced model despite having lower MAC performance. This approach complements the results of the previous work using several COMAC techniques, and demostrates the feasibility to achieve low COMACs results in the reduced finite element model once the stiffness parameters of the full element model are updated. The example was prepared and solved with MSC/NASTRAN SOL103 and SDTools-MATLAB for comparative purposes

KE-formulacija za aplikacije virtualne stvarnosti

Virtual reality (VR), as a novel technology, represents one of the most powerful tools to assist or even play the major role in many areas, such as development of new designs, training medical practitioners or assembly operators, entertaining industry, etc. On the other hand, the finite element method (FEM) imposed itself as an essential technical support for the needs of computing flexible bodies’ deformational behavior. FEM together with CAD are important ingredients of VR. In the VR applications that imply interactive simulations with flexible bodies included, the efficiency of FEM formulations is of crucial importance. The paper presents a co-rotational FEM-formulation developed to meet the needs of simulating geometrically nonlinear deformational behavior at interactive frame rates. It is presented here in combination with a rather simple linear tetrahedral element. The formulation is enriched with a coupled-mesh technique to enable the usage of rougher FEM models to compute deformational behavior of complex geometries. The advantages of an iterative solver and the solution procedure for both static and dynamic analyses are discussed.Virtualna stvarnost (VR), kao nova tehnologija, predstavlja jednu od najmoćnijih alatki koje podržavaju rad ili čak igraju glavnu ulogu u mnogim područjima, kao što su razvoj novih dizajna, trening liječnika ili montažera, industrija zabave, itd. S druge strane, metoda konačnih elemenata (MKE) se nametnula kao osnovna tehnička podrška za potrebe proračunavanja deformacijskog ponašanja elastičnih tijela. MKE je zajedno s CAD-om, važan dio VR-a. U VR aplikacijama koje podrazumijevaju interaktivnu simulaciju s elastičnim tijelima, efikasnost MKE formulacije je od presudne važnosti. Rad predstavlja korotacijsku MKE formulaciju razvijenu s ciljem simuliranja geometrijski nelinearnog ponašanja u interaktivnoj domeni. Formulacija je predstavljena u kombinaciji s vrlo jednostavnim linearnim elementom tipa tetraedra. Formulacija je proširena tehnikom spregnutih mreža kako bi se omogućilo korištenje grubljih MKE modela za određivanje deformacijskog ponašanja složenih geometrija. Razmotrene su prednosti iterativnog solvera kao i procedura rješavanja statičke i dinamičke analize

Highly efficient fe simulations by means of simplified corotational formulation

Finite Element Method (FEM) has deservedly gained the reputation of the most powerful numerical method in the field of structural analysis. It offers tools to perform various kinds of simulations in this field, ranging from static linear to nonlinear dynamic analyses. In recent years, a particular challenge is development of FE formulations that enable highly efficient simulations, aiming at real-time dynamic simulations as a final objective while keeping high simulation fidelity such as nonlinear effects. The authors of this paper propose a simplified corotational FE formulation as a possible solution to this challenge. The basic idea is to keep the linear behavior of each element in the FE assemblage, but to extract the rigid-body motion on the element level and include it in the formulation to cover geometric nonlinearities. This paper elaborates the idea and demonstrates it on static cases with three different finite element types. The objective is to check the achievable accuracy based on such a simplified geometrically nonlinear FE formulation. In the considered examples, the difference between the results obtained with the present formulation and those by rigorous formulations is less than 3% although fairly large deformations are induced

THE ANALYSIS OF FEM RESULTS CONVERGENCE IN MODELLING PIEZOELECTRIC ACTIVE SHELL STRUCTURES

The field of active/adaptive structures has been the subject of intense interest over the past couple of decades. The progress in this research field strongly depends on the availability of adequate and reliable modelling tools. Regarding structural analysis in general, the finite element method (FEM) has imposed itself as the method of choice for modelling and simulation. Piezoelectric active structures are characterized by strong enough coupling between the mechanical field and the electric field, which is further used for the realization of active structural behaviour. The descriptions of the mechanical and electrical field as well as their coupling significantly affect the convergence of the FEM results with mesh refinement, which may proceed in a trend different to what is commonly expected when FEM is applied to purely mechanical problems. The paper considers this aspect by using two quadratic shell type finite elements developed for modelling piezoelectric composite laminates. Both full and uniformly reduced integration techniques are taken into consideration in a set of examples involving composite laminates with active piezoelectric layers

THE ANALYSIS OF FEM RESULTS CONVERGENCE IN MODELLING PIEZOELECTRIC ACTIVE SHELL STRUCTURES

The field of active/adaptive structures has been the subject of intense interest over the past couple of decades. The progress in this research field strongly depends on the availability of adequate and reliable modelling tools. Regarding structural analysis in general, the finite element method (FEM) has imposed itself as the method of choice for modelling and simulation. Piezoelectric active structures are characterized by strong enough coupling between the mechanical field and the electric field, which is further used for the realization of active structural behaviour. The descriptions of the mechanical and electrical field as well as their coupling significantly affect the convergence of the FEM results with mesh refinement, which may proceed in a trend different to what is commonly expected when FEM is applied to purely mechanical problems. The paper considers this aspect by using two quadratic shell type finite elements developed for modelling piezoelectric composite laminates. Both full and uniformly reduced integration techniques are taken into consideration in a set of examples involving composite laminates with active piezoelectric layers

Nachnutzbare FEM-Software in der DDR

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TCR signaling requirements for activating T cells and for generating memory

Over the last two decades the molecular and cellular mechanisms underlying T cell activation, expansion, differentiation, and memory formation have been intensively investigated. These studies revealed that the generation of memory T cells is critically impacted by a number of factors, including the magnitude of the inflammatory response and cytokine production, the type of dendritic cell [DC] that presents the pathogen derived antigen, their maturation status, and the concomitant provision of costimulation. Nevertheless, the primary stimulus leading to T cell activation is generated through the T cell receptor [TCR] following its engagement with a peptide MHC ligand [pMHC]. The purpose of this review is to highlight classical and recent findings on how antigen recognition, the degree of TCR stimulation, and intracellular signal transduction pathways impact the formation of effector and memory T cell

STRATEGI KOMUNIKASI PEMASARAN USAHA RINTISAN SERFASH

Sepanjang tahunnya, terjadi ketimpangan antara jumlah lapangan pekerjaan dengan jumlah lulusan perguruan tinggi di Indonesia. Ketimpangan ini mampu diatasi dengan memperbanyak lapangan pekerjaan, salah satunya dengan membangun usaha rintisan. Serfash merupakan salah satu usaha rintisan di bidang fashion thrift dengan garansi reparasi sepatu gratis yang pertama di Pulau Jawa. Sebagai usaha rintisan yang tergolong baru, Serfash masih perlu menerapkan berbagai strategi agar usaha berjalan dengan maksimal, salah satunya dengan menerapkan strategi komunikasi pemasaran. Maka dari itu, peneliti tertarik untuk melakukan penelitian terkait strategi komunikasi pemasaran pada usaha rintisan Serfash. Jenis penelitian ini merupakan jenis penelitian kualitatif. Metode penelitian menggunakan penelitian deskriptif-kualitatif dengan subjek penelitian adalah dua pihak internal usaha rintisan Serfash, yakni CEO Serfash dan COO Serfash. Objek penelitian ini ialah strategi komunikasi pemasaran usaha rintisan Serfash. Teknik pengumpulan data pada penelitian ialah dokumentasi dan wawancara mendalam. Teknik analisis data dilakukan dengan 3 tahapan, diantaranya: reduksi data, penyajian data, hingga penarikan kesimpulan dan verifikasi. Hasil dari penelitian mengungkapkan bahwa strategi komunikasi terbagi atas perumusan strategi, implementasi strategi, dan evaluasi strategi. Berdasarkan hasil temuan dan analisis data, didapatkan kesimpulan bahwa strategi komunikasi pemasaran pada Serfash didapatkan dengan menyusun strategi Serfash melalui design thinking dengan didukung dengan konsep-konsep pendukung seperti IMC yang berproses atau berjalan secara bersamaan atau bersinergi dengan BMC. Proses pada IMC diharapkan dapat bekerja secara terintegrasi maksimal, namun pada kenyataanya ada beberapa poin yang tidak dapat bekerja secara bersamaan seperi bagian media marketing akan bekerja terlebih dahulu sebelum bagian publik relasi dapat bekerja secara maksimal. Selain itu, Serfash menitik beratkan segmen pada mahasiswa atau masyarakat menengah ke bawah dengan dengan kriteria trend terbaru. Dari poin diatas disimpulkan bahwa Serfash menggunakan komunikasi pemasaran dengan optimal dimana branding citra Serfash menggunakan elemen hard selling berupa garansi reparasi sepatu dan gratis cuci sepatu dan dengan menggunakan iklan, promosi, dan seasonal event digunakan sebagai bentuk strategi komunikasi pemasaran yang digunakan Serfash

MODAL TRIGGERED NONLINEARITIES FOR DAMAGE LOCALIZATION IN THIN WALLED FRC STRUCTURES – A NUMERICAL STUDY

This paper presents a novel method for detecting locations of damages in thin walled structural components made of fiber reinforced composites (FRC). Therefore, the change of harmonic distortion, which is found by current research to be very sensitive to delamination, under resonant excitation will be derived from FEM-simulation. Based on the linear modal description of the undamaged structure and the damage-induced nonlinearities represented by a nonlinear measure, two spatial damage indexes have been formulated.The main advantage of this novel approach is that the information about the defect is represented mainly by changes in the modal harmonic distortion (MHD), which just needs to be measured in one (or few) structural points. The spatial resolution is given by the pairwise coupling of the MHD with the corresponding mode shapes