scholarly journals Computational Finite Element Method (FEM) forward modeling workflow for transcranial Direct Current Stimulation (tDCS) current flow on MRI-derived head: Simpleware and COMSOL Multiphysics tutorial

2019 ◽  
Author(s):  
Ole Seibt ◽  
Dennis Truong ◽  
Niranjan Khadka ◽  
Yu Huang ◽  
Marom Bikson
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Computational Models ◽  
Current Flow ◽  
Forward Modeling ◽  
Fem Model ◽  
Direct Current Stimulation ◽  
Element Method

AbstractTranscranial Direct Current Stimulation (tDCS) dose designs are often based on computational Finite Element Method (FEM) forward modeling studies. These FEM models educate researchers about the resulting current flow (intensity and pattern) and so the resulting neurophysiological and behavioral changes based on tDCS dose (mA), resistivity of head tissues (e.g. skin, skull, CSF, brain), and head anatomy. Moreover, model support optimization of montage to target specific brain regions. Computational models are thus an ancillary tool used to inform the design, set-up and programming of tDCS devices, and investigate the role of parameters such as electrode assembly, current directionality, and polarity of tDCS in optimizing therapeutic interventions. Computational FEM modeling pipeline of tDCS initiates with segmentation of an exemplary magnetic resonance imaging (MRI) scan of a template head into multiple tissue compartments to develop a higher resolution (< 1 mm) MRI derived FEM model using Simpleware ScanIP. Next, electrode assembly (anode and cathode of variant dimension) is positioned over the brain target and meshed at different mesh densities. Finally, a volumetric mesh of the head with electrodes is imported in COMSOL and a quasistatic approximation (stead-state solution method) is implemented with boundary conditions such as inward normal current density (anode), ground (cathode), and electrically insulating remaining boundaries. A successfully solved FEM model is used to visualize the model prediction via different plots (streamlines, volume plot, arrow plot).

scholarly journals STUDI BANDING PERFORMA TIANG UTAMA BUS UNTUK MODEL TUNGGAL DAN MODEL GANDA DENGAN MENGGUNAKAN SIMULASI METODA ELEMEN HINGGA

2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Budi Setiyana
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fem Model ◽  
Element Method

Sehingga setiap komponen dari bus harus memiliki struktur rangka yang kuat terutama pada tiang utama. Masing-masing tiang utama umumnya dibuat dari sebuah baja profil tunggal (model tunggal). Tetapi tiang utama bus ini juga dapat dibuat dari gabungan dua buah baja profil dengan cara di las (model ganda) yang mempunyai dimensi luar yang sama dengan model tunggal. Penelitian ini bertujuan memodelkan dan membandingkan performa tiang utama sebuah bus untuk tiang model tunggal dan model ganda dengan menggunakan FEM (Finite Element Method). Hasil simulasi FEM adalah berupa tegangan dan displacement. Berdasarkan hasil analisis, didapatkan tegangan dan displacement pada tiang utama model tunggal yaitu berturut turut sebesar 1,287 x 106 N/m2 dan 6,448 x 10-1 mm. Sedangkan tegangan dan displacement pada tiang utama model ganda yaitu berturut turut sebesar 2,936 x 106 N/m2 dan 1,580 mm.  Dari hasil simulasi, bentuk rangka tiang utama yang terbaik adalah tiang utama model tunggal karena memiliki tingat keamanan yang tinggi dibandingkan dengan tiang model ganda baik dari sisi tegangan maupun displacement.Kata kunci: FEM, model tunggal, model ganda, tiang utama

scholarly journals Modelling of triaxial fracture processes in heterogeneous quasi-brittle materials using the Embedded Finite Element Method (E-FEM)

2021 ◽  
Author(s):  
Alejandro Ortega Laborin ◽  
Yann MALECOT ◽  
Emmanuel ROUBIN ◽  
Laurent DAUDEVILLE
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Spherical Inclusion ◽  
Brittle Materials ◽  
Three Dimensions ◽  
Strong Discontinuity ◽  
Homogeneous Material ◽  
Fem Model ◽  
Fracture Processes ◽  
Element Method

This paper studies the use of the Embedded Finite Element Method (E-FEM) for the numerical modelling of triaxial fracture processes in non-homogeneous quasi-brittle materials. The E-FEM framework used in this study combines two kinematics enhancements: a weak discontinuity allowing the model to account for material heterogeneities and a strong discontinuity allowing the model to represent local fractures. The strong discontinuity features enriched fracture kinematics that allow the modelling of all typical fracture modes in three dimensions. A brief review is done of past work using similar enriched finite element frameworks to approach this problem. The work continues by establishing the theoretical basis of each kind of discontinuity formulation and their superposition through the Hu-Washizu variational principle. Afterwards, two groups of simulations have been done for discussing the performance of this combined E-FEM model: homogeneous simulations and simple heterogeneous simulations. Simple homogeneous material simulations aim to test the capabilities of the strong discontinuity model featuring full 3-D kinematics. Simple heterogeneous simulations show numerical applications of the model to the problem of a single spherical inclusion embedded into a homogeneous matrix. Comparisons will be made with another E-FEM model considering a single local fracture mode approach to discuss the differences on the representation of fracture physics under all explored conditions. A concluding statement is made on the benefits and complications identified for the E-FEM framework in this kind of applications.

scholarly journals Direct current simulation in acrylic box using 3D finite element method

2019 ◽  
Author(s):  
Y. A. Laksono ◽  
S. Zulaikah ◽  
S. Sunaryo ◽  
H. Heriyanto ◽  
S. Hidayat
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Direct Current ◽  
3D Finite Element ◽  
3D Finite Element Method ◽  
Element Method
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