Reconstruction of complex shaped crack from ECT signals based on a fast forward solver using an advanced multi-media element

In this paper, the conventional database type fast forward solver for efficient simulation of eddy current testing (ECT) signals is upgraded by using an advanced multi-media finite element (MME) at the crack edge for treating inversion of complex shaped crack. Because the analysis domain is limited at the crack region, the fast forward solver can significantly improve the numerical accuracy and efficiency once the coefficient matrices of the MME can be properly calculated. Instead of the Gauss point classification, a new scheme to calculate the coefficient matrix of the MME is proposed and implemented to upgrade the ECT fast forward solver. To verify its efficiency and the feasibility for reconstruction of complex shaped crack, several cracks were reconstructed through inverse analysis using the new MME scheme. The numerical results proved that the upgraded fast forward solver can give better accuracy for simulating ECT signals, and consequently gives better crack profile reconstruction.

ANALISA DISPERSI PM2,5 MENGGUNAKAN MODEL GAUSS POINT SOURCE DIKAWASAN INDUSTRI DAN DESAIN VENTURI SCRUBBER BESERTA IPAL UNTUK EFFLUENT VENTURI (Studi Kasus : Industri Peleburan Aluminium PT.X Kecamatan Kesamben, Jombang)

Kegiatan Industri Peleburan Aluminium PT.X mengakibatkan kualitas udara di sekitar industri menurun hal tersebut ditandai oleh beberapa keluhan dari masyarakat, PM2,5 merupakan salah satu partikulat yang ditimbulkan dari proses peleburan aluminium yang mana sangat berpengaruh negatif terhadap kesehatan manusia. Tujuan dari penelitian adalah menganalisis konsentrasi PM2,5 di kawasan penduduk menggunakan model gauss point source serta mendesain alat pengendali pencemar udara venturi scrubber untuk dapur peleburan aluminium beserta instalasi pengolahan air limbah. Hasil perhitungan menunjukkan bahwa konsentrasi PM2,5 di kawasan industri PT.X titik 1 (50 m dari lokasi industri) yaitu 2,7 x 10-5/m3, titik 2 (100 m dari lokasi industri) yaitu 6,7 x 10-6/m3, titik 3 (200 m dari lokasi industri) yaitu 1,6 x 10-6/m3 dari ketiga titik tersebut masih memenuhi baku mutu udara ambient Peraturan Pemerintah Republik Indonesia No. 41 Tahun 1999. Hasil perhitungan desain venturi scrubber diperoleh dimensi venturi diameter throat (lebar) 0,55 m, panjang throat 1,65 m, dan panjang bagian diverging 2,2 m prosentase removal partikulat PM2,5 sebesar 95% dan hasil perhitungan desain IPAL diperoleh untuk bangunan koagulasi dengan dimensi Panjang 0,86 m, lebar 0,86 m dan tinggi 1,2 m, bangunan Flokulasi diperoleh panjang 2,1 m , lebar 4,2 m dan tinggi 2 m, bangunan Sedimentasi dengan diameter 5,6 m dan tinggi 1,57 m. Rencana Anggara Biaya dari perhitungan desain didapatkan untuk desain Venturi Scrubber dan IPAL yaitu sebesar Rp. 83.647.421.

Non-linear deflection and stress analysis of laminated composite sandwich plate with elliptical cutout under different transverse loadings in hygro-thermal environment

In this paper, non-linear transverse deflection, stress and stress concentration factors (SCF) of isotropic and laminated composite sandwich plate (LCSP) with and without elliptical cutouts subjected to various trans-verse loadings in hygrothermal environment are studied. The basic formulation is based on secant function-based shear deformation theory (SFSDT) with von-Karman nonlinearity. The governing equation of non-linear deflection is derived using C0 finite element method (FEM) through minimum potential energy approach. Normalized trans-verse maximum deflections (NTMD) along with stress concentration factor is determined by using Newton’s Raphson method through Gauss point stress extrapolation. Influence of fiber orientations, load parameters, fiber volume fractions, plate span to thickness ratios, aspect ratios, thickness of core and face, position of core, boundary conditions, environmental conditions and types of transverse loading in MATLAB R2015a environment are examined. The numerical results using present solution methodology are verified with the results available in the literatures.

An Optimized Generalized Integration Rules for Error Reduction of Acoustic Finite Element Model

In the finite element method (FEM), the accuracy in acoustic problems will deteriorate with the increasing frequency due to the “dispersion effect”. In order to minimize discretization error, a novel optimized generalized integration rules (OGIR) is introduced into FEM for the reduction of discretization error. In the present work, the adaptive genetic algorithm (AGA) is implemented to sight the optimized location of integration points. Firstly, the generalized integration rules (GIR) is used to parameterize the Gauss point location, then the relationship between the location parameterize of the integration points and discretization error is derived in detail, and the optimized location of the integration points is found through the optimization procedure, and then the OGIR–FEM is finally proposed to solve the acoustic problem. It also can be directly used to solve the optional acoustic problem, including the damped problems. Numerical example involving distorted meshes indicates that present OGIR–FEM has a superior error reducing performance in comparison with the other error reducing finite elements. These researches indicate that the proposed method can be more widely applied to solving practical acoustic problems with more accurate solutions.

An efficient multiscale modeling framework for nonlinear analyses of composite structures

Traditional multiscale modeling methods of composite structures are based on the global-local approach whereby the global analysis of structures are first performed to determine potential damage regions, followed by local analyses at those regions to identify detailed damage patterns and failure modes. Such an approach does not take into account the localized effects of critical regions on the global analysis and may become less accurate in general. To address better the behavior of local regions on multiscale analyses, homogenization-based multiscale methods are applied. For each load increment, the global problem is solved simultaneously with one Representative Volume Element (RVE) equilibrium problem for each Gauss point of the global mesh. This approach is successful to capture the local behavior at each material point; however, it is computationally expensive since the RVE is called at all the Gauss points in the global model for each load increment. We develop an efficient multiscale modeling method whereby the RVE analyses are only called at specialized locations by multiscale elements and run parallel with the global analysis. The constitutive models of multiscale elements are defined in a user-defined element subroutine (UEL) where stiffnesses of the multiscale elements are unknown at the beginning of the analysis. They can only be obtained by performing a series of RVE analyses for each set of loads received from the global analysis. The advantage of the proposed method is that the stiffnesses of the multiscale elements are directly computed from the RVE analyses and keep updated for each global load increment. The nested multiscale modeling is implemented by Python script and highly capable for nonlinear analysis of composite structures.