Combination Of FEM Research Articles

Prediction method for maize kernel impact breakage based on high-speed camera and FEM

Processes such as threshing and processing determine the subsequent storage, nutritional value, and economic value of maize kernels. The breakage characteristics of maize kernels in threshing and processing machinery are unknown, which greatly limits the need for new developments in low-loss threshing. In this paper, the breakage characteristics of maize kernels under different impact postures and impact velocities were investigated by a combination of FEM and bench tests. The results showed that the breakage evolution rules of kernel breakage modes were the result of stress concentration and energy conversion. The maize kernel with side posture had the smallest critical breakage velocity of 22.5 m/s for breaking into pieces. A breakage probability model for predicting the degree of maize kernel breakage was proposed, and the energy and velocity thresholds provided a method for the digital design of breakage reduction performance of maize threshing machinery and detection performance of impact breakage machinery.

Surface effects of molten slag spills on calcium aluminate cement paste

Industries such as metal, ceramics and petrochemicals suffer from high temperature spills. Such events exert a unique form of loading in concrete structures that cannot be accurately simulated by heating of samples in an oven. Calcium aluminate cement (CAC) based concrete is the industry standard for such environment, and while much is known regarding its heating, literature considering hot spills on concrete surfaces is scarce. In this paper, slag is heated up to the same temperature as in a steel factory and then poured on top of cement paste samples with W/C ratios of 0.20 and 0.40. A combination of FEM, TGA, XRD and SEM/EDS was used to investigate the effects of hot spill on the samples. The rapid expansion caused by the thermal shock generated cracks in only some of the samples, while the high temperature environment and unidirectional escape of water caused chemical changes in all samples.

HYPOGLYCEMIC ACTIVITY OF ETHYL ACETATE FRACTION COMBINATION OF MORINDA FRUIT AND CINNAMON BARK USING GLUCOSE-INDUCED IN MICE

Objective: Noni fruit (Morinda citrifolia L) and cinnamon bark (Cinnamomum burmannii) are plants that have the hypoglycemic effect on their ethyl acetate fraction in the single dose. This study was to determine the hypoglycemic activity of the combination of ethyl acetate fraction (FEM) and cinnamon bark (FEC) in glucose-induced mice, as well as the dose of the combination of FEM and FEC which could have a hypoglycemic effect.
 Methods: The methods were including extraction using liquid-liquid extraction, identification by TLC, and assay of hypoglycemic activity in mice induced by oral glucose for a moment in the eight groups that were normal control, negative control, positive control, dose 1-5. The activity tests were performed at 30th, 60th, 90th and 120th of minutes.
 Results: The research showed that the yield of FEM and FEC were 5.25% and 8.05%. Identification of compounds by TLC showed that the FEM and FEC were 4 and 3 spots. The results of a hypoglycemic test showed that the combination of FEM and FEC on glucose-induced mice showed a decreased effect of mice blood glucose levels better than a single dose of these fractions.
 Conclusion: The hypoglycemic activity test at a combined dose of FEM 175 mg/kg BW and FEC 150 mg/Kg BW have provided hypoglycemic activity better compared to other dose groups with a percentage decrease in average relative blood glucose at the 30th, 60th, 90th, 120th minute were 29.57%, 44.94%, 43.40% and 40.55%, respectively. Thus, the combination of the FEM and FEC in glucose-induced mice gave a hypoglycemic effect in mice.

Creep damage and fracture of notched specimens under static and fast periodic loading

Creep-damage processes in notched specimens subjected to static and periodic loading are studied experimentally. Subsequent simulations were carried out using Rabotnov evolution equation. In case of dynamic creep (fast periodic loading) the constitutive equations derived by use of asymptotic and averaging methods were used. Numerical results were obtained by the combination of FEM and predictor-corrector time integration scheme. Fracture process was studied using designed numerical procedure based on the elimination of the finite elements with critical values of damage parameter. The fracture times and directions of the crack propagation were determined. The qualitative difference between processes of crack propagation in cases of static and periodic loading were observed.

Transmission loss analysis in a partitioned duct with porous boundaries based on combination of FEM and measurement of sound absorption coefficients

The acoustic wave propagation is studied in a partitioned duct with porous boundaries, with emphasis on the effect of porous material in the calculations by FEM. There are several models of the porous materials in simulation softwares like COMSOL, but the necessary parameters are not generally known for porous material which are products for business. This paper describes a method which estimate the parameters of porous material in COMSOL, using the sound absorption coefficients measured in impedance tube. The present study investigates numerically and experimentally the performance of partitioned ducts with right-angled corners, applied for noise reduction in places having a deafening noise of high frequency.

Improvement in determining the risk of damage to the human lumbar functional spinal unit considering age, height, weight and sex using a combination of FEM and RSM.

Human functional spinal unit (FSU) is comprised of two adjacent vertebrae, the intervertebral disc (IVD), the cartilage endplates and the connecting ligamentous tissues. As humans age, trabecular, cortical bone and IVD change in mechanical properties. These changes influence the movement of the FSU (displacements, rotations and disc bulges). This paper proposes a method to determine the influence of sex, age, weight and height on the movements of the FSU using a combination of the FEM and RSM. The work concentrates on the medium-sized human FSU (L3-L4 lumbar level with standard dimensions of IVD: width = 50mm, depth = 35mm and height = 11mm). Also, the proposed method could be an improvement to the determination of risk of damage based on body mass index (BMI), as well as an alternative method of searching for a healthy weight. The method was developed as follows: First, a three-dimensional parameterized human healthy FSU FE model was generated based on the standard test (for compression, flexion, extension, lateral bending, torsion and shear). The movements of the FSU FE model based on the aforementioned standardized test when the sex, age, weight and height varies in a range for each individual (30-80 years; 70-120 kg; 160-190 cm) were simulated. Quadratic regression models were generated for each standardized test using RSM. An ANOVA test showed that all of the tests have a significant influence on weight and age, whereas height influences only those tests that involve rotation of the FSU (flexion, extension and lateral bending). Normal weight, overweight and obesity BMI classifications were considered in determining the healthy weight with the following constraints: the limit angles of flexion and lateral bending, as well as the maximum posterior bulge limit of the IVD, could not exceed of one-third of the spinal canal. The proposed method concluded that: (1) normal BMI values do not cause damage to the FSU, (2) some overweight BMI values may cause damage to the FSU for a certain range of ages and heights and (3) for BMI obesity values, the risk of damage to the FSU may be imminent.

Analysis of Mine Ventilation Network by 1D FEM: Simulation of Fans and Natural Draught

The version of simulating fans in mine ventilation network analysis by using the combination of FEM with the laminar solution method is considered. Two ways of fan insertion are discussed: in the form of a separate active element and in the form of combined element (an active element inserted into a passive element). The latter approach allows changing a position of the fan in a design stage without renumbering of a grid. The method of chords is used to linearize in general nonlinear fan characteristic. It is shown that the dependence of air discharge on the upstream-downstream pressure difference is an ascending curve for the fan. This provides a convergence for the iterative procedure of solving the FEM nonlinear equations system. A method of calculation of convective heat transfer between the air flow and the rock wall based on Lyon’s solution for a pipe with the constant density of boundary heat flow is described. As the density of heat flow and the air properties are slowly varying functions along a mine working (a branch of a network), then discretizing each branch into small segments permits to consider these parameters as constant along segments. Calculation of nonhomogeneous temperature field and treatment of gravity allow modelling the natural draught effect. The results of solution of the test problems validating used algorithms are given. Calculation results of flow mass rate in a mine network within the year are also represented which make it possible to estimate the influence of natural draught on venting capability.

Assessment of seismic behavior stone bridge using a finite element method and discrete element method

Seismic behavior of Osmanli and Senyuva stone bridges was addressed in this study. A combination of FEM and DEM was employed for getting closer to the real behavior of the bridge. One of the unique features of this combinational method is simulation close to reality. Modal numerical analysis was also used to verify the modeling. At the end of earthquake, a part of two lateral walls of Osmanli bridge was broken. The growth of arch cracks also increased during the earthquake. A part of right-hand wall of Senyuva Bridge was destructed during the earthquake. The left-hand side of the bridge wall was damaged during the earthquake but was not destructed.

Design Optimization and Fabrication of a Novel Structural SOI Piezoresistive Pressure Sensor with High Accuracy.

This paper presents a novel structural piezoresistive pressure sensor with four-grooved membrane combined with rood beam to measure low pressure. In this investigation, the design, optimization, fabrication, and measurements of the sensor are involved. By analyzing the stress distribution and deflection of sensitive elements using finite element method, a novel structure featuring high concentrated stress profile (HCSP) and locally stiffened membrane (LSM) is built. Curve fittings of the mechanical stress and deflection based on FEM simulation results are performed to establish the relationship between mechanical performance and structure dimension. A combination of FEM and curve fitting method is carried out to determine the structural dimensions. The optimized sensor chip is fabricated on a SOI wafer by traditional MEMS bulk-micromachining and anodic bonding technology. When the applied pressure is 1 psi, the sensor achieves a sensitivity of 30.9 mV/V/psi, a pressure nonlinearity of 0.21% FSS and an accuracy of 0.30%, and thereby the contradiction between sensitivity and linearity is alleviated. In terms of size, accuracy and high temperature characteristic, the proposed sensor is a proper choice for measuring pressure of less than 1 psi.

Combination of FEM and CMA‐ES algorithm for transmissivity identification in aquifer systems

AbstractIn this paper, we propose a coupling of a finite element model with a metaheuristic optimization algorithm for solving the inverse problem in groundwater flow (Darcy's equations).This coupling performed in 2 phases is based on the combination of 2 codes: This is the HySubF‐FEM code (hydrodynamic of subsurface flow by finite element method) used for the first phase allowing the calculation of the flow and the CMA‐ES code (covariance matrix adaptation evolution strategy) adopted in the second phase for the optimization process. The combination of these 2 codes was implemented to identify the transmissivity field of groundwater by knowing the hydraulic head in some point of the studied domain. The integrated optimization algorithm HySubF‐FEM/CMA‐ES has been validated successfully on a schematic case offering an analytical solution.As realistic application, the integrated optimization algorithm HySubF‐FEM/CMA‐ES was applied to a complex groundwater in the north of France to identify the transmissivity field. This application does not use zonation techniques but solves an optimization problem at each internal node of the mesh. The obtained results are considered excellent with high accuracy and fully consistent with the hydrogeological characteristics of the studied aquifer.However, the various numerical simulations performed in this paper have shown that the CMA‐ES algorithm is time‐consuming. Finally, the paper concludes that the proposed algorithm can be considered as an efficient tool for solving inverse problems in groundwater flow.

Damper Currents Simulation of Large Hydro-Generator Using the Combination of FEM and Coupled Circuits Models

A high-order model is required for an accurate simulation of the synchronous alternator spatial harmonic content. However, some hydro-generators have fractional slot per pole per phase windings, and carrying transient simulations of these machines with finite-element software often leads to unacceptable computation time. This paper details a large alternator modeling method that provides an excellent compromise between accuracy and speed. It is a combination of magnetostatic finite element method and coupled circuits model. The paper details the construction of this model and explains the procedures to identify several model parameters from experimental data as the standstill frequency response and open and short circuit tests. The effectiveness of this modeling method is validated by the study of a large 109-MVA hydrogenerator having an instrumented rotor pole. We compare transient and steady-state simulation waveforms of the damper bar currents during sudden two- and three-phase short-circuit to the experimental measures.

Using a Combination of FEM and Perturbation Method in Frequency Split Calculation of a Nearly Axisymmetric Shell with Middle Surface Shape Defect

Using a Combination of FEM and Perturbation Method in Frequency Split Calculation of a Nearly Axisymmetric Shell with Middle Surface Shape Defect

Stress Analysis and Improvement of Extrusion Dies Using Combination of FEM with Taguchi Method

This study aims at analyzing the influence of the maximum principal stress on Tungsten Carbide Steel die core in an extrusion die which caused the crack of die core, and then adjusts the dies assembly method in order to improve the service life of die. In this study, combining FEM simulation software with Taguchi Method L9(34) is to choose the cobalt content for die core materials, and the quantity of shrink fit while assembling the die core and die case as the reference parameters. When carrying out the simulation process, compared the changes of the maximum principal stress of the die core caused by the plastic deformation of die materials to achieve the minimum expected value as the goal be chosen the most optimal die combination. Then, the results obtained are to make dies in trial and mass-production practically; as a result, it can be achieved that the die life is improved from the original 1000pcs to 150000pcs, which is more 150 times better than before.

Parameter Identification with FEM on Absorbing Boundary Condition and Genetic Algorithm (GA)

Researches of wave motion are important on theory and application. The forward problem and the backward problem are the two aspects that relate with each other. In this paper, with the combination of FEM considering BGT absorbing boundary condition for forward problem and GA method, the inversion of target’s characters in infinite area is discussed. The absorbing boundary condition is obtained through approximating the Sommerfeld radiation condition. Although the absorbing boundary condition can’t simulate the effect exactly, it can reach the limitation in the practice and has the character of solving the coupling that simplifies the calculations. Because of the use of finite element model method, the forward problems that involve special geometrical shaped scatter and multi scatters can be solved. The finite element model is used iteratively to compute the scattered field. In the inversion process, the GA method is adopted because of its advantage of global optimum search and parallel calculation. The numerical simulation examples of single and multiple show the validity of this method.

A Method for Numerical Solutions to Problems with Pipes under Unknown Forces and Constraint Conditions

For the solutions to engineering equipment with pipes, unknown forces and unclear constraint conditions on the pipes result in the analysis limitation due to the high temperature and fluid pressure to pipes. In this paper, a new method for determining the loads is established to problems with many pipes. In the method, based on the combination of FEM and Successive Approximation Approach, pipes forces on the equipment are analyzed. By the analysis of suitable forces, the relationship between forces and stress can be obtained. The cycling process of “loading-solving-determining-adjusting” is carried out to approaching destinations based on hundreds of numerical results. Moreover, an evaluation scheme is built to evaluate groups of forces and guarantee equipment to work normally under some certain forces. The constraint condition from groups of forces can be also confirmed. A case study gave the verification of the method.

Prediction of the sound field in anechoic rooms : comparison of two different approaches

Despite the numerical advances, predicting the sound field in anechoic rooms is still challenging because it requires a fine modeling of the wall surface, acoustic properties and geometry, and the computation of the room sound field. It is proposed here to compare two innovative approaches to predict the performance of anechoic wedges, in particular to quantify the influence of porous frame motion, and to propose a numerically efficient model for the prediction of the sound field in anechoic room sounds at low frequencies. The first approach relies on the theory for modeling the sound propagation in double porosity media first presented by Olny & Boutin [J. Acoust. Soc. Am. 114 (1), 2003]. It has been shown that this approach could accurately predict the cut-off frequency of anechoic wedges. The interest is that this approach is numerically costless and that complex geometry could be considered. The second approach is based on the combination of FEM and BEM. It allows to predict the sound field in anechoic rooms. Compared to the previous approach, the latter one has the advantage of being able to identify structural effects inside the wedges and to propose an accurate prediction of the sound field in the room.

P25: Design of Forging Process by Combination of FEM and ANN(SHORT ORAL PRESENTATION FOR POSTERS II)

P25: Design of Forging Process by Combination of FEM and ANN(SHORT ORAL PRESENTATION FOR POSTERS II)

Analysis of Stress Concentration Problems by the Combination of FEM and BFM.

In this paper, a method for calculating the stress concentration factor or stress intensity factor is proposed and applied to the problem of the effect of gripped part in a plate specimen. This method is based on the combination of FEM and BFM (body force method). In this method first a given problem is analyzed by FEM and the surface stresses on an imaginary boundary including the source of stress concentration are calculated. Secondarily, BFM is applied to the partial body whose boundary is the imaginary boundary. In the analysis the boundary condition is given by the surface stresses on the imaginary boundary obtained by FEM. Because the accuracy of FEM on the imaginary boundary is comparatively high and the accuracy of BFM is extremely high, the accuracy of this method is high.

140 有限要素法と体積力法の併用による応力集中問題の解析

In this paper, a method for calculating the stress concentration factor or stress intensity factor is proposed and applied to the problem of the effect of gripped part in a plate specimen. This method is based on the combination of FEM and BFM (body force method). In this method first a given problem is analyzed by FEM and the surface stresses on an imaginary boundary including the source of stress concentration are calculated. Secondarily, BFM is applied to the partial body whose boundary is the imaginary boundary. In the analysis the boundary condition is given by the surface stresses on the imaginary boundary obtained by FEM. Because the accuracy of FEM on the imaginary boundary is comparatively high and the accuracy of BFM is extremely high, the accuracy of this method is high.

FEMと最適化ソフトの組合せによる鋼橋最小重量化設計の試み

FEMと最適化ソフトの組合せによる鋼橋最小重量化設計の試み