• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1290-1300
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• 1996

The finite element method, based on rigid-plastic formulation, is widely used to simulate metal forming processes. In order to improve the computational efficiency of the rigid-plastic FEM, one-point integration is used to evaluate the stiffness matrix with four-node rectangular elements and eight-node brick elements. In order to control the hourglass modes, hourglass strain rate components were introduced and included in the effective strain rate definition, Numerical tests have shown that the proposed one-point integration scheme reduces the stiffness matrix evaluation time without deteriorating the convergence behavior of Newton-Raphson method. Simulations of a ring compression, a plane-strain closed-die forging and the three-dimensional spike forging processes were carried out by using the proposed integration method. The simulation results are compared to those obtained by applying the conventional integraiton method in terms of the solution accuracy and computational efficiency.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2312-2320
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• 2005

The aerodynamic effects of leading-edge accretion can raise important safety concerns since the formulation of ice causes severe degradation in aerodynamic performance as compared with the clean airfoil. The objective of this study is to develop a numerical simulation strategy for predicting the particle trajectory around an MS-0317 airfoil in the test section of the NASA Glenn Icing Research Tunnel and to investigate the impingement characteristics of droplets on the airfoil surface. In particular, predictions of the mean velocity and turbulence diffusion using turbulent flow solver and Continuous Random Walk method were desired throughout this flow domain in order to investigate droplet dispersion. The collection efficiency distributions over the airfoil surface in simulations with different numbers of droplets, various integration time-steps and particle sizes were compared with experimental data. The large droplet impingement data indicated the trends in impingement characteristics with respect to particle size ; the maximum collection efficiency located at the upper surface near the leading edge, and the maximum value and total collection efficiency were increased as the particle size was increased. The extent of the area impinged on by particles also increased with the increment of the particle size, which is similar as compared with experimental data.

• The Korean Journal of Food And Nutrition
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• v.28 no.2
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• pp.189-195
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• 2015

Failure of the functions involved in ingestion leads to, not only loss of enjoyment of eating, but also protein-energy malnutrition. Dysmasesis and difficulty of swallowing occurs in various diseases, but aging is a major cause. In the aging society, the proportion of elderly people with dysmasesis and difficulty of swallowing is expected to increase rapidly. Developing foods for the elderly that are easy to chew and swallow is thus required. This study was conducted to develop easily chewable and swallowable foods for the elderly who can crush foods and ingest with their own tongues, but occasionally have difficulty in drinking fluids such as water and tea. Various foods for the elderly with chewing and swallowing difficulties were used for sensory assessment. The sensory panel consisted of 10 dietitians (10 women) in nursing care facilities. The sensory optimal composite recipes were determined by central composite design (CCD). The sensory measurements were significantly different in saltiness (p<0.05), sweetness (p<0.05), and overall quality (p<0.05). The optimum formulation of stir fried anchovy calculated by numerical and graphical methods was 3.74 g of soy sauces and 30.17 g of oligo-saccharides. Stir fried anchovy had a moisture content, hardness and adhesiveness of 76.52%, 2.10, and -1.57, respectively.

• Korean journal of food and cookery science
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• v.28 no.4
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• pp.431-441
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• 2012

The purpose of this study was to determine the optimal mixing conditions, storage, and irradiation characteristics by two different amounts of cabbage powder and water in bread prepared with cabbage powder. A significant increase or decrease in dough pH (p<0.01), sweetness (p<0.05), water content (p<0.001), L-value (p<0.01), a-value (p<0.001), b-value (p<0.001), hardness (p<0.05), springiness, and chewiness (p<0.05) was observed. Sensory measurements showed a significant improvement in appearance, flavor, color, taste (p<0.05), texture, moisture (p<0.01), and overall quality (p<0.05). As a result, the optimum formulation obtained by numerical and graphical methods was 37.04 g cabbage powder and 385.3 g water. The optimized and control breads were irradiated and their DPPH radical scavenging activities and total plate counts were evaluated over 6 days. The result showed the antioxidant and antibiotic action of the bread with cabbage powder.

• Smart Structures and Systems
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• v.19 no.1
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• pp.57-66
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• 2017

Nanocomposites reinforced with carbon nanotube fibers exhibit greater stiffness, strength and damping properties in comparison to conventional composites reinforced with carbon/glass fibers. Consequently, most of the nanocomposite research is focused in understanding the dynamic characteristics, which are highly useful in applications such as vibration control and energy harvesting. It has been observed that those nanocomposites show better stiffness when the geometry of nanotubes is straight as compared to curvilinear although nanotube agglomeration may exist. In this work the damping behavior of the nanocomposite is characterized in terms of loss factor under the presence of nanotube agglomerations. A micro stick-slip damping model is used to compute the damping properties of the nanocomposites with multiwall carbon nanotubes. The present formulation considers the slippage between the interface of the matrix and the nanotubes as well as the slippage between the interlayers in the nanotubes. The nanotube agglomerations model is also presented. Results are computed based on the loss factor expressed in terms of strain amplitude and nanotube agglomerations. The results show that although-among the various factors such as the material properties (moduli of nanotubes and polymer matrix) and the geometric properties (number of nanotubes, volume fraction of nanotubes, and critical interfacial shear stresses), the agglomeration of nanotubes significantly influences the damping properties of the nanocomposites. Therefore the full potential of nanocomposites to be used for damping applications needs to be analyzed under the influence of nanotube agglomerations.

• Steel and Composite Structures
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• v.24 no.6
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• pp.753-765
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• 2017

This paper aims to investigate the strength degradation of reinforced concrete piers wrapped with steel plates which corrode at the pier base by employing a three dimensional elasto-plastic finite element formulation. The prediction accuracy of the employed finite element analysis method is firstly verified by comparing the analytical results with test results. Then, a series of parametric studies is carried out to investigate the effects of steel plate's corrosion position along width direction, corrosion depth along plate thickness, corrosion range along width direction, and steel plate-concrete bonding degradation on the strength of the piers. It is observed that the strength degradation of the piers is closely related to steel plate's corrosion position, corrosion depth and corrosion range in the case of local corrosion on the webs. In contrast, when the base of flanges corrodes, the strength degradation of the piers is only related to steel plate's corrosion depth and corrosion range, and the influence of corrosion position on the strength degradation is very gentle. Furthermore, the strength of the piers decreases with the degradation of steel plate-concrete bonding behavior. Finally, the maximum strength of the piers obtained from numerical analysis corresponding to different bonding behavior is compared with theoretical results within an accepted error.

• Wind and Structures
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• v.27 no.5
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• pp.311-324
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• 2018

This work examines vibration and bending response of carbon nanotube-reinforced composite plates resting on the Pasternak elastic foundation. Four types of distributions of uni-axially aligned single-walled carbon nanotubes are considered to reinforce the plates. Analytical solutions determined from mathematical formulation based on hyperbolic shear deformation plate theory are presented in this study. An accuracy of the proposed theory is validated numerically by comparing the obtained results with some available ones in the literature. Various considerable parameters of carbon nanotube volume fraction, spring constant factors, plate thickness and aspect ratios, etc. are considered in the present investigation. According to the numerical examples, it is revealed that the vertical displacement of the plates is found to diminish as the increase of foundation parameters; while, the natural frequency increase as the increment of the parameters for every type of plate.

• Steel and Composite Structures
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• v.34 no.2
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• pp.241-260
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• 2020

This article presented a comprehensive model to study static buckling stability and associated mode-shapes of higher shear deformation theories of sandwich laminated composite beam under the compression of varying axial load function. Four higher order shear deformation beam theories are considered in formulation and analysis. So, the model can consider the influence of both thick and thin beams without needing to shear correction factor. The compression force can be described through axial direction by uniform constant, linear and parabolic distribution functions. The Hamilton's principle is exploited to derive equilibrium governing equations of unified sandwich laminated beams. The governing equilibrium differential equations are transformed to algebraic system of equations by using numerical differential quadrature method (DQM). The system of equations is solved as an eigenvalue problem to get critical buckling loads and their corresponding mode-shapes. The stability of DQM in determining of buckling loads of sandwich structure is performed. The validation studies are achieved and the obtained results are matched with those. Parametric studies are presented to figure out effects of in-plane load type, sandwich thickness, fiber orientation and boundary conditions on buckling loads and mode-shapes. The present model is important in designing process of aircraft, naval structural components, and naval structural when non-uniform in-plane compressive loading is dominated.

• Structural Engineering and Mechanics
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• v.73 no.1
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• pp.17-25
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• 2020

A finite element (FE) model for analyzing slender reinforced high-strength concrete (HSC) columns under biaxial eccentric loading is formulated in terms of the Euler-Bernoulli theory. The cross section of columns is divided into discrete concrete and reinforcing steel fibers so as to account for varied material properties over the section. The interaction between axial and bending fields is introduced in the FE formulation so as to take the large-displacement or P-delta effects into consideration. The proposed model aims to be simple, user-friendly, and capable of simulating the full-range inelastic behavior of reinforced HSC slender columns. The nonlinear model is calibrated against the experimental data for slender column specimens available in the technical literature. By using the proposed model, a numerical study is carried out on pin-ended slender HSC square columns under axial compression and biaxial bending, with investigation variables including the load eccentricity and eccentricity angle. The calibrated model is expected to provide a valuable tool for more efficiently designing HSC columns.

• Structural Engineering and Mechanics
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• v.72 no.1
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• pp.31-41
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• 2019

Structural integrity assessment of piping components is of paramount important for remaining life prediction, residual strength evaluation and for in-service inspection planning. For accurate prediction of these, a reliable fracture parameter is essential. One of the fracture parameters is stress intensity factor (SIF), which is generally preferred for high strength materials, can be evaluated by using linear elastic fracture mechanics principles. To employ available analytical and numerical procedures for fracture analysis of piping components, it takes considerable amount of time and effort. In view of this, an alternative approach to analytical and finite element analysis, a model based on relevance vector machine (RVM) is developed to predict SIF of part through crack of a piping component under fatigue loading. RVM is based on probabilistic approach and regression and it is established based on Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. Model for SIF prediction is developed by using MATLAB software wherein 70% of the data has been used for the development of RVM model and rest of the data is used for validation. The predicted SIF is found to be in good agreement with the corresponding analytical solution, and can be used for damage tolerant analysis of structural components.