• 대한기계학회논문집A
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• 제29권3호
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• pp.484-494
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• 2005

Finite element method is very effective method to simulate the forming processes with good prediction of the deformation behaviour. For the finite element modeling of sheet mental forming the accurate tool model is required. Due to the geometrical complexity of real-size part stamping tools it is hard to make FE model for real-size auto-body stamping parts. In this paper, it was focussed on the drawability factors on auto-body panel stamping by AUTOFORM with using tool planing alloy to reduce law price as well as high precision from Design Optimization of die. According to this study, the results of simulation will give engineers good information to access the Design Optimization of die.

• Interaction and multiscale mechanics
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• 제2권1호
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• pp.1-14
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• 2009

This paper proposes an interaction field concept based on the field theory of plasticity. Relative deformation between two arbitrary scales, e.g., macro and micro fields, is defined which can be implemented in the crystal plasticity-based constitutive framework. Differential geometrical quantities responsible for describing dislocations and defects in the interaction field are obtained, based on which dislocation density and incompatibility tensors are further derived. It is shown that the explicit interaction exists in the curvature or incompatibility tensor field, whereas no interaction in the torsion or dislocation density tensor field. General expressions of the interaction fields over multiple scales with more than three scale levels are derived and implemented into the present constitutive equation.

• Computers and Concrete
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• 제21권1호
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• pp.31-37
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• 2018

This paper deals with the stability analysis of concrete pipes mixed with nanoparticles conveying fluid. Instead of cement, the $Fe_2O_3$ nanoparticles are used in construction of the concrete pipe. The Navier-Stokes equations are used for obtaining the radial force of the fluid. Mori-Tanaka model is used for calculating the effective material properties of the concrete $pipe-Fe_2O_3$ nanoparticles considering the agglomeration of the nanoparticles. The first order shear deformation theory (FSDT) is used for mathematical modeling of the structure. The motion equations are derived based on energy method and Hamilton's principal. An exact solution is used for stability analysis of the structure. The effects of fluid, volume percent and agglomeration of $Fe_2O_3$ nanoparticles, magnetic field and geometrical parameters of pipe are shown on the stability behaviour of system. Results show that considering the agglomeration of $Fe_2O_3$ nanoparticles, the critical fluid velocity of the concrete pipe is decreased.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.559-562
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• 2004

Carbon nanotube is a geometrical frame-like structure and the primary bonds between two nearest-neighboring atoms act like beam members, whereas an individual atom acts as the joint of the related beam members. The sectional property parameters of these beam members are obtained from molecular mechanics. Computations of the elastic deformation of single-walled carbon nanotubes reveal that the Young's moduli of carbon nanotubes vary with the tube diameter and are affected by their helicity. With increasing tube diameter, the Young's moduli of carbon nanotubes approach the Young's modulus of graphite.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.329-337
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• 2017

This study concerns the vibrational behavior of multi-walled nested silicon-carbide and carbon nanotubes using the finite element method. The beam elements are used to model the carbon-carbon and silicon-carbon bonds. Besides, spring elements are employed to simulate the van der Waals interactions between walls. The effects of nanotube arrangement, number of walls, geometrical parameters and boundary conditions on the frequencies of nested silicon-carbide and carbon nanotubes are investigated. It is shown that the double-walled nanotubes have larger frequencies than triple-walled nanotubes. Besides, replacing silicon carbide layers with carbon layers leads to increasing the frequencies of nested silicon-carbide and carbon nanotubes. Comparing the first ten mode shapes of nested nanotubes, it is observed that the mode shapes of armchair and zigzag nanotubes are almost the same.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.634-642
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• 2006

The aim of this paper is to increase the performance of hysteresis compensation for Shape Memory Alloy (SMA) actuators by using inverse Preisach model in closed-loop control system. This is used to reduce hysteresis effects and improve accuracy for the displacement of SMA actuators. Firstly, hysteresis is identified by numerical Preisach model implementation. The geometrical interpretation from first order transition curves is used for hysteresis modeling. Secondly, the inverse Preisach model is formulated and incorporated in closed-loop PID control system in order to obtain desired current-to-displacement relationship with hysteresis reducing. The experimental results for hysteresis compensation by using this method are also shown in this paper.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.138-141
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• 2004

Finite element method is very effective method to simulate the forming processes with good prediction of the deformation behaviour. For the finite element modeling of sheet mental forming the accurate tool model is required. Due to the geometrical complexity of real-size part stamping tools it is hard to make FE model for real-size auto-body stamping parts. In this paper, it was focussed on the drawability factors on auto-body panel stamping by AUTOFORM with using tool planing alloy to reduce law price as well as high precision from Design Optimization of die. According to this study, the results of simulation will give engineers good information to access the Design Optimization of die.

• 한국정밀공학회지
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• 제22권7호
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• pp.94-101
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• 2005

This work proposes a new method for describing the hysteresis non-linearity of a piezoelectric actuator. The hysteresis behaviour of piezoelectric actuators, including the minor loop trajectory, are modeled by geometrical relationship between a reference major loop and its minor loops. This hysteresis model is transformed into inverse hysteresis model in order to output compensated voltage with regard to the given input displacement. A feedforward neural network, which is trained by a feedback PID control module, is incorporated to the inverse hysteresis model to compensate unknown dynamics of the piezoelectric system. To show the feasibility of the proposed feedforward-feedback controller, some experiments have been carried out and the tracking performance was compared to that of simple PTD controller.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.953-957
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• 1994

A performance prediction method is presented in this paper for design of a rotating machinery having power split/circulated transmisson with slip elements and planetary gears. And internal power flow patterns of such systems are theoretically analyzed by using mathematical modeling. To estimate usefulness of the designed machinary, geometrical approach has been adopted through the performance locus diagram which represents overall characteristics of the system. This gives us complect prediction of the qualitative performane and effects of design factors such as system layout, types and gear ratios of planetary gears and disign parameters of slip elements. The results for one of them are compared with experimental ones using dynamometer for verification.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.234-238
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• 2015

When we use a Finite Elements Method (FEM) to solve a linear static analysis problem, number of elements need to be sufficiently small for convergence of the solution. If we analysis a part, whose curvature is varying heavily, we face to determine how small the elements size is, because the calculated stress is increased as the elements are smaller. In this case, we need to analysis with mesh insensitive method, stress linearization. We can get a solution that is not varying with the elements size if the size is smaller than a certain level. In this paper, we evaluate a pressure vessel having geometrical discontinuities using stress linearization. First, we analysis the vessel with global model, including all part of the vessel, using large shell elements. Second, we analysis the local part of the vessel, which is the small part occurring maximum stress, using small continuum elements. Last, we evaluate the safety of the pressure vessel according to the ASME Sec. VIII Div 2.