• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.22-29
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• 2004

Deformation of the porous media has influence on performance of a proton exchange membrane fuel cell (PEMFC). The stress distributions and deformation of the porous media are major factors for safe and efficient operation in the PEMFC. In this paper, nonlinear contact analysis of air plate and porous media is performed under a working condition to predict the performance characteristics of the air plates. Two kinds of models are suggested for this study. The first porous media model has nonlinear material properties. The second model has nonlinear material properties with contact condition between porous media and air plate. The numerical analysis results of the two models are somewhat different. It is shown that the nonlinear contact analysis is required for the design study of the PEMFC.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.957-962
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• 2012

Fluid/structure interaction (FSI) analysis is necessary to predict the response of a system in which aerodynamic pressure causes deformation of the structure, and vice versa. In dealing with a nonlinear behavior of the structure, however, a simple iterative algorithm of aerodynamic analysis with structural analysis yields no accurate results since aerodynamic pressure need to be changed in accordance with the deformation of structures. In this study, we explore an efficient and accurate method for integrating FSI analysis into structural nonlinear systems. During the course of nonlinear structural analysis, loading conditions are periodically updated by aerodynamic analysis. The accuracy and efficiency of the method is demonstrated with a high-aspect-ratio flexible wing of Global Hawk.

• Smart Structures and Systems
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• v.31 no.2
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• pp.101-111
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• 2023

Structural health monitoring (SHM) covers a range of damage detection strategies for buildings. In real-time, SHM provides a basis for rapid decision making to optimise the speed and economic efficiency of post-event response. Previous work introduced an SHM method based on identifying structural nonlinear hysteretic parameters and their evolution from structural force-deformation hysteresis loops in real-time. This research extends and generalises this method to investigate the impact of a wide range of flag-shaped or pinching shape nonlinear hysteretic response and its impact on the SHM accuracy. A particular focus is plastic stiffness (K_p), where accurate identification of this parameter enables accurate identification of net and total plastic deformation and plastic energy dissipated, all of which are directly related to damage and infrequently assessed in SHM. A sensitivity study using a realistic seismic case study with known ground truth values investigates the impact of hysteresis loop shape, as well as added noise, on SHM accuracy using a suite of 20 ground motions from the PEER database. Monte Carlo analysis over 22,000 simulations with different hysteresis loops and added noise resulted in absolute percentage identification error (median, (IQR)) in K_p of 1.88% (0.79, 4.94)%. Errors were larger where five events (Earthquakes #1, 6, 9, 14) have very large errors over 100% for resulted K_p as an almost entirely linear response yielded only negligible plastic response, increasing identification error. The sensitivity analysis shows accuracy is reduces to within 3% when plastic drift is induced. This method shows clear potential to provide accurate, real-time metrics of non-linear stiffness and deformation to assist rapid damage assessment and decision making, utilising algorithms significantly simpler than previous non-linear structural model-based parameter identification SHM methods.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.3
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• pp.47-53
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• 2005

The non-linear finite element program of the large deformation analysis by computer simulation has been used in the prediction and evaluation of the behaviors of the non-linear rubber components. The analysis of rubber components requires the tools modelling the special materials that are quite different from those used for the metallic parts. The nonlinear simulation analysis used in this study is expected to be widely applied in the design analysis and the development of several rubber components which are used In the manufacturing process of many industries. By utilizing this method, the time and cost can also be saved in developing the new rubber product. The objective of this study is to analyze the rubber component with the large deformation and non-linear properties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.1014-1019
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• 2003

A dynamic modeling method for beams undergoing overall rigid body motion is presented in this paper. Two special deformation variables are introduced to represent the stretching and the curvature and are approximated by the assumed mode method. Geometric constraint equations that relate the two special deformation variables and the cartesian deformation variables are incorporated into the modeling method. By using the special deformation variables, all natural as well as geometric boundary conditions can be satisfied. It is shown that the geometric nonlinear effects of stretching and curvature play important roles to accurately predict the dynamic response when overall rigid body motion is involved.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.148-153
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• 1998

In order to control thermal deformation of machine origin of machine tools due to internal and external heat sources, the real-time compensation system has been developed. First, GMDH models were constructed to estimate thermal deformation of machine origin for a vertical machining center through the measurement of deformation data and temperature data of specific points on the machine tool. Thermocouples and gap sensors are used respectively for measurement. These models are nonlinear equations with high-order polynomials and implemented in a multilayered perceptron type network structure. Secondly, work origin shift method were developed by implementing digital I/O interface board between CNC controller and IBM-PC. The work origin shift method is to shift the work origin by the compensation amounts which is calculated by pre-established GMDH model. From the experimental result, thermal deformation of machine origin was reduced to below $\pm$5${\mu}{\textrm}{m}$.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.7-23
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• 2007

The shear wave velocity is directly related to the deformation characteristic of soils which is an engineering property represented by the shear modulus. This feature presents an opportunity of advantageous utilization of the shear wave velocity for deformation analysis in geotechnical engineering applications, since the deformation modulus is determined on strong theoretical basis, whereas penetration resistances such as N by SPT or qc by CPT rely on empirical relations. Furthermore, it is an engineering property that can be evaluated by performing the same basic measurement in the laboratory and field, and various problems in geotechnical engineering can be dealt with economically and reliably when the field and laboratory methods are combined effectively. In this article, assessment of nonlinear deformation characteristic of soils based on synergic use of the field and laboratory test results is described, and representative case histories of geotechnical applications of the shear wave velocity are illustrated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.06a
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• pp.173-184
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• 1994

A method of obtaining deformation severity of axisymmetric shape deep-drawn products was developed. Strain states of products produced by single or multi-stage drawing were predicted by using finite element analysis. This method used minimization of potential energy between the known shape of final product and the unknown in initial blank. And that was done numerically by nonlinear finite element method. Deformation theory of plasticity was used for practical purposes. From predicted strain states of drawn parts, deformation severity was found by using forming limit diagrams.

• The Journal of Korea Robotics Society
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• v.17 no.1
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• pp.68-75
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• 2022

In this paper, we considered the deformation shape of the soft rotation actuator as a double curvature shell and proceeded with the analytical development. Since the response of the hyperelastic material has a large nonlinear deformation, the analytical approach is very complicated and the solution cannot be easily obtained. it is assumed that the behavior of the flexible body, which is a superelastic material, takes the form of a double curvature shell, and the formulas for calculating the deformation are simplified. In this process, equilibrium equations in the related coordinate system representing a double curvature shell were derived. In addition, assuming a thin shell, the stress component in the thickness direction was ignored, and the equation was developed by adding the assumption of free rotation without load. In order to verify the analytically calculated value in this way, an experiment was conducted and the results were compared.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.49-57
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• 2023

This study investigated the rocking behavior of unreinforced masonry walls and wall piers under cyclic loading. Based on the benchmark tests, the characteristics of load-deformation relations in masonry walls with rocking failure were captured, focusing on observed deformation modes. The rocking strengths of masonry walls (i.e., peak and residual strengths) were evaluated, and the effects of opening configurations on the masonry wall strength were examined. The deformation capacity of the rocking behavior and the hysteresis shape of the load-deformation relations were also identified. Based on the results, modeling approaches for the rocking behavior of masonry walls were discussed.