• Proceedings of the KSME Conference
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• 2004.11a
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• pp.667-672
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• 2004

A modeling method for the modal analysis of cantilever plates undergoing in-plane translational acceleration is presented in this paper. Cartesian deformation variables are employed to derive the equations of motion and the resulting equations are transformed into dimensionless forms. To obtain the modal equation from the equations of motion, the in-plane equilibrium strain measures are substituted into the strain energy expression based on Von Karman strain measures. The effects of two dimensionless parameters (related to acceleration and aspect ratio) on the modal characteristics of accelerated plates are investigated through numerical studies.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.97-107
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• 1995

Global postbuckling analysis is accomplished for one-dimensional and two-dimensional delaminations. A new finite element model, which can be used to model the global postbuckling analysis of one-dimensional and two-dimensional delaminations, is presented. In order to calculate the strain energy release rate, geometrically nonlinear analysis is accomplished, and the incremental crack closure technique is introduced. To check the effectiveness of the finite element models and the incremental crack closure technique, the simplified closed-form sloution for a through-the-width delamination with plane strain condition is derived and compared with the finite element result. The finite element results show good agreement with the closed-foul1 solutions. The present method was extended to calculate the strain energy release rate for two-dimensional delamination. For a symmetric circular delamination, the strain energy release rate shows great variation along the delamination front. and the delamination growth appears to occur perpendicular to the loading direction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.267-272
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• 1993

This paper presents the performance and problems in analysis method and testing system of Electronic Speckle Pattern Interferometry (ESPI) method, in measuring two-dimensional in-plane displacement. The anyalysis result of measurement by ESPI is quite comparable to that of measurement by strain gauge method. This implieds that the method of ESPI is a very effective tool in non-contact two-dimensional in-planc strain analysis. But there is a controversal point,measurment error. This error is discussed to be affected not by ESPI method itseif, but by its analysis scheme of the interference fringe,where the first-order interpolation has been applied to the points of strain measured. In this case, it is turned out that the more errors would be occured in the large interval of fringe. so, this paper describes a computer method for drawing when the height is available only for some arbitary collection of points, the method is based on a distance-weighted, least-squares approximation technique, with the weight varying with the distance of the data points.

• Journal of the Korean Society for Railway
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• v.7 no.2
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• pp.85-92
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• 2004

This paper consists of two parts. One is finite element analysis of the redistribution of residual stresses of weld specimen by cutting. This work is necessary to predict the actual residual stress distribution of weld specimens used in fatigue test. The other subject is to calculate the relaxation of residual stress and the strain field induced by cyclic loading. To obtain fatigue life of weldment, the value of strain amplitude at each position is necessary, for example in the strain-life approach, and the numerical results can be used to verify experimental strain measurements. Thermo mechanical finite element analyses were conducted on the commercial package ABAQUS.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.889-894
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• 2005

A modeling method for the modal analysis of cantilever plates undergoing in-plane translational acceleration is presented in this paper. Cartesian deformation variables are employed to derive the equations of motion and the resulting equations are transformed into dimensionless forms. To obtain the modal equation from the equations of motion, the in-plane equilibrium strain measures are substituted into the strain energy expression based on Von Karman strain measures. The effects of two dimensionless parameters (related to acceleration and aspect ratio) on the modal characteristics of accelerated plates are investigated through numerical studies.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.713-716
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• 2002

The dimensional accuracy of the cold forged products is strongly dependent on the elastic behavior of the die. The elastic deformation of the die is continuously changed during the process. Therefore, it is needed to measure the deformation of die. Strain gauges are used to measure the elastic strains in the die during cold backward extrusion process. The strain gauges are attached on the die surface and embedded at the interface between the die insert and the stress ring. In order to compare the results with the FE-analysis, the rigid-plastic FE-analysis of cold backward extrusion process using DEFORM-3D has been performed, and the analysis of elastic deformation of the die has been done by using ANSYS with non-linear contact.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.73-78
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• 2003

The residual stresses and. distortions of structures by welding exert negative effect on the safety of railroad structures. This investigation performs a thermal elasto-plastic analysis using finite element techniques to evaluate residual stresses in butted-welded joint. Considering this initial residual stresses, local stress and strain at the critical location (weld toe) during the loading were analyzed by elastic plastic finite element analysis. Fatigue crack initiation life and fatigue crack propagation life of butt-welded specimen were predicted by local strain approach and Neuber's role and Paris law. It is demonstrated that fatigue life estimates by local strain approach closely approximate the experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.186-192
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• 1993

Proto-type seismic isolation rubber bearings are investigated through nonlinear hyperelasticity finite elements using the ANSYS general purpose structural analysis code. The purpose of the analysis was to determine the maximum horizontal strain range which can be obtained with a 250KN hydraulic actuator. A Mooney-Rivlin strain energy density function was used as a constitutive law for rubber. The results are compared with the test data available in the literature and found to in good agreement only in the higy strain range. The analysis results can be used with conservatism to predict the necessary force required to a specified displacement such as the purpose of this analysis. However, more precise constitutive model will be required to simulate the bearing behavior with accuracy in the mid-range strain.

• Smart Structures and Systems
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• v.14 no.4
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• pp.679-697
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• 2014

The strain data acquired from structural health monitoring (SHM) systems play an important role in the state monitoring and damage identification of bridges. Due to the environmental complexity of civil structures, a better understanding of the actual strain data will help filling the gap between theoretical/laboratorial results and practical application. In the study, the multi-scale features of strain response are first revealed after abundant investigations on the actual data from two typical long-span bridges. Results show that, strain types at the three typical temporal scales of $10^5$, $10^2$ and $10^0$ sec are caused by temperature change, trains and heavy trucks, and have their respective cut-off frequency in the order of $10^{-2}$, $10^{-1}$ and $10^0$ Hz. Multi-resolution analysis and wavelet shrinkage are applied for separating and extracting these strain types. During the above process, two methods for determining thresholds are introduced. The excellent ability of wavelet transform on simultaneously time-frequency analysis leads to an effective information extraction. After extraction, the strain data will be compressed at an attractive ratio. This research may contribute to a further understanding of actual strain data of long-span bridges; also, the proposed extracting methodology is applicable on actual SHM systems.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.112-116
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• 2002

In cold forging, the elastic behavior of the die has a direct influence on the accuracy of the forging part. And the die dimension is continuously changed during the loading, unloading, and ejecting stage. In this paper, we evaluated the elastic deflections of cold forging die during loading, unloading, and ejecting stage. Uni-axial strain gauges are used to measure elastic strain of die during each forging stage. Strain gauges are attached on the surface of die. A commercial F.E.M code, DEFORM-2D$\^$TM/ is used to predict elastic strain of die. Two method of F.E.M. analysis are used to compare with measured and calculated elastic strain. One is to regard the die as rigid body over forging cycle. And then, the die sass is analyzed by loading the die with pressure from the forging part. The other is to regard the die as elastic body from forging cycle. The elastic strain of die is calculated and the die is elastically deformed at each strop. The calculated results under the elastic die assumption are well agreed with experimental data using strain gauges.