• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.126-129
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• 2005

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive continuous indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model. The residual stress from the indentation method was compared with that from the saw-cutting method.

• Earthquakes and Structures
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• v.25 no.1
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• pp.15-26
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• 2023

It is of great importance to assess the residual displacement demand in the performance-based seismic design. In this paper, a hybrid deep learning model for predicting the residual displacement spectra under near-fault (NF) ground motions is proposed by combining the long short-term memory network (LSTM) and back-propagation (BP) network. The model is featured by its capacity of predicting the residual displacement spectrum under a given NF ground motion while considering the effects of structural parameters. To construct this model, 315 natural and artificial NF ground motions were employed to compute the residual displacement spectra through elastoplastic time history analysis considering different structural parameters. Based on the resulted dataset with a total of 9,450 samples, the proposed model was finally trained and tested. The results show that the proposed model has a satisfactory accuracy as well as a high efficiency in predicting residual displacement spectra under given NF ground motions while considering the impacts of structural parameters.

• Steel and Composite Structures
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• v.25 no.5
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• pp.617-624
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• 2017

In this study, a new empirical method is presented to obtain Dynamic Increase Factor (DIF) in nonlinear static analysis of structures against sudden removal of a gravity load-bearing element. In this method, DIF is defined as a function of minimum ratio of difference between maximum moment capacity ($M_u$) and moment demand ($M_d$) to plastic moment capacity ($M_p$) under unamplified gravity loads of elements. This function determines the residual strength of a damaged building before amplified gravity loads. For each column removal location, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived, which correspond to the ratio min $[(M_u-M_d)/M_p]$ of beams in the bays immediately adjacent to the removed column, and at all floors above it. Therefore, the new DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of a moment frame structure. The proposed DIF formulas can estimate the real residual strength of a structure based on critical member.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.579-580
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• 2006

In this study, an injection mold of tensile test specimen was manufactured by international standard. Pressure and temperature in the cavity of the injection mold was measured by sensors. Simulation of injection molding process was performed with the same condition of experiment and linear structural tensile analysis was also performed with the initial condition of the residual stress induced by injection molding analysis. Normalized elastic coefficient of tensile test was compared with that of structural analysis. It was shown that the residual stress induced by injection molding has an effect on both the experiment of tensile test and linear structural analysis.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.71-78
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• 2014

Although the fatigue design curve of ASME Code has enough margin with respect to alternating stress and cycles, the welding residual stress(WRS) should be included in fatigue analysis. In this paper, WRS distribution in a nozzle with dissimilar metal weldment was obtained by finite element analysis and was added in fatigue analysis. The fatigue analysis was performed by following the ASME Code including thermal and stress analysis applying with postulated 30 transient conditions. The calculated results of a cumulative fatigue usage factors(CUF) were compared for the case of the models with or without WRS effects. The results showed that the CUF at weldment and heat affected zone was affected by the WRS.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.126-129
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• 2001

LIPCA (LIghtweight Piezo-composite Curved Actuator) is an actuator device which is lighter than other conventional piezoelectric ceramic type actuator. LIPCA is composed of a piezoelectric ceramic layer and fiber reinforced light composite layers, typically a PZT ceramic layer is sandwiched by a top fiber layer with low CTE (coefficient of thermal expansion) and base layers with high CTE. LIPCA has curved shape like a typical THUNDER (thin-layer composite unimorph feroelectric driver and sensor), but it is lighter an than THUNDER. Since the curved shape of LIPCA is from the thermal deformation during the manufacturing process of unsymmetrically laminated lay-up structure, an analysis for the thermal deformation and residual stresses induced during the manufacturing process is very important for an optimal design to increase the performance of LIPCA. To investigate the thermal deformation behavior and the induced residual stresses of LIPCA at room temperature, the curvatures of LIPCA were measured and compared with those predicted from the analysis using the classical lamination theory. A methodology is being studied to find an optimal stacking sequence and geometry of LIPCA to have larger specific actuating displacement and higher force. The residual stresses induced during the cooling process of the piezo-composite actuators have been calculated. A lay-up geometry for the PZT ceramic layer to have compression stress in the geometrical principal direction has been designed.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.218-223
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• 2000

The shot peening is largely used for a surface treatment in which small spherical parts called shots are blasted on a surface of a metallic components with velocities up to 100m/s. This treatment leads to an improvement of fatigue behavior due to the developed compressive residual stresses, and so it has gained widespread acceptance in the automobile and aerospace industries. The residual stress profile on surface layer depends on the parameters of shot peening, which are, shot velocity, shot diameter, coverage, impact angle, material properties etc. and the method to confirm this profile is only measurement by X-ray diffractometer. Despite its importance to automobile and aerospace industries, little attention has been devoted to the accurate modelling of the process. In this paper, the simulation technique is applied to predict the magnitude and distribution of the residual stress and plastic deformation caused by shot peening with the help of the finite element analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.6
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• pp.35-45
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• 2008

To investigate the effects of residual displacement, the structural responses of buckling-restrained braced frames (BRBF) and special moment-resisting frames (SMRF) were evaluated for design-based excitations following an application of initial residual drift. The initial residual drift was applied to the structure in two ways. The first way was to simply apply the same earthquake record to the structure twice, with an appropriate pause between applications to allow the structural response from the first record to return to zero. The second way to apply the initial residual drift was to apply a pushover to the structure until it arrives at the desired residual drift value. According to the analysis results, the initial residual drifts had a significant effect on the responses of steel BRBF and SMRF. The responses of BRBF were more highly dependent on the initial residual deformation than the responses of SMRF. Therefore, in order to minimize the post-event repair cost, a reduction of residual drift is required.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.12
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• pp.1116-1123
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• 2015

The lifetime of a geostationary satellite depends on the residual propellant amount and therefore the precise residual propellant gauging is very important for the mitigation of economic loss arised from premature removal of satellite from its orbit, satellites replacement planning, slot management and so on. In this paper, the thermal mass method and its uncertainty are described. The residual propellant analysis of a geostationary satellite is simulated based on the KOREASAT data and the uncertainty of thermal mass method is calculated by using the Monte Carlo method. The results of this study show the importance parameter of estimation residual propellant using the thermal mass method.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.3
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• pp.631-635
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• 2001

The major problems associated with the manufacturing processes of the microaccelerometer based on the tunneling current concept is the residual stress. This paper deals with finite element analysis of residual stress causing pop up phenomenon which are induced in micromachining processes for a microaccelerometers sensor using silicon on insulator(SOI) wafer. After heating the tunnel gap up to $100^{\circ}C$and get it through cooling process and the additional beam up to $80^{\circ}C$get it through the cooling process. We learn the residual stress of each shape and compare the results with each other, after heating the tunnel gap up to $400^{\circ}Cduring$ the Pt deposition process. The equivalent stresses produced during the heating process of focused ion beam(FIB) cut was also to be about $0.02~0.25Pa/^{\circ}C$and cooling process the gradient of residual stresses of about $8.4\{times}10^2Pa/{\mu}m$ still at cantilever beam and connected part of paddle. We want to seek after the real cause of this pop up phenomenon and diminish this by change manufacturing processes of microaccelerometer sensors.