• Title/Summary/Keyword: Damage Function

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A Study on the Fatigue Strength of Lap Weld of LNG Tank (LNG탱크 겹침용접부의 피로강도에 관한 연구)

  • Kim, Jong-Ho
    • Journal of Ocean Engineering and Technology
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    • v.13 no.3 s.33
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    • pp.29-35
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    • 1999
  • At the design of Mark III membrane type LNG tank, an analytical and experimental approach on the fatigue strengths of membrane and its welds are very important in order to assist designers and surveyors. In this study, fatigue tests of lap weld of Mark III membrane type LNG tank were carried out and cumulative damage factor was calculated in order to estimate the fatigue life by probability density function and rule methods. It contained the following tests and reviews : 1) The fatigue tests of lap weld of stainless steel according to statistical testing method recommended by JSME, 2)Preparation of S-N curve for lap welds considering the statistical properties of the results of fatigue tests. 3) Procedure for estimating the initiation life of fatigue crack of lap welds under variable loads by the rule lf classification society and probability density function, 4) Guideline for inspection of lap welds fo membrane type LNG tank.

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Seismic performance of skewed highway bridges using analytical fragility function methodology

  • Bayat, M.;Daneshjoo, F.
    • Computers and Concrete
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    • v.16 no.5
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    • pp.723-740
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    • 2015
  • In this study, the seismic performance of skewed highway bridges has been assessed by using fragility function methodology. Incremental Dynamic Analysis (IDA) has been used to prepare complete information about the different damage states of a 30 degree skewed highway bridge. A three dimensional model of a skewed highway bridge is presented and incremental dynamic analysis has been applied. The details of the full nonlinear procedures have also been presented. Different spectral intensity measures are studied and the effects of the period on the fragility curves are shown in different figures. The efficiency, practicality and proficiency of these different spectral intensity measures are compared. A suite of 20 earthquake ground motions are considered for nonlinear time history analysis. It has been shown that, considering different intensity measures (IM) leads us to overestimate or low estimate the damage probability which has been discussed completely.

Effects of Differences Frequency of Repeated Transcranial Magnetic Stimulation Applied to the Less Affected Contralesional Corticomotor Area on Upper Extremity Function in Patients with Stroke (뇌졸중 환자의 비손상측 대뇌겉질 운동영역에 적용한 반복 경두개 자기자극의 빈도가 팔 기능에 미치는 영향 )

  • Ha-Na Kim;Sang-Mi Chung
    • Journal of The Korean Society of Integrative Medicine
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    • v.11 no.4
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    • pp.281-289
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    • 2023
  • Purpose : In this study, we aimed to determine how frequencies different of repetitive transcranial magnetic stimulation applied to the less affected contalesional corticomotor area affect upper extremity motor function in patients with acute stroke within 3 months of onset. By doing so, we aimed to propose a new method of rTMS intervention based on the degree of damage and recovery status of the patient, rather than the generalized rTMS intervention that has been used uniformly. Methods : The rTMS intervention was applied on the contralesional side of the cerebral hemisphere damage. 15 subjects in the HF-rTMS group, 12 subjects in the LF-rTMS group, and 14 subjects in the SF-rTMS group were randomized to receive the rTMS intervention in each group for a total of 10 sessions on five consecutive weekdays for two weeks, and underwent FMA-U to determine changes in upper extremity function following the intervention in each group. FMA-U was performed within 24 hours before and after the rTMS intervention. Results : When the FMA-U was performed to determine the pre- and post-intervention changes in upper extremity motor function within the groups, no statistically significant differences were found in the SF-rTMS group before and after the intervention, but significant statistical differences were found in the HF-rTMS group (p=.006) and the LF-rTMS group (p=.020), with greater significance in the HF-rTMS group than the LF-rTMS group. Conclusion : This study confirmed that compensatory action by activating the less affected contralesional corticomotor area based on the bimodal balance-recovery model can support upper extremity recovery patients with acute stroke within 3 months of onset, depending on the degree of damage level and recovery status. Therefore, the results of the contralesional HF-rTMS application in this study may provide a basis for proposing a new rTMS intervention for upper extremity recovery in stroke patients.

Safety of Herbal Medicines on Liver Function in Functional Dyspepsia Patients: A Single-Center Retrospective Study (기능성 소화불량 환자의 간 기능에 대한 한약 투여의 안전성: 단일 센터 후향적 연구)

  • Aram Han;Chang-Yul Keum;Chae-Rim Yoon;Su-Hyun Choi;Dahee Jeong;Nahyun Jeong;Hae-in Jeong;Na-Yeon Ha;Jinsung Kim
    • The Journal of Internal Korean Medicine
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    • v.44 no.4
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    • pp.635-644
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    • 2023
  • Objectives: This study analyzed laboratory serum data results before and after patients took herbal medicine to confirm the clinical safety of herbal medicine. In addition, in the event of liver damage, the case was analyzed to confirm the characteristics of liver damage and the possibility of liver damage caused by herbal medicine. Methods: A retrospective chart review of the effects of herbal medicine on liver function in patients diagnosed with functional dyspepsia was conducted. The electronic medical records of 128 patients in a single hospital were reviewed. Results: The statistical analysis revealed a statistically significant decrease in liver function-related laboratory serum data after taking herbal medicine (p<0.05). In addition, among 128 patients, there were two cases of drug-induced liver injury (DILI) (1.56%). Conclusion: Taking herbal medicine prescribed by experts does not significantly affect liver function in patients with functional dyspepsia. Rather, the liver levels of the subjects showed a significant decrease after taking herbal medicine. To support these results, further large-scale multicenter prospective studies are necessary.

Residual Longitudinal Strength of a VLCC Considering Probabilistic Damage Extents (확률론적 손상을 고려한 VLCC 잔류 종강도 평가)

  • Nam, Ji-Myung;Choung, Joon-Mo;Park, Ro-Sik
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.2
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    • pp.124-131
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    • 2012
  • This paper provides prediction of ultimate longitudinal strengths of hull girder of a VLCC considering probabilistic damage extents due to collision and grounding accidents based on IMO Guideline(2003). The probability density functions of damage extents are expressed as a function of nondimensional damage variables. The accumulated probability levels of 10%, 30%, 50%, and 70% are taken into account for the damage extent estimation. The ultimate strengths have been calculated using in-house software UMADS (Ultimate Moment Analysis of Damaged Ships) which is based on the progressive collapse method. Damage indices are provided for all heeling angles due to any possible flooding of compartments from $0^{\circ}$ to $180^{\circ}$ which represent from sagging to hogging conditions, respectively. The analysis results reveal that minimum damage indices show different values according to heeling angles and damage levels.

Identification of the Structural Damages in a Cylindrical Shell (원통형 셸에 발생한 구조손상의 규명)

  • Kim, Sung-Hwan;Lee, U-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.12 s.243
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    • pp.1586-1596
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    • 2005
  • In this paper, a structural damage identification method (SDIM) is developed to identify the line crack-like directional damages generated within a cylindrical shell. First, the equations of motion for a damaged cylindrical shell are derived. Based on a theory of continuum damage mechanics, a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness, which is dependent of the size and the orientation of the damage with respect to the global coordinates. The present SDIM is then derived from the frequency response function (FRF) directly solved from the equations of motion of a damaged shell. In contrast with most existing SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM may require only the FRF-data measured at damaged state. By virtue of utilizing FRF-data, one may choose as many sets of excitation frequency and FRF measurement point as needed to acquire a sufficient number of equations for damage identification analysis. The numerically simulated damage identification tests are conducted to study the feasibility of the present SDIM.

Residual ultimate strength of a very large crude carrier considering probabilistic damage extents

  • Choung, Joonmo;Nam, Ji-Myung;Tayyar, Gokhan Tansel
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.6 no.1
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    • pp.14-26
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    • 2014
  • This paper provides the prediction of ultimate longitudinal strengths of the hull girders of a very large crude carrier considering probabilistic damage extent due to collision and grounding accidents based on IMO Guidelines (2003). The probabilistic density functions of damage extent are expressed as a function of non-dimensional damage variables. The accumulated probabilistic levels of 10%, 30%, 50%, and 70% are taken into account for the estimation of damage extent. The ultimate strengths have been calculated using the in-house software called Ultimate Moment Analysis of Damaged Ships which is based on the progressive collapse method, with a new convergence criterion of force vector equilibrium. Damage indices are provided for several probable heeling angles from $0^{\circ}$ (sagging) to $180^{\circ}$ (hogging) due to collision- and grounding-induced structural failures and consequent flooding of compartments. This paper proves from the residual strength analyses that the second moment of area of a damage section can be a reliable index for the estimation of the residual ultimate strength. A simple polynomial formula is also proposed based on minimum residual ultimate strengths.

A combined experimental and numerical study on the plastic damage in microalloyed Q345 steels

  • Li, Bin;Mi, Changwen
    • Structural Engineering and Mechanics
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    • v.72 no.3
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    • pp.313-327
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    • 2019
  • Damage evolution in the form of void nucleation, propagation and coalescence is the primary cause that is responsible for the ductile failure of microalloyed steels. The Gurson-Tvergaard-Needleman (GTN) damage model has proven to be extremely robust for characterizing the microscopic damage behavior of ductile metals. Nonetheless, successful applications of the model on a given metal type are limited by the correct identification of damage parameters as well as the validation of the calculated void growth rate. The purpose of this study is two-fold. First, we aim to identify the damage parameters of the GTN model for Q345 steel (Chinese code), due to its extensive application in mechanical and civil industries in China. The identification of damage parameters is facilitated by the well-suited response surface methodology, followed by a complete analysis of variance for evaluating the statistical significance of the identified model. Second, taking notched Q345 cylinders as an example, finite element simulations implemented with the identified GTN model are performed in order to analyze their microscopic damage behavior. In particular, the void growth rate predicted from the simulations is successfully correlated with experimentally measured acoustic emissions. The quantitative correlation suggests that during the yielding stage the void growth rate increases linearly with the acoustic emissions, while in the strain-hardening and softening period the dependence becomes an exponential function. The combined experimental and finite element approach provides a means for validating simulated void growth rate against experimental measurements of acoustic emissions in microalloyed steels.

Effect of creep-fatigue interaction on high temperature low cycle fatigue strength and fracture behavior of STS 316 stainless steels (STS 316鋼 의 高溫低사이클 疲勞强度 와 破壞擧動 에 미치는 크리이프 - 疲勞 相互作용 의 影響)

  • 오세욱;이규용;김중완;문무경
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.2
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    • pp.140-149
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    • 1985
  • Fully reversed push-pull low cycle fatigue tests under strain control of trapezoid cyclic mode have been conducted in air at temperature of 550.deg. C and with frequency of 0.5 cpm on the domestic stainless steel STS 316 after solution treatment for 1 hour at 1100.deg. C. As an experimental equipment for high temperature fatigue tests, an electric servo-hydraulic fatigue machine(Instron model 1350) was used. This paper presents the effects of creep hold time and plastic strain range on push-pull high temperature low cycle fatigue life and fracture behavior. The fracture surfaces were observed by means of the scanning electron microscope. The results are as follows. (1) The fatigue life decreases with increase of the plastic strain range equal hold time and also decreases as the hold time is getting longer. (2) The frequency modified damage function can predict fatigue life by incorporating a variation of Coffin's frequency modified approach into damage function. (3) The ratios of creep damage and fatigue damage can be calculated by using he linear accumulation damage concept and the ratio of creep damage increases as the hold time is getting longer. (4) At the creep hold time of 5 minutes and the strain range of 2.0%, the fracture mode was intergranular fracture and striations were hardly observed. In this case, the intergranular cracking was originated in void type('.gamma.' type) cracking.

Preliminary Analysis of Climate Change Damage in Korea Using the PAGE Model (PAGE 모델을 이용한 한국 기후변화의 피해비용 분석)

  • Chae, Yeo-Ra
    • Journal of Environmental Policy
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    • v.9 no.1
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    • pp.31-55
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    • 2010
  • This study aims to estimate potential climate change damage in Korea using the PAGE model. This study reviewed previous a reasearch to compare relative sensitivity to climate change in Korea and other regions to generate climate change damage function. It was found that sensitivity to climate change in Korea is similar to other Organization for Economic Cooperation and Development (OECD) countries. This study estimated climate change impact for three scenarios. If no action is taken, climate change damage cost in Korea could reach US$ 12,928 ~ 57,900 M. Cumulative Net Present Value (NPV)of climate change impact from 1990 to 2100 would be between US$ 143,226 ~ 921,701 Mdepending on emission scenarios. However, this result should be interpreted with caution as it draws its damage function based on only a few available references. Results also showed that an adaptation policy could decrease the degree of climate change impact significantly. If an adaptation policy is implemented, climate change impact will be decreased by US$ 11,355 million dollars in Korea in 2100.

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