• Title/Summary/Keyword: sensitivity to damage

Search Result 487, Processing Time 0.023 seconds

Localized failure in damage dynamics

  • Do, Xuan Nam;Ibrahimbegovic, Adnan;Brancherie, Delphine
    • Coupled systems mechanics
    • /
    • v.4 no.3
    • /
    • pp.211-235
    • /
    • 2015
  • In this work we present a one-dimensional damage model capable of representing the dynamic fracture for elastodamage bar with combined hardening in fracture process zone - FPZ and softening with embedded strong discontinuities. This model is compared with another one we recently introduced (Do et al. 2015) and it shows a good agreement between two models. Namely, it is indicated that strain-softening leads to a sensitivity of results on the mesh discretization. Strain tends to localization in a single element which is the smallest possible area in the finite element simulations. The strain-softening element in the middle of the bar undergoes intense deformation. Strain increases with increasing mesh refinement. Strain in elements outside the strain-softening element gradually decreases to zero.

A Study on the Analysis of Lightning Damage Impact in Domestic Offshore Wind Farm (국내 해상풍력발전단지 낙뢰피해 영향 분석에 관한 연구)

  • Seo, Jin-Gyu;Kim, Kyu-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.65 no.2
    • /
    • pp.247-252
    • /
    • 2016
  • The latest offshore wind turbines are easily exposed to lightning strikes because they are designed with longer blades and taller height to satisfy the growing capacity demands. The generation facilities and elements of the offshore wind farm are more vulnerable to lightning damage because of more severe, unpredictable weather conditions. Therefore, this paper presents the analysis of measure for lightning overvoltage mitigation in offshore wind farm planned in South Korea southwest seashore. The sensitivity analysis includes the steady state and transient state characteristics of offshore wind farm and proposes the countermeasure for mitigation of transient overvoltage by considering earth resistivity of the offshore environment.

Electrochemical and Cavitation-Erosion Characteristics of Duplex Stainless Steels in Seawater Environment (해수 환경에서 듀플렉스 스테인리스강의 전기화학적 거동 및 캐비테이션 특성)

  • Heo, Ho-Seong;Kim, Seong-Jong
    • Corrosion Science and Technology
    • /
    • v.20 no.6
    • /
    • pp.466-474
    • /
    • 2021
  • A wet type scrubber for merchant vessel uses super austenitic stainless steels with pitting resistance equivalent number (PREN) of 40 or higher for operation in a harsh corrosive environment. However, it is expensive due to a high nickel content. Thus, electrochemical behavior and cavitation erosion characteristics of UNS S32750 as an alternative material were investigated. Microstructure analysis revealed fractions of ferritic and austenitic phases of 48% and 52%, respectively, confirming the existence of ferritic matrix and austenitic island. Potentiodynamic polarization test revealed damage at the interface of the two phases because of galvanic corrosion due to different chemical compositions of ferritic and austenitic phases. After a cavitation test, a compressive residual stress was formed on the material surface due to impact pressure of cavity. Surface hardness was improved by water cavitation peening effect. Hardness value was the highest at 30 ㎛ amplitude. Scanning electron microscopy revealed wave patterns due to plastic deformation caused by impact pressure of the cavity. The depth of surface damage increased with amplitude. Cavitation test revealed larger damage caused by erosion in the ferritic phase due to brittle fracture derived from different strain rate sensitivity index of FCC and BCC structures.

A practical modification to coaxial cables as damage sensor with TDR in obscured structural members and RC piles

  • Mehmet Ozgur;Sami Arsoy
    • Structural Monitoring and Maintenance
    • /
    • v.10 no.2
    • /
    • pp.133-154
    • /
    • 2023
  • Obscured structural members are mostly under-evaluated during condition assessment due to lack of visual inspection capability. Insufficient information about the integrity of these structural members poses a significant risk for public safety. Time domain reflectometry (TDR) is a novel approach in structural health monitoring (SHM). Ordinary coaxial cables "as is" without a major modification are not suitable for SHM with TDR. The objective of this study is to propose a practical and cost-effective modification approach to commercially available coaxial cables in order to use them as a "cable sensor" for damage detection with the TDR equipment for obscured structural members. The experimental validation and assessment of the proposed modification approach was achieved by conducting 3-point bending tests of the model piles as a representative obscured structural member. It can be noted that the RG59/U-6 and RG6/U-4 cable sensors expose higher strain sensitivity in comparison with non-modified "as is" versions of the cables used. As a result, the cable sensors have the capability of sensing both the presence and the location of a structural damage with a maximum aberration of 3 cm. Furthermore, the crack development can be monitored by the RG59/U-6 cable sensor with a simple calibration.

Derivation of analytical fragility curves using SDOF models of masonry structures in Erzincan (Turkey)

  • Karimzadeh, Shaghayegh;Kadas, Koray;Askan, Aysegul;Erberik, M. Altug;Yakut, Ahmet
    • Earthquakes and Structures
    • /
    • v.18 no.2
    • /
    • pp.249-261
    • /
    • 2020
  • Seismic loss estimation studies require fragility curves which are usually derived using ground motion datasets. Ground motion records can be either in the form of recorded or simulated time histories compatible with regional seismicity. The main purpose of this study is to investigate the use of alternative ground motion datasets (simulated and real) on the fragility curves. Simulated dataset is prepared considering regional seismicity parameters corresponding to Erzincan using the stochastic finite-fault technique. In addition, regionally compatible records are chosen from the NGA-West2 ground motion database to form the real dataset. The paper additionally studies the effects of hazard variability and two different fragility curve derivation approaches on the generated fragility curves. As the final step for verification purposes, damage states estimated for the fragility curves derived using alternative approaches are compared with the observed damage levels from the 1992 Erzincan (Turkey) earthquake (Mw=6.6). In order to accomplish all these steps, a set of representative masonry buildings from Erzincan region are analyzed using simplified structural models. The results reveal that regionally simulated ground motions can be used alternatively in fragility analyses and damage estimation studies.

Damage detction and characterization using EMI technique under varying axial load

  • Lim, Yee Yan;Soh, Chee Kiong
    • Smart Structures and Systems
    • /
    • v.11 no.4
    • /
    • pp.349-364
    • /
    • 2013
  • Recently, researchers in the field of structural health monitoring (SHM) have been rigorously striving to replace the conventional NDE techniques with the smart material based SHM techniques, employing smart materials such as piezoelectric materials. For instance, the electromechanical impedance (EMI) technique employing piezo-impedance (lead zirconate titanate, PZT) transducer is known for its sensitivity in detecting local damage. For practical applications, various external factors such as fluctuations of temperature and loading, affecting the effectiveness of the EMI technique ought to be understood and compensated. This paper aims at investigating the damage monitoring capability of EMI technique in the presence of axial stress with fixed boundary condition. A compensation technique using effective frequency shift (EFS) by cross-correlation analysis was incorporated to compensate the effect of loading and boundary stiffening. Experimental tests were conducted by inducing damages on lab-sized aluminium beams in the presence of tensile and compressive forces. Two types of damages, crack propagation and bolts loosening were simulated. With EFS for compensation, both cross-correlation coefficient (CC) index and reduction in peak frequency were found to be efficient in characterizing damages in the presence of varying axial loading.

An Assessment Pipe Damage Probability of High Pressure Underground Pipeline in Industrial Estate (산업단지 고압매설배관의 손상확률 평가)

  • Kim, jin-jun;Rhie, Kwang-Won;Choi, hun-ung;Choi, ji-hun
    • Journal of the Korean Institute of Gas
    • /
    • v.23 no.2
    • /
    • pp.9-16
    • /
    • 2019
  • The frequency of major accidents which has probability of occurrence at the high pressure underground pipeline of industrial estate such an Ulsan, Yeo-ju by the other construction such as an excavation work will be compared to city gas underground pipeline to derive the basic event by the FTA and present. Also, Observe and analyze the pipe damage impact factor such as an excavation frequency, patrol cycle. As a result, It contributes to the safety improvement of high pressure gas buried pipeline due to obtain importance and sensitivity of the pipe damge impact factors.

Effect of DPBll Gene for the Transcriptional Induction by DNA Damage During Cell Cycle in Saccharomyces cerevisiae (출아효모의 세포주기동안 DNA 상해에 의한 발현 유도에 미치는 DPB11 유전자의 영향)

  • 선우양일;임선희;배호정;김중현;김은아;김승일;김수현;박정은;김재우
    • Korean Journal of Microbiology
    • /
    • v.38 no.2
    • /
    • pp.96-102
    • /
    • 2002
  • The S-phase checkpoint mechanisms response to DNA damage or inhibition of DNA replication for maintenance of genetic stability in eukaryotic cells. These roles include cell cycle control arrest at S-phase and Iranscriptional induction of repair genes. To characterize the defects of dpbll mutant for both these responses, we examined the over-expression effect of DPBll gene, the sensitivity to HU, MMS, and the transcriptional pattern by DNA damage agent for RNRS mRNA. RNRS transcript is induced in response to a wide variety of agents that either damage D7A directly through chemical modification or induce stress by blocking DNA synthesis. As results, dpbll-1 cells are sensitive to DNA damage agents and the level of RNR3 mRNA is reduced approximately 40% than wild type cells. Moreover, we found the same results in dpb2-1 cells. Therefore, we propose that DPB2 and DPBll act as a sensor of replication that coordinates the transcriptional and cell cycle responses to replication blocks.

Power spectral density method performance in detecting damages by chloride attack on coastal RC bridge

  • Mehrdad, Hadizadeh-Bazaz;Ignacio J., Navarro;Victor, Yepes
    • Structural Engineering and Mechanics
    • /
    • v.85 no.2
    • /
    • pp.197-206
    • /
    • 2023
  • The deterioration caused by chloride penetration and carbonation plays a significant role in a concrete structure in a marine environment. The chloride corrosion in some marine concrete structures is invisible but can be dangerous in a sudden collapse. Therefore, as a novelty, this research investigates the ability of a non-destructive damage detection method named the Power Spectral Density (PSD) to diagnose damages caused only by chloride ions in concrete structures. Furthermore, the accuracy of this method in estimating the amount of annual damage caused by chloride in various parts and positions exposed to seawater was investigated. For this purpose, the RC Arosa bridge in Spain, which connects the island to the mainland via seawater, was numerically modeled and analyzed. As the first step, each element's bridge position was calculated, along with the chloride corrosion percentage in the reinforcements. The next step predicted the existence, location, and timing of damage to the entire concrete part of the bridge based on the amount of rebar corrosion each year. The PSD method was used to monitor the annual loss of reinforcement cross-section area, changes in dynamic characteristics such as stiffness and mass, and each year of the bridge structure's life using sensitivity equations and the linear least squares algorithm. This study showed that using different approaches to the PSD method based on rebar chloride corrosion and assuming 10% errors in software analysis can help predict the location and almost exact amount of damage zones over time.

Health Vulnerability Assessment for PM10 in Busan (부산지역 미세먼지에 대한 건강 취약성 평가)

  • Lee, Won-Jung;Hwang, Mi-Kyoung;Kim, Yoo-Keun
    • Journal of Environmental Health Sciences
    • /
    • v.40 no.5
    • /
    • pp.355-366
    • /
    • 2014
  • Objectives: This study seeks to evaluate the vulnerability assessment of the human health sector for $PM_{10}$, which is reflected in the regional characteristics and related disease mortality rates for $PM_{10}$ in Busan over the period of 2006-2010. Methods: According to the vulnerability concept suggested by the Intergovernmental Panel on Climate Change (IPCC), vulnerability to $PM_{10}$ is comprised of the categories of exposure, sensitivity, and adaptive capacity. The indexes of the exposure and sensitivity categories indicate positive effects, while the adaptive capacity index indicates a negative effect on vulnerability to $PM_{10}$. Variables of each category were standardized by the rescaling method, and each regional relative vulnerability was computed through the vulnerability index calculation formula. Results: The regions with a high exposure index are Jung-Gu (transportation region) and Saha-Gu (industrial region). Major factors determining the exposure index are the $PM_{10}$ concentration, days of $PM_{10}{\geq}50$, ${\mu}g/m^3$, and $PM_{10}$ emissions. The regions that show a high sensitivity index are urban and rural regions; these commonly have a high mortality rate for related disease and vulnerable populations. The regions that have a high adaptive capacity index are Jung-Gu, Gangseo-Gu, and Busanjin-Gu, all of which have a high level of economic/welfare/health care factors. The high-vulnerability synthesis of the exposure, sensitivity, and adaptive capacity indexes show that Dong-Gu and Seo-Gu have a risk for $PM_{10}$ potential effects and a low adaptive capacity. Conclusions: This study presents the vulnerability index to $PM_{10}$ through a relative comparison using quantitative evaluation to draw regional priorities. Therefore, it provides basic data to reflect environmental health influences in favor of an adaptive policy limiting damage to human health caused by vulnerability to $PM_{10}$.