• Smart Structures and Systems
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• v.32 no.3
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• pp.153-166
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• 2023

Health monitoring of civil infrastructures, in particular, old bridges that are still in service, has become more than necessary, given the risk that a possible degradation or failure of these infrastructures can induce on the safety of users in addition to the resulting commercial and economic impact. Bridge integrity assessment has attracted significant research efforts over the past forty years with the aim of developing new damage identification methods applicable to real structures. The bridge of Ouled Mimoun (Tlemcen, Algeria) is one of the oldest railway structure in the country. It was built in 1889. This bridge, which is too low with respect to the level of the road, has suffered multiple shocks from various machines that caused considerable damage to its central part. The present work aims to analyze the stability of this bridge by identifying damages and evaluating the damage rate in different parts of the structure on the basis of a finite element model. The applied method is based on an inverse analysis of the normal stress responses that were calculated from the corresponding recorded strains, during the passage of a real train, by means of a set of strain gauges placed on certain elements of the bridge. The results obtained from the inverse analysis made it possible to successfully locate areas that were really damaged and to estimate the damage rate. These results were also used to detect an excessive rigidity in certain elements due to the presence of plates, which were neglected in the numerical reference model. In the case of the continuous bridge monitoring, this developed method will be a very powerful tool as a smart health monitoring system, allowing engineers to take in time decisions in the event of bridge damage.

• Analytical Science and Technology
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• v.9 no.2
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• pp.179-191
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• 1996

In order to understand the high temperature deformation behavior of superalloy 718, a rotating grade 718 alloy has been compression tested to about 0.7 upset ratio at $927{\sim}1066^{\circ}C$ temperature range and $5{\times}10^{-4}{\sim}5{\times}10^0sec^{-1}$ strain rate. The maximum flow stress was increased with increasing strain rate, and similar behavior was observed with decreasing temperature. At low temperature and high strain rates other than $5{\times}10^{-1}sec^{-1}$, strain softening was occurred mainly by dynamic recovery and deformation twinning processes, while at high temperature and low strain rates strain softening was offseted by dynamic recrystallization. At $5{\times}10^{-1}sec^{-1}$, strain hardening was occurred due to work hardening of the dynamic recrystallized grains. Strain rate sensitivity, m, was varied with strain rates. In the case of lower strain rate tests, m was measured as 0.3 and it was observed that the deformation was mainly controlled by dynamic recrystallization. At higher strain rate, m was lowered to 0.1 and the deformation was controlled by the dynamic recovery and the deformation twinning processes.

• Conservation Science in Museum
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• v.2
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• pp.57-68
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• 2000

This study is a scientific analysis of 12 bronze materials which were excavated from Sanoisa temple in Chongju. Analysis of crystalline shape, size and distribution of the each sample metal suggested that they can be classified as tableware(wrought), vessels for memorial service(casting) and bell bronze, which is the same result as classification based on elemental composition. Most of the tableware are forging wares with composition of 8:2:0 in Cu:Sn:Pb, and vessels for memorial service are casting wares whose composition is 7:1:2 in Cu:Sn:Pb, and bell bronze's composition is Cu:Sn:Pb = 85:10:5/9:1:0. The result clearly shows that composition is closely related with usage and manufacturing method of wares. Trace elements such as Co, Fe and As are the elements with high correlation coefficient with Cu, which means they exist as impurities in Cu, and the content of As showed an increase in the order of tableware, memorial service vessels and bell bronze. In addition, the analysis of lead isotope ratio showed that 3 bronze materials with high lead content were made from the lead coming from Japan and China. The composition of the solder was Cu:Sn:Pb = 83:12:5 where small Pb crystals were distributed evenly.