• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집A
• /
• pp.635-640
• /
• 2001

This paper introduces a frequency-domain method of structural damage identification. It is formulated in a general form from the dynamic stiffness equation of motion for a structure and then applied to a beam structure. The appealing features of the present damage identification method are: (1) it requires only the frequency response functions experimentally measured from damaged structure as the input data, and (2) it can locate and quantify many local damages at the same time. The feasibility of the present damage identification method is tested through some numerically simulated damage identification analyses and then experimental verification is conducted for a cantilevered beam with damage caused by introducing three slots.

• Smart Structures and Systems
• /
• 제22권6호
• /
• pp.699-709
• /
• 2018

With increasing traffic volumes and rising vehicle traffic, especially in cities, the number of pedestrian bridges has also increased significantly. Like all other structures, pedestrian bridges also suffer damage. In order to increase the safety of pedestrians, it is necessary to identify existing damage and to repair them to ensure the safety of the bridge structures. Owing to the shortcomings of local methods in identifying damage and in order to enhance the reliability of detection and identification of structural faults, signal methods have seen significant development in recent years. In this research, a new methodology, based on cone-shaped kernel distribution with a new damage index, has been used for damage detection in pedestrian truss bridges. To evaluate the proposed method, the numerical models of the Warren Type steel truss and the Arregar steel footbridge were used. Based on the results, the proposed method and damage index identified the damage and determined its location with a high degree of precision. Given the ease of use, the proposed method can be used to identify faults in pedestrian bridges.

• 한국산학기술학회논문지
• /
• 제18권4호
• /
• pp.685-693
• /
• 2017

본 연구는 인구와 주요시설들이 집중되어 있는 도시지역에 국지성 폭우가 발생했을 경우, 용도지역별로 침수 피해에 대한 위험도를 등급화하여 효율적으로 대처하기 위해 연구하였다. 창원시를 대상으로 토지이용의 제도적 기반이 되는 용도지역과 재산 가치를 추정할 수 있는 공시지가, 그리고 건축물의 피해 면적과 밀도를 추정하기 위한 용적률 등에 대한 자료를 확보하여 Fuzzy모형을 통해 동일한 침수면적이 발생했을 경우 사회 경제적 피해에 대한 민감도를 파악함으로써 용도지역별로 피해 정도를 위험등급화를 하였다. 분석결과 창원시의 5개 구(마산합포구, 마산회원구, 성산구, 의창구, 진해구)에서 용도지역별 침수피해 순위는 상업지역, 주거지역, 공업지역, 녹지지역 순으로 동일하게 나타났으며, 이는 상업지역이 공시지가와 용적률이 가장 높아 침수 피해에 대한 재산 피해가 높기 때문으로 판단된다. 하지만 마산회원구와 성산구의 세부적인 분석결과에서 앞선 결과와는 상이한 것을 볼 수 있었는데, 지역의 환경 및 특성에 따라 용도지역별로도 침수위험등급이 달라질 수 있음을 보여주고 있다. 본 연구에서 도출된 결과물은 향후 도시계획과 연계하여 토지이용계획 수립 시 도시 침수피해를 줄이기 위한 기초 자료로 활용될 수 있을 뿐 아니라, 도시 지역 개발 계획 수립 시 침수 피해 정도를 사전에 예측할 수 있다. 또한, 기후변화와 도시화라는 이슈와 함께 폭우 발생 시 도시 내수침수 저감에 기여하기 위한 대책으로 토지이용 부문이라는 새로운 대책을 제시했다는 점에서 큰 의의가 있다고 할 수 있다.

• Journal of Dental Anesthesia and Pain Medicine
• /
• 제20권2호
• /
• pp.55-61
• /
• 2020

During dental treatment, a dentist usually applies the local anesthesia. Therefore, all dentists should have expertise in local anesthesia and anesthetics. Local anesthetics have a neurotoxic effect at clinically relevant concentrations. Many studies have investigated the mechanism of neurotoxicity of local anesthetics but the precise mechanism of local anesthetic-induced neurotoxicity is still unclear. In addition, it is difficult to demonstrate the direct neurotoxic effect of local anesthetics because perioperative nerve damage is influenced by various factors, such as the anesthetic, the patient, and surgical risk factors. This review summarizes knowledge about the pharmacology of local anesthetics, nerve anatomy, and the incidence, risk factors, and possible cellular mechanisms of local anesthetic-induced neurotoxicity.

• Smart Structures and Systems
• /
• 제11권2호
• /
• pp.217-240
• /
• 2013

In this paper, practical methods to utilize PZT's dual piezoelectric effects (i.e., dynamic strain and electro-mechanical (E/M) impedance responses) for damage detection in beam-type structures are presented. In order to achieve the objective, the following approaches are implemented. Firstly, PZT material's dual piezoelectric characteristics on dynamic strain and E/M impedance are investigated. Secondly, global vibration-based and local impedance-based methods to detect the occurrence and the location of damage are presented. Finally, the vibration-based and impedance-based damage detection methods using the dual piezoelectric responses are evaluated from experiments on a lab-scaled beam for several damage scenarios. Damage detection results from using PZT sensor are compared with those obtained from using accelerometer and electric strain gauge.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1998년도 춘계학술대회논문집
• /
• pp.220-223
• /
• 1998

The failure of die often occurs as a result of growth of microcracks - referred as a brittle damage. In this study, an analysis of brittle damage evolution cupled with elastic finite element analysis of die deformation is presented. A local transformation from the tractions of a workpiece mesh to those of a die mesh is developed. The brittle damage is defined as a vector considering the shape of common microcracks in the brittle metals and the damage function suggested by Krajcinovic is utillized. Applications of the proposed model to modeling damage evolution in the extrusion die and forging die are given and the characteristics of brittle damage evolution in die are in detail examined.

• Structural Engineering and Mechanics
• /
• 제63권2호
• /
• pp.251-257
• /
• 2017

A local damage identification method using measured structural static displacement is proposed in this study. Based on the residual force vector deduced from the static equilibrium equation, residual strain energy (RSE) is introduced, which can localize the damage in the element level. In the case of all the nodal displacements are used, the RSE can localize the true location of damage, while incomplete displacement measurements are used, some suspicious damaged elements can be found. A model updating method based on static displacement response sensitivity analysis is further utilized for accurate identification of damage location and extent. The proposed method is verified by two numerical examples. The results indicate that the proposed method is efficient for damage identification. The advantage of the proposed method is that only limited static displacement measurements are needed in the identification, thus it is easy for engineering application.

• Journal of Mechanical Science and Technology
• /
• 제18권12호
• /
• pp.2114-2124
• /
• 2004

In this paper, a structural damage identification method (SDIM) is developed for cylindrical shells and the numerically simulated damage identification tests are conducted to study the feasibility of the proposed SDIM. The SDIM is derived from the frequency response function solved from the structural dynamic equations of damaged cylindrical shells. A damage distribution function is used to represent the distribution and magnitudes of the local damages within a cylindrical shell. In contrast with most existing modal parameters-based SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM requires only the FRF-data measured in the damaged state. By virtue of utilizing FRF-data, one is able to make the inverse problem of damage identification well-posed by choosing as many sets of excitation frequency and FRF measurement point as needed to obtain a sufficient number of equations.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.90-95
• /
• 2003

Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. In pipes of energy plants, sometimes, the local wall thinning may result from severe erosion-corrosion (E/C) damage. However, the effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale welded and unwelded carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. The observed failure modes were divided into four types; ovalization, crack initiation/growth after ovalization, local buckling and crack initiation/growth after local buckling. Also, the strengths of welded and unwelded piping system with local wall thinning were evaluated.

• 대한치과마취과학회지
• /
• 제13권3호
• /
• pp.71-79
• /
• 2013

Local pain management is the most critical aspect of patient care in dentistry. Local anesthesia is a reversible blockade of nerve conduction in an applied area that produces loss of sensation. The chemical agents used to produce local anesthesia stabilize neuronal membranes by inhibiting the ionic fluxes required for the propagation of neural impulses. Proper local anesthesia permits the dental surgeon to perform the necessary surgical procedure in a careful, gentle fashion that will be less stressful for both the operator and the patient. The improvements in agents for local anesthesia are probably the most significant advances that have occurred in dental science. Today's anesthetics are safe, effective, and can be administered with insignificant soft tissue damage and minimal concerns for allergic reactions. This article reviews the widely used local anesthetic agents for obtaining local anesthesia, and also discusses some frequently seen complications.