• Proceedings of the Korean Reliability Society Conference
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• 2001.06a
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• pp.235-238
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• 2001

It is well known that the reliability of materials of mechanical products is becoming more and more important not only for assurance of quality, but for international competition of products. In order to assure the reliability of materials or mechanical products nondestructive evaluation (NDE) techniques are playing more important roles. The existence of Internal defects in materials or mechanical parts is served as crack initiation site during the various loading condition. Historically, nondestructive evaluation (NDE) technique has been used almost exclusively for detecting microscopic discontinuities In materials or mechanical parts after they have been in service to expand the role of the NDE to include all aspects of materials production and application. Research efforts are being directed at developing and perfecting NDE techniques capable of monitoring (1) materials production processes (2) material integrity following transport, storage and fabrication and (3) the amount and rate of degradation during service. In addition, efforts are underway to develop technique capable of quantitative discontinuity sizing, permitting determination of response using fracture mechanics analysis, as well as techniques for quantitative materials characterization to replace the qualitative techniques used in the past. In this paper, the important role of NDE technology for reliability assurance of materials/mechanical parts is introduced.

• Journal of Korean Society of Steel Construction
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• v.15 no.1
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• pp.41-50
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• 2003

Nondestructive Damage Evaluation (NDE) techniques yield the damage location and its size from the modal characteristics of pre-damaged and post-damaged structures. To predict the system reliability of the aging structure, results from the NDE are integrated into the element/component failure probabilities. The element/component failure probabilities can be calculated from failure functions for each element/component with the aid of techniques from a structural reliability analysis. In this paper, a method to estimate the system reliability of a structure that is based on the reliabilities of elements/components in a given structure is presented. The efficacy of the combination of the nondestructive damage detection and the structural reliability evaluation is demonstrated using pre-damaged and post-damaged modal data obtained from numerical simulations of a rigid frame.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.6
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• pp.607-611
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• 2001

Ultrasonic inspection system consist of the operator, equipment and procedure. The reliability of results in ultrasonic inspection is affected by its ability. Furthermore, the reliability of nondestructive testing is influenced by the inspection environment, materials and types of defect. Therefore, it is very difficult to estimate the reliability of NDT due to the various factors. In this study, the probability of detection by logistic probability model and Monte Carlo simulation is used for the reliability assessment of ultrasonic inspection. The utility of the NDT reliability assesment is verified by the analysis of the data from round robin test nth these models.

• Tribology and Lubricants
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• v.26 no.6
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• pp.336-340
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• 2010

Ultrasound thermography detects defects by radiating 20 ~ 30 kHz ultrasound waves to the samples and capturing the heat generated from the defects with the use of an infrared thermographic camera. This technology is being spotlighted as a next-generation NDE for the automobile and aerospace industries because it can test large areas and can detect defects such as cracks and exfoliations in real time. The heating mechanism of the ultrasound vibration has not been accurately determined, but the thermomechanical coupling effect and the surface or internal friction are estimated to be the main causes. When this heat is captured by an infrared thermographic camera, the defects inside or on the surface of objects can be quickly detected. Although this technology can construct a testing device relatively simply and can detect defects within a short time, there are no reliable data about the factors related to its detection ability. In this study, the ultrasound thermography technique was used to manufacture gasoline and diesel engine piston specimens, and nondestructive reliability tests to verify the applicability and validity of the ultrasound thermography technique.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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• pp.230-234
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• 2009

As concrete ages, the surrounding environment is expected to have growing influences on the concrete. As all the impacts of the environment cannot be considered in the strength-estimating model of a nondestructive concrete test, the increase in concrete age leads to growing uncertainty in the strength-estimating model. Therefore, the variation of the model error increases. It is necessary to include those impacts in the probability model of concrete strength attained from the nondestructive tests so as to build a more accurate reliability model for structural performance evaluation. This paper reviews and categorizes the existing strength-estimating statistical models of nondestructive concrete test, and suggests a new form of the strength-estimating statistical models to properly reflect the model uncertainty due to aging of the concrete. This new form of the statistical models will lay foundation for more accurate structural performance evaluation.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.198-209
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• 2012

The present paper reviews the widely used surface microstructural investigation technique and micro/nano nondestructive evaluation(NDE) technique which is able to evaluate the surface and subsurface. In general, the micro/nano defects and microstructural state of surface have great influence on the mechanical, physical, and chemical properties of bulk materials. The investigation technique of surface microstructure is possible to evaluate the defects and microstructural state with high reliability. The various applications and developments of each inspection technique have been introduced. Consequently, it is thought that the technique developments and applications of micro/nano NDE in nondestructive industries are extensively possible hereafter.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.217-224
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• 2002

The performance demonstration round robin test was conducted to quantify the capability of ultrasonic inspection for in-service and to address some aspects of reliability for nondestructive evaluation. The fifteen inspection teams who employed procedures that met or exceeded ASME Sec. XI code requirements detected the piping of nuclear power plant with various cracks to evaluate the capability of detection. With data from PD-RR test, the performance of ultrasonic nondestructive inspection could be assessed using probability of length and depth sizing of cracks.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.157-164
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• 2003

The pulse-echo method is one of the most widely used ultrasonic techniques for application of nondestructive evaluation. Particularly, quantitative nondestructive evaluation of defects has been considered more important to assure the reliability and the safety of structure. Frequency energy in adhesive joints is based on the ultrasonic wave analysis. The attenuation coefficient upon wave amplitude and the frequency energy that is expressed in the term of wave pressure amplitude were utilized for the primary wave experiment. By means of a control experiment, it was confirmed that the variation of the frequency energy in adhesive joints depends on transition by stress variation. In this paper, the ultrasonic characteristics were measured for single lap joint and Double Cantilever Beam specimen with different fracture modes that was subjected to stress. Consequently, the data that was obtained from the adhesive specimen was analytically compared to the fracture mechanics parameter

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.245-251
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• 2002

Electronic Speckle Pattern Interferometry(ESPI) is one of optical technique to measure displacement precisely, uses CCD camera to show result image in real time. General ESPI system measures in-plane or out-of-plane displacement. Shearography is one of electronic speckle pattern interferometric methods which allow full-field observation of surface displacement derivatives and it is robust in vibration. The shearography provides non-contacting technique of evaluating defects nondestructively In this study, the shearography was used to evaluate defects in Carbon Fiber Reinforced Plastic(CFRP). Various sizes of artificial defects were embedded in various depths of woven CFRP plate. Effects due to the variation of size and depth of defects were evaluated in this study.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.4
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• pp.304-312
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• 1998

In order to assure the reliability and integrity of structures such as bridges, Power and petrochemical plants, nondestructive evaluation techniques are recently playing more important roles. Among the various kinds of nondestructive evaluation techniques, ultrasonic technique is one of the most widely used methods for nondestructive inspection of internal defects in structures. For the reliable quantitative evaluation of internal defects from the experimental ultrasonic signals, a numerical analysis of ultrasonic scattering field due to a defect distribution is absolutely required. In this paper, the SH-wave scattering by multi-cavity defects using elastodynamic boundary element method is studied. The effects of shape of defects on transmitted and reflected fields are considered. The interaction of multi-cavity defects in 50-wave scattering is also investigated. Numerical calculation by the boundary element method has been carried out to predict near field solution of scattered fields of ultrasonic SH-wave. The presented results would be useful to improve the sensitivity of flaw defection for inverse analysis and pursue quantitative nondestructive evaluation for inverse problem.