• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.510-516
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• 2016

• Journal of the Korean Statistical Society
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• v.7 no.1
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• pp.27-43
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• 1978

This paper deals with the problem of obtaining a minimum cost acceptance sampling plan for destructive testing. The cost model is constructed under the assumption that the sampling procedure takes the following form; 1) lots rejected on the first sample are acreened with a non-destructive testing, 2) the screening is assumed to be imperfect, and therefore, after the screening, a second sample is taken to determine whether to accept the lot of to scrap it. The usual sampling procedures for destructive testing can be regarded as special cases of the above one. Utilizing Hald's Bayesian approach, procedures for finding the global optimal sampling plans are given. However, when the lot size is large, the global plan is very different to obtain even with the aid of an electronic computer. Therefore a method of finding suboptimal plan is suggested. An example with uniform prior is also given.

• Tunnel and Underground Space
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• v.7 no.1
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• pp.75-83
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• 1997

The interest of diagnosis and maintenance of construction is increasing due to the collapse of infastructures. To obtain the complete, reliable and reproducible data ont he state of the entire structure, various non-destructive techniques are available, Especially, specific constructional characteristics of tunnels make the application of non-destructive tests more difficult. Despite of the complications of these conditions, non-destructive techniques should be capable of providing a description of the state of the tunnel lining, without the removal of the tunnel installations. In this paper, the infrared thermography technique using the difference of surface temperature was studied. The optimum equipment was selected and introduced, the principle, testing method and data anlaysis were investigated. Also, through the case study for inspection of concrete tunnel lining, this technique has proven to be a valuable non-destructive test for detecting the defects such as crack, leakage of water and exfoliation of concrete. The applicability and usefulness of this technique for estimation of concrete tunnel lining have been conformed.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.841-846
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• 2002

Development on non-destructive testing methods were performed to evaluate the effectiveness of crack repair for test beams induced a crack. Cracked beams are repaired with expoxy and microcement, and then they are tested by two methods, the ultrasonic pulse velocity method and the transfer function method. It is proved that the ultrasonic pulse velocity method is very valid for the evaluation of the effectiveness on expoxy repair, and the transfer function method is very applicable to evaluate the effectiveness on microcement repair.

• Smart Structures and Systems
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• v.17 no.1
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• pp.1-15
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• 2016

Rayleigh wave velocity along a straight survey line on a concrete plate is measured in order to compare different non-destructive data acquisition techniques. Results from a rolling non-contact data acquisition system using air-coupled microphones are compared to conventional stationary accelerometer results. The results show a good match between the two acquisition techniques. Rolling measurements were found to provide a fast and reliable alternative to stationary system for stiffness determination. However, the non-contact approach is shown to be sensitive to unevenness of the measured surface. Measures to overcome this disadvantage are discussed and demonstrated using both forward and reverse rolling measurements.

• Tunnel and Underground Space
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• v.14 no.1
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• pp.35-42
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• 2004

Impact-echo is a method for non-destructive testing of concrete structure. This method is based on the use of impact-generated stress wave which is propagated and reflected from internal flaws within concrete structure and external surface. In this study, we performed non-destructive testing using impact-echo methods for safety diagnosis of civil engineering and building structures. There are testing cases for the three models having one-dimensional form ; The first case is the measurement of thickness change of the model, the second is the detection of cavity in the model, and the third is the predictions of the lining thickness and the position of the cavity under tunnel lining condition.

• Journal of the Korea Institute of Building Construction
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• v.2 no.3
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• pp.123-130
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• 2002

Recently, it is being studied on the high strength concrete in many laboratories and being applied to the construction field actually. But non-destruction testing equation that to be proposed about normal strength concrete in Japan has been using because the systematic study results for the estimation of compressive strength of high strength concrete do nit exist. So it is essential to suggest the non-destruction testing equation for the estimation of compressive strength of high strength concrete. This is an experimental study to analyze and investigate the non-destruction testing equation for the estimation of compressive strength of high strength concrete. The results are as follows; The relation between rebound number, pulse velocity and compressive strength of high strength concrete have lower coefficient than combined method of rebound number and pulse velocity. Also new non-destructive testing equation for the estimation on the compressive strength of high strength concrete was suggested in this study, and it is considered that these equations have possibility to be applied in domestic construction field.

• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.45-54
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• 1999

Non destructive test is applied to revise mechanical strength and assume material strength or defect of material, equipment and structure, instead of fracture test. Especially, ultrasonic test has the characteristics such as an excellent permeability high-sensitiveness to fine defect and an almost exact measurement for position, size and direction of inner defect which differ from other non destructive tests. In this study, the program is developed to evaluate optimal testing condition, to distinguish obstacle echo and defect position. This program on the basic of Ray-Tracing model shows generation and processing of ultrasonic pulse. The simulation is compared with testing in the 3 cases of an oblique angle transducer like $45^{\circ},\;60^{\circ}\;and\;70^{\circ}$. The test result for all conditions is well compared with simulation result when relative not is within $0.1{\sim}7.2%$. And the course of several echos is simply assumed through simulation.

• Electronics and Telecommunications Trends
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• v.33 no.3
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• pp.59-69
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• 2018

Terahertz (THz) imaging and spectroscopy have been developed as non-destructive testing methods for various industrial applications. However, they have not been widely adopted in real applications owing to a high system price and the large size of conventional THz time-domain spectroscopy systems, which are based on ultrashort optical pulse lasers. Recently, various types of compact THz emitters and detectors have become available. As a result, THz non-destructive test (NDT) systems have become viable solutions. Herein, we briefly review the recent advances in THz NDT techniques adopting continuous-wave THz systems, including our recent results of a THz-based waterproof test system and an electrical connection inspection system for car manufacturing.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.115-121
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• 2012

Exploration in microelectromechanical systems(MEMS) and nanotechnology requires evaluation techniques suitable for sub-micron length scale so that thermal and mechanical properties of novel materials can be investigated for optimal design of miro/nanostructures. The ultrafast optical pump-probe technique provides a contact-free and non-destructive way to characterize nanoscale thin-films, and its ultrahigh temporal resolution enables the study of heat-transport phenomena down to a sub-picosecond regime. This paper reviews the principle of optical pump-probe technique and introduces its application to the area of micro/nano-NDE.