• Architectural research
• /
• 제18권4호
• /
• pp.179-184
• /
• 2016

The structure must be periodically checked and measures must be taken to prevent deterioration in building construction. From this point of view, a nondestructive test is essential to estimate whether the construction of buildings is proper, and whether the dimension of depositing concrete is consistent and without damage. This study estimated the thickness of the concrete component of construction framework using the ultrasonic velocity method and the impact echo method, in order to investigate reliability of the estimation of the thickness of normal strength concrete and high strength concrete, leading to the following conclusions. In the estimation of the thickness of the concrete structures, specimens of normal strength of 24MPa and specimens of high strength of 40MPa demonstrated an average error rate of 5.1% and 2.2%, respectively. The impact-echo method, one of the non-destructive tests, is verified as an efficient diagnostic technique. With this information, we will determine specific standards for the maintenance of structures, and the re-creation of lost building blueprints.

• 비파괴검사학회지
• /
• 제23권6호
• /
• pp.577-582
• /
• 2003

This paper describes a new technique for thickness measurement of a very thin layer less than one-quarter of the wavelength of ultrasonic wave used in the ultrasonic pulse-echo measurements. The technique determines the thickness of a thin layer in a tapered medium from constructive interference of multiple reflection waves. The interference characteristics are derived and investigated in theoretical and experimental approaches. Modified total reflection wave g(t) defined as difference between total and first reflection waves increases in amplitude as the interfacial layer thickness decreases down to zero. A layer thickness less than one-tenth of the ultrasonic wavelength is measured using the maximum amplitude of g(t) with a good accuracy and sensitivity. The method also requires no inversion process to extract the thickness information from the waveforms of reflected waves, so that it makes possible to have the on-line thickness measurement of a thin layer such as a lubricating oil film in thrust bearings and journal bearings during manufacturing process.

• 한국공작기계학회논문집
• /
• 제10권3호
• /
• pp.55-60
• /
• 2001

A technique on the detection of tool wear based on the ultrasonic pulse-echo method in turning process is presented. The change in amount of the reflected energy from nose and flank of the tool can be related to the level of tool wear and mechanical integrity of the tool, that is, there exists an excellent correlation between the ultrasonic measurement and tool wear. As a results, the method is very useful for the prediction of cutting tool life and the determination of tool exchange period.

• 비파괴검사학회지
• /
• 제28권6호
• /
• pp.504-511
• /
• 2008

This paper proposes an ultrasonic measurement method for measurement of linear interfacial stiffness of contacting surface between two steel plates subjected to nominal compression pressures. Interfacial stiffness was evaluated by using shear waves reflected at contact interface of two identical solid plates. Three consecutive reflection waves from solid-solid surface are captured by pulse-echo method to evaluate the state of contact interface. A non-dimensional parameter defined as the ratio of their peak-to-peak amplitudes are formulated and used to calculate the quantitative stiffness of interface. Mathematical model for 1-D wave propagation across interfaces is developed to formulate the reflection and transmission waves across the interface and to determine the interfacial stiffness. Two identical plates are fabricated and assembled to form contacting surface and to measure interfacial stiffness at different states of contact pressure by means of bolt fastening. It is found from experiment that the amplitude of interfacial stiffness is dependent on the pressure and successfully determined by employing pulse-echo ultrasonic method without measuring through-transmission waves.

• 한국정밀공학회지
• /
• 제20권3호
• /
• pp.157-164
• /
• 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

• E2M - 전기 전자와 첨단 소재
• /
• 제9권10호
• /
• pp.1053-1059
• /
• 1996

The pulse-echo response of the piezoceramics PZT-polymer 3-3 type composite transducers with various PVA additions were investigated. The PZT powder was prepared by the molten salt synthesis method. The porous PZT specimens will be used as a filler to make 3-3 type comosite were prepared from a mixture of PZT and polyvinylalcohol(PVA) sphere by utilizing BURPS(Bumout Plastic Sphere) technique. It was shown that the transmitting and receiving sensitivity of 3-3 type piezoelectric composite transducers could be improved than that of solid PZT transducers. The reason is that 3-3 type piezoelectric composite have low dielectric constant, density and acoustic impedance. The distance between transducer and reflector was in good agreement with the distance calculated from the longitudinal velocity of the specimens and receiving time observed pulse-echo responses on the ultrasonic transducer analyzer.

• 비파괴검사학회지
• /
• 제36권2호
• /
• pp.138-148
• /
• 2016

Measurement of elastic constants is crucial for engineering aspects of predicting the behavior of materials under load as well as structural health monitoring of material degradation. Ultrasonic velocity measurement for material properties has been broadly used as a nondestructive evaluation method for material characterization. In particular, pulse-echo method has been extensively utilized as it is not only simple but also effective when only one side of the inspected objects is accessible. However, the conventional technique in this approach measures longitudinal and shear waves individually to obtain their velocities. This produces a set of two data for each measurement. This paper proposes a simultaneous sensing system of longitudinal waves and shear waves for elastic constant measurement. The proposed system senses both these waves simultaneously as a single overlapped signal, which is then analyzed to calculate both the ultrasonic velocities for obtaining elastic constants. Therefore, this system requires just half the number of data to obtain elastic constants compared to the conventional individual measurement. The results of the proposed simultaneous measurement had smaller standard deviations than those in the individual measurement. These results validate that the proposed approach improves the efficiency and reliability of ultrasonic elastic constant measurement by reducing the complexity of the measurement system, its operating procedures, and the number of data.

• 대한기계학회논문집A
• /
• 제24권1호
• /
• pp.52-61
• /
• 2000

The role of quantitative nondestructive evaluation of defects is becoming more important to assure the reliability and the safety of structure, which can eventually be used for residual life evaluation of structure on the basis of fracture mechanics approach. Although ultrasonic technique is one of the most widely used techniques for application of practical field test among the various nondestructive evaluation technique, there are still some problems to be solved in effective extraction and classification of ultrasonic signal from their noisy ultrasonic waveforms. Therefore, crack size determination through a neural network based on the back-propagation algorithm using back-scattered ultrasonic signals is established in this study. For this purpose, aluminum plate containing vertical or inclined surface breaking crack with different crack length was used to receive the back-scattered ultrasonic signals by pulse echo method. Some features extracted from these signals and sizes of cracks were used to train neural network and the neural network's output of the crack size are compared with the true answer.

• 한국해양공학회지
• /
• 제2권1호
• /
• pp.135-149
• /
• 1988

Friction welding has been shown to have significant economic and technical advantages. However, one of the major concerns in using friction welding is the reliability of the weld quality. No reliable nondestructive test method is available at present for detecting weld quality, particularly in a production environment. Friction welds are formed by the mechanisms of diffusion as well as mechanical interlocking. The severe plastic flow at the interface by forge action of the process brings the subsurfaces so close together that detection of any unbonded area becomes very difficult. This paper presents an attempt to determine the friction weld strength quantitatively using the ultrasonic pulse-echo method. Instead of detecting flaws or cracks at the interface, the new approach calculates the coefficient of reflection based on measured amplitudes of the echoes. It has been finally confirmed that this coefficient could provide the quantitative relationship to the weld quality such as tensile strength, torsional strength, impact value, hardness, etc. So a new nondestructive analysis system of friction weld strength of dissimilar metals using an ultrasonic technique could be well developed.

• 비파괴검사학회지
• /
• 제19권4호
• /
• pp.259-269
• /
• 1999

최근 초음파속도법과 충격반향기법 등과 같이 탄성파를 이용한 비파괴검사 방법이 콘크리트의 강도나 탄성계수를 결정하는데 유용하게 사용되고 있다. 하지만 탄성파 속도에 영향을 미치는 다양한 인자들이 고려되지 않은 상태에서 비파괴검사가 행해지고 있어 실제로 만족할 만한 결과를 주지 못하고 있다. 이 연구에서는 다양한 영향인자들 중에서 특히 콘크리트의 수분함유량이 종파 속도에 미치는 영향정도를 실험을 통해 조사하였다. 콘크리트 내부의 수분함유량이 감소하면, 즉 콘크리트가 건조해지면 종파 속도는 점점 감소하며, 충격반향기법에 의해 측정된 막대파 속도가 초음파 속도보다 수분의 영향을 더 많이 받는 것으로 나타났다. 또한 기건양생하에서는 재령이 증가함에 따라 수분함유량이 감소하게 되어 콘크리트의 종파 속도는 거의 증가하지 않는 반면에 강도는 점차적으로 증가하는 경향을 보이기 때문에 종파 속도와 콘크리트 강도의 상관관계 설정시 이를 반드시 고려해야 할 것으로 판단된다.