• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.205-211
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• 2013

This paper studies on mechanical properties, fractures, and ultrasonic characteristics of Pure Titanium welds using ultrasonic attenuation. Ti specimen was made by using AR purge gas. When the titanium weld specimen is fractured, Tensile tests were conducted in order to observe the ultrasonic signal changes. A scanning electron microscope(SEM) was used to observe changes in failure surface and an ultrasonic normal probe with the central frequency of 4 MHz was used to obtain ultrasonic signals. As a result, the value of the mechanical properties in the weld zone was lower than that in the base zone and heat affected zone(HAZ) from Ti. Also the grain size in the weld zone was bigger than that in the weld zone and HAZ from Ti. Ultrasonic signals using a RMS method presents correlation between envelope area and the tensile strength. Consequently, the ultrasonic method could be potential tool for integrity evaluation of the Ti weld zone.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.115-115
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• 2009

아연코팅강판의 레이저 용접시 발생하는 용접결함은 이미 널리 알려진 이슈이다. 그러나 대부분의 연구가 박판을 중심으로 이루어지고 있어서, 후판을 중심으로 한 조선산업에서의 아연코팅 강판의 연구는 매우 미진한 실정이다. 이중 후판 아연코팅강판의 결함검출연구는 그 연구가 거의 전무한 실정으로, 본 연구에서는 후판 아연코팅강판의 레이저 겹치기용접시의 결함검출을 중심으로 실험을 실시하였다. 실험은 Fig. 1에서와 같이 광신호와 음향신호의 RMS를 통하여 raw signal에서 잘 나타나지 않았던 신호의 패턴을 확인함으로써 실제 신호와 비드와를 대응을 가능하게 하였다. 또한 결함 발생시의 RMS값을 건전한 상태와 비교분석하여 실제 결함검출의 가능성도 확인할 수 있었다.

• Journal of Welding and Joining
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• v.16 no.3
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• pp.102-110
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• 1998

The horizontal fillet welding is prevalently used in heavy and ship building industries to fabricate the large scale structures. A deep understanding of the horizontal fillet welding process is restricted, because the phenomena occurring in welding are very complex and highly non-linear characteristics. To achieve the satisfactory weld bead geometry in robot welding system, the seam tracking algorithm should be reliable. The number of seam tracker was developed for arc welding automation by now. Among these seam tracker, the arc sensor is prevalently used in industrial robot welding system because of its low cost and flexibility. However, the accuracy of arc sensor would be decreased due to the electrical noise and metal transfer. In this study, the signal processing algorithm based on the neural network was implemented to enhance the reliability of measured welding current signals. Moreover, the seam tracking algorithm in conjunction with the signal processing algorithm was implemented to trace the center of weld line. It was revealed that the neural network could be effectively used to predict the welding current signal at the end of weaving.

• Journal of Welding and Joining
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• v.30 no.1
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• pp.19-26
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• 2012

• Proceedings of the KWS Conference
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• 1998.10a
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• pp.284-287
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• 1998

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1156-1169
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• 1989

본 연구에서는 용접도중 발생할 수 있는 용접질 저항요인을 전극분리현상을 측정하여 파악하고 용접 열입력에 해당하는 용접전류를 학습제어방식(self-learning control)에 의하여 컴퓨터와 주변기기(interface)를 통해 조절함으로서 요구되는 균일한 용접질이 항상 보장되도록 하였다. 여기서 학습제어방식을 태택한 이유는 제어하고자 하는 대상의 동적 모델(dynamic model)이 없어도 제어기 이득의 선정이 비교적 자유롭고 용접 제어장치가 자체적으로 감지(monitoring)한 신호로 판단하여 제어동작을 취함으로서 용접시 축적되는 정보(data)가 용접기에 일종의 지능을 부여할 수 있어서 진보된 개념의 용접제어장치 개발의 가능성을 검토해 보기 위함이다.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.3
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• pp.30-36
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• 2000

In this paper, an ultrasonic testing method for inspection of high attenuation welding area using the minimum Polarity threshold algorithm which combines the minimum amplitude selection algorithm and polarity threshold algorithm is suggested to increase the signal to noise ratio of the flow signal. In order to confirm the usefulness of the suggested algorithm, experiments were performed using four probes and standard specimens following the ASME Xl Code. As a result, scattering signals were observed from the SE(safe end) and CCSS (centrifugal casting stainless steel) materials due to the microstructural characteristical, and the detectability was reduced due to the highly attenuated signal from the weldment area, but it was conformed that using the suggested algorithm, the signal to noise ratio increased about 2.6.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1507-1512
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• 2010

In this study, the plasma induced by $CO_2$ laser lap welding of 6t Zn coated steel used for ship building was measured using photodiodes and a microphone. Then, the welding phenomenon with gap clearance of lap joint was compared with RMS-treated signal. Thus, we found that intensity of the RMS-treated signal increased with Zn vaporization; further, the presence of defects results in rapid variations with the RMS value as a function of lap-joint parameters. Besides, the FFT value of the raw signal with variations of changing welding parameters was calculated, and then the calculated FFT frequency value was set as the bandwidth of digital filter for a more accurate in-process monitoring. The RMS values were acquired by filtering the raw signal. By matching the weld beads and the calculated RMS values, we confirmed that there is a strong relationship between the signals and the defects.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.248-248
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• 2000

본 연구는 조선 소조립, 판넬조립 등의 공정에서 발생되는 필렛 용접 부위의 용접 자동화를 위한 로봇 시스템 개발에 관한 연구이다. 조선등의 중공업 분야에서는 작업이 중량이고 대형임에 따라 로봇이 부재의 특정위치로 이동하여 작업해야 한다. 또한 작업대상의 형상이나 치수가 매번 변경됨에 따라 이에 능동적으로 대처할 수 있어야 한다. 본 연구에서는 두 대의 로봇(2대x6축=12축)이 다축 문형 캔트리(4축)에 장착된 조선용 필렛용접 로봇 시스템(16축)을 개발하였다. 필렛용접부재를 중심으로 두 대의 로봇이 양쪽을 동시에 용접하는 방식으로 고속회전토치를 적용하여 위빙동작없이 원하는 용접각장(Leg Length)을 생성할 수 있다. 캔트리 시스템은 PC 기반의 별도 제어기로 구성하여 두 대의 로봇 제어기와 신호 입출력에 의해 동시동작이 가능하도록 하였으며, 작업장에 놓인 부재의 위치오차를 보장하기 위하여 시각센서를 적용하였다. 용접시작점의 위치보정을 위한 시작점 검출을 위해접촉센서(Touch Sensor)를 적용하였으며, 용접선 추적을 위해서 아크센서(Arc Sensor)를 적용하였다. 본 시스템 2000년 1월 제작 설치가 완료되어 현재 성능 테스트가 완료된 상태로 향후 생산현장에 적용될 계획이다.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.4
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• pp.209-215
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• 2020

In this paper, we propose an algorithm for segmenting weld bead images using edge enhancement and active contours. In the proposed method, high-frequency filtering and contrast improvement are performed for edge enhancement, and then, by applying the active contour method, only the weld bead region can be obtained. The proposed algorithm detects an edge through high-frequency filtering and reinforces the detected edge by using contrast enhancement. After the edge information is improved in this way, the weld bead area can be extracted by applying the active contour method. The proposed algorithm shows better performance than the existing methods for segmenting the weld bead in the image. For the objective reliability of the proposed algorithm, it was compared with the existing high pass filtering methods, and it was confirmed that the welding bead segmentation of the proposed method is excellent. The proposed method can be usefully used in evaluating the quality of the weld bead through an additional procedure for the segmented weld bead.