• Laser Solutions
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• v.2 no.3
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• pp.19-31
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• 1999

This paper introduces the monitoring scheme of laser welding quality using neural network. The developed monitoring scheme detects light signal emitting from plasma formed above the weld pool with optic sensor and DSP-based signal processor, and analyzes to give a guidance about the weld quality. It can automatically detect defects of laser weld and further give an information about what kind of defects it is, specially partial penetration and porosity among the interior defects. Those could be detected only by naked eyes or X-ray after welding, which needs more processes and costs in mass production. The monitoring scheme extracts four feature vectors from signal processing results of optical measuring data. In order to classify pattern for extracted feature vectors and to decide defects, it uses single-layer neural network with perceptron learning. The monitoring result using only the first feature vector shows confidence rate in recognition of 90%($\pm$5) and decides whether normal status or defects status in real time.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.365-370
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• 2003

The problem of brake judder is typically caused by quality defects in manufacturing. This quality problem, however, can't be controlled deterministically and requires analyses and designs considering uncertainties. This paper presents a method for dynamic analysis of a brake judder considering uncertainties. Firstly, quality defects, which come from the uncertainties, are determined by examination of symptoms of the brake judder quality problem. Effective quality defects are selected by investigation of process capability and comparison of sensitivity of each quality defects and noise levels of the effective quality defects are determined. Secondly, flexible multibody dynamic analysis and finite element analysis according to the proposed method are carried out. Finally, The analysis results are compared with the test results with noise levels of the effective quality defects.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.29-33
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• 1996

In this study, specimens were prepared which have some defects on the buttweld joint of mild steel. In order to detect the defects of specimens, the following tests were put to : AUT and RT. When the results of the three tests were compared, the conclusion could be brought to as follows. 1) AUT outstrips RT in the abillity to detect plane defects like slags or cracks, but RT excels AUT in the ability to detect spheroidal defects like blowholes. 2) RT detects neither taper cracks nor very closed cracks, whereas AUT detects both of them. 3) AUT can detect at once plane defects like cracks and spheroidal defects like blowholes.

• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.361-366
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• 2013

An imaging technique to visualize the internal defects in a plate-type nuclear fuel specimen was developed by using an active optical interferometer for a nondestructive quality inspection. A periodic thermal wave having a sinusoidal intensity pattern induced a periodical strain variation for the specimen. The varying strain image was acquired using an optical laser interferometer. The strain distribution over the internal defects will be distorted in an acquired strain image because a part of the thermal wave will be reflected from these defects during propagation. In this paper, internal defects were efficiently visualized by sequentially accumulating the extracted defect components. The experimental results confirmed that the developed visualization system can be a valuable tool to detect the internal defects in plate-type nuclear fuel.

• Journal of the Semiconductor & Display Technology
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• v.9 no.3
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• pp.59-63
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• 2010

This paper proposes computer visual inspection algorithms for various LCD defects which are found in a manufacturing process. Modular vision processing steps are required in order to detect different types of LCD defects. Those key modules include RGB filtering for pixel defects, gray-scale morphological processing and Hough transform for line defects, and adaptive threshold for spot defects. The proposed algorithms can give users detailed information on the type of defects in the LCD panel, the size of defect, and its location. The machine vision inspection system is implemented using C language in an embedded Linux system for a high-speed real-time image processing. Experiment results show that the proposed algorithms are quite successful.

• Design & Manufacturing
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• v.14 no.4
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• pp.52-57
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• 2020

In this study attempted to prevent defects due to blow holes among defects of sand casting products. It was intended to reduce the defect rate by reducing the blow hole of the inner surface. Currently, expectations and requirements for the quality level of non-ferrous aluminum casting in the casting industry are increasing. In addition, the shape is complex and the shrinkage precision is required. Among them, the test prototype is expensive to manufacture the mold, and the production time is also long, and the product is manufactured by sand casting. At this time, the highest defect rates are defects caused by shrinkage defects, surface defects, and blow holes.. At this study, the manufacturing time was shortened by using the shape of the fluid movement path in advance. Also, it is possible to reduce defects due to blow holes.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.1
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• pp.13-23
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• 1996

Weld defects degrade the strength and safety of astructure and are resulted from the various cases. The complexity of causal relation of weld defects requires an expert for the analysis of weld defects and the measures counter to them. An expert system has the intelligent functions such as the representation of knowledge and the inference. On this research, weld defect are systematically analysed and their causal model is developed. This information is saved to the knowledge base. The suitable inference algorithm for the diagnosis of weld defects is developed and realized with C++ programming.

• Journal of KSNVE
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• v.5 no.3
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• pp.353-360
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• 1995

A new automatic diagnostic system for predicting multiple defects in rolling element bearings is developed by taking probbability into account. A database is constructed from the frequency characteristics of tested bearings with various types of defects. The proposed algorithms for the automatic diagnosis of bearing defects are shown to be satisfactory through the experiments. This method can be effectively used for quality control of the rolling bearing in plants.

• Journal of the Korean housing association
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• v.21 no.6
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• pp.71-80
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• 2010

The purpose of this study is to classify defects of the residential building by analyzing the defect specified by prequalification of residential building reconstruction and to suggest the solution of the problem which can be arisen during each stage of plan, construction and maintenance. By sorting the main defects which is specified by pre-qualification of residential building reconstruction for three years from August 2006 to August 2009 into 4 catagories and analyzing the cause of the defects, we draw the way of maintenance to prevent the defects and make pleasant residential environment. The reason for the frequent defects from residential building is mainly deterioration. It occured on the finishing more than on the structure, which means that residents can find defects easier on the finishing than the structure and clear the demand for repair. The result of analyzing of pre-qualification of residential building reconstruction is that the defects mostly caused small, masonry constructed and lower apartment. The apartment which is not into legal right for maintenance naturally have more defects than the others. In conclusion, it is necessary to establish a law of obligation duty of the maintenance of small apartment.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.6
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• pp.666-671
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• 2000

Objectives: This study evaluated the availability of mandibular symphysis corticocancellous block grafts in patients treated for reconstruction of intraoral jaw defects. Materials & Methods: 8 patients with mandibular and maxillary bony defects were treated with corticocancellous block of symphysis. The types of defects included 4 pathologic jaw defects and 4 vertical and/or horizontal alveolar deficiencies. The age ranged from 13 to 45 years. Additional treatments such as plate fixation, alloplastic bony substitutes, and/or barrier membrane application were perfomred. They were evaluated for complications and healing of defects. Follow-up period ranged from 6 to 15 months. Results: 2 patients experienced complications such as wound dehiscence and mild resorption of exposed bone. None of the patients needed secondary operation. Paresthesia of lip, chin, and teeth were recovered completely by 6 months postoperatively. Reconstructed wound showed favorable healing and bony consolidation. Conclusion: Corticocancellous block of mandibular symphysis can be used for the reconstruction of a variety of intraoral local jaw defects selectively. Advantages were easy fixation of graft, possibility of restoration of original alveolar contour, and decreased donor site morbidity.