• Structural Engineering and Mechanics
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• v.76 no.5
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• pp.631-641
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• 2020

In the present work, an approach for the multiple time probabilistic characterization of the response of linear structural systems subjected to random non-Gaussian processes is presented. Its fundamental property is working directly on the multiple time probability density functions of the actions and of the response. This avoids of passing through the evaluation of the response statistical moments at multiple time or correlations, reducing the computational effort in a consistent measure. This approach is the extension to the multiple time case of a previously published dynamic Probability Transformation Method (PTM) working on a single evolution of the response statistics. The application to some simple examples has revealed the efficiency of the method, both in terms of computational effort and in terms of accuracy.

• Advances in Energy Research
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• v.8 no.3
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• pp.137-144
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• 2022

This study presents an experimental investigation of conventional and enhanced receiver tube performance for the application of a concentrated parabolic trough collector (CPC). The CPC system is fabricated and tested for the conventional and enhanced receiver tubes. The experiments were performed on both tubes for the change of flow rates. The temperature rise of the tube surface, as well as working fluid, were monitored for varying flow rates. The results were compared and discussed in view of enhanced CPC system performance. The results exhibited that the temperature rise of the working fluid passing through the tube was more in the case of the enhanced tube compared to the conventional receiver tube under the same flow rates.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1511-1516
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• 2007

Because Seaming process of MPJ (Mechanical Press Joining) has various design factors such as thickness, bending radius, seaming width, caulking press width and the dynamic factor such as multistage plastic working, elastic recovery, residual stress, the optimum conditions can't be easily determined. Using a design of experiment based on the FEM, which has several advantages such as less computing, high accuracy performance and usefulness, this study was performed investigating the interaction effect between the various design factor as well as the main effect of the each design factor during drum MPJ and proposed optimum condition using center composition method among response surface derived from regression equation of simulation-based DOE.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.06a
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• pp.135-144
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• 1995

Cold Forging has advantage in high accuracy and short working time. However large-skzed and complicated parts are difficult to process with cold forging. Thus large-sized and complicated parts have been processed with two pieces, or combind forging that is hot forging in addition to cold sizing. Recently, large-sized and complicated parts can be manufactured with cold forging alone by advanced cold forging technology using the long-stroke press. In this paper, cold forging technology of large-sized and complicated parts are investigated, including tripod slide housing for constant velocity joint and drive shaft for starter.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.03a
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• pp.31-40
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• 1995

Powder metallurgy process has many advantages such as hight efficientyof material, mass productivity and complex shape production with good mechanical properties. Among the powder forming processes, incremental forging allows the consolidation to be achieved with amaller force then those required by conventional forging. In particular the proces known as rotary forging is an unique and prodominant process known as rotary forging is an unique and prodominant process in which the working constraints approximate to those in normal closed die forging. This study is concerned with the powder compaction by rotary forging process. An experimental rotary forging press with 500kN load capacity has been developed, which is equippe dwith the rotational conicla die inclined to the central axis of the press at arbitrary angle. It is found that the highly densified P/M parts can be obtained by rotary forging process and the material properties are superior to those of the conventrional sintered parts. The detailedcomparision of the mechanical properties by rotary forging process with those by conventional process are given.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.598-602
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• 1996

This study is performed for investigating the effects of stripping and counter punching force on shearing characteristics in fine blanking, such as camber, burr-height and dimensional accuracy, etc by experiments. Conventional hydraulic press equipped with specially designed hydraulic unit is used for experiments so that both the stripping force and counter punching force are arbitrarily adjusted according to experimental conditions. Two kinds of materials, hot rolled steel sheet(1mm, 3mm) and pure aluminum(1mm, 3mm) are selected in order to examine the influence of strength and thickness of working materials in blanking of T-shaped products. Based on the experimental results of this study, it can be concluded that the finely cut surface of sheared blank can be obtained even in conventional hydraulic press if additional equipments and special dies are employed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.50-55
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• 2021

In this study, to create circular holes on an inclined conic face, we developed a novel process of vertical piercing on the plane before drawing, instead of applying an expensive cam-piercing method. The pierced holes are deformed during the drawing, and their shapes are affected by the size of the center hole. Using the Abaqus CAE program, the deformation tendency of the holes, according to the diameter of the center hole, was identified, and the diameter for securing the roundness of the side holes were determined through actual experiments. The developed process was successfully applied to mass production of the part, and a cost reduction is expected.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.1012-1016
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• 2002

This paper describes a research work of developing computer-aided design of a product with bending and piercing for progressive working. An approach to the system for progressive working is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written in Auto-LISP on the Auto-CAD with a personal computer and is composed of four main modules, which are input and shape treatment, flat pattern layout, strip layout, and die layout modules. The system is designed by considering several factors, such as bending sequences by fuzzy set theory, complexities of blank geometry, punch profiles, and the availability of a press equipment. Strip layout drawing generated in the strip layout module is presented in 3-D graphic forms, including bending sequences and piercing processes with punch profiles divided into for external area. The die layout module carries out die design for each process obtained from the results of the strip layout. Results obtained using the modules enable the manufacturer for progressive working of electric products to be more efficient in this field.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.137-146
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• 2005

This paper describes a research work to develop a computer-aided design for the product made by progressive working of bending and piercing. An approach to the system for progressive working is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written in AutoLISP on the AutoCAD with a personal computer and is composed of three main modules, which are input and shape treatment, flat pattern layout, strip layout modules. The system is designed by considering several factors, such as piercing and bending sequences by fuzzy set theory, complexities of blank geometry, punch profiles, and the availability of a press equipment. Strip layout drawing generated in the strip layout module is presented in 3-D graphic forms, including piercing and bending sequences with punch profiles divided into for external area. Results obtained using the modules enable the manufacturer for progressive working of electric products to be more efficient in this field.

• Structural Engineering and Mechanics
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• v.51 no.6
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• pp.973-988
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• 2014

This paper presents a factor-analysis based questionnaire categorization method to improve the reliability of the evaluation of working conditions without influencing the completeness of the questionnaire both in Taiwanese and Chinese construction enterprises for structural engineering applications. The proposed approach springs from the AI application and expert systems in structural engineering. Questions with a similar response pattern are grouped into or categorized as one factor. Questions that form a single factor usually have higher reliability than the entire questionnaire, especially in the case when the questionnaire is complex and inconsistent. By classifying questions based on the meanings of the words used in them and the responded scores, reliability could be increased. The principle for classification was that 90% of the questions in the same classified group must satisfy the proposed classification rule and consequently the lowest one was 92%. The results show that the question classification method could improve the reliability of the questionnaires for at least 0.7. Compared to the question deletion method using SPSS, 75% of the questions left were verified the same as the results obtained by applying the classification method.