• Journal of the Korean Society for Precision Engineering
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• v.16 no.7
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• pp.24-31
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• 1999

Bulging is a forming method to shape of die cavity by using hydraulic pressure in tube or vessel. Bulging machine and die were developed in order to produce vessel for keeping warm. Bulging machine is a double type with two horizontal cylinders for bulging of two pieces at the same time. The developed die system has one bulging die and two drawing dies for necking at the both ends of tube. The diameter of tube expands by hydraulic pressure in tube. at the same time, thrust at the both ends of tube. pushes tube in the direction of expansion to obtain high expanding rate with no crack. In this study, the bulging properties were investigated to solve tube crack and necking in manufacturing vessel by the combination method of bulging and drawing. As a result, high expanding rate of tube radius without crack, precision necking and high productivity were obtained.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.4
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• pp.40-46
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• 2001

Bulging is a forming method to shape die cavity by using hydraulic pressure in tube or vessel. Bulging machine and die were developed in order to produce vessel for keeping warm. Bulging machine is a double type with two horizontal cylinders for bulging of two pieces at the same time. The developed die system has one bulging die and two drawing dies for necking at both ends of the tube. The diameter of tube expands by hydraulic pressure in tube. At the same time, thrust at both ends of the tube pushes tube in the direction of expansion to obtain high expansion rate with no crack. In this study, the bulging properties were investigated to solve tube crack and necking in manufacturing vessel by combining bulging and drawing. As a result, high expanding rate of tube radius without crack, precision necking and high productivity were obtained.

• Transactions of Materials Processing
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• v.24 no.1
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• pp.20-27
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• 2015

Hot tensile tests were conducted at different temperatures ranging from $20^{\circ}C$ to $550^{\circ}C$ to evaluate the mechanical properties of Al5052 seamless tubes. Such tubes can provide the technological foundation for complex forming using hot air bulging. Hot air bulging is one of the recently developed hydroforming techniques and it has some limitations in terms of cycle times. The benefits of hot air bulging are weight and cost savings through part consolidation and reduced post-forming processes such as welding and piercing. In order to extend the forming limits of Al lightweight material hot air bulging was investigated. A heated tube was placed in a heated die and sealed at the ends by sealing cylinders. The heated tube was subsequently expanded against the die cavity wall by internal pressure using air medium. The results of the current study show that axial feeding speed and air pressure have an effect on the formability of Al tubes during air bulging at elevated temperatures.

• Aerospace Engineering and Technology
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• v.7 no.2
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• pp.103-109
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• 2008

A study has been conducted on the bulging process of regenerative cooling nozzle which is essential for the manufacturing of liquid rocket thrust chamber. Tension tests have been performed for the material to be used for the development of the bulging process and mechanical properties are obtained by the test. Two or three bulging tools were required to complete the bulging process. The necking of the material was a major failure encountered in the bulging process and a research has revealed that grain size of the material has considerable effect on its occurrence. The presently developed bulging process with a controlled grain size material has been successfully applied to the manufacturing of subscale and 30-tonf full scale regeneratively cooled nozzle while demonstrating the applicability and usefulness of the presently developed bulging process.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.329-337
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• 2019

This paper presents an experimental investigation about visualization of bulging development of geosynthetic-encased stone column (GESC) based on the digital image correlation (DIC) technique and transparent soil. Visual model tests on GESC and ordinary stone column (OSC) were carried out. In order to delete the warping effect resulting from transparent soil and experiment setup, a modification for experiment results was performed. The bulging development process of the GESC and the displacement field of the surrounding soil were measured. By comparing with the existing experimental and theoretical results, it demonstrates that the model test system developed for studying the continuous bulging development of GESC is suitable. The current test results show that the bulging depth of GESC ranges from 1.05 to 1.40 times the diameter of GESC. The influence depth of GESC bulging on surrounding soil displacement is 0~3 the times diameter of GESC.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.145-147
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• 2009

The benefits of hydroforming technology are known as weight and cost savings through part consolidation and reduced post-forming processes such as welding and piercing. Hydroforming technology has some weaknesses in terms of process cycle times. But, as the hydraulic system and process designs are continuously developed, the cycle time is also reduced to acceptable and competitive levels. Hot air bulging is one of recently developed hydroforming techniques. Hot air bulging in order to further extend the forming degrees of Al lightweight material is investigated. A heated tube is placed in a heated die and sealed at the ends by sealing cylinders. The tube is subsequently expanded against the die cavity wall by internal pressure provided by air medium. The result of this study shows that axial feeding speed and air pressure have an effect on formability of Al air bulging at elevated temperature.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.271-278
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• 2008

A study has been conducted on the bulging process of liquid rocket engine nozzle which is essential to the manufacturing regenerative cooling combustion chamber. Mechanical properties of the material used for the bulging were experimentally obtained by tension tests. Deformation of the bulged nozzle was confirmed by a structural analysis. The developed bulging process and the deformation analysis result were confirmed by manufacturing of the bulged nozzle specimens and the bulging test. There has been a bulging failure among 7 bulged specimens due to the necking of the material. The cause of necking was investigated by comparing microstructure of the material. The investigation has revealed grain size of the material has considerable effect on the occurrence of the necking.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.100-105
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• 2001

The manufacturing of metal bellows consists of the four main forming processes, deep-drawing, ironing, tube bulging and folding. Among these, the bulging and folding processes are critically important because the quality of metal bellows is greatly influenced by the forming conditions of these processes. In the present study, the finite element analysis technique is applied to the bulging and folding processes to obtain information about the design parameters of a metal bellows.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1291-1292
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.251-252
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• 2011