• Journal of Welding and Joining
• /
• v.18 no.4
• /
• pp.38-47
• /
• 2000

Characteristics of the interface between tube and tube sheet which were formed by explosive expansion and roll expansion, have been studied in the research. The results are as follows: Optimum amounts of explosives for the expansion of Alloy 600 (19.05mm and 15.88mm) were found to be RDX 3.5-8.5g/m. Because explosive expansion caused les strain hardening and increased bounding strength, characteristics of the explosively expanded were better than those of mechanically expanded. As the transition region of the explosive expansion is inactive, the resistance to the stress corrosion cracking increases by 30∼40% compared to the roll and hydraulic expansion.

• Explosives and Blasting
• /
• v.17 no.4
• /
• pp.32-50
• /
• 1999

This study deals with interface charactristics of tube and tubesheet of the nuclear steam generator by the explosive expansion in order to take advantage of optimum expansion ratio, pull-out strength and leakage tightness and improvement of the resisitance on the stress corrosion cracking for low residual stress. The paper also show the relationship between roll, hydraulic and explosive expansion. The results obtain are as follows (1) Because of the explosive bonding is to use the high speed pressure and energy by the explosive, workability is good, bonding region is homogenous (2) Expansion ratio is 2.7%, Pull-out strength 850kg, Leakage strength $500kg/cm^2$. Clearance gap is 10~30mm in case of explosive expansion and interface structure of the tube and tubesheet is optimum condition. (3) As the transition region of the explosive expansion is inactive, the resistance of the stress corrosion cracking is increases 30~40% compare to the roll and hydraulic expansion.

• Explosives and Blasting
• /
• v.17 no.4
• /
• pp.18-31
• /
• 1999

The explosive forming has been used for many year to expand tubes into tubesheets. this process has demonstrated ability to direct carefully the energy of an explosive to expand tubes into tubesheet holes without damaging the tubesheet and without causing the excessive cold work at the tube I.D. that is normally associated with mechanical expansion. The success of explosive tube expansion provided the background for the development of the explosive tube plug. The main results are as follows : (1) The optimum explosives and explosive qualities are PETN, RDX, HMS and about 18~31gr/ft of explosive plugging in nuclear steam generator. (2) Explosive plugging's thickness is 0.9~1.8mm. If groove of 0.4 mm formed in plug outside, For the hydraulic leakage is go up, explosive plugging of formed groove are applicate tube and tubrplate. (3) Sheath is designed on the polyethylene of low density, In thermal impact test of the $430^\circ{C}$, hydraulic leakage is $300kg/cm^2$. (4) About 10~60mm oxide inclusions are existed on the space of explosive plug and tube protect to the leakage.

• Journal of Energy Engineering
• /
• v.22 no.2
• /
• pp.148-155
• /
• 2013

The steam generators of OPR-1000 plants have Alloy 600 and Alloy 690 as the tube material and its tube expansion method is the explosive expansion method. According to the experience of these plants, circumferential cracks were largely occurred in steam generator tubes expanded by the explosive expansion method and their locations were the outer surface of tube expansion transition region surrounding with piled-up sludge. But even though tubes have the same conditions, tubes with the hydraulic expansion method shows the prevail trend of axial cracks compared to circumferential cracks. Therefore in this study, in order to identify the difference of such phenomena as above, configurations of tube and tubesheet were modeled and at operating conditions, stress values applied in the tube expansion transition area in accordance with tube expansion methods were calculated by using computational program and the direction and the predominance of cracks were evaluated.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.5
• /
• pp.543-551
• /
• 2011

Steam generator tubes for nuclear power plants contain the local shape transitions on their inner or outer surface such as dent, bulge, over-expansion, eccentricity, deflection, and so on by the application of physical force during the tube manufacturing and steam generator assembling and by the sludge (that is, corrosion products) produced during the plant operation. The structural integrity of tubes will be degraded by generating the corrosive crack at that location. The profilometry using the traditional bobbin probes which are currently applied for measuring the profile change of tubes gives us basic information such as axial locations and average magnitudes of deformations. However, the three-dimensional quantitative evaluation on circumferential locations, distributional angle, and size of deformations will have to be conducted to understand the effects of residual stresses increased by local deformations on corrosive cracking of tubes. Steam generator tubes of Korean standard nuclear power plants expanded within their tube-sheets by the explosive expansion method and suffered from corrosive cracks in the early stage of power operation. Thus, local deformations of steam generator tubes at the top of tube-sheet were measured with an advanced rotating probe and a laser profiling system for the two cases where the tubes expanded by the explosive expansion method and hydraulic expansion. Also, the trends of eccentricity, deflection, and over-expansion of tubes were evaluated. The advanced eddy current profilometry was confirmed to provide accurate information of local deformations compared with laser profilometry.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.2
• /
• pp.145-151
• /
• 2017

As an alternative to conventional explosive methods for demolition of concrete structures and rocks, the use of non-explosive demolition agents can be considered to reduce noise, vibration, and dust emissions during the demolition process. In this study, we conduct finite element analysis for crack initiation and propagation caused by the expansion of non-explosive demolition agents in square concrete structures. The predicted crack patterns are compared with the experimental results in the literature. The minimum values of the required expansion pressure of non-explosive demolition agents are also estimated, which depend upon the arrangement of non-explosive demolition agents and empty holes. Furthermore, we investigate the effect of empty holes on the fragmentation of concrete structures, and discuss the effective arrangement of non-explosive demolition agents and empty holes for fragmentation improvement.

• Metals and materials international
• /
• v.24 no.6
• /
• pp.1327-1332
• /
• 2018

In this study, a novel approach to the explosive synthesis of titanium carbide (TiC) is discussed. Nonstoichiometric $TiC_x$ powder was produced via the underwater explosion of a Ti powder encapsulated within a spherical explosive charge. The explosion process, bubble formation, and synthesis process were visualized using high-speed camera imaging. It was concluded that synthesis occurred within the detonation gas during the first expansion/contraction cycle of the bubble, which was accompanied by a strong emission of light. The recovered powders were studied using scanning electron microscopy and X-ray diffraction. Submicron particles were generated during the explosion. An increase in the carbon content of the starting powder resulted in an increase in the carbon content of the final product. No oxide byproducts were observed within the recovered powders.

• Proceedings of the KWS Conference
• /
• 1996.05a
• /
• pp.34-37
• /
• 1996

The expanding method of tube to tubesheet joint part on neclear steam generators are classified into three classes of roller expanding, explosive expanding and hydraulic expanding. After the expanded Mock-Up specimen are made by the three expanding method. The general properties, microstructure/microvickers hardness, pull-out strength, hydraulic leak pressure, of tube to tubesheet joint part were inspected. and We evaluated the operation efficiency of expansion, reproduction of expanded joint about three expanding method. Through the overall evaluation of tube to tubesheet joint part, The hydraukic expanding and explosive expanding could be certificated more useful expanding method.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.1
• /
• pp.27-34
• /
• 2005

The present work has been developed the study of interpretation of separation behavior in gas expansion separation(GES) bolt which has the separation characteristics without fragmentation and minimum pyre-shock during the operation of the explosive bolt. In order to obtain the performance of minimum pyre-shock, the present work used non-compressive material instead of separation explosives. The use of the interpretation processor could be extensively helped to design the shape and the amount of explosives in the explosive bolt having complex geometry, and to analyse the separation behavior during the operation. It is also proved that the GES bolt is the most suitable the separation system necessary to minimum pyre-shock and non fragmentation compare with others.

• Explosives and Blasting
• /
• v.41 no.1
• /
• pp.19-31
• /
• 2023

There are various types of explosives, and each explosive has different characteristics such as water resistance, energy required for detonation, and crushing power, so understanding the characteristics of explosives is important for safe use and performance improvement. Computer simulation is used indirectly along with various experiments to understand the characteristics of explosives, and a state equation is used to express the explosive detonation process through computer simulation. In this study, the explanation of JWL EOS, which is mainly used among the state equations of explosives, and the cylinder expansion experiment to calculate the coefficient of JWL EOS were implemented as ANSYS AUTODYN and compared and analyzed with the actual experimental results. As a result, an error rate of around 20% occurred, and it was found that the overall change pattern of pressure and energy was consistent with the previously published experimental results.