• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.138-144
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• 2013

The automation technology for overlay welding is needed due to the occurrence of severe corrosion and abrasion on the surface of internal contact in different shape of fittings. In Korea, different shapes of fittings have been manufactured by using the imported equipment of overlay welding automation at some companies. Thus the research on the development of overlay welding automation system (in short, OWAS) for a large L-type tube is urgently needed. In this paper, the investigation is focused on the optimal design of a supporting base for the (currently developing) OWAS of large L-type tube. Specifically we assume that the base which supports the equipment during the process of overlay welding is loaded as self-weight in the direction of gravity through static analysis especially when it is rotated 180 degree on the OWAS. For optimal design of a supporting base for OWAS of large L-type tube, Solidworks(R) (for 3-dimensional modelling) and ANASYS Workbench(R) (for structural analysis) are incorporated so as to proceed an optimization routines based on Response Surface Method (RSM) and Design of Experiment (DOE). In more specific, DOE finds out major factors (or dimensions) of the supporting base by using MINITAB(R). Then the regression equations between design variables (the major factors of supporting base) and response variables (deformation, stress and safety factor for the supporting base), which will be resulted in by RSM, verify the major factors of DOE. In the next step, Central Composite Design (CCD) plans 20 simulations of ANASYS Workbench(R) and then figures out the optimal values of design variables which will be reflected on the manufacturing of supporting base. Finally welding experiment is conducted to figure out the influence of overlay welding quality in applying the optimized design values of supporting base to the actual OWAS.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.299-307
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• 2007

In this study, a new concept for simulating a physical damage of tunnel shotcrete lining due to a long-term chemical deterioration has been proposed. It is known that the damage takes place mainly by internal cracks, reduction of stiffness and strength, which results mainly from volume expansion of the lining and corrosion of cement materials, respectively. This damage mechanism of shotcrete lining appears similar in most kinds of chemical reactions in tunnels. Therefore, the mechanical deterioration mechanism induced by a series of chemical reactions was generalized in this study and mathematically formulated in the framework of thermodynamics. The numerical model was implemented to a 3D finite element code, which can be used to simulate behaviour of tunnel structures undergoing external loads as well as chemical deterioration in time. A number of illustrative examples were given to show a feasibility of the model in tunnel designs.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.488-495
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• 2017

In this study, we conducted the kinetic hydration modeling of OPC and the final product according to the substitution ratio of GGBS by using the geochemical code, GEMS, in order to calculate the thermodynamic equilibrium. The thermodynamic data was used by GEMS's 3rd party database, Cemdata18, and the cement hydration model, the Parrot & Killoh model was applied to simulate the hydration process. In OPC modeling, ion concentration of pore solution and hydration products by mass and volume were observed according to time. In the GGBS modeling, as the substitution rate increases, the amount of C-S-H, which contributes the long-term strength, increases, but the amount of Portlandite decreases, which leads to carbonation and steel corrosion. Therefore, it is necessary to establish prevention of some deterioration.

• Steel and Composite Structures
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• v.33 no.1
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• pp.37-66
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• 2019

In cold-formed steel structures, such as trusses, wall frames and portal frames, the use of back-to-back built-up cold-formed stainless-steel lipped channels as compression members are becoming increasingly popular. The advantages of using stainless-steel as structural members are corrosion resistance and durability, compared with carbon steel. The AISI/ASCE Standard, SEI/ASCE-8-02 and AS/NZS do not include the design of stainless-steel built-up channels and very few experimental tests or finite element analyses have been reported in the literature for such back-to back cold-formed stainless-steel channels. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand (gAS/NZS) standards for built-up carbon steel sections only describe a modified slenderness approach, to consider the spacing of the intermediate fasteners. Thus, this paper presents a numerical investigation on the behavior of back-to-back cold-formed stainless-steel built-up lipped channels. Three different grades of stainless steel i.e., duplex EN1.4462, ferritic EN1.4003 and austenitic EN1.4404 have been considered. Effect of screw spacing on the axial strength of such built-up channels was investigated. As expected, most of the short and intermediate columns failed by either local-global or local-distortional buckling interactions, whereas the long columns, failed by global buckling. All three grades of stainless-steel stub columns failed by local buckling. A comprehensive parametric study was then carried out covering a wide range of slenderness and different cross-sectional geometries to assess the performance of the current design guidelines by AISI and AS/NZS. In total, 647 finite element models were analyzed. From the results of the parametric study, it was found that the AISI & AS/NZS are conservative by around 10 to 20% for cold-formed stainless-steel built-up lipped channels failed through overall buckling, irrespective of the stainless-steel grades. However, the AISI and AS/NZS can be un-conservative by around 6% for all three grades of stainless-steel built-up channels, which failed by local buckling.

• Biomedical Engineering Letters
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• v.8 no.4
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• pp.337-344
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• 2018

Additive manufacturing (AM) is an alternative metal fabrication technology. The outstanding advantage of AM (3D-printing, direct manufacturing), is the ability to form shapes that cannot be formed with any other traditional technology. 3D-printing began as a new method of prototyping in plastics. Nowadays, AM in metals allows to realize not only net-shape geometry, but also high fatigue strength and corrosion resistant parts. This success of AM in metals enables new applications of the technology in important fields, such as production of medical implants. The 3D-printing of medical implants is an extremely rapidly developing application. The success of this development lies in the fact that patient-specific implants can promote patient recovery, as often it is the only alternative to amputation. The production of AM implants provides a relatively fast and effective solution for complex surgical cases. However, there are still numerous challenging open issues in medical 3D-printing. The goal of the current research review is to explain the whole technological and design chain of bio-medical bone implant production from the computed tomography that is performed by the surgeon, to conversion to a computer aided drawing file, to production of implants, including the necessary post-processing procedures and certification. The current work presents examples that were produced by joint work of Polygon Medical Engineering, Russia and by TechMed, the AM Center of Israel Institute of Metals. Polygon provided 3D-planning and 3D-modelling specifically for the implants production. TechMed were in charge of the optimization of models and they manufactured the implants by Electron-Beam Melting ($EBM^{(R)}$), using an Arcam $EBM^{(R)}$ A2X machine.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.180-191
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• 2013

The purpose of this research was to find an optimal quarrying for marble by analyzing the applicability and the work efficiency of a chain saw machine newly introduced in the underground Baekwoon mine. From the test results of the physical properties of Baekwoon marble, which affects the efficiency of rock cutting, it was found to have similar physical characteristics as the ones which are now being produced in the other areas in Korea. And especially it shows isotropic property, which can be thought to be advantageous as a dimensional stone. To check the long-term quality of the marble as a stone material, several tests such as corrosion resistance test and abrasion test were carried out. It was found to be vulnerable to acid rain with decrease of weight and seismic wave velocity after applying artificial rain at pH 5.6 for 50 times. The percentage of wear from abrasion test was 22.67%. The working time and cutting speed of the chain saw machine were recorded and analyzed during the test-run at the quarry. The overall work cycle was assorted into 9 unit operations and the operating time per each unit was drawn. The operating times for the two cutting patterns, which could be possibly applicable to the work site, were compared. The results indicated that the pattern B, that the cutting sequence was set to minimize the movement of the machine, showed 6% less working hours than the pattern A, which first cuts the outer boundary. With cutting pattern analysis, the ore body in the Baekwoon mine was 3 dimensionally modeled and a quarrying plan considering the existing conditions of the marble was suggested.