• Journal of Biomedical Engineering Research
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• v.14 no.2
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• pp.155-162
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• 1993

The human's biomechanical structure keeps an optimal state by adapting the original biomechanical structure according to a change in the physical environment. This phenomenon is believed to be the main cause of loosening of the total hip replacement which is used widely in these days. In this study the bone density change due to artificial hip joint, which is generally believed as bone-remodeling, was investigated by the finite element method. For this, 2-D FEM models with 4 nodal point elements were constructed for intact and implanted cases. The density was calculated by comparing the relative amounts of effective stress for these two cases. In this way, calculated new density values were used in the next step as input values and this procedure repeated until convergence was obtained. Severe density change was detected at the femoral cortex of the proximal-medial side as expected. Moreover, following surprising result was found from this analysis. Titanium alloy prosthesis showed less density change compared to stainless steel prosthesis at earlier stage, however, almost same amount of the density change was detected at final stage. It was also found that other design parameters could not significantly affect its density change.

• Resources Recycling
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• v.29 no.5
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• pp.3-14
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• 2020

Magnesium is the third most abundant structural metal after aluminum and iron. Magnesium is the lightest metal in the common metals. It has a density 33 % less than aluminum and 77% lower than steel. However, the primary magnesium production process is highly energy intensive. The recycling of magnesium scrap reduces the energy consumption and environmental burden, comparing to the primary metal production. However, the amount of recovered metal from scrap is limited because of the difficulties to remove the impurities in the scrap. This work provides an overview of the magnesium production and recycling process.

• Steel and Composite Structures
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• v.25 no.6
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• pp.685-692
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• 2017

In this study, the effect of various adhesively bonded composite patches on mechanical properties of notched Al-Mg alloy plates was analyzed. For this purpose firstly, the un-notched and notched specimens were fabricated from 5086 Al-Mg alloys which have been used in armor-plated military vehicles. The surface notches as a flaw were machined with circular cutting tool to form notch aspect ratio a/c=0.15 and notch-to-thickness ratios a/t=0.5 in the radial direction on the test specimens. Then, various composite patches which reinforced by glass, carbon and Kevlar fibers were bonded adhesively at elliptically surface notches. Finally, experimental measurements conducted by applying tensile static loading. The experimental results showed that repairing with composite patches with order of carbon, glass and Kevlar fibers have remarkable effect on tensile strength of the notched plate. Also the finite element models were developed using Abaqus/Explicit code to predict the tensile strength and elongation of unrepaired notched specimen and specimen repaired by carbon fiber composite patch. The comparison between numerical and experimental results showed good agreement between them and proved the accuracy of numerical modeling.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.2 s.140
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• pp.142-150
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• 2005

Recently, the gas transportation system for CNG(Compressed Natural Gas) has been developed and several innovative approaches are presented from the aspects of commercial demand. In this study, a new type of 20ft container shape CNG tank with two and four cylinder intersections by using the intersecting spheres has been proposed. And the structural analysis of CNG tank with Mildsteel, API High Tensile Steel, Al-alloy and FRP has been carried out to compare the different types of pressure vessels of materials used. The analysis result shows that the proposed intersectional cylindrical type of CNG tank can be applied to the gas transportation system. And further study on the commercial analysis and associated equipments should be carried out for the practical applications.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.42-46
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• 2018

The subject of this study dealt with the structural safety analysis regarding the measured thrust test equipment as noted on a small engine. In this work, the structural design and analysis of steel and aluminum alloy structure for a small engine test of equipment were performed. Firstly, the structural design requirements of the engine test equipment were identified and investigated. After the structural design was reviewed, next the structural analysis of the engine test equipment was performed by the utilization of the finite element analysis method. The study was performed to determine that the stress and displacement analysis was appropriately managed regarding the applied load condition. As a result, it was determined that through the structural analysis, this study has confirmed that the designed engine test equipment is approved for safety, and meets its design purpose at this time.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.289-294
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• 2021

Tungsten (W) is used as a facing material for nuclear fusion reactors, and it is used in conjunction with structural materials such as copper alloy (CuCrZr), graphite, or stainless steel. On the other hand, since tungsten is a material with a high melting point, a method that can be manufactured at a lower temperature is important. Therefore, in this study, tungsten, which is a facing material, was attempted to be manufactured using a pressure sintering method. Material properties of sintered tungsten materials were analyzed for each solvent using two types of solvents, acetone and polyethylene glycol. The sintered tungsten material using acetone as a solvent exhibited a hardness value of about 255 Hv, and when polyethylene glycol was used, a hardness value of about 200 Hv was shown. The flexural strength of the sintered tungsten material was 870 MPa and 307 MPa, respectively, when acetone and polyethylene glycol were used as solvents. The sintered tungsten material using acetone as a solvent caused densification between particles, which served as a factor of increasing the strength.

• Steel and Composite Structures
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• v.31 no.2
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• pp.173-185
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• 2019

This paper presents experimental and numerical investigations of aluminum tubular members subjected to combined bending and web crippling. A series of tests was performed on square hollow sections (SHS) fabricated by extrusion using 6061-T6 heat-treated aluminum alloy. Different specimen lengths were tested to obtain the interaction relationship between moment and concentrated load. The non-linear finite element models were developed and verified against the experimental results obtained in this study and test data from existing literature for aluminum tubular sections subjected to pure bending, pure web crippling, and combined bending and web crippling. Geometric and material non-linearities were included in the finite element models. The finite element models closely predicted the strengths and failure modes of the tested specimens. Hence, the models were used for an extensive parametric study of cross-section geometries, and the web slenderness values ranged from 6.0 to 86.2. The combined bending and web crippling test results and strengths predicted from the finite element analysis were compared with the design strengths obtained using the current American Specification, Australian/New Zealand Standard and European Code for aluminum structures. The findings suggest that the current specifications are either quite conservative or unconservative for aluminum square hollow sections subjected to combined bending and web crippling. Hence, a bending and web crippling interaction equation for aluminum square hollow section specimens is proposed in this paper.

• Advances in materials Research
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• v.7 no.3
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• pp.195-201
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• 2018

High Strength low alloy steels containing various levels of C, Nb and Mn were used and for each of which, a simulated double thermal cycle was applied with the same first peak temperature and different second peak temperatures to produce HAZ microstructure corresponding to multi-pass weld. Effect of double cycle second temperature on the microstructure was observed and compared with single cycle results obtained from previous works, it was found that the percentage of martensite austenite constituent (MA) increases by Nb addition for all steels with the same Mn content and the increase in Mn content at the same Nb content shows an increase in MA area fraction as well. MA area fraction obtained for the double cycle is larger than that obtained for the single cycle for all steels used which imply that MA will have great role in the brittle fracture initiation for double cycle and the inter-pass temperature should be controlled for medium and high-carbon Mn steel to avoid large area fraction of MA. The beneficial effects of Niobium obtained in single pass weld were not observed for the double cycle or multi pass welds.

• Corrosion Science and Technology
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• v.20 no.2
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• pp.85-93
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• 2021

The corrosion damage of materials in marine environment mainly occurs by Cl^- ions due to the breakdown of passive films. Additionally, various characteristics in seawater such as salinity, temperature, immersion time, flow rate, and biological activity also affect corrosion characteristics. In this study, the corrosion characteristics of stainless steels (STS 304 and STS 316L) and anodized aluminum alloys (AA 3003 and AA 6063) were evaluated with seawater temperature parameters. A potentiodynamic polarization experiment was conducted in a potential range of -0.25 V to 2.0 V at open circuit potential (OCP). Corrosion current density and corrosion potential were obtained through the Tafel extrapolation method to analyze changes in corrosion rate due to temperature. Corrosion behavior was evaluated by measuring weight loss before/after the experiment and also observing surface morphology through a scanning electronic microscope (SEM) and 3D microscopy. Weight loss, maximum damage depth and pitting damage increased as seawater temperature increased, and furthermore, the tendency of higher corrosion current density with an increase of temperature attributed to an increase in corrosion rate. There was lower pitting damage and lower corrosion current density for anodized aluminum alloys than for stainless steels as the temperature increased.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2277-2288
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• 2021

To regulate the safety protocols in nuclear facilities, radioactive aerosols have been extensively researched to understand their health impacts. However, most measured particle-size distributions remain at low resolutions, with the particle sizes ranging from nanometer to micrometer. This study combines the high-resolution detection of 500 size classes, ranging from 6 nm to 10 ㎛, for aerodynamic diameter distributions, with a regional lung deposition calculation. We applied the new approach to characterize particle-size distributions of aerosols generated during the plasma arc cutting of simulated non-radioactive steel alloy wastes. The high-resolution measured data were used to calculate the deposition ratios of the aerosols in different lung regions. The deposition ratios in the alveolar sacs contained the dominant particle sizes ranging from 0.01 to 0.1 ㎛. We determined the distribution of various metals using different vapor pressures of the alloying components and analyzed the uncertainties of lung deposition calculations using the low-resolution aerodynamic diameter data simultaneously. In high-resolution data, the changes in aerosols that can penetrate the blood system were better captured, correcting their potential risks by a maximum of 42%. The combined calculations can aid the enhancement of high-resolution measuring equipment to effectively manage radiation safety in nuclear facilities.