• Journal of the Korean Institute of Gas
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• v.26 no.1
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• pp.27-33
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• 2022

As the scale of explosions diversifies along with the expansion of gas handling and storage facilities, studies on explosion-proof facilities in preparation for accidents is being actively conducted. The gastight door blocks the expansion pressure caused by blast waves or internal fires, and at the same time protects the personnel and equipment inside. For gastight doors, the regulations related to explosion-proof design are not clearly presented, and studies on the explosion pressure resistance performance evaluation of the facility are insufficient. In this study, the gastight door was modeled in a 3D shape with reference to the regulation ASTM regarding the gastight door standard. Afterwards, evaluation for blast-resistant performance of gastight door using Numerical simulation was evaluated by using ANSYS Explicit Dynamics to compare the deformation.

• Transactions of Materials Processing
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• v.31 no.4
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• pp.214-228
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• 2022

The yield criterion, or called yield function, plays an important role in the study of plastic working of a sheet because it governs the plastic deformation properties of the sheet during plastic forming process. In this paper, we propose a novel anisotropic yield function useful for describing the plastic behavior of various anisotropic sheets. The proposed yield function includes the anisotropic version of the second stress invariant J₂ and the third stress invariant J₃. The anisotropic yield function newly proposed in this study is as follows. F(J₂)+ αG(J₃)+ βH (J₂ × J₃) = k^m The proposed yield function well explains the anisotropic plastic behavior of various sheets by introducing the parameters α and β, and also exhibits both symmetrical and asymmetrical yield surfaces. The parameters included in the proposed model are determined through an optimization algorithm from uniaxial and biaxial experimental data under proportional loading path. In this study, the validity of the proposed anisotropic yield function was verified by comparing the yield surface shape, normalized uniaxial yield stress value, and Lankford's anisotropic coefficient R-value derived with the experimental results. Application for the proposed anisotropic yield function to aluminum sheet shows symmetrical yielding behavior and to pure titanium sheet shows asymmetric yielding behavior, it was shown that the yield curve and yield behavior of various types of sheet materials can be predicted reasonably by using the proposed new yield anisotropic function.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.38-44
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• 2022

As the supply of hydrogen charging stations for hydrogen supply accelerates due to the hydrogen economy revitalization policy, the risk of accidents is also increasing. Since most hydrogen explosion accidents lead to major accidents, it is very important to secure safety when using hydrogen energy. In order to utilize hydrogen energy, it is essential to secure the safety of hydrogen storage containers used for production, storage, and transportation of liquid hydrogen. In this paper, in order to evaluate the structural safety of a hydrogen-filled pressure vessel, the behavioral characteristics of gas pressure were analyzed by finite element analysis. SA-372 Grade J / Class 70 was used for the material of the pressure vessel, and a hexahedral mesh was applied in the analysis model considering only the 1/4 shape because the pressure vessel is axisymmetric. A finite element analysis was performed at the maximum pressure using a hydrogen gas pressure vessel, and the von Mises stress, deformation, and strain energy density of the vessel were observed.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.265-281
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• 2022

A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.148-154
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• 2022

As the 4th industrial age approaches, the demand for semiconductors is increasing enough to be used in all electronic devices. At the same time, semiconductor technology is also developing day by day, leading to ultraprecision and low power consumption. Semiconductors that keep getting smaller generate heat because the energy density increases, and the generated heat changes the shape of the semiconductor package, so it is important to manage. The temperature change is not only self-heating of the semiconductor package, but also heat generated by external damage. If the package is deformed, it is necessary to manage it because functional problems and performance degradation such as damage occur. The package burn in test in the post-process of semiconductor production is a process that tests the durability and function of the package in a high-temperature environment, and heat dissipation performance can be evaluated. In this paper, we intend to review a new material formulation that can improve the performance of the adapter, which is one of the parts of the test socket used in the burn-in test. It was confirmed what characteristics the basic base showed when polyamide, a high-molecular material, and alumina, which had high thermal conductivity, were mixed for each magnification. In this study, functional evaluation was also carried out by injecting an adapter, a part of the test socket, at the same time as the specimen was manufactured. Verification of stiffness such as tensile strength and flexural strength by mixing ratio, performance evaluation such as thermal conductivity, and manufacturing of a dummy device also confirmed warpage. As a result, it was confirmed that the thermal stability was excellent. Through this study, it is thought that it can be used as basic data for the development of materials for burn-in sockets in the future.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.3
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• pp.104-114
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• 2022

The purpose of using coolant in machining is both to increase a tool life and also to prevent product deformation and thus, stabilize the surface quality by lubricating and cooling the tool and the machining surface. However, a very small amount of cutting mist should be used because chlorine-based extreme pressure additives are used to generate environmental pollutants in the production process and cause occupational diseases of workers. In this study, medical titanium alloy (Ti-6Al-7Nb) was subjected to a processing experiment by selecting factors and levels affecting cutting power in the processing of the Aerosol Dry Lubrication (ADL) method using vegetable oil. The machining shape was a slot to sufficiently reflect the effect of the cutting depth. As for the measurement of cutting force, the trend of cutting characteristics was identified through complete factor analysis. The factors affecting the cutting force of ADL slot processing were identified using the reaction surface analysis method, and the characteristics of the cutting force according to the change in factor level were analyzed. As the cutting speed increased, the cutting force decreased and then increased again. The cutting force continued to increase as the feed speed increased. The increase in the cutting depth increased the cutting force more significantly than the increase in the cutting speed and the feed speed. Through the reaction surface analysis method, the regression equation for predicting cutting force was identified, and the optimal processing conditions were proposed. The cutting force was predicted from the secondary regression equation and compared with the experimental value.

• Structural Engineering and Mechanics
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• v.86 no.2
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• pp.167-180
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• 2023

This work applies a four-known quasi-3D shear deformation theory to investigate the bending behavior of a functionally graded plate resting on a viscoelastic foundation and subjected to hygro-thermo-mechanical loading. The theory utilizes a hyperbolic shape function to predict the transverse shear stress, and the transverse stretching effect of the plate is considered. The principle of virtual displacement is applied to obtain the governing differential equations, and the Navier method, which comprises an exponential term, is used to obtain the solution. Novel to the current study, the impact of the viscoelastic foundation model, which includes a time-dependent viscosity parameter in addition to Winkler's and Pasternak parameters, is carefully investigated. Numerical examples are presented to validate the theory. A parametric study is conducted to study the effect of the damping coefficient, the linear and nonlinear loadings, the power-law index, and the plate width-tothickness ratio on the plate bending response. The results show that the presence of the viscoelastic foundation causes an 18% decrease in the plate deflection and about a 10% increase in transverse shear stresses under both linear and nonlinear loading conditions. Additionally, nonlinear loading causes a one-and-a-half times increase in horizontal stresses and a nearly two-times increase in normal transverse stresses compared to linear loading. Based on the article's findings, it can be concluded that the viscosity effect plays a significant role in the bending response of plates in hygrothermal environments. Hence it shall be considered in the design.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.165-172
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• 2006

This study describes a series of model tests on instrumented pile groups embedded in HAP-CHEN sand undergoing lateral movement. We tried to find the effect of group piles dependent on a number of factors, including the position of the pile in a group, the pile spacing, and the pile arrangement. The results of test are as follows. For the group piles, the bending moment profile for each pile is similar in shape to that of single pile, although the magnitude and the position of the maximum bending moment are different. $R_M$ (the ratio of maximum bending moment) and $R_F$ (the ratio of resistance to lateral soil movement) were found to increase with increasing pile spacing. When a pile is in a group under lateral soil movement, RM increased in the order of the middle row, front row, back row, according to the direction of lateral deformation, and the outer pile has a larger RM than the inner pile.

• Composites Research
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• v.21 no.3
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• pp.9-17
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• 2008

In this paper, the low velocity impact characteristics of filament winding CFRP pressure vessel was investigated using numerical and experimental methods. The cylinder part of CFRP vessel was impacted using triangular shape impactor which simulated the sharp edge of dropping tools and impact response behavior of CFRP was reviewed. The mechanical behavior, such as deformation and stress distribution, were also predicted by explicit finite element method and the validity of the model was investigated. For the quantitative evaluation of the residual strength of the pressure vessel after impact, a series of the ring specimens was cut from the impacted vessel and its burst pressure was measured by hydraulic pressure hoop tension test. As the results, the relationship between the residual strength degradation and the impact energy was successively obtained and a useful methodology to evaluate quantitatively the impact damage tolerance of CFRP pressure vessel was established.

• Composites Research
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• v.19 no.1
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• pp.15-21
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• 2006

It is very difficult to make complex 3 dimensional curved-shape composite laminates using the advanced unidirectional composite prepregs. This study shows development process of subscale composite parabolic antenna reflector using unidirectional AS4/PEEK prepreg tapes. The AS4/PEEK thermoplastic composite materials are known to have good thermal and chemical stabilities in addition to their high specific strength and modulus. Various lamination methods were investigated through finite element analyses to make up the laminate design of the reflector. The automated fiber placement method was used to fabricate the reflector. The thermal expansion test using full-bridge strain gage circuits was done to verity the performance of the composite product.