• Journal of Ocean Engineering and Technology
• /
• v.13 no.2 s.32
• /
• pp.1-10
• /
• 1999

This study is concerned with the application of new criterion for membrane/shell mixed element in the rigid-plastic finite element analysis and elastic-plastic finite element analysis. The membrane/shell mixed element can be selctively adapted to the pure stretching condition by using membrane or a shell element in the bending effect areas. Thus, membrane/shell mixed element requires a efficient criterion for a distinction between membrane and shell element. In the present study introduce the criterion using the angle of between two element and confirm a generality of criterion from appling the theory to a rigid-plastic and elastic-plastic problems.

• Computers and Concrete
• /
• v.31 no.6
• /
• pp.469-484
• /
• 2023

The response mechanism of simply supported two-way reinforced concrete (RC) slabs under fire was numerically studied from the view of stress redistribution using the finite element software ABAQUS. Results show that: (1) Simply supported two-way RC slabs undergo intense stress redistribution, and their responses show four stages, namely elastic, elastic-plastic, plastic and tensile membrane stages. There is no cracking in the fire area of the slabs until the tensile membrane stage. (2) The inverted arch effect and tensile membrane effect improve the fire resistance of the two-way slabs. When the deflection is L/20, the slab is in an inverted arch effect state, and the slab still has a good deflection reserve. The deformation rate of the slab in the tensile membrane stage is smaller than that in the elastic-plastic and plastic stages. (3) Fire resistance of square slabs is better than that of rectangular slabs. Besides, increasing the reinforcement ratio or slab thickness improves the fire resistance of the slabs. However, an increase of cover thickness has little effect on the fire resistance of two-way slabs. (4) Compared with one-way slabs, the time for two-way slabs to enter the plastic and tensile cracking stage is postponed, and the deformation rate in the plastic and tensile cracking stage is also slowed down. (5) The simply supported two-way RC slabs can satisfy with the requirements of a class I fire resistance rating of 90 min without additional fire protection.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.36 no.6
• /
• pp.239-246
• /
• 2014

Many kinds of membrane have been used for the guided bone regeneration (GBR) technique. However, most membranes do not fulfill all requirements for the ideal membrane for the GBR technique. Among them, collagen membrane has been most widely used. However, its high price and weak tensile strength in wet condition are limitations for wide clinical application. Synthetic polymers have also been used for the GBR technique. Recently, silk based membrane has been considered as a membrane for the GBR technique. Despite many promising preclinical data for use of a silk membrane, clinical data regarding the silk membrane has been limited. However, silk based material has been used clinically as vessel-tie material and an electrospun silk membrane was applied successfully to patients. No adverse effect related to the silk suture has been reported. Considering that silk membrane can be provided to patients at a cheap price, its clinical application should be encouraged.

• Archives of Plastic Surgery
• /
• v.37 no.5
• /
• pp.509-518
• /
• 2010

Purpose: Major drawbacks of conventional bone marrow stromal cells (BSCs) transplantation method are mainly caused by direct transplanted cell to host cell interactions. We hypothesized that separation of the transplanted cells by a microporous membrane might inhibit most of the potential adverse effects and induce superior effect. The purpose of the study is to determine the optimal condition of the microporous membrane. Methods: First, BSCs were placed in polyethylene terephthalate (PET) transwell inserts with 3, 8, or $12{\mu}m$ pore size, and cultured in 24 well culture plates. After 5 days, bottoms of the plates were observed for presence of attached BSCs in monolayer and cell numbers were evaluated. Second, BSCs were placed PET, polycarbonate (PCT), and mixed cellulose esters (MCE) transwell inserts with 3 and $8{\mu}m$ pore size, and cultured in 24 well culture plates. After 3 days, the supernatants of the media left in culture plate were analyzed for collagen, vascular endothelial growth factor (VEGF), platelet derived growth factor BB (PDGF-BB), and basic fibroblast growth factor (bFGF). Third, BSCs were placed in 15% and 70% of the PET membrane with $3{\mu}m$ pore size. All the experimental conditions and methods were same as the second study. Results: The optimal pore sizes to prevent BSC leakage were $3{\mu}m$ and $8{\mu}m$. The amounts of type I collagen and three growth factors tested did not show significant differences among PET, PCT, and MCE groups. However, the collagen, VEGF, and bFGF levels were much higher in the high (70%) density group than in the low (15%) density group. Conclusion: This study revealed that the optimal pore size of membrane to prevent direct BSC to recipient cell contact is in between $3{\mu}m$ and $8{\mu}m$. Membrane materials and pore sizes do not influence the collagen and growth factor passage through the membrane. The most striking factor for collagen and growth factor transport is pore density of the membrane.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.7
• /
• pp.1738-1750
• /
• 1994

Both cylindrical cup drawing and square cup drawing are analyzed using membrane analysis as well as shell analysis by the elastic-plastic finite element method. An incremental formulation incorporating the effect of large deformation and normal anisotropy is used for the analysis of elastic-plastic non-steady deformation. The computed results are compared with the existing experimental results to show the validity of the analysis. Comparisons are made in the punch load and distribution of thickness strain between the membrane analysis and the shell analysis for both cylindrical and square cup drawing processes. In punch load, both analyses show very little difference and also show generally good agreement with the experiment. For the cylindrical cup deep drawing, the computed thickness strain of a membrane analysis, however, shows a wide difference with the experiment. In the shell analysis, the thickness strain shows good agrement with the experiment. For the square cup deep drawing, both membrane and shell analyses show a wide difference with experiment, this may be attributable to the ignorance of the shear deformation. Concludingly, it has been shown that the membrane approach shows a limitation for the deep drawing process in which the effect of bending is not negligible and more exact information on the thickness strain distribution is required.

• 한국가스학회:학술대회논문집
• /
• 2005.10a
• /
• pp.193-198
• /
• 2005

An investigation was made on the fatigue characteristics of type 304 stainless steel membrane manufactured by plastic working. To investigate the effect of plastic deformation, tests were performed with 5 types of specimens having different amount of plastic deformation. Fatigue tests were executed under both room and LNG temperatures ($-162^{\circ}C$). All the test results were compared with the fatigue data provided by RPIS(Recommended Practice for Inground LNG Storage Tank). On the basis of these results, it was confirmed that RPIS's design fatigue curve could be applied to evaluate fatigue lift of KOGAS membrane manufactured by pressing.

• Coupled systems mechanics
• /
• v.6 no.4
• /
• pp.501-522
• /
• 2017

This paper introduces a numerical procedure to incorporate elasto-plastic local deformation effects in the dynamic analysis of beams. The appealing feature is that simple beam type finite elements can be used for the global model which needs not to be altered by the localized elasto-plastic deformations. An overlapping local sophisticated 2D membrane model replaces the internal forces of the beam elements in the predefined region where the localized deformations take place. An iterative coupling technique is used to perform this replacement. Comparisons with full membrane analysis are provided in order to illustrate the accuracy and efficiency of the method developed herein. In this study, the membrane formulation is able to capture the elasto-plastic material behaviour based on the von Misses yield criterion and the associated flow rule for plane stress. The Newmark time integration method is adopted for the step-by-step dynamic analysis.

• Journal of the Korean Institute of Gas
• /
• v.9 no.4 s.29
• /
• pp.1-5
• /
• 2005

An investigation was made on the fatigue characteristics of type 304 stainless steel membrane manufactured by plastic working. To investigate the effect of plastic deformation, tests were performed with 5 types of specimens having different amount of plastic deformation. Fatigue tests were executed under both room and LNG temperatures $(-162^{\circ}C)$. All the test results were compared with the fatigue data provided by RPIS (Recommended Practice for Inground LNG Storage Tank). On the basis of these results, it was confirmed that RPIS's design fatigue curve could be applied to evaluate fatigue life of KOGAS membrane manufactured by pressing.

• Archives of Craniofacial Surgery
• /
• v.13 no.1
• /
• pp.46-49
• /
• 2012

Purpose: The forehead flap is the workhorse in nasal reconstruction, which provides a similar skin color, texture, structure, and reliability. There are some disadvantages, including donor site morbidities, 2- or 3-stage operations, and postoperative management after initial flap transfer. Furthermore, there has been little attention to the exposed raw surface wound, after the first stage of an operation. This article describes the authors' modification to overcome this problem, using artificial collagen membrane. Methods: An Artificial collagen membrane is composed of an outer silicone membrane and an inner collagen layer. After a forehead flap elevation, the expected raw surface was covered by an artificial collagen membrane with 5-0 nylon suture. A simple dressing, which had been applied to the site, was changed every 2 or 3 days in an outpatient unit. At 3 weeks postprocedure, a second stage operation was performed. Results: With biosynthetic protection of the raw surface, there were no wound problems, such as infection or flap loss. Thus, the patient was satisfied due to an effortless management of the wound and a reduction in pain. Conclusion: The application of an artificial collagen membrane to the raw under-surface of the flap could be a comfortable and a protective choice for this procedure.

• Journal of Korean Association for Spatial Structures
• /
• v.7 no.2 s.24
• /
• pp.35-44
• /
• 2007

The characteristics of elasto-plastic responses of a gymnasium building which is a steel braced frame with membrane roof is discussed as a basic research on the performance based seismic design of large span structures, in this paper. Under the strong earthquake motions, the formation of plastic hinges on braces attached by the bottom frame make reduce down the stresses and displacements of upper structures, and vertical acceleration of the membrane is tend to increase but maximum response of strain and corresponding stresses are tend to be reduced.