• Journal of the Korean Wood Science and Technology
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• v.45 no.2
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• pp.139-146
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• 2017

This study was conducted to develop a new drying technology in order to quickly and massively dry bamboo tubes without crack and check. The bamboo tubes with the diameter of 45 mm - 68 mm had been impregnated in the solution of PEG-1000, and then were dried under room temperature and high temperature, respectively. The cracks occurred on all control specimens while no cracks were found on PEG treated specimens during drying at room temperature due to effect of PEG restraining the circumferential shrinkage of bamboo tube. But the drying period of this method was too long (200 days) compared to 10 hours of kiln drying. During fast high temperature drying, cracks occurred on all control specimens, but no cracks were found on PEG treated specimens, which could be accounted for more solidified PEG due to higher drying temperature and faster drying rate, and the tension set formed on the surface of bamboo tube in the early stage of drying owning to high drying temperature and low relative humidity. Thus, it is advised that PEG treated bamboo tube should be fast dried at high temperature in order to not only prevent crack or check in short drying period but also increase the dimensional stability of the products made of bamboo tubes.

• Computers and Concrete
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• v.11 no.2
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• pp.123-148
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• 2013

The nonlinear finite element method with eight noded isoparametric quadrilateral element for concrete and two noded element for reinforcement is used for the prediction of the behavior of reinforcement concrete structures. The disturbed state concept (DSC) including the hierarchical single surface (HISS) plasticity model with associated flow rule with modifications is used to characterize the constitutive behavior of concrete both in compression and in tension which is named DSC/HISS-CT. The HISS model is applied to shows the plastic behavior of concrete, and DSC for microcracking, fracture and softening simulations of concrete. It should be noted that the DSC expresses the behavior of a material element as a mixture of two interacting components and can include both softening and stiffening, while the classical damage approach assumes that cracks (damage) induced in a material treated acts as a void, with no strength. The DSC/HISS-CT is a unified model with different mechanism, which expresses the observed behavior in terms of interacting behavior of components; thus the mechanism in the DSC is much different than that of the damage model, which is based on physical cracks which has no strength and interaction with the undamaged part. This is the first time the DSC/HISS-CT model, with the capacity to account for both compression and tension yields, is applied for concrete materials. The DSC model allows also for the characterization of non-associative behavior through the use of disturbance. Elastic perfectly plastic behavior is assumed for modeling of steel reinforcement. The DSC model is validated at two levels: (1) specimen and (2) practical boundary value problem. For the specimen level, the predictions are obtained by the integration of the incremental constitutive relations. The FE procedure with DSC/HISS-CT model is used to obtain predictions for practical boundary value problems. Based on the comparisons between DSC/HISS-CT predictions, test data and ANSYS software predictions, it is found that the model provides highly satisfactory predictions. The model allows computation of microcracking during deformation leading to the fracture and failure; in the model, the critical disturbance, Dc, identifies fracture and failure.

• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.811-818
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• 2009

In order to meet increasingly complex and rigorous technical specifications, extensive effort has been devoted to fabricate clad materials with multi-layered metal plates. In this study, novel stainless steel/aluminum/copper (STS/Al/Cu) three-ply clad materials were fabricated by a hot rolling process for cookware applications. The effect of the testing temperature on the mechanical properties of the clad materials and on each component metal was investigated during the tensile tests. The interface properties of the clad materials were also examined by optical microscopy (OM) and an electron probe micro-analyzer (EPMA). The best mechanical and interfacial properties for a warm working process were found in a sample annealed at a temperature of $300^{\circ}C$. For the sample annealed at $400^{\circ}C$, the results of the tensile test indicated that interface delamination occurred only in the region of the Al/Cu interfaces. This was due to the formation of the thick and brittle intermetallic compound of $Al_2Cu$ in the Al/Cu interface. In contrast, no interface delamination was observed in the STS/Al interface, most likely due to its strong bond strength.

• Composites Research
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• v.17 no.5
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• pp.1-6
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• 2004

Composite pressure vessels with HDPE (high density polyethlyne) liner with metal boss at each end were developed by Filament Winding Process. The vessel is composed of a dome-shaped part at each end and a cylinder-shaped part at the middle of the vessel. The environmental tests carried out for possible vessel materials such as High Density Polyethlyn (HDPE), resins and reinforcing fibers up to a year showed no significant damages. The boss was designed to minimize the gas leak which was verified by FEM analysis. Most ideal fiber tension was obtained by experimental method and the fiber volume fraction, $\textrm{V}_{f}$, obtained by image analyzer were 55.4 % in cylinder and 55.6 % in dome parts, respectively. Winding pattern is programmed to control the composite thickness in the dome areas such that the failure of the vessel may occur in the cylinder. During the cure, the vessel was rotated and a constant internal pressure of 0.62 bar was applied. From this, the vessel's burst pressure is improved by 28 %. The burst and fatigue tests for under-wound and fully wound vessel showed satisfactory results.

• Journal of Chest Surgery
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• v.42 no.2
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• pp.165-174
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• 2009

Background: With the advances of cardiac surgery, the demand for an artificial prosthesis has increased, and this has led to the development and utilization of diverse alternative materials. We conducted this research to improve an artificial prosthesis by examining the changes of the physical qualities, the pressure related tensile strength, the change in elasticity and the thermostability of a xenograft valve (porcine) and pericardium (bovine, porcine) based on the type of fixation liquid we used. Material and Method: The xenograft valves and pericardium were assigned into three groups: the untreated group, the fixed with glutaraldehyde (GA) group and the glutaraldehyde with GA+solvent such as ethanol etc. group. The surgeons carried out each group's physical activities. Each group's uniaxial tension and elasticity was measured and compared. Thermostability testing was conducted and compared between the bovine and porcine pericardium fixed with GA group and the GA+solvent group. Result: On the physical activity test in the surgeon's hand, no significant difference between the groups was sensed on palpation. For suture and tension, the GA+solvent group was slightly firmer than the low GA concentration group. In general, the circumferential uniaxial tension and elasticity of the porcine aortic and pulmonary valves were better in the fixed groups than that in the untreated group. There was no significant difference between the GA and GA+solvent groups (p>0.05). Bovine and porcine pericardium also showed no significant difference between the GA group and the GA+solvent group (p>0.05). When comparing between the groups for each experiment, the elasticity tended to be stronger in most of the higher GA concentration group (porcine pulmonary valve, porcine pericardium). On the thermostability testing of the bovine and porcine pericardium, the GA group and the G+solvent group both had a sudden shrinking point at $80^{\circ}C$ that showed no difference (bovine pericardium: p=0.057, porcine pericardium: p=0.227). Conclusion: When fixing xenograft prosthetic devices with GA, adding a solvent did not cause a loss in pressure-tension, tension-elasticity and thermostability. In addition, more functional solvents or cleansers should be developed for developing better xenografts.

• Clinics in Shoulder and Elbow
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• v.16 no.1
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• pp.33-39
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• 2013

Purpose: The aim of this study is to evaluate the clinical result of intra-articular fractures of the distal humerus (AO type C) in elderly osteoporotic patients treated with double tension band osteosynthesis. Materials and Methods: From January 2006 to December 2010, 10 elderly osteoporotic patients(1 male, 9 females) with intra-articular fractures of the distal humerus (AO type C) were treated with double tension band osteosynthesis. The mean age of patients at the time of surgery was 74.6(66~84) years and the mean follow-up period was 39.2(20~74) months. The fracture union and complications were assessed and the functional result was evaluated by the rating system of Jupiter et al. and the Mayo elbow performance index. Results: Bone union was achieved in all patients with no secondary displacement. The mean time for union was 16.6(13~22) weeks. The average postoperative arc of elbow flexion was 119(100~140) degrees with a mean flexion contracture of 8.5(0~15) degrees. The recovery in two patients was rated as excellent, in 7 as good, and in 1 as fair in terms of the Mayo elbow performance index with average value of 82(70~90) points. Seven patients were rated as excellent, 1 as good, and 2 as fair in terms of the rating system of Jupiter et al. Changing tension band wiring was performed in one patient as skin irritation was noticed due to tension band knots. Heterotopic ossification developed in one patient but had no symptom. Conclusion: Double tension band osteosynthesis in intra-articular fractures of distal humerus (AO type C) in elderly osteoporotic patients can provide sufficient and secure stability to allow early rehabilitation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.823-826
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• 2000

Burr formed in drilling are classified into three types. no burr, burrs with cap, teared burr. To control burr size in drilling. the second type burrs with cap are to be formed because it is small and uniform. It is necessary to understand the mechanism of cap formation to derive the burr formation into second type burr with cap. In several materials, second type burrs are formed in drilling by changing cutting conditions. It is observed that cap is formed as a result of the plastic deformation along the outside of exit hole. According to the tension behavior of the material in concentrated region between hole and drill outside edge, the geometry of burr with cap is determined.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.40-48
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• 1997

There are many research results as individual uni-axial tension creep test of heat-resisting materials. However, there are very few about the study on the high temperature creep test for the Initial Strain Method, and especially any study on it about the friction welded joints of SUH3 to SUH35. One of the important concerns is a reliable method of evaluating static creep properties. No reliable method seems available at present to evaluate or predict static creep properties. So, the reliable method to evaluate and predict them by the ISM and AE techniques was made.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.200-207
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• 2001

Burrs farmed in drilling are classified into three types, no burr, burrs with cap, teared burr. To control burr size in drilling, the second type burrs with cap are to be formed because it is small and uniform. It is necessary to understand the mechanism of cap formation to derive the burr formation into second type burr with cap. In several materials. second type burrs are formed in drilling by changing cutting conditions. It is observed that cap is formed as a result of the plastic deformation along the outside of exit hope. According to the tension behavior of the material in concentrated region between hole and drill outside edge, the geometry of burr with cap is determined. Simplified 2D FEM analysis shows good prediction for burr formation.

• Journal of Korean Association for Spatial Structures
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• v.22 no.2
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• pp.47-55
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• 2022

In this study, we focus on the feasibility of structural topology optimization for a steel-timber composite beam design of optimally allocating glue-laminated timbers into a web with openings under the condition of given steel flanges. The motivation of this study is to topologically take maximal stiffness harmonizing both tension and compression performance of the steel-timber composite beam and become the eco-frandly timber design for buidling members. As a result of this study, the key web-openings allocation becomes triangle spaces, i.e., empty or no materials, of optimal topologies of both a pure timber plate and a steel flange-web timber plate without web-openings. Several applicable examples verify the effectiveness of topology optimization for steel-timber beams with web-openings.