• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2006.06b
• /
• pp.285-290
• /
• 2006

As an alternative method to solve air pollution problem and difficulty of pulp bleaching of kraft pulping process, NaOH-Urea pulping was applied. The properties of NaOH-Urea pulp were compared to those of NaOH and kraft pulps. Addition of urea in low alkali charges retarded delignification rate compared to NaOH pulping. But, in high alkali application, delignification was significantly enhanced not from the addition of urea but from the high alkalinity. It was disclosed that urea did not participate on delignification reaction by the experiment using lignin model compound. Compared to paper strengths at the same level of sheet density, NaOH-Urea pulp gave as almost same breaking length and tensile index as those of kraft pulp. Especially tensile energy absorption and burst index were higher than those of kraft pulp.

• Elastomers and Composites
• /
• v.57 no.4
• /
• pp.165-174
• /
• 2022

The effect of fumed silica loading on the thermal stability and mechanical properties of fluorosilicone (FVMQ) rubber was investigated. The distribution of fumed silica inside FVMQ was characterized using scanning electron microscopy, and the thermal stability of composites was evaluated using thermogravimetric analysis and by the changes in mechanical performance during thermo-oxidative aging. The function mechanism of fumed silica was studied by Fourier transform infrared spectroscopy. The results show that with increasing silica content, the crosslink density of composites, the modulus at 100%, and tensile strength also increased, whereas the elongation at break decreased. Furthermore, increasing the silica content of composites increased the initial decomposition temperature (T_d) and residual weight of the composite after exposure to nitrogen. In addition, the thermal oxidative aging experiment demonstrated improved aging resistance of the FVMQ composites, including lower change in tensile strength, elongation at break, and modulus at 100%.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.18 no.2
• /
• pp.61-68
• /
• 2022

Accurate evaluation of residual stress is important for stress corrosion cracking assessment. In this paper, electron beam welding experiment is simulated via finite element analysis and the sensitivity of the parameters related to the combined heat source model is investigated. Predicted residual stresses arecompared with measured residual stresses. It is found that the welding efficiency affects the size of the tensile residual stress area and the magnitude of maximum longitudinal residual stress. It is also found that the parameter related to the ratio of energy distributed to the two-dimensional heat source has little effect on the size of tthe tensile residual stress area, but affects the size of the longitudinal residual stress in the center of the weld.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.32 no.2
• /
• pp.87-92
• /
• 2019

In this paper, we have verified a low-voltage EM(elasto-magnetic) sensing technique for tensile force management of PSC(prestressed concrete) internal tendon in order to apply the technique to actual construction sites where stable power supply is difficult. From observation of past domestic and overseas PSC structural accident cases, it was found that PS tension is very important to maintain structural stability. In this paper, we have tried to measure the tensile force from a magnetic hysteresis curve through EM sensors according to voltage value by using relation between magnetostriction and stress of ferromagnetic material based on elastic-magnetic theory. For this purpose, EM sensor of double cylindrical coil type was fabricated and tensile force test equipment for PS tendon using hydraulic tensioning device was constructed. The experiment was conducted to confirm relationship between changes of permeability and tensile force from the measurement results of the maximum / minimum voltage amount. The change of magnetic hysteresis curve with magnitude of tensile force was also measured by reducing amount of voltage step by step. As a result, the slope of estimation equation in accordance with magnitude of magnetic field decreases with the voltage reduction. But it was confirmed a similar pattern of change of magnetic permeability for the magnetic hysteresis loop. So, in this study, it is considered that it is possible to manage the tensions of PSC internal tendon using EM sensing technique in low-voltage state.

• International journal of advanced smart convergence
• /
• v.4 no.1
• /
• pp.145-153
• /
• 2015

Friction Stir Welding (FSW) is a solid state welding that could successfully weld the difficult-to-weldmaterials such as an aluminum alloy. In this welding process, the stirrer of the welding tool is one of the important factors for producing the perfect sound joint that indicates the higher joint strength. So, this report aims to apply the friction stir welding using various stirrer geometries to weld the AA6063-T1 aluminum alloy butt joint, investigates the mechanical properties of the joint and then compares the mechanical properties with the microstructure of the joint. An experiment was started by applying the friction stir welding process to weld a 6.3 mm thickness of AA6063-T1 aluminum alloy butt joint. A study of the stirrer geometries effect such as a cylindrical geometry, a cone geometry, a left screw geometry and a right screw geometry at a rotational speed of 2000 rpm and a welding speed of 50-200 mm/min was performed. The mechanical properties such as a tensile strength and a hardness of the joint were also investigated and compared with the microstructure of the joint. The results are as follows. A variation of FSW Stirrer shape directly affected the quality AA6063-T1 aluminum alloy butt joint. A cylindrical stirrer shape and a cone stirrer shape produced the void defect at the bottom part of the weld metal and initiated the failure of the joint when the joint was subjected to the load during the tensile test. Left and right screw stirrer shapes gave the sound joint with no void defect in the weld metal and affected to increase the joint strength that was higher than that of the aluminum base metal.

• The korean journal of orthodontics
• /
• v.22 no.3 s.38
• /
• pp.557-578
• /
• 1992

Heat treatment which removes internal stress enhances the mechanical properties of the orthodontic arch wire. The main purpose of this experiment was to investigate the effects of the heat treatment on the mechanical properties of the Elgiloy wire. The Elfiloy wire, 0.016' X 0.022' and 0.018' X 0.025', were heat treated in an electric oven for 5, 10 and 15 minutes at selected temperatures between 300 and $900^{\circ}C$. Tensile strength and load deflection rate were measured to reveal the changes of mechanical property at various conditions, and each specimen was observed under metallurgic microscope. Also to trace the precipitation material due to overheat treatment, a qualitative analysis was carried out with EDS system. It was found that heat treatment at a low temperature caused an increase in the tensile strength and bending resistance, and a maintenance in the fibrous in the tensile strength and bending resistance, and a maintenance in the fibrous structure of both sizes of wire. The changes observed in properties and appearance were probably due to the relief of internal stresses incurred in the metal during cold working. In both sizes of wire the tensile strength and the bending resistance continued to decrease at high temperature, and the fibrous structure continued to disappear then was not observed at $900^{\circ}C$. The carbide precipitation founded in grain boundary at $750^{\circ}C$ probably was other elements carbide (Ni, Co) except Cr. The grain growth was observed at $1100^{\circ}C$. Optimum heat treatment for the 0.016' X 0.022' Elgiloy wire was 10 minutes at $500^{\circ}C$, and for the 0.018' X 0.025' Elgiloy wire it was 5 to 15 minutes at $500^{\circ}C$.

• Steel and Composite Structures
• /
• v.21 no.5
• /
• pp.1031-1043
• /
• 2016

Optimization of the construction scheme of the cable-strut tensile structure based on error sensitivity analysis is studied in this paper. First, the element length was extracted as a fundamental variable, and the relationship between element length change and element internal force was established. By setting all pre-stresses in active cables to zero, the equation between the pre-stress deviation in the passive cables and the element length error was obtained to analyze and evaluate the error effects under different construction schemes. Afterwards, based on the probability statistics theory, the mathematical model of element length error is set up. The statistical features of the pre-stress deviation were achieved. Finally, a cable-strut tensile structure model with a diameter of 5.0 m was fabricated. The element length errors are simulated by adjusting the element length, and each member in one symmetrical unit was elongated by 3 mm to explore the error sensitivity of each type of element. The numerical analysis of error sensitivity was also carried out by the FEA model in ANSYS software, where the element length change was simulated by implementing appropriate temperature changes. The theoretical analysis and experimental results both indicated that different elements had different error sensitivities. Likewise, different construction schemes had different construction precisions, and the optimal construction scheme should be chosen for the real construction projects to achieve lower error effects, lower cost and greater convenience.

• The Journal of Korean Academy of Prosthodontics
• /
• v.40 no.4
• /
• pp.386-395
• /
• 2002

This study would like to measure and compare water sorption and solubility of acrylic resins, with 3 different polymerizing methods, and tensile strength between denture base resin and relining rosins. For this experiment, 3 different acrylic resins were used; heat polymerizing resin: Vertex (Dentmex, Zeist, Holland), autopolymerizing resin: Tokuso Rebase (Tokuyama Corp, Tokyo, Japan), and light curing resin: Mild Rebaron LC(GC Corp, Tokyo, Japan) The results were as follows ; 1. Tokuso Rebase showed the lowest water sorption. followed by Mild Rebaron LC and Vertex. Among resins, there were some signigicant differences (P<0.05). 2. Vertex showed the lowest solubility, followed by Mild Rebaron LC and Tokuso Rcbase. Among resins, there were some signigicant differences (P<0.05). 3. Intact Vertex showed the highest tensile strength, and Mild Rebaron LC had a more tensile strength than Tokuso Rebase. Between Vertex and the other resins, there were some signigicant differences (P<0.05) However, between Mild Rebaron LC and Tokuso Rebase, there was no statistical difference (P>0.05). About 50% of Rebaron LC showed cohesive fracture. 4. Tensile strength has more decreased after thermocycling than before, but there was no statistical difference (P>0.05).

• Journal of Korean Society of Steel Construction
• /
• v.18 no.3
• /
• pp.395-403
• /
• 2006

Recently constructed bridges often have long spans and simple structure details considering not only the function but other important factors such as aesthetics, maintenance, construction duration and life cycle cost. Therefore, bridges require high-performance steels like extra-thick plate steels and thermo-mechanical control process (TMCP) steels. TMCP stels are now gaining wide attention due to their weldability improved strength and toughness. Recently, SM570-TMC steel, which is a high-strength TMCP steel with a tensile strength of 600 MPa, has been developed and applied to steel structures. However, using this steel in building steel structures requires the elucidation of not only material characteristics but also the mechanical characteristic of welded joints. In this study, high-temperature tensile properties of SM570-TMC steel were investigated through the elevated temperature welded joints of SM570-TMC steel were studied through the three-dimensional thermal elasticplastic analyses on the basis of mechanical properties at high temperatures obtained from the experiment.

• Structural Engineering and Mechanics
• /
• v.43 no.6
• /
• pp.823-833
• /
• 2012

An experimental method was suggested for obtaining fracture toughness ($K_{Ic}$) and the tensile strength (${\sigma}_t$) of chopped strand glass fiber reinforced polymer concretes (PC). Semi-circular bend (SCB) specimens subjected to three-point bending were used for conducting the experiments on the PC material. While the edge cracked SCB specimen could be used to evaluate fracture toughness, the tensile strength was obtained from the un-cracked SCB specimen. The experiments showed the practical applicability of both cracked and un-cracked SCB specimens for using as suitable techniques for measuring $K_{Ic}$ and ${\sigma}_t$ in polymer concretes. In comparison with the conventional rectangular bend beam specimen, the suggested SCB samples need significantly less material due to its smaller size. Furthermore, the average values of ${\sigma}_t$ and $K_{Ic}$ of tested PC were approximately 3.5 to 4.5 times the corresponding values obtained for conventional concrete showing the improved strength properties of PC relative to the conventional concretes.