• Transactions of Materials Processing
• /
• v.4 no.3
• /
• pp.245-256
• /
• 1995

SMC(Sheet Molding Compound), a thermoset composite material which consists of unsaturated polyester resin, fiberglass strands, fillers, and various chemical additives for curing agent, has been widely used in fabrication of structural components. The mechanical properties of molded SMS parts are strongly dependent on material flow results during compression molding process, while such flow in molds is affected by material characteristics. For numerical simulation of SMC molding process, estimation of material property of SMC must be accomplished. In this study, flow resistance of SMC was estimated through a simple compression test using a lubricant with grease oil under the constant strain rate condition at various temperatures and the result was compared with other material data available in the literature. The accuracy of the experimentally determined flow resistance was tested by finite element analyses of compression molding of SMC. Simulation results were compared with experimental results under the plane strain condition.

• Structural Engineering and Mechanics
• /
• v.3 no.6
• /
• pp.611-622
• /
• 1995

This paper is concerned with inelastic load carrying capacity of tapered steel members with or without accumulated plastic strains resulted from previous loading histories. A finite element program is developed using stiffness matrices of tapered members and is applicable for analyses with material and geometric nonlinearity. Results of analyses are compared with other available solutions and with experimental results.

• Steel and Composite Structures
• /
• v.18 no.1
• /
• pp.51-69
• /
• 2015

In recent years, the use of fiber reinforced polymer composites has increased because of their unique features. They have been used widely in the aircraft and space industries, medical and sporting goods and automotive industries. Thanks to their beneficial and various advantages over traditional materials such as high strength, high rigidity, low weight, corrosion resistance, low maintenance cost, aesthetic appearance and easy demountable or moveable construction. In this paper, it is aimed to determine and compare the geometrically nonlinear static and dynamic analysis results of footbridges using steel and glass fiber reinforced polymer composite (GFRP) materials. For this purpose, Halgavor suspension footbridge is selected as numerical examples. The analyses are performed using three identical footbridges, first constructed from steel, second built only with GFRP material and third made of steel- GFRP material, under static and dynamic loadings using finite element method. In the finite element modeling and analyses, SAP2000 program is used. Geometric nonlinearities are taken into consideration in the analysis using P-Delta criterion. The numerical results have indicated that the responses of the three bridges are different and that the response values obtained for the GFRP composite bridge are quite less compared to the steel bridge. It is understood that GFRP material is more useful than the steel for the footbridges.

• Explosives and Blasting
• /
• v.35 no.1
• /
• pp.27-33
• /
• 2017

In this study, two fracture toughness test procedures are modelled for selected metal and rock on LS-DYNA, which is a commercial finite element code. The tests are conducted by using the 3-point bend test procedure for rectangular bar specimen. Because it takes a relatively long time to conduct the test, the implicit solver based on the Newmark method is adopted for the analyses. The values of stress intensity factor obtained from the analyses are 73 and $0.3MPa.m^{0.5}$ for the metal and rock material, respectively. It can be thought that the resulting small value of the fracture toughness of the rock material model well represents the brittleness of rock material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.486-486
• /
• 2009

In this paper, the current-voltage (I-V) curves, such as linear sweep voltammetry (LSV) and cyclic voltammetry (CV), were employed to evaluate the effect of electrolyte concentration on the electrochemical reaction trend. From the I-V curve, the electrochemical states of active, passive, transient and trans-passive could be characterized. And then, we investigated that how this chemical affect the process of voltage-induced material removal in electrochemical mechanical polishing (ECMP) of Copper. The scanning electron microscopy (SEM) and energy dispersive spectroscopy EDS) analyses were used to observe the surface profile. Finally, we monitored the oxidation and reduction process of the Cu surface by the repetition of anodic and cathodic potential from cyclic voltammetry (CV) method in acid- and alkali-based electrolyte. From these analyses, it was important to understand the electrochemical mechanisms of the ECMP technology.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.13 no.1
• /
• pp.61-68
• /
• 2017

Reactor pressure vessel (RPV) under severe accident conditions accompanied by core melting is exposed to direct high-temperature thermal loads. Understanding the creep behavior of the material is one of the most important factors for evaluating the structural integrity at these conditions. While damage evaluation studies have been conducted on critical structures of nuclear power plants through finite element (FE) analyses considering creep behavior, for accurate creep damage evaluation, constitutive equations considered in the FE analyses may have different results depending on the time hardening and strain hardening models as well as the tertiary creep consideration. The purpose of this study is to evaluate the creep damage under severe accident conditions by using FE method for a representative domestic RPV material, SA508 Gr.3. The effect of material hardening models and constitutive equations which are the main variables were also investigated.

• Korean Journal of Metals and Materials
• /
• v.48 no.6
• /
• pp.551-556
• /
• 2010

In this report, we describe mold materials that were used to produce movable metal type by the investment casting method during the Joseon dynasty period in Korea. Samples were obtained from the Wibuinja collection, which is held by the National Museum of Korea. Most of the mold material remnants were found in the depressed areas of the movable type specimens, and we therefore performed non-destructive analyses including XRF, EDS, and XRD. Through these analyses, we were able to identify the mold remnants as hydrocerussite [trilead dihydroxide dicarbonate, $Pb_3(CO_3)_2(OH)_2$] formed in platy hexagonal crystallites. Hydrocerussite was first used to make white pigments and cosmetics in ancient Greece, but this is the first report of hydrocerussite used as mold material applied around a disposable pattern for investment casting. The results of this study will further the understanding of the production process for early movable metal type and ancient casting technologies.

• Journal of Mechanical Science and Technology
• /
• v.15 no.8
• /
• pp.1079-1089
• /
• 2001

This paper proposes J and CTOD estimation schemes applied to fracture toughness testing, covering typical homogeneous and bi-material specimens. Recommendations are based on the plastic limit analysis (either slip line field or finite element limit analyses), assuming the rigid plastic material behavior. The main outcome of the present study is that the J and CTOD estimation schemes (both codified and non-codified), recommended for homogeneous specimens, can be equally used for bi-material specimens with interface cracks. The effect of yield strength mismatch in bi-material specimens on the J-integral CTOD is discussed.

• Coupled systems mechanics
• /
• v.7 no.4
• /
• pp.441-453
• /
• 2018

Longitudinal fracture in a functionally graded beam configuration was studied analytically with taking into account the non-linear behavior of the material. A cantilever beam with two longitudinal cracks located symmetrically with respect to the centroid was analyzed. The material was functionally graded along the beam width as well as along the beam length. The fracture was studied in terms of the strain energy release rate. The influence of material gradient, crack location along the beam width, crack length and material non-linearity on the fracture behavior was investigated. It was shown that the analytical solution derived is very useful for parametric analyses of the non-linear longitudinal fracture behavior. It was found that by using appropriate material gradients in width and length directions of the beam, the strain energy release rate can be reduced significantly. Thus, the results obtained in the present paper may be applied for optimization of functionally graded beam structure with respect to the longitudinal fracture performance.

• Journal of KSNVE
• /
• v.9 no.3
• /
• pp.472-476
• /
• 1999

The effect of static preload on the dynamic properties of rubber materials is rather important, especially when good isolation characteristics are required at high frequencies. However, there are still few papers for dynamic characteristics of compressed rubber components. It was demonstrated in reference (4) that for bonded rubber material of a cylindrical shape, a simplified theory equation between linear dynamic and nonlinear static behavior of rubber material was useful to predict their combined effects. This paper presents the second part of the study. It is confirmed that for the compressed rubber material, the stress can be factored into a function of frequency and a function of strain(stretch). The finite element methodis applied to analyze non-linear large deformation of rubber material and its results are compared with those of a simplified theory equation. The predicted dynamic material properties based on non-linear static finite element analyses have a good agreement of experimental results and those based on simplified theory equation.