• 한국주조공학회지
• /
• 제26권1호
• /
• pp.3-7
• /
• 2006

• 한국주조공학회지
• /
• 제30권2호
• /
• pp.66-75
• /
• 2010

The effects of alloying elements on the mechanical properties of normalized and quenched 3.60wt%C-2.60wt%C ductile cast iron poured into shell stack mold were investigated. The strength and hardness of as-cast specimen were increased and the elongation of it was decreased with the additions of Mn, Cu and Sn. The strength and hardness were increased with the addition of 0.40wt%Mo and then rather decreased with the increased addition of 0.80wt%. The strength and hardness were increased with normalizing treatment and the strengths of normalized specimens were increased slightly with the addition of alloying elements except Mo. Meanwhile the yield strength of the normalized specimen was increased slightly with the addition of Mo, the tensile strength was not changed much. Meanwhile the hardness and strength of the quenched specimen were slightly increased with the addition of Mn, those were almost not changed with the amount added. The tensile strength of the quenched specimen with larger diameter, when the Cu had been added, and the tensile and yield strengths of them, when Mo had been added, were increased with the addition of alloying element. On the other hand, those were not changed with the amount added. For the case of specimen with smaller diameter, there were no effects of these two elements. When Sn had been added, the strength of hardened specimen with larger diameter was slightly increased with the amount added. However, that with smaller diameter was rather decreased with it. The effect of specimen diameter on the strength of quenched specimen with the addition of Cu, Mo and Sn was reduced.

• 한국정밀공학회지
• /
• 제19권1호
• /
• pp.180-185
• /
• 2002

Aluminum casting/forging process is used to produce an aluminum tie-rod end for the steering system of automobiles. Firstly, casting experiments were carried out to get a good preform for forging the tie-rod end. In the casting experiment, the effects of additives, Ti+B, Zr, Sr, and Mg, on the mechanical properties and the microstructure of a cast preform were investigated. And a finite element analysis was performed to determine an optimal configuration of the cast preform. Lastly, a forging experiment was carried out to make the final product of aluminum tie-rod end by using the above cast preform. In the casting experiments, when 0.2% Ti+B and 0.25% Zr were simultaneously added into molten Al-Si alloy, the highest values of tensile strength and elongation of the cast preform were obtained. When 0.04% Sr were added into the molten aluminum alloy, the finest silicon-structure was observed in the cast preform. The highest hardness was obtained when 0.2% Mg was added. In the forging experiment, It was confirmed that the optimal configuration of a cast preform predicted by FE analysis was very useful. The hardness of a cast/forged product using designed preform was superior to that of required specification.

• 한국주조공학회지
• /
• 제25권2호
• /
• pp.102-108
• /
• 2005

The ability and fading behavior of inoculant in ductile cast iron melt and the effect of minor element on them were investigated. The result obtanied on nodularization and the performance of inoculant were more distinct when the melt was treated and held at the high temperature range of $1450{\sim}1500^{\circ}C$ than at the lower one of $1350{\sim}1400^{\circ}C$. The performance of 5.2%Mg-Fe-Si alloy was the best of 4 nodularizers. That of Fe-75%Si(I) alloy was better than other 4 inoculants. The performance of the Fe-75%Si(I) inoculant was deteoriated by the addition of sulfur or bismuth. On the other hand, that was improved by the addition of cerium, even though its extent was not big.

• Structural Engineering and Mechanics
• /
• 제42권1호
• /
• pp.55-72
• /
• 2012

Precast-cast insitu concrete bridge construction is widely practiced for small to medium span structures. These bridges consist of precast pre-stressed concrete beams of various cross-sections with a cast in-situ reinforced concrete slab. The connection between the beams and the slab is via shear links often included during the manufacturing process of the beams. This form of construction is attractive as it provides for standardisation, reduced formwork and construction time. The assessment of the integrity of shear connectors in existing bridges is a major challenge. A procedure for assessment of shear connectors based on vibration testing and finite element model updating is proposed. The technique is applied successfully to a scaled model bridge model and an existing bridge structure.

• Structural Engineering and Mechanics
• /
• 제57권5호
• /
• pp.937-949
• /
• 2016

Fiber reinforced polymer (FRP) applications in the structural engineering field include concrete-FRP composite systems, where FRP components are either attached to or embedded into concrete structures to improve their structural performance. This paper presents the results of an analytical study conducted using finite element model (FEM) to simulate the behavior of three-points load beam reinforced with GFRP and/or steel bars. To calibrate the FEM, a small-scale experimental program was carried out using six reinforced concrete beams with $200{\times}200mm$ cross section and 1000 mm length cast and tested under three point bending load. The six beams were divided into three groups, each group contained two beams. The first group was a reference beams which was cast without any reinforcement, the second group concrete beams was reinforced using GFRP, and the third group concrete beams was reinforced with steel bars. Nonlinear finite element simulations were executed using ANSYS software package. The difference between the theoretical and experimental results of beams vertical deflection and beams crack shapes were within acceptable degree of accuracy. Parametric study using the calibrated model was carried out to evaluate two parameters (1) effect of number and position of longitudinal main bars on beam behavior; (2) performance of concrete beam with composite longitudinal reinforcement steel and GFRP bars.

• 대한화학회지
• /
• 제7권1호
• /
• pp.51-57
• /
• 1963

It is well known that the graphite flakes become spherulite, when a suitable amount of nodulizing element, such as cerium or magnesium, is added to the cast iron. The change of graphite from flake to nodular shape improves not only the tensile strength but the ductility as well. However, the mechanism of spheroidization of graphite in cast iron has not yet been clearly understood, and various theories proposed by a number of investigators were such that it may be due to the special nucleation effect, prevention of flake formation by the adsorption of magnesium vapour on the graphite surface or file surface free energy difference between plain graphite and magnesium-adsorbed graphite. Regardless of the speculations of spheroidizing mechanism of the graphite in the cast iron, the final phenomenon comes to the conclusion that it may be due to the lack of wettability between graphite and iron matrix. In order to collaborate this fact through an experimental method, the authors have constructed a vacuum arc furnace for the wettability measurement as its first step. Our study and experiments were then directed to the comparison of the wettability between iron and graphite on the two cases (namely, the one where magnesium was preliminarily coated on the graphite surface and the other not coated), by means of contact angle measurements. The result was such that a significant difference of the contact angles has been shown between the above two cases. indicating the spheroidization of graphite which might have resulted from the lack of wettability between magnesium-adsorbed graphite and iron matrix.

• Journal of Welding and Joining
• /
• 제32권2호
• /
• pp.54-62
• /
• 2014

Manhole cover, which is usually made of grey cast iron and consists of frame and cover, should have enough strength to support the heavy traffic load. The manhole cover made of cast iron has heavy weight to handle manually and is vulnerable to impact force with its brittle characteristics. Moreover, its production process of casting has been regulated in terms of environmental pollution. In this study, steel manhole cover is proposed to substitute the cast cover with a series of structural analyses to confirm its strength to support the test load for manhole cover. The cover of the proposed steel manhole cover is made of thin circular pate and stiffeners below the plate. Rectangular columns and hollow circular plate were selected for the shape of the stiffener. In order to give enough strength for the cover to behave within elastic range in the loading, strengthening structures of the cover were varied with increasing the number and the size of the stiffeners. The results of the analyses revealed that when both the hollow circular stiffener and cross stiffeners were additionally applied at the same time to the steel cover with longitudinal stiffeners, the maximum stress level in the cover could be reduced to that level presented in the cast cover.

• Steel and Composite Structures
• /
• 제38권4호
• /
• pp.365-380
• /
• 2021

Although traditional steel-concrete composite beams have excellent structural characteristics, it cannot meet the requirement of quick assembly and repair in the engineering. This paper presents a study on static behavior of bolt connected steel-concrete composite beam without post-cast zone. A three-dimensional finite element model was developed with its accuracy and reliability validated by available experimental results. The analysis results show that in the normal service stage, the bolt is basically in the state of unidirectional stress with the loss of pretightening can be ignored. Parametric studies are presented to quantify the effects of the post-cast zone, size and position of splicing gap on the behavior of the beam. Based on the studies, suggested size of gap and installation order were proposed. It is also confirmed that optimized concrete slab in mid-span can reduce the requirement of construction accuracy.

• 한국주조공학회지
• /
• 제4권4호
• /
• pp.20-29
• /
• 1984

It is very important to obtain gray and ductile cast irons with completely pearlitic structure by addition more economical alloying elements. In this study, 9 melts of gray iron and 5 melts of Mg-treated ductile cast iron were made according to Sb content (0-0.08% Sb). Each melt were casted to ${\phi}20mm$ test bars in sand mold under the same condition and inspected microstructure, mechanical and thermal properties. The results obtained from this study are as follows: 1. It is confirmed that Sb should be an economical, simple and useful additive for avoiding ferrite in gray and even in ductile cast irons. 2. For gray cast iron, the recommended ladle addition of metallic Sb amounts to 0.05%. At these levels, Sb has no detrimental influence on the mechanical properties of gray cast irons, which are normally modified according to their pearlite content without increasing the chilling tendency. 3. Despite its adverse influence on graphite shape in ductile iron, Sb can be used as a pearlite stabilizing alloying element even in the case of Mg - treated iron. The quantity to be added does not exceed 0.04% in the case of thinwalled castings. 4. The nodule count is increased very much and the shape of graphite particles become remarkably spheroidal. The matrix may be fully pearlitized, except for thin - walled castings, because the high nodule count results inevitably in some ferrite. 5. The $Ac_1$ and pearlite decomposition temperature are rised in accordance with increasing of additive Sb amount.