• Transactions of Materials Processing
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• v.14 no.4 s.76
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• pp.338-350
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• 2005

Recently, in the field of automobile industry, to solve the problem of reducing the weight of automobile for the improvement of fuel efficiency and the protection of environment, the aluminum alloy parts have been substituted for the steel parts. However, the aluminum alloy does not have as good mechanical property as the steel part. To improve the mechanical property, the semi-solid die casting process is performed to make automobile parts. In the fabrication of semisolid material the control of the liquid segregation is very important to improve the material properties of aluminum alloy. In the present paper we examine the influence of the liquid segregation by the injection conditions in the semi-solid die casting has been investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2034-2043
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• 2002

The process design to produce a near net shape home-appliance compressor component using semi-solid die casting process is performed. In order to obtain a good component without defects such as liquid segregation and porosity, the relationship between pressure and time, and plunger tip displacement and injection velocity are proposed with repeated trial and error. The effect of the velocity variation in the process parameters on liquid segregation and extraction is investigated to produce the aluminum frame part(a kind of compressor part) with good mechanical properties. The mechanical characteristic of semi-solid die casting formed parts for AlSi7Mg0.65r(A357) and AlSi17Cu4Mg(A390) are investigated with a view to minimizing the occurrence of defects. To investigate of application possibility at industry field, A380 aluminum alloy with 8∼9% silicon contents used for the squeeze casting process. The obtained mechanical properties is compared with semi-solid die casting.

• Journal of Korea Foundry Society
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• v.27 no.1
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• pp.31-35
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• 2007

In order to develop the semi-solid forming technology for magnesium alloy the rheological and thixotropic behavior of Mg alloy slurry with varying shear rates and cooling rates was investigated and simulated with considering the viscosity based on microstructures and processing variables. The viscosity of slurry of Mg alloy (AZ91D) in semi-solid region was exponentially increased with a solid fraction, and was decreased with increasing a shear rate. In order to analyze precisely the rheological behavior, the ANYCAST program modified with the Carreau model and the different heat transfer coefficient between the cast and mold was used to simulate the flow behavior of Mg semi-solid slurry during the injection into a casting mold in a high pressure diecasting machine. The simulated rheological behavior of Mg alloy slurry was matched well with the experimental results.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.130-136
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• 2009

Semi-solid casting(SSC) of magnesium alloys is increasingly being used to produce high quality components. This process is similar to the injection molding of plastics and is called thixomolding. Using this process, higher strength, thinner wall sections and tighter tolerances without porosity are obtained. The high strength and low weight characteristics of magnesium alloys render the high-precision fabrication of thin-walled components with large surface areas. They are widely used for the IT, auto and consumer electronics industries. However, warpage of the thin-walled sections degrade quality of the parts produced in the SCC process. To produce thin-walled magnesium alloy parts, the geometry of gating system on the quality of the finished products should be clearly studied. In this paper, to minimize warpage of the thin-walled sections, Taguchi method is applied to the optimal design of the gate geometry in the thixomolding process. Width, height, length and angle of the gating system are selected for the robust design parameters. Effectiveness of the robust design is verified through the CAE software.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.61-64
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• 2003

In the field of automobile industry, suspension parts have been fabricated by the light metal part to substitute the steel part. For application light metal of suspension parts, mechanical property of high strength was performed. For anting semi-solid die casting of suspension part, die filling and solidification simulation have been carried out with Ostwald-de Waele rheological model. We designed the optimal die and secured injection condition as possible as laminar flow based on the result of computer simulation. Mechanical properties of knuckle part and heat treatment condition were investigated.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.7-21
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• 2000

This paper describes an overview of the thixoforming and thixomolding processes. Semi-solid metalworking (SSM), which is called the thixoforming process of aluminium materials, incorporates the elements of both casting and for the manufacture of near net shape parts. The SSM has some advantages such as net shape or near net shape manufacturing, the ability to form thin walls, excellent surface finish, tight tolerance, and excellent dimensional precision. The thixomolding process of Mg alloy (AZ9l) is a combination of two technologies both conventional die casting and plastic injection molding. The feed material used is a machined chip with a geometry of approximately 1 mm square and a length of 2~3 mm. The semi-solid forming (SSF) of high quality aluminium and magnesium parts will be established in the automotive and electronic industry, in the future. The hybrid method of casting/forging has been caused attention. This process uses a preformed material made by casting instead of the wrought material and finishes it by a single forging process. This process is expected to lower costs without sacrificing the mechanical and finishes it by a single forging process. The process is expected to lower costs without sacrificing the mechanical properties. The authors, intending that the casting/forging process contributes to a reduction in production cost of aluminum automotive parts in Korea, describes the feature of the casting/forging process, aluminum alloys suitable for the cast preform, microstructure and mechanical properties of the cast preform, application examples of cast/forging, and further study.

• Earthquakes and Structures
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• v.13 no.1
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• pp.1-8
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• 2017

This article is all about using the MR damper with an external lever system for mitigation torsional and transitional lateral displacements by using of PID control algorithm. The torsional modes are so destructive and can be varied during an earthquake therefore, using a semi-active control system mostly recommended for them. In this paper the corner lateral displacement of each floor obtains and then it equivalents in a solid member and it connects to an MR damper, which relies to a rigid structure to reduce the response. An MR damper is a semi-active control system, which can absorb a lot of energy by injecting current to it. This amount of current is very low and needs low power supply, but it increases the amount of damper force, rather than inactive systems like viscous dampers. This paper will show the appropriate algorithm for current injection into MR damper when the eccentricity of the load is changed by using of Bouc-Wen and Bingham's methods and illustrates the coincidence of them.

• BMB Reports
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• v.55 no.12
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• pp.615-620
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• 2022

The murine leukemia virus-based semi-retroviral replicating vectors (MuLV-based sRRV) had been developed to improve safety and transgene capacity for cancer gene therapy. However, despite the apparent advantages of the sRRV, improvements in the in vivo transduction efficiency are still required to deliver therapeutic genes efficiently for clinical use. In this study, we established a gibbon ape leukemia virus (GaLV) envelope-pseudotyped semi-replication-competent retrovirus vector system (spRRV) which is composed of two transcomplementing replication-defective retroviral vectors termed MuLV-Gag-Pol and GaLV-Env. We found that the spRRV shows considerable improvement in efficiencies of gene transfer and spreading in both human glioblastoma cells and pre-established human glioblastoma mouse model compared with an sRRV system. When treated with ganciclovir after intratumoral injection of each vector system into pre-established U-87 MG glioblastomas, the group of mice injected with spRRV expressing the herpes simplex virus type 1-thymidine kinase (HSV1-tk) gene showed a survival rate of 100% for more than 150 days, but all control groups of mice (HSV1-tk/PBS-treated and GFP/GCV-treated groups) died within 45 days after tumor injection. In conclusion, these findings sug-gest that intratumoral delivery of the HSV1-tk gene by the spRRV system is worthy of development in clinical trials for the treatment of malignant solid tumors.

• Transactions of Materials Processing
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• v.23 no.4
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• pp.244-249
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• 2014

The thixoforming process has been applied to forming of a joint node for the aluminum frame of a low speed electric vehicle. A joint node should connect three aluminum extruded chassis showing different profiles. The MHS(magnetohydrodynamic stirring) A357 billet was selected because homogeneous globular grains are necessary as the billet materials for thixoforming. A careful design of joint node has been performed by the considerations of structural demands and the simulation results for the thixoforming process using the MAGMAsoft. Optimum heating temperature for the A357 billet was between 580 and $585^{\circ}C$ corresponding to the semi-solid temperatures showing 20-30% of liquid fraction. An injection speed of around 100mm/s and preheating of die at temperatures of $200^{\circ}C$ were also necessary conditions to obtain reasonable thixoformed parts.

• Journal of Korea Foundry Society
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• v.27 no.4
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• pp.173-178
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• 2007

The bearing bracket, which has produced by the squeeze casting for the high strength in lightweight part of automobile, was developed by the rheocasting process using the H-NCM slurry. Compared with the squeeze casting, the rheocasting process has some merits such as shortening cycle-time, reducing total weight, and increasing productivity. In this study, partial feeding test was carried out by controlling plunger stroke length and compared with semisolid simulation. Optimal casting parameters such as injection speed and stroke variations were established. Sound products with integral microstructure were obtained by the H-NCM slurry and X-ray analysis also showed the integral condition throughout the entire parts.