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Chun D.H.,Yeungnam University | Na H.J.,Korea Textile Machinery Research Institute
19th International Congress on Sound and Vibration 2012, ICSV 2012 | Year: 2012

Since the earliest discoveries of Sabine, the reverberation time is considered to be one of the most important factors in determining the sound quality of a room. The assumptions of homogeneous energy (completely diffuse sound in the room), and continuous, uniform absorption of energy by the boundary surfaces of the room are intrinsic to the theory. For very non-uniformly placed absorbents with same room absorption, as when just one wall is highly absorptive and the rest are reflective, the reverberation time is different. In this paper, the reverberation time by placement of absorbing materials are examined both numerically and experimentally.

Cho K.-S.,Dongyang University | Lee K.-A.,Andong National University | Kim M.-J.,Andong National University | Jeong J.-O.,PIM KOREA Co. | Park S.-W.,Korea Textile Machinery Research Institute
International Powder Metallurgy Congress and Exhibition, Euro PM 2013 | Year: 2013

In this research, we performed tensile tests, microstructure analysis, and high-cycle fatigue tests of Fe-2%Ni alloy specimen produced by using the metal injection molding (MIM) process. In the microstructure observation results, inhomogeneous ferrite and pearlite were appeared. As a result of tensile tests, the tensile strength and strain rate of the specimen was 605 MPa and approximately 6.0%, respectively, and the hardness of the specimen was approximately 220 Hv. The high-cycle fatigue tests revealed the fatigue limit of the Fe-2%Ni alloy specimen to be 410 MPa. Further, by analyzing the fracture surface, we appraised the tensile and fatigue failure behavior of Fe-2%Ni alloys produced by the metal injection molding.

Chun D.H.,Korea Textile Machinery Research Institute | You B.H.,Yeungnam University | You B.H.,Texas State University | Lee H.J.,Texas State University
Fibers and Polymers | Year: 2014

Injection molding has been widely used in the manufacturing of various polymer products, including housewares, home appliances, and automotive parts. A disposable medical device based on polymeric material at a low cost is another important area for injection molding. The numerical analysis was performed to predict the potential problem, often occurring during the manufacturing process of the medical device. Computer-aided engineering model was developed using industry-standard molding software, MOLDFLOW®. The flow pattern of the molten polymer was investigated in the replication of butterfly shaped Catheter Support for various catheterization. The flow pattern and temperature distribution of the molded part were investigated through a series of analysis. The results of analysis with original design predicted non-uniform polymer flow with a poor weld line, unbalanced cavity filling, and uneven temperature distribution of the part. An appropriate gate location to achieve uniform flow pattern for mold filling was determined on the base of the predicted results and experience, considering the performance of the product and limitation of the production. © 2014 The Korean Fiber Society and Springer Science+Business Media Dordrecht.

Kim K.-S.,Andong National University | Lee K.-A.,Andong National University | Kim J.-H.,PIM KOREA Co. | Park S.-W.,Korea Textile Machinery Research Institute | Cho K.-S.,Dongyang University
Advanced Materials Research | Year: 2013

Inconel 713C alloy was tried to manufacture by using MIM(Metal Injection Molding) process. The high-temperature mechanical properties of MIMed Inconel 713C were also investigated. Processing defects such as pores and binders could be observed near the surface. Tensile tests were conducted from room temperature to 900°C. The result of tensile tests showed that this alloy had similar or somewhat higher strengths (YS: 734 MPa, UTS: 968 MPa, elongation: 7.16% at room temperature) from RT to 700°C than those of conventional Inconel 713C alloys. Above 800°C, however, ultimate tensile strength decreased rapidly with increasing temperature (lower than casted Inconel 713C). Based on the observation of fractography, initial crack was found to have started near the surface defects and propagated rapidly. The superior mechanical properties of MIMed Inconel 713C could be obtained by optimizing the MIM process parameters.© (2013) Trans Tech Publications, Switzerland.

Kim M.,Yeungnam University | Han M.S.,Korea Textile Machinery Research Institute | Seo T.,Yeungnam University | Lee J.,Yeungnam University
International Journal of Control, Automation and Systems | Year: 2016

Instantaneous center (IC) analysis of a mechanism is very important in mechanism analysis, since the analysis gives intuition about the global movement of the mechanism, and the analysis also makes the numerical analysis of velocities faster. Previous IC analysis methods have used geometrical information from the mechanism configuration. Such methods have disadvantages of complexity in calculation and difficulty determining the direction of linkage movement due to geometric complexity. This research suggests a new IC analysis method for planar closed chains. The proposed method determines the IC simply from the relation between joint velocities based on graphical representation. Twists in screw theory are used to define the joint velocities in a closed chain and also to calculate the IC. Three different kinds of mechanisms are analyzed by the method: a four-bar mechanism, slidercrank mechanism, and a multiple closed-chain mechanism composed of four-bar and slider-crank mechanisms. The analysis methodology can be applied to calculate the ICs of various planar closed chains. © 2016 Institute of Control, Robotics and Systems and The Korean Institute of Electrical Engineers and Springer-Verlag Berlin Heidelberg

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