The Mechanical Behavior of Materials X

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Authors: Chang Yong Kang, Don Wook Son, Jang Hyun Sung, Ki Woo Nam
Abstract: The damping capacity and strength of Fe-6Al-25/34Mn alloys have been studied for the development of new materials with high strength and damping capacity. Particularly, the effect of α’(including α) and ε martensite phases, which constitute the microstructure of cold rolled Fe-Al-Mn alloys, has been investigated in terms of the strength and damping capacity of the alloys. The damping capacity rises with increasing the degree of cold rolling and reveals the maximum value at 32% reduction. The damping capacity is strongly affected by the volume fraction of ε martensite. The phases such as α’ and austenite(γ)   on damping capacity. Considering that tensile strength increases and elongation decreases with increasing the volume fraction of α’-martensite, it is proved that tensile strength is mainly affected by the amount of α’martensite.
Authors: Ki Hyun Kim, Dae Gab Gweon, Hyun Soo Jung, Soo Hun Lee, Min Sung Hong, Moon G. Lee
Abstract: Design of design of X-Y-Theta fine stage using VCM (voice coil motor) is presented in this paper. This fine stage is combined with linear DC motor. Long range, high speed and high precision of the stage is obtained by using dual servo control for laser micro/nano machining. A novel structure of VCM for the fine stage is proposed. The fine stage can have 3 DOF(X-Y-Theta) motion by four VCM actuators which are located on the same plane. The X-Y-Theta fine stage is designed to have high acceleration for high throughput. Based on the design, the stage is fabricated. The designed stage has the acceleration of 5m/s2 with 45kg total mass. In addition, this actuator is feedback controlled using HP laser interferometer. The reaction force between the coarse and fine stage of the dual servo is compensated by force compensator.
Authors: Young Hun Chae
Abstract: The current study investigated the effect of micro-dimple size on reduction friction to understand the potential of friction reduction through micro-scale dimple to fabricate by photolithography on pin-on-disk test using flat-on-flat contact geometry. It was verified that the friction property with respect to the same pitch influences the size of dimple under lubricated sliding contact. Additionally, it was recognized from Stribeck curve that the friction property has a connection with the size of dimple. This can explain the relationship between the friction coefficient and a dimensionless parameter for lubrication condition. The friction property has an effect on the size of surface texture on reduction friction, not only because of the density of dimple, but also because of the ratio of diameter/pitch. A ratio of approximately 0.5 is recommended under the tested friction condition. It is suggested that the ratio of d/p is an important parameter for surface texture design.
Authors: Young Hun Chae
Abstract: Some surface patterns of tribological application are an attractive technology of engineered surface. Because of the friction reduction is considered to be necessary for improved efficiency of machine. This study was investigated for the effect of friction property for angles of micro-crosshatch groove surface pattern on bearing steel used pin-on-disk test. We obtain sample which can be fabricated by photolithography process. We discuss the friction property depended on an angle of crosshatch groove surface pattern. We can verify the lubrication mechanism as Stribeck curve which has a relationship between the friction coefficient and a dimensionless parameter under the lubrication condition. It was found that the friction coefficient was related to angle of crosshatch groove pattern on contact surface.
Authors: S.O. Jang, S.Y. Lee, K.N. Kim, K.M. Kim, B.I. Kim
Abstract: Carbonate apatite has a similar structure to the inorganic component of teeth and bone. Although carbonate apatite is widely used as a bone substitute, there are no reports on its use as a desensitizing dentifrice. This in vitro study evaluated the relative abrasivity of the dentifrice containing nano-sized carbonated apatite (n-CAPs) using a Surface Profile Method (SPM). The dentin specimens were made from the root of extracted human molars. The cervical part of the teeth was sectioned with a diamond wheel disk. The teeth were embedded into an epoxy resin mold and the surface was gradually polished using silicone carbide paper. After grinding, the degree of surface roughness was examined within the range of 2 mm with tapping. The British Standard Institution reference dentifrice (BSI: CaCO3 40%) and the experimental dentifrices (group 1: n-CAPs 30%, group 2: n-CAPs 15% and silica 15%, group 3: n-CAPs 5% and silica 25%, group 4: silica 30%, group 5: CaCO3 10% and SrCl2 10%) were compared. The dentifrice slurries were prepared by mixing 24 grams of the dentifrice in 12 ml distilled water. Each tooth specimen was brushed 1,000 times with the dentifrice slurries using a back-and-forth stroke. The relative abrasivity of each dentifrice was evaluated by determining the ratio of the BSI standard dentifrice to each experiment. The results were analyzed using one-way ANOVA and Tukey’s multiple comparisons using Window SPSS (Statistical analysis system) 12.0. According to the results, Group 1 (3.2), which contained only n-CAPs appeared to have the lowest abrasivity than the BSI dentifrice (100). However, Groups 2 (124.2), 3 (137.9) and 4 (178.1), which contained n-CAPs and silica, appeared to have a higher abrasivity than the BSI dentifrice (p>0.05). The relative abrasivity of group 5 (38), which was a commercial desensitizing dentifrice, was relatively lower. It appears that the higher abrasivity of the experimental is due to the shape and size of the silica component. Therefore, n-CAPs itself has no influence on the abrasivity of the dentifrice. The main reason for the low abrasivity of n-CAPs is believed to be its small particle size (range 50-90nm).
Authors: Shigeru Hamada, Kenji Hashizume
Abstract: In order to evaluate strength reliability of micron size polycrystalline silicon (poly-Si) structure, bending tests of cantilever beam and Weibull analysis are performed. Recently, the importance of microelectromechanical systems (MEMS) in society is increasing, and the number of production is also increasing. The MEMS devices, which contain mechanical movement, have to maintain their reliability in face of external shock, thermal stress and residual stress from manufacturing processes. In greeting the mass production era of the MEMS, in case the material strength design of MEMS is performed, required strength data is not average value but the variation, especially minimum value of the material. Micron size poly-Si structure is widely employed in the MEMS such as microsensor, switching device and so on. Then, in order to evaluate strength reliability of micron size poly-Si structure, tests and analysis are performed. The specimen is made by chemical vapor deposition (CVD) process and thickness is 3.5, 6.4 and 8.3 micrometer and the specimen has notch. The test specimen used for the test changed characteristics of (1) film thickness (2) stress concentration, and investigation about the influence each effects of the variation in a bending strength are discussed.
Authors: Jong Kweon Kim, Shi Hoon Choi, Yong Bum Park
Abstract: The crystallographic texture and mechanical properties were investigated in a nanocrystalline Fe-50%Ni alloy fabricated by using an electrodeposition method. The as-deposited texture was characterized by strong <100>//ND and weak <111>//ND fibre components, and the occurrence of grain growth resulted in the strong development of the <111>//ND fibre components with the minor <100>//ND fibre components. The elastic modulus and hardness were measured by means of a nanoindentation test. The annealing led the specimen to an increase in the elastic modulus and a strong decrease in the hardness. The elastic modului measured were compared with the theoretic predictions based on an elastic self-consistent (ESC) polycrystal model. The theoretical values of the elastic moduli through the thickness direction in the sample were in a good agreement with the experimental results.
Authors: Hyun Su Kim, Young Chul Park, Seung Hwan Oh, Se Hun Kim, Young Jik Jo, Jung Ho Kang
Abstract: This is a widespread requirement for low cost lightweight thermal imaging sensors for both military and civilian applications. The feasibility of micromechanical optical and infrared (IR) detection using microcantilevers is demonstrated. Microcantilevers provide a simple Structurefor developing single- and multi-element sensors for visible and infrared radiation that are smaller, more sensitive and lower in cost than quantum or thermal detectors. Microcantilevers coated with a heat absorbing layer undergo bending due to the differential stress originating from the bimetallic effect. This paper reports a micromachined silicon uncooled thermal imager intended for applications in automated process control.
Authors: Jung Yup Kim, Hyun Ju Choi, Sang Joo Lee, Hak Joo Lee
Abstract: In the semiconductor inspection, number of pads at unit area is increasing and pad array have become irregular 2-dimensional. So we develop a bellows type micro contact probe. Our micro contact probe is a vertical-type micro contact probe for area arrays and narrow pitch electrode pads. We choose bellows type micro contact probe to prevent stress concentration. Our design targets are 120 um pad pitch, 20-50 um OD(over drive) and over 5 mN reaction force. In this research, micro contact probe is made by electroplating(Ni-Co). structural analysis is accomplished by FEM. And characterization of micro contact probe is done by our own mechanical tester. So material property is measured for structural analysis and structural analysis result will be compared with experimental result.

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