• Textile Coloration and Finishing
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• v.34 no.1
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• pp.46-57
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• 2022

In this study, the relationship between fiber orientation and mechanical properties with the injection pressure of polyamide-6/glass fiber composite materials manufactured by the injection molding process was investigated. Also, an actual experimental data and finite element model-based simulation data were analyzed. Specimens were manufactured through the injection molding process setting the injection pressure differently to 700, 800, 900, and 1000 bar, respectively. A morphological analysis and orientation of the PA6/GF composite material were observed using Optical microscope. Through tensile and flexural strength tests, the mechanical properties of the PA6/GF composite materials with the injection pressure were studied. As a result, it was confirmed that the mechanical properties were the superior under the injection pressure of 900 bar molding conditions. In addition, the mechanical properties of the actually manufactured specimen (PA6/GF) and virtual engineering S/W((Digimat, Abaqus) were used to compare and analyze the analysis results for the mechanical properties, and based on the reliable DB, the physical properties of the PA6/GF composite characteristics were studied.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.313-318
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• 2001

A haptic hand controller operated by the user's hand can receive information on position and orientation of the hand and display force and moment generated in the virtual environment to the hand. This paper presents a design method for KU-HHC, 6 DOF Korea University-haptic hand controller, which allows separation of workspace from linkage mechanism in consideration of the efficient user operation. First, the 3 DOF mechanism in which all the actuators are mounted on the fixed base is developed by combining a 5-bar linkage and gimbal mechanism. Then, the 6 DOF HHC is designed by connecting the two 3 DOF devices through a handle. This paper presents the forward and inverse kinematics for this device and Jacobian analysis. Improvement of the kinematic characteristics using performance index is also discussed. The hand controller KU-HHC based on this design concept and kinematic analysis was manufactured and shows excellent performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.18-25
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• 2003

A haptic hand controller (HHC) operated by the user’s hand can receive information on position and orientation of the hand and display force and moment generated in the virtual environment to the hand. In this paper, a 3-DOF hand controller is first presented, in which all the actuators are mounted on the fixed base by combining a 5-bar linkage and a gimbal mechanism. The 6-DOF HHC is then designed by connecting these two 3-DOF devices through a handle which consists of a screw and nut. Analysis using performance index is carried out to determine the dimensions of the device. The HHC control system consists of the high-level controller for kinematic and static analysis and the low-level controller for position sensing and motor control. The HHC used as a user interface to control the mobile robot in the virtual environment is given as a simple application.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.2
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• pp.79-90
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• 1996

Transmission electron microscopy(TEM) investigation on the phase decomposition of B2-ordered (Ni,Co)Al supersaturated with Ni and Co has revealed the precipitation of $(Ni,Co)_2Al$ which has not been expected from the reported equilibrium phase diagram. The $(Ni,Co)_2Al$ phase has a hexagonal struture and takes a rod-like shape with the long axis of the rod parallel to the <111> directions of the B2 matrix. By aging at temperatures below 873 K, a long period Superlattice Structure appears in the hexagonal $(Ni,Co)_2Al$ Phase. The orientation relationship between the $(Ni,Co)_2Al$ Precipitates and the B2-(Ni,Co)Al matrix is found to be$(0001)_p$ // $(111)_{B2}$ and $[\bar{1}2\bar{1}0]_P$ // $[\bar{1}10]_{B2}$, Where the suffix p and B2 denote the $(Ni,Co)_2Al$ precipitate and the B2-(Ni,Co)Al matrix, respectively. (Ni,Co)Al hardens appreciably by the fine precipitation of the $(Ni,Co)_2Al$ phase. Energy dispersive spectroscopy was used to analyze the compositions of each phase formed in B2-(Ni,Co)Al.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.3
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• pp.84-92
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• 2014

In this paper, a novel 5-axis hybrid-kinematic machine tool is introduced and the research results on accuracy improvement of the prototype machine tool are presented. The 5-axis hybrid machine tool is made up of a 3-DOF parallel manipulator and a 2-DOF serial one connected in series. The machine tool maintains high ratio of stiffness to mass due to the parallel structure and high orientation capability due to the serial-type wrist. In order to acquire high accuracy, the methodology of measuring the output shafts by additional sensors instead of using encoder outputs at the motor shafts is proposed. In the kinematic view point, the hybrid manipulator reduces to a serial one, if the passive joints in the U-P serial chain at the center of the parallel manipulator are directly measured by additional sensors. Using the method of successive screw displacements, the kinematic error model is derived. Since a ball-bar is less expensive than a full position measurement device and sufficiently accurate for calibration, the kinematic calibration method of using a ball-bar is presented. The effectiveness of the calibration method has been verified through the simulations. Finally, the calibration experiment shows that the position accuracy of the prototype machine tool has been improved from 153 to $86{\mu}m$.

• Korean Journal of Cognitive Science
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• v.27 no.3
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• pp.355-376
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• 2016

We used holes defined by color similarity (Experiment 1) and binocular disparity (Experiment 2) to study how the inner contour of an object (i.e., boundary of a hole in it) is encoded in visual working memory. Many studies in VWM have shown that an object's boundary properties can be integrated with its surface properties via their shared spatial location, yielding an object-based encoding benefit. However, encoding of the hole contours has rarely been tested. We presented objects (squares or circles) containing a bar under a change detection paradigm, and relevant features to be remembered were the color of objects and the orientation of bars (or holes). If the contour of a hole belongs to the surrounding object rather than to the hole itself, the object-based feature binding hypothesis predicts that the shape of it can be integrated with color of an outer object, via their shared spatial location. Thus, in the hole display, change detection performance was expected to better than in the conjunction display where orientation and color features to be remembered were assigned to different parts of a conjunction object, and comparable to that in a single bar display where both orientation and color were assigned into a single bar. However, the results revealed that performance in the hole display did not differ from that in the conjunction display. This suggests that the shape of holes is not automatically encoded together with the surface properties of the outer object via object-based feature binding, but encoded independently from the surrounding object.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2283-2288
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• 2009

There are a lot of characteristics in Human visual information processing when image information is transmitted from retina to visual cortex. Among them, we analyze the sensibility of the orientation and cortical magnification on an image. The fact that the small fovea is allotted a large area on the cortex is called the cortical magnification factor. We compare recognition rates by weight of vertical, horizontal and diagonal response. In statistics analysis, we show that a particular simple cell responds best to a bar with a vertical orientation. After then, we will apply the characteristics to Human visual system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1518-1525
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• 2006

Finite element analyses of structures made of the fiber reinforced composites require an adequate method to characterize the high anisotropic behavior induced by one or several layers of fiber cords with different spatial orientation embedded in a rubber matrix. This paper newly proposes a continuum based rebar element considering change of the orientation of the fiber during deformation of the composite. The mechanical behavior of the embedded fiber is modeled using two-node bar elements in order to consider the relative deformation and spatial orientation of the embedded fiber. For improvement of the analysis accuracy, the load-displacement curve of fiber is applied to the stiffness matrix of fiber. A finite element program is constructed based on the total Lagrangian formulation considering both geometric and material nonlinearity. Finite element analyses of the tensile test are carried out in order to evaluate the validity of the proposed method. Analysis results obtained with the proposed method provides realistic representation of the fiber reinforced rubber composite compared to results of other two models by the Halpin-Tsai equation and a rebar element in ABAQUS/Standard.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.4
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• pp.270-277
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• 1997

Plastic anisotropy is one of important factors which determine the drawability of a steel sheet. It has been mainly measured by mechanical tensile test. From the ultrasonic velocities propagating along the relative directions to the rolling direction, CODF(crystallite orientation distribution function) can be measured and ODC's(orientation distribution coefficients) has some correlations with the plastic anisotropy. In this study the correlations between the plastic anisotropy and ODC's of the cold rolled steel sheet were measured. From the results of ultrasonic velocity measurements the average normal anisotropy, $\bar{\gamma}$ and the average planar anisotropy, ${\Delta}r$ could be predicted within the accuracy of ${\pm}0.082$ and ${\pm}0.096$, respectively. Acoustic resonance method was applied to measure the ultrasonic velocities and EMAT's were used for generating and detecting the ultrasonic waves.

• Korean Journal of Crystallography
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• v.5 no.1
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• pp.24-32
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• 1994

The study of (0001), (1120) and (1011) GAN epitaxy films grown on the (0001),(1012) and (1120) α-Al2O3 substrates have been investigated using the haliar vapor phaes epitaxy(HVPE) method in Ga/HCI/NH3/He system. XRD, RHEED and SEM are used for the study of the films struction and surface morphology. Chemical composition of the film surface is estimsted by XPS. The following orientation relationships are observed; (0001) GaN /(0001) Al2O3 (1120) GaN/ (1012) Al2O3 and (0001) and (1011) GaN/ (1120) Al2O3 in accordance with growth conditions. The (0001) GaN films grown on(0001) and (1120) a-Al2O3 substrates at higer temperature(1050℃) have shown two dimensional grownth mechanism. Form SEM and RHEED, the smoother surface morphology and better structure are observed for the (1011) GaN films grown on (1120) sapphire at higer temperature.