• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.87-94
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• 2023

This paper addresses the installation and modification design of airframe structures for new and modified equipment installations that are essential for aircraft performance improvement. Typical performance improvement equipment mounted on the exterior of the aircraft include antenna, radar, electro-optical/infrared (EO/IR), and self-protection system equipment, which require structural reinforcement, modification, and mounting design of the green aircraft for operation. In the interior of the aircraft, console and rack structures are modified or added according to user operation requirements. In addition, this is accompanied by the installation design of equipment to be replaced and added for performance improvement, and the according modification of environmental control system components for internal cooling. The engineering process and cases in which airworthiness was verified through the detailed design of airframe structures with structural integrity, operability, and maintainability of performance-improved aircraft are presented.

• Design & Manufacturing
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• v.17 no.2
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• pp.55-61
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• 2023

With femtosecond (fs) laser pulse irradiation on metals, various types of nano- and micro-scale structures can be naturally induced at the surface through laser-matter interaction. Two notable structures are laser-induced periodic surface structures (LIPSSs) and cone/spike structures, which are known to significantly modify the optical and physical properties of metal surfaces. In this work, we irradiate fs laser pulses onto various types of metals, cold-rolled steel, pickled & oiled steel, Fe-18Cr-8Ni alloy, Zn-Mg-Al alloy coated steel, and pure Cu which can be useful for precise molding and imprinting processes, and adjust the morphological profiles of LIPSSs and cone/spike structures for clear structural coloration and a larger range of surface wettability control, respectively, by changing the fluence of laser and the speed of raster scan. The periods of LIPSSs on metals used in our experiments are nearly independent of laser fluence. Accordingly, the structural coloration of the surface with LIPSSs can be optimized with the morphological profile of LIPSSs, controlled only by the speed of the raster scan once the laser fluence is determined for each metal sample. However, different from LIPSSs, we demonstrate that the morphological profiles of the cone/spike structures, including their size, shape, and density, can be manipulated with both the laser fluence and the raster scan speed to increase a change in the contact angle. By injection molding and imprinting processes, it is expected that fs laser-induced surface structures on metals can be replicated to the plastic surfaces and potentially beneficial to control the optical and wetting properties of the surface of injection molded and imprinted products.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.38.3-38.3
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• 2021

We are developing an optomechanical design of infrared telescope for the CubeSat and Unmanned Aerial Vehicle (UAV) which adapts the Linear Astigmatism Free- Three Mirror System in the confocal off-axis condition. The small entrance pupil (diameter of 40 mm) and the fast telescope (f-number of 1.9) can survey large areas. The telescope structure consists of three mirror modules and a sensor module, which are assembled on the base frame. The mirror structure has duplex layers to minimize a surface deformation and physical size of a mirror mount. All the optomechanical parts and three freeform mirrors are made from the same material, i.e., aluminum 6061-T6. The Coefficient of Thermal Expansion matching single material structure makes the imaging performance to be independent of the thermal expansion. We investigated structural characteristics against external loads through Finite Element Analysis. We confirmed the mirror surface distortion by the gravity and screw tightening, and the overall contraction/expansion following the external temperature environment change (from -30℃ to +30℃).

• Journal of the Korea Convergence Society
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• v.8 no.12
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• pp.299-305
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• 2017

This study relates to the development of a program for calculating the design data and estimating on the Abbe-$K{\ddot{o}}nig$ prism. First, we set the Abbe-$K{\ddot{o}}nig$ prism design variables and derive the relational expressions between them. With this expressions, we could develope the program that outputs the numerical data for the Abbe-$K{\ddot{o}}nig$ prism design and three evaluation data for the Abbe-$K{\ddot{o}}nig$ prism analysis when the face-length, the effective convergent incident angle of incident beam, and the refraction index of prism are given. In fact, applying this program to the prism which is not the commercial size, we were able to calculate the design data very quickly, and we could easily understand the optical structure of the designed Abbe-$K{\ddot{o}}nig$ prism by the three evaluation data. This means that we can quickly ensure the structural data of the Abbe-$K{\ddot{o}}nig$ prism which is required for the product development.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.197-203
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• 2001

Micro-defects induced by design and production failure or working environments are known as the cause of SCC(Stress Corrosion Cracking) in aged structures. Therefore, the evaluation of structural integrity based on micro-cracks is required not only a manufacturing step but also in-service term. So we introduce a new nondestructive inspection method using the magneto-optical film to detect micro-cracks. The method has some advantage such as high testing speed, real time data acquistion and the possibility of remote sensing by using of a magneto-optical film that takes advantage of the change of magnetic domains and domain walls. This paper introduces the concept of the new nondestructive inspection method using the magneto-optical film, also proves the possibility of this method as a remote testing system under oscillating load considering application on real fields by applying the method to four types of specimens.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.302-307
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• 1998

In the production of semiconductor wafer, optical and electron microscopes, ion-beam, laser device must maintain their alignments within a sub-micrometer. This equipment requires a vibration free environment to provide its proper function. Especially, lithography and inspection devices, which have sub-nanometer class high accuracy and resolution, have come to necessity for producing more improved giga and tera class semiconductor wafers. This high technology equipments require very strict environmental vibration standard, vibration criteria, in proportion to the accuracy of the manufacturing, inspecting devices. The vibration criteria of high sensitive equipment should be represented in the form of exactness and accuracy, because this is used as basic data for the design of building structure and structural dynamics of equipment. The study on the evaluation of the factors affecting the permissible vibration criteria is required to design the efficient isolation system of the semiconductor manufacturing of equipment. This paper deals with the properties of the effected factor for vibration criteria of high sensitive equipment.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.9
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• pp.495-501
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• 2000

This paper presents a method to minimize the initial deflection of a multi-layer piezoelectric microactuator without loosing its piezoelectric deflection performance required for light modulating micromirror devices. The multi-layer piezoelectric actuator composed of PZT silicon nitride and platinum layers deflects or buckles due to the gradient of residual stress. Based on the structural analysis results and relationship between process conditions and mechanical properties we have modified the fabrication process and the thickness of thin film layers to reduce the initial residual stress deflection without decreasing its piezoelectric deflection performance. The modified designs fabricated by surface-micromachining process achieved the 77% reduction of the initial deflection compared with that of the conventional method based on the measured micromechanical material properties is applicable to the design refinement of multi-layer MEMS devices and micromechanical structures.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.1
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• pp.8-14
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• 2018

Printed circuit heat exchangers (PCHEs) are widely used with an increasing demand for industrial applications. PCHEs are capable of operating at high temperatures and pressure. We consider a PCHE as a candidate intermediate heat exchanger type for a high temperature gas-cooled reactor (HTGR). For conventional application using stainless steels, design and manufacturing of PCHEs are well established. For applications to HTGR, knowledge of longitudinal conduction and deformation of channel is required to estimate design margin. This paper analyzes the effects of longitudinal conduction and deformation of channel on thermal performance using a code internally developed for design and analysis of PCHEs. The code has a capability of two dimensional simulations. Longitudinal conduction is estimated using the code. In HTGR operating condition, about ten percent of design margin is required to compensate thermal performance. The cross-sectional images of PCHE channels are obtained using an optical microscope. The images are processed with computer image process technique. We quantify the deformation of channel with dimensional parameters. It is found that the deformation has negative effect on structural integrity. The deformation enhances thermal performance when the shape of channel is straight in laminar flow regime. It reduces thermal performance in cases of a zigzag channel and turbulent flow regime.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.851-856
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• 2005

The precision fabrication of aspherical lenses is increasingly required for the latest applications of compact and high resolution video-recording or camera systems. Micro-optical components, including micro-spherical or aspherical lenses and reflecting mirrors, are generally required to be manufactured with high shape accuracy, extremely low surface roughness and no surface damage. To meet the needs of the precision fabrication system, a bed which supports the micro aspherical lens fabrication machines stably and safely is required. In this study, the thickness of the ribs of the bed is optimized using the CAD integrated optimal design system, a virtual DS program.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.98-105
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• 2018

The satellite is exposed to various launch environments such as random vibrations and shock. Accordingly, structural design of electronic equipment mounted on satellite must meet reliability requirements at the box level. In addition, it is essential to secure the reliability of the solder joint applied to electronic equipment. In this paper, we performed a modal and quasi-static analysis for the purpose of satisfaction of the design requirements of the CCB (Camera Controller Box) present on the 500 kg-class compact advanced satellite (CAS500). In addition, structural safety of electronic components was verified by the Steinberg's method and random equivalent static analysis.