Min-Saeng Kim

Nickel Line Patterning Using Silicon Supersonic Micronozzle Integrated with a Nanoparticle Deposition System

In this study, 3-µm- and 20-nm nickel powders were deposited on Si substrates to pattern a metal line using a nanoparticle deposition system (NPDS) at room temperature. The stand-off distance (SoD), the distance between the substrate and the end of nozzle, was varied from 300 to 1000 µm to determine its effect on deposition properties. A Ni line was successfully formed on the Si substrate. When 3-µm Ni powders were used, the thickness of the deposited layer on the Si substrate was measured to be 5.4 µm, and its width was 176.4 µm at a SoD of 300 µm. In contrast, the deposited average thickness at a SoD of 500 µm was 1.1 µm, with a width of 190.6 µm. Moreover, the deposited thickness was measured to be 6.4 µm using 20-nm Ni powders at a SoD of 300 µm. Thus, it was found that the deposited thickness decreased as SoD increased, indicating an inversely proportional relationship. For deposition behavior, depending on the size of powders, it was found that 20-nm Ni powders resulted in a thicker deposition than did 3-µm Ni powders, as momentum transfer between carrier gas and powders is inversely proportional to the powder size. Thus, as the powder size decreased, its spray velocity increased; hence, it is more effective to use nano powders for Ni line patterning. Surface resistivity of the deposited Ni line was 1.83 ×10-7 Ωm using 20-nm powders and 1.61 ×10-7 Ωm using 3-µm powders. These values are close to the standard resistivity value for bulk Ni, which is 6.9 ×10-8 Ωm, making NPDS a promising technique for metal line-fabrication equipment.

Numerical simulation and verification of a curved morphing composite structure with embedded shape memory alloy wire actuators

Shape memory alloys have been actively studied in various fields in an attempt to utilize their high energy density. In particular, shape memory alloy wire-embedded composites can be used as load-bearing smart actuators without any additional manipulation, in which they act like a hinge joint. A shape memory alloy wire-embedded composite is able to generate various deformation behaviors via the combination of its shape memory alloy and matrix materials. Accordingly, a study of the various design parameters of shape memory alloy wire-embedded composites is required to facilitate the practical application of smart structures. In this research, a numerical simulation of a shape memory alloy wire-embedded composite is used to investigate the deformation behavior of a composite panel as a function of the composite width per shape memory alloy wire, composite thickness, and the eccentricity of the shape memory alloy wire. A curved morphing composite structure is fabricated to confirm the results of the numerical simulation. The deformation of the shape memory alloy wire-embedded composite panel is determined by measuring its radius of curvature. The simulated deformation behaviors are verified with the experimental results. In addition, an analysis of the deformation and internal stress of the composites is carried out. It can be used to obtain guidelines for the mechanical design of shape memory alloy wire-embedded composite panels.

Fabrication of a smart air intake structure using shape memory alloy wire embedded composite

Shape memory alloys (SMAs) have been actively studied in many fields utilizing their high energy density. Applying SMA wire-embedded composite to aerospace structures, such as air intake of jet engines and guided missiles, is attracting significant attention because it could generate a comparatively large actuating force. In this research, a scaled structure of SMA wire-embedded composite was fabricated for the air intake of aircraft. The structure was composed of several prestrained Nitinol (Ni–Ti) SMA wires embedded in -shape glass fabric reinforced plastic (GFRP), and it was cured at room temperature for 72 h. The SMA wire-embedded GFRP could be actuated by applying electric current through the embedded SMA wires. The activation angle generated from the composite structure was large enough to make a smart air intake structure.

Numerical simulation of hybrid composite shape-memory alloy wire-embedded structures

The large recovery force and non-linear deformation behaviour resulting from a change in the temperature in shape-memory alloys (SMAs) make them attractive materials for applications in smart materials and structures, as well as actuators. However, SMAs are limited in their application because they cannot support general loads such as bending or compression. SMA wire-embedded composite materials, where materials such as glass fibre reinforced plastics (GFRPs) are combined with SMAs, are proposed to overcome these limitations. However, the increased stiffness of GFRPs limits the deformation that can be achieved. The inclusion of more compliant materials, such as silicon rubber, into the matrix can improve the achievable deformation, and the characteristics of the resulting hybrid composite can be controlled by varying the conformation of the material. In this study, a numerical simulation method was developed to predict the deformation behaviour of SMA wire-embedded hybrid composites. To verify the simulation procedure, several conformations of SMA wire-embedded hybrid composites were fabricated, and their deformation behaviours were compared with the simulation results. The simulation was then used to achieve a favourable trade-off between the stiffness and the achievable deformation of the structure.

Structure Evaluation for the Level Luffing Crane' Boom

Abstract Structure evaluation for 70/15 T×105 m LLC(Level Luffing Crane)’s boom was conducted by Finite Element Method. Boom modeled with beam element was fixed by luff rope and boom mount and was received loads from self weight, luff hoisting, traveling motion, slewing motion, and wind force, etc. These applied loads were calculated using various factors presented in the reference standards and were inputted in the analysis model after considering about the adverse conditions of LLC. In the research, deformation, stresses, buckling of boom were evaluated by ANSYS. Structural safety of boom was confirmed in the results of numerical analysis. 기호설명 K : 후크의 하중조건, 하중횟수에 따른 효 β 율 계수(duty factor) Ψ : 리프트 작동에 의한 발생되는 충격계 수 (impact factor) F i : 관성력(N) W i : 호이스팅 하중과 구성품 질량(kg) G : 중력 가속도(m/s 2 ) Q : 풍하중에서의 속도압(N/m 2 ) C : 풍력계수 A : 파이프의 2단면적(m ) β TL : 주행(Traveling)시 발생되는 관성력에 의한 계수 SL : 선회(Slewing)시 발생되는 관성력에 의한 계수

Nano/micro particle beam for ceramic deposition and mechanical etching

Nano/micro particle beam (NPB) is a newly developed ceramic deposition and mechanical etching process. Additive (deposition) and subtractive (mechanical etching) processes can be realized in one manufacturing process using ceramic nano/micro particles. Nano- or micro-sized powders are sprayed through the supersonic nozzle at room temperature and low vacuum conditions. According to the process conditions, the ceramic powder can be deposited on metal substrates without thermal damage, and mechanical etching can be conducted in the same process with a simple change of process conditions and powders. In the present work, ceramic aluminum oxide (Al2O3) thin films were deposited on metal substrates. In addition, the glass substrate was etched using a mask to make small channels. Deposited and mechanically etched surface morphology, coating thickness and channel depth were investigated. The test results showed that the NPB provides a feasible additive and subtractive process using ceramic powders.

Structural Analysis for a 70/15 ton×105 m Level Luffing Crane

Evaluation of the structural analysis for a 70/15 ton×105 m LLC (Level Luffing Crane) was conducted with an FEM Tool. Due to a discordance of the modeling and element type, the LLC was progressively analyzed after dividing it into the boom, main structure and rocker. All loads such as slewing, traveling and wind load, etc., that are indicated in the reference standards, were inputted as various severe conditions of the LLC. The deformation, equivalent stress(Von Mises stress), buckling characteristics were evaluated for the LLC structures. The stress concentrated areas over the allowable stress were identified, and reinforcement work was performed with a stiffener.

COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF FABRICATED MICRONOZZLE FOR SUPERSONIC PARTICLE DEPOSITION

A micronozzle was applied in nanoparticle deposition system (NPDS) for supersonic deposition. To determine whether suitable behavior of supersonic fluid can be produced or not, computational fluid dynamics (CFD) flow analysis was used. Ni particles were successfully deposited using the fabricated micronozzle in NPDS at room temperature. It was found that shorter micronozzle with larger side profile deposits wide and thick film compared to the deposition using long micronozzle with smaller side profile. These experimental results agree with the simulation results.