• 한국CDE학회논문집
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• 제13권4호
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• pp.296-304
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• 2008

Recently, various attempts are being done to apply off-line programming system to field of paint robot. But most commercial simulation softwares have problems that are slow simulation speed and not support various painting paramenters on simulation. This paper proposes enhanced paint simulation method for off-line programming system. For these, this method used the mathematical model of flux field from a previous research. The flux field has the flux distribution function, which reflects on the feature of paint spray. A previous research derived this flux distribution function for an integral function and calculated paint thickness function for an integral function. But if flux distribution function is defined as an integral function, it is inadequate to use for real-time simulation because a number of calculation is needed for estimation of paint thickness distribution. Therefore, we defined the flux distribution function by numerical method for reducing a mount of calculation for estimation of paint thickness. We derived the equation of paint thickness function analytically for reducing a mount of calculation from the paint distribution function defined by numerical method. In order to prove proposed paint simulation method this paper compares the simulated and measured thickness. From this comparison this paper show that paint thickness distribution is predicted precisely by proposed spray paint simulation process.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.59-60
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• 2022

When a metal sprayed film of several hundred ㎛ on the concrete surface is possible to 80 dB of shielding effect electromagnetic waves (ElectroMagnetic Pulse, EMP). Therefore, in this study, as a way to secure EMP shielding performance by applying a metal spray coating showing excellent EMP shielding performance to a concrete structure, the metal spray welding efficiency and thin film adhesion performance according to the concrete spray direction and surface treatment method were evaluated. Metal sprayed efficieny according to the metal spraying direction and method was confirmed that the difference was insignificant by applying the roughening agent. However, the method of strengthening the concrete surface and applying the sealing agent show maximum adhesion strength of 3.98 MPa compared to other methods, and it is judged that this method can be utilized for the metal spraying method for concrete EMP shielding.

• 전기화학회지
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• 제8권1호
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• pp.42-46
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• 2005

It has been known that the synthesis of the cathode materials for the lithium rechargeable batteries by the sol-gel process has many advantages over the conventional solid-state method. It has been, however, a continuing issue that new additional steps should be introduced to commercialize this process. In this work, spray drying was introduced to the existing sol-gel process as a continuous mass production method of the pre-heat treatment precursor materials. The precursors of $LiCoO_2$ and $LiNi_{0.8}Co_{0.2}O_2$ were continuously produced through spray drying from the solution containing stoichiometric amount of lithium, cobalt, and nickel sources as well as a chelating agent. The process variables, such as pH of the starting solution, spray drying conditions, and calcination conditions were optimized. The XRD pattern for the synthesized material indicated a good crystallinity with a layered structure.

• 한국재료학회지
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• 제31권3호
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• pp.172-180
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• 2021

In this study, using the plasma spray method, tensile and compression fatigue tests are performed in saline solution to examine the effect of Ti undercoat on corrosion fatigue behavior of alumina-coated specimens. The alumina-coated material using Ti in the undercoat shows better corrosion fatigue strength than the base material in the entire stress amplitude range. Fatigue cracking of UT specimens occurs in the recess formed by grit-blasting treatment and progresses toward the base metal. Subsequently, the undercoat is destroyed at a stage where the deformation of the undercoat cannot follow the crack opening displacement. The residual stress of the UT specimen has a tensile residual stress up to about 100 ㎛ below the surface of the base material; however, when the depth exceeds 100 ㎛, the residual stress becomes a compressive residual stress. In addition, the inside of the spray coating film is compressive residual stress, which contributes to improving the fatigue strength characteristics. A hardened layer due to grit-blasting treatment is formed near the surface of the UT specimen, contributing to the improvement of the fatigue strength characteristics. Since the natural potential of Ti spray coating film is slightly higher than that of the base material, it exhibits excellent corrosion resistance; however, when physiological saline intrudes, a galvanic battery is formed and the base material corrodes preferentially.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1236-1245
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• 2004

In this study, an optical imaging method was developed for the measurements of the sizes and velocities of droplets in sprays. Double-exposure single-frame spray images were captured by the imaging system. An image processing program was developed for the measurements of the sizes and positions of individual particles including separation of the overlapped particles and particle tracking and pairing at two time instants. To recognize and separate overlapping particles, the morphological method based on watershed segmentation as well as separation using the perimeter and convex hull of image was used consecutively. Better results in separation were obtained by utilization of both methods especially for the multiple or heavily-overlapped particles. The match probability method was adopted for particle tracking and pairing after identifying the positions of individual particles and it produced good matching results even for large particles like droplets in sprays. Therefore, the developed optical imaging method could provide a reliable way of analyzing the motion and size distribution of droplets produced by various sprays and atomization devices.

• 대한기계학회논문집B
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• 제23권10호
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• pp.1310-1319
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• 1999

High-pressure swirl injectors have usually been employed in Gasoline direct injection engines due to their spray characteristics and the feasibility of their control. Thus the microscopic characteristics of high-pressure swirl spray were investigated by PDA. The correlation between axial and radial velocities and the correlation between droplet size and axial velocity were examined with different axial and radial positions. Two dimensional droplet velocity and its number distribution with size-classified droplets were illustrated. The mean droplet velocity and its SMD were also analyzed at the center of spray, the position having maximum mean axial velocity, and the spray periphery using time dividing method. Finally, the structure of high-pressure swirl spray was presented with the size distribution and velocity profile of droplets.

• 대한기계학회논문집B
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• 제30권4호
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• pp.381-388
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• 2006

The objective of this study is to predict the etching characteristics using spray characteristics for the optimization on the etching process of Lead-Frame. The etching characteristics such as etching factor, uniformity were investigated on the actual operating conditions. The correlation between the etching characteristics and the spray ones obtained by measurement were analyzed to simulate the etching characteristics according to actual conditions of lead-frame etching process. These conditions of lead-frame process were spray pressure, distance from nozzle tip to substrate, pipe pitch, and nozzle pitch. To improve the etching characteristics in the lead-frame process, effects of the various operating conditions should be understood in detail. The spray characteristics obtained by experiment using PDA system were simulated by the Monte-Carlo method. The etching process model was coded by Java language. It was found that simulation results generally agreed well with the measured results of etching characteristics in lead-frame etching process. The optimal operating parameters were successfully found under variable conditions.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.532-548
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• 2002

A hybrid model consisting of a modified TAB (Taylor Analogy Breakup) model and DVM (Discrete Vortex Method) is proposed for numerical analysis of the evaporating spray phenomena in diesel engines. The simulation process of the hybrid model is divided into three steps. First, the droplet breakup of injected fuel is analyzed by using the modified TAB model. Second, spray evaporation is calculated based on the theory of Siebers'liquid length. The liquid length analysis of injected fuel is used to integrate the modified TAB model and DVM. Lastly, both ambient gas flow and inner vortex flow of injected fuel are analyzed by using DVM. An experiment with an evaporative free spray at the early stage of its injection was conducted under in-cylinder like conditions to examine an accuracy of the present hybrid model. The calculated results of the gas jet flow by DVM agree well with the experimental results. The calculated and experimental results all confirm that the ambient gas flow dominates the downstream diesel spray flow.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.99-100
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• 2006

Cold gas dynamic spray or cold-spray is a deposition process, which causes deformation of a thin substrate. The deformation is usually convex to the deposited side. In this research, the main cause of the deformation was investigated using 6061-T6 aluminum alloy. The effects or anisotropic coefficient or thermal expansion (CTE) or the deposited layer by cold-spray and residual stress were studied by experiments and finite element analysis. The Hole Drilling method was applied to measure residual stress in the cold-spray layer and substrate. The data obtained by the experiments were used for the analysis of substrate deformation. From the result of the analysis, it was concluded that compressive residual stress was the main reason of substrate deformation while CTE had little effect.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.9-18
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• 2005

The objective of this study is to analyse the spray characteristics according to the injection duration under the ambient pressure condition, and the injection timing in the visualization engine. In order to investigate the spray behavior, we obtained the spray velocity using the PIV method that has been an useful optical diagnostics technology, and calculated the vorticity from spray velocity component. These results elucidated the relationship between vorticity and entropy which play an important role in the diffusion process for the early injection case and the stratification process for the late injection case. In addition, we quantified the homogeneous diffusion rate of spray using the entropy analysis based on the Boltzmann's statistical thermodynamics. Using these method, it was found that the concentration of spray droplets caused by the increase of injection duration is more effective than the increase of momentum dissipation. We also found that the homogeneous diffusion rate increased as the injection timing moved to the early intake stroke process and BTDC $50^{\circ}$ was the most efficient injection timing for the stratified mixture formation during the compression stroke.