• Title/Summary/Keyword: Heat treatment simulation

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Modeling of Flame Acceleration Considering Complex Confinement Effects in Combustible Gas Mixture (가연성 기체 혼합물에서 복잡한 구조에 따른 화염 가속 모델링)

  • Gwak, Min-Cheol;Yoh, Jai-Ick
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.3
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    • pp.315-324
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    • 2012
  • This paper presents a numerical investigation of the deflagration-to-detonation transition (DDT) of flame acceleration by a shock wave filled with an ethylene/air mixture as the combustible gas, considering geometrical changes by using obstacles and bent tubes. The model used consists of the reactive compressible Navier-Stokes equations and the ghost fluid method (GFM) for complex boundary treatment. Simulations with a variety of bent tubes with obstacles show the generation of hot spots through flame and strong shock-wave interactions, and restrained or accelerated flame propagation due to geometrical effects. In addition, the simulation results show that the DDT occurs with a nearly constant chemical heat-release rate of 20 MJ/($g{\bullet}s$) in our numerical setup. Furthermore, the DDT triggering time can be delayed by the absence of unreacted material together with insufficient pressures and temperatures induced by different flame shapes, although hot spots are formed in the same positions.

Thermal Elasto-Plastic Deformation Analysis of Metal Matrix Composites Considering Residual Stress and Interface Bonding Strength (잔류응력과 계면접합강도를 고려한 금속복합재료의 열탄소성 변형 해석)

  • Kang, Chung-Gil;Seo, Young-Ho
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.1 s.94
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    • pp.227-237
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    • 1999
  • As the interface bonding phenomenon between the matrix and the reinforcements has a large effect on the mechanical properties of MMCs, a sugestion of the strength analysis technique considering the residual stress and the interface bonding phenomenon is very important for the design of pans and the estimation of fatigue behavior. In this paper the three dimensional finite element anaysis is performed during the elasto-plastic deformation of the particulate reinforced metal matrix composites. It was analyzed with the volume fractions in view of microscale. Bonding strength. interface separation and matrix void growth between the matrix and the reinforcements will be predicted on deformation under tensile loading. An interface seperation is estimated by the fracture criterion which is a critical value of generalized plastic work per unit volume. The shape of the reinforcement is assumed to be a perfect sphere. And the type of the reinforcement distribution is assumed as FCC array. The thermal residual stress in MMCs is induced by the heat treatment. It is included at the simulation as an initial residual stress. The element birth and death method of the ANSYS program is used for the estimation of the interface bonding strength, void generation and propagation. It is assumed that the fracture in the matrix region begin to occur under the external loading when the plastic work per unit volume is equal to the critical value. The fracture strain will be defined. The experimental data of the extruded $SiC_p$>/606l Al composites are compared with the theoretical results.

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Study of Focusing Characteristics of Ultrasound for Designing Acoustic Lens in Ultrasonic Moxibustion Device (뜸 자극용 초음파 치료기기의 음향렌즈 설계를 위한 초음파 집속 특성 연구)

  • Bae, Jae-Hyun;Song, Sung-Jin;Kim, Hak-Joon;Kim, Ki-Bok
    • Journal of the Korean Society for Nondestructive Testing
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    • v.35 no.2
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    • pp.134-140
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    • 2015
  • Traditional moxibustion therapy can cause severe pain and leave scarring burns at the moxibustion site as it relies on the practitioner's subjective and qualitative treatment. Recently, ultrasound therapy has received attention as an alternative to moxibustion therapy owing to its objectiveness and quantitative nature. However, in order to convert ultrasound energy into heat energy, there is a need to precisely understand the ultrasound-focusing characteristics of the acoustic lens. Therefore, in this study, an FEM simulation was performed for acoustic lenses with different geometries a concave lens and zone lens as the geometry critically influences ultrasound focusing. The acoustic pressure field, amplitude, and focal point were also calculated. Furthermore, the performance of the fabricated acoustic lens was verified by a sound pressure measurement experiment.

Evaluation of Analytical Method for Detent Spring Force Correction (디텐트 스프링 교정을 위한 해석적방법의 적용성 평가)

  • Kim, Sun-Ho;Kwon, Hyuk-Hong;Park, Kyoung-Taik;Jung, Yong-Hun
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.4 s.97
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    • pp.57-63
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    • 1999
  • A thin metal plate such as detent spring has the shape deformation due to the phenomenon of spring back after press machining and heat treatment process. This requires the correction of spring shape and force in final inspection process. To do correction of the shape deformation the impact force is manually applied to the bended part of detent spring after measuring the shape deformation and spring force. To develop the automatic spring force correction system, applied force of occurring plastic deformation must be derived from the experimental method. But frequent change of spring shape and material makes it difficult to accomplish the experimental method to be applied. This paper describes the analytical method for detent spring force correction system is to be substituted for the experimental method. FEM(Finite Element Method) is used to find the boundary value between elastic and plastic deformation in the analytical method. To confirm the validity of the analytical method, the result of two methods is compared each other at various applied force conditions. It shows that the simulation result of the analytical method is consistent with the result of the experimental method within the error bound ${\pm}$5%. The result of this paper is useful for development of the automatic spring correction system and reduction of the complicated and tedious processes involved in experimental method.

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Strategic Direction and Road Map of Expanding Prevention of Winter Disease in the Summer (동병하치 확산을 위한 전략적 방향과 이행방안)

  • Song, Ho-Sueb
    • Journal of Acupuncture Research
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    • v.27 no.3
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    • pp.147-157
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    • 2010
  • Objectives : The purpose of this study was to propose appropriate strategic directions and road maps for successful achievement of programs preventing winter disease in the summer. Methods : Details on programs preventing winter disease in the summer such as clear concept, theoretical basis, current status, intervention or available prescriptions and indication/contraindication/caution were prepared through the related journal review, upon which an observational study was devised and done for simulation to find out even a trivial problem and to guarantee the safety beforehand. The experimental group was divided into 5 groups by the size of pill and the way ginger is treated; 1cm pill with ginger group, 3cm pill group without ginger, 3cm pill group dipped into ginger, 3cm pill group applying ginger to acupoints and 3cm pill group with ginger Results 1. program preventing winter disease in the summer was defined as representative winter diseases such as common cold, influenza, chronic asthma, chronic bronchitis, allergic rhinitis, emphysema, chronic gastritis and rheumatoid arthritis, and preventive care in the summer, reinforcing deficient yang qi of five viscera by using exuberant yang qi from summer heat. 2. It was based upon historically established theories which is 'nourishing yang qi in the spring and summer', 'long summer, namely rainy spell in the summer overwhelms the winter, because of earth winning water according to the five phases theory' and 'To replenish yang qi is major principle to treat winter diseases, which can be most appropriately and timely applied to the patient with deficient yang qi of five viscera inherently, especially in the three dog days of the summer, because of exuberant exterior yang qi and deficient interior yang qi in the five viscera'. 3. In the adjacent China and Taiwan, acupoint applying method in the three dog days named 'San Fu Tie' have been stirring a boom throughout the nation, in which Xiaochuan Gao was used as a basic prescription and it mainly was applied at bilateral $BL_{13}$, $_{15}$ and $_{17}$ for about 4 hours. As far as domestic current status, the necessity of adopting the above method prior to Herbal formula was also recognised, because not a few koreans have apprehension for the safety of it including medicinal herbs and are reluctant to take it any more due to negative advertisement of narrow minded doctors' association. 4. Indication of acupoint applying method in the three dog days included most of winter diseases such as common cold, influenza, chronic asthma, chronic bronchitis, allergic rhinitis, emphysema, chronic gastritis. contraindication was pregnant woman and the weak such as infants and the old. More attention was paid to grasp firmly the normal reaction following the treatment for preventing side effect and teasing blister. recommendation was also given to abstain from food inducing phlegm and dampness such as meat, shrimp and crab as well as cold drinks and foods 5. In the simulation observational study based upon the above findings following review the related articles, no blister was shown on the acupoints icluding bilateral $BL_{13}$, $_{15}$ and $_{17}$ in every experimental group during 24hr observation following the acupoint applying treatment with pills made by modified and devised prescription. At 4 hr, the effectiveness of it reached a peak showing redness and mild tenderness and there is little difference between groups 3cm pills groups regardless of the way ginger was treated. abdominal distention and growling was found in all the volunteers during the treatment at CV 8. Strategic directions and road maps : Through successful fulfillment of the program preventing winter disease in the summer, Korean traditional medicine should be integrated into mainstream national health care services. Cultural access was thought to be as important as Scientific EBM approach. First of all, To evoke potential cultural homogeneity from campaigns and press advertisement was needed for promoting public awareness about preventing winter disease in the summer by enhancing immunity via acupoint applying treatment in the three dog days, and then indigenous name as Sambokcheop, protocol, Clinical Research Form for data collection of it should be developed and prepared. Once the first step was taken this summer, through a thorough data collection and scrutinized scientific evaluation, drawbacks should be compensted for and the efficacy and safety should be substantiated.

Typhoon Simulation with a Parameterized Sea Surface Cooling (모수화된 해면 냉각을 활용한 태풍 모의 실험)

  • Lee, Duho;Kwon, H. Joe;Won, Seong-Hee;Park, Seon Ki
    • Atmosphere
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    • v.16 no.2
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    • pp.97-110
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    • 2006
  • This study investigates the response of a typhoon model to the change of the sea surface temperature (SST) throughout the model integration. The SST change is parameterized as a formulae of which the magnitude is given as a function of not only the intensity and the size but the moving speed of tropical cyclone. The formulae is constructed by referring to many previous observational and numerical studies on the SST cooling with the passage of tropical cyclones. Since the parameterized cooling formulae is based on the mathematical expression, the resemblance between the prescribed SST cooling and the observed one during the period of the numerical experiment is not complete nor satisfactory. The agreements between the prescribed and the observed SST even over the swath of the typhoon passage differ from case to case. Numerical experiments are undertaken with and without prescribing the SST cooling. The results with the SST cooling do not show clear evidence in improving the track prediction compared to those of the without-experiments. SST cooling in the model shows its swath along the incomplete simulated track so that the magnitude and the distribution of the sea surface cooling does not resemble completely with the observed one. However, we have observed a little improvement in the intensity prediction in terms of the central pressure of the tropical cyclone in some cases. In case where the model without the SST treatment is not able to yield a correct prediction of the filling of the tropical cyclone especially in the decaying stage, the pulling effect given by the SST cooling alleviates the over-deepening of the model so that the central pressure approaches toward the observed value. However, the opposite case when the SST treatment makes the prediction worse may also be possible. In general when the sea surface temperature is reduced, the amount of the sensible and the latent heat from the ocean surface become also reduced, which results in the weakening of the storms comparing to the constant SST case. It turns out to be the case also in our experiments. The weakening is realized in the central pressure, maximum wind, horizontal temperature gradient, etc.

Numerical Simulation for the Quasi-static Behavior of Superelastic Nitinol Shape Memory Alloys (SMAs) (초탄성 니티놀 형상기억합금의 준정적 거동에 대한 수치해석적 재현)

  • Hu, Jong Wan
    • Journal of Korean Society of Steel Construction
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    • v.27 no.6
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    • pp.493-501
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    • 2015
  • Superelastic shape memory alloys (SMAs) are metallic materials that can automatically recover to their original condition without heat treatment only after the removal of the applied load. These smart materials have been wildly applied instead of steel materials to the place where large deformation is likely to concentrate. In spite of many advantages, superelastic SMA materials have been limited to use in the construction filed because there is lack of effort and research involved with the development of the material model, which is required to reproduce the behavior of superelastic SMA materials. Therefore, constitutive material models as well as algorithm codes are mainly treated in this study for the purpose of simulating their hysteretic behavior through numerical analyses. The simulated curves are compared and calibrated to the experimental test results with an aim to verify the adequacy of material modeling. Furthermore, structural analyses incorporating the material property of the superelastic SMAs are conducted on simple and cantilever beam models. It can be shown that constitutive material models presented herein are adequate to reliably predict the behavior of superelastic SMA materials under cyclic loadings.

Fabrication of Piezoresistive Silicon Acceleration Sensor Using Selectively Porous Silicon Etching Method (선택적인 다공질 실리콘 에칭법을 이용한 압저항형 실리콘 가속도센서의 제조)

  • Sim, Jun-Hwan;Kim, Dong-Ki;Cho, Chan-Seob;Tae, Heung-Sik;Hahm, Sung-Ho;Lee, Jong-Hyun
    • Journal of Sensor Science and Technology
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    • v.5 no.5
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    • pp.21-29
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    • 1996
  • A piezoresistive silicon acceleration sensor with 8 beams, utilized by an unique silicon micromachining technique using porous silicon etching method which was fabricated on the selectively diffused (111)-oriented $n/n^{+}/n$ silicon subtrates. The width, length, and thickness of the beam was $100\;{\mu}m$, $500\;{\mu}m$, and $7\;{\mu}m$, respectively, and the diameter of the mass paddle (the region suspended by the eight beams) was 1.4 mm. The seismic mass on the mass paddle was formed about 2 mg so as to measure accelerations of the range of 50g for automotive applications. For the formation of the mass, the solder mass was loaded on the mass paddle by dispensing Pb/Sn/Ag solder paste. After the solder paste is deposited, Heat treatment was carried out on the 3-zone reflow equipment. The decay time of the output signal to impulse excitation of the fabricated sensor was observed for approximately 30 ms. The sensitivity measured through summing circuit was 2.9 mV/g and the nonlinearity of the sensor was less than 2% of the full scale output. The output deviation of each bridge was ${\pm}4%$. The cross-axis sensitivity was within 4% and the resonant frequency was found to be 2.15 KHz from the FEM simulation results.

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