• Title/Summary/Keyword: cavity pressure

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Cavity Design for Injection Molded Gears by the Compensation Method of Design Parameters (설계인자 보정방법에 의한 사출성형기어의 캐비티 설계)

  • Lee, Sung-Chul;Kim, Choong-Hyun;Kwon, Oh-Kwan;Huh, Yong-Jeong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.10
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    • pp.3142-3151
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    • 1996
  • As plastics shrink when changing from a molten to a solid state, mold cavities must by made larger than the product specification, In making molded gears, the teeth in the cavity must be carefully compensated for shrinkage so that the teeth of gears will have the correct profile. Two compensation methods are widely used in the cavity design. One is the compensation of a module and the other is the modification of a pressure angle and profile shifting coefficient. These methods, however, do not provide a gear cavity with all disign parameters for gears and several parameters are determined by experience. In this paper, the new design technique, namely the compensation method of design parameters, was proposed , which is based on the three kinds of shrinkage rates obtained from the measuring data of the prototype of molded gears. Using the shrinkage rates in the tip circle, tooth heigth and tooth thickness, we calculate the whole design parameters of a gear cavity. Thus, the gear cavity is considered as a complete gear with the compensated module, pressure angle, profile shifting coefficient, clearance coefficient and back lash amount so that the formula of gears can be applied to the cavity design effectively. Experimental results show that more precision molded gears can be made by using the proposed design method.

Inducer Design to Avoid Cavitation Instabilities

  • Kang, Dong-Hyuk;Watanabe, Toshifumi;Yonezawa, Koichi;Horiguchi, Hironori;Kawata, Yutaka;Tsujimoto, Yoshinobu
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.4
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    • pp.439-448
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    • 2009
  • Three inducers were designed to avoid cavitation instabilities. This was accomplished by avoiding the interaction of tip cavity with the leading edge of the next blade. The first one was designed with extremely larger leading edge sweep, the second and third ones were designed with smaller incidence angle by reducing the inlet blade angle or increasing the design flow rate, respectively. The inducer with larger design flow rate has larger outlet blade angle to obtain sufficient pressure rise. The inducer with larger sweep could suppress the cavitation instabilities in higher flow rates more than 95% of design flow coefficient, owing to weaker tip leakage vortex cavity with stronger disturbance by backflow vortices. The inducer with larger outlet blade angle could avoid the cavitation instabilities at higher flow rates, owing to the extension of the tip cavity along the suction surface of the blade. The inducer with smaller inlet blade angle could avoid the cavitation instabilities at higher flow rates, owing to the occurrence of the cavity first in the blade passage and its extension upstream. The cavity shape and suction performance were reasonably simulated by three dimensional CFD computations under the steady cavitating condition, except for the backflow vortex cavity. The difference in the growth of cavity for each inducer is explained from the difference of the pressure distribution on the suction side of the blades.

Evaluation of failure and Design criteria for the pressrue vessel (압력용기의 설계기준 및 손상 평가)

  • Oh Hwansup;Jung Hyojin;Pak Sangpil;Son Duik
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2005.05a
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    • pp.228-233
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    • 2005
  • The damage of the pressure courage by degradation can become the reason of unexpected break down or failure accident and it is very important because safety accident, the production loss, environmental pollution, social problems are occur. Consequently The result to investigat of failure accident for domestic pressure vessel, the factor of degradation is SCC, Sorrosion, Cavity, Crack.

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MOLTEN CORIUM DISPERSION DURING HYPOTHETICAL HIGH-PRESSURE ACCIDENTS IN A NUCLEAR POWER PLANT (원자로 노심 용융물의 고압분출 및 비산 현상에 대한 수치해석적 연구)

  • Kim, Jong-Tae;Kim, Sang-Baik;Kim, Hee-Dong;Jeong, Jae-Sik
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.121-128
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    • 2009
  • During a hypothetical high-pressure accident in a nuclear power plant (NPP), molten corium can be ejected through a breach of a reactor pressure vessel (RPV) and dispersed by a following jet of a high-pressure steam in the RPV. The dispersed corium is fragmented into smaller droplets in a reactor cavity of the NPP by the steam jet and released into other compartments of the NPP by a overpressure in the cavity. The fragments of the corium transfer thermal energy to the ambient air in the containment or interact chemically with steam and generate hydrogen which may be burnt in the containment. The thermal loads from the ejected molten corium on the containment which is called direct containment heating (DCH) can threaten the integrity of the containment. DCH in a NPP containment is related to many physical phenomena such as multi-phase hydrodynamics, thermodynamics and chemical process. In the evaluation of the DCH load, the melt dispersion rates depending on the RPV pressure are the most important parameter. Mostly, DCH was evaluated by using lumped-analysis codes with some correlations obtained from experiments for the dispersion rates. In this study, MC3D code was used to evaluate the dispersion rates in the APR1400 NPP during the high-pressure accidents. MC3D is a two-phase analysis code based on Eulerian four-fields for melt jet, melt droplets, gas and water. The dispersion rates of the corium melt depending on the RPV pressure were obtained from the MC3D analyses and the values specific to the APR1400 cavity geometry were compared to a currently available correlation.

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Film Insert Molding of Automotive Door Grip Using Injection-Compression Molding (사출압축성형을 이용한 자동차용 도어그립 필름인서트성형)

  • Lee, Ho Sang;Yoo, Young Gil;Kim, Tae An
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.7
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    • pp.771-777
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    • 2014
  • Injection-compression molding was used for film insert molding of an automotive door grip using films with three-dimensional embossed patterns. A vacuum mold was fabricated for vacuum-assisted thermoforming of the film, and an injection-compression mold was developed for film insert molding. Three pressure transducers were installed inside the mold cavity to measure cavity pressures. Injection-compression molding experiments under various compression strokes and toggle speeds were performed to investigate their effects on the cavity pressure and heights of the embossed patterns. The compression stroke of 0.9mm and low toggle speed resulted in a higher degree of conservation of embossed patterns. Additionally, the processing conditions for the maximum heights of embossed patterns were almost similar to those for minimum integral value of cavity pressures. The injection-compression molding process presents the opportunity to impart a soft-touch feeling of plastic parts printed with embossed patterns.

Experimental study on the mechanical response and failure behavior of double-arch tunnels with cavities behind the liner

  • Zhang, Xu;Zhang, Chengping;Min, Bo;Xu, Youjun
    • Geomechanics and Engineering
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    • v.20 no.5
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    • pp.399-410
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    • 2020
  • Cavities often develop behind the vault during the construction of double-arch tunnels, generally in the form of various defects. The study evaluates the impact of cavities behind the vault on the mechanical and failure behaviors of double-arch tunnels. Cavities of the same sizes are introduced at the vault and the shoulder close to the central wall of double-arch tunnels. Physical model tests are performed to investigate the liner stress variation, the earth pressure distribution and the process of progressive failure. Results reveal that the presence of cavities behind the liner causes the re-distribution of the earth pressure and induces stress concentration near the boundaries of cavities, which results in the bending moments in the liner inside the cavity to reverse sign from compression to tension. The liner near the invert becomes the weak region and stress concentration points are created in the outer fiber of the liner at the bottom of the sidewall and central wall. It is suggested that grouting into the foundation soils and backfilling injection should be carried out to ensure the tunnel safety. Changes in the location of cavities significantly impact the failure pattern of the liner close to the vault, e.g., cracks appear in the outer fiber of the liner inside the cavity when a cavity is located at the shoulder close to the central wall, which is different from the case that the cavity locates at the vault, whereas changes in the location of cavities have a little influence on the liner at the bottom of the double-arch tunnels.

A study on Characteristics of Molten Metal Flow in Vacuum DieCasting by Numerical Analysis (수치해석에 의한 진공다이캐스팅에서의 용탕 유동특성 연구)

  • Park, Jin-Young;Lim, Kwan-Woo;Lee, Kwang-Hak;Kim, Sung-Bin;Kim, Eok-Soo;Park, Ik-Min
    • Journal of Korea Foundry Society
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    • v.27 no.4
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    • pp.153-158
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    • 2007
  • Molten metal flow in vacuum die casting was characterized by a numerical analysis. The VOF method was used to simulate the filling behaviors of molten metal during filling process. The various vacuum degrees of no vacuum(760 mmHg), 650, 500, 250 and 60mmHg were artificially applied in cavity. And the filling behaviors of molten metal with the applied vacuum conditions were simulated and compared with those of experiment. The results showed that molten metal was partially filled into cavity when vacuum was applied and the filling length of molten metal in cavity was increased with increasing applied reduced pressure in cavity. Also, the simulated filling behaviors of molten metal were apparently similar to those of experiment, indicating the numerical analysis developed in this study was highly effective. Through the result of fluid flow simulation, both relation equations of filling length and filling velocity with the variation of pressure conditions in cavity were calculated respectively and the internal gas contents of casting was significantly reduced by the modification of vacuum gate system.

Numerical Investigation on Cavity-Enhanced-Supersonic Combustion Engine of Upstream Fuel Injection in Cavity (공동내부 연료분사방식 초음속 연소기의 수치해석 연구)

  • Jeong, Eun-Ju;Jeung, In-Seuck
    • 한국연소학회:학술대회논문집
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    • 2003.05a
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    • pp.35-39
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    • 2003
  • A numerical study is carried out to investigate combustion phenomena in a model SCRamjet engine, which has been experimentally studied at the Australian National University using a T3 free-piston shock tunnel. The Mach number is 3.8, the static pressure 110kPa and the static temperature 1100K in the main air flow. The fuel is hydrogen, which is injected in the cavity. Equivalence ratio is set to either 0.25 or 0.5 to access its effect on the fuel-air mixing combustion phenomena. The results show that the cavity generates several recirculation zones, which increase the fuel-air mixing. Self ignition occurs near the point of fuel injection. The flame is anchored by the cavity and generates the precombustion shock on the step. For a high equivalence ratio, the recirculation zones are bigger and the flame is present throughout the combustor.

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Tire Cavity Noise Reducing Material Development (타이어 공명 소음 저감체 개발)

  • Lee, Sang-Ju;Kang, Hyun-Seok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.11a
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    • pp.658-661
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    • 2008
  • Vibrations transmitted through rolling tire are major sources of road noise in vehicle interior on the range of $0{\sim}500Hz$. Among various road noises, tire cavity noise makes many problems recently. Vehicle NVH performance has improved better and road surfaces are made well. But tires are changed to high inches and low series. So tire cavity noise becomes more serious. In this paper, a designed material for reducing tire cavity noise is proposed. On the surface inside tire, this material is attached at one position using double-tape. This material disperses the pressure variations inside the tire. So a spindle forces at wheel center are reduced. And tire cavity noise at vehicle interior is also reduced. Durability is verified by tire only test and vehicle test. Noise performance also compared with peak levels after attaching this material.

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