The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform

Shih-po Lin - One of the best experts on this subject based on the ideXlab platform.

  • Factors affecting the formation of fingering in water‐assisted injection‐molded thermoplastics
    Advances in Polymer Technology, 2006
    Co-Authors: Shih-jung Liu, Shih-po Lin
    Abstract:

    Water-assisted injection-molding technology has received extensive attention in recent years, due to the lightweight of plastic parts, relatively low-resin cost per part, faster cycle time, and flexibility in the design and manufacture. However, there are still some unsolved problems that confound the overall success of this technology. One of these is the water “fingering” phenomenon, in which the water bubbles penetrate outside designed water channels and form finger-shape branches. This study has investigated the effects of various processing parameters on the formation of fingering in water-assisted injection-molded thermoplastic parts. Both amorphous and semicrystalline polymers were used to mold the parts. The influence of water channel Geometry, including aspect ratio and Fillet Geometry, on the fingering was also investigated. It was found that water-assisted injection-molded amorphous materials gave less fingering, while molded semicrystalline parts gave more fingering when compared to those molded by gas-assisted injection molding. For the water channels used in this study, the channels with a rib on the top produced parts with the least water fingering. Water fingering in molded parts decreases with the height-to-thickness ratio of the channels. The water pressure, water injection delay time and short-shot size were found to be the principal parameters affecting the formation of water fingering. In addition, a numerical simulation based on the transient heat conduction model was also carried out to help better explain the mechanism for the formation of fingering in water-assisted injection-molded thermoplastics. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 98–108, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20062

  • Study of ‘fingering’ in water assisted injection molded composites
    Composites Part A: Applied Science and Manufacturing, 2005
    Co-Authors: Shih-jung Liu, Shih-po Lin
    Abstract:

    Abstract Thin, plate-shaped parts of composite materials are usually reinforced with structural ribs. These ribs also serve as water channels in water-assisted injection molding technology. One of the problems encountered in water assisted injection molded composite parts is the ‘water fingering’ phenomenon, in which the water bubbles penetrate outside designed water channels and form finger-shape branches. Severe fingerings can lead to significant reductions in part stiffness. This study investigated the fingering phenomenon in water assisted injection molded composites. Experiments were carried out on a water-assisted injection molding system developed earlier in our lab. The materials used were short glass–fiber filled polypropylene composites. A plate cavity with a fish-bone water-channel layout was used for all experiments. The effects of various processing parameters on the fingering were studied. It was found that the water pressure, water injection delay time and melt short shot size were the principal parameters affecting the formation of water fingerings. In addition, the influence of water channel Geometry, including aspect ratio and Fillet Geometry on the fingering were also investigated. The goal of this study is to gain a better understanding of the formation of water fingerings, so that steps can be taken to ensure that the fingering is minimized. This provides significant advantages in terms of improved part quality.

Shih-jung Liu - One of the best experts on this subject based on the ideXlab platform.

  • Factors affecting the formation of fingering in water‐assisted injection‐molded thermoplastics
    Advances in Polymer Technology, 2006
    Co-Authors: Shih-jung Liu, Shih-po Lin
    Abstract:

    Water-assisted injection-molding technology has received extensive attention in recent years, due to the lightweight of plastic parts, relatively low-resin cost per part, faster cycle time, and flexibility in the design and manufacture. However, there are still some unsolved problems that confound the overall success of this technology. One of these is the water “fingering” phenomenon, in which the water bubbles penetrate outside designed water channels and form finger-shape branches. This study has investigated the effects of various processing parameters on the formation of fingering in water-assisted injection-molded thermoplastic parts. Both amorphous and semicrystalline polymers were used to mold the parts. The influence of water channel Geometry, including aspect ratio and Fillet Geometry, on the fingering was also investigated. It was found that water-assisted injection-molded amorphous materials gave less fingering, while molded semicrystalline parts gave more fingering when compared to those molded by gas-assisted injection molding. For the water channels used in this study, the channels with a rib on the top produced parts with the least water fingering. Water fingering in molded parts decreases with the height-to-thickness ratio of the channels. The water pressure, water injection delay time and short-shot size were found to be the principal parameters affecting the formation of water fingering. In addition, a numerical simulation based on the transient heat conduction model was also carried out to help better explain the mechanism for the formation of fingering in water-assisted injection-molded thermoplastics. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 98–108, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20062

  • Study of ‘fingering’ in water assisted injection molded composites
    Composites Part A: Applied Science and Manufacturing, 2005
    Co-Authors: Shih-jung Liu, Shih-po Lin
    Abstract:

    Abstract Thin, plate-shaped parts of composite materials are usually reinforced with structural ribs. These ribs also serve as water channels in water-assisted injection molding technology. One of the problems encountered in water assisted injection molded composite parts is the ‘water fingering’ phenomenon, in which the water bubbles penetrate outside designed water channels and form finger-shape branches. Severe fingerings can lead to significant reductions in part stiffness. This study investigated the fingering phenomenon in water assisted injection molded composites. Experiments were carried out on a water-assisted injection molding system developed earlier in our lab. The materials used were short glass–fiber filled polypropylene composites. A plate cavity with a fish-bone water-channel layout was used for all experiments. The effects of various processing parameters on the fingering were studied. It was found that the water pressure, water injection delay time and melt short shot size were the principal parameters affecting the formation of water fingerings. In addition, the influence of water channel Geometry, including aspect ratio and Fillet Geometry on the fingering were also investigated. The goal of this study is to gain a better understanding of the formation of water fingerings, so that steps can be taken to ensure that the fingering is minimized. This provides significant advantages in terms of improved part quality.

Richard J Goldstein - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Blade Leading Edge Geometry on Turbine Endwall Heat (Mass) Transfer
    Journal of Turbomachinery, 2005
    Co-Authors: S. Han, Richard J Goldstein
    Abstract:

    The secondary flows, including passage and other vortices in a turbine cascade, cause significant aerodynamic losses and thermal gradients. Leading edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading edge modified blade has not been investigated thoroughly. Since a Fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a Fillet Geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having a modified leading edge by adding a Fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the Fillets. Apparently the corner vortices are intensified with the leading edge modified blade.

  • Influence of blade leading edge Geometry on turbine endwall heat(mass) transfer
    Volume 3: Turbo Expo 2005 Parts A and B, 2005
    Co-Authors: S. Han, Richard J Goldstein
    Abstract:

    The secondary flows, including passage and other vortices in a turbine cascade cause significant aerodynamic losses and thermal gradients. Leading-edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading-edge modified blade has not been investigated thoroughly. Since a Fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a Fillet Geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having modified leading-edge by adding a Fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the Fillets. Apparently the corner vortices are intensified with the leading-edge modified blade.Copyright © 2005 by ASME

S. Han - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Blade Leading Edge Geometry on Turbine Endwall Heat (Mass) Transfer
    Journal of Turbomachinery, 2005
    Co-Authors: S. Han, Richard J Goldstein
    Abstract:

    The secondary flows, including passage and other vortices in a turbine cascade, cause significant aerodynamic losses and thermal gradients. Leading edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading edge modified blade has not been investigated thoroughly. Since a Fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a Fillet Geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having a modified leading edge by adding a Fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the Fillets. Apparently the corner vortices are intensified with the leading edge modified blade.

  • Influence of blade leading edge Geometry on turbine endwall heat(mass) transfer
    Volume 3: Turbo Expo 2005 Parts A and B, 2005
    Co-Authors: S. Han, Richard J Goldstein
    Abstract:

    The secondary flows, including passage and other vortices in a turbine cascade cause significant aerodynamic losses and thermal gradients. Leading-edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading-edge modified blade has not been investigated thoroughly. Since a Fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a Fillet Geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having modified leading-edge by adding a Fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the Fillets. Apparently the corner vortices are intensified with the leading-edge modified blade.Copyright © 2005 by ASME

Chung-biau Tsay - One of the best experts on this subject based on the ideXlab platform.

  • Tooth profile design for the manufacture of helical gear sets with small numbers of teeth
    International Journal of Machine Tools & Manufacture, 2005
    Co-Authors: Chien-fa Chen, Chung-biau Tsay
    Abstract:

    Based on gear theory and generating mechanism, this investigation presents a complete mathematical model of a helical gear set with small number of teeth. The unavoidable tooth-profile undercutting of the gears with small number of teeth is examined by using the developed mathematical model and the conventional method of tooth-profile shifting. Furthermore, an alternative method for lessening the tooth-profile undercutting is also presented by considering a modification of the basic Fillet Geometry using a modified rack cutter. A third method, combining the aforementioned two methods for the design of helical gears with small number of teeth is also proposed to yield a gear set without tooth undercutting. The mating gear with profile shifting is generated using the pinion as a shaper. The tip Fillet and root Fillet are modified and a clearance between the pinion and the mating gear is also included in the design. Analysis results indicate that the change of distance between the centers of gear set depends only on gear shifting. Moreover, computer graphs are demonstrated the profile-shifted and the proposed modified gear tooth profiles.