The Experts below are selected from a list of 11898 Experts worldwide ranked by ideXlab platform

Nicola Pugno - One of the best experts on this subject based on the ideXlab platform.

  • Stag Beetle Elytra: Localized Shape Retention and Puncture/Wear Resistance
    Insects, 2019
    Co-Authors: Lakshminath Kundanati, Roberto Guarino, Nicola Pugno
    Abstract:

    Beetles are by far one of the most successful groups of insects, with large diversity in terms of number of species. A part of this success is attributed to their elytra, which provide various functions such as protection to their bodies from mechanical forces. In this study, stag beetle (Lucanus cervus) elytra were first examined for their overall flexural properties and were observed to have a localized Shape-retaining snap-through mechanism, which may play a possible role in partly absorbing impact energy, e.g., during battles and falls from heights. The snap-through mechanism was validated using theoretical calculations and also finite element simulations. Elytra were also characterized to examine their puncture and wear resistance. Our results show that elytra have a puncture resistance that is much higher than that of mandible bites. The measured values of modulus and hardness of elytra exocuticle were 10.3 ± 0.8 GPa and 0.7 ± 0.1 GPa, respectively. Using the hardness-to-modulus ratio as an indicator of wear resistance, the estimated value was observed to be in the range of wear-resistant biological material such as blood worms (Glyrcera dibranchiata). Thus, our study demonstrates different mechanical properties of the stag beetle elytra, which can be explored to design Shape-retaining bio-inspired composites with enhanced puncture and wear resistance.

  • stag beetle elytra localized Shape Retention and puncture wear resistance
    Insects, 2019
    Co-Authors: Lakshminath Kundanati, Roberto Guarino, Nicola Pugno
    Abstract:

    Beetles are by far one of the most successful groups of insects, with large diversity in terms of number of species. A part of this success is attributed to their elytra, which provide various functions such as protection to their bodies from mechanical forces. In this study, stag beetle (Lucanus cervus) elytra were first examined for their overall flexural properties and were observed to have a localized Shape-retaining snap-through mechanism, which may play a possible role in partly absorbing impact energy, e.g., during battles and falls from heights. The snap-through mechanism was validated using theoretical calculations and also finite element simulations. Elytra were also characterized to examine their puncture and wear resistance. Our results show that elytra have a puncture resistance that is much higher than that of mandible bites. The measured values of modulus and hardness of elytra exocuticle were 10.3 ± 0.8 GPa and 0.7 ± 0.1 GPa, respectively. Using the hardness-to-modulus ratio as an indicator of wear resistance, the estimated value was observed to be in the range of wear-resistant biological material such as blood worms (Glyrcera dibranchiata). Thus, our study demonstrates different mechanical properties of the stag beetle elytra, which can be explored to design Shape-retaining bio-inspired composites with enhanced puncture and wear resistance.

Sung-hoon Ahn - One of the best experts on this subject based on the ideXlab platform.

  • Hybrid composite actuator with Shape Retention capability for morphing flap of unmanned aerial vehicle (UAV)
    Composite Structures, 2020
    Co-Authors: Nam-geuk Kim, Minwoo Han, Anna Iakovleva, Hyungbin Park, Won-shik Chu, Sung-hoon Ahn
    Abstract:

    Abstract A morphing flap is for changing the Shape of wings continuously without any additional mechanical parts, which can reduce turbulence, aerodynamic drag, vibration, and noise versus the discontinuous geometry of ‘conventional’ flaps. Especially, smart materials based morphing technology can achieve various deformations without complex mechanical components, such as motors and joints. These characteristics are advantageous to reduce the operating cost of the aircraft through improvement of aerodynamic performance and weight saving. In this study, we designed a hybrid composite actuator capable of Shape-Retention, integrated with a Shape memory polymer (SMP) scaffold and a Shape memory alloy (SMA) wire. The hybrid composite actuator composed of SMP and SMA can maintain a deformed state without additional current to heat the SMA by using Shape-memory effects of SMP. The measured maximum deformation angle of the actuator was 102° and the maintained angle was 70°. Then, the aerodynamic performance of the morphing flap was evaluated in wind-tunnel experiments. The morphing flap generated additional lift force during actuation and the lift-to-drag ratio of the morphing flap was higher than that of a conventional flap; the maximum difference was 81% at 10° of the angle of attack.

  • Smart soft composite actuator with Shape Retention capability using embedded fusible alloy structures
    Composites Part B: Engineering, 2015
    Co-Authors: Wei Wang, Hugo Rodrigue, Sung-hoon Ahn
    Abstract:

    This work presents a new kind of Shape memory alloy (SMA) based composite actuators that can retain its Shape in multiple configurations without continuous energy consumption by changing locally between a high-stiffness and a low-stiffness state. This was accomplished by embedding fusible alloy (FA) material, Ni-chrome (Ni-Cr) wires and SMA wires in a smart soft composite (SSC) structure. The soft morphing capability of SMA-based SSC structures allows the actuator to produce a smooth continuous deformation. The stiffness variation of the actuator was accomplished by melting the embedded FA structures using Ni-Cr wires embedded in the FA structure. First, the design and manufacturing method of the actuator are described. Then, the stiffness of the structure in the low and high-stiffness states of the actuator were measured for different applied currents and heating durations of the FA structure and results show that the highest stiffness of the actuator is more than eight times that of its lowest stiffness. The different Shape Retention capability of the actuator were tested using actuators with one or two segments and these were compared with a numerical model.

  • woven type smart soft composite beam with in plane Shape Retention
    Smart Materials and Structures, 2013
    Co-Authors: Minwoo Han, Gilyong Lee, Sung-hoon Ahn
    Abstract:

    Shape memory alloy (SMA) wire embedded composites (SMAECs) are widely used as morphing structures in small-size and high-output systems. However, conventional SMAECs cannot keep deformed Shapes without additional energy. In this paper, a new kind of smart structure named the woven type smart soft composite (SSC) beam is introduced, which is not only capable of morphing, but also maintaining its deformed Shape without additional energy. The woven type SSC beam consists of two parts: woven wires and matrix. The selected woven wires are nitinol (Ni–Ti) SMA wires and glass fibers, while the matrix part is polydimethylsiloxane (PDMS). In order to evaluate the performance of the woven type SSC beam in areas such as in-plane deformation, blocking force and repeatability, a beam-Shape specimen is prepared of size 100 mm (length) × 8 mm (width) ×3 mm (thickness). The fabricated SSC beam achieved 21 mm deformation and 16 mm Shape Retention. Blocking force was measured using a dynamometer, and was about 60 mN. In the repeatability test, it recovered almost the same position when its cooling time was 90 s more. Consequently, the woven type SSC beam can be applied to bio-mimicking, soft morphing actuators, consuming less energy than traditional SMAECs.

Lakshminath Kundanati - One of the best experts on this subject based on the ideXlab platform.

  • Stag Beetle Elytra: Localized Shape Retention and Puncture/Wear Resistance
    Insects, 2019
    Co-Authors: Lakshminath Kundanati, Roberto Guarino, Nicola Pugno
    Abstract:

    Beetles are by far one of the most successful groups of insects, with large diversity in terms of number of species. A part of this success is attributed to their elytra, which provide various functions such as protection to their bodies from mechanical forces. In this study, stag beetle (Lucanus cervus) elytra were first examined for their overall flexural properties and were observed to have a localized Shape-retaining snap-through mechanism, which may play a possible role in partly absorbing impact energy, e.g., during battles and falls from heights. The snap-through mechanism was validated using theoretical calculations and also finite element simulations. Elytra were also characterized to examine their puncture and wear resistance. Our results show that elytra have a puncture resistance that is much higher than that of mandible bites. The measured values of modulus and hardness of elytra exocuticle were 10.3 ± 0.8 GPa and 0.7 ± 0.1 GPa, respectively. Using the hardness-to-modulus ratio as an indicator of wear resistance, the estimated value was observed to be in the range of wear-resistant biological material such as blood worms (Glyrcera dibranchiata). Thus, our study demonstrates different mechanical properties of the stag beetle elytra, which can be explored to design Shape-retaining bio-inspired composites with enhanced puncture and wear resistance.

  • stag beetle elytra localized Shape Retention and puncture wear resistance
    Insects, 2019
    Co-Authors: Lakshminath Kundanati, Roberto Guarino, Nicola Pugno
    Abstract:

    Beetles are by far one of the most successful groups of insects, with large diversity in terms of number of species. A part of this success is attributed to their elytra, which provide various functions such as protection to their bodies from mechanical forces. In this study, stag beetle (Lucanus cervus) elytra were first examined for their overall flexural properties and were observed to have a localized Shape-retaining snap-through mechanism, which may play a possible role in partly absorbing impact energy, e.g., during battles and falls from heights. The snap-through mechanism was validated using theoretical calculations and also finite element simulations. Elytra were also characterized to examine their puncture and wear resistance. Our results show that elytra have a puncture resistance that is much higher than that of mandible bites. The measured values of modulus and hardness of elytra exocuticle were 10.3 ± 0.8 GPa and 0.7 ± 0.1 GPa, respectively. Using the hardness-to-modulus ratio as an indicator of wear resistance, the estimated value was observed to be in the range of wear-resistant biological material such as blood worms (Glyrcera dibranchiata). Thus, our study demonstrates different mechanical properties of the stag beetle elytra, which can be explored to design Shape-retaining bio-inspired composites with enhanced puncture and wear resistance.

Yoshiyuki Nishio - One of the best experts on this subject based on the ideXlab platform.

  • superparamagnetic ipn gels of carrageenan phema excelling in Shape Retention
    Carbohydrate Polymers, 2017
    Co-Authors: Takahiro Tsuru, Kazuki Sugimura, Yoshiyuki Nishio
    Abstract:

    Iron oxide nanoparticles-incorporated carrageenan (CAR)/PHEMA composites of interpenetrating network (IPN) type were successfully prepared by in situ ferrite synthesis in the polymer network. The IPN structure was constructed at CAR/PHEMA compositions of 15/85 and 40/60 (wt/wt) by polymerization and cross-linking of 2-hydroxyethylmethacrylate as an impregnating solvent of CAR gels. As a result of this IPN construction, the composites were firm and showed a good Shape-retentivity in their gelatinous state. SQUID magnetometry and X-ray diffractometry were conducted for evaluation of the magnetic property of the inorganic-hybridized IPN composites. Magnetite particles with 10-30nm sizes were distributed inside the IPNs treated with the repeatable ferrite synthesis; thereby, the hybrids displayed a superparamagnetic character at ambient temperature. Specifically, the 40/60 CAR/PHEMA IPN imparted a practically passable value (10-15emu (g sample)-1) of saturation magnetization. The present IPN system offers a potential for application as a biocompatible magnetic material used in hydro-surroundings.

  • Superparamagnetic IPN gels of carrageenan/PHEMA excelling in Shape Retention.
    Carbohydrate polymers, 2017
    Co-Authors: Takahiro Tsuru, Kazuki Sugimura, Yoshiyuki Nishio
    Abstract:

    Iron oxide nanoparticles-incorporated carrageenan (CAR)/PHEMA composites of interpenetrating network (IPN) type were successfully prepared by in situ ferrite synthesis in the polymer network. The IPN structure was constructed at CAR/PHEMA compositions of 15/85 and 40/60 (wt/wt) by polymerization and cross-linking of 2-hydroxyethylmethacrylate as an impregnating solvent of CAR gels. As a result of this IPN construction, the composites were firm and showed a good Shape-retentivity in their gelatinous state. SQUID magnetometry and X-ray diffractometry were conducted for evaluation of the magnetic property of the inorganic-hybridized IPN composites. Magnetite particles with 10-30nm sizes were distributed inside the IPNs treated with the repeatable ferrite synthesis; thereby, the hybrids displayed a superparamagnetic character at ambient temperature. Specifically, the 40/60 CAR/PHEMA IPN imparted a practically passable value (10-15emu (g sample)-1) of saturation magnetization. The present IPN system offers a potential for application as a biocompatible magnetic material used in hydro-surroundings.

Randall M German - One of the best experts on this subject based on the ideXlab platform.

  • densification and Shape Retention in supersolidus liquid phase sintering
    Acta Materialia, 1999
    Co-Authors: Randall M German
    Abstract:

    Abstract Rapid sintering densification of relatively large prealloyed powders is possible by exceeding the solidus temperature in an approach termed supersolidus liquid phase sintering. This process is often limited by a narrow processing window for attaining densification without distortion. Densification and distortion both reflect viscous flow responses of the solid–liquid mixtures. In the present research, a control microstructure softening parameter ζ , which combines the effects of grain size, liquid volume fraction, and contiguity, is proposed to separate densification and distortion events. This microstructure parameter has two critical values, ζ densif and ζ distort , for densification and Shape loss, respectively. It must be smaller than ζ distort to avoid Shape distortion, while for densification, it must be larger than ζ densif . As ζ densif is smaller than ζ distort , there is window of sintering conditions where densification is achieved without accompanying Shape loss. Understanding this parameter provides a means to design alloys and processing cycles for net Shape, full density components by supersolidus liquid phase sintering.