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Metamaterials
Metamaterials

メタマテリアル(Metamaterials)とは
Metamaterials

メタマテリアルとは、自然界には見られない機能を持つように人工的に設計されたモノを指します。具体的にはある材料に対して幾何形状を設計、または様々な材料の配置を適切にコントロールすることで、材料単体では実現できなかったマクロな物性を実現したモノをメタマテリアルと呼びます。



例えばこの動画にあるメタマテリアルはゴムやエラストマーなどの一般的な柔軟な材料に穴をあけたシンプルな幾何構造ですが、特異な変形を生み出しています。一般的な柔軟材料は体積を保存するため圧縮方向と垂直な方向に膨らみます。一方で動画のメタマテリアルは圧縮方向に垂直な方向は膨らまずに縮み、全体として体積が拡大縮小する通常ではありえない変形が生まれています。こうした構造は負のポアソン比を持つメタマテリアル(Auxetic)と呼ばれており、衝撃吸収性や追従性の高い変形を生み出します。





力学的メタマテリアル(Mechanical Metamaterials)はAxeticのような衝撃吸収だけではなく、変形を適切に制御することで振動吸収・振動伝達・音響制御など幅広い領域の物理現象を制御するポテンシャルを持つ研究領域です。また、光学特性、電磁特性などを制御するメタマテリアルの研究も近年盛んに行われています。

この構造はエラストマーに穴を開けただけで製造できることからもわかるようにメタマテリアルは3Dプリンタなどの先進的な製造方法だけではなく、射出成形やプレス加工など従来の製造手法であっても十分にさまざまな物理現象を制御することができます。

Metamaterials in a broad sense refer to objects that have been artificially designed to have functions not found in nature. By assigning a geometric shape to a material or by appropriately controlling the arrangement of various materials, macroscopic physical properties that could not be realized with a single material can be realized.

For example, as shown in the figure below, the entire shape created by space-filling a metal with a specific geometric structure (right side of the figure) is considered to be a "material" (metamaterial), and considering its Young's modulus (material rigidity) and Poisson's ratio (deformation characteristics of the material) means "understanding the structure as a metamaterial.

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The structure is called an Octet Truss, which is lighter and stiffer than many materials in general use today. Octet Trusses are called Mechanical Metamaterials, which means that their mechanical properties, such as elasticity, plasticity and deformation properties, are artificially controlled. Octet Truss is one of the mechanical metamaterials, in which mechanical properties such as elasticity, plasticity and deformation are artificially controlled.

(*However, there are now reports of metamaterial structures that are lighter and stiffer than Octet Truss.)

Mechanical metamaterials are a research field that has the potential to control a wide range of physical phenomena such as vibration absorption, vibration transmission, shock absorption, and acoustic control by appropriately controlling deformation, in addition to achieving both rigidity and lightness as in the case of Octet Truss. This research field has the potential to control a wide range of physical phenomena such as vibration absorption, vibration transmission, shock absorption, and acoustic control by appropriately controlling deformation. In addition, metamaterials that control optical and electromagnetic properties have been actively studied in recent years.

Metamaterials are known to produce various physical properties not only in space-filling structures such as Octet Truss, but also in two-dimensional structures such as honeycomb. Therefore, metamaterials can control various physical phenomena not only by advanced manufacturing methods such as 3D printers but also by conventional manufacturing methods such as injection molding and pressing.

Compliant Mechanisms
Compliant Mechanisms

コンプライアントメカニズム (Compliant Mechanisms)とは
Compliant Mechanisms

弾性変形を伴い、力や変形を伝える機構のことをコンプライアントメカニズムと呼びます。例えば、バネやペーパークリップ、スナップフィットなどもコンプライアントメカニズムの一形態です。

コンプライアントメカニズムには少なくとも次の5つの利点があります。

A mechanism that involves elastic deformation and transmits force or deformation is called a compliant mechanism. For example, a spring, paper clip, or snap fit is a form of compliant mechanism.

Compliant mechanisms have at least the following five advantages

  1. 1. 少ない部品点数

    1. Fewer Parts

    コンプライアントメカニズムの多くは一体構造で狙った動きを生み出すことができるため、従来ではネジやボルトで組み立てて生み出していたヒンジ等の稼働部位の組立てを大幅に減らすことができます。


    Many of the compliant mechanisms have a one-piece structure that can produce the desired movement, which greatly reduces the need to assemble hinges and other moving parts that are conventionally assembled with screws and bolts.

  2. 2. 精密挙動

    2. Precision Mechanics

    コンプライアントメカニズムは一体構造で変形を生み出すことができるため、従来の稼働部位に発生する部品間の”あそび”がなくなり、精密な挙動を実現できます。

    Since the compliant mechanism can generate deformation in a single structure, it eliminates the "looseness" that occurs between parts in conventional operating areas, and allows for precise behavior.

  3. 3. 微細挙動

    3. Microscopic Mechanics

    精密な挙動を一体構造で制御することができるため、コンプライアントメカニズムは、微細なセンサ・アクチュエータなどのMEMS(Microelectromechanical Systems) 領域 で応用されています。更に、コンプライアントメカニズムによって動きを伴う様々な従来部材を小型化することができます。

    Because of the ability to control precise behavior in a single structure, compliant mechanisms are being applied in the field of microelectromechanical systems (MEMS), such as microscopic sensors and actuators. Furthermore, compliant mechanisms can reduce the size of various conventional components that involve motion.

  4. 4. オイルレスな稼働部材

    4. Oil-free Operating Components

    一体構造によって動きを制御するコンプライアントメカニズムは、稼働部の部品間摩擦を低減するための潤滑油を必要としません。したがって、潤滑油周りのメンテナンスが不要となると共に、無重力・超高低温下などの極環境下でも安定して稼働する機構として利用することができます。

    The compliant mechanism, whose movement is controlled by an integrated structure, does not require lubricating oil to reduce the friction between the parts of the operating part. Therefore, maintenance around lubricating oil is not necessary, and the mechanism can be used to operate stably even in extreme environments such as zero gravity and ultra high and low temperatures.

  5. 5. 振動制御

    5. Vibration Control

    コンプライアントメカニズムによって適切に弾性・変形を制御すれば、バネやゴムなどの付加的な部材を用いることなく特定の振動を遮断することができます。また特定の振動周波数を強めて振動を
    効率よく伝達することもできます。


    If the elasticity and deformation are properly controlled by the compliant mechanism, specific vibrations can be blocked without the use of additional components such as springs or rubber. It is also possible to transmit vibration efficiently by intensifying a specific vibration frequency.
    It is also possible to transmit vibrations efficiently by strengthening specific vibration frequencies.


DFM
DFM

DFM(Direct Functional Modeling)
DFM(Direct Functional Modeling)

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