Material, Sensors, Actuators and Fabrication Lesson 1

Introduction

Hightlight: sensor and actuator, material is because of that Shape memory alloy, electrical material

Robotic material: material engineering cares about many aspects of the material, while science cares maybe only one aspect of the material, like superconductivity

Convention and Advanced Robotic Materials

Conventional Matrial: most of the material foucs only on one job, and leading to one aspect of the material. e.g. Arm, leg, body: mechanical properties are important

Advanced Robotic Materials: multifunctional, tightly integrated e.g. maybe the material expand to push, some material can change shape on change of electric field (mechanical field and electrical field. more: thermal field, chemical field)

Robotic Matrial can mean putting up a lot of materials together to make a system. (page 9)

The rest

Basic Knowledge of Materials Science and Engineering

important: Crsytal, Phase Diagram

Atomic structure:

page 29

bonding:

• ionic (NaCl)
• covalent (H2O)
• metallic (Mg)
• secondary bond (Polymer, Van der Waals?)

page 30

Some properties of material is determined by the chemical bond: - elastic modulus, (atomic force) - thermal expansion coefficient, (atomic force)

So, unless the nature of the bond is changed, the properties will not change.

page 31

Crystal structure of Solids

General: Unit cell

• Cubic
• Tetragonal
• Hexagonal

more on page 32, 33

page 34: complicated structure

vacancy can effect the properties of the material

atom of Ti can shift under the influence of electric field; and can even lead to deformation, but the movement typically small and limited, but can be more precise than using a motor.

page 36

14 basic cell -> 32 crystallographic point groups

page 37

crystal structure is ideal, but in reality, there are defects. (can be useful)

page 42

left: normal process for ceramic right: tape casting

all ceramic need sinterring, because the ceramic is made of powder, and the powder is not bonded together, so need to be sinterring to bond them together.

page 44 Solid solution: mixing two solid together, and they are mixed at atomic level, to form a new material.

page 45 Mechanical properties is always important even for materail that is not used for mechanical purpose. Such as some material used in sea water. And many failure of material is due to mechanical failure.

page 50 If several material have very different thermal expansion coefficient, there will be large residual stress when they are bonded together.

page 53 Smart material is also needed with a processor to control it. But maybe itself can be sensor and actuator.