INTRODUCTION TO SMART MATERIALS RAKESH CHANDRA B CB.EN.P2MFG12008

SMART MATERIALS Sense and react to environmental conditions or stimuli such as those from mechanical, thermal,chemical,electrical,magnetic or other sources In general, smart materials come in three distinct flavors: (a) Passively smart materials that respond directly and uniformly to stimuli without any signal processing. (b)Actively smart materials that can, with the help of a remote controller, sense a signal, analyze it, and then “decide” to respond in a particular way. (c)Finally, the more powerful and autonomous intelligent materials that carry internal, fully integrated controllers, sensors, and actuators

HISTORY Gold- Cadmium in1932 Copper-Zinc in1938 BEEHLER , Ni-Ti at the Naval Ordinance Laboratory – Nitinol (1962) After the discovery of Nitinol, a number of other system with the ‘shape memory effect’ was found.

DIFFERENT TYPES OF SMART MATERIALS Piezoelectric materials Magneto restrictors Shape Memory Alloys (SMAs) Electro rheological Fluids Thermo responsive materials pH-sensitive materials Electro chromic materials

Piezoelectric materials: produce an electrical field when subject to a mechanical strain Magneto restrictors: respond to magnetic field. They produce a magnetic field when strained

Shape Memory Alloys (SMAs): materials can convert thermal energy directly into mechanical work

Electro rheological Fluids: changes in rheological properties such as viscosity, plasticity, and elasticity.

pH-sensitive materials : These are indicators that change colors as a function of Ph Electro chromic materials :when a voltage is applied across it the optical properties are changed.

Transformation Mechanism of Smart Material existence austenite martensite (high temp phase) (low temp phase) twinned detwinned

Different phases of smart materials Austenite High temperature phase Cubic Crystal Structure Martensite Low temperature phase Monoclinic Crystal Structure Detwinned Martensite Twinned Martensite

Transformation Mechanism When temp changes transformation between two phases occur due to this transformation, SM have many special properties, such as shape memory effect and super elasticity

shape memory effect

super elasticity

USES & APPLICATIONS OF SMART MATERIALS Vibration reduction in sporting goods Noise reduction in vehicles military applications Medical Applications

On the left, the drink is too warm. Once cooled, a stripe appears (right) indicating that the drink is properly chilled. Thermo chromic pigments

Thermo colour Sheet This is a self adhesive sheet whose colour changes according to the temperature. Used for thermometers, heat warning patches

Thermo colour Sheet This is a self adhesive sheet whose colour changes according to the temperature. Used for thermometers, heat warning patches

Thermo colour Sheet This is a self adhesive sheet whose colour changes according to the temperature. Used for thermometers, heat warning patches Sheet changes colour according to temp

SMAs are widely use in medical applications. This is a medical implant which expands when warmed to body temperature, to widen a restricted blood vessel.

The future…… The emerging industrial applications are: Active Vibration Control (AVC) Active Noise Control (ANC) Active Shape Control (ASC) Active Health Monitoring (AHM)

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