Introduction to Smart Materials for Mechatronics.pptx

This Document has a details about the Smart materials

1. Smart Materials for Mechatronics (21MTRC0) Introduction to Smart Materials

2. What are Smart Materials? Smart Materials are those which possess ability to change their physical properties in a specific fashion by external stimuli or their environment. Physical properties could be shape, viscosity, stiffness, color, dimension, etc. Stimuli could be: •       Stress/Strain •       Pressure •       Water •       Wind •       Temperature •       Electric current •       Magnetic fields •       Nuclear radiation •       Light •       pH •       Moisture

3. Types of Smart materials 1. Active Smart Materials (Sensors and Actuators) It can change their properties in response to external stimuli such as temperature, pressure, electric or magnetic fields, light, or chemical environments. They can perform work or generate forces, making them useful for actuators, sensors, and other responsive systems. Examples: Piezoelectric Materials, Shape Memory Alloys, Electroactive Polymers, ER and MR Fluids 2. Passive smart materials (Sensors) It have intrinsic properties that allow them to respond to environmental changes without the need for external control. They do not actively change their properties but can adapt to changes in their environment in a predictable manner. Examples: Self-Healing Polymers, Hydrogels, Thermal Insulators, Phase Change Materials

4. Classification of smart materials Input Smart Material Output Stress Piezoelectric Material Electric charge Electric Field Mechanical Strain Temperature change Pyroelectric Material Electric charge Heat Shape Memory Alloy Original Memorized Shape Magnetic Field Ferromagnetic Shape Memory Alloy Original Memorized Shape Electric Field Electro-rheological Fluid Change in Viscosity Magnetic Field Magneto-rheological Fluid Change in Viscosity Magnetic Field Magnetostrictive Material Mechanical Strain Electric Field Electrostrictive Materials Mechanical Strain Temperatute Thermochromic Material color Light Photochromic Material color

5. What are piezoelectric materials? Piezoelectric materials are materials that have the ability to generate internal electrical charge from applied mechanical stress. ​ The term ​ piezo ​ is Greek for "push.“ Applications

6. Barium titanate (BaTiO 3 ). The first piezoelectric ceramic discovered. Lead titanate (PbTiO 3 ) Lead zirconate titanate (PZT). Currently the most commonly used Potassium niobate (KNbO 3 ) Lithium niobate (LiNbO 3 ) Lithium tantalate (LiTaO 3 ) Sodium tungstate (Na 2 WO 4 ) Synthetic Piezoelectric Materials

7. What are Shape Memory Materials? Shape-memory materials have the potential to restore their original shape after a major and seemingly plastic deformation when a certain stimulus is applied. The nickel-titanium ( NiTi / Nitinol ) alloy developed by William J. Buehler at the Naval Ordinance Laboratory in the early 1960 s is a type of shape memory alloy with 50 % nickel and 50 % titanium content

8. Shape Memory EFFECT High-temperature phase Parent phase Body centered cubic crystal structure Austenite Phase  Low-temperature phase lower symmetry, Tetragonal, orthorhombic, or monoclinic crystal structure. Shape-memory effect Martensite  Phase

9. Shape Memory EFFECT

10. One way shape-memory effect Two way shape-memory effect The material returns to its original shape upon heating. The material can remember two shapes: one at high temperature (austenite) and one at low temperature ( martensite ). Types of Shape Memory EFFECT

11. Psudoelasticity vs Shape memory effect Pseudo-elasticity or superelasticity refers to the material's ability to recover its original shape after a mechanical load has induced large deformations. Shape memory effect describes the ability of such a material to be plastically deformed below its transformation temperature, and recover its original shape once the temperature is increased.

12. Phase-transformation There are four critical phase-transformation temperatures: Ms , Mf , As and Af Ms – Martensite start Mf - Martensite finish As – Austenite start Af - Austenite finish

13. magnetic shape memory alloys (MSMA) Magnetic shape memory alloys (MSMA), or ferromagnetic shape memory alloys (FSMA), are particular shape memory alloys that can be stimulated by an external magnetic field too, out of the thermal shape memory effect ( Ullakko , 1996). Martensitic Transformation: They undergo a reversible phase transformation between martensite (low symmetry phase) and austenite (high symmetry phase) when exposed to a magnetic field. A laboratory-based actuator with NiMnGa

14. Shape Memory Actuators Aircraft Structures Robotics Biomedical-Stents The wires in the picture are used to replace the actuator. Electric pulses sent through the wires allow for precise movement of the wings, as would be needed in an aircraft. This reduces the need for maintenance, weighs less, and is less costly.

15. Additive Manufacturing

16. Spring tyres

17. Hubble Arms

18. Problems With SMAs Fatigue from cycling Causes deformations and grain boundaries Begin to slip along planes/boundaries Overstress A load above 8% strain could cause the SMA to completely lose its original austenite shape Difficulty with computer programming More expensive to manufacture than steel and aluminum Relatively new

19. Magnetostriction is defined as the property of some magnetic materials that causes them to change their shape or dimensions when they are magnetized by an external magnetic field . The change in size or length of a material due to magnetostriction depends on the strength and direction of the applied magnetic field , as well as the magnetic anisotropy and crystal structure of the material. Magnetostrictive MaTerials The phenomenon was first noted by James Joule in 1842, establishing a foundational understanding of how magnetic fields affect materials. Eg : Terfenol -D

20. Actuator - Joule Effect Sensor – Villari Effect “energy harvesting” Magnetostriction converts electrical energy into mechanical energy and vice versa Anisotropic property – crystal orientation dependence Change in shape is completely elastic - no fatigue Magnetostriction is a reversible effect Magnetic Field Mechanical S train Magnetostriction 21

21. Strain vs Magnetic Field of Magnetostrictive Materials Magnetostriction refers to the phenomenon in which the dimensions of a material shift when its magnetisation changes. cobalt, iron – 50 ppm Magnetostrictives were used in SONAR applications during world war - II Strain vs Magnetic Field of Magnetostrictive Materials 22 Clark et al. 2000

22. When an external magnetic field is applied to a magnetic material, it exerts a torque on the domains, causing them to rotate and align with the field direction. This process involves the movement of domain walls (the boundaries between domains with different magnetization directions) and the deformation of the crystal lattice (the arrangement of atoms in the material). As a result, the material changes its shape or dimensions according to its magnetostrictive strain (the fractional change in length or volume due to magnetostriction ) Mechanism

23. Magnetostrictive Materials Materials Magnetostriction Curie Temperature Fe 20 ppm ~ 770°C Ni 60 ppm ~ 360 °C Co 30 ppm ~ 1120 °C Fe-Al Alloy ( Alfer ) 100 ppm ~ 800 °C Fe-Ni Alloy ( Permalloy ) 1 ppm - Co-Ni Alloy 20 ppm ~ 950 °C Fe-Co Alloy 30 ppm ~ 980 °C Co-Fe-Vanadium Alloy ( Permendur ) 5 ppm ~ 1400 °C Ferrites 10 ppm > 400 °C Rare Earths: La, Ce, Nd 1000 ppm < 300 °C Terfenol -D 2000 ppm ~ 380 °C Galfenol : Fe 81 Ga 19 250 ppm ~ 700 °C

24. Terfenol-D is an intermetallic compound Terbium Dysprosium Iron T b Dy Fe Nominal composition is Tb 0.3 Dy 0.7 Fe 1.92 Tb:Dy ratio tailored to fit application Tb generates the majority of the magnetostriction Dy reduces magnetic anisotropy Fe stabilizes magnetic ordering to ambient temperatures (raises T c ) Terfenol - D 25 Teter et al. 1987

25. Low Magnetostriction Structural (strong) High Magnetostriction Brittle Ni: 50 ppm Terfenol-D: 1000 ppm Fe-Ga: 60 – 250 pp m Galfenol (Fe-Ga) 26 Wang et al. 2013

26. The magnetostrictive strain can be measured by various methods, such as optical interferometry, strain gauges , piezoelectric transducers , or resonant techniques. The most common parameter used to characterize magnetostriction is the magnetostriction coefficient (also called Joule’s coefficient), which is defined as: where ΔL is the change in length of material when magnetized from zero to saturation, and L is its initial length.   magnetostrictive strain

27. magnetostrictive strain depends on several factors The magnitude and direction of the applied magnetic field The saturation magnetization (the maximum possible magnetization) of the material The magnetic anisotropy (the preference for certain magnetization directions) of the material - how direction affects the magnetic property of a material The magnetoelastic coupling (the interaction between magnetization and elastic strain) of the material The temperature and stress state of the material Crystallographic directions

28. Joule effect and Villari effect Joule effect Villari effect The Joule effect, also known as the direct magnetostrictive effect, is when a ferromagnetic material changes size in response to an external magnetic field.  The Villari effect is the reverse, where a change in the length of a ferromagnetic material induces a magnetic field.  Villari effect Joule effect

29. Electrostrictive materials Electrostriction is a property of all dielectric materials, and is caused by the presence of randomly-aligned electrical domains within the material. When an electric field is applied to the dielectric, the opposite sides of the domains become differently charged and attract each other, reducing material thickness in the direction of the applied field (and increasing thickness in the orthogonal directions due to  Poisson's ratio ). The resulting  strain  (ratio of deformation to the original dimension) is proportional to the square of the  polarization . Reversal of the electric field does not reverse the direction of the deformation. More formally, the electrostriction coefficient is a fourth order tensor ( Q ijlk ), relating second order strain ( x ij ) and first order polarization tensors ( P k ,  P l ). It should be noted that the related  piezoelectric effect  occurs only in a particular class of dielectrics. Electrostriction is a quadratic effect, unlike piezoelecticity , which is a linear effect. In addition, unlike piezoelectricity, electrostriction cannot be reversed: deformation will not induce an electric field.

30. Materials The most commonly used are: Lead magnesium niobate (PMN) Lead magnesium niobate -lead titanate (PMN-PT) Lead lanthanum zirconate titanate (PLZT)