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Nitinol Innovation - Kellogg's Research Labs (Technical Intro Slide)
- 1. https://www.kelloggsresearchlabs.com/ info@kelloggsresearchlabs.com 1-(855)-583-5353 N I T I N O L K E L L O G G‘ S R E S E A R C H L A B S
- 2. Brief History of Nitinol1 Classifications2 Applications3 Technical Concepts4 O V E R V I E W Providing for You5 Questions and Feedback6
- 3. Brief History of Nitinol
- 4. Discovery of Nitinol’s double state 195 9 By Buehler working with alloys for a ICBM nose cones at Naval Ordinance Labs 196 1Discovery of shape memory effect Again by Naval Ordinance Labs, they realized that low-grade thermal energy can be converted to high-grade mechanical energy 197 4 National Heat Engine Conference Determined more material science knowledge of Nitinol was needed 199 5 Nike releases Flexon eyewear Featuring superelastic Nitinol frames that could take extreme abuse and bounce right back 200 5 Nitinol is ready to hit the world market By this time the material science knowledge was developed enough for widespread commercial use
- 5. Classifications » Shape Memory » Superelastic
- 6. Shape Memory • What is a Shape Memory Alloy? • Material that recovers its shape upon heating • Atomic structures of Nitinol • Martensite: atomic lattice is a “herring bone” shape • Austenite: atomic lattice is cubic • One-way and Two-way shape memory
- 7. Material can two shapes different tra temperature
- 8. Superelastic • What does Superelastic mean? • When stress is removed, the strain is recovered • Superelastic Nitinol exhibits austenite structure • Closer to transition temperature = more superelastic • Due to stress induced martensite • Used in high strain applications
- 9. Applications » Concepts of Application » Current Applications
- 10. Concepts of Application Vibration Dampening » Superelastic nitinol » Dampening properties of silicone » Strength of titanium Actuators » Shape memory nitinol » Linear, rotary, or complex » Single use actuator recover from extreme deformations Temperature Control » Shape memory nitinol » Activates at specific temperature » 1-way or 2-way shape memory Medical Devices » Superelastic or shape memory nitinol » Biocompatibility is exceptional » Numerous other beneficial qualities
- 11. Current Applications Nitinol Antennas for Satellites » Nitinol packs tightly in martensite state » Electricity initiates transformation to austenite state » Extended antenna has magnitudes larger surface area Nitinol Stent Implants » Nitinol is compressed to fit into small arteries » Body temperature initiates transformation » Superelasticity allows for up to 50 million cycles Nitinol Thermo-static valve » Nitinol spring is used as an actuator » Spring expands or contracts to control flow of hot and cold water » Water temperature is thus accurately controlled
- 12. Technical Concepts » Critical Temperatures » Hysteresis » Fatigue » Ternary Alloys
- 13. Critical Temperatures 100% Austenite 100% Martensite Temperature » Martensite Difficult Temperature: 𝑀 𝑑 𝑴 𝒇 𝑴 𝒔 𝑨 𝒔 𝑨 𝒇 𝑴 𝒑 𝑨 𝒑
- 14. Hysteresis 100% Austenite 100% Martensite Temperature 𝑴 𝒇 𝑴 𝒔 𝑨 𝒔 𝑨 𝒇 • Hysteresis is defined as a “lag” • Important mostly in Shape Memory applications • Hysteresis can be a design constraint or a benefit • Example: Actuators • Constraint: limits speed • Benefit: power savings
- 15. Fatigue • Fatigue is the inability of the nitinol to return to its preset shape • Number of cycles affects the amount of deformation • 12% deformation → 1 cycle • 5% deformation → 10,000 cycles • 3% deformation → 10 million cycles • Fatigue can be reset using heat retreatment
- 16. Ternary Alloys 1 Aluminum ↑ Fatigue life, Flexibility ↓ Weight 2Cobalt ↑ Stiffness ↓ Shape Memory 3 Copper ↑ Fatigue life ↓ Hysteresis 4 Hafnium ↑ Transition Temp. (150ºC) 5 Iron ↑ Tensile strength ↓ Transition Temp. 6 Magnesium ↑ Fatigue life ↓ Stiffness 7 Niobium ↑ Hysteresis (100ºC) 8 Palladium ↑ Transition Temp. (600ºC) 9 Platinum ↑ Transition Temp. (> 600ºC) 3rd Element And Possibly More…
- 17. Providing for You » Manufacturing Capabilities » Engineering Services
- 18. Manufacturing Capabilities Vacuum Melting Drawing and Rolling Mass Production Electrochemical Processes Physical Vapor Deposition Vacuum Sputtering
- 19. Engineering Services Heat Treatment Surface Treatment Thermomechanical Testing Shape Setting Laser Welding Transition Temperature Characterization
- 21. https://www.kelloggsresearchlabs.com/ info@kelloggsresearchlabs.com 1-(855)-583-5353 T H A N K Y O U K E L L O G G‘ S R E S E A R C H L A B S
Editor's Notes
- The unique characteristics of nitinol’s double phase was first discovered by William J. Buehler while he was working on ICBM nose cones at Naval Ordinance Labs in 1959 And of course the unique properties of nitinol were discovered by accident like many other revolutionary discoveries. The shape memory effect was not discovered until 1961, 2 years later by the same Naval Ordinance Labs group. And with this they realized that low grade thermal energy could be converted to high grade mechanical energy. Scientists continued to experiment with nitinol trying to determine the mechanism behind the shape memory effect. Leading up until the National Heat Engine Conference in 1974 where the top scientists gathered to discuss their discoveries around nitinol. Following the conference, they determined that the material science knowledge of nitinol was not extensive enough for commercial use. Until nitinol started to make a reemergence when it was used in Nike’s line of Flexon Eyewear in 1995 These glasses could be bent to extreme lengths but would snap right back when released This was the first application of superelastic nitinol. By 2005, the Materials Science knowledge had been developed to the point where nitinol could finally be used in widespread commercial use. Since then, nitinol has been used in a variety of different ways from surgical stents to the long sought after heat engines.
- - First, we will delve one of the more interesting characteristics of nitinol: shape memory - SMA: an alloy that when cold it is malleable, but recovers it shape when it is heated. *pass out springs for listeners to distract themselves* This phenomenon is due to the special characteristics rooted in the atomic structure of the Nitinol Nitinol has 3 different atomic structure phases: Austenite, Martensite, and R-phase. Martensite’s crystal structure allows the bonds to rotate giving the appearance of malleability. Austenite is the phase where the nitinol is rigid and elastic. Since the bonds rotated without breaking, when it transforms to austenite, it returns to its original form. The R-phase is another crystal structure, but most applications ignore it. (sensor applications because its non-hysteretic) The most common forms of SM Nitinol are designed to display 1-way SM, although 2-way SM is possible With one way shape memory, the nitinol is malleable when cold and can be distorted. When heated it will return to it preset shape. That’s the extent of 1-way SM. Although with 2-way SM, the nitinol will have a preset shape for when its cold as well. So when heated, it will exhibit one shape, and when it’s cold, it will exhibit a different shape
- The other classification of nitinol is superelastic. Superelastic refers to a material that when the stress on it is removed, the strain it underwent is completely recovered. Essentially when the material is deformed, it will return to its original shape when there’s no force being applied to it. Superelastic nitinol still has a transition temperature. Although, it will not reach that temperature because its application environment will always remain above the transition temperature. With that being said, the closer the nitinol is to its transition temperature, the more superelastic it will be. When its close the Af temperature, the nitinol will experience stress induced martensite when a stress is applied to it. This transformation between the martensite and austenite phases is what makes the nitinol exhibit superelasticity Super elastic nitinol is especially useful for applications that have a high amount of strain.
- Let’s talk about the concepts on application that nitinol can fit in. First is vibration dampening. In these applications, nitinol is exceptionally special because it has dampening properties similar to that of silicone rubber but the strength of titanium. Then we have actuators, which can be linear, rotary, or complex. Our single use actuators have proven to recover from extreme deformations Next is temperature control valves, where nitinol can activate at a specific temperature or even specific temperatures by utilizing the 2-way shape memory effect. Lastly we have medical devices. Nitinol, with its great biocompatibility, also has good shock dissipation, high deformation, and a long fatigue life which makes it great for a variety of implants.
- Some projects we have worked on recently include: Designing antennas for satellites. The nitinol antenna is packed tightly in the satellite until the sunlight activates the shape memory effect of the nitinol allowing it to extend out. Another project was to design prosthetic stents. Using the shape memory effect, we were able to have a condensed nitinol stent expand just with the thermal energy of body heat. Being superelastic, they are also able to withstand over 50 million cycles. Lastly, we are currently working to develop a nitinol mesh. The current role of the mesh for this project is to hold open small incisions made during a surgery. The nitinol mesh will be rolled to reduce its size then the body temperature will activate the mesh, opening it up and opening the incision.
- Nitinol is classified by 11 critical temperatures. So to explain this concept we have an atomic structure vs. temperature graph Each phase has a start and a finish temperature. There is also a peak temperature, which represents the temperature that produces the highest rate of change of atomic structure in the nitinol. Which on the graph would be the points of inflection on the graph between Ms and Mf as well as between As and Af The temperature we refer to the most is the transition temperature of the nitinol which is represented by the austenite finish temperature An equilibrium temperature is possible only if Ms > As which can be attributed to the Gibb’s free energy of he system There is currently no method for measuring the Mo and therefore must be calculated. Last is the martensite difficult temperature which represents the temperature where producing stress induced martensite is extremely difficult. Not being able to form stress induced martensite hinders the superelasticity of the nitinol Above the martensite difficult temperature nitinol acts as a linear elastic As you can see by the graph and from my explanation, there is a temperature range where the metal has a mixture of both martensite and austenite atomic structures which leads me into the next technical concept…
- Hysteresis. We define hysteresis as a lag, specifically a lag in the transformation of the nitinol atomic structure when shifting from martensite to austensite or vice versa. There is a temperature gap to overcome before inducing a thermal atomic structure transformation As you can see on the graph, this range between Mf and Af is what we call thermal hysteresis. Hysteresis is a concern mostly in shape memory applications Hysteresis can be a design liability, where the presence of hysteresis may impede on the functionality of the nitinol. Although, it could also be a benefit. Take for example an actuator. Hysteresis can limit the speed of the actuator because it has to either cool down or heat up entirely through the hysteresis. But on the other hand it can help with saving power by allowing you to reduce the temperature in a steady state application. An equilibrium temperature is possible only if Ms > As which can be attributed to the Gibb’s free energy of he system There is currently no method for measuring the Mo and therefore must be calculated. Last is the martensite difficult temperature which represents the temperature where producing stress induced martensite is extremely difficult. Not being able to form stress induced martensite hinders the superelasticity of the nitinol Above the martensite difficult temperature nitinol acts as a linear elastic As you can see by the graph and from my explanation, there is a temperature range where the metal has a mixture of both martensite and austenite atomic structures which leads me into the next technical concept…
- Fatigue is an important characteristic of metals that withstand cycles of stress. Fatigue is essentially the inability of the nitinol to completely return back to its preset shape. For one-time use applications, fatigue is not a worry. But for applications where the nitinol will under go 10,000 or even 10 million cycles, fatigue has to be considered. The number of cycles can impact the amount the nitinol can be deformed and still recover to its set shape. For instance, a nitinol can recover approximately 12% deformation once, which is great for a one-time use application However, we have produced a single-use actuator that recovered from 250% deformation. On the other hand, nitinol can recover 3% over a course of about 10 million cycles What’s great about nitinol fatigue though is that it can be completely rehabilitated with a heat treatment! Another option for fighting fatigue is adding a 3rd element which can allow you to push up to a billion cycles..
- Ternary Alloys Adding a 3rd metal could benefit the function of your nitinol. Some examples of ternary alloys include adding the following metals to nitinol: Aluminum: which increases fatigue life and flexibility, while also reducing the weight for weight sensitive applications. Cobalt: can increase stiffness but suppresses SM effect, so using it in products such as high stiffness springs is beneficial. Copper: can drastically decrease hysteresis and also increases the fatigue life. Although it is much more difficult to machine. Hafnium: raises the transition temperature as high as 150°C. Iron: drives the transition temperature down while also stabilizing it and also increases tensile strength. Magnesium: reduces the stiffness and improves fatigue life, similarly to the aluminum alloy but w/o the density reduction. Niobium: increases the hysteresis as large as 100°C, which is useful in applications where transformation is not desired (F-16). Palladium: drives transition temperature up to as high as 600°C, but its very expensive. Platinum: also drive the transition temperature up, even higher than Palladium can, but again is very expensive.
- KRL is the fastest growing business in NH but we stick right by our customers throughout every step of the process. We will work directly with your engineering team to produce a product specifically tailored to your application
- There are a number of different manufacturing services that KRL can provide for you: Vacuum melting allows us to manufacture our own nitinol instead of importing it. With our in house equipment we can draw and roll wires and rods from nitinol ingots. Our manufacturing facility allows us to mass produce products that you may require for your products. We offer physical vapor deposition which allows us to coat your product with a number of inorganic and organic coatings. There are 3 electrochemical processes that we provide which are electropolishing, electroplating, and passivation Lastly, we are establishing our vacuum sputtering technologies and hope to have them functional soon.
- Not only do we offer a number of manufacturing services, we also provide multiple engineering services which allows us to customize the nitinol to fit your exact needs Heat treatment is required to establish and optimize the shape memory effect in nitinol but it can also alter mechanical and thermal properties. We also offer surface treatment which determines how the nitinol will interact with its environment. Possible surface treatments include coating, polishing, and other chemical treatments. With our thermomechanical testing equipment we can provide you with a complete, temperature dependent, mechanical profile of your nitinol system. We do provide shape setting services for your nitinol, making everything from simple shapes for proof of concepts to complex systems. Attaching nitinol to itself or other materials can be difficult, but with our high quality fiber and YAG lasers strong attachments can be made. We also have equipment to perform stress free tests (DSC), stressed tests (Bend and Free Recovery), and even active tests to further characterize your nitinol.