National conference on modern trends in
Science & Technology
MTST’11
14th & 15th October 2011, Moodbidri
Mechanical Engg Session ME6 OP56
Functional Shape Memory Material Conceptualisation for High Frequency Actuation situate Abstract
MURALIDHAR LAKKANNA This manuscript reviews illustrated fundamental intelligence mechanisms, pertinent techniques & Research Scholar Department of Mechanical Engineering National Institute of Technology Karnataka Surathkal, Mangalore 575025 Karnataka, India
The author has over 15 years of professional experience & currently pursuing doctorial research can be reached at
[email protected]
experimental methodologies strategically adopted to engage shape memory material embodiments across high coupling frequency i.e., feasible approaches inspired to achieve tenacious shape memory function. Logically micromechanical approach overweighed conventional macro mechanical approach to synthesize combinatorial behaviour involving characteristics like sensor, processor, actuator, feedback controller, etc, Although garbled conceptual discoveries occurred decades ago, mere recently they are colligating a as potential methodology. Stiffness increase, dynamic moduli with temperature and/or frequency enable distinct capabilities to control & modulate between static and dynamic states. Additionally intrinsic spontaneous feedback recognition methodology enhances the functional shapememory technology sophistication. Hence, high frequency shape-memory material embodiment would definitely play an important role in advancement of shape memory materials © 2011 Lakkanna Received on 30 Aug 2011, Peer reviewed and accepted on 24 Sept 2011 and Published on 15 Oct 2011
Keywords: High frequency actuation, Shape memory materials, βW-TiNi
1. Overview of Smart Functional Materials According to modern anthropology human evolution & material knowledge, advancements have strong correlation since 1.5 million years. Accordingly technology has been swiftly progressing across a broad spectrum of domains demanding more advanced functions like greater convenience, compaction, portability, etc, Exhaustive developments have radically improved human understanding of material science discipline, i.e., fundamental as well as advanced processing techniques, methods, capabilities, etc., at various levels as schematised n figure 1.
Figure 1: Schematic representation of actuation frequency vs strain range [11]
Consequent to change of physical, chemical or biological environment state materials exhibit many properties. It is often difficult to group materials strictly into following intervals [3], Classical materials (CMs) those used for general purpose, noncritical and low stress applications. CMs are considered as continuum realm without gaps or empty spaces or close packed physical particles so micro structural information is disregarded. Standard Engineering Materials (SEMs), which are configured / expected to possess parametric properties. SEMs are predominantly used to accomplish passive functions such as supporting, stiffening, connecting, etc., Accessing standardized properties by selecting appropriate engineering material from the library is more or less, a straightforward approach. Pertinent mechanical behaviour response characteristics of SEMs are assessed using macroscopic & microscopic information. In Organised by Dr. M.V.Shetty Institute of Technology, Vidyanagar, N.H.13, Thodar, Moodbidri 574 225, Karnataka
doi 10.13140/2.1.4592.2249
Muralidhar L , National Conf MTST, (Oct 2011),ME6, Pg 56‐1 to 8
micromechanical approach macroscopic matter is considered to consist of microscopic structural elements interacting with each other. Individual mechanical response behaviour of each elemental ensemble is mutually interdependent, discrete, deterministic, etc, [8]. High-performance materials (HPMs) or advanced engineering materials, which are synthesized to exhibit superior & outstanding properties (extreme service environments, rigorous engagement, rugged condition, etc,). In addition to passive functions HPMs also accomplish active functions i.e., changing shape, properties, etc,. So functional material selection is up against a tremendous complexity in anticipation of an active behaviour in conjunction with a particular passive behaviour. Amazing material properties like physical, mechanical, thermal, electrical, etc are persistently engineered across multiple domains to realize spawning functionalities strategic performance configurations. HPMs leverage specific advantages of micro structural mechanisms to potentially configure functional performance targeting specific engineering parameters beyond CMs & SEMs by overcoming, curtailing, or compensating material properties dependence on external parameters [1]. Subsequently simultaneous optimisation of macro structural parameters could be carried out [9]. HPMs offer exceptional abilities concurring to both stringent constraints as well offer extended functionality (like electromagnetic shielding, etc,) spawning fresh sub group of materials called functional materials, with multimodal degrees of intrinsic discriminations like shapes, sizes, forms, structure, composition, etc, [22]. Most intelligent system performance adoptions encounter speculative technological challenges illustrating "high risk / high reward". Active material function involves nonlinear & time dependent behaviour due to complementary intrinsic mechanisms. Pahl & Beitz (1996) prophesied that concretization is essential similar to CMs & SEMs combinatorial embodiments. So that material properties could be directly / relatively accessed from simple interrelationships. Probably standardized material property do not exist for functional materials, consequently Pugh (1991) expressed that functional material embodiments always have configurable property ranges between a broad spectrum with highly complex physical interrelationships. Over the past decade, smart material technology has evolved to a more sophisticated level possessing autonomous intelligence relative to dynamic state changes [7]. “Smart Materials” go far beyond respond ability with highly configurable, reversible, accurate & reliable property changes compatible to external stimuli imitating the role of sensor and actuator [13], continuous and spontaneous feedback [2], etc,. Smart materials definition was controversially arrived with mutual consensus at a special workshop organised by US Army Research Office in 1988, where four qualifying features ‘sensors’, ‘actuators’, ‘control mechanism’ and ‘timely response’ were recognised. “A material possessing built-in or intrinsic sensor(s), actuator(s) and control mechanism(s) capable of sensing a stimulus, responding to it in a predetermined manner and extent within a short / appropriate time, and reverting to its original state as soon as the stimulus is removed” [14, 16]. Sustainable societal requirements in energy, health, mobility, safety, security, etc, offer huge potential to engage smart functionalities, so novel intelligence smartness oriented research efforts exploit intrinsic material characteristics [6, 18]. Futuristic synthetic smart material researches in biomimetics have amazingly inspired engineering concepts from biological matter and structures. Particularly five cognitive sensual behaviours viz sight, sound, smell, taste and touch corresponding to visual/optical, acoustic/ultrasonic, electrical, chemical and thermal/magnetic functionalities [19]. Smart materials possess to accurate stimuli response interrelationship self-configuring abilities. Functional smart materials assimilate spontaneous neurosignal response configuration with autonomous memory, endowed perception, predictable actions, accurate control and reliable behaviour. Today ultra-smart materials are paving ways to realise innovative systems with functional abilities of ultimate intelligence, extreme adaptability, higher degree of freedom, emotion, etc., such unique and marvellous functionalities are modelled and simulated to deduce magnificent orders of system integration [15]. Obviously synthetic alternatives are still starringly primitive compared to their natural counterparts in terms of efficiency, agility, coordination and autonomy [17]. Nature has evolved a great synergy between material (muscles), structure (wings) and control (brain) that is yet to be replicated. Smart materials are further subdivided into materials exhibiting direct or indirect coupling, a.
Piezoceramics, piezoelectric polymers, magnetostrictive ceramics, SMAs and magnetic SMAs are grouped as active smart materials exhibiting a direct coupling. Active smart material are capable of naturally (freely) absorbing / releasing energy within service regime implying that either mechanical or non-mechanical field can serve as an input while the other as output
b.
In contrast, passive materials such as electro-rheological fluids (ERF) and magneto-rheological fluids (MRF) indirectly change electric and/or magnetic fields coupled with their mechanical behaviour through their fluid viscosity change. This indirect oneway coupling usually lacks the reciprocity of two-way coupling typically exhibited by directly coupling two fields 2
Muralidhar L , National Conf MTST, (Oct 2011),ME6, Pg 56‐1 to 8
Figure 2: Classical SMA adoption representation based on response strain to coupling frequency abilities [10]
SMAs are thermo mechanical materials capable of absorbing / releasing thermal and / or mechanical energy i.e., encountering simulative external thermal gradient (heated or cooled) stimulus exhibit topological change response (expand, shrink, bend, stretch, etc) as represented in figure 2. Traditionally heavy mass was perceived to be strong & fragile and conversely light mass w was perceived to be weak and tough, but rationally SMAs are strong & tough. So two prominent metrics embraced to c compare active functional abilities are density & 3
elastic modulus. Accordingly, density varies between 5000 to 9000 Kg/m & modulus varies between 10 to 100 GPa. Therefore active functional ability depends on two key design drives; energy density (available work output per unit volume) and coupling frequency ideally SMAs are expected to have both high energy density and high frequency as represented in figure 3 & 4. Energy density being defined as the product of response strain to stimulating stress, assuming material operates under isothermal state. Specific energy density (work output per unit mass) is a ratio of energy density to mass density.
Figure 3: Energy density diagram indicating typical al ranges of stimuli stress to response strain for different materials [5]
Figure 4: Actuation frequency diagram comparing frequency ranges of different active materials exhibiting direct coupling [5]
2. Origin of SMAs Etymologically "Martensite" was commemoration of extensive study by Adolf Martens (1850 - 1914), a German metallurgist who in 1890 discovered displacively transformed hard regular crystal structure with plate like grains as opposed to slower diffusive transformations in FeC system. Microscopically these acicular lenticular grains had lens / needle shaped morphology. This was the first major step towards eventual SMA discovery; subsequently martensitic transformation established as most widely studied phenomenon. Similarly "Austenite" was honourably named after Sir William Chandler Roberts Austine (1843 - 1902) who in 1896 extensively investigated solid state diffusion coefficient (configurational kinetics) of gold in lead and discovered a high temperature solid solution phase existing above critical temperature In 1932 Arne Ölander, a Swedish physicist demonstrated "Shape Memory Effect” (SME) phenomenon from AuCd by cyclically lifting a load mass at Brussels World’s Fair. In 1938 Greninger & Mooradian first witnessed peculiar martensite phase formation and disappearance consequent to temperature cycling of CuZn system. Based on extensive experimental studies in CuZn and CuAl systems, such reversible thermo elastic memory phenomenon from interphasial transformation explained a decade later by Kurdjumov & Khandros (1949). In 1947 while investigating unidentified debris of Roswell crash at Battelle Memorial Institute, Ohio; US Air Force General Wright Patterson et al., had suspected existence of TiNi composition from solubility perspective. Again, in 1949-second progress report on Roswell debris analysis submitted by Battelle scientists Criaghead, Fawn and Eastwood also 3
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indicated possibility of Titanium Nickelide system possessing rare "Memory" capabilities. In 1950, M.V.Nevitt discovered TiNi intermetallic structure by constituting Ti & Ni elements. In 1950 Chang and Read witnessed thermo elastic shape memory phenomenon during bending behaviour research of AuCd bars. Subsequently other researchers also witnessed thermo elastic reversible martensite transformation in many other systems like InTl, CuZn, etc., systems. A large number of SMA discoveries exhibiting exciting features succeeded followed from 1990 onwards as well as spreading into other domains, off them TiNi has been at the helm, because of its exquisite properties attracting both scientists & technologists across multiple disciplinary arena over the recent four decades to exploit unique functional memory phenomenon with nearly limitless possibilities. SMA Development William J Buehler made a landmark contribution in 1959; while exploring metallic alloys to heat shield nose cones of U.S. Navy Polaris missiles capable of withstanding re-entry into atmosphere. Arc melt cast bars kept on his table, had broad spectrum of temperatures from cold (nearer to ambient temperature) first bar to very hot just cast. While grinding surface irregularities he stumbled upon to witness acoustic damping change with their temperature change as all of them fell down over the concrete floor of his lab; cold bars produced a dull "thud" unlike just cast rang like bell quality. These unusual behaviours provoked Buehler to curiously investigate acoustic damping property variance TiNi bars exhibited along with Raymond Wiley & David Goldstein (both metallurgists) as a function of temperature from an altitude of early physical, mechanical and metallographic perspectives. They collectively captured various overtly exhibited unusual and unique behaviours like, a.
Polished plane metallographic surfaces when heated to 373K to 473K exhibited an obvious eruption or recon touring due to planar surface shearing occurrence along certain crystallographic planes only.
b.
RCW Wiley another NOL researcher witnessed stable (in size) micro hardness indentations at room temperature, but astonishingly the dents significantly reduced in size / vanished when slightly warmed up to study heat treatment effect at 373K to 473K
c.
Once again Buhler had left few deformed cast ingots on his desk under direct sunlight when he came back from lunch he noticed that those ingots shape were changed
d.
Curiosity also got its best in a 1961 laboratory management review meeting while demonstrating fatigue resistance properties of TiNi. At room temperature, Buehler had bent a demo (0.25mm thin) strip into an accordion shape, so could be repeatedly collapsed (folded) and stretched. During the meeting as the specimen passed around reviewers they who repeatedly "fidgeted" (flexed, squeezed, compressed, etc,) to understand fatigue resistance among them Associate Technical Director, Dr. David S Muzzey who being a pipe smoker applied heat from his lighter toe to folded strip. To everyone’s amazement, it immediately extended / stretched out longitudinally with considerable force magnitude i.e., with substantial energy conversion (heat energy → mechanical energy) was revealed; while unnoticed in Buehler’s metallurgical laboratory mechanical memory discovery was the missing piece of SMA puzzle… [and] became ultimate payoff even though, the shape memory alloy (SMA) phenomenon had been already invented.
All these startling discoveries were analogous to a “black box” myth as they lacked the most rudimentary basic understanding of why and how. That was when Dr. Frederick E. Wang joined Buehler’s group at NOL in 1962 possessing crystal physics expertise; who extensively studied TiNi by correlating unique previous observations. Interestingly memory observations correlated to acoustic damping change in about the same temperature range towards a more plausible & conclusive explanation. Hence, TiNi was a systematically lead discovery. Finally, Buehler, Wang and Pickart in 1963 synthesized complex A: TiNi between 873K and 439K. Possessing good mechanical properties in addition, they also witnessed reversible M: TiNi transformations at 439K i.e., shape memory effect. Through further extensive investigations, they were able to justify and quantitatively explain conflicting observations of previous investigators. Honouring their achievement, the term NiTiNOL™ was acronymised for Nickel Titanium discovery at Naval Ordnance Laboratory, White Oak, Maryland. Subsequently this discovery spearheaded many research efforts exploring SMAs microstructure, heat treatment, composition, etc.; In 1965 Co & Fe ternary alloying with TiNi were found to decrease critical transformation temperatures. In 1967 Raychem Corporation (under Jack Harrison) first commercially adopted TiNi (Fe, Co) system to develop "shrink-to-fit” pipe couplers known as Cryofit™ to join hydraulic tubes for Grumman Aerospace, who had a leaking problem with the existing hydraulic line couplers at 153K. Cryofit™ tube transformation temperatures were so low that were easily expandable (radial tube size) using a tapered mandrel at 63K to 77K and to prevent actuation occurrence before assembly were transported in liquid nitrogen. Subsequently in 4
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1970 Cryofit™ tube coupling were strategically deployed on U.S. Navy F14 fighter planes, it demonstrated SMA device reliability in an extreme pressure hydraulic system over a million couplings were produced later. Between 1963 to 1980 S. Miyazaki et. al exhaustively studied reversible martensitic memory mechanism and its crystallographic transformations and in 1982 distinguished SME and SE. The idea of using TiNi for biomedical applications was first conceived in early 1970’s, in that decade first wide scale orthodontic applications like dental braces exerting constant pressure on teeth was patented by George Andreason. Subsequently in early 1990’s first SMA based TiNi stents were commercially available. Apart from medical arena breakthrough, air conditioning vents, temperature sensitive valves, electronic cable connectors, etc. were also developed. Over the past decade, a strong swift actuation demand surged to alternate conventional hydraulic actuators, pneumatic devices, bimetallic strips and electric motors, etc. extensive studies have indicated high frequency SMAs are viable candidate as unique self-contained smart system [10]. 3. Introduction to High Frequency SMAs Primary developments were concentrated to classical 2
SMAs confined up to 10 Hz actuation frequency service regime. Due to limited actuation, coupling frequencies of commercially available TiNi applications had suppressed high specific energy density. Most TiNi actuator designs currently used are for position control, but they suffer from various deficiencies like slow speed, limit cycles i.e., oscillating around a command position instead of converging to it [21]. However over the last decade a great deal of demand for stable properties operating swiftly [10] are driven by strategic applications such as core
Figure 5: SMA grouping based on specific energy density & transformation frequency [Data source: NASA Library]
transportation (marine turbines, automobile and aircrafts)
jet engines, power generation systems (nuclear, oil and gas energy plants) in deep hole oil rigs, fasteners & vibration dampers, appliances (gas stove, heaters and many general home appliances), etc., Classical TiNi centric SMAs behaviourally deteriorate in higher frequency service regimes owing to increased proportion of slips & micro structural defects like interlocking, gliding, etc. exceeding displacive transformation. So developing TiNi with high specific energy density, good dimensional stability & capable 2
of operating at higher transformation frequencies exceeding 10 Hz has become increasingly important key technology to enable higher automation in numerous domains. HFSMAs developed by NIMS, Japan generated 15X force and 50X displacement relative to piezoelectric elements as well as replicable at any scale. TiNi matrix modifying techniques are conceptualised to extend TiNi capabilities to high frequency regimes, understanding and researched to predict their mechanical behaviour and introduce them into prototype devices. There are rather few successful demonstration adopting HFSMAs; nonetheless, quite a large number of studies are conceptualised. In an attempt to distinguish HFSMAs from their lower counterparts, many definitions have been put forward. One of the most 2
widely accepted definition was given by Firstov et al. describing HFSMAs as alloys with reverse transformation above 10 Hz in stress free conditions following any thermo mechanical treatment as shown in figure 5. 1.
NASA, Fundamental aeronautics program, Glenn is evaluating HFSMA feasibility of substituting PID controller integrated with windup protection for active clearance control actuation amidst high-pressure turbo jet engine transients [4]. HFSMA actuator concept prototype linked to shroud actively controlled clearance at critical operating points, also maintained speed and magnitude within the operating envelope avoiding detrimental blade incursions (rubs). HFSMA beams / strips embedded inside each chevron side centroid rapidly develop asymmetric stress state alternatively and thereby a.
during low altitude (low speed flight); HFSMA beams were quickly heated to austenite & chevron tips were bent into air flow to increase flow stream turbulence (enhancing mixing rate). As chevrons enhance mixing of right amount, jet engine noise diminishes quietly at lower decibels
b.
during high altitude (high speed flight) HFSMA beams were rapidly cooled to martensite & chevrons straightened, thereby increasing engine performance
Potential benefits realized were, a.
Annually saving millions of dollars to airline industry fuel costs 5
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Specific fuel consumption was minimized by actively controlling gap (dynamically occurring throughout flight missions) between turbine blades & shroud i.e., controlling differential clearance variations within tighter tolerance limits reduced leakage flows. In modern engines clearance was 1mm at low power conditions and reduced to a fractional value at high power conditions, fastest clearance rates of change occurred during take-off (low to high power transition), so actuating rate criteria was based on take-off event. a.
Lowering environmentally harmful NOx emissions and reduced engine weight will allow continuing reduction in aerospace related CO2 emissions
b.
Reduce exhaust gas temperature (EGT) overshoot during take-off / landing, a critical factor in extending on wing life of hot section components
c.
Improving time between engine overhauls each actuator was designed to bear 1.7 to 9 KN load; displace at least 1 mm, exhibit acceptable failsafe operability & reliability. Validation test results indicated HFSMA control system had minimal variability in clearance control performance across the operating envelope. Final actuator design was sufficiently compacted to fit within limited space (10 parallel HFSMA wires of 50mm in length) outside high-pressure turbine case and consuming only small amounts of bleed air to adequately regulate temperature
2.
Quick lubricant regulating TiNiW valves are investigated to feed high speed rotating shafts
3.
High-speed micro-actuator technology deployments with small transformation hysteresis are extensively explored; since TiNiW can realise complex spatial movements within compact size without additional resetting force. Although weak inherent memory strain have to be dealt from fatigue perspective swift micro actuation offers very promising high volume avenue.
3.1.
High Frequency SMAs Research Conception
By 1969 high frequency phenomenology was realised in CuAlNi, βW-TiNi, TiNiPd, etc., but βW-TiNi emerged as the most promising & superior among the candid HFSMA systems for a wide range of applications. High frequency shape memory ternary alloy TiNiW exhibit exceptional strain hardening capability in the temperature range 293K to 673K invoking extreme research importance. Higher work hardening enhances critical stress to detwinn martensite variants offering maximum recoverable strain, probably resulting from more residual stress induced defects introduced during martensite variant reorientation. Extensive studies have been made on processing, equilibrium phases, phase transformation behaviour, structure, sub structure, interface structure of martensite and precipitation behaviour during aging. Aging & quaternary alloying techniques have slightly improved shape memory & strength without disturbing other properties. Yet to date there is no complete report explaining fundamental mechanical properties relating strength to elongation relative to temperature of βW-TiNi under high frequency actuation. 3.2.
High Frequency Martensitic Transformation
Foundations of material science progress & technology development rely on sophisticated studies like crystallography, electrochemistry and metallography, etc., along with experimental methods (e.g., thermometry and measurement of electrical resistivity and hardness). Higher transformation frequencies are expected to increase reliability and reduce cyclic response time. During high frequency displacive martensitic transformation ratcheting, resulting stress field defects are prone to significantly inhibit microstructural mechanisms. So obviously understanding equilibrium, structure, microstructure, crystallography, stability, diffusion process effects on kinetics and thermodynamics of transformation and deformation behaviour for all phases are critically important from functional perspective. In fact, there is no collective knowledge readily depicting mutual influence on displacive & diffusion controlled martensitic transformations except for some decomposition process data [20]. Reversibility & swiftly transforming σ
HFSMAs exhibit lower Ms ; improved mechanical properties, stable transformation paths & with smaller transforming strains as grain sizes are reduced. HFSMA being a subset of viable materials with various transition envelopes require a more expansive research for fully. 3.1.
Need Identification
As per WTO 2007 statistics worldwide metallic trading in 2006 was US$ 201 billion a share of 1.7% in world trades, of which th
th
nonferrous trade value was 82%. COMTRADE data analyses revealed Titanium and Nickel concentrates were top 9 & 10 traded th
metals worldwide respectively. Because of planned development since independence today India is 6 largest titanium producer possessing 5% world market share. In contrast though Indian metallic market size was Rs 19,755 crore in 200708, titanium trading was only 0.6% on national metallic exports and nickel trading were 6
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negligible. Worldwide titanium and concentrates trade amounted to US $ 1.09 billion in 2006, USA being largest importer (with a $ 200 Million value) followed by Germany (US $ 146 million), Japan (US $ 91 million), Taiwan (US $ 81 million) and UK (US $ 70 million). India had been a principal source to Japan; which amounted to 44% of India’s total titanium and concentrate export in 200607. Other major targets India had been trading were Malaysia, South Korea and Australia. Indian titanium and concentrate export to other major importers such as USA, Germany, Taiwan and UK, being currently insignificant [S Prahalathan et. al.,]. According to Observatoire Des Materiaux Nouveaux of France accelerated material demand growth trajectory will impact anticipated economy growth rate in the decade ahead [Lastres, 1994:512]. Therefore, India has a very prosperous titanium opportunity ahead to seriously engage. An interesting fact surfaced during patent survey, according to International council for scientific & technical information (ICSTI) 2,32,560 patents on shape memory alloys have been granted worldwide, 2008 witnessed (highest) 23,759 patents, with a nearly 5000 patents under review in 2010; among them 75% were tagged to possessed commercial value in nature. The most prominent International Patent Classification (IPC) code was awarded to more than 2900 inventions with “shape memory alloy", “shape memory or memorizing material”, “shape memory device or devices”, “SMA” or “TiNi,” text strings in title, abstract, or in independent claim. Since 60's only USA and Japan were actively publishing research works, though china aggressively started activities from last 5 years; starting 2000 onwards a plethora of research works are being published, as a result patents are distributed all over the world [S.K.Bhaumik]. In June 1986 Government of India, DST, awarded research grants to Department of Material Science, S.N.Bose National Centre for basic science, Kolkata, to undertake fundamental TiNi studies [DST annual report 200910] subsequently a plethora of research efforts in multiple facets have been witnessed. Preceding works in India were at best, unconnected individualistic efforts on the basis of Kota Harinarayana report Government of India conceived a India centric smart materials, structures and systems technology strategy to knock huge potential. Nucleating National program on smart materials with a seeding budget of D75 crore in July 2000. Subsequently Board for Smart Materials Research and Technology (BSMART) was constituted to establish R & D facilities, integrate embroiled fraternity, foster scientific knowledge exchange, promote developmental research, infiltrate temperament, fascinate commercialization, enable smart products in diverse avenues, stride to rapid global progress. Since then BSMART has been prioritizing national needs and channelling funds to encourage developmental research activities [Nirupa Sen et. al,]. Successively Government of India launched another program DISMAS (Development Initiative for Smart Aircraft Structures) specifically for aerospace applications seeding Rs 19.26 crore sanctioned by DRDO in April 2001 to incorporate various smart technologies concepts in Light Combat Aircraft (LCA) by ADA, Bangalore specifically featuring Structural health monitoring, Active NVH control (Noise, vibration and harnessing), Conformal antennae and radome, Suppress controlling acoustic excitations, Active suspension control, Aerodynamic shape control and Active fluid dynamics. Consequently, NAL Bangalore has set up indigenous alloy fabrication & wire drawing with controlled microstructure facility. Prominent shape memory products developed in India were, a.
SMA actuators for robot manipulators & micro pumps in the order of 18mm diameter and 5mm height
b.
SMA wires or ribbons as finite control elements (trigger, drive, etc.,) fuel control valves and injectors leveraging their high specific energy density βW-TiNi was used as high frequency SMA owing to its swift action regime even though poor SME.
3.2.
State of Technology
Currently the greatest HFSMA technology advancement challenges are [23], a.
offer extremely stable mechanical properties for rapid coupling
b.
associate extreme strength & sufficient ductility
c.
exhibit consistent physical behaviours within restricted dimensions
d.
exhibit behavioural uniformity between static and dynamic states
Several studies collectively evolved high frequency SMAs, i.e., TiNiX ternary systems exhibiting stable properties at expedited transformation rates. Similar to classical SMAs, HFSMAs have identical crystalline fragments with matrix composition stoichiometry lying very close to their quasicrystalline Hume Rothary phase. A.C.Kneissl et al., compared microstructures of TiNi, βW-TiNi & CuAlNi by thermal cycling (4000 cycles) between product and parent phases using fine grained wires as well as course grained thin ribbons. They found βW-TiNi system had superior trainable qualities against functional fatigue i.e., stable recoverable strain. A.G.Mayer et. al., compared microstructures of TiNi, βW-TiNi & CuAlNi by thermally cycling (5000 cycles) between product and parent phases using fine grained wires as well as course grained thin ribbons. They found high magnitude pseudo plastic strain as well as pronounced irreversible strains, while TiNi exhibited 7
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degradation. Obviously, βW dispersion strengthening effect was very positive. H.Scherngell et. al., compared microstructures of TiNi, βW-TiNi & CuAlNi by thermal cycling (4000 cycles) between product and parent phases using fine grained wires as well as course grained thin ribbons, they witnessed cold working improved behavioural strain stability and annealing increased coupling amplitude but were found to have faster degradation rates. Indicating aging effect on the microstructure, functional memory and mechanical properties have to be revealed for better clarity. Also optimum aging conditions have to be determined to achieve most favourable combination of high transformation frequency with stable and good functional memory characteristics. K.Mehrabi et. al, investigated a range of W wt % additive effects on TiNi matrix and found optimum mechanical properties and functional behaviours were exhibited at 2 wt. % W. beyond 2 wt. % W rich dispersiods increases strength and hardness, which is related to wear resistance but diminished SME. P.J.S.Buenconsejo. et. al., found TiNi matrix grain size decreased rapidly as a function of supersaturating βW content. On the other hand annealed TiNi matrix grain size decreased slightly as a function of supersaturating βW content. They also witness above 10 at % W established micro structural barrier arresting TiNi grain growth. P.J.S.Buenconsejo. et. al., in another work found hysteresis reduced as a direct function of W wt. % additive content. S.F.Hsien et. al., have explained transformation sequence, phases, grain boundaries, patterns, etc., they witnessed transformation temperature of both Ti & Ni rich matrix reduced as a function of W content. They also found shape recovery improved by solid solution hardening of TiNi matrix containing W. X.J. Yan et. al., found W was less soluble in TiNi matrix instead formed fine precipitates and these W rich dendrites improved radiopacity significantly. So Ti50.3Ni47.7W2 composition is chosen as maximum TiNi matrix as well have sufficient βW particles dispersed to increase strength and exhibit stable response even at swift coupling rates. Coherent precipitates stiffen the matrix by hindering the dislocation motion. 3.2.1. Theme Shape memory effect, super elasticity, and good damping properties, uncommon in typical metals set aside Titanium Nickelide is a fascinating material with limitless possibilities to innovate self-locking, self-expanding, self-compressing devices, etc., Applicability of functional behaviours are controllability of characteristic properties., because mechanical behaviours are sensitive to inherent microscopic mechanisms, so mechanical behavioural investigation is proposed for βW-TiNi. Therefore a systematically lead transformation ratcheting have to be explored at various controlled stress combinations with mean stress below evolving peak & valley strains, nominal elastic modulus as well as energy dissipation have to be analysed relative to loading condition bias. Mechanical behavioural dependence upon biasing load can explain high frequency effects. Statistically deduce logical inferences from complex host responses and scientifically analyse relative to attributed fundamental knowledge from reviewed works. Nonlinear active and linear passive mechanical behaviour of βW-TiNi need extensive investigation to engage in high frequency application. βW-TiNi complex interrelationship as well as behavioural dependency on several factors has to be simplified with high degree of accuracy & reliability to promote adoptions. Accurate analytical constitutive models to predict βW-TiNi behaviour are essential. 3.2.2. Precept Aggressive research effort is essential to massively adopt βW-TiNi. This will significantly influence currently designed & used products, which are mainly prohibited by lack of efficient as well as comprehensive service range concurring to their exciting behaviours. Research community has to aggressively focus future efforts on strategic developments. Accordingly, these reviews have been presented in order for industrial, technical, and financial goals to be achieved. Significant results & conclusions are expected to, a.
Enable innovative applications βW-TiNi will catalyze major technological innovations as a basis to design, develop and substitute certain strategic materials. βW-TiNi is potentially capable of discriminating between static or shock loading by spontaneously generating a large retarding force against shock stresses (Shock absorbers) [15]
b.
Optimise performance & enhance reliability in current & future βW-TiNi centric systems Broad based technologies offering higher strength to density ratios, greater hardness and wear resistance and one or more superior thermal, electrical or optical properties compared to classical materials, offer savings in total energy consumption, 8
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improved performance at reasonable cost and less dependence on strategic and critical mineral resources [US Bureau of Mines, Annual Report, 1992] c.
Evolve βW-TiNi as value adding optional candidate like enhancing functional scalability Synonymous to advanced materials, high value added βW-TiNi are expected to produce totally new epochal characteristics and new social values by driving sophisticated manufacturing processes and technologies and/or commercialisation technology [Kaounides, 1995: 289].
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Organised by Dr. M.V.Shetty Institute of Technology, Vidyanagar, N.H.13, Thodar, Moodbidri 574 225, Karnataka
doi 10.13140/2.1.4592.2249
