What is a Smart Structure? A smart structure is a system containing multifunctional parts that can perform sensing, control, and actuation; it is a primitive analogue of a biological body. Smart materials are used to construct these smart structures which can perform both sensing and actuation functions.
If truly smart, these intelligent systems can determine their present state, decide what is the optimum or more desirable state and carry out an appropriate response in a controlled and timely manner, that is, a smart structure has the capability to respond to a changing external environment (such as loads and shape change) as well as to a changing internal environment (such as damage or failure). Smart systems are defined as ensembles whose dynamic can be monitored or modified by distributed sensors and actuators, in accordance with an integrated control law, to accommodate time-varying exogenous inputs or changing environmental conditions.
Smart Material Based Systems (SMBS) are defined as electro-mechanical systems integrated with sensing, actuating, control and computational functions provided by such materials. Through system integration and compact design, systems with less complexity, lower cost and higher reliability can be built. Smart materials are those that receive, transmit or process a stimulus and respond by producing a “useful” reversible effect.
They are often also called “responsive” or “intelligent” materials and depending on changes in some external conditions or the type of stimuli, “responsive” materials change their properties (mechanical, electrical, appearance), their structure or composition, and/or their functions. What is a Smart Material? A smart material prepared by the university of Michigan. | | Introduction: The last 30 years, scientist and technologist have made amazing developments on the design and integration of electronic and machinery using conventional materials.
Now, new possibilities in engineering design with higher levels of functionality are being created by (a) the development of new “responsive” materials; (b) the awareness of their capabilities and (c) the control on the minutarization process. An important feature of the technology of smart materials and structures is that it facilitates the integration of important core engineering concepts such as design and manufacture, materials science, sensor and actuator technology, information/signal processing, modeling, etc.
The aim of these integrations is to transform passive structures into active ones. It makes use of physics, mathematics, chemistry, computer science, materials science, electrical, and mechanical engineering knowledge. The design of these structures with higher levels of functionality is changing the traditional practices in all engineering disciplines. For the design, analysis and manufacturing of these active systems is necessary to integrate basic engineering concepts and directed towards specific products (product realization) using a strong multidisciplinary approach.
It necessitates of human creativity and innovative ideas to serve human society for such tasks as making cars safer, a more comfortable airplane, a self-repair water pipe, etc. Smart structures can help us to control the environment better and to increase the energy efficiency of devices. It’s important that we understand that in the manner that we created the structures of a Smart Material is going to be the results that we will obtain from it. The Smart Materials and Smart Structures are also very challenging, because they combine the better parts of Science and also requires a lot of knowledge to can work on it.
A space structure with impedance monitoring unit Examples: A useful example is during an earthquake, MR fluid inside the dampers will change from solid to liquid and back as tremors activate a magnetic force inside the damper. Using these dampers in buildings and on bridges will create smart structures that automatically react to seismic activity. This will limit the amount of damage caused by earthquakes. With this example we demonstrate that with the smart Materials we are preparing for the future security.
These are but a few of researches. Brought to their logical conclusions, uses for smart materials will enable engineers of the future to incorporate into their designs the features of safety, durability, and convenience that are the goals of today’s researchers. Importance of Smart Materials and Structures The importance of smart materials and structures is best expressed by the following statement [after ref. 1]: “The key to 21st century competitive advantage will be the development of products with increasing levels of functionality. Smart Materials” will play a critical role in this development, where we define these as materials that form part of a smart structural system that has the capability to sense its environment and the effects thereof and, if truly smart, to respond to that external stimulus via an active control mechanism” Types of Smart Materials In comparison to conventional materials, smart materials are functional, that is, they are required to undergo purposeful and reversible changes, playing an active part in the way the structure or device works.
Their degree of smartness is measured in terms of their “responsiveness” to environmental stimuli and their “agility”. Responsiveness implies a large amplitude change while agility implies a fast response. Their classification is based on the relationship between the stimulus and response. Almost all high performance devices are based on crystalline materials. The physical and chemical properties of these devices depend not only on their crystalline structure but also on the crystal direction in which they are been measured (anisotropy). Piezoelectric
These are crystals which acquire a charge when compressed, twisted or distorted. Piezoelectric materials have two unique properties which are interrelated. When a piezoelectric material is deformed, it gives off a small but measurable electrical discharge. Alternately, when an electrical current is passed through a piezoelectric material it experiences a significant increase in size (up to a 4% change in volume). An illustration of the Piezoelectric Effect Electrostrictive, Magnetostrictive and Elastorestrictive. These are materials that change in size in response to either an electric or magnetic field.
Conversely, they can produce a voltage when stretched. Electro-rheostatic (ER) and magneto-rheostatic (MR) materials are fluids, which can experience a dramatic change in their viscosity. These fluids can change from a thick fluid (similar to motor oil) to nearly a solid substance within the span of a millisecond when exposed to a magnetic or electric field; the effect can be completely reversed just as quickly when the field is removed. MR fluids experience a viscosity change when exposed to a magnetic field, while ER fluids experience similar changes in an electric field.
The composition of each type of smart fluid varies widely. The most common form of MR fluid consists of tiny iron particles suspended in oil, while ER fluids can be as simple as milk chocolate or cornstarch and oil. Thermoresponsive – Shape memory alloys=. Shape memory alloys are the dominant smart material, change shape in response to heat or cold (change in temperature) Shape memory alloys (SMA’s) are metals, which exhibit two very unique properties, pseudo-elastic and Shape Memory Effect.
Conventional bone plate used to repair jaw fracture Electrorheological ;amp; magnetorheological= these are fluids that can change state instantly through the application of an electric or magnetic charge. pH-sensitive= these are indicators that change colors as a function of pHUV-sensitive and Electrochromic Electrochromic materials are those that have the ability to change its optical properties when a voltage is applied across it.
Smart polymers = Polymers that respond strongly to small changes in the external conditions Smart hydrogel Engineered response gels that shrink or swell by a factor of 1000, and that can be programmed to absorb or release fluids in response to almost any chemical or physical stimulus Conventional bone plate used to repair jaw fracture Examples of Medical applications More specific applications Sensors built into aircraft will let maintenance people know when repairs or more sophisticated inspections are required.
Smart materials are beginning to play an important role in civil engineering designs for dams, bridges, highways, and buildings. They are useful also to remove corrosion of a Navy Pier and also engineers are introducing sheets of composites materials containing sensors that will alert maintenance engineers to the need for repairs. Other important industry that are including Smart Materials they are working in a project to develop smart car seats that can identify primary occupants and adapt to their preferences for height, leg-room, back support, and so forth.
Technology also exists to enable cars to tell owners how much air pressure tires have, when oil changes are needed, and other maintenance information. Developing solid state and smart materials technologies will bring costs down. * Another important application is using the MR fluid . The MR damper developed at the Intelligent Structures and Systems Lab uses the mixed mode configuration. The MR damper has a built-in MR valve across which the MR fluid is forced.
The piston of the MR damper acts as an electromagnet with the required number of coils to produce the appropriate magnetic field. Also the MR damper has a run-through shaft to avoid an accumulator for the design of cars. A view of the one dimensional force feedback system Other applications using MR fluids are: Since MR fluids have a very high yield stress they can be used to control the transmission of torque in rotating machinery too. For example, they may be used in an automotive power train to transmit torque from the engine to the transmission and the vehicle.
Advanced Control System Design using MR dampers- MR dampers can also be used to achieve sliding mode control in vibrating systems like seat suspensions, vehicle suspensions, washing machines and prosthetic devices. Modeling and Control of Active Spiral and Patch Antennas A simple mass-spring-MR damper system This is just a basic overview of the uses and the applications of smart materials in general and industrial fields. Our ppt will be based on some specific applications and general uses of smart materials. THANK U