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STRUCTRAL APPLICATION OF SMART MATERIALS
The development of durable and cost effective high performance construction materials is important for the economic well being of a country. Assorted developments are being made these days to increase the strength and durability of these structures and make them accustomed to various natural changes.
The technology now addresses the growing needs for strengthening aging structures , rehabilitating damaged structures and designing new structures to more severe requirements and for longer service life. Innovations are being made in structural materials and to develop superior products that have positive impact on our cost-effective competitiveness, national security and quality of life. In order to achieve the above requirements evaluation of structure is essential. Figure(1) shows the evaluation components of structure.
Engineers have to use three main criteria to select materials: desired properties, availability of manufacturing technology, economic feasibility. One of the latest development in this context is the development of smart material.
WHAT ARE SMART MATERIALS?
“Smartness” of a material is characterized by self-adaptability, self sensing memory and decision making. Smart materials are the materials that respond with shape or other property change upon application of externally applied driving forces (electrical, magnetic and thermal). In other words, smart materials refer to materials that can undergo controlled transformations through physical interactions and are structured with multi-functionality. They have they are able to respond to slight variation in temperature, moisture, pH, electric or magnetic fields by changing their appearance, state and properties. They are exemplified as boon in tackling the problem of deteriorating civil infrastructure and they had influenced the life cost of these structures by reducing the upfront construction cost as they allow reduced safety factors in initial design.
SHAPE MEMORY ALLOYS
The term shape memory refers to the ability of certain alloys to undergo large strains, while recovering their original configuration at the end of the deformation process impulsively or by heating without any residual deformation. This is due to their two unique properties: pseudo-elasticity and shape memory effect. It had been found that these shape memory alloys first bridges the structure and then on application of heat, changes shape and clamp both sides of the crack together. The most efficient and widely used alloys include NiTi (Nickel-Titanium), CuZnAl and CuAlNi.