Civil engineering materials thesis

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Civil Engineering Materials Paper 1

An Introduction to Civil Engineering on the Application of Intelligent Materials

Abstract With the continuous improvement of people's requirements for the quality and use of civil engineering functions, a variety of intelligent materials, including fiber optics, piezomagnetic, piezoelectricity, memory alloys and other intelligent materials in the field of civil engineering have been widely used. The article introduces the concepts and characteristics of smart materials and their applications in civil engineering, and looks forward to their application trends in the future.

Keywords smart materials; civil engineering; characteristics; development trend

Introduction

At present, with the development of materials such as optical brazing, piezomagnetism, piezoelectricity, and shape memory alloys, smart materials have been widely used in various fields of civil engineering. The most basic smart materials are generally known as perceptual materials, which can sense internal and external stimuli. Materials that sense changes in internal and external conditions and make adjustments to adapt to the environment are called actuator materials. Nowadays, smart materials, generally need a variety of materials composite assembly to realize the diagnosis, repair, and adjustment of the material structure in the case of environmental changes.

First, the type and characteristics of smart materials

The concept of smart materials was systematically put forward in the early 1980s, and the end of the 1980s to get unprecedented development space. With the development of fiber optics, piezomagnetism, shape memory alloys and other smart materials, so that it has been more widely used in the field of civil engineering. Intelligent materials with their different functional characteristics can be usually divided into two categories, one for the perception of the external or internal stimulus intensity of the role of materials, known as sensory materials. The other category is materials that can respond to or drive changes in external environmental conditions or internal states, also known as intelligent drive materials. Intelligent material structure has three elements of control, sensing and driving, which can utilize its own perception to process information, issue instructions and execute actions, and then realize various functions such as structural self-monitoring, diagnosis, detection, repair, correction and adaptation. In general, it is difficult for a single functional material to have the above functions, which requires the group element to compound or assemble a variety of materials and constitute a new smart material to realize.

Second, the application of intelligent materials in civil engineering

1. The application of shape memory alloy

Shape memory alloy is a kind of intelligent alloy material with shape memory effect, as a new type of functional material, the main advantage is that in the process of excitation of shape memory effect of the material, the material can produce higher than 700 MPa of the return stress and 8% or so, and at the same time, it can have a strong response strain. The main advantage of the new functional material is that during the process of excitation of the shape memory effect, the material can generate a return stress higher than 700 MPa and a return strain of about 8%, and at the same time, it has a strong energy transfer and storage capacity. The application of this property enables the materials to be placed in various structures to realize the application research of self-diagnosis, toughening, strengthening and adaptive control of the structures, and the materials can be developed into intelligent actuators to carry out the application research in the aspects of structural deformation, damage, cracks and vibration. Phase transition pseudoelasticity and phase transition hysteresis performance is another advantage of shape memory alloys, in the loading and unloading process of its stress-strain curve constitutes a ring, indicating that the material in the process can absorb the dissipation of more energy. Shape-memory alloys have a phase-change restoring force of up to 400 MPa, which can be combined with this property to develop a passive energy dissipation control system for shape-memory alloys that can realize phase-change pseudo-elasticity and can be used for passive control of energy dissipation and seismic resistance in civil engineering structures. Usually, the shape memory alloy passive energy dissipation control system is placed between the layers or at the bottom of the structure, which is used to realize the energy dissipation system's perception of the interlayer deformation of the structure, thus playing the role of consuming seismic energy. The results of the study show that after the energy dissipator is installed in the shape memory alloy structure, the energy dissipator can absorb about two-thirds of the seismic energy and significantly inhibit the displacement of the structure.

2. Application of piezoelectric materials

Piezoelectric materials generally refers to the receipt of pressure, the material will appear at both ends of the voltage of the crystal material. The application of piezoelectric materials in civil engineering mainly includes static deformation control of structures, noise control and seismic wind resistance and other fields. The traditional method of using piezoelectric materials is to sense the vibration of the structure through piezoelectric sensing elements, and utilize the output results of the sensors to realize the perception of vibration and early warning. On this basis, take the appropriate control algorithm to control and quantify the input of the piezoelectric body, so as to realize the control of structural vibration, which is the current research frontier of piezoelectric smart materials. With the depth of research and technological advances, piezoelectric intelligent structures in civil engineering should be more and more extensive.

3. Application of optical fiber

Optical fiber is composed of outer cladding and inner core, is a fibrous optical communication media materials, the material using advanced information transmission technology initially used in communication transmission systems, as the information carrier photons in the speed and capacity than the electronic, so the more rapid development. Photons have a high parallel processing capacity and high information rate, the potential in the information capacity and processing speed to get full play. Fiber optic materials are used in monitoring, sensing and long-distance transmission of information, etc. Fiber optic as a sensing element is embedded in the traditional concrete structure to achieve automatic monitoring, diagnosis, control, forecasting and evaluation of the structural indicators and other functions, and will be embedded in the shape memory alloy and other driving elements, the organic combination of the information processing system and the control element, so that the concrete structure has an intelligent function to achieve the concrete structure self-diagnosis and repair. Structure self-diagnosis and repair. In the civil engineering structure diagnosis and active control of seismic response, fiber optic materials have been used as a more ideal material for the design of the sensor, China has also been used for testing and evaluation of the Three Gorges Dam.

4. Application of piezomagnetic materials

The application of piezomagnetic materials in civil engineering mainly includes magnetorheological materials and magnetostrictive materials. Based on the principle of magnetorheological materials, when the strength of the magnetic field is higher than the critical strength, the magnetorheological in a very short period of time from the liquid state to the solid state. Between solid and liquid can be based on the magnetorheological fluid characteristics of fast, controllable and reversible nature, control fluid properties when the implementation of the need for low energy, so in the smart structure is usually magnetorheological fluid as the main material of the dynamic device. Based on this, magnetorheological materials can be used in the structure of high-rise buildings to realize semi-active control of earthquakes. Because of the broad prospects for potential applications, magnetostrictive materials have received a great deal of attention in recent years. Magnetostrictive materials have a strong magnetostrictive effect, this material can be reversible between electromagnetic and mechanical conversion, this property makes it can be used in high-power ultrasonic devices, sonar systems, precision positioning control and many other fields.

Third, the development trend of smart materials

In the field of civil engineering, the development trend of smart materials is concentrated in the following three aspects. First, real-time monitoring and detection of the structural state, integrated sensing and drive components in civil engineering structures, the use of its network of real-time monitoring of the structural state, in order to ensure the safety of civil engineering structures and infrastructure, and effectively reduce maintenance costs. The second is the shape of adaptive materials and structures, the structure can not only carry the transfer of movement, but also detect and change the structural characteristics, has a broader application prospects. Third, adaptive control of vibration damping anti-seismic wind noise reduction structure, in civil engineering design structural dynamic response has been a relatively important issue, especially for bridges and high-rise buildings and other civil engineering structures seismic wind problems, research and development and application of smart materials can provide an important way to realize the adaptive control of the structure. Although the current smart materials still have different degrees of shortcomings, but with the continuous deepening of the relevant research, the performance of smart materials will be significantly improved. In many fields, smart materials will play its potential, reflecting the broad prospects for application, the research carried out, including mechanics, computer control, materials, microelectronics, artificial intelligence and other disciplines and technologies.

Fourth, conclusion

In summary, with the wide application of smart materials, while components gradually to miniaturization, multifunctionality and high power direction, in the building structure of the composite control, sensing, drive systems and coupling/connection components, the building structure will be developed into an active intelligent building structure, for the effective use of solar energy, to withstand the impact of earthquakes, wind vibration and other serious natural disasters have an important role, for people to work, and to provide a good opportunity to work, and to provide a good opportunity for people to work. It is important for the effective use of solar energy, against earthquakes, wind vibration and other serious natural disasters, providing a more comfortable and safe environment for people's work and life, and improving the quality of civil engineering structure construction is of great significance.

References:

[1] Zhang Yadong. Research on the application of intelligent materials in civil engineering [J]. Science and Technology Information, 2011(30):49.

[2]Huang Pu Shi. Research on smart materials in civil engineering construction[J]. Digital User, 2013(11):27.

[3]Wang Yang. Application of intelligent building materials in green ecological energy-saving buildings[J]. Foreign Building Materials Science and Technology, 2008, 29(2):123-126.

[4]Zheng Smart, Zhang Yongxing, Dong Qiang. Smart materials and their application in civil engineering [J]. Journal of Chongqing Institute of Transportation, 2005, 24(6):91-94.

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