Abstract: For improving fracture toughness as well as endowing with excellent self-crack-healing ability, mullite/SiC particles /SiC whiskers multi-composites were developed. Crack-healing ability and the mechanical properties of the specimens were investigated. Mullite/ 20 vol% SiC whiskers, mullite/ 25 vol% SiC whiskers and mullite/ 15 vol% SiC whiskers/ 10 vol% SiC particles composites can completely heal the pre-crack of 100 ım in surface length by heat-treatment at 1300 oC for 2 h in
air. However, not completeness of the strength recovery was caused for mullite/ 15 vol% SiC whiskers composite by crack-healing. In spite of the same SiC content, the crack-healing ability of mullite/ 15 vol% SiC whiskers/ 10 vol% SiC particles composite is superior to that of mullite/ 25 vol% SiC whiskers composite. Admixing with SiC whisker was effective for improvement in fracture toughness. Additionally, the fracture toughness was not reduced by admixing with SiC particles.
Abstract: The conductivity of metal-carbon-silicon nanocomposite films considered as potential
candidates for the application as wide-range temperature sensors for severe environmental conditions is studied. The films combine unique properties of amorphous carbons with a new functionality imparted by the presence of metal nanoclusters in host matrix. The deposition of carbon-silicon phase was performed using PECVD of siloxane vapors. Metals (W, Nb, and Cr) with concentration in the range from 12 to 40 at. % were incorporated in the carbon-silicon host matrix by DC magnetron co-sputtering. The conductivity of the films decreases with temperature in the range 80-400 K, being well described by the power-law dependence. The conductivity mechanism found satisfactory explanation in the framework of the model of inelastic tunneling of electrons between metal nanoclusters dispersed in carbon-silicon matrix. The parallel study of the influence of metal concentration increase on carbon phase microstructure was carried out using Raman spectroscopy.
Abstract: A new route to designing smart active composites, which deals with fiber-reinforced
in-plane anisotropic piezoelectric lamina and laminates, is proposed and its quantitative procedure formulated. Two examples of design are highlighted: unidirectionally active laminate and twist bimorph. Some progress in experimental work on the latter is briefly described.
Abstract: TbDyFe is a rare earth-iron magnetostrictive alloy with “giant” magnetostrain, good magnetomechanical coupling factor and fast response. Giant magnetostrictive actuators (GMAs) are designed and fabricated with home-made TbDyFe rods. Their magnetostrain properties under varied operation are tested. The static output displacement up to 100μm and output force up to 1500N were obtained. The dynamic displacement increases with amplitude under fixed frequency and decreases with frequency under fixed amplitude generally. The maximum dynamic output displacement of 146µm was obtained at natural frequency around 5Hz. Active vibration control employing GMA was implemented in the flexible structure. The excellent damping effect, 20-30 dB under the frequency range from 10Hz to 100Hz was obtained. The dynamic phase delay of GMA has been analyzed. A
novel improved FSLMS algorithm is proposed to achieve a better control performance.
Abstract: This paper demonstrates the ability of the Smart Spring to suppress helicopter blade
vibration through numerical simulation and experimental investigation. Mechanical shaker tests on a Bell-212 helicopter blade section verified the impedance control properties and the ability to suppress blade vibration using the Smart Spring proof-of-concept hardware. More importantly, the tests conducted in a wind tunnel proved the performance of the Smart Spring under highly varying unsteady excitation conditions. These tests confirmed that the Smart Spring system is able to actively suppress helicopter vibration through adaptive control of blade impedance properties.
Abstract: In this paper, a new method of combining computational mechanics and neural networks for prediction of composite beam delamination is proposed. One beam with delamination, as well as a ‘healthy’ beam with no delamination, had a four-ply symmetric carbon/epoxy composite design, were fabricated simultaneously. The delamination was assumed at different location of the beam, and then the finite element analysis was performed and the modal frequencies of the composite beam were obtained, which were used to train the neural network. The piezoelectric patch was attached to the top of the composite beam to measure its modal frequencies. A feedforward backpropagation neural network was designed, trained, and used to predict the delamination location using the experimental modal values as inputs. The experimental results demonstrate that the predicted delamination location and size error is small.
Abstract: A heuristic iterative learning control (ILC) design scheme is presented and is applied to the controller design of the active vibration control. A magnetostrictive material actuator is used as experimental equipment for active vibration control in this paper. The merit of the presented ILC scheme is that it is not necessary to build the mathematical model of the magnetostrictive actuator. The experimental result shows that the controller designed is efficient for active vibration control.
Abstract: In this paper, a new method which combines the least square method with Tree-Structured fuzzy inference system is presented to approximate the Preisach distribution function. Firstly, by devising the input sequence and measure the output, discrete Preisach measure can be identified by the use of the least squares method. Then, the Preisach function can be obtained with Tree-Structured fuzzy inference system without any special smoothing means. So, this new method is not sensitive to
noise, and is a universal approximator of the Preisach function. It collect the merit and overcome the deficiency of the existing methods.
Abstract: A six degree-of-freedom (DOF) Stewart platform is constructed, which consists of six TbDyFe alloy magnetostrictive actuators, and applied to active vibration control. To control the smart structure, a real time computer control system is built. An improved adaptive filtering algorithm is proposed in this paper, which is used for the computer control system. The results of experiments show that the smart structure and the proposed algorithm are efficient for active vibration control. More than 30 dB of vibration attenuation is achieved in real-time experiments.