Advanced Materials Research Vols. 622-623

Abstract: The tensile and low cycle fatigue tests were carried out on alumina short fibers reinforced Al-Si piston alloy composites (Al-Si MMCs). Three Al-Si MMCs reinforced with 10, 17 and 25 vol.% of alumina short fibers were prepared to investigate the effects of volume fraction on tensile and low cycle fatigue properties at room temperature (RT) and 350°C. The results showed that the tensile strength decreased with the increasing of volume fraction of fibers at RT and was slight different at 350°C. Among the three MMCs, the 17%-MMCs showed highest stress level under the low cycle fatigue tests. The fatigue cracks were usually initiated from the clustered and large size fibers near the surface of specimen, propagated along the fiber/matrix interface at RT and grew rapidly by means of broken the fibers at 350°C.

Abstract: In this paper, the phosphogypsum-based salic composite binder is the main study object, the particle size distribution, chemical composition and mineral composition of the components have been tested and analysed; According to the ratio experiments, a rational proportion range of the phosphogypsum-based Si-Al composite binder has been summarized; meanwhile, experiments have been designed for composite binder’s activity characterization by using the method of activity rate K_ª , and the extent which the K_ª value is affected by the external environment is Temperature > Curing time > Fineness; then scattered points on the dissolved quantity of active Al₂O₃、SiO₂ and the compressive strength at 90d is simulated by Matlab, and simulation results show that the compressive strength at 90d linearly increased with the increasing of dissolved quantity of active Al₂O₃、SiO₂.

Abstract: Micro-electromechanical switches (MEMS) with good performance in high frequency application such as linearity, no DC power consumption, no noise, small size and capability to co-fabrication on the chip today, it is noteworthy. the evolutionary approach in the design optimization of MEMS is a novel and promising research area. The problem is of a multi-objective nature; hence, multi-objective evolutionary algorithms (MOEA) are used. In this paper we introduced geometrical parameters of micro-electromechanical switch as input parameters or variables of multi-objective genetic algorithms then we compute electrical parameter of mems switch That show good performance and relation between theoretical parameter and simulated results is good.

Abstract: Smart materials such as piezoceramics used in industrial applications, are subjected to nonlinear phenomenon of hysteresis which degrades the tracking performance of the actuator in operation. Depending on the operating frequency and input magnitude applied to the piezoelectric actuators (PA), the symmetric and asymmetric hysteresis loops can be observed. A generalized inertial-dependent Prandtl-Ishlinskii (PI) model is proposed in term of the stop operator to compensate the effects of nonlinearity in asymmetric hysteresis loops for PA. A nonlinear envelope function is assigned for the threshold of the stop operator to minimize the error between the model response and the measured response obtained through the experiments at frequency range from 200 Hz to 500 Hz.

Abstract: Minimally invasive surgery (MIS) has had a major impact on modern day surgery, and has become the standard for various procedures. MIS however suffers from various impediments, and as a result, has seen robotic surgery gain rapid popularity. It is yet to be seen whether robotic surgery will cause another major paradigm shift, as these systems still require large costs, take up too much space, have an unclear cost benefit, and provide little or no force feedback. This paper presents a slave design for MIS, and a brief literature review on design requirements is given. A novel tool design for force/torque sensing is discussed, which uses an overcoat method to reduce measurement corruption at the trocar, and uses a single external 6-DOF f/t sensor.

Abstract: Robust Gain-Scheduling control based on Linear Parameter-Varying (LPV) system is researched in theory and applied to transient mode control of a morphing wing UAV (MUAV). H∞ output feedback control method is extended to the LPV system via parameterized LMIs. In application, LPV model of MUAV is established using the Jacobian linearization method, based on which an LPV controller is designed using the proposed method to control the attitudes of transient mode in morphing process, the problem of high frequency dynamics is found and solved by a robust pole constraint method. Monte-Carlo simulation is performed for 30 times, by which satisfactory performance and robustness of the LPV controller is revealed.

Abstract: Object size identification is very useful in building systems or applications especially in autonomous system navigation. Many recent works have started to use multiple vision sensors or cameras for different type of application such as 3D image constructions, occlusion detection and etc. Multiple cameras system has becoming more popular since cameras are now very cheap and easy to deploy and utilize. The proposed measurement system consists of object detection on the stereo images and blob extraction and distance and size calculation and object identification. The system also employs a fast algorithm so that the measurement can be done in real-time. The object measurement using stereo camera is better than object detection using a single camera that was proposed in many previous research works. It is much easier to calibrate and can produce a more accurate results.

Abstract: The ship electric field has become a new physical field which is widely concerned at home and abroad in recent years. For the research of ship electric field, one of the most effective methods is to measure it underwater. According to the analysis of ship electric field signal’s characteristics, the ship electric field measurement system based on MSP430F149 was designed and the key technologies of software and hardware were also presented in this paper. The results of experiment demonstrated that the system could effectively measure the ship electric field signal in a low SNR. Meanwhile, it has the advantages of low power consumption, high accuracy and credible.

Abstract: A two-dimensional (2D) vector sensor measures one acoustic pressure and two acoustic particle velocity components of the acoustic field. In this paper, a new approach is presented for localization of acoustic sources using an array of 2D vector sensors. A simple algorithm for estimating the source location with this array is presented along with their statistical performance analysis. The simulation experiment is presented to verify the efficacy of the proposed localization method and simultaneously analyzing the factors which affects the accuracy of localization.

Abstract: SHM is defined as “an emerging technology that can be defined as continuous, autonomous, real time, in-service monitoring of the physical condition of a structure by means of embedded or attached sensors with minimum manual intervention” .SHM provides the ability of a system to detect adverse changes within a system’s structure to enhance reliability and reduce maintenance costs. There are different Non-Destructive techniques like acoustic emission, ultrasonic, acousto-ultrasonic, guided ultrasonic waves or Lamb waves which are nowadays investigated for the development of an efficient and user-friendly damage identification system. This paper deals with the latter which is based on Lamb wave propagation. It has been developed especially for distinguishing different kinds of damages. The Lamb wave-based active SHM method uses piezoelectric (PZT) sensors to transmit and receive Lamb waves in a thin Aluminum plate. The Lamb wave modes (AO &SO) travel into the structure and are reflected by the structural boundaries, discontinuities, and damage. By studying their propagation and reflection, the presence of defect in the structure is determined. Laboratory level experiments have been carried out on thin Aluminum plates with angular, horizontal and vertical defect. The obtained waveform is filtered to avoid unwanted noise & disturbances using Savitzky-Golay filtering. The filtered waveforms are compared to differentiate the defects. Short Time Fourier Transform has been carried out on the acquired waveform. This study provides significant insight into the problem of identifying localized damages in the structure using PZT and dispersion of signal after they interact with different types of damage. Those small defects like the horizontal one that may be nearly missed in time domain analysis can also be clearly identified in the STFT analysis. Moreover the occurrence of So mode is also clearly seen. Thus, Lamb waves generated by PZT sensors and time-frequency analysis techniques could be used effectively for damage detection in aluminum plate. This study has given a complete idea of the working and the basic requirements of SHM system.