Applied Mechanics and Materials Vols. 52-54

Abstract: Carbon fiber (CF) is an essential functional material focused on widely, especially in civil engineering. The mechano-electric character of carbon fiber layer based on the polymer-matrix and its sensing application to the pre-embedded crack detecting were experimentally discussed in this paper. Through the uniaxial tension the CF layer reveals a good performance by resistance changing with response to the loading. By three-points bending test, the crack of the structure would lead to an evident increasing of the resistance change ratio of CF layer. From the experimental results, the ratio of resistance increasing of CF layer laid on crack will be higher by 14.25% in average than that of CF layer with no crack laid. Thus carbon fiber mat composed with polymer will provides a new kind of potential sensor which can detect the defects of the structure.

Abstract: The design and safety evaluation of a geotechnical project is influenced by the shear strength parameters of geo-material. Moment method and linear regression method are the mainly used methods to estimate the shear strength parameters. But moment method is always over estimate the variation of strength parameters due to the smaller sample size, meanwhile the conventional linear regression method cannot obtain the standard deviation. Base on the reliability theory, a new method employing Solver add-in of spreadsheet was developed to calculate the shear strength parameters. The method was simplified by the principle that the shortest distance form origin point to the limit state surface in the normalization space was the reliability index. Four hundred and four samples of direct shear tests of rock mass from many large hydraulic projects in China were analyzed by four statistic methods including the new proposed one. Comparing results of different methods indicated that the new reliability statistic method had good performance than the traditional ways.

Abstract: Energy equivalent modulus medium of entrainment multiphase composite body is one of main methods, Those methods study frangible materials damage in micromechanics. Through studying the physical and mechanical process of microstructure varity, we can introduce some kind averaging method to find the material’s macroscopic property. It has not been studied as yet that we study entrainment composite body’s damage trough introducing continous field variable of every exponent tensor from macrophenomenology angle. This paper regards entrainment multiphase composite body as the micropolar medium of introducing inner structure. It provides analytic formula to describe equivalent modus of entrainment multiphase composite body damage, through the stress in micropolar theory of elasticity,couple-stresses tensor and Helmhoetz degrees of freedom density.

Abstract: Nanocrystallized ZrN coatings have been deposited by DC magnetron sputtering. The effects of target power on the microstructure and mechanical properties of ZrN coatings have been investigated. X-ray diffraction, scanning electron microscope and nano-indentation were applied to characterize the phase structure, morphologies of cross-section and mechanical properties of ZrN coatings. As power increases up to 250 W, ZrN coating exhibits (111) preferred orientation. All coatings showed columnar structure, and the columnar width increased with improved power. These microstructural changes resulted in the increase in hardness with increasing target power.

Abstract: The κ-Al2O3/TiCN multilayer coatings have been deposited on cemented carbide cutting tools using chemical vapor deposition (CVD). The morphology of the surface and cross-section were examined by scanning electron microscope (SEM). The adhesion force and scratch resistance of κ-Al2O3/TiCN coating were determined by CSM scratch tester. The results showed that the etching reagents and etching times had an evident influence on the morphology of the cross-section of κ-Al2O3/TiCN coating. The surface of κ-Al2O3/TiCN coating exhibited hexagon grain structure. The κ-Al2O3 layer showed columnar structure while the TiCN layer exhibited fibrous structure with long-needle grains. The results of scratch testing indicated that the -Al2O3/TiCN coating failed at coating/substrate and layer/layer interface by delaminating rather than by cracking or chipping due to long needle-like and columnar structure.

Abstract: Shape memory alloys have become the most promising construction material for smart actuators in diverse applications. However, their highly nonlinear hysteresis behaviour sets the main barriers in precise motion control. This paper presents an adaptive MKP control scheme based on a feed-forward compensator using the inverse of the modified KP model and the selective parameter adaptation law, to realize dynamic hysteresis compensation for real-time applications. The performance of the proposed control scheme was evaluated experimentally. The results indicate that such an improved adaptive control scheme is characterized by the reduced computation, rapid parameter convergence and effective hysteresis linearization.

Abstract: The objective of wireless location is to determine the mobile station (MS) location in a wireless cellular communications system. Due to the measurement with large errors, location schemes give poorer performance in non-line-of-sight (NLOS) environments. To determine MS location, Taylor-series algorithm (TSA) is commonly used scheme. TSA can give a least-square (LS) solution to a set of simultaneous linearized equations. The disadvantage of TSA is the need for an initial position guess to start the solution process. The iteration process may not converge due to a poor initial estimate of the MS location. To improve the location accuracy with less complexity, the initial MS location selection criterion is proposed. Numerical results demonstrate that the proposed criterion always provides more accurate positioning.

Abstract: Ranging is one of the most important processes in the uplink of the IEEE 802.16e OFDMA system. A ranging process includes the initial ranging, periodic ranging, handover ranging, and the contention bandwidth request. Initial ranging provides network entry, uplink synchronization, and system coordination. In the initial state of the transmission process, multiple users randomly transmit selected ranging code sets and BS identifies a specific user using the ranging code identification and uplink synchronization using the transmission delay estimation. In this paper, we discuss the details of the initial ranging and propose an algorithm to carry out a successful ranging process. The performance results and the comparison of computational complexity with the traditional method are also presented. It is noted the proposed algorithm can offer a better trade-off between computational complexity and performance.

Abstract: High dynamic property is a major object in fine stage design, as well as high stability. To raise structural damping is a feasible and effective method. In this paper, an approach is advanced by choosing parameters of structural damping for fine stage, via analysis of the loss factor of the structure. Through the experimental verification, this method could double the damping ratios, and be applicable to the same structures without changing the original interface.

Abstract: In this paper, a refined model of interlocked composite gird stiffened structure and an equivalent model based on simplified ICG panel are built. Buckling and dynamic response of the composite panel are then analyzed using the models. The result is the accuracy of buckling and mode analysis of refined model is greatly improved compared with the equivalent model. Simulation for impact response under different impactors is considered. The coefficients such as material properties and structure dimension of the slot are discussed.