Search

Corroded cables from a cable-stayed bridge in China that had been in service for 18 years were employed to investigate the basic mechanical properties and residual fatigue life of wires and cables. First, the wires were randomly selected from the cables near the bottom anchorages and cut into segments as test specimens. The extent of corrosion of the wires was experimentally investigated. A tensile loading test was conducted on the wires to obtain the mechanical properties of the corroded single wires. The fatigue life of the corroded single wires was experimentally studied, and a dramatic degradation in fatigue life was observed. This phenomenon was interpreted using SEM images. Fatigue tests on two corroded cables were also conducted, and the test results indicated that the fatigue life of the cables had also decreased dramatically. A Monte Carlo simulation was conducted to obtain the fatigue life of cables. The simulation results indicated that the fatigue life of a cable was controlled by the small fraction of wires in the cable with the shortest fatigue lives. The fatigue life of a cable at a certain failure probability was dependent on the number of wires in the cable, but the mean fatigue life of a cable was not affected by the number of wires in the cable. DOI: 10.1061/(ASCE)BE.1943-5592.0000235. © 2012 American Society of Civil Engineers. CE Database subject headings: Cable-stayed bridges; Fatigue; Corrosion; Monte Carlo method; Simulation; Experimentation. Author keywords: Stay cable; Corrosion; Fatigue; Monte Carlo simulation.

Because the braking performance of automobile has close relationship to traffic safety, it is important to detect that. Focusing on the problem that the real time speed is difficult to obtain in detection process, soft sensing technique is introduced in this paper. According to analyzing the relationship of the dynamics equation of a moving automobile, a module of real time speed of braking is set up. By using imitation method with experiment data to get the pressure function of cylinder and analyzing the relationship between the trigging moment of a wheel and the pressure function of brake cylinder, the real time speed is confirmed in good precision. The maximal measurement error of real time speed is 8.7% and the precision can satisfy engineering request.

The effects of high magnetic field annealing on the preferred orientation distribution (texture) and magnetic anisotropy of arc-melted FePd alloy were studied by recalculated pole figure method and vibrating sample magnetometry. A rigorous texture characterization method was used to analyze the crystal orientation distribution of the annealed FePd. As compared with annealing without magnetic field, the high magnetic field annealing increases the volume fraction of crystal grains with c-axis aligned along the annealing magnetic field direction. A corresponding uniaxial magnetic anisotropy was also observed in the magnetically annealed FePd alloy.

This paper introduces a design method for polyvinylidene fluoride (PVDF) structural acoustic sensors for the active control of sound radiation into enclosures. It combines genetic algorithms and the quadratic optimal approach to search for a sensor configuration capable of detecting vibration components with strong sound-radiation ability. In this research, one PVDF sensor is not limited to one single piece of continuous PVDF film. It can consist of a cluster of small PVDF pieces, which could be discrete. Therefore, the parameters to be optimized are the number and the locations of PVDF pieces involved in a sensor. The design method is applied to a cylindrical shell with a floor partition. The general design guidelines are discussed. To show the effectiveness of the method, the control performance of an optimal sensor arrangement is compared with that of non-optimal ones. Physical insights are obtained using structural modal response analysis, modal spectrum analysis of the PVDF sensor output, and structural acoustical coupling analysis. The performance of a PVDF sensor configuration designed at one acoustic resonant frequency is also investigated for other disturbance frequencies below 500 Hz, showing that a significant reduction of acoustic potential energy can be achieved over a wide frequency range. It is demonstrated that, with PVDF sensors optimally designed using the proposed method, the active control of sound radiation into enclosures can be achieved without using acoustic transducers.

Genetic algorithms (GAs) are employed to optimize locations of PZT actuators in an active structural acoustic control (ASAC) system comprising a cylindrical shell with an internal floor partition. The effect of PZT actuators is simulated using a bending model and an in-plane force model, respectively. The characteristics of the optimal placements of both models are discussed and compared. Numerical simulations demonstrate that for the investigated structure, the in-plane force model has a better control performance than the bending model in the low-frequency range. The underlying physics of the control results are analyzed. Considering the practical applicability of optimally designed ASAC systems, the control performance of the optimal configuration obtained at a single frequency is assessed in the low-frequency range between 100 and 500 Hz, with results showing a significant sound attenuation in the whole range of interest.

In the present paper the structural acoustic coupling characteristics of a cylindrical shell with an internal floor partition are analyzed. Due to the existence of the floor, the cavity becomes irregular and both the structural and acoustic modes are difficult to express analytically. A method using “Radiation Efficiency Analysis of Structural Modes” is proposed. Typical configurations ranging from plain shells to shells with floor partitions are analyzed and, whenever possible, results are compared with those found in the literature. This method is shown to be effective when irregular-shaped cavities are involved. Meanwhile, analyses using wavenumber spectrum are also employed as an alternative. Results show that both methods have their own merit and both are very useful in the analysis of structural acoustic coupling systems, especially in the case of irregular cavities.

In the notebook and clamshell mobile phone, data communication wire often requires repeated bending. Generally, communication wire with the actual application conditions, the test data cannot assess bending resistance performance of data communication wire is tested conventionally using wires with weights of 90 degree to test bending number, this test method and device is not fully reflect the fatigue performance in high frequency and light load application condition, at the same time it has a large difference between the test data of the long-term reliability of high frequency and low load conditions. In this paper, high frequency light load fatigue testing machine based on the giant magnetostrictive material and stroke multiplier is put forward, in which internal reflux stroke multiplier is driven by giant magnetostrictive material to realize the rapid movement of light load. This fatigue testing device has the following advantages: (1) When the load is far less than the friction, reducing friction is very effective to improve the device performance. Because the body is symmetrical, the friction loss of radial does not exist in theory, so the stress situation of mechanism is good with high transmission efficiency and long service life. (2) The installation position of the output hydraulic cylinder, can be arranged conveniently as ordinary cylinder. (3) Reciprocating frequency, displacement and speed of high frequency movement can be programmed easily to change with higher position precision. (4)Hydraulic oil in this device is closed to transmit, which does not produce any environment pollution. The device has no hydraulic pump and tank, and less energy conversion processes, so it is with the trend of green manufacturing.

Active control of vibration and sound inside a structure-surrounded enclosure leads to many applications such as noise control inside vehicle cabins. Despite the extensive research carried out in the last two decades, ANVC technology is still in its infancy and has not yet been introduced massively in practical engineering applications. One of the problems to be resolved is that most of presently used techniques require the use of microphones inside the cavity, which is not practical in many situations. In addition, due to the coupling between the vibrating structure and the confined enclosure, demand for more robust control strategy is apparent. This paper tackles the aforementioned problem using a benchmark system in which only PVDF (Polymer polyvinylidene fluoride) sensors are used on the structural surface. A new method based on genetic algorithms is developed for sensor design. This design process ensures a proper consideration of the acoustic energy in the enclosure without the direct use of acoustic sensors inside the cavity. Roughly speaking, the sensor is designed to capture the most radiating motion of the structure via an automatic optimization process. In the proposed method, Genetic Algorithms and the least quadratic square optimal theory are organically combined together. For each configuration of error sensors, the amplitude of control forces, which can either be point forces or excitation generated by piezoceramic actuators, is first determined by minimizing the sum of the squared outputs of error sensors using the least quadratic square optimal theory. Then with the optimal amplitude of control forces, the acoustic potential energy of the sound cavity is computed and used as the evaluation criteria in the evolution process. Using Genetic Algorithms, the optimal configuration of the error sensors can be determined. A cylindrical shell with an internal floor partition is used as an example to illustrate the effectiveness of the proposed approach. To increase the computational efficiency, the structural surface is assumed to be covered with strip-typed PVDF sensors along both the circumferential and longitudinal directions. Both numerical and experimental results show the great effectiveness of the proposed GA-based design method. The sound reduction is achieved not only at the design frequency but also at most frequencies in the low frequency range. The proposed method demonstrates great merits in sensor design for complex structures.

Field experiment and numerical simulation are performed on a 33 kW horizontal axis wind turbine. The distribution of pressure is gathered by disposed 191 taped pressure sensors span-ward on seven particular sections of a blade. And the parameters of experimental condition of inflow and operation condition of the wind turbine are obtained at the same time. And then, the three-dimensional Reynolds averaged incompressible Navier-Stokes equations and the RNG κ-e turbulence model are used to study the aerodynamic characteristics of the wind turbine. The numerical method is proved to be more effective by contrasting the numerical results to the field experimental data. For the calculation results of the blade pressure, the closer to the root of the blade the more consistent to the values of the experiment. A greater differential is shown at the leading edge than the trailing edge. The pressure distribution contours of the blade surface are obtained too.