Applied Mechanics and Materials Vols. 152-154

Abstract: The effect is discussed between operating parameters of District Heat Supply System and injector geometry by calculation. It is illustrated that heat supply load affects injector geometry worst, and suction fluid temperature has great impact on injector’s area ratio, while pressure loss of system offers no effects on diffuser geometry of injector.

Abstract: Resistance spot welding (RSW) is one of the most commonly used form of manufacturing process. To efficiently search for the optimal RSW parameters in a new welding power control scheme to obtain the maximum tensile strength of welded joints, a design of experiments (DoE) using orthogonal arrays has been conducted. However the lack of success of conventional DoE is attributed to two facts that the weld quality is quantitatively measured and level-based evaluated, and the welding expulsion compromises the continuity of response surface, which is an underlying hypothesis of normal DoE analysis. Hereby a fuzzy analysis methodology for the experimentation design, referred as fuzzy orthogonal experiments (FOE) in this paper, has been proposed. With the fuzzification of factor levels and experimental objectives, the proposed method is able to explore the results of arbitrarily given factors without additional experiments, and identifies the varying tendency under condition of discontinuity experimental responses. The FOE application for a specifically planned RSW process presents a detailed FOE analyzing procedures, and yields the optimal parameter settings. The case study shows that FOE outperforms the traditional orthogonal DoE for its minimized experiment numbers and robust response tendency analysis.

Abstract: Based on 3-TELEs(tele-controlling,tele-metering and tele-communication)Technology, a monitoring & controlling system for reservoir sluices group has been researched and developed in this project.With this embedded system, some real-time simulation data such as the rainfall, the water-level, the flow-level, the sluice opening and closing degree, as well as some equipment running condition data, are collected and analyzed to realize the 3-TELEs controlling, which means that the on-the-spot controlling, the base station controlling, and the remote center controlling can be achieved simultaneously at different place.

Abstract: This paper establishes the mathematical model of the piston ring’s wearing capacity for the marine diesel engine, studies the influence of the piston ring’s axial motion and radial motion to the magnetic field’s output signal, computes and analyzes the corresponding relationships of the magnetoresistive sensor’s output and the piston ring’s wearing capacity, and does the on-board experiment on the oil tanker with the 6RTA52U diesel engine. Measuring actually the magnetoresistive sensor’s output corresponding to the piston ring’s wearing capacity of the marine diesel engine confirms the correctness for the mathematical model of the wearing capacity. The research conclusions lay the technical foundation for the online monitor of the piston ring’s wear.

Abstract: To study the effect of a strong underwater shock wave on a concrete dam, in this research the hammers impact were applied to simulate the underwater shock in a model test. The model scale was 200 according to the gravity-elasticity similitude law. Five acceleration sensors were imbedded along the downstream surface of the dam. The maximum input pressure was evaluated based on the recorded accelerations. The explosive charge and the distance between the explosion center and the dam were determined corresponding to the maximum impact pressure. After the hammers impacted, the upstream face of the dam was fractured and downstream was scabbed; some cracks extended from the upstream face to the downstream face; the head of dam was projected; and the dam appeared entirely displacement. Although the damage similarity of the model and prototype is not verified, this method may be used to verify the quality of a protection project and offered evidence to define a protection project.

Abstract: A new mistuning form, pre-twist mistuning was found in the bladed disk based on the engineering practice. Based on a continuous parameter model of bladed disk, the characteristics of bladed disk with pre-twist mistuning and natural parameters mistuning, including stiffness mistuning, mass mistuning and damping mistuning were compared and analyzed, and the effect of pre-twist mistuning on the vibration response localization of bladed disk was researched. The result shows that pre-twist mistuning can lead vibration response localization to bladed disk as well as natural parameters mistuning. The degree of vibration response localization caused by force mistuning is comparative with the natural parameters mistuning. Compared with natural parameters mistuning, the pre-twist mistuning could not change the natural characteristics of bladed disk. As a result, the pre-twist mistuning can not be detected by traditional method, such as the frequency test. The result not only completed the research content of bladed disk, but also conducted the design and manufacture of bladed disk.

Abstract: A nonlinear spring-mass model is established to study the dynamic characteristics of nonlinear vibration isolator. By use of ADAMS software, the influence of stiffness, foundation displacement excitation and frequency of external excitation on the nonlinear vibration isolation systems are analyzed. Results indicate that the linear vibration system needs 4s to achieve stability, but the nonlinear vibration system only needs 0.1s. The response value increases with the increase of excitation frequency, the response pick value increases by 61.58% and 102.35% and each corresponding stable value increases by 159.35% and 309.87%.

Abstract: In order to validate the theory and select effective operational parameters in practical ice-breaking by air cushion vehicle (ACV), experimental study should be carried on firstly. The relationships of corresponding parameters between ACV model and prototype and between the ice-like material and the real ice are established on the basis of the similarity theory and the differential equation of thin elastic vibrating plate under static or moving load. According to geometric and dynamic similarity between model and prototype, for the conditions of different water depth, ice thickness, mass and velocity of ACV in actual operating mode, the pressure and velocity of ACV model, the elastic modulus and density of ice-like material in model test can be determined, the method of extending the model test results to prototype is proposed.

Abstract: A fully integrated micro electromagnetic vibration energy harvester based on MEMS technology is designed and its mechanical and electromagnetic characteristics are analyzed by using Finite Element method (FEM). Structure static, modal and harmonic analysis of spring-magnet system was carried out by ANSYS software. Ansoft Maxwell software was used to simulate the electromagnetic characteristics of the energy conversion system, especially the relationship between the output performances of the structure and parameters of the coil. The optimized model is designed and the optimization principles could provide a reference for the future electromagnetic vibration based harvester design.

Abstract: Whispered speech can be effectively used for quiet and private communications over mobile phones and is also the communication means for ENT patients under a regime of voice rest. However, little progress has been made on the denoising of whispered speech in noisy environment because of its special acoustic characteristics.In this paper, we propose a whisper denoising algorithm in joint time-frequency domain based on real-valued discrete Gabor transform(RDGT). Noisy whisper is first transformed into the joint time-frequency domain by fast real-valued discrete Gabor transform. The MMSE based log-amplitude estimator is derived under speech presence uncertainty hypothesis. Clean whisper spectral is then estimated by inverse transform of RDGT. Experimental results show that the proposed algorithm is very effective in avoiding the musical residual noise and retaining weak speech components.