Search

This article presents the development of an acoustic energy harvester using a quarter-wavelength resonator phononic crystals together with piezoelectric vibrators. The quarter-wavelength resonator phononic crystals consist of a main wave duct, several quarter-wavelength resonators, and equivalent piezoelectric vibrators. The acoustic energy is converted to mechanical energy when the sound incident in the quarter-wavelength resonator generates an oscillatory pressure as of localization efficiency, which in turns causes piezoelectric vibrators vibrating. Transfer matrix method is used to provide a physical insight into the structure band of the quarter-wavelength resonator phononic crystals, and finite element method is used to analyze the sound localization effect and evaluate the reclaimed energy of the quarter-wavelength resonator phononic crystals. Results indicate that the numerical analysis agrees well with experiments. When the frequencies of the incident sound are near both sides of the bandgap, the maximum output voltage always can be obtained.

The service life of a gear-type oil pump with variable displacement is affected by the reliability of its drive system. To analyse the reliability of the drive system and improve the service life of the oil pump, a virtual prototype model was established based on real conditions and multi-body dynamic theory. The model was validated according to bench test results. And simulation results were in good agreement with test results. A numerical method was used to simulate the dynamics model and the dynamic meshing forces of gear pairs were obtained. A reliability evaluation model of the drive system was built. The reliability of each part and the entire drive system were calculated. And system reliability was analysed and discussed when 45 steel or 40Cr was utilised as the material for the drive system. The results provided a foundation for the reliability design and the dynamic optimisation of a gear-type oil pump with variable displacement.

This article introduces the basic theory of modal analysis. The modal testing system is established for a developing truck body. Using a pseudo-random excitation signal along the x, y, and z directions, the modal test is carried out to obtain the dynamic performance by multi-point excitations. The transfer function set is obtained by averaging all transfer functions, and the set is processed by order selection to get 28 order modes. Fitting modal parameters and normalizing modal mass can gain natural frequencies and vibration modes of cab. Then, the modal analysis of truck cab is calculated based on the finite element method, and the results are compared with the test results. The improved measures are put forward to enhance the local stiffness, avoid modal coupling, and reduce vibration noise. So, this article supplies a reference for the dynamic test for the large body.

A procedure for sound filed simulation, sound quality (SQ) evaluation, and optimization of interior noise of a rail vehicle is investigated in this paper. Firstly, some interior noises are measured on site when the subway is running in tunnel at a speed of 60 km/h. The sound pressure levels (SPLs), loudness, sharpness, and roughness of the measured noise are analyzed. A finite element model for acoustical simulation of the carriage is established by using the Actran software. The accuracy and feasibility of the finite model are verified by comparing the psychoacoustical parameters from the simulations and measurements. By using orthogonal experimental design, finally, the best optimization scheme is put forward, which obtained a sound quality improvement with a 4.81 dB decrease in SPL and a 1.07 sone reduction in loudness. The proposed optimization scheme may be extended to other vehicles for improving interior acoustic environment.

Assembly dimensional quality affects wind noise and driving steady and whole external appearance. The quality can be improved by reducing part tolerance and fixture tolerance and optimizing key control characteristics (KCCs). However, reducing tolerance should largely increase manufacturing costs, and then the paper assembly tolerance is decreased by selecting optimal KCCs. In this work, a fitness function is presented to evaluate assembly operations based on the linear assembly variation analysis model. Afterwards, a new social radiation algorithm (SRA) is proposed to optimize KCCs, and some test functions are used to evaluate optimum performance between the genetic algorithm (GA) and SRA, and the results show that the performance of SRA is better than that of GA. Finally two cases are used to illustrate process of assembly operation optimization by SRA, and the results show that the SRA has higher precision and efficiency than that of GA.