Shi Dong-yan

Propagation of torsional waves in a thin circular plate of generalized phononic crystals

By introducing periodicity in the direction of variable vectors, the concept of existing phononic crystals (PCs) is expanded to generalized phononic crystals (GPCs), and a one-dimensional thin circular plate of GPCs (GPC plate) consisting of two alternating homogeneous materials is constructed. To show the characteristics of a torsional stress wave propagating along the radial direction, a transfer matrix is derived based on the basic torsional wave equation of the thin circular plate in cylindrical coordinates. A localization factor is introduced to evaluate the average attenuation of torsional stress waves in the structure, thus the band gaps are calculated. The inherent relationships between wave attenuation band, wave front and periodicity are discussed in detail. Finite element method simulations, numerical analyses and the insertion loss method are combined to investigate the effects of the main parameters on the torsional stress wave band in GPC plate. The results show that there are significant band gaps of the torsional stress waves caused by the periodicity of GPC plate, which are similar to those of existing PCs, and the localization factor can be used for the wave analysis of GPCs. In addition, structural and material parameters have a great influence on the wave attenuation band of the GPC plate.

Clustering and group selection of interim product in shipbuilding

Cellular manufacturing of the interim products based on group technology (GT) is a useful way to increase the productivity and improving the process flows of shipbuilding. In this paper, we analyze the similarity relationship on interim product to form product families and establish requirement mode of similarity measurement based on shipbuilding GT. The classifier of ART2 artificial neural network is proposed on the basis of the adaptive resonance theory. It can classify and identify automatically the input data through analyzing the characteristics of interim product in shipbuilding. With the modified algorithm, the interim product can easily and efficiently be formed product families and controlled to group related interim product into families in reason by similar coefficient. Meanwhile, through analyzing the production constraint to form assembly cell, the set of evaluating indexes is founded whose weights are decided by the entropy weight method and the comprehensive assessment values of product families design schemes can be computed to judge the final optimization scheme through the grey correlation analysis. The formation of sub-assembly interim product family in a bulk carrier is taken as an example to verify the proposed method, and the results show that it is an effective method for solving the group manufacturing problem in shipbuilding activities.

Key technology of ship product data exchange based on STEP

In this paper, in order to implement the share and exchange of the ship product data, a new kind of global function model is established. By researching on the development and trend of the application of ship STEP (standard for the exchange of product model data) standards, the AIM (application interpreted model) of AP216 is developed and improved as an example, aiming at the characteristics and practical engineering of ship industry in our country. The data exchange interfaces are formed based on STEP in the CAD/CAM for the ship by all function modules and shared databases under the global function model. The share and exchange of all information and data are solved in the design, manufacture and all life-cycle of ship products among different computer application systems. The research work makes foundation for the ship industry informatization.

Application of neural network method to process planning in ship pipe machining

Based on artificial neural network for process planning decision in ship pipe manufacturing, a novel method is established by analyzing process characteristics of the ship pipe machining. The process knowledge of pipe machining is shifted from the expression of the external rules to the description of the internal net weight value in order for the net inferring engine to decide the process route of pipe machining rapidly and rightly. Simulation shows that the method can resolve problems of process decision, and overcome the drawbacks of “matching difficulty” and “combination explosion” in traditional intelligent CAPP based on symbol reasoning.