Comparison of online identification methods of material parameters in press straightening process
More and more automatic pressure straighteners are used on the manufacturing industry because of their high productivity and good quality. When the technologic parameters are calculated, the precision of results will be influenced by the part's material performance parameters. In this paper, three online identification methods of performance parameters were studied. They were BP neural network method, RBF neural network method and the support vector machine method. Then their identification effects were compared. It was shown that all three methods can be used to identify material performance parameters in straightening process. But later two methods have better identification precision and shorter response time than BP neural network method.
Study on Calculation Method of Press Straightening Stroke Based on Straightening Process Model
It is difficult to determine straightening stroke precisely for automatic straightening machines. The existing calculation method of straightening stroke is based on straightening curvature equation. Because the initial curvature is obtained by curve fitting method, the method is inconvenient to use and its accuracy is not well. In this paper, a method to calculate straightening stroke based on straightening process model is put forward. So the mathematic load-deflection model of straightening process must be established at first. The straightening process model for shafts is developed according to the elastic-plastic mechanics theory. By using the model, the straightening stroke can be calculated directly according to the initial deflection of the bent part. It is advantageous to use and to decrease errors. Comparing with FEM results and experimental results, the calculation results by the model are exact and the errors are small. So the validity and the accuracy of the method are verified. It will be helpful to the development of automatic straightening machines.
Normed units in abelian group rings
We compute explicitly the isomorphic structure of the normalized unit group of an abelian group ring under some minimal natural restrictions on the group basis and the coefficient ring. This enlarges affirmations due to Chatzidakis-Pappas (J. London Math. Soc., 1991) and Mollov (Publ. Math. Debrecen, 1971).