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.
RESEARCH ON THEORETICAL MODEL OF PRESS STRAIGHTENING PROCESS AND ITS EXPERIMENT
It is important to calculate straightening stroke precisely for automatic straightening machines. The rectangular section part is selected for study and is assumed to be the ideal elastic-plastic material. Based on the elastic-plastic mechanics theory, through deriving relationships among load, bending moment, deflection and elastic region length, the mathematical load-deflection model of press straightening process is established. An example is given. The results calculated by the model are in good agreement with the results computed by finite element method (FEM). Experimental data also shows that the calculation results by the model is exact and the error is small. So the validity and the accuracy of the model are verified. It will be helpful to the development of automatic straightening machines.
Control of reflective cracking
The first is 'fatigue' cracking of the layer. This type of cracking is the result of the application of loads on the pavement and is controlled by appropriate thickness design which 'ill not be discussed in detail here. Thickness design includes not only the design strength and thickness of the stabilised, but other design elements such as delaying reflection cracking, or limiting stresses in the stabilised layer, by adopting a minimum thickness of overlying material. This may include an unbound layer utilising the 'upside down' pavement approach. The actual thickness required of the overlying material varies but for example PIARC (Ref.1) recently reported when the thickness of coated materials exceeds 20 cm the emergence of shrinkage cracks at the surface is generally uncommon; when it is 15 cm thick, the cracks emerge at the surface, but do not shorten the life of the surface course, especially if they are sealed. This experience has been gained 'with legal axle loads of 130 kN, considerably greater than the Australian legal axle load.