Implementation of an open-die forging process for large hollow shafts for wind power plants with respect to an optimized microstructure
To realize large wind power plants in an economically feasible way, it is necessary to identify potential for lightweight design of the generator hollow-shafts, which are commonly produced by casting. The weight of these shafts can significantly be reduced by producing them by open-die forging, since the forming of the material leads to a higher strength, which allows to reduce the wall thickness noticeable. This paper describes the development and implementation of a forging process for hollow shafts with respect to an optimized microstructure. To numerically investigate this process, a realistic finite element simulation model was developed in a first step. The kinematic of the tools has been implemented authentically to provide a realistic material flow and process conditions. Additionally, a material model for the steel 42CrMo4 was integrated into the simulation model to predict the resulting microstructure. Using the implemented FE model, the forging process was optimized manually to achieve a homogeneous and fine-grained microstructure. The optimization was based upon a variation of different forging parameters and the sequence of forging steps. In the next step, a forging on laboratorial scale was performed to validate the simulation model. For this purpose, after forging, specimens from the hollow shaft were evaluated by metallography to determine the final grain size. A comparison of the results with the numerical simulation showed a general agreement of the measured grain size with the numerically calculated grain size. Based upon these results, the process model was transferred to an FE model with an industrial scale. By this it was possible to analyze the transferability of the used FE model regarding the assumptions about the kinematics and the sequence of the forging steps. A numerical investigation of the industrial process proved the scalability of the process to an industrial relevant geometry.
Study on deformation uniformity of mandrel forging process and control measures of inner hole eccentricity
Abstract The deformation uniformity and the control measures of the eccentricity of the inner hole in actual mandrel forging are researched by numerical simulation combined with experimental investigation. In one-step pressing, taking the width of the upper platform and the inverted cone angle of the large deformation area in one-step pressing as the characteristic parameters, the influence law of the pressing reduction of the anvil on the distribution of the mandrel forging deformation was obtained. In sequential overturned pressing, the influence of the 45° and 60° billet overturning schemes commonly used in the actual production on the deformation distribution and its uniformity was simulated. The result analysis shows that the deformation uniformity of the 45°overturning scheme is better than that of the 60°. The difference of the actual pressing reduction at each step in the overturning makes the angle of the large deformation area and the overturning angle in actual operation mismatch leads to the uneven deformation distribution. Based on the above research results, a kind of symmetrical overturning mandrel forging process is proposed to replace the existing sequential turning process, which greatly improved the deformation uniformity. Then, two kinds of hole eccentricity correction methods are put forward, which are stepped reduction mandrel forging combined with symmetrical overturning scheme (SO-Stepped Reduction) and changing the initial position in sequential overturning scheme (CIPSO-Stepped Reduction). Simulation analysis and experimental research show that the two kinds of hole eccentricity correction methods can effectively correct the hole eccentricity in the mandrel forging process. The methods of CIPSO-Stepped Reduction is easy to operate and more efficient.
Degradable polymers : principles and applications
1. Why Biodegradable Polymers? G. Scott. 2. An Overview of Biodegradable Polymers and Biodegradation of Polymers S.H. Huang. 3. Degradation and Stabilization of Carbon-Chain Polymers G. Scott. 4. Techniques and Methods of Polymer Degradation S. Karlsson, A.-C. Albertsson. 5. Biodegradation of Aliphatic Polyesters Suming Li, M. Vert. 6. Starch-Polymer Composites C. Bastioli. 7. Polymers from Renewable Sources E. Chiellini, et al. 8. Sustainable Poly(Hydroxyalkanoate) (PHA) Production G. Braunegg. 9. Polyhydroxyalkanoates: Properties and Modification for High Volume Application I. Chodak. 10. Biodegradable Polymers in Medicine E Piskin. 11. Environmentally Biodegradable Water-Soluble Polymers G. Swift. 12. Plastics and the Environment J. Guillet. 13. Degradable Hydrocarbon Polymers in Waste and Litter Control G. Scott, D.M. Wiles. Subject Index.