Hot Workability Studies of Nimonic 80A Applied to the Net-Shape Forging of Aerofoil Blades
Real material based physical-simulation experiments are carried out on Nimonic 80A samples with the aim of investigating the workability exhibited by the material under the process conditions that occur during multi-step hot forging of a gas turbine blade
- PDF / 916,832 Bytes
- 6 Pages / 481.89 x 691.654 pts Page_size
- 60 Downloads / 162 Views
P.F. Bariani, T. Dal Negro and M. Fioretti University of Padua, Padua, ltaly
KEY WORDS :
Hot Forging , Turbine Blades, Nimonic 80A, Workab ility
ABSTRACT: Real material based physical-simulation experiments are carried out on Nimonic 80A samples with the aim of investigating the workability exhibited by the material under the process conditions that occur during multi-step hot forging of a gas turbine blade. On the basis of workability data, expressed in terms of rheological behaviour, sensitivity of the flow strength to temperature and strain rate variations during deformation and final microstructure, opportunities for redesign and optimisation of process parameters are analysed.
1.
INTRO DUCTI ON
Modelli ng the forging of turbine blades can be approac hed in differen t and complem entary ways, accordin g to the particula r aim of the analysis. Analytic al methods , such as slab method and slip-line theory, prove tobe effective in predictin g Ioads, optimum die profile, preform position and minimu m stock volume for complet e filling of cavities in the aerofoil region of the turbine [1,2]. Physica l simulati on techniques based on soft model material s deforme d by using cheap tools have been extensiv ely applied to investig ate both 2D and 3D flow pattems [3-5]. In the most sophisticated applications, these techniqu es enable forging Ioads and pressure distribution at interfac estobe evaluate d as well [6]. Exclusiv e capabili ty of the Finite Elemen t method is the coupled thermal and mechani cal analysis of forging operatio ns with quantifi cation of local values of strain, strain rate, stress and temperature in the whole volume of the workpie ce and dies [7 -9]. Nett-sha pe forging of Nickel-a lloy turbine blades is a complex operatio n to model. Due to the high sensitiv ity of the flow strength of the material to tempera ture and, for some alloys, Published in: E. Kuljanic (Ed.) Advanced Manufacturing Systemsa nd Technolog y, CISM Coursesa nd Leeeures No. 406, Springer Verlag, Wien New York, 1999.
324
P.F. Bariani, T. Da! Negro and M. Fioretti
to strain rate and the thin section in the aerofoil region, filling of the die cavtties is dominated by the response of the material to the straining and temperature histories that are determined by the geometry, heat transfer and friction at the material-workpiece interface. Accordingly, knowledge of the instantaneous response of the material to the thermal and mechanical cycles is a prerequisite to accurate modeHing and effective design of the forging process. To this aim, physical-simulation experiments have been set up by the authors [10-12] where the thermal and mechanical events of the forging process are reproduced on realmaterial samples. This paper refers to the application of the above physical simulation experiments to Nimonic 80A samples with the aim of investigating the workability exhibited by the material under the process conditions that occur during multi-step forging of a gas turbine blade. On the basis of workability data, expressed in terms
Data Loading...
