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| Research on Multi-Step Hot Forming Process of TB8 Titanium Alloy Leading Edge Skin of Complex Shape Blade |
| SHI Wenxiang1 , ZHANG Wenliang2 , CHEN Minghe1 , XIE Lansheng1 , WANG Ning1 |
| (1. College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics， Nanjing 210016, China; 2. AVIC Xi’an Aircraft Industry Group Company Ltd., Xi’an 710089, China) |
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Abstract A certain type of hovercraft with complex curved blades has a special-shaped cross section at the leading edge skin. The torsion angle of the front and rear ends is so large that it’s difficult to form by one step. In order to achieve its accurate forming, a multi-step hot forming experiment is required. To obtain suitable experimental parameters, the material forming performance and part forming scheme were studied through high-temperature tension, stress relaxation experiments and finite element simulation. The results of experiments and finite element analysis show that the high temperature plasticity and stress relaxation of TB8 during hot forming can effectively avoid crack failure and suppress springback. Through multi-step hot forming, it is possible to achieve precise forming of 88.7° large twisted skin parts. After comparing with the deformation and springback distribution of the parts at different temperatures and stamping speed of the high-temperature ridge pre-bending, tip-bending and tail-bending, the optimized patameters are obtained that the forming temperature is 675℃ , the stamping speed is 30mm/min, and the maximum thinning of the skin parts during pre-bending is 0.92%. Based on the stress distribution of the parts in each forming step obtained by simulation, the stress relaxation time is determined according to the results of the stress relaxation experiment. The ridge pre-bending stress relaxation time is 15min, and the spring-back angle of the part is less than 3.5°. The high-temperature tip-bending and tail-bending after 10min stress relaxation, the average springback of the part is less than 0.5mm. The multi-step thermoforming has been used to produce the skin of complex-shaped blade leading edge, which can be accurately assembled with the blade.
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2021, 
