The Forming Die Design and Experimental Research of CFETR Vacuum Vessel Shells
Vacuum vessel (VV) is the main component of the China fusion engineering test reactor. Shell forming is relatively in the earliest phase, one of the most important processes during VV manufacturing. The profile errors caused by spring back of shells at room temperature will directly influence the subsequent manufacturing and experimental studies, so a set of dies, whose profiles can be easily revised, has been designed based on the spring-back theory. The empirical formula has been used to calculate the theoretic die profile value, which is mostly determined by the mechanical properties of 316LN stainless steel. Then, choosing four relevant values to simulate the forming process in which the optimal profile errors of shell must be controlled within 1.5 mm. The optimal dimensional value of the dies has been confirmed to guide the forming experimental study. After the experiment, the actual profile errors, thickness reduction, maximum spring back, maximum deformation rate, and the surface residual stress have been measured, and those data are an accurate indicator from the finite element analysis, also verifying the reasonability of the manufacturing process in turn.
R&D of Full-Scale Partial Vacuum Vessel Mockup for Future Fusion Engineering Test Reactor in China
As a representative part of the vacuum vessel based on future fusion engineering test reactor in China, lower segment named PS4 is chosen to demonstrate the fabrication feasibility with full scale for the purpose of cost saving. PS4 mockup has double-walled structure and full penetration is required for welding. All fabrication processes are involved, and the main interests of this paper are focused on forming precision, UT usability for austenite stainless steel 304L, distortion control technology and fabrication route reasonability. The fabrication refers to nuclear code of RCC-MR 2007 and domestic standards including GB/T 19418-2003 and JB/T 4730-2005. This paper presents the R&D processes and results.
Microstructure of the solder-casting zone in bridges of dental gold alloys.
The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.