| Railway tank car is the main equipment of railway transportation for concentrated nitric acid. Xi’an Railway Vehicles Equipment Co., Ltd. is designing70t concentrated nitric acid tank car based on previous60t tank car to meet the increasing demand for concentrated nitric acid. Al/Al-Mg alloy laminated plate material was chosen to applied for tank body considering the requirements of anti-corrosion and force bearing. Aluminum is the inner material which will produce a firm oxide layer with concentrated nitric acid to protect Al-Mg alloy; high strength Al-Mg alloy is the load bearing material to ensure the structure strength of tank body. However, butt joint filler material of the laminated plate can only adopt Al-Mg alloy which will make a small amount of filler material exposed in concentrated nitric acid. Therefore, an aluminum plate was overlapped on the butt joint to protect the weld.This paper research on fatigue performance of the laminated plate and evaluate of the lifetime of the tank body based on load spectrum on universal lines of our country. At first, fatigue tests were taken for above laminated plate specimens, its butt weld specimens and lap weld specimens to establish S-N curves. Then, elastic-plastic analysis for basic material specimens were taken to verify tensile test results and get basic mechanic data. Then, finite element analysis of tank car under different working conditions was taken to get load-stress transfer coefficients of different key points. Eventually, use Miner linear cumulative damage rule based on C70general railway line load spectrum to evaluate lifetime of tank body to validate its fatigue reliability.In conclusion, in this paper, S-N curves of the three kinds of specimens were established, and stress distribution and load spectrum of tank car under different working conditions were obtained. Based on above results, lifetime of dangerous point of basic material of tank body is2.52x106kilometers and lifetime of dangerous point of weld joint is1.33×108kilometers, which is bigger than the designed lifetime2.5×106kilometers. The results show that the strength of the tank body using Al-Mg alloy laminated plate is consistent with the requirement. Some related positions are suggested to give appropriate optimization and strictly control welding quality based on the results of the fatigue life. |
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