Research On Prediction Methods Of Fracture Toughness In The Ductile To Brittle Transition Region For 16MnDR Steel

Fracture toughness plays an important role in the structure integrity assessment of pressure vessels.The fracture toughness values of pressure vessel ferritic steels show significant scatter and strong temperature dependence in a distinct temperature region,called the ductile to brittle transition region.This makes it difficult to precisely describe the distribution of fracture toughness.Lots of researches and experiments have been done and some effective methods have been obtained abroad decades ago.However,the research about fracture toughness of pressure vessel ferritic steels in China starts later than other countries because of the lack of experimental data of Chinese steels.In this paper,the Chinese low temperature pressure vessel ferritic steel 16MnDR steel is studied and the data of tensile test,Charpy impact test and fracture toughness test are adopted to evaluate the methods that is used to estimate the fracture toughness of ferritic steels in the ductile to brittle transition region.The main contents and conclusions are as follow:?1?The Master Curve method is studied.Different reference temperature T₀ values are determined using both single-temperature and multi-temperature method.The influence of different numbers and combinations of test temperatures on T₀ is studied.?2?The applicability of some empirical formulas between Charpy V-notch impact energy and fracture toughness are discussed.Several methods used to calculate T₀ based on Charpy impact test data and empirical formulas'predicted results are studied.?3?Finite element simulations of fracture toughness test are conducted using SE?B?specimen model and the simulation results are compared with test data to confirm the validity of finite element analysis for 16MnDR steel.?4?A novel method that can effectively estimate the fracture toughness of 16MnDR steel in the transition region based on finite element analysis results and the Master Curve method is proposed.?5?The Beremin model's parameters of 16MnDR steel at-70?and-80?are calibrated by Minami method and the distributions of cumulative failure probability of fracture toughness at these temperatures are precisely predicted by Beremin model.