Research Of Small Punch Test To Obtain J_IC By Empirical Correlation And O-type Pre-cracked Sample Method

In this paper, fracture toughness tests and the small punch test were carried out on a large number of materials or the same materials with different directions. Empirical correlation of standard fracture toughness and equivalent fracture strain obtained by small punch test was researched. Furthermore, O-type pre-cracked small punch tests were performed on Q345R and A106steel at different temperatures.The main achievements are as follows:(1) The values of standard fracture toughness J0.2for35materials were calculated by means of standards GBT21143-2007and ASTM E1820-09combined with the J-resistance curve obtained by test. The results obtained by the two standards were compared.(2) A measure specification of minimum thickness of small punch specimen after fracture was established and the test method for equivalent fracture strain was founded and empirical correlation of equivalent fracture strain and standard fracture toughness were established.(3) O-type pre-cracked small punch test was introduced in this paper. The optimized diameter of round-notch was determined by linear elastic finite element analysis. Machining method for O-type sharp notch was developed to make sure the notch tip radius below10μm.(4) Calculation Method of stress intensity factor for O-type pre-cracked small punch test in low temperature was researched in this paper.