Investigation of Crack Tip Stress and Strain Fields at Crack Initiation of A106 Gr. B Carbon Steels under High Strain Rates

Abstract This paper analyzes crack tip stress and strain fields at crack initiation under high strain rates. In the range of high strain rates, the mechanical behavior of a material is characterized by an increased in strain rate sensitivity. However, due to geometry and constraint of various test specimen, it is difficult to quantify strain rate on the at constant test speed. To quantify the strain rate, we simulate crack tip stress and strain fields using three-dimensional finite element model. Our analysis models are fracture toughness (CT) specimen and full scale circumferential cracked pipe component. Dynamic material properties used in the finite element analysis are based on Pipe Fracture Encyclopedia. Pipe Fracture Encyclopedia provides strain rate dependent tensile test, fracture toughness test and full-scale four point bending test. All experiments were tested at 288 °C and test specimens were extracted from A106 Gr, B carbon steel pipes. Three different strain rate tensile test (4 x 10 -4 /s, 3.4/s and 11.6/s) are fitted using Johnson-Cook model. Our results show that, applied strain rate and strain rate at characteristic length have similar values as in the CT specimen simulation result. Similar outcomes were shown in the pipe simulation result.