Evaluation of Dynamic Fracture Mechanics in the AISI316 Stainless Steel Using Instrumented Charpy Impact Testing

摘要

The dynamic fracture mechanics behavior of the AISI 316 stainless steel was studied by using instrumented Charpy impact testing. The dynamic fracture toughness (J_(1b)) could be evaluated by four different methods: Compliance Changing Rate, Stretching Zone, Energy Revised and Maximum Load Energy. The tests were made in temperatures -196 °C, room and 200 °C. At each temperature two specimens were tested. The total impact energy was 300 J and the impact velocity was 5.12 m/s. The Charpy specimens 10×10×50 mm were pre-cracked until 5 mm according to ASTM E-23. Stretching zone size was measured and analyzed by observing the fracture surfaces. They were obtained in a scanning electron microscope. Some times the blunting angle (θ) is assumed to 45°, but in this work it was the measured directly of stretching zone width. The range of θ?changed from 22 to 27°. The dynamic fracture toughness calculated among the three different methods showed a large difference. The compliance method showed less conservative. The values obtained by the revised energy were between the compliance and stretching zone methods. The AISI 316 stainless steel showed an extremely ductile behavior between -196 °C and 200 °C. All methods did not agree ASTM E1820 standard. In this work, plane strain was not occurred in the tip crack in the AISI 316.