摘要：Dynamic fracture toughness of engineering materials at loading rates greater than 10 6 MPa m / s is widely investigated using the modified Hopkinson pressure bar apparatus. For accurate measurement of dynamic fracture toughness, it is essential to thoroughly understand the dynamic effects excited by the stress wave, such as stress wave propagation characteristics in bars/cracked specimen, the contact situation between the specimen and loading point or supports, and the dynamic response of the fracture specimen. In this work, full transient dynamic analysis techniques are used to comprehend “loss of contact” situation of cracked fracture specimen with an incident bar (impactor) and a transmission bar (supports) in a Hopkinson bar loaded two-bar/three-point bend test. A modified Hopkinson bar loaded experimental setup, including striker, incident, and transmission bars and three-point bend fracture specimen, is modeled using the commercial software ANSYS. The dynamic responses of the specimens made of titanium alloy, high-strength steel, and aluminum alloy are analyzed, and the specimen contact states with the incident and transmission bars are investigated using stress state contours of the specimen along with nodal displacement of the specimen and the bars. The dynamic fracture toughness values for the three specimens are also calculated and compared with the experimental results. The simulation results from the current two-bar/three-point bend test indicated that no “loss of contact” occurs during the first load duration as is previously proved experimentally.
关键词：Hopkinson pressure bar; two-bar/three-point bend test; “loss of contact”; stress state; finite element analysis
