Dynamic three point bending test is one of the general methods to test the dynamic fracture characteristics of materials. However, it is generally hard to measure the dynamic load generated by interaction of two bodies. In order to make it easier in the test, many impact methods, such as the one using a rod-impactor to measure the dynamic load from its response and that using the electro-magnetic force instead of the impactor loading, have been proposed.
In addition, the evaluation of the dynamic fracture mechanics parameter is also difficult. Many researchers are using the static calibration between the load and KI value. However, it has been also reported that the load doesn't have good correlation to the dynamic stress intensity factor. Therefore, a detailed simulation is necessary to evaluate the methods of obtaining the dynamic stress intensity factor.
In this study, the finite element analysis of dynamic three point bending test using a rod-impactor, by which the dynamic load can be measured easily, was made with consideration of the contact-separate behavior and frictional effect at the loading and support points. The stress intensity factors evaluated by several methods were compared. The following results were obtained.
(1) KI values calculated by the static load-KI relation had a larger oscillation than those by other methods. In addition, the non-zero frictional coefficient caused the reductions in displacement, CODmouth and J-integral, but did not affect the load. From these points, the method using the static load-KI relation is not appropriate for this case.
(2) As the ratio of the span to the width of the specimen (S/W) became smaller, the oscillation of the time history of KI value and the separation between the specimen and the support became less.
(3) The lower modes of vibration were dominant in the response of the specimen in spite of impact loading.