Abstract

From results of literature, it can be concluded that the R-curve of soft piezoelectric ceramics strongly depends on the type of test. In three-point bending tests and measurements with compact tension specimens a pronounced R-curve is found, whereas tests with opposite roller loading show a more flat crack resistance curve. Two possible reasons for this effect are differences in the domain switching state and bridging interactions in the crack wake. Both effects are discussed in terms of fracture mechanics. From the considerations it can be concluded that the dominating effect is the test-dependent change of the orientation state in the crack wake.