66 research outputs found
Scale effects and crack propagation in non-linear elastic structures
New scaling laws are proposed for crack propagation in geometrically similar non-linear elastic structures. The stresses to cause cracking in large non-linear elastic structures are even smaller than those in larger linear structures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22190/1/0000621.pd
Defect-Structure-Related Ferroelectric Properties of K0.5Na0.5NbO3 Lead-Free Piezoelectric Ceramics
Lead-free piezoelectric ceramics K0.5Na0.5NbO3 (KNN) doped with Cu, Fe, and Ni have been prepared by a conventional ceramic process. The results reveal that Cu-doped KNN ceramic exhibits double-loop-like characteristics, while Fe & Ni-doped KNN ceramics show normal single loops. EPR spectra verified the formation of irreversible defect complex (DC1) and (DC2) in Cu-doped ceramics, while defect complexes were observed in Fe-doped ceramics and very small defect complex signal in Ni-doped ceramics. The experimental results show that the ferroelectric properties of KNN ceramics are strongly related to these defect structures
Influence of test parameters on the measurement of the essential work of fracture of zinc sheets
The Essential Work of Fracture (EWF) concept is used to characterize the fracture of thin plates of a zinc alloy. The consistency and applicability of the EWF approach are discussed. The successive stages of the fracture process were studied: the evolution of the shape of the crack tip was observed with a scanning electron microscope, the shape of the plastic zone and the evolution of necking in the ligament ahead of the crack tip were measured using a laser profilometer and the onset of cracking in the ligament was detected by means of a TV camera coupled with acoustic emission recording. The influence of both test parameters and material parameters on the Essential Work of Fracture (omega(e)) and on the CTOD (delta(c)) are elucidated. The effects of specimen geometry, deformation rate, texture and grain size are especially investigated. The main advantages and drawbacks of the EWF method are highlighted
- …