ADM guidance-ceramics: Fatigue principles and testing

Fatigue of dental ceramics.

OBJECTIVES Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. DATA/SOURCES The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the denta...

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Fatigue Testing

Fatigue is the progressive, localized, permanent structural change that occurs in materials subjected to fluctuating stresses and strains that may result in cracks or fracture after a sufficient number of fluctuations. Fatigue fractures are caused by the simultaneous action of cyclic stress, tensile stress and plastic strain. If any one of these three is not present, fatigue cracking will not i...

Basic Principles of Homing Guidance

25­ INTRODUCTION The key objective of this article is to provide a broad conceptual foundation with respect to homing guidance but with sufficient depth to adequately support the articles that follow. During guidance analysis, it is typical to assume that the missile is on a near-collision course with the target. The implications of this and other assumptions are discussed in the first section,...

Electrically induced strain and polarization fatigue in lead-free ceramics

Piezoelectric ceramics have traditionally been used in commercial applications such as actuators and sensors. By far the most popular piezoceramics currently in use are Pb(Zr,Ti)O3-based (PZT) ceramics. PZT ceramics are able to produce large strain and polarization with the application of an electric field, and this is due to the Morphotropic phase boundary (MPB). A MPB is associated with the b...