This research project was motivated by the possibility of using fracture mechanics to assist in optimizing gear design. The primary goal is to develop a state-of-the-art capability for modeling three-dimensional crack propagation in gears using boundary element method, finite element method, and fracture mechanics. It is being conducted by a grant between Cornell University and the NASA-Glenn Research Center (formerly known as Lewis Research Center).
This is mainly applicable for short-lived devices where very large overloads may occur at low cycles. Typical examples include the elements of control systems in mechanical devices. A fatigue failure mostly begins at a local discontinuity and when the stress at the discontinuity exceeds elastic limit there is plastic strain. The cyclic plastic strain is responsible for crack propagation and fracture. Experiments have been carried out with reversed loading and
Chapter 1 is for readers who have less background in partial differential equations (PDEs).
It contains materials which will be useful in understanding some of the jargon related to the
rest of the chapters in this book. A discussion about the classification of the PDEs is
presented. Here, we outline the major analytical methods. Later in the chapter, we introduce
the most important numerical techniques, namely the finite difference method and finite
element method. In the last section we briefly introduce the level set method.
Many pavements, which are considered to be structurally sound after the
construction of an overlay, prematurely exhibit a cracking pattern similar to that
which existed in the underlying pavement. This propagation of an existing crack
pattern, from discontinuities in the old pavement, into and through a new overlay is
known as reflective cracking.
Reflective cracks destroy surface continuity, decrease structural strength, and allow
water to enter sublayers. Thus, the problems that weakened the old pavement are
extended up into the new overlay.
Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture.In modern materials science, fracture mechanics is an important tool in improving the mechanical performance of materials and components.