i wanted to know about fatigue failure.?

Question

fatigue failure in mechanical components. can u tell a suitable site where i can get all the information?
animation,clips would be more ellaborative
thanks

Answer 1

In materials science, fatigue is the progressive, localised, and permanent structural damage that occurs when a material is subjected to cyclic or fluctuating strains at nominal stresses that have maximum values less than (often much less than) the static yield strength of the material. The resulting stress may be below the ultimate tensile stress, or even the yield stress of the material, yet still cause catastrophic failure.

A practical example of low-cycle fatigue would be the bending of a paperclip. A metal paperclip can be bent past its yield point (i.e., bent so it will stay bent) without breaking, but repeated bending in the same section of wire will cause the material to fail.

The following characteristics are common to fatigue in all materials:

The process starts with a microscopic crack, called the initiation site, which then widens with each subsequent movement, a phenomenon analysed in the topic of fracture mechanics.
Failure is essentially probabilistic. The number of cycles required for failure varies between homogeneous material samples. Analysis demands the techniques of survival analysis.
The greater the applied stress, the shorter the life.
Damage is cumulative. Materials do not recover when rested.
Fatigue life is influenced by a variety of factors, such as temperature and surface finish, in complicated ways.
Some materials (e.g., some steel and titanium alloys) exhibit an endurance limit or fatigue limit, a limit below which repeated stress does not induce failure, theoretically, for an infinite number of cycles of load. Most other non-ferrous metals (e.g., aluminium and copper alloys) exhibit no such limit and even small stresses will eventually cause failure.
As a means to gauge fatigue characteristics of non-ferrous and other alloys that do not exhibit an endurance limit, a fatigue strength is frequently determined, and this is typically the stress level at which a component will survive 107 loading cycles.
See the fatigue failure here:
http://en.wikipedia.org/wiki/Image:Classic_fatigued_axle.JPG
For indepth details please click:
http://en.wikipedia.org/wiki/Metal_fatigue

Answer 2

Try the following it may be of some value to you:

http://www.sv.vt.edu/classes/MSE2094_NoteBook/97ClassProj/anal/kelly/fatigue.html