What is the definiton of a crack?
What is the definiton of a crack?
(OP)
How do you define cracks in metallic structure? At what instance do you define crack initiation? Isn't it always a crack if you just magnify it enough?
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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What is the definiton of a crack?
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RE: What is the definiton of a crack?
-I define a crack as any location with a stress riser that has grown into the thickness of the part due to applied stresses at that point.
-I'd define crack initiation as the point where stress causes the as-fabricated defect/stress riser to significantly expand up (crack) beyond the initial geometry in the original part.
-Yes and no. Obviously there will always be microscopic defects and even a perfect re-entrant corner can open up into a crack due to stress risers. As the stress theoretically hit an asymptote at the tip of these stress risers you could argue that yes, there is always a crack. However, I would say that locations that have not significantly expanded from their initial conditions are not cracks; just defects or geometric stress risers.
In practicality, if it hasn't caused a significant loss of section I wouldn't really consider the part "cracked".
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: What is the definiton of a crack?
RE: What is the definiton of a crack?
Flaws larger than the minimum may be rejected out of hand or analyzed on a case by case basis, depending on the application.
RE: What is the definiton of a crack?
If your installation is critical, then you need to figure out what your critical crack size is (the longest crack that will sustain the largest load expected in service, which should be less than your maximum design load).
Now you can have a discussion about inspection methods ... visual ? NDI ? different methods detect different minimum size cracks; how critical is it ?
another day in paradise, or is paradise one day closer ?
RE: What is the definiton of a crack?
What impact does a crack have on the structure?
Crack propagation is usually only critical in dynamic structures. Does the crack grow in width? Length? What happens if the crack grows?
In general, a crack is defined as a visible anomaly. Yes, there are microcracks and sometimes they make a difference; however, in most cases we are only concerned about propagation and growth of cracks that eminate from a dynamic source. If it's visible, it's a crack!
RE: What is the definiton of a crack?
Presumably Schrodinger's Crack is in a superimposed state, until somebody observes it.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: What is the definiton of a crack?
RE: What is the definiton of a crack?
and like a "plumber's crack", once seen it can't be unseen.
another day in paradise, or is paradise one day closer ?