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Raiser vs. Riser
Hopefully I've ended the edit war (however low in casualties) regarding stress raiser vs. stress riser. Both are commonly used terms, but the article should use the term "stress concentration" since that's the title. The other mention is regarding what they call it in orthopedics, and assuming it's right, then it should remain "raiser". - EndingPop 17:58, 14 February 2007 (UTC)
WikiProject class rating
This article was automatically assessed because at least one WikiProject had rated the article as stub, and the rating on other projects was brought up to Stub class. BetacommandBot 16:31, 10 November 2007 (UTC)
Under the 'Prevention' section, there's multiple references to '2a' without any explanation of what 'a' is. Going to the 'Fracture' page says that 'a' is "half the length of the crack", so '2a' is "the length of the crack" (assuming 'a' means the same thing on both pages). Of course, that's nonsense in this context - once the crack is whatever it's length is, it will keep growing. So much for a "critical value".
- .. once the crack is whatever it's length is, it will keep growing. That is not true. Most materials contain microscopic cracks that grow only when the applied stress reaches a certain critical value. Designs that consider this aspect of material behavior are called damage tolerant. Bbanerje (talk) 05:16, 27 July 2011 (UTC)
Truly speaking, all materials contain defects. These defects grow as soon as the material under consideration experiences some load (stress is force per unit area and is a tensor There are some good videos on youtube explaining what is stress and stress concentration ). When the stress is small, the growth is elastic i.e. it disappears when that load disappears. It has been shown that due to energy considerations these cracks mostly become elliptical (tending to become circular) in shape. Inglis was perhaps the first one to bring it to everyone's attention. Generally, the longer axis of the ellipse is labelled 2a and the shorter axis of the ellipse is labelled 2b.
If the load is not perpendicular to any of the two axes of the ellipse, the material shifts (due to shear) and cracks tend to align in what are called principal directions such that the major axis is along the direction of the load. If the load is perpendicular to any of the axes of the ellipse, the material tends to shift to make the direction of the load as the major axis of the final shape of the crack.
It can be proved that the ends of the axis which is perpendicular to the direction of the load experiences maximum stress. This is called the tip stress. Thus, every point on the surface of the crack does not experience the same stress. This tip stress divided by the the far field applied stress is called the stress concentration factor. Due to complicated nature of mathematics involving partial differential equations, it is not easy to find this tip stress. However, it is possible to simplify this problem for some practical applications by using what are called plane stress and plane strain conditions. It can be proved that under plane stress conditions the tip stress depends on the ratio of major axis to minor axis in the final configuration. And when the final shape becomes circular the stress concentration factor becomes three. The final configuration depends on many factors. I have placed two videos explaining this in detail on youtube. I will be happy to provide my views any time. The crack experiences permanent deformation (damage) when the tip stress crosses the yield point. Hence, the tip stress is what we have to worry about. 126.96.36.199 (talk) 15:30, 15 March 2013 (UTC)