IMO

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Note added at 13 hrs (2014-08-19 23:40:08 GMT)
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http://en.wikipedia.org/wiki/Section_modulus
Section modulus is a geometric property for a given cross-section used in the design of beams or flexural members. Other geometric properties used in design include area for tension, radius of gyration for compression, and moment of inertia for stiffness. Any relationship between these properties is highly dependent on the shape in question. Equations for the section moduli of common shapes are given below. There are two types of section moduli, the elastic section modulus (S) and the plastic section modulus (Z).
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Profile section modulus of bending.
http://en.wxzhouxiang.com/products_detail/&productId=160.htm...
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115S. 159S. 245S. 273S. (mm ) Profile section modulus of bending. 6. 16. 30. 45. 100. 320. 500. (MPa) profile yield limit(MPa)
http://lgosix.bossgoo.com/section-bending-machine/vertical-p...
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To increase the section modulus of bending and torsion, it is known to equip the rotor with a continuous shaft for absorbing the drive forces
http://www.google.com/patents/US6416285
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Wrecking Bars, flat-oval. Special tool steel; forged; hardened; red powder coated; up to 50% higher section modulus of bending compared to equivalent hex
https://www.rennsteig.com/en/products/tools/striking-tools/w...
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= section modulus of bending mm3. Wg = effective section modulus of bending for a reduced branch mm3
http://www.scribd.com/doc/236426625/16/TBK-5-6-Norwegian-Pip...