Talk:Strain tensor

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[edit] Pure shear strain

The diagram at the start of this section needs to be updated so that the equation for tan(γ) is correct. At present the diagram shows a pure rotation of AB to AB' through an angle of γ and this means that

\tan(\gamma/2) = \frac{\overline{BB'}/2}{\overline{AB}}

but the equation is correct as it stands in the article, so the diagram cannot be correct.

The area Arh of the rhombus diagram is

A_{rh}=\overline{AB'}^2\times \sin(90-\gamma)

whereas the area of the orginal square Asq is

A_{sq}=\overline{AB}^2

The areas must be the same in order to give pure shear strain. This means that

\overline{AB}=\overline{AB'}

cannot be true (given pure shear strain).

Also, this page instantly assumes the use of the Cartesian coordinate system. General vector notation should be used at the start, and then, if we only want to show the Cartesian component derivations, make specific note of it.

in general, it should be eps = 1/2 ( grad u + transpose grad u). from there you can do your component derivations in whatever coordinate system desired, and it turns into dui/dxj if you go Cartesian. —Preceding unsigned comment added by 64.203.249.10 (talk) 00:47, 28 September 2007 (UTC)