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AIRY STRESS FUNCTION FOR TWO DIMENSIONAL INCLUSION ...

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2<br />

2 2<br />

2<br />

⎛<br />

⎞ ⎛<br />

⎞<br />

4 ∂ 1 ∂ 1 ∂ ∂ 1 ∂ 1 ∂<br />

∇ φ = ⎜ 2 + + 2 2 ⎟ ⎜ 2 + + 2 2 ⎟ φ = 0.<br />

(2.1.8)<br />

⎝ ∂r<br />

r ∂r<br />

r ∂ θ ⎠ ⎝ ∂r<br />

r ∂r<br />

r ∂ θ ⎠<br />

The plane problem again is formulated in term of the Airy stress function,<br />

φ( r , θ)<br />

, with a single governing biharmonic equation as required.<br />

2.2 Complex Variable Methods<br />

A complex variable z is defined by two real variables x and y<br />

This definition can also be expressed in polar form by<br />

z = x + iy.<br />

(2.2.1)<br />

Figure 2-2 Complex Plane.<br />

z r i re i<br />

= (cosθ + sin θ)<br />

=<br />

2 2<br />

where r = x + y known as the modulus of z and<br />

θ =<br />

−1<br />

tan ( y / x) the argument<br />

9<br />

θ<br />

(2.2.2)<br />

z x iy re i − θ<br />

= − = . (2.2.3)<br />

z is the complex conjugate of the variable z

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