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while the associated shear stresses of this displacement field are
1
5 ( x 3 + ξ 3 ) 2
Q 2
3 C ( x 1 ξ 1 ) x 3
Q 5
3 C λ
λ + μ
( x 1 ξ 1 )( x 3 + ξ 3 )
Q 5
=−
τ 13
, (1.494)
1
5 ( x 3 + ξ 3 ) 2
Q 2
3 C ( x 2 ξ 2 ) x 3
Q 5
3 C λ
λ + μ
( x 2 ξ 2 )( x 3 + ξ 3 )
Q 5
τ 23
=−
, (1.495)
1
3 C ( x 1
ξ 1 )( x 2
ξ 2 )
5 x 3 ( x 3
+ ξ 3 )
Q 2
τ 12
=−
.
(1.496)
Q 5
The stress field generated by the Galerkin vector G 3 produces the traction per unit
area, on a small sphere of radius a surrounding the image point, with components
( x 3
+
,
+ ξ 3 ) 2
a 2
3 C x 1
ξ 1
a 4
3 x 3 ( x 3
+ ξ 3 )
a 2
1
3
F 1 =
+
(1.497)
λ +
( x 3
+
,
+ ξ 3 ) 2
a 2
3 C x 2
ξ 2
a 4
3 x 3 ( x 3
+ ξ 3 )
a 2
1
3
F 2 =
+
(1.498)
λ +
F 3 = 3 C x 3
( x 3
+
a 4
+ ξ 3 ) 2
a 2
+ ξ 3
a 4
+ 3 x 3 ( x 3
+ ξ 3 )
a 2
2
3
λ + μ
+ ξ 3
. (1.499)
The components of the total traction on the small sphere are found to be T 1
=
T 2
=
0and
a 2
0
π
T 3
=
F 3 sinθ d θ d φ
0
a 2 π
0
=
F 3 sinθ d θ
Ca 2 π
0
cos θ
a 3
cos 2
3 ( a cos θ ξ 3 )
a
=
θ +
cosθ
(1.500)
+
a 4 sinθ d θ
2
3
λ + μ
+ ξ 3
+
cos 2
cosθ π
0
a cos 3
6 π C
a
1
1
3
λ + μ
ξ 3
4 cos 4
=
θ +
θ +
θ
=
0.
For Kelvin's problem at the image point, the stresses are found from expres-
sions (1.321) and (1.322) for Kelvin's problem at the source point, by replacing
 
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