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Lai et al, Introduction to Continuum Mechanics
CHAPTER 2, PART A
2.1 Given
1 0 2 1
Sij 0 1 2 and a
i 2
3 0 3 3
Evaluate (a) Sii , (b) Sij Sij , (c) S ji S ji , (d) S jk Skj (e) amam , (f) Smn aman , (g) Snmaman
Ans. (a) Sii S11 S22 S33 1 1 3 5 .
(b) Sij Sij S 2 S 2 S2 S2 S2 S2 S2 S2 S2
11 12 13 21 22 23 31 32 33
1 0 4 0 1 4 9 0 9 28 .
(c) S ji S ji = Sij Sij =28.
(d) S jk Skj S1k Sk1 S2k Sk 2 S3k Sk 3
S11S11 S12 S21 S13S31 S21S12 S22 S22 S23S32 S31S13 S32 S23 S33S33
1 1 0 0 2 3 0 0 1 1 2 0 3 2
0 2 3 3 23 .
(e) amam a12 a2 2 3a2 1 4 9 14 .
(f) Smn aman S1na1an S2na2an S3na3an
S11a1a1 S12a1a2 S13a1a3 S21a2a1 S22a2a2 S23a2a3 S31a3a1 S32a3a2 S33a3a3
1 1 1 0 1 2 2 1 3 0 2 1 1 2 2
2 2 3 3 3 1
0 3 2 3 3 3 1 0 6 0 4 12 9 0 27 59.
(g) Snmaman = Smn aman =59.
2.2 Determine which of these equations have an identical meaning with a Q a' .
i ij j
(a) a Q a' , (b) a Q a' , (c) a' Q .
a
p pm m p qp q m n mn
Ans. (a) and (c)
2.3 Given the following matrices
1 2 3 0
ai 0 , Bij 0 5 1
2 0 21
Demonstrate the equivalence of the subscripted equations and corresponding matrix equations in
the following two problems. T
(a) b B a and b B a , and s a B a
(b) s B a a
i ij j ij i j
Ans. (a)
bi Bija j b1 B1 ja j B11a1 B12a2 B13a3 2 1 3 0 0 2 2
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b2 B2 ja j B21a1 B22a2 B23a3 2, b3 B3 ja j B31a1 B32a2 B33a3 2.
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Lai et al, Introduction to Continuum Mechanics
2 3 0 1 2
b B a 0 5 1 0 2 . Thus, bi Bija j gives the same results as b
B a
0 2 2
(b) 1
2
s Bij aia j B11a1a1 B12a1a2 B13a1a3 B21a2a1 B22a2a2 B23a2a3
B31a3a1 B32a3a2 B33a3a3 2 (1)(1) 3 (1)(0) 0 (1)(2) 0 (0)(1)
5 (0)(0) 1 (0)(2) 0 (2)(1) 2 (2)(0) 1 (2)(2) 2 4 6.
2 3 0 1 2
T
and s a B a 1 0 2 0 5 1 0 1 0 2 2 2 4 6.
0 2 1 2 2
T
2.4 Write in indicial notation the matrix equation (a) A B C , (b) D B C
and (c)
T
E B C F .
T
Ans. (a) A B C A B C , (b) D B C A
B C .
ij im m j ij mi mj
T
(c) E B C F E B C F .
ij mi mk kj
2 2 2
2 2 2
2.5 Write in indicial notation the equation (a) s A1 A2 A3 and (b) 0.
1
x2 2
x2 3
x2
2 2 2 2
2 2 2
Ans. (a) s A1 A2 A3 Ai Ai . (b) 0 0.
x12 2x
2
3 x2 i ix x
2.6 Given that Si j =aiaj and Si j =ai a j, where ai =Qmi am and a j =Qn Qik Qjk ij .
jan , and
Show that Si i =Sii .
Ans. Si j =QmiamQn jan =QmiQn jaman Si i =QmiQniaman = mn m na a =amam Smm Sii .
vi
2.7 Write ai in long form.
v vi
j
t x
j
Ans. v
v1
i 1 a v1 v1 v1
v v
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