Shigleys Mechanical Engineering Design
By Keith Nisbett Richard Budynas
11th edition
Chapter 1 Solutions - Rev. B, Page 1/6
,chapter 1
Problems 1-1 through 1-6 are for student research. No standard solutions are provided.
1-7 From fig. 1-2, cost of grinding to 0.0005 in is 270%. Cost of turning to 0.003 in is
60%.
Relative cost of grinding vs. Turning = 270/60 = 4.5 times ans.
1-8 Ca = cb,
10 + 0.8 p = 60 + 0.8 p − 0.005 p 2
P 2 = 50/0.005 p = 100 parts ans.
1-9 Max. Load = 1.10 p
min. Area = (0.95)2a
min. Strength = 0.85 s
To offset the absolute uncertainties, the design factor, from eq. (1-1) should be
1.10
Nd = = 1.43 ans.
0.85(0.95)
2
1-10 (a) x1 + x2:
X1 + x2 = x1 + e1 + x 2 + e2
Error = e = ( x1 + x2 ) − ( x1 + x 2 )
= e1 + e2 ans.
(b) X1 − x2:
X1 − x2 = x1 + e1 − ( x 2 + e2 )
E = ( x1 − x2 ) − ( x1 − x 2 ) = e1 − e2 Ans.
(c) X1 x2:
X1x2 = ( x1 + e1 )( x 2 + e2 )
E = x1 x2 − x1 x 2 = x1e2 + x 2e1 + e1e2
x e + x e = x x e1 + e2 ans.
1 2 2 1 1 2
x x
1 2
Chapter 1 Solutions - Rev. B, Page 2/6
, (d) X1/x2:
x1 x1 + e1 x1 1+ e1 X1
x = x + e = x 1+ e x
2 2 2 2 2 2
−1
e e2 1+ e x e e e e
1 − then −
1+
2 1 1 1 2 1 2
1+ 1− 1+
x2 x2 1+ e2 x 2 x1 x2 x1 x 2
x1 x1
Thus, e = − x1 e1 e2 ans.
x x x x −x
2 2 2 1 2
1-11 (a) x1 = 7 = 2.645 751 311 1
X1 = 2.64 (3 correct digits)
x2 = 8 = 2.828 427 124 7
X2 = 2.82 (3 correct digits)
X1 + x2 = 5.474 178 435 8
E1 = x1 − x1 = 0.005 751 311 1
E2 = x2 − x2 = 0.008 427 124 7
E = e1 + e2 = 0.014 178 435 8
sum = x1 + x2 = x1 + x2 + e
= 2.64 + 2.82 + 0.014 178 435 8 = 5.474 178 435 8 checks
(b) X1 = 2.65, x2 = 2.83 (3 digit significant numbers)
E1 = x1 − x1 = − 0.004 248 688 9
E2 = x2 − x2 = − 0.001 572 875 3
E = e1 + e2 = − 0.005 821 564 2
sum = x1 + x2 = x1 + x2 + e
= 2.65 +2.83 − 0.001 572 875 3 = 5.474 178 435 8 checks
S 16 (1000) ( )
25 103
1-12 = = d = 0.799 in ans.
Nd d 3 2.5
7
table a-17: d= in ans.
( )
8
S 25 103
Factor of safety: n= = = 3.29 ans.
16 (1000)
(7)
3
8
n
1-13 eq. (1-5): r = ri = 0.98(0.96)0.94 = 0.88
I=1
Overall reliability = 88 percent ans.
Chapter 1 Solutions - Rev. B, Page 3/6
, 1-14 a = 1.500 0.001 in
B = 2.000 0.003 in
C = 3.000 0.004 in
D = 6.520 0.010 in
(a) W = d − a − b − c = 6.520 − 1.5 − 2 − 3 = 0.020 in
tw = tall = 0.001 + 0.003 + 0.004 +0.010 = 0.018
W = 0.020 0.018 in ans.
(b) from part (a), wmin = 0.002 in. Thus, must add 0.008 in to d . Therefore,
D = 6.520 + 0.008 = 6.528 in ans.
1-15 v = xyz, and x = a a, y = b b, z = c c,
V = abc
V = (a a)(b b)(c c)
= abc bca acb abc abc bca cab abc
The higher order terms in are negligible. Thus,
v bca + acb + abc
v bca + acb + abc a b c a b c
And, = + + = + + ans.
v abc a b c a b c
for the numerical values given, v = 1.500 (1.875)3.000 = 8.4375 in3
v 0.002 0.003 0.004
= + + = 0.00427 v = 0.00427 (8.4375) = 0.036 in3
V 1.500 1.875 3.000
V = 8.438 0.036 in3 ans.
Chapter 1 Solutions - Rev. B, Page 4/6