Page 92 - Shigley's Mechanical Engineering Design

bud29281_ch02_031-070.qxd 11/11/09 09:35 PM Page 67 Debd Hard Disk1:Desktop Folder:Temp Work:Satya 10/11/09:

Materials 67
Figure 2–19

Strength S versus density ρ for various materials. For metals, S is the 0.2 percent offset yield strength. For polymers, S is the 1 percent yield
strength. For ceramics and glasses, S is the compressive crushing strength. For composites, S is the tensile strength. For elastomers, S is the tear
strength. (Figure courtesy of Prof. Mike Ashby, Granta Design, Cambridge, U.K.)
10000
Strength–density Ceramics Si N Ti alloys
Composites SiC 3 4 O Steels Metals
Metals and polymers yield strength A Al 2 3 Ni alloys
Al alloys
Ceramics and glasses MGR Tungsten
CFRP P
1000 Elastomers tensile tear strength Mg alloys P P P alloys
Composites tensile failure Polymers and Tungsten
elastomers GFRP carbide
PEEK
PA PET T Copper
PC
100 Wood PMMA alloys
to grain
Natural
materials
Strength S, MPa 10 Rigid polymer Zinc alloys
foams
Lead alloys
Foams
1
Butyl Concrete
Wood rubber Silicone Guide lines for
to grain elastomers minimum mass
Cork design
0.1
S
2/3
S 1/2
Flexible polymer S
foams MFA D4
0.01
0.01 0.1 1 10
Density , Mg/m 3

PROBLEMS
2–1 Determine the tensile and yield strengths for the following materials:
(a) UNS G10200 hot-rolled steel.
(b) SAE 1050 cold-drawn steel.
(c) AISI 1141 steel quenched and tempered at 540°C.
(d) 2024-T4 aluminum alloy.
(e) Ti-6Al-4V annealed titanium alloy.
2–2 Assume you were specifying an AISI 1060 steel for an application. Using Table A–21,
(a) how would you specify it if you desired to maximize the yield strength?
(b) how would you specify it if you desired to maximize the ductility?
2–3 Determine the yield strength-to-weight density ratios (specific strength) in units of kN m/kg for
AISI 1018 CD steel, 2011-T6 aluminum, Ti-6Al-4V titanium alloy, and ASTM No. 40 gray cast iron.
2–4 Determine the stiffness-to-weight density ratios (specific modulus) in units of inches for AISI 1018
CD steel, 2011-T6 aluminum, Ti-6Al-4V titanium alloy, and ASTM No. 40 gray cast iron.
2–5 Poisson’s ratio ν is a material property and is the ratio of the lateral strain and the longitudinal
strain for a member in tension. For a homogeneous, isotropic material, the modulus of rigidity G
is related to Young’s modulus as
E
G =
2(1 + ν)