ASM Metals HandBook Vol. 8 - Mechanical Testing and Evaluation
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• Axial tension or compression
• Bending, shear, and torsion
• Internal or external pressure
• Stress concentrations and localized contact loads
Mechanical testing under these basic stress conditions using the expected product load/time profile (static,
impact, cyclic) and within the expected product environment (thermal, chemical, electromagnetic, radiation,
etc.) provides the design data required for most applications.
In conducting mechanical tests, it is also very important to recognize that the material may contain flaws and
that its microstructure (and properties) may be directional (as in composites) and heterogeneous or dependent
on location (as in carburized steel). To provide accurate material characteristics for design, one must take care
to ensure that the geometric relationships between the microstructure and the stresses in the test specimens are
the same as those in the product to be designed.
It is also important to consider the complexity of materials selection for a combination of properties such as
strength, toughness, weight, cost, and so on. This article briefly describes design criteria for some basic
property combinations such as strength, weight, and costs. More detailed information on various performance
indices in design, based on the methodology of Ashby, can be found in the article “Material Property Charts” in
Materials Selection and Design, Volume 20 of ASM Handbook. The materials selection method developed by
Ashby is also available as an interactive electronic product (Ref 1).
Reference cited in this section
1. Cambridge Engineering Selector, Granta Design Ltd., Cambridge, UK, 1998
Overview of Mechanical Properties and Testing for Design
Howard A. Kuhn, Concurrent Technologies Corporation
Product Design
Design involves the application of physical principles and experience-based knowledge to develop a predictive
model of the product. The model may be a prototype, a simplified mathematical model, or a complex finite
element model. Regardless of the level of sophistication of the model, reaching the product design objectives of
material and geometry specifications for successful product performance requires accurate material parameters
(Ref 2).
Modern design methods help manage the complex interactions between product geometry, material
microstructure, loading, and environment. In particular, engineering mechanics (from simple equilibrium
equations to complex finite element methods) extrapolates the results of basic mechanical testing of simple
shapes under representative environments to predict the behavior of actual product geometries under real
service environments.
In the following sections, a simple tie bar is used to illustrate the application of mechanical property data to
material selection and design and to highlight the general implications for mechanical testing. Material
subjected to the basic stress conditions is considered in order to establish design approaches and mechanical test
methods, first in static loading and then in dynamic loading and aggressive environments. More detailed
reference books on mechanical design and engineering methods are also listed in the “Selected References” at
the end of this article.
Reference cited in this section
2. G.E. Dieter, Engineering Design: A Materials and Processing Approach, McGraw Hill, 1991, p 1–51, p
231–271
Overview of Mechanical Properties and Testing for Design
Howard A. Kuhn, Concurrent Technologies Corporation
Tensile Loading
Design for Strength in Tension. Figure 1 shows an axial tensile load applied to a tie bar representing, for
example, a boom crane support, cable, or bolt. For this elementary case, the stress in the bar is uniformly
distributed over the cross section of the tie bar and is given by:
σ = F/A
(Eq 1)
where F is the applied force and A is the cross-sectional area of the bar. To avoid failure of the bar, this stress
must be less than the failure stress, or strength, of the material:
σ = F/A < σ
f
(Eq 2)
where σ
f
is the stress at failure. The failure stress, σ
f
, can be the yield strength, σ
o
, if permanent deformation is
the criterion for failure, or the ultimate tensile strength, σ
u
, if fracture is the criterion for failure. In a ductile
metal or polymer, the ultimate tensile strength is defined as the stress at which necking begins, leading to
fracture. In a brittle material, the ultimate strength is simply the stress at fracture. Typical values of yield and
ultimate tensile strength for various materials are summarized in Tables 1, 2, and 3. These typical values are
intended only for general comparisons; design values should be based on statistically based minimum values or
on minimum values published in the purchase specifications of materials (such as ASTM standards).
Table 1 Typical room-temperature mechanical properties of ferrous alloys and superalloys
Strength in tension,
MPa (ksi)
Strength in torsional
shear, MPa (ksi)
Modulus of
elasticity, GPa (10
6
psi)
Material
0.2%
offset
yield
strength
Ultimate
0.2% offset
compressive
yield
strength,
MPa (ksi)
0.2% offset
yield
strength
Ultimate Tension Shear
Elongation
in 50
mm (2 in.),
%
Hardness,
HB
Cast irons
Gray cast iron … 140 (20) 240 (35) … 255 (37) 105 (15) 40 (6) 1 130
White cast iron … 415 (60) 690 (100) … 415 (60) 140 (20) 55 (8) … 400
Nickel cast iron, 1.5% nickel … 310 (45) 415 (60) … … 140 (20) 55 (8) 1 200
Malleable iron 230 (33) 345 (50) 230 (33) 130 (19) 330 (48) 170 (25) 70 (10) 14 120
Ingot iron, annealed 0.02%
carbon
165 (24) 290 (42) 145 (21) 105 (15) 205 (30) 205 (30) 85 (12) 45 70
Wrought iron, 0.10% carbon 205 (30) 345 (50) 205 (30) 125 (18) 240 (35) 185 (27) 70 (10) 30 100
Steels
Wrought iron, 0.10% carbon 205 (30) 345 (50) 205 (30) 125 (18) 240 (35) 185 (27) 70(10) 30 100
Steel, 0.20% carbon
Hot-rolled
275 (40) 415 (60) 275 (40) 165 (24) 310 (45) 200 (29) 85 (12) 35 120
Cold-rolled 415 (60) 550 (80) 415 (60) 250 (36) 415 (60) 200 (29) 85 (12) 15 160
Annealed castings 240 (35) 415 (60) 240 (35) 145 (21) 310 (45) 200 (29) 85 (12) 25 130
Steel, 0.40% carbon
Hot-rolled
290 (42) 485 (70) 290 (42) 170 (25) 380 (55) 200 (29) 85 (12) 25 135
Heat-treated for fine grain 415 (60) 620 (90) 415 (60) 250 (36) 515 (75) 200 (29) 85 (12) 25 190
Annealed castings 240 (35) 450 (65) 240 (35) 145 (21) 380 (55) 200 (29) 85 (12) 15 130
Steel, 0.60% carbon
Hot-rolled
435 (63) 690 (100) 435 (63) 255 (37) 550 (79.8) 200 (29) 85 (12) 15 200
Heat-treated for fine grain 540 (78) 825 (120) 540 (78) 325 (47) 690 (100) 200 (29) 85 (12) 15 235
Steel, 0.80% carbon
Hot-rolled
505 (73) 825 (120) 505 (73) 305 (44) 725 (103) 200 (29) 85(12) 10 240
Oil-quenched, not drawn 860 (125) 1240
(180)
860 (125) 515 (75) 1035
(150)
200 (29) 85 (12) 2 360
Steel, 1.00% carbon
Hot-rolled
570 (83) 930 (135) 570 (83) 345 (50) 795 (115) 200 (29) 85 (12) 10 260
Oil-quenched, not drawn 965 (140) 1515 965 (140) 580 (84) 1275 200 (29) 85 (12) 1 430
(220) (185)
Nickel steel, 3.5% nickel,
0.40% carbon, max. hardness
for machinability
1035
(150)
1170
(170)
1035 (150) 620 (90) 965 (140) 200 (29) 85 (12) 12 350
Silicomanganese steel, 1.95%
Si, 0.70% Mn, spring tempered
895 (130) 1200
(174)
895 (130) 540 (78) 795 (115) 200 (29) 85 (12) 1 380
Superalloys (wrought)
A286 (bar) 760 (110) 1080
(157)
… … … 180 (26) … 28 …
Inconel 600 (bar) 250 (36) 620 (90) … … … … … 47 …
IN-100 (60 Ni-10Cr-15Co,
3Mo, 5.5Al, 4.7Ti)
850 (123) 1010
(147)
… … … 215 (31) … 9 …
IN-738 915 (133) 1100
(159)
… … … 200 (29) … 5 …
Source: Ref 3, 4
Table 2 Typical room-temperature mechanical properties of nonferrous alloys
Metal or alloy Approximate
composition, %
Condition 0.2% offset
tensile yield
strength,
MPa (ksi)
Tensile
strength,
MPa (ksi)
Tensile
modulus
of
elasticity,
GPa (10
6
psi)
Elongation
in
50 mm (2
in.), %
Ultimate
shear
strength,
MPa (ksi)
Hardness
Heavy nonferrous alloys (~8–9 g/cm
3
)
Annealed 33 (4.8) 209 (30) 125 (18) 60 …
…
Copper Cu
Cold drawn 333 (48) 344 (50) 112 (16) 14 …
337 HRB
Annealed 125 (18) 340 (49) 85 (12) 53 205 (30)
68 HRF
Quarter hard, 15%
reduction
310 (45) 385 (56) 85 (12) 20 230 (33)
62 HRB
Free-cutting brass 61.5 Cu, 35.5 Zn, 3 Pb
Half hard, 25%
reduction
360 (52) 470 (68) 95 (14) 18 260 (38)
80 HRB
Annealed, 0.050
mm grain
105 (15) 325 (47) 85 (12) 55 230 (33)
66 HRF
High-leaded brass
(1 mm thick)
65 Cu, 33 Zn, 2 Pb
Extra hard 425 (62) 585 (85) 105 (15) 5 310 (45)
87 HRB
Annealed, 0.070
mm grain
70 (10) 270 (39) 85 (12) 48 215 (31)
66 HRF
Red brass (1 mm
thick)
85 Cu, 15 Zn
Extra hard 420 (61) 540 (78) 105 (15) 4 305 (44)
83 HRB
Sand cast 195 (28) 515 (75) … 40 …
…
Aluminum bronze 89 Cu, 8 Al, 3 Fe
Extruded 260 (38) 565 (82) 125 (18) 25 …
…
A (solution
annealed)
… 500 (73) 125 (18) 35 …
60 HRB
Beryllium copper 97.9 Cu, 1.9 Be, 0.2 Ni
HT (hardened) 1035 (150) 1380 (200) 125 (18) 2 …
42 HRC
Soft annealed 205 (30) 450 (65) 90 (13) 35 290 (42)
65 HRB
Manganese bronze
(A)
58.5 Cu, 39 Zn, 1.4 Fe,
1 Sn, 0.1 Mn
Hard, 15% reduction
415 (60) 565 (82) 105 (15) 25 325 (47)
90 HRB
Annealed, 0.035
mm grain
150 (22) 340 (49) 90 (13) 57 …
33 HRB
Phosphor bronze,
5% (A)
95 Cu, 5 Sn
Extra hard, 0.015
mm grain
635 (92) 650 (94) 115 (17) 5 …
94 HRB
Annealed at 760 °C 140 (20) 380 (55) 150 (22) 45 …
37 HRB
Cupronickel, 30% 70 Cu, 30 Ni
Cold drawn, 50%
reduction
540 (78) 585 (85) 150 (22) 15 …
81 HRB
Light nonferrous alloys (~2.7 g/cm
3
for Al alloys; ~1.8 g/cm
3
for Mg alloys)
Sand cast, 1100-F 40 (5.8 or 6) 75 (11) 60 (9) 22 …
…
Annealed sheet,
1100-O
35 (5.075) 90 (13) 70 (10) 35 …
…
Aluminum Al
Hard sheet, 1100-
H18
145 (21) 165 (24) 70 (10) 5 …
…
Temper O 75 (11) 185 (27) 73 (11) 20 125 (18)
90 HRH
Aluminum alloy
2024
93 Al, 4.5 Cu, 1.5 Mg,
0.6 Mn
Temper T36 395 (57) 495 (72) 73 (11) 13 290 (42)
80 HRB
Temper O 95 (14) 185 (27) 73 (11) 18 125 (18)
192 HRH
Aluminum alloy
2014
93 Al, 4.4 Cu, 0.8 Si,
0.8 Mn, 0.4 Mg
Temper T6 415 (60) 485 (70) 73 (11) 13 290 (42)
83 HRB
Temper O 90 (13) 195 (28) 69 (10) 30 125 (18)
82 HRH
Aluminum alloy
5052
97 Al, 2.5 Mg, 0.25 Cr
Temper H38 255 (37) 290 (42) 69 (10) 8 164 (24)
85 HRE
Temper O 160 (23) 310 (45) … 24 195 (28)
…
Aluminum alloy
5456
94 Al, 5.0 Mg, 0.7 Mn,
0.15 Cu, 0.15 Cr
Temper H321 255 (37) 350 (51) … 16 205 (30)
…
Temper O 105 (15) 230 (33) … 17 150 (22)
65 HRE
Aluminum alloy
7075
90 Al, 5.5 Zn, 1.5 Cu,
2.5 Mg, 0.3 Cr
Temper T6 505 (73) 570 (83) … 11 330 (48)
90 HRB
Cast 21 (3) 90 (13) 40 (6) 2–6 …
16 HRE
Extruded 69–105 (10–
15)
195 (28) 40 (6) 5–8 …
26 HRE
Magnesium Mg
Rolled 115–140
(17–20)
200 (29) 40 (6) 2–10 …
51 HRE
Cast, condition F 85 (12) 150 (22) 45 (7) 2 125 (18)
64 HRE
Magnesium alloy
AM100A
90 Mg, 10 Al, 0.1 Mn
Cast, condition T61 150 (22) 275 (40) 45 (7) 1 145 (21)
80 HRE
Cast, condition F 95 (14) 200 (29) 45 (7) 6 125 (18)
59 HRE
Magnesium alloy
AZ63A
91 Mg, 6 Al, 3 Zn, 0.2
Mn
Cast, condition T6 130 (19) 275 (40) 45 (7) 5 140 (20)
83 HRE
Titanium alloys (~4.5 g/cm
3
)
Commercial
ASTM grade 2 Ti
98 Ti … 275 (40) 345 (50) 103 (15) 20 …
80 HRB
Ti-5Al-2.5Sn 92 Ti, 5 Al, 2.5 Sn … 825 (120) 860 (125) 110 (16) 8–10 …
36 HRC
Annealed 560 (81) 655 (95) 103 (15) 29 …
15–25
HRC
Ti-3Al-2.5V 94 Ti, 3 Al, 2.5 V
Cold worked and
stress relieved
760 (110) 895 (130) 103 (15) 19 …
24–27
HRC
Solution treated and
aged bar (1–2 in.)
965 (140) 1035 (150) 110 (16) 8 620 (90)
36–39
HRC
Annealed bar 825 (120) 895 (130) 110 (16) 10 …
…
Ti-6A1-4V 90 Ti, 6 Al, 4 V
Mill annealed … 925 (134) … … 545 (79) …
Table 3 Typical room-temperature mechanical properties of plastics
Material Tensile
strength,
MPa (ksi)
Elongation,
%
Modulus of
elasticity
GPa (10
6
psi)
Compressive
strength,
MPa (ksi)
Modulus of
rupture,
MPa (ksi)
Hardness
Thermosets
EP, reinforced
with glass cloth
350 (51) … 175 (25) 410 (59) 485 (70)
MF, alpha-
cellulose filler
50–90 (7–13) 0.6–0.9 9 (1) 170–300 (25–
44)
70–110 (10–
16)
110–125
HRM
PF, no filler 50–55 (7–9) 1.0–1.5 5–7 (0.7–1) 70–200 (10–29) 80–100 (12–
15)
124–128
HRM
PF, wood flour
filler
45–60 (7–9) 0.4–0.8 6–8 (0.87–
1.16)
160–250 (23–
36)
60–85 (9–
12)
100–120
HRM
PF, macerated
fabric filler
25–65 (4–9) 0.4–0.6 6–9 (0.87–1)
100–160 (15–
24)
60–100 (9–
15)
95–120
HRM
PF, cast, no
filler
40–65 (6–9) 1.5–2.0 3 (0.43) 85–115 (12–17) 75–115 (11–
17)
93–120
HRM
Polyester,
glass-fiber
filler
35–65 (5–9) … 11–14 (1.6–
2.0)
140–175 (20–
25)
95–115 (14–
17)
…
UF, alpha-
cellulose filler
55–90 (8–13) 0.5–1.0 10 (1.5) 175–240 (25–
35)
70–100 (10–
15)
115–120
HRM
Thermoplastics
ABS 35–45 (5–7) 15–60 1.7–2.2
(0.25–0.32)
25–50 (4–7) …
95–105
HRR
CA 15–60 (2–9) 6–50 0.6–3.0
(0.1–0.4)
90–250 (13–36) 15–110 (2–
16)
50–125
HRR
CN 50–55 (7–9) 40–45 1.3–15.0
(0.18–2)
150–240 (22–
35)
60–75 (9–
11)
95–115
HRR
PA 80 (12) 90 3.0 (0.43 85 (12) …
79 HRM,
118 HRR
PMMA 50–70 (7–10) 2–10 … 80–115 (12–17) 90–115 (13–
17)
85–105
HRM
PS 35–60 (5–9) 1–4 3.0–4.0
(0.4–0.6)
80–110 (12–16) 55–110 (8–
16)
65–90
HRM
PVC, rigid 40–60 (6–9) 5 2.4–2.7
(0.3–0.4)
60 (9) …
110–120
HRR
PVCAc, rigid 50–60 (7–9) … 2.0–3.0
(0.3–0.4)
70–80 (10–12) 85–100 (12–
15)
…
ABS, acrylonitrile-butadiene-styrene; CA, cellulose acetate; CN, cellulose nitrate; EP, epoxy; MF, melamine
formaldehyde; PA, polyamide (nylon); PF, phenol formaldehyde; PMMA, polymethyl methacrylate; PS,
polystyrene; PVC, polyvinyl chloride; PVCAc, polyvinyl chloride acetate; UF, urea formaldehyde.
Source: Ref 6
Fig. 1 Bar under axial tension
Equation 2 combines the performance of the part (load F) with the part geometry (cross-sectional area A) and
the material characteristics (strength σ
f
). The equation can be used several ways for design and material
selection. If the material and its strength are specified, then, for a given load, the minimum cross-sectional area
can be calculated; or, for a given cross-sectional area, the maximum load can be calculated. Conversely, if the
force and area are specified, then materials with strengths satisfying Eq 2 can be selected.
Factor of Safety. Normally, designs involve the use of some type of a factor of safety. This factor, which is
always greater than unity, is used in the design of components to ensure that the component can satisfactorily
perform it intended purpose. The factor of safety is used to account for the uncertainties that exist in the real-
world use of any component. Two main classifications of factors affect the factor of safety in a design, and they
are these:
• Uncertainties associated with the material properties of the component itself, including the expected
properties of the materials used to fabricate the component, as well as any uncertainties introduced by
manufacturing and fabrication processing.
• Uncertainties associated with the level and type of loading the component will see, as well as the actual
service conditions and any environmental condition the component may experience.
The factor of safety is used to establish a target stress level for the design. This is sometimes referred to as the
allowable stress, the maximum allowable stress, or simply, the design stress. In order to determine this
allowable stress condition, the failure stress is simply divided by the safety factor. Safety factors ranging from
1.5 to 10 are typical. The lower the uncertainty is, the lower the safety factor.
Design for Strength, Weight, and Cost. If minimum weight or minimum cost criteria must also be satisfied, Eq
2 can be modified by introducing other material parameters. To illustrate, the area A in Eq 2 is related to density
and mass by A = M/ρL, where M is the mass of the bar, L is the length of the bar, and ρ is the material density.
Solving Eq 2 for F and substituting for A:
F < σ
f
A = (σ
f
/ρ)(M/L)
(Eq 3)
From Eq 3 it is clear that, to transmit a given load, F, the material mass will be minimized if the property ratio
(σ
f
/ρ) is maximized. The strength-to-weight ratio of a material is an important design and performance index;
Fig. 2 is a plot developed by Ashby for comparison of materials by this design criterion. Similarly, material
selection for minimum material cost can be obtained by maximizing the parameter (σ
f
/ρc), or strength-to-cost
ratio, where c represents the material cost per unit weight. These types of performance indices for design and
the use of materials property charts like Fig. 2 are described in more detail in Ref 7 and in the articles “Material
Property Charts” and “Performance Indices” in Materials Selection and Design, Volume 20 of ASM Handbook.
Fig. 2 Strength, σ
i
, plotted against density, ρ, for various engineered materials. Strength is yield strength
for metals and polymers, compressive strength for ceramic, tear strength for elastomers, and tensile
strength for composites. Superimposing a line of constant σ
f
/ρ enables identification of the optimum class
of materials for strength at minimum weight.
Design for Stiffness in Tension. In addition to designing for strength, another important design criterion is often
the stiffness or rigidity of a material. The elastic deflection of a component under load is governed by the
stiffness of the material. For example, if a bridge or building is designed to avoid failure, it may still undergo
motion under applied loads if it is not sufficiently rigid. As another example, if the tie bar in Fig. 1 were a bolt
clamping a cap to a pressure vessel, excessive elastic change in length of the bolt under load might allow
leakage through a gasket between the cap and vessel.
Elastic change in length occurs when an axial load is applied to the bar and is given by:
ΔL = εL
(Eq 4)
where ΔL is the change in length and ε is the strain in the bar. In the elastic range of deformation, axial stress is
proportional to the strain:
σ = Eε
(Eq 5)
where the proportionality factor is E, the elastic modulus of the bar material.
The elastic modulus can be considered a physical property, because it is fundamentally related to the bond
strength between the atoms or molecules in the material; that is, the stronger the bond, the higher the elastic
modulus. Thus, the elastic modulus does not vary much in material with a given type of crystal structure or
microstructure. For example, the elastic modulus of most steels is typically about 200 GPa (29 × 10
6
psi) for
steels of various composition and strength levels (Fig. 3). However, the modulus can vary with direction if the
material has an anisotropic structure. For example, Fig. 4 is a plot of the tensile and compressive modulus for
type 301 austenitic stainless steel. Transverse and longitudinal values vary, as do values for tensile and
compressive loads. At low stresses, the tension and compressive moduli are, by theory and experiment,
identical. At higher stresses, however, differences in the compressive and tensile moduli can be observed due to
the effects of deformation (e.g., elongation in tension). Typical values of elastic moduli are given in Table 4 for
various alloys and metals.
Table 4 Elastic constants for polycrystalline metals at 20 °C
Elastic modulus (E) Bulk modulus (K) Shear modulus (G) Metal
GPa 10
6
psi GPa 10
6
psi GPa 10
6
psi
Poisson's
ratio, ν
Aluminum 70 10.2 75 10.9 26 3.80
0.345
Brass, 30 Zn 101 14.6 112 16.2 37 5.41
0.350
Chromium 279 40.5 160 23.2 115 16.7
0.210
Copper 130 18.8 138 20.0 48 7.01
0.343
Iron, soft 211 30.7 170 24.6 81 11.8
0.293
Iron, cast 152 22.1 110 15.9 60 8.7
0.27
Lead 16 2.34 46 6.64 6 0.811
0.44
Magnesium 45 6.48 36 5.16 17 2.51
0.291
Molybdenum 324 47.1 261 37.9 125 18.2
0.293
Nickel, soft 199 28.9 177 25.7 76 11.0
0.312
Nickel, hard 219 31.8 188 27.2 84 12.2
0.306
Nickel-silver, 55Cu-18Ni-27Zn 132 19.2 132 19.1 34 4.97
0.333
Niobium 104 15.2 170 24.7 38 5.44
0.397
Silver 83 12.0 103 15.0 30 4.39
0.367
Steel, mild 211 30.7 169 24.5 82 11.9
0.291
Steel, 0.75 C 210 30.5 169 24.5 81 11.8
0.293
Steel, 0.75 C, hardened 201 29.2 165 23.9 78 11.3
0.296
Steel, tool steel 211 30.7 165 24.0 82 11.9
0.287
Steel, tool steel, hardened 203 29.5 165 24.0 79 11.4
0.295
Steel, stainless, 2Ni-18Cr 215 31.2 166 24.1 84 12.2
0.283
Tantalum 185 26.9 197 28.5 69 10.0
0.342
Tin 50 7.24 58 8.44 18 2.67
0.357
Titanium 120 17.4 108 15.7 46 6.61
0.361
Tungsten 411 59.6 311 45.1 161 23.3
0.280
Vanadium 128 18.5 158 22.9 46.7 6.77
0.365
Zinc 105 15.2 70 10.1 42 6.08 0.249
Source: Ref 9