Chapter 6: Failure Prediction for Static Loading

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Chapter 6 Failure Prediction for Static Loading
The concept of failure is central to the design
process, and it is by thinking in terms of
obviating failure that successful designs are
achieved. Henry Petroski Design Paradigms
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Rectangular Plate with Hole
Figure 6.1 Rectangular plate with hole subjected
to axial load. (a) Plate with cross-sectional
plane (b) one-half of plate with stress
distribution (c) plate with elliptical hole
subjected to axial load.
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Rectangular Plate with Hole
Figure 6.1 Stress concentration factors for
rectangular plate with central hole. (a) Uniform
tension.
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Rectangular Plate with Pin-Loaded Hole
Figure 6.2 Stress concentration factors for
rectangular plate with central hole. (b)
pin-loaded hole.
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Rectangular Plate with Hole in Bending
Figure 6.2 Stress concentration factors for
rectangular plate with central hole. (c) Bending.
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Axially Loaded Rectangular Plate with Fillet
Figure 6.3 Stress concentration factors for
rectangular plate with fillet. (a) Axial load.
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Rectangular Plate with Fillet in Bending
Figure 6.3 Stress concentration factors for
rectangular plate with fillet. (b) Bending.
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Axially Loaded Rectangular Plate with Groove
Figure 6.4 Stress concentration factors for
rectangular plate with groove. (a) Axial load.
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Rectangular Plate with Groove in Bending
Figure 6.4 Stress concentration factors for
rectangular plate with groove. (b) Bending.
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Axially Loaded Round Bar with Fillet
Figure 6.5 Stress concentration factors for
round bar with fillet. (a) Axial load.
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Round Bar with Fillet in Bending
Figure 6.5 Stress concentration factors for
round bar with fillet. (b) Bending.
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Round Bar with Fillet in Torsion
Figure 6.5 Stress concentration factors for
round bar with fillet. (c) Torsion.
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Axially Loaded Round Bar with Groove
Figure 6.6 Stress concentration factors for
round bar with groove. (a) Axial load.
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Round Bar with Groove in Bending
Figure 6.6 Stress concentration factors for
round bar with groove. (b) Bending.
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Round Bar with Groove in Torsion
Figure 6.6 Stress concentration factors for
round bar with groove. (c) Torsion.
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Round Bar with Hole
Figure 6.7 Stress concentration factors for
round bar with hole.
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Stress Contours
Figure 6.8 Flat plate with fillet axially loaded
showing stress contours for (a) square corners
(b) rounded corners (c) small grooves and (d)
small holes.
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Modes of Fracture
Figure 6.9 Three modes of crack displacement.
(a) Mode I, opening (b) mode II, sliding (c)
Mode III, tearing.
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Fracture Toughness
Table 6.1 Yield stress and fracture toughness
data for selected engineering materials at room
temperature.
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Failure Prediction for Multiaxial Stresses I.
Ductile Materials
Maximum Shear Stress Theory (MSST)
Distortion-Energy Theory (DET)
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Failure Prediction for Multiaxial Stresses II.
Brittle Materials
Maximum Normal Stress Theory (MNST)
Internal Friction Theory (IFT)
Modified Mohr Theory
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Three-Dimensional Yield Locus
Figure 6.10 Three-dimensional yield locus for
MSST and DET.
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MSST and DET for Biaxial Stress State
Figure 6.12 Graphical representation of
distortion energy theory for biaxial stress state.
Figure 6.11 Graphical representation of
maximum-shear-stress theory for biaxial stress
state.
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Example 6.6
Figure 6.13 Rear wheel suspension used in
Example 6.6
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Examples 6.7 and 6.8
Figure 6.14 Cantilevered round bar with torsion
applied to free end used in Example 6.7.
Figure 6.15 Cantilevered round bar with torsion
and transverse force applied to free end used in
Example 6.8.
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Maximum Normal Stress Theory
Most suitable for fibrous brittle materials,
glasses, and brittle materials in general.
Figure 6.16 Graphical representation of
maximum-normal-stress theory (MNST) for biaxial
stress state.
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Internal Friction and Modified Mohr Theories
Figure 6.17 Internal friction theory and
modified Mohr theory for failure prediction of
brittle materials.
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Experimental Verification
Figure 6.18 Experimental verification of yield
and fracture criteria for several materials. (a)
Brittle fracture (b) ductile yielding.
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Stress Analysis of Artificial Hip
Figure 6.21 Sections of femoral stem analyzed
for static failure.
Figure 6.19 Inserted total hip replacement.
Figure 6.20 Dimension of femoral implant (in
inches).