SME 4133 Failure of Engineering Components and Structures MODULE 4 MECHANISMS OF FAILURE M.N. Tamin, UTM MECHANISMS OF FAILURE
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SME 4133 Failure of Engineering Components and Structures
MODULE 4
MECHANISMS OF FAILURE M.N. Tamin, UTM
MECHANISMS OF FAILURE
SME 4133 Failure of Engineering Components and Structures
MECHANISMS OF FAILURE
Static failureTensile fractureDuctile and brittle fracture
MECHANISMS OF FAILURE M.N. Tamin, UTM
Ductile and brittle fractureCreep ruptureMorphology of fracture surfaces
Fatigue failureStages of fatigue failureFatigue fracture characteristics
SME 4133 Failure of Engineering Components and Structures
Tensile Fracture
MECHANISMS OF FAILURE M.N. Tamin, UTM
Cleavage (brittle) fracture Ductile fracture
Source: Vander Voort, G.F., Metals Engineering Quarterly, Vol. 16, No. 3, 1976, pp. 33.
SME 4133 Failure of Engineering Components and Structures
Fracture of Bolts in Tensile Overload
(a) Brittle fracture
(Water-quenched to 47 Rockwell C)
MECHANISMS OF FAILURE M.N. Tamin, UTM
Rockwell C)
(b) Ductile fracture
(Annealed to 15 Rockwell C)
(c) Extensive necking and cup-and-cone fracture of an annealed bolt
(d) Brittle fracture of a quenched bolt. No obvious plastic deformation
(a) (b) (c) (d)
SME 4133 Failure of Engineering Components and Structures
Fracture of Shaft in Torsion Overload
Fracture surface is flat and perpendicular to axis of shaft
MECHANISMS OF FAILURE M.N. Tamin, UTM
Dark spiral indicates plastic deformation by
torsion Swirl pattern of fracture surface
Ductile failure of 1035 steel drive shaft due to torsion overload
SME 4133 Failure of Engineering Components and Structures
Imperfections in SolidScrew dislocation
MECHANISMS OF FAILURE M.N. Tamin, UTM
Fig. 4.3, Callister 7ed.
Burgers vector b
SME 4133 Failure of Engineering Components and Structures
necking void nucleation
void growth and linkage
shearing at surface
fracture
σ
Fracture Process in Ductile Materials
MECHANISMS OF FAILURE M.N. Tamin, UTM
Particles serve as void
nucleation sites.
50 µm
P. Thornton, J. Mater. Sci., Vol. 6, 1971, pp. 347-56.)
Slip by plastic deformation
SME 4133 Failure of Engineering Components and Structures
• Ductile failure:--one piece--large deformation
Ductile Versus Brittle Fracture
MECHANISMS OF FAILURE M.N. Tamin, UTM
• Brittle failure:--many pieces--small deformation
Figures from V.J. Colangelo and F.A. Heiser, Analysis of Metallurgical Failures(2nd ed.), Fig. 4.1(a) and (b), p. 66 John Wiley and Sons, Inc., 1987. Used with permission.
SME 4133 Failure of Engineering Components and Structures
Ductile Fracture Surface
• Transgranular fracture(across grains)
MECHANISMS OF FAILURE M.N. Tamin, UTM
- Dimples in ductile fracture.
SME 4133 Failure of Engineering Components and Structures
• Intergranular fracture(between grains)
Brittle Fracture Surfaces
MECHANISMS OF FAILURE M.N. Tamin, UTM
304 S. Steel (metal)Reprinted w/permission from "Metals Handbook", 9th ed, Fig. 633, p. 650. Copyright 1985, ASM International, Materials Park, OH. (Micrograph by J.R. Keiser and A.R. Olsen, Oak Ridge National Lab.)
4 mm
SME 4133 Failure of Engineering Components and Structures
Deterioration of a material by initiation and propagation of crack when subjected to
FATIGUE FAILURE
MECHANISMS OF FAILURE M.N. Tamin, UTM
propagation of crack when subjected to repeated load.
SME 4133 Failure of Engineering Components and Structures
Formation of Fatigue Striations
MECHANISMS OF FAILURE M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
Fatigue Striations
MECHANISMS OF FAILURE M.N. Tamin, UTM
SME 4133 Failure of Engineering Components and Structures
Fracture Surface Due To Fatigue
MECHANISMS OF FAILURE M.N. Tamin, UTM
PSB – persistent slip bands
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