MECHANISMS OF FAILURE M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures MODULE 4 MECHANISMS OF FAILURE SKMM 4133 Failure of Engineering.

MECHANISMS OF FAILURE M.N. Tamin, UTM

SME 4133 Failure of Engineering Components and Structures

MODULE 4

MECHANISMS OF FAILURE

SKMM 4133 Failure of Engineering Components and Structures



MECHANISMS OF FAILURE

Static failure

Tensile fracture

Ductile and brittle fracture

Creep rupture

Morphology of fracture surfaces

Fatigue failure

Stages of fatigue failure

Fatigue fracture characteristics




Tensile Fracture

Cleavage (brittle) fracture Ductile fracture

Source: Vander Voort, G.F., Metals Engineering Quarterly, Vol. 16, No. 3, 1976, pp. 33.




Fracture of Bolts in Tensile Overload

(a) Brittle fracture

(Water-quenched to 47 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)




Fracture of Shaft in Torsion Overload

Dark spiral indicates plastic deformation by

torsion Swirl pattern of fracture surface

Fracture surface is flat and perpendicular to axis of shaft

Ductile failure of 1035 steel drive shaft due to torsion overload




Fig. 4.3, Callister 7ed.

Burgers vector b

Imperfections in SolidScrew dislocation




necking void nucleation

void growth and linkage

shearing at surface

fracture

Particles serve as void

nucleation sites.

50 mm

P. Thornton, J. Mater. Sci., Vol. 6, 1971, pp. 347-56.)

Fracture Process in Ductile Materials

Slip by plastic deformation




• Ductile failure: --one piece --large deformation

• 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.

Ductile Versus Brittle Fracture




Ductile Fracture Surface

- Dimples in ductile fracture.

• Transgranular fracture (across grains)




• Intergranular fracture (between grains)

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

Brittle Fracture Surfaces




Deterioration of a material by initiation and propagation of crack when subjected to repeated load.

FATIGUE FAILURE




Formation of Fatigue Striations




Fatigue Striations




PSB – persistent slip bands

Fracture Surface Due To Fatigue


MECHANISMS OF FAILURE M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures MODULE 4 MECHANISMS OF FAILURE SKMM 4133 Failure of Engineering.

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