Bolt Failures

SME 4133 Failure of Engineering Components and Structures

MODULE 4

MECHANISMS OF FAILURE M.N. Tamin, UTM

MECHANISMS OF FAILURE


MECHANISMS OF FAILURE

Static failureTensile fractureDuctile and brittle fracture


Ductile and brittle fractureCreep ruptureMorphology of fracture surfaces

Fatigue failureStages of fatigue failureFatigue 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)


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

Fracture surface is flat and perpendicular to axis of shaft


Dark spiral indicates plastic deformation by

torsion Swirl pattern of fracture surface

Ductile failure of 1035 steel drive shaft due to torsion overload


Imperfections in SolidScrew dislocation


Fig. 4.3, Callister 7ed.

Burgers vector b


necking void nucleation

void growth and linkage

shearing at surface

fracture

Fracture Process in Ductile Materials


Particles serve as void

nucleation sites.

50 m

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

Slip by plastic deformation


Ductile failure:--one piece--large deformation

Ductile Versus Brittle Fracture


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 Fracture Surface

Transgranular fracture(across grains)


- Dimples in ductile fracture.


Intergranular fracture(between grains)

Brittle Fracture Surfaces


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


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

FATIGUE FAILURE


propagation of crack when subjected to repeated load.


Formation of Fatigue Striations



Fatigue Striations



Fracture Surface Due To Fatigue


PSB persistent slip bands

Bolt Failures

Documents

Transcript of Bolt Failures