SWI 3.2
Y G O L O N H C E T
Senior Welding Inspection Fracture Assessments Course Reference WIS 10
Fracture Surfaces
SWI 3.2
Y Introduction: G • Fatigue and britte !ractures are the t"o most O important !orms o! ser#ice !aiure in "eded L structures O • Fatigue !ractures account !or more than $0% o! a N ser#ice !aiures H • &ritte !ractures athough rare in occurrence are usuay C catastrophic in economic terms and may cause oss in E i!e T
Fracture Surfaces
SWI 3.2
Y Introduction: G • Fatigue and britte !ractures are the t"o most O important !orms o! ser#ice !aiure in "eded L structures O • Fatigue !ractures account !or more than $0% o! a N ser#ice !aiures H • &ritte !ractures athough rare in occurrence are usuay C catastrophic in economic terms and may cause oss in E i!e T
Fatigue atigue Fracture ractu re Surface Surfaces s racture Features o! Fatigue !ractures:
SWI 3.2
Y G •'er#ice !aiure O •(ccurs under cycic)!uctuating stress L •'mooth appearance O •Initi Initiates ates at some !orm !orm o! stress concentrati concentration* on* These N stress points may be "ed de!ects+ poor pro!ies+ H notches etc C •In certain cases e#idence o! beach mar,ings E •Fracture occurs perpendicuar to the appied stress T
SWI 3.2
Fatigue Fractures Y G O L O N H C E T
Fatigue cracking at the weld toe
Fatigue Fracture Surfaces Y G O L O N H C E T
-oints o! initiation
Smooth fracture surface
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Fatigue Fracture Surfaces Y G O L O N H C E T Copyright © 2003 TWI Ltd
SWI 3.2
/uctie !racture
&each .ar,s M.S.Rogers
Ductile Fracture Y G O L O N H C E T
Features o! ductie !ractures: •ough !ibrous appearance •/u grey in coour •In certain cases e#idence o! shear ips •In most cases a reduction in area •(ccurs as a secondary mode o! !aiure
SWI 3.2
Brittle Fracture Features o! britte !ractures:
Y •1suay occurs "ithout #isibe or audibe "arning G •In certain cases bright crystaine appearance O •In certain cases a che#ron pattern appearance+ the L che#ron pattern points bac, to the point o! O initiation N •Litte i! no reduction in area H •Litte i! no e#idence o!! shear ips C •.ay be a straight britte !racture or secondary E mode o! !aiure T
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Brittle Fracture Y G O L O N H C E T
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Brittle Fracture Y G O L O N H C E T
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Brittle Fracture Y G O L O N H C E T
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Fracture Assessments Y G O L O N H C E T
SWI 3.2
emember in the C'WI- 3*2 'enior Weding Inspectors eamination your are reuired to conduct a practica eamination o! t"o !racture sampes and compete a s,etch and a !ina report on your !indings Time 30
ao"ed 4 hour !or both !racture sampes
minutes !or each !racture sampe
Fracture Assessments Y G O L O N H C E T
5ou are reuired • ',etch the !racture sur!ace* • Indicate the !racture initiation points 6i! ,no"n7 • 'ho" any de!ects present • Identi!y the primary mode o! !aiure • Identi!y the secondary mode o! !aiure • 'tate "hether !aiure occurred in the "ed+ parent materia or both 6i! ,no"n7 • Write a concusion to summari8e your !indings+ pro#iding reasons and e#idence • 'ign and date your report
SWI 3.2
SWI 3.2
FractureSample 1 Y G O L O N A. Initiation point H B. Initiation point Initiation point C C. D. Initiation point E . Initiation point F. Initiation point T !. Initiation point
Ductile Fracture
". Weld crater#crater pipe I. Cap undercut $. Ductile fracture %. Ductile fracture &. Fatigue fracture '. Shear lips
Fracture Assessment Report specimen 1. &
F
&
C
&
SWI 3.2
A* &hear lips &* 'nitiation pointsweld toe undercut 9 C* eld spatter /* Fatigue fracture surface 9* Ductile fracture surface F* eld undercut A ;* *oor weld craters . *ossible beach marks
Y 9 ; G ; O A L & / & / O Primary mode of failure: Fatigue perpendicular to the applied stress Secondary mode of failure: Ductile fracture N Concusion: Fatigue failure occurred at the weld toes of a fillet weld on both sides of the joint. The fatigue failure has initiated at a number of points along the weld toes (B), theses separately H initiated into fatigue cracks and joined up by a series of steps on each side of joint (D) this is eident by the smooth appearance of the fracture surface. The fatigue C the of thecrack stopped at he possible beach marks (!). E The secondary and final mode of failure is a ductile fracture (") this is eident by t he rough fibrous appearance and areas of shear lips (#). $ther points of interest are the poor T weld craters (%) and the weld undercut (F).
/ate: 43)0=)03
'ignature: M.S Rogers
Fracture Sample 2 Y G O L O N H C E T
A(A. Initiation point B. Stepping C. Stepping D. Ductile fracture . Inclusions F. Inclusions !. Fatigue fracture
Ductile Fracture
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Fracture Assessment Report specimen 2.
9
F
F
;
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/
Y & G C / A A O A* &hear lips &* -eduction in area C* Fatigue fracture /* Ductile fracture L 9* &tepping F* Beach markings ;* 'nclusions >. 'nitiation point O Primary mode of failure: Fatigue perpendicular to the applied stress Secondary mode of failure: Ductile fracture N Concusion: Fracture occurred at the weld toe (!+!) of a butt weld along its entire length. H # fatigue crack has initiated at the weld toe (!+!) along the welds entire length, this is C eident by the smooth fracture surface (). The fatigue crack stopped at point (F). The secondary mode of failure is a ductile fracture this is eident by the rough fibrous E fracture surface (D), the eidence of shear lips (#) and a reduction in area (B). $ther T points to notice are the opening up of the plate inclusions (%) in the rolled direction.
/ate: 43)0=)03
'ignature: M.S Rogers
Fracture Sample 3 Y G O L O N H C E T
SWI 3.2
Ductile Fracture A.
Slag inclusion
B.
Slag inclusion
C.
Slag inclusion
D.
Shear lip
.
Slag inclusion
F. !. ".
Shear lip Fatigue fracture Ductile fracture
)ote* +eduction in area
Fracture Assessment Report specimen 3. &
SWI 3.2
A* Fatigue fracture surface &* &hear lips C* -educed area /* Ductile fracture surface 9* eld defects (slag inclusions) F* Beach markings
Y F / / G C O L A 9 A 9 O 9 A Primary mode of failure: Fatigue perpendicular to the applied stress N Secondary mode of failure: Ductile fracture H Concusion: The butt weld failed due to fatigue cracks which initiated from weld metal defects ("). The cracks hae a smooth appearance this is eidence of fatigue fracture (#). C The secondary mode of failure which is the final mode is a ductile fracture this is eident E by the dull fibrous appearance of the fracture surface (D), shear lips (B) and a slight reduction in area (). T
/ate: 43)0=)03
'ignature: M.S Rogers
Fracture Sample 4 Y G O L O N H C E T
SWI 3.2
Ductile Fracture A.
!as pore#initiation point
B.
Beach mark
C.
Ductile fracture
D.
Fatigue fracture
.
Shear lip
F.
Shear lip
!.
Shear lip
Fracture Assessment Report specimen 4. /
A* %as pore
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Y &* Beach mark & C* Fatigue fracture surface G / /* &hear lipsslight reduction in area O A 9* Ductile fracture surface L C O Primary mode of failure: Fatigue perpendicular to the applied stress N Secondary mode of failure: Ductile fracture Concusion: The metal shaft failed due to a fatigue crack, which initiated from a small H gas pore (#) primary mode of failure is from a fatigue crack () this is eident by the smooth C The appearance of the fracture surface. E The secondary and final mode of failure is a ductile fracture (") this is eident by the dull gray fibrous appearance of the fracture surface, eident of shear lips (D) and a reduction T in area (D).
9
/ate: 43)0=)03
'ignature: M.S Rogers
Fracture Sample 5 Y G Brittle Fracture O L O N A. Weld defect possi,le toe crack initiation point point H B. Small shear lip C C. Shear lip E D. Shear lip T )ote* -atterned fracture surface ( Brittle fracture.
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Fracture Assessment Report specimen 5. &
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A
Y A* eld defect, possible toe crack G &* &hear lips O C* *atterned brittle fracture L C C O Primary and final mode of failure: Brittle fracture N Concusion: The brittle fracture initiated from a welding defect, possible toe crack. brittle fracture occurred in a butt weld, initiated from a welding defect, possible H #toestraight crack (#). C The brittle fracture surface () has a distinctie pattern of markings which radiate from the surface of the weld toe defect, possible toe crack (#). 't should be noted that the E pattern points back towards the initiation point (#). $ther features of interest are the T slight shear lips (B).
/ate: 43)0=)03
'ignature: M.S Rogers
Fracture Sample 6 Y G O L O N Brittle Fracture H )ote* -atterned#cheron fracture surface ( Brittle C fracture. E )ote* Small shear lips along ,oth plate surfaces. T
SWI 3.2
Fracture Assessment Report specimen 6. A
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Y A* &light shear lips &* Brittle fracture G C & surfacecheron pattern O C* 'nitiation point L A DI+C/I0) 0F -+0-+!A/I0) O Primary and final mode of failure: Brittle fracture N Concusion: This serice failure has no isible initiation point, the fracture is a brittle H fracture this is eident by the uniform cheron pattern (B), which points back towards the C origin of the fracture initiation point. E $ther interesting points are the slight shear lips (#) and no reduction in area eident. T
Fracture Sample 7 Y G O L O N H C E T
SWI 3.2
C/0D Brittle Fracture A
B
A.
'achined notch initiation point
B.
Fatigue fracture surface
C.
Brittle fracture
)ote* 1er little reduction in area and no eidence of shear lips
C
Fracture Assessment Report specimen 7. A* achined notch, initiation point
SWI 3.2
Y A &* Fatigue fracture surface G C* brittle fracture surface & O Primary and final mode of failure: Fatigue L fracture C Secondary mode of failure: Brittle fracture. O NConcusion: The T$D sample failed from a purposely initiated fatigue crack HThe primary mode of failure is a fatigue fracture (B) this is eident by the smooth fracture surface, which initiated from a machined notch (#). The secondary mode of failure is a Cbrittle fracture () this is eident by the crystalline fracture surface with ery little Eeidence of plastic deformation (ery little reduction in area) and no eidence of shear lips T
Fracture Sample Y G O L O N H C E T
SWI 3.2
C/0D Ductile Fracture A
B
A.
'achined notch initiation point
B.
Fatigue fracture surface
C.
Ductile fracture surface
)ote* /he reduction in area and the
C
large shear lips
Fracture Assessment Report specimen . A* achined notch, initiation point
SWI 3.2
Y A &* Fatigue fracture surface G C* &hear lips & O /* Ductile fracture surface L Primary and final mode of failure: Fatigue C / fracture O Secondary mode of failure: Ductile fracture. N Concusion: The T$D sample failed from a purposely initiated fatigue crack H The primary mode of failure is a fatigue fracture (B) this is eident by the smooth fracture C surface, which initiated from a machined notch (#). The secondary mode of failure is a ductile fracture (D) this is eident by the fibrous appearance of the fracture surface with E eidence of plastic deformation, a large reduction in area and shear lips (). T
Fracture Sample ! Y G O L O N H C E T
/ A ;
Ductile # Brittle Fracture
F &
C
9
A. B. C. D. .
F. Ductile fracture Cracks # forging ,ursts. !. Brittle fracture Cracks # forging ,ursts. Cracks # forging ,ursts Initiation point # threat tip Fatigue fracture
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Fracture Assessment Report specimen !. A* racksforging bursts
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C Y / &* Fatigue fracture surface A G 9 C* Ductile fracture surface /* Brittle fracture surface & O 9* 'nitiation point L A A and final mode of failure: Fatigue fracture Primary O of failure: Brittle fracture. Third mode of failure: Brittle fracture Concusion: NSecondary mode The threaded bar failed from a fatigue crack, which initiated at the base ofH the thread ("). The primary mode of failure is a fatigue fracture (B) this is eident by the smooth fracture which initiated from the base of the thread ("). The secondary mode of failure is surface, C a ductile fracture () this is eident by the fibrous appearance of the fracture surface with Eeidence of plastic deformation. The final mode of failure is brittle (D) this is eident by Tthe bright crystalline fracture surface.
/ate: 43)0=)03
'ignature: M.S Rogers
Y G O L & O N H A. C B. E C. T
Fracture Sample 1"
F
C
Ductile Fracture / &
A
9
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Fatigue fracture surface. D. Initiation point # weld toe undercut Ductile fracture surface. Initiation point # weld toe . Beach marks F. Weld spatter undercut
Fracture Assessment Report specimen 1". F
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A* Fatigue fracture surface
&* Ductile fracture surface Y C / C* 'nitiation point, weld toe G undercut A & A & /* 'nitiation point, weld toe O undercut L 9* Beach markings 9 9 O F. eld spatter N Primary mode of failure: Fatigue perpendicular to the applied stress mode of failure: Ductile fracture H Secondary Concusion: The fabricated cruciform joint failed as a result of a fatigue fracture this is by the smooth fracture surface (#), its point of initiation (,D), possible undercut C eident at the weld toe. The fatigue cracks tip is eident by the beach markings ("), where the stop and starts with each stress cycle. E crack The secondary and final mode of failure is a ductile fracture (B) this is eident by the T fibrous appearance of the fracture.
/ate: 43)0=)03
'ignature: M.S Rogers