Fracture

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 britte !ractures are the t"o most           O important !orms o! ser#ice !aiure in "eded          L structures           O • Fatigue !ractures account !or more than $0% o! a          N ser#ice !aiures          H • &ritte !ractures athough rare in occurrence are usuay           C catastrophic in economic terms and may cause oss in          E i!e          T

Fracture Surfaces

SWI 3.2

         Y Introduction:           G • Fatigue and britte !ractures are the t"o most           O important !orms o! ser#ice !aiure in "eded          L structures           O • Fatigue !ractures account !or more than $0% o! a          N ser#ice !aiures          H • &ritte !ractures athough rare in occurrence are usuay           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 !aiure           O •(ccurs under cycic)!uctuating stress          L •'mooth appearance           O •Initi Initiates ates at some !orm !orm o! stress concentrati concentration* on* These          N stress points may be "ed de!ects+ poor pro!ies+          H notches etc           C •In certain cases e#idence o! beach mar,ings          E •Fracture occurs perpendicuar to the appied 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

SWI 3.2

Fatigue Fracture Surfaces          Y          G          O          L          O          N          H          C          E          T Copyright © 2003 TWI Ltd

SWI 3.2

/uctie !racture

&each .ar,s M.S.Rogers

Ductile Fracture          Y          G          O          L          O          N          H          C          E          T

Features o! ductie !ractures: •ough !ibrous appearance •/u grey in coour  •In certain cases e#idence o! shear ips •In most cases a reduction in area •(ccurs as a secondary mode o! !aiure

SWI 3.2

Brittle Fracture Features o! britte !ractures:

         Y •1suay occurs "ithout #isibe or audibe "arning          G •In certain cases bright crystaine appearance          O •In certain cases a che#ron pattern appearance+ the          L che#ron pattern points bac, to the point o!          O initiation          N •Litte i! no reduction in area          H •Litte i! no e#idence o!! shear ips           C •.ay be a straight britte !racture or secondary          E mode o! !aiure          T

SWI 3.2

Brittle Fracture          Y          G          O          L          O          N          H          C          E          T

SWI 3.2

Brittle Fracture          Y          G          O          L          O          N          H          C          E          T

SWI 3.2

Brittle Fracture          Y          G          O          L          O          N          H          C          E          T

SWI 3.2

Fracture Assessments          Y          G          O          L          O          N          H          C          E          T

SWI 3.2

emember in the C'WI- 3*2 'enior Weding Inspectors eamination your are reuired to conduct a practica eamination o! t"o !racture sampes and compete a s,etch and a !ina report on your !indings  Time  30

ao"ed 4 hour !or both !racture sampes

minutes !or each !racture sampe

Fracture Assessments          Y          G          O          L          O          N          H          C          E          T

5ou are reuired • ',etch the !racture sur!ace* • Indicate the !racture initiation points 6i! ,no"n7 • 'ho" any de!ects present • Identi!y the primary mode o! !aiure • Identi!y the secondary mode o! !aiure • 'tate "hether !aiure occurred in the "ed+ parent materia or both 6i! ,no"n7 • Write a concusion to summari8e your !indings+ pro#iding reasons and e#idence • 'ign and date your report

SWI 3.2

SWI 3.2

FractureSample 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 pointsweld 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 Concusion: 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 eident 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 eident 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

SWI 3.2

Fracture Assessment Report specimen 2. 

9

F

F

;

SWI 3.2

/ 

         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 Concusion: 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 eident by the smooth fracture surface (). The fatigue crack stopped at point (F). The secondary mode of failure is a ductile fracture this is eident by the rough fibrous          E  fracture surface (D), the eidence 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 Concusion: The butt weld failed due to fatigue cracks which initiated from weld metal defects ("). The cracks hae a smooth appearance this is eidence of fatigue fracture (#).           C The secondary mode of failure which is the final mode is a ductile fracture this is eident          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

SWI 3.2

         Y &* Beach mark  & C* Fatigue fracture surface          G / /* &hear lipsslight 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 Concusion: 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 eident by the smooth           C The appearance of the fracture surface.          E The secondary and final mode of failure is a ductile fracture (") this is eident by the dull  gray fibrous appearance of the fracture surface, eident 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.

SWI 3.2

Fracture Assessment Report specimen 5. &

SWI 3.2

 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 Concusion: 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 distinctie 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#cheron fracture surface ( Brittle          C fracture.          E )ote* Small shear lips along ,oth plate surfaces.          T

SWI 3.2

Fracture Assessment Report specimen 6.  A

SWI 3.2

         Y  A* &light shear lips &* Brittle fracture          G C &  surfacecheron pattern          O C* 'nitiation point           L  A DI+C/I0) 0F -+0-+!A/I0)           O Primary and final mode of failure: Brittle fracture          N Concusion: This serice failure has no isible initiation point, the fracture is a brittle          H  fracture this is eident by the uniform cheron 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 eident.          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 eidence 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          NConcusion: The T$D sample failed from a purposely initiated fatigue crack           HThe primary mode of failure is a fatigue fracture (B) this is eident by the smooth fracture  surface, which initiated from a machined notch (#). The secondary mode of failure is a           Cbrittle fracture () this is eident by the crystalline fracture surface with ery little          Eeidence of plastic deformation (ery little reduction in area) and no eidence 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 Concusion: The T$D sample failed from a purposely initiated fatigue crack           H The primary mode of failure is a fatigue fracture (B) this is eident by the smooth fracture           C  surface, which initiated from a machined notch (#). The secondary mode of failure is a ductile fracture (D) this is eident by the fibrous appearance of the fracture surface with          E eidence 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

SWI 3.2

Fracture Assessment Report specimen !.  A* racksforging bursts

SWI 3.2

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          Concusion: 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 eident 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 eident by the fibrous appearance of the fracture surface with          Eeidence of plastic deformation. The final mode of failure is brittle (D) this is eident 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

SWI 3.2

9

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

SWI 3.2

 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 Concusion: 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 eident at the weld toe. The fatigue cracks tip is eident 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 eident by the          T  fibrous appearance of the fracture.
/ate: 43)0=)03

'ignature: M.S Rogers