Fractography Resource - [email protected] 1 Examples of Fractography in Other Materials...

Fractography Resource - [email protected]

Examples of Fractography in Other Materials

Professor M Neil [email protected]

Department of Mechanical & Marine Engineering

University of Plymouth

Drake Circus, Plymouth PL4 8AA

ENGLAND

mailto:[email protected]

mailto:[email protected]


Contents – Use the hyperlinks to navigate around this resource

WC-Co : Compression and tensile fatigue

316L stainless steel – SCC

Fatigue in polycarbonate

Fast fracture in polycarbonate



6% Co Grade T6

Rupture = 2190 MPa - average grain size = 1.8 m

The line indicates the transition between regions of compression fatigue (lower half) and tensile fatigue (upper half)

Original magnification shown by micron bar



6% Co Grade T6


Compression fatigue at higher magnification – WC grains are rounded and Co tear ridges are less frequent




6% Co Grade T6


Tensile fatigue at higher magnification – WC grains are more angular and Co tear ridges are more evident


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316L stainless steel - SCC

0.033C 1.44Mn 0.44Si 18.4Cr 8.6Ni 0.016P 0.010S

YS = 205 MPa in annealed state : Vickers hardness 235

2 mm thick, 120 mm diameter seam welded pipe used to transport glucose solution

Cracking associated with weld – inner surface of pipe shown here – significant crack branching



0.033C 1.44Mn 0.44Si 18.4Cr 8.6Ni 0.016P 0.010S



Cracking associated with weld – outer surface of pipe shown here – less crack branching

Implication: glucose is cause of problem, not external lagging



0.033C 1.44Mn 0.44Si 18.4Cr 8.6Ni 0.016P 0.010S



Fracture surface shows brittle appearance – not fatigue crack growth



0.033C 1.44Mn 0.44Si 18.4Cr 8.6Ni 0.016P 0.010S



Have 'feathery' cleavage facets present

Implication: SCC, although detrimental species not clear



0.033C 1.44Mn 0.44Si 18.4Cr 8.6Ni 0.016P 0.010S



Pipe operates at 60°C – diagram indicates that chloride SCC occurs at this temperature in acid solutions with 104 ppm of chlorides present

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YS = 20 MPa (initial cyclic yield) - annealed state – 2 mm thick plate

R = 0.5

Notch root is at the left of the picture




R = 0.5

Near the notch root




R = 0.5

Near the notch root

The marks are not fatigue striations




R = 0.5

This position is 7.5 mm from the notch root




R = 0.5

This position is 17.5 mm from the notch root

The marks are not fatigue striations – they probably relate to craze size ahead of the crack tip


Fast fracture in polycarbonate


This shows typical fast fracture in the PC

Features are very similar to fatigue

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Fractography Resource - [email protected] 1 Examples of Fractography in Other Materials...

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