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Fracture mechanics by three-dimensional crack-tip synchrotron X-ray microscopy.

Withers PJ - Philos Trans A Math Phys Eng Sci (2015)

Bottom Line: X-ray diffraction provides information about the crack-tip stress field, phase transformations, plastic zone and crack-face tractions and forces.Time-lapse CT, besides providing information about the three-dimensional nature of the crack and its local growth rate, can also provide information as to the activation of extrinsic toughening mechanisms such as crack deflection, crack-tip zone shielding, crack bridging and crack closure.It is shown how crack-tip microscopy allows a quantitative measure of the crack-tip driving force via the stress intensity factor or the crack-tip opening displacement.

View Article: PubMed Central - PubMed

Affiliation: Manchester X-ray Imaging Facility, School of Materials, Manchester University, Manchester M13 9PL, UK Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0FA, UK p.j.withers@manchester.ac.uk.

ABSTRACT
To better understand the relationship between the nucleation and growth of defects and the local stresses and phase changes that cause them, we need both imaging and stress mapping. Here, we explore how this can be achieved by bringing together synchrotron X-ray diffraction and tomographic imaging. Conventionally, these are undertaken on separate synchrotron beamlines; however, instruments capable of both imaging and diffraction are beginning to emerge, such as ID15 at the European Synchrotron Radiation Facility and JEEP at the Diamond Light Source. This review explores the concept of three-dimensional crack-tip X-ray microscopy, bringing them together to probe the crack-tip behaviour under realistic environmental and loading conditions and to extract quantitative fracture mechanics information about the local crack-tip environment. X-ray diffraction provides information about the crack-tip stress field, phase transformations, plastic zone and crack-face tractions and forces. Time-lapse CT, besides providing information about the three-dimensional nature of the crack and its local growth rate, can also provide information as to the activation of extrinsic toughening mechanisms such as crack deflection, crack-tip zone shielding, crack bridging and crack closure. It is shown how crack-tip microscopy allows a quantitative measure of the crack-tip driving force via the stress intensity factor or the crack-tip opening displacement. Finally, further opportunities for synchrotron X-ray microscopy are explored.

No MeSH data available.


Related in: MedlinePlus

The fibre stresses measured at the fatigue crack plane shown in figure 10 for a Ti–Al–4V/35% SiC fibre composite can be considered as crack-face tractions at (a) Kmax and (b) Kmin. These crack-closing (a) and crack-opening (b) stresses are shown superimposed upon the measured continuum crack-tip stress field (in MPa; after [50]) derived by summing the stresses in each phase in their correct phase fractions. The crack length is approximately 0.35 through the width of the sample. (Online version in colour.)
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RSTA20130157F18: The fibre stresses measured at the fatigue crack plane shown in figure 10 for a Ti–Al–4V/35% SiC fibre composite can be considered as crack-face tractions at (a) Kmax and (b) Kmin. These crack-closing (a) and crack-opening (b) stresses are shown superimposed upon the measured continuum crack-tip stress field (in MPa; after [50]) derived by summing the stresses in each phase in their correct phase fractions. The crack length is approximately 0.35 through the width of the sample. (Online version in colour.)

Mentions: Often, measurements of the COD are used to infer the crack-face tractions [99]. However, in some cases, the crack-face tractions can be determined and the effective stress intensity range can be calculated either using weight functions [100] or by finite-element methods [101]. In some cases, diffraction can provide a direct measure of the bridging stresses. By way of an example, consider the fibre stresses shown in figure 10 for a Ti–Al–4V/35% SiC fibre composite. The net effect of these fibres can be considered as crack-face tractions acting over the crack faces, as shown in figure 18. These crack-face tractions can then be used to infer the stress intensity range effective at the crack tip, as shown in figure 19. What is clear from the figure is that as the crack grows more and more fibres bridge the crack, so that, ultimately, the fibres either break or arrest the crack [10,50].Figure 18.


Fracture mechanics by three-dimensional crack-tip synchrotron X-ray microscopy.

Withers PJ - Philos Trans A Math Phys Eng Sci (2015)

The fibre stresses measured at the fatigue crack plane shown in figure 10 for a Ti–Al–4V/35% SiC fibre composite can be considered as crack-face tractions at (a) Kmax and (b) Kmin. These crack-closing (a) and crack-opening (b) stresses are shown superimposed upon the measured continuum crack-tip stress field (in MPa; after [50]) derived by summing the stresses in each phase in their correct phase fractions. The crack length is approximately 0.35 through the width of the sample. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4308984&req=5

RSTA20130157F18: The fibre stresses measured at the fatigue crack plane shown in figure 10 for a Ti–Al–4V/35% SiC fibre composite can be considered as crack-face tractions at (a) Kmax and (b) Kmin. These crack-closing (a) and crack-opening (b) stresses are shown superimposed upon the measured continuum crack-tip stress field (in MPa; after [50]) derived by summing the stresses in each phase in their correct phase fractions. The crack length is approximately 0.35 through the width of the sample. (Online version in colour.)
Mentions: Often, measurements of the COD are used to infer the crack-face tractions [99]. However, in some cases, the crack-face tractions can be determined and the effective stress intensity range can be calculated either using weight functions [100] or by finite-element methods [101]. In some cases, diffraction can provide a direct measure of the bridging stresses. By way of an example, consider the fibre stresses shown in figure 10 for a Ti–Al–4V/35% SiC fibre composite. The net effect of these fibres can be considered as crack-face tractions acting over the crack faces, as shown in figure 18. These crack-face tractions can then be used to infer the stress intensity range effective at the crack tip, as shown in figure 19. What is clear from the figure is that as the crack grows more and more fibres bridge the crack, so that, ultimately, the fibres either break or arrest the crack [10,50].Figure 18.

Bottom Line: X-ray diffraction provides information about the crack-tip stress field, phase transformations, plastic zone and crack-face tractions and forces.Time-lapse CT, besides providing information about the three-dimensional nature of the crack and its local growth rate, can also provide information as to the activation of extrinsic toughening mechanisms such as crack deflection, crack-tip zone shielding, crack bridging and crack closure.It is shown how crack-tip microscopy allows a quantitative measure of the crack-tip driving force via the stress intensity factor or the crack-tip opening displacement.

View Article: PubMed Central - PubMed

Affiliation: Manchester X-ray Imaging Facility, School of Materials, Manchester University, Manchester M13 9PL, UK Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0FA, UK p.j.withers@manchester.ac.uk.

ABSTRACT
To better understand the relationship between the nucleation and growth of defects and the local stresses and phase changes that cause them, we need both imaging and stress mapping. Here, we explore how this can be achieved by bringing together synchrotron X-ray diffraction and tomographic imaging. Conventionally, these are undertaken on separate synchrotron beamlines; however, instruments capable of both imaging and diffraction are beginning to emerge, such as ID15 at the European Synchrotron Radiation Facility and JEEP at the Diamond Light Source. This review explores the concept of three-dimensional crack-tip X-ray microscopy, bringing them together to probe the crack-tip behaviour under realistic environmental and loading conditions and to extract quantitative fracture mechanics information about the local crack-tip environment. X-ray diffraction provides information about the crack-tip stress field, phase transformations, plastic zone and crack-face tractions and forces. Time-lapse CT, besides providing information about the three-dimensional nature of the crack and its local growth rate, can also provide information as to the activation of extrinsic toughening mechanisms such as crack deflection, crack-tip zone shielding, crack bridging and crack closure. It is shown how crack-tip microscopy allows a quantitative measure of the crack-tip driving force via the stress intensity factor or the crack-tip opening displacement. Finally, further opportunities for synchrotron X-ray microscopy are explored.

No MeSH data available.


Related in: MedlinePlus