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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: 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.X-ray diffraction provides information about the crack-tip stress field, phase transformations, plastic zone and crack-face tractions and forces.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 measured (a) and best-fit (b) elastic strain fields (in 10−6) for the crack-opening (εyy) direction at KImax=6.6 MPa√m for an Al 5091 CT sample. The LEFM best-fit crack-tip strains correspond to a crack-tip stress intensity of KeffImax=6.11 MPa√m,KeffIImax=0.33MPa√m (table 1) [22]. (Online version in colour.)
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RSTA20130157F17: The measured (a) and best-fit (b) elastic strain fields (in 10−6) for the crack-opening (εyy) direction at KImax=6.6 MPa√m for an Al 5091 CT sample. The LEFM best-fit crack-tip strains correspond to a crack-tip stress intensity of KeffImax=6.11 MPa√m,KeffIImax=0.33MPa√m (table 1) [22]. (Online version in colour.)

Mentions: By comparing the measured crack-tip strain field directly with that predicted by LEFM, it is possible to infer the stress intensity factor effective at the crack tip, Keff, directly from the local elastic strain field [22], as summarized in table 1 for the strain field in figure 17. It is evident from the table that in this case, where the plastic zone is small, the nominal stress intensity calculated from the crack length, the applied load and the specimen geometry is in very good agreement with that actually experienced by the crack tip. One of the disadvantages of fitting to the K field is the need to accurately know the location of the crack tip [98].Figure 17.


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

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

The measured (a) and best-fit (b) elastic strain fields (in 10−6) for the crack-opening (εyy) direction at KImax=6.6 MPa√m for an Al 5091 CT sample. The LEFM best-fit crack-tip strains correspond to a crack-tip stress intensity of KeffImax=6.11 MPa√m,KeffIImax=0.33MPa√m (table 1) [22]. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

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

RSTA20130157F17: The measured (a) and best-fit (b) elastic strain fields (in 10−6) for the crack-opening (εyy) direction at KImax=6.6 MPa√m for an Al 5091 CT sample. The LEFM best-fit crack-tip strains correspond to a crack-tip stress intensity of KeffImax=6.11 MPa√m,KeffIImax=0.33MPa√m (table 1) [22]. (Online version in colour.)
Mentions: By comparing the measured crack-tip strain field directly with that predicted by LEFM, it is possible to infer the stress intensity factor effective at the crack tip, Keff, directly from the local elastic strain field [22], as summarized in table 1 for the strain field in figure 17. It is evident from the table that in this case, where the plastic zone is small, the nominal stress intensity calculated from the crack length, the applied load and the specimen geometry is in very good agreement with that actually experienced by the crack tip. One of the disadvantages of fitting to the K field is the need to accurately know the location of the crack tip [98].Figure 17.

Bottom Line: 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.X-ray diffraction provides information about the crack-tip stress field, phase transformations, plastic zone and crack-face tractions and forces.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