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Fatigue life prediction in the aerospace components relies on fracture mechanics for relatively long cracks (>1mm). Nevertheless, most of the fatigue life is spent while the crack is relatively short (<1mm). However life of short cracks is far from well understood leading engineers to apply over conservative safety factors which involves environmental and economic losses. The material microstructure is responsible for the large life uncertainty in short cracks. Recent experimental techniques, such as high-resolution X-Ray diffraction combined with tomography, have opened up exciting opportunities to in-situ fully characterize the 3D microstructure (grain shapes and orientations). This allows monitoring the deformation and crack propagation in 3D. Imaged-based models can be built from the reconstructed microstructure to provide a unique opportunity to improve crystal plasticity models for fatigue initiation.
The student will build image-based crystal plasticity models from data obtained by diffraction contrast tomography (DCT) obtained at the European Synchrotron Radiation Facility (ESRF). This would allow validation of the finite element models implemented in ABAQUS software. The student will use and further develop user material subroutines (UMAT), user element subroutines (UEL) and post-processing tools. Ultimately, this aims to fill the gap of the lack of understanding of how short fatigue cracks initiate and propagate. During the PhD programme, the student will also benefit from on-going and further collaborations with colleagues at Manchester University and Madrid Materials IMDEA institute.
We are looking for a self-motivated individual with skills in solid mechanics, mathematics and programming. Knowledge in finite element modelling (ABAQUS software) would be an advantage. The supervisory team will consist of Dr. Gonzalez and Prof. Tong from Portsmouth university and Prof. Marrow from Oxford University. Successful applicants will be awarded a University Bursary Stipend of £14,057 per annum for up to 4 years.
Some objectives are:
• To interrogate the model in terms of the effect of cyclic plastic strain and grain boundary stresses occurring within isolated regions "hot-spots" of the reconstructed microstructure at favourably oriented grains.
• To further develop the 3D crystal plasticity model in finite element ABAQUS software using a material subroutine (UMAT), user element subrounites (UEL) and the finite element mesh
• To identify the key microstructural parameters that affect fatigue crack growth
• Further objectives on modelling multi-scale plasticity are flexible depending on the interests/strenghts of the candidate
Application deadline for studentship: Sunday, April 03, 2016. Applications submitted after that will be considered for self-funded only. The studentship is, in principle, open to European Union individuals only. International applicants are normally considered for self-funded only. However, outstanding international applicants might be considered for the studentship.
Keywords: policrystalline materials, crystal plasticity, multi-scale plasticity, fatigue, finite element modelling, X-Ray diffraction
Any informal enquiries can be made to Dr. Gonzalez (firstname.lastname@example.org)
Información complementaria de la oferta:
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