Latest Papers

〈a〉 Prismatic, 〈a〉 basal, and 〈c+a〉 slip strengths of commercially pure Zr by micro-cantilever tests
J Gong, TB Britton, MA Cuddihy, FPE Dunne, AJ Wilkinson
Acta Materialia (2015) vol. 96, 249-257

Measurements of stress fields near a grain boundary: Exploring blocked arrays of dislocations in 3D
Y Guo, DM Collins, E Tarleton, F Hofmann, J Tischler, W Liu, R Xu, AJ Wilkinson, TB Britton
Acta Materialia (2015) vol. 96, 229-236

On the mechanistic basis of deformation at the microscale in hexagonal close-packed metals
TB Britton, FPE Dunne, AJ Wilkinson
Proceedings of the Royal Society A (2015) vol. 471, 20140881

Evolution of intragranular stresses and dislocation densities during cyclic deformation of polycrystalline copper
J Jiang, TB Britton, AJ Wilkinson
Acta Materialia (2015) vol. 94, 193-204

The orientation and strain dependence of dislocation structure evolution in monotonically deformed polycrystalline copper
J Jiang, TB Britton and AJ Wilkinson
International Journal of Plasticity (2015) vol. 69, 102-117

A synchrotron X-ray diffraction study of in situ biaxial deformation
DM Collins, M Mostafavi, RI Todd, T Connolley and AJ Wilkinson
Acta Materialia (2015) vol. 90, 46-58

A discrete dislocation plasticity study of the micro-cantilever size effect
E Tarleton, DS Balint, J Gong, and AJ Wilkinson
Acta Materialia (2015) vol. 88, 271-282

Pair of Acta Materialia Papers on Twinning
Hamidreza Abdolvand has published a pair of papers on deformation twinning in Zircaloy-2. The first paper reports on experimental measurements made at ESRF beamline ID11 using the 3D-XRD method developed by the Riso/DTU group. During an in situ tensile study the method was used to characterise the size, position, orientation and average lattice strain state in grains within a sample volume of ~0.8x0.8x0.9mm. There were a little over 6100 grains in the sample volume a the start of the experiment but after ~2.8% strain twinning meant that the same volume was segmented into over 9700 grains. The progressive increase in lattice strains and amount of twinning was followed using observations at 7 different strain levels. In the second paper results are presented from a large (2600 grain) CP-FEA simulation using a microstructure constructed from the 3D-XRD data. The model captures the twinning well. The stresses in twin and parent gran pairs are examined just after twin formation for both experimental and simulated results. A significant finding is that local normal stresses in the twin and parrent pairs both normal to the twin habit plane and along the twin shear direction are essentially identical.

Hamid A 3DXRD Zr twining
ESRF April 2015 team photo

Experiment at ID11 ESRF
We were fortunate to get allocated 18 shifts (6 days) of beamtime at ID11 ESRF. Hamid Abdolvand who had drafted the proposal led the team consisting of Jicheng Gong, Dave Collins, Yi Guo. Jon Wright (centre of photo) provided tremendous support both in the lead up to the experiment and during it. The team successfully ran a series of 3D XRD measurments during in situ tensile testing of Ti and Zr samples. With help from Wolfgang Ludwig some diffraction contrast tomography scans were also conducted taken at the start and and of the deformation experiments. Hamid will be kept busy with data analysis for a considerable time.

Dislocation Dynamics embedded in FEA
Ed Tarleton in collaboration with Daniel Balint (Imperial College) have successfully embedded discrete dislocation dynamics simulations of plasticity within a finite element analysis framework that handles complex displacement and traction boundary conditions. This new modelling capability is an important tool for analysis of small scale mechanical testing experiments. Micro-cantilever bend tests on hexagonal Ti and Zr crystals conducted by Jicheng Gong have been simulated. The marked size effect, stochastic flow behaviour, and slip band spacing evident in the experiments are all well captured by the simulations. The study is reported in Acta Materialia

DDD-FEA modelling
Meet us at

ICM12 2015
12th Int Conf on Mechanical Behaiour of Materials

KIT, Germany, 10–14 May 2015
- Junnan Jiang will be presenting on micromechanical testing of grain boundary sliding

ICMM 2015
4th Int Conf on Material Modeling

Berkeley CA, 27–29 May 2015
- several members of the group will be attending and Hamid A will be presenting

M and M 2015
Microscopy and Microanalysis 2015

Portland, OR, 2-6 August 2015
- presentations by Angus W on 'progress with EBSD strain mapping', and Arantxa V-C on 'EBSD strain mapping in III-V nitride' and on 'Transmission Kikuchi Diffraction'

Int Conf on Strength of Materials 2015

Brno, Czech Republic, 9–14 August 2015
- several members of the group will be attending and hopefully presenting talks and posters

ECI nanomechanics
Nanomechanical Testing of Materials V

Albufeira, Portugal, 4-9 October 2015
- Angus W and Jicheng G will be attending and presenting talks/posters