Optical Diagnostics Group

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Research areas

Optical diagnostics provide greater understanding and control of engineering and scientific systems. Light adds no extra mass or stiffness to the structure and measurements can be made at many points simultaneously under service conditions. We research novel optical techniques for measuring deformation, strain, vibration, shape and fluid flow. We apply these techniques to understand and validate models for manufacturing applications, in particular additive manufacturing (3D printing) of metals.

Additive manufacture (3D printing) of metals - Powder

Key findings

· Open architecture metal powder bed fusion (PBF) system for in-situ monitoring [1]

· High-speed and schlieren imaging during PBF for multiple layer builds [2]

· First model of laser plume and ambient gas flow in build chamber for PBF [2]

· First high-speed imaging during PBF at sub-atmospheric and hyperbaric pressures [3,4]

[1] P. Bidare, R.R.J Maier, R.J. Beck, J. D. Shephard and A. J. Moore, “An open-architecture metal powder bed fusion system for in-situ process measurements”, Additive Manufacturing 16 177–185 (2017)

[2] P. Bidare, I. Bitharas, R.M. Ward, M.M. Attallah, and A.J. Moore, “Fluid and particle dynamics in laser powder bed fusion”, Acta Materialia 142 107–120 (2018)

[3] P. Bidare, I. Bitharas, R.M. Ward, M.M. Attallah and A.J. Moore, “Laser powder bed fusion at sub-atmospheric pressures”, International Journal of Machine Tools and Manufacture 130–131 65–72 (2018)

[4] P. Bidare, I. Bitharas, R.M. Ward, M.M. Attallah and A.J. Moore, “Laser powder bed fusion in high-pressure atmospheres”, International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-018-2495-7 (2018)

Additive manufacture (3D printing) of metals - Wire

Key findings

· Shadowgraphy & schlieren imaging of shield gas coverage for arc processes [1,2]

· Effect of gas flowrate, cross-drafts, and nozzle diameter, stand-off and angle on shield gas coverage [1,3]

· Multiphysics magneto-hydrodynamic (MHD) model of interaction between plasma arc and shield gas to predict shield gas coverage [3]

[1] V. Beyer, S.W. Campbell, G.M. Ramsey, T.J. Scanlon, A.M. Galloway, A.J. Moore and N.A. McPherson, “Systematic study of the effect of cross-drafts and nozzle diameter on shield gas coverage in MIG welding”, Science and Technology of Welding and Joining 18(8) 652–660 (2013)

[2] I. Bitharas, S.W. Campbell, A.M. Galloway, N.A. McPherson and A.J. Moore, “Visualisation of alternating shielding gas flow in GTAW”, Materials and Design 91 424–431 (2016)

[3] I. Bitharas, N.A. McPherson, W. McGhie, D. Roy and A.J. Moore, “Visualisation and optimisation of shielding gas coverage during MIG welding”, Journal of Materials Processing Technology 255 451–462 (2018)

Residual stress measurements using GHz and THz radiation

Key findings

· First measurement of the direct stress optic coefficient for yttria-partially stabilized zirconia (YTZP) ceramic [2]

· First observation of stress induced birefringence in air plasma sprayed (APS) ceramic thermal barrier coatings (TBCs) [3]

[1] T.D. Nguyen, J.D. Valera and A.J. Moore, “Optical thickness measurement with multi-wavelength THz interferometry”, Optics and Lasers in Engineering 61 19–22 (2014)

[2] P. Schemmel, G. Diederich and A.J. Moore, “Direct stress optic coefficients for YTZP ceramic and PTFE at GHz frequencies”, Optics Express 24(8) 8110–8119 (2016)

[3] P. Schemmel, G. Diederich and A.J. Moore, “Measurement of direct strain optic coefficient of YSZ thermal barrier coatings at GHz frequencies”, Optics Express 25(17) 19968–19980 (2017)

[4] P. Schemmel and A.J. Moore, “Monitoring stress changes in carbon fibre reinforced polymer composites with GHz radiation”, Applied Optics 56(22) 6405–6409 (2017)

Iterative laser forming / Iterative laser straightening

Key findings

· First automated, iterative forming and straightening of doubly-curved surfaces incorporating both bending and membrane strains [1,2]

· Systematic study relating changes in the mechanical properties of low carbon steel (AISI1010) and aluminium alloy (AA2024-T3) to temperature during forming [3]

· Through-thickness strain measured by neutron diffraction and related to line energy and number of passes for forming and straightening [4]

[1] R. McBride, F. Bardin, M. Gross, D.P. Hand, J.D.C. Jones and A.J. Moore, “Modelling and calibration of bending strains for iterative laser forming”, Journal of Physics D: Applied Physics 38 4027–4036 (2005)

[2] S.P. Edwardson, E. Abed, P. French, G. Dearden, K.G. Watkins, R. McBride, D.P. Hand, J.D.C. Jones and A.J. Moore, “Developments towards controlled three-dimensional laser forming of continuous surfaces”, Journal of Laser Applications 17(4) 247–255 (2005)

[3] S.M. Knupfer and A. J. Moore, “The effects of laser forming on the mechanical and metallurgical properties of low carbon steel and aluminium alloy samples”, Materials Science and Engineering A 527 4347–4359 (2010)

[4] S.M. Knupfer, A.M. Paradowska, O. Kirstein and A.J. Moore, “Characterization of the residual strains in iterative laser forming”, Journal of Materials Processing Technology 212 90–99 (2012)

Shape measurement

Key findings

· Dynamic shape measurement system for laser materials processing [1,2]

· Automated shape measurement for a monolithic fringe projection probe mounted to a coordinate measuring machine (CMM) [3,4]

[1] M. Reeves, A.J. Moore, D.P. Hand and J.D.C. Jones, “Dynamic shape measurement system for laser materials processing”, Optical Engineering 42(10) 2923–2929 (2003)

[2] M. Reeves, A.J. Moore, D.P. Hand, J.D.C. Jones, J.R. Cho, R.C. Reed, S.P. Edwardson, G. Dearden, P. French and K.G. Watkins, “Dynamic distortion measurements during laser forming of Ti-6Al-4V and their comparison with a finite element model”, Proc. IMechE B: Journal of Engineering Manufacture 217 1685–1696 (2003)

[3] Y.R. Huddart, J.D.R. Valera, N.J. Weston, T.C. Featherstone and A.J. Moore, “Phase-stepped fringe projection by rotation about the camera’s perspective center”, Optics Express 19(19) 18458–18469 (2011)

[4] Y.R. Huddart, J.D.R. Valera, N.J. Weston and A.J. Moore, “Absolute phase measurement in fringe projection using multiple perspectives”, Optics Express 21(18) 21119 (2013)

Deformation, Strain and Vibration measurement

Key findings

· First measurements with microsecond temporal resolution using speckle pattern interferometry [1,2]

· Quantified surface velocity limit and extended it with spatial phase stepping [3,5]

[1] A.J. Moore, D.P. Hand, J.S. Barton and J.D.C. Jones, “Transient deformation measurement with ESPI and a high speed camera”, Applied Optics 38(7) 1159–1162 (1999)

[2] J.M. Kilpatrick, A.J. Moore, J.S. Barton, J.D.C. Jones, M. Reeves and C. Buckberry, “Measurement of complex surface deformation by high-speed dynamic phase-stepped digital speckle pattern interferometry”, Optics Letters 25(15) 1068–1070 (2000)

[3] T. Wu, J.D.C. Jones and A.J. Moore, “High-speed phase-stepped digital speckle pattern interferometry using a CMOS camera”, Applied Optics 45(23) 5845–5855 (2006)

[4] W.N. MacPherson, M. Reeves, D.P. Towers, A.J. Moore, and J.D.C. Jones, M. Dale, C. Edwards, “Multipoint laser vibrometer for modal analysis”, Applied Optics 46(16) 3126–3132 (2007)

[5] T. Wu, J.D. Valera and A.J. Moore, “High-speed, sub-Nyquist interferometry”, Optics Express 19(11) 10111–10123 (2011)