Prof. Harm Askes

Professor of Computational Mechanics
Head of Department

Address:
Department of Civil and Structural Engineering
Sir Frederick Mappin Building
Mappin Street, Sheffield, S1 3JD

Telephone: +44 (0) 114 222 5769
Fax: +44 (0) 114 222 5700
Email: h.askes@sheffield.ac.uk

Qualifications

PhD (Delft University of Technology, Netherlands), MSc (Delft University of Technology, Netherlands)

Profile

Harm Askes obtained his MSc degree in Civil Engineering from Delft University of Technology (Netherlands) in 1995. He also studied psychology and philosophy at Leiden University (Netherlands). In 2000 he was awarded a PhD from Delft University of Technology for his work in computational methods for failure analysis. From 1999 until 2004 he was an Assistant Professor at the Faculty of Civil Engineering in Delft, where he was teaching Structural Mechanics and carrying out research in the field of Computational Mechanics. In September 2004 he was appointed Professor of Computational Mechanics at the Department of Civil and Structural Engineering of the University of Sheffield. He has been Head of Department since September 2009.

His research interests are the modelling of engineering structures and materials. The two main themes are Numerical Methods and Mechanics of Materials:

Numerical Methods:

• Error estimation and mesh adaptivity are required for efficient and accurate finite element analysis. Of particular interest are novel Arbitrary Lagrangian-Eulerian formulations based on the equilibrium of configurational forces.
• Constraint equations are an essential ingredient of many mathematical models. Recent work includes the use of negative penalty functions in terms of stiffness or inertia, and the simultaneous use of stiffness penalties and inertia penalties.

Mechanics of Materials:

• Failure of engineering materials is simulated within a multi-scale modelling framework using the homogenisation of Representative Volume Elements. For strain-softening materials this requires special measures, such as the coupled-volume approach that links micro and macro-scale volumes. Recent developments focus on extending this methodology to dynamics.
• Gradient-enriched continuum theories can be used to capture a range of microstructure-driven phenomena such as wave dispersion, size effects and strain localisation. Of particular interest is the implementation of gradient theories, which is normally not straightforward due to the higher-order continuity requirements. Research is carried out to re-formulate fourth-order equations as a set of coupled second-order equations.

In his free time, Harm enjoys reading comics and modern European history, cooking and eating various types of curries, running and watching football. He has published one novel (in Dutch) and still pretends to be a life-long fan of Ajax FC.

Activities and Distinctions

• Voted "Best Lecturer" of the Department by graduating students in June 2008
• Executive Committee of the UK Association of Computational Mechanics in Engineering (2005-present)
• Editorial Advisory Panel of the Proceedings of the ICE "Engineering and Computational Mechanics" (2007-present)
• Associate Editor of the Journal of the Mechanical Behavior of Materials (2007-present)
• Visiting Professor of the Universitat Politecnica de Catalunya (Barcelona, Spain) (2005-2006, 2008-present)
• External Examiner of the MSc Structural Engineering & Mechanics, University of Glasgow & Edinburgh University (2008-2011)
• External Examiner Civil Engineering, University of Nottingham (2010-2013)

Selected Publications

Numerical Methods:

• Le CV, Askes H and Gilbert M (2010) Adaptive Element-Free Galerkin method applied to the limit analysis of plates. Computer Methods in Applied Mechanics and Engineering, 199, August, pp 2487-2496. ISSN 0045-7825. DOI 10.1016/j.cma.2010.04.004
• Askes H, Caramés-Saddler M and Rodriguez-Ferran A (2010) Bipenalty method for time domain computational dynamics. Proceedings of the Royal Society A, 466, May, pp 1389-1408. ISSN 1364-5021. DOI 10.1098/rspa.2009.0350
• Pannachet T, Sluys LJ and Askes H (2009) Error estimation and adaptivity for discontinuous failure. International Journal for Numerical Methods in Engineering, 78 (5), April, pp 528-563. ISSN 0029-5981. DOI 10.1002/nme.2495

Mechanics of Materials:

• Gitman IM, Askes H, Kuhl E and Aifantis EC (2010) Stress concentrations in fractured compact bone simulated with a special class of anisotropic gradient elasticity. International Journal of Solids and Structures, 47 (9), May, pp 1099-1107. ISSN 0020-7683. DOI 10.1016/j.ijsolstr.2009.11.020
• Askes H, Metrikine AV, Pichugin AV and Bennett T (2008) Four simplified gradient elasticity models for the simulation of dispersive wave propagation. Philosophical Magazine, 88 (28), October, pp 3415-3443. ISSN 1478-6435. DOI 10.1080/14786430802524108
• Gitman IM, Askes H and Sluys LJ (2008) Coupled-volume multi-scale modelling of quasi-brittle material. European Journal of Mechanics - A/Solids, 27 (3), May, pp 302-327. ISSN 0997-7538. DOI 10.1016/j.euromechsol.2007.10.004

Grants

• 2011: "Spatial and temporal spreading of mine loading using micro-structured truss material" funded by DSTL. Investigators: R Goodall, A Tyas, I Todd, H Askes and JA Warren. Value: £31291.
• 2010-2013: "The influence of microstructure on wave and front propagation through heterogeneous media" funded by Leverhulme Trust. Investigators: WJ Parnell, H Askes, T Bennett and IM Gitman. Value: £228,721.
• 2010-2012: "Bipenalty Method for finite elements and explicit time integration" funded by Royal Society. Investigators: H Askes and A Rodriguez-Ferran. Value: £8800.
• 2009-2012: "Top-down multi-scale modelling strategies for UHMWPE composites" funded by DSTL. Investigators: H Askes and A Tyas. Value: £257,313.
• 2009: "Computational multi-scale modelling of mechanical stimulation of bone" funded by Wellcome Trust. Investigators: IM Gitman, L Yang and H Askes. Value: £68301.
• 2007-2009: "Bridging the Gap between Mathematics, ICT and Engineering Research at Sheffield" funded by EPSRC. Investigators: GW Jewell, J Derrick, A O'Hagan and H Askes. Value: £350,842.
• 2006-2009: "Finite elements for gradient elasticity in statics and dynamics" funded by EPSRC. Investigator: H Askes. Value: £150,430.

Teaching

• CIV 101 – Engineering Mechanics 1
• CIV 215 – Structural Analysis 3 (with Professor Ian Burgess)