Metal Forming and Material Processing

In close collaboration with academic and industrial partners and with a focus for aerospace, automotive and medical application, the research team carries out fundamental and applied research in the following areas:

New flexible and hybrid material forming processes
Process modelling and optimisation
Material characterisation, constitutive models, formability and fracture

Friction stir welding and processing of lightweight materials
Tribological behaviour in bulk and sheet forming processes

Projects

Developing a Bespoke Incremental Sheet Forming Machine for Cranioplasty

EPSRC research grant: 2014-2018, £299k

Principal investigator: Dr Hengan Ou

Project partners:

Delcam International plc
Labman Automation Ltd
Shanghai Jiao Tong University
UCL Hospitals NHS Trust

Project summary: Cranioplasty is a surgical procedure for the repair of deformity of a human skull due to brain tumour, stroke or traumatic injuries. Among all available materials, titanium continues to be a main stream material used in cranioplasty surgeries because of its excellent biocompatibility, resistance to infection, excellent material properties and lightweight. However, in spite of the popular use of titanium in cranial reconstruction, there is a wide variety of methods including casting, manual shaping and rubber press forming commonly used in cranial plate manufacture.

Even with the assistance of advanced CAD/CAM (computer-aided design and manufacture) and computed tomographic (CT) and magnetic resonance imaging (MRI) technologies, currently the process for manufacturing customised cranial plates by conventional methods normally takes up to two weeks to completion mainly due to the time required for the manufacture of dies and tools.

This project aims to develop an incremental sheet forming (ISF) based process for fast and cost effective manufacture of personalised cranial plates. Our recent work has shown that a typically large size cranial plate can be made satisfactorily by using the ISF process in less than 30 minutes instead of hours or days. The objectives of the project are to

Develop in-depth understanding of titanium ISF formability, deformation and failure mechanisms and to develop predictive models and novel tool path optimisation algorithms
Design and build a bespoke desktop ISF machine for cranial reconstruction with clearly defined technical specifications
Conduct a series of ISF benchmark testing and pre-clinical trials of 3 demonstration case studies
Disseminate research outcomes and to engage with wider academic and industrial communities as well as end users

Incremental Sheet Forming to Manufacture PEEK Cranial Plates

EPSRC MeDe Fresh Idea grant: 2015-2016, £49k

Principal investigator: Dr Hengan Ou

Project summary: PEEK (polyetheretherketone) has been increasingly used in medical implants including cranioplasty surgeries in recent years. With the support of the EPSRC Centre for Innovative Manufacturing in Medical Devices Fresh Idea fund, the project aims to develop a heat assisted incremental sheet forming (ISF) to manufacture large scale PEEK cranial plates.

ISF is a flexible sheet forming process requiring minimum use of tooling and is easy for automation. ISF has been proven to be an effective means to manufacture large scale titanium cranial plates. By carrying out extensive PEEK material testing and ISF trials, this project aims to demonstrate the technical feasibility and potential benefits of the ISF process as a novel alternative method for manufacturing PEEK cranial plates. The specific project objectives are to

Investigate ISF formability and deformation mechanisms of PEEK material
Develop bespoke ISF tooling and apparatus for ISF processing PEEK cranial plates
Disseminate research outcomes and to develop further funding programmes for collaborative research and knowledge transfer

FE Simulation and Optimisation of Multi-Stage Deep Drawing Processes for Precision Components

Innovate-UK KTP grant with Advanex Europe: 2017-2019, £151,808

Principal investigator: Dr Hengan Ou

Co-investigator: Prof Atanas Popov

Project summary: Advanex Europe Ltd is a market leader specialising in precision engineering solutions for high value metal and plastic components to supply a diverse range of markets from agriculture and automotive through to medical and aerospace. The main objectives of this Innovate-UK project are to

Develop advanced FE simulation algorithms to ensure a high level of fidelity and efficiency of FE simulation of multi-stage deep drawing operations
Develop an integrated optimisation framework that can be used to assist multi-stage deep drawing process design and operations
Implement the FE simulation capabilities and integrated optimisation tool in actual production with consideration of material and process variability throughout multi-stage operations

New Material Processing Technologies for Sustainable Future

EC/FP7 Marie Curie IRSES (MatProFuture) project: 2013-2017, €739k

Principal investigator: Dr Hengan Ou

Co-investigators: Prof Adib Becker and Prof Wei Sun

Project coordinator: University of Nottingham (UK)

Project partners:

University of Palermo (Italy)
University of Erlangen-Nuremberg (Germany)
University of Sheffield (UK)
Huazhong University of Science and Technology (China)
Northwestern Polytechnical University (China)
Harbin Institute of Technology (China)
Shanghai JiaoTong University (China)
Wuhan University of Technology (China)
South China University of Technology (China)

Project summary: Development of new energy efficient, environment friendly and cost effective material processing technologies for manufacturing of high value products is of considerable importance to sustained economic recovery and growth of Europe and around the globe. Supported by the EC FP7 Marie Curie IRSES (International Research Staff Exchange Scheme) funding, the MatProFuture (New Material Processing Technologies for Sustainable Future, project no: 318968) project assembles 4 EU and 6 Chinese leading universities and aims to establish new research links and to develop new materials processing technologies through extensive research staff exchange and knowledge transfer activities between participating institutions in Europe and China. The overall objectives of the MatProFuture project were to

Carry out collaborative research and joint activities in the field of new material processing technologies for stimulated creativity and innovative solutions and identified areas for industrial application;
Exchange experienced staff and talented young researchers at various levels for transfer of knowledge and skills through various forms of activities including organisation of seminars/workshops, summer schools and high profile conferences;
Disseminate high quality research and to establish long-term collaboration through joint research programmes and collaborative projects with a wider participation of research communities, SMEs and OEMs from different industrial sectors.

WP1 Developing New Sustainable Materials Processing Technologies

MatProFuture project work packages & activities

Since the inception of the MatProFuture project, 113 experienced (ER) and early-stage (ESR) researchers have participated in 299 man-months research staff exchange and secondments between MatProFuture partner institutions. The completed staff exchange and secondment activities are a direct result of collective effort by and active participation of researchers from all MatProFuture project partners. Significant progresses have been made in training of early-stage researchers, generation and dissemination of research outcomes in five focused research areas: new sheet forming processes, precision forging, integrated joining and forming, novel spinning and new hydroforming processes.

During the MatProFuture project, 2 MatProFuture special sessions were organised in international conferences. 6 MatProFuture summer schools and research seminars were organised. To the end of MatProFuture project, a total 45 journal papers have been published and 12 presentations have been given in international conferences. Further 10 journal papers have been submitted under consideration for publication and 7 papers have been submitted to international conferences. These successful collaboration and dissemination activities have had a positive impact for MatProFuture project partners to continue their established links and to develop an excellent platform for long-term collaboration in the emerging field of new and high value materials processing and forming technologies.

Key contacts

Dr Hengan Ou

Phd Students:

Mr Wenxuan Peng
Miss Xuelei Zhao
Mr Hui Zhu

Past Members:

Mr Shakir Gatea
Mr Omar Al-Jumaili
Dr Fei Chen
Dr Amar Behera

Research themes

New Flexible and Hybrid Material Forming Processes

Flexible forming is characterised by localised plastic deformation of the material without the need of special tooling and expensive machines, whilst hybrid forming is achieved by simultaneous or sequential use of different mechanisms or energy sources for much improved processing quality and efficiency of high value products. Under UK EPSRC, Innovate-UK and EU Marie Curie funding and in close collaboration with national and international partners, research has been carried out in a number of areas including

Single point and double side incremental sheet forming of pure titanium sheet for cranioplastyCranioplasty is a surgical procedure for the repair of a deformity of the human skull. ISF based cranial reconstruction & ISF manufacturing of cranial plates with significant amount of reduction in both lead-time and manufacturing cost.

Reconstruction for ISF based cranial plate

Reconstructionfor ISF based cranial manufacturing from CT/MRI data

ISF for titanium cranial plate

ISF for titantium Cranial plate

Heat assisted incremental sheet forming of titanium alloy and PEEK materialsA novel heat-assisted apparatus has been developed so that ISF can be used to form PEEK and other polymeric materials.

Heat-assisted ISF for PEEK material

ISF formed PEEK plates

ISF formed PEEK Plates

Development of new generation of bespoke ISF machines

Research papers:

B. Lu, M.W. Mohamed Bazeer, H. Long, J.F. Cao and H. Ou, “A study of incremental sheet forming by using water jet”, International Journal of Advanced Manufacturing Technology (published on-line)
S. Ai, B. Lu, J. Chen, H. Long and H. Ou, “Evaluation of deformation stability and fracture mechanism in incremental sheet forming”, International Journal of Mechanical Sciences , Vol.124-125, pp174-184
A.K. Behera and H. Ou (2017), “Effect of stress relieving heat treatment on surface finish and dimensional accuracy of incrementally formed grade 1 titanium sheet parts”, International Journal of Advanced Manufacturing Technology, Vol. 87(9), pp3233-3284.
S. Gatea, H. Ou and G McCartney (2016), “Review on the influence of process parameters in incremental sheet forming”, International Journal of Advanced Manufacturing Technology, Vol. 87(1), pp479-499.
T.T. Cao, B. Lu, H. Ou, H. Long and J. Chen (2016), “Investigation on a new hole-flanging approach by incremental sheet forming through a featured tool”, International Journal of Machine Tools and Manufacture, Vol. 110, pp1-17.
B. Lu, H Ou, S.Q Ying, H. Long and J. Chen (2016), “Titanium Based Cranial Reconstruction using Incremental Sheet Forming”, International Journal of Material Forming, Vol.9(3), pp361-370.
A.K. Behera, B. Lu and H. Ou (2016), “Characterization of shape and dimensional accuracy of incrementally formed titanium sheet parts with intermediate curvatures between two feature types”, International Journal of Advanced Manufacturing Technology, Vol.83, pp1099-1111.
M.H. Zhang, B. Lu, J. Chen, H. Long and H. Ou (2015), “Selective element fission approach for fast FEM simulation of incremental sheet forming based on dual-mesh system”, International Journal of Advanced Manufacturing Technology, Vol. 78(5-8), pp1147-1160.
B. Lu, Y. Fang, D.K. Xu, J. Chen, A. Sheng, H. Long, H. Ou and J. Cao (2015), “Investigation of deformation mechanism of double side incremental sheet forming process”, International Journal of Machine Tools and Manufacture, Vol.93, pp37-48.
B. Lu, D.K Xu, R.Z. Liu, H. Ou, H. Long and J. Chen (2015), “Cranial Reconstruction using Double Side Incremental Forming”, Key Engineering Materials, Vol. 639, pp535-542.
B. Lu, Y. Fang, D.K. Xu, J Chen, H. Ou, N.H. Moser and J. Cao (2014), “Investigation of friction effect in single point incremental forming process for aluminum alloys using oblique roller-ball tool”, International Journal of Machine Tools and Manufacture, Vol. 85, pp14-19.
Y. Fang, B. Lu, J Chen, D.K. Xu and H. Ou (2014), “Analytical and experimental investigations on deformation mechanism and fracture behaviour in single point incremental forming”, Journal of Materials Processing Technology, Vol. 214(8), pp1503-1515.
B. Lu, J. Chen, H. Ou and J, Cao (2013), “Feature-based tool path generation approach for incremental sheet forming process”, Journal of Materials Processing Technology, Vol. 213, pp1221-1233.

Process Modelling and Optimisation

Hot precision forging is a competitive route for manufacturing of high temperature alloy aerofoil blades for aeroengine applications. To satisfy the ever increasing demand for improved reliability, durability and performance, as well as reduced cost and weight for aeroengine technologies, net-shape specification of forged aerofoil blades is an essential requirement in forging design and production together with other criteria including sufficient mechanical properties and minimal material loss. Under EPSRC, EC/FP and industrial funding support, significant progress has been made in developing

new algorithms and methods for accurate quantification of dimensional and shape errors due to die- and press-elasticity, thermal distortion and trimming operation
A novel compensation approach for net-shape accuracy with the consideration of uncertainties
Aframework of virtual inspection for effective validation of forging simulation and optimisation results with practical measurement procedures

Deformation characteristics of a 1000T press

Deformation characteristics of a 1000T press [6,12,13]

Forging error quantification

Forging error quantification [5,6,11]

A two-step stochastic forging optimisation for minimised systematic

A two-step stochastic forging optimisation for minimised systematic errors and reduction of variations [7,10]

Research papers:

Y. Shao, B. Lu, D.K. Xu, J. Chen, H. Ou, H. Long and P.Y. Guo (2016), “Topology-based preform design optimization for blade forging”, International Journal of Advanced Manufacturing Technology, vol. 86, pp1593-1605.
Y. Shao, B. Lu, H. Ou and J. Chen (2015), “A new approach of preform design for forging of 3D blade based evolutionary structural optimization”, Structural and Multidisciplinary Optimization, Vol. 51(1), pp199-211.
Y. Shao, B. Lu, H. Ou, F. Ren and J. Chen, (2014) “Evolutionary Forging Optimization Using Strain based Criterion”, International Journal of Advanced Manufacturing Technology, Vol. 71(1-4), pp69-80.
J. Makem, H. Ou, C.G. Armstrong (2012), “A Virtual Inspection Framework for Precision Manufacturing of Aerofoil Components”, Computer-Aided Design, Vol. 44(9), pp858-874.
5. B. Lu and H. Ou (2012), “An Efficient Approach for Trimming Simulation of 3D Forged Components”, International Journal of Mechanical Sciences, Vol. 55(1), pp30-41.
B. Lu and H. Ou (2012), “Quantification of Press Elasticity in Precision Forging of 3D Complex Shapes”, Proc. IMechE, Part B, Journal of Engineering Manufacture, Vol. 226(3), pp466-477.
H. Ou, P. Wang, B. Lu and H Long (2012), “Finite Element Modelling and Optimisation of Net-Shape Metal Forming Processes with Uncertainties”, Computers and Structures, Vols 90-91, pp13-27.
B. Lu, H. Ou and Z.S. Cui (2011), “Shape Optimisation of Preform Design for Precision Close-Die Forging”, Structural and Multidisciplinary Optimization. Vol. 44(6), pp785-796.
B. Lu, H. Ou and H Long (2011), “Die shape optimisation for net-shape accuracy in metal forming using direct search and localised response surface methods”, Structural and Multidisciplinary Optimization, Vol. 44(4), pp529-545.
B. Lu and H. Ou (2011), “Stochastic Finite Element Modelling and Optimisation for Net-Shape Forging of 3D Aeroengine Blades”, Proc. IMechE, Part L, Journal of Materials: Design & Applications, Vol 225(2), pp71-85.
B. Lu, H. Ou, C.G. Armstrong and A. Rennie (2009), “3D Die Shape Optimisation for Net-Shape Forging of Aerofoil Blades”, Materials & Design, Vol 30(7), pp2490-2500.
H. Ou and C.G. Armstrong (2006), "The Effect of Press Elasticity in Forging of Aerofoil Sections Using Finite Element Simulation", Finite Elements in Analysis and Design, Vol. 42(10), pp856-867.
H. Ou (2006), "Prediction of Dimensional Errors in 3D Complex Shapes due to Press Elasticity", International Journal of Advanced Manufacturing Technology, Vol. 31(1-2), pp61-70.
H. Ou, J. Lan, C.G. Armstrong, M.A. Price, S.J. Walløe and M.J. Ward (2006), "Reduction in Post Forging Errors for Aerofoil Forging Using Finite Element Simulation and Optimisation", Modelling and Simulation in Materials Science and Engineering, Vol. 14(2), pp179-193.
H. Ou, J. Lan, C.G. Armstrong and M.A. Price (2004), "A FE Simulation and Optimisation Approach for Forging of Aeroengine Components", Journal of Materials Processing Technology, Vol. 151, pp208-216.

Material Characterisation, Constitutive Models, Microstructural Evolution, Formability and Fracture

Successful forming of components for specified material and mechanical properties is depended upon in-depth understanding of material deformation behaviour, development of representative constitutive models and effective methods for evaluation of microstructural evolution and prediction of formability and facture under different deformation conditions. Under EPSRC funding and in collaboration with academic partners, work has been carried out to characterise deformation behaviour and to develop constitutive models of metallic (e.g. Ti and Ni alloys) and non-metallic (e.g. PEEK) materials. A modified Gurson-Tvergaard- Needleman (GTN) model with the consideration of shear, strain rate and stress triaxiality has been developed to predict ductile fracture and formability in incremental sheet forming of pure titanium parts for medical applications.

Flow stress behaviour of IN718 alloy under hot deformation condition

Flow stress behaviour of IN718 alloy under hot deformation condition

IN718 Superalloy microstructures at different temperatures and strain rates

Deformation and fracture characteristics and constitutive modelling of polyether-ether-ketone (PEEK)

$Deformation and fracture characteristics$

Experimental testing of PEEK specimen under elevated temperature [1]

$SEM fractograph of a notched PEEK$

SEM fractograph of a notched PEEK specimen with a radius of 1.0mm [4]

A GTN based model for the prediction of ductile fracture and formability in ISF of pure Ti components

Tensile test for GTN model parameters using DIC system

Tensile test for GTN model parameters using DIC system [6]

$SEM fractographs determining VVF 1$

SEM fractographs for determining VVF (void volume fracture) at different stages under tensile condition

ISF testing and FE simulation of a hyperbolic pyramid

ISF testing and FE simulation of hyperbolic cone with

ISF testing and FE simulation of hyperbolic cone with different tool sizes

Research papers:

F. Chen, H. Ou, S. Gatea and H. Long, “Hot tensile fracture characteristics and constitutive modelling of polyether-ether-ketone”, Polymer testing (to appear)
F. Chen, H. Ou, Z.S. Cui and H. Long (2016), “Mesoscale simulation of microstructural evolution during dynamic recrystallization in Ni-based superalloy”, Applied Physics A–Materials Science and Processing, Vol. 122(10):890, pp1-13
F. Chen, J. Liu, H. Ou, B. Lu and Z.S. Cui (2015), “Flow characteristics and intrinsic workability of IN718 superalloy”, Materials Science and Engineering A, Vol. 642, pp279-287
F. Chen, S. Gatea, H. Ou, B. Lu and H. Long (2016), “Fracture characteristics of PEEK at various stress triaxialities”, Journal of the Mechanical Behavior of Biomedical Materials, Vol.64, pp173-186
F. Chen, H. Ou, B. Lu and H. Long (2016), “A constitutive model of polyether-ether-ketone (PEEK)”, Journal of the Mechanical Behavior of Biomedical Materials, Vol. 53, pp427-433
S. Gatea, B. Lu, H. Ou and G. McCartney (2015), “Numerical simulation and experimental investigation of ductile fracture in SPIF using modified GTN model”, Proc. 4th International Conference on New Forming Technology (ICNFT2015), Aug., Glasgow, UK.

Friction Stir Welding and Processing of Lightweight Materials

Friction stir welding (FSW) is a proven technique to join similar and dissimilar materials. Friction Stir Processing (FSP) is a new concept for processing materials with improved material and mechanical properties. Work has been carried out to join Aluminium alloy and Aluminium Matrix Composite (AMC) materials using FSW and in developing new FSP techniques for improved microstructure and mechanical properties.

Experimental set up for FSW of Al alloy

Experimental testing and FE simulation of Surface mechanical

Experimental testing and FE simulation of Surface mechanical grinding treatment (SMGT) for grain refinement

Research papers:

B. Lu, Z.H. Li, H. Long, F. Chen, J. Chen and H. Ou (2017), “Microstructure refinement by tool rotation-induced vibration in incremental sheet forming”, Procedia Engineering (Proc. ICTP 2-17 conf.) to appear.
D. Zhao, J.D. Deng, H.J. Mao, D.S. Qian and H. Ou (2017), “Simulation and experiment study on flow forming of inner-splined flange”, Procedia Engineering (Proc. ICTP 2-17 conf.) to appear.
C.R. Chen, Y. Wang and H. Ou (2016), “Study of weld characteristics for repair using sequential experimental design and artificial neural networks”, International Journal of Advanced Manufacturing Technology, Vol.84, pp1313–1323.
O.S. Salih, H. Ou, W. Sun and D.G McCartney (2015), “A review of friction stir welding of aluminium metal matrix composites”, Materials and Design, Vol. 86, pp61-71.

Tribological Behaviour in Bulk and Sheet Forming Processes

Friction plays an important role in bulk and sheet metal forming processes. Effective and accurate measurement of friction coefficient/factor is essential for the design and accurate FE simulation or analytical evaluation of a specific forming process. Recent work has led to the proposal of two new configurations that can be used in ring compression tests for friction under bulk forming conditions. Effort has also been carried out to assess the effect of friction in incremental sheet forming process.

New ring compression tests with inner and outer boss

Ring compression test with inner boss concept

Ring compression test with inner boss concept, tested samples and measured friction factors of four lubrication conditions plotted on the calibration curves [1] Ring compression test with outer boss concept and a tested sample without lubrication

Ring compression test with outer boss concept and a tested sample without lubrication [3]

Measurement of friction in incremental sheet forming

ISF testing apparatus and normal and tangential force measurement data using a rigid and a ball tool

Research papers:

C.L. Hu, Q. Yin, Z. Zhao and H. Ou (2017), “A new measuring method for friction factor by using ring with inner boss compression test”, International Journal of Mechanical Sciences, Vol. 123, pp133-140.
D.W. Zhang and H. Ou (2016), “Relationship between friction parameters in Coulomb-Tresca friction model for bulk metal forming”, Tribology International, Vol. 95, pp13-18
C. Hu, H. Ou and Z. Zhao (2015), “An alternative method for evaluating friction conditions in cold forging by compression of ring with boss”, Journal of Materials Processing Technology, Vol.224, pp18-425.
C. Hu, H. Ou and Z. Zhao (2015), “Investigation of tribological condition in cold forging using an optimal spike forging test”, Advances in Mechanical Engineering, Vol. 7(5), pp1-11.
T. Robinson, H. Ou and C.G. Armstrong (2004), "Study on Ring Compression Test Using Physical Modelling and FE Simulation", Journal of Materials Processing Technology, Vol. 153-154, pp54-59.

Metal Forming and Material Processing

Projects

Key contacts

Research themes

Advanced Manufacturing Technology Research Group

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