REsidual STresses and OPtimisation of Additive Manufaturing. Marie Curie ITN proposal FP7-287287.

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Presentation: Back to INDEX


Additive Manufacturing (AM) is a technique where components are produced layer by layer joined (“glued”) using different techniques depending on the material to be used. This way of production means a complete change of thinking components as there is no need to think of tooling such as moulds to produce such parts. As a consequence the number of parts of assemblies can be reduced by producing the part already assembled. Furthermore parts can be personalised as there is no need to produce a large number of identical parts to divide the cost of tooling. Therefore, there is no benefit in producing the part in a country with low salaries and production can be carried out near the consumer. However, there are several topics which need to be addressed:
• The speed of manufacturing a part is long in comparison to current techniques such as injection moulding. This topic is addressed by many Universities such as Loughborough University and AM machine producers such as MTT (http://www.mtt-group.com/). University of Manchester is together with ESI (http://www.esi-group.com/) working on FP7 Industry-Academia Partnerships and Pathways (IAPP) project INLADE.
• There is a limit of materials available for AM with an increasing research on finding the right “gluing” procedure. IQS (http://www.iqs.edu/) is leading a project to develop multimaterial AM and as a consequence has been working on organising conferences such as http://additivemanufacturingforum.org/.
• The surface obtained by AM needs further treatment for application with low roughness requirements as for example gears. This is a consequence of steps in layering. Reducing the step the roughness improves but increases the time to produce a part. Flubetech (http://www.flubetech.com/) is currently working on several surface treatments transferred from conventional parts to AM parts. KissSoft (http://kisssoft.ch/) produces a software for gears to design the right parameters for conventional materials used by all sort of companies such as NISSAN and Universities such as IQS and UNINORTE (http://www.uninorte.edu.co/).
• Laser welding techniques for steel AM parts lead to complex residual stresses which might increase with the speed of production due to problems of cooling the weld. Unfortunately residual stresses might lead to early fracture of components. University of Bristol (http://www.bristol.ac.uk/mecheng/research/solids/) has a large experience in measurement and prediction of residual stresses. Veqter (http://www.veqter.co.uk/) is a company specialised in the measurement of residual stresses on thick welds.
• Current software for Finite Element Methods are well established for core components but there is a need of software and hardware development for hollow - lattice components which are a great solution for weight optimisation. Several companies are working on software developments to allow the design of lattice components such as Within-lab (http://www.within-lab.com/) which require test validation. University Politecnico de Milano (http://www.mecc.polimi.it/) has been working on simulation and testing of fracture of components.

Objetives: Back to INDEX


1. (ESR1)- Weight optimisation using lattice components with finite element software validation. (WP2-Polimi + Within-lab) Engineering development of components is commonly focused on weight optimisation considering all sorts of load requirements. To achieve this goal engineers use equations to evaluate the change of some parameters in the weight and safety factor to avoid failure of the component. With real complex components equations might be too complex and therefore the engineer requires help from computer aided engineering such as finite elements. Conventional production techniques allow weight optimisation by reducing thickness or introducing some holes in the component. For AM parts weight optimisations can be achieved by producing lattice-hollow components in areas with low load requirements. Within-lab is a company that has been developing a software that suggests some lattice configuration to reduce weight based on several beam structures. The first objective of the project is to define tests of AM parts to validate and improve the software for several mechanical failures defining the methodology to allow weight optimisation. Early-Stage Researchers (ESRs) might receive training on testing (Milano) and simulation (Within-lab).
Animated gif of simulation of bending test.
Animated gif of experimental bending test.
Animated gif of possible optimisation of gears.

2. (ESR2)- Residual stress measurement on AM parts. (WP3-UoB + Veqter) Welded parts are well known to produce residual stresses as a consequence of thermal expansion of hot weld and cooling. One of the major problems is that residual stresses are not visible and therefore might differ in some areas. University of Bristol has developed a technique to measure residual stresses on thick welds at several positions including the effect of depth. The second objective of the project is to measure residual stresses on AM parts considering several techniques and defining the right methodology to know the place with maximum residual stresses. ESRs might receive training on different techniques for residual stress measurement (Veqter) and Finite Element Software (U.Bristol) to simulate residual stresses.
Animated gif of simulation of welding residual stresses.
Animated gif of simulation of residual stresses relaxation at high temperature due to creep.

3. (ESR3)- Speed manufacturing optimisation with residual stresses minimisation. (WP3-MTT + Veqter) Conventional welding defines speed and sorting of welds in order to minimise heat effects and therefore residual stresses. For AM parts the increase of speed leads to powerful laser machines which can be controlled to do the welding strategy to minimise residual stresses. Furthermore, comparison of high speed parameters with creep relaxation need to be addressed. The third objective of the project is to define the right welding strategy to minimise residual stresses for the minimum time to produce a part including the possibility of creep relaxation. ESRs might receive training on machine welding strategies (MTT), deep hole drilling techniques (Veqter) and creep stress relaxation (U.Bristol).
Animated gif of manufacturing simulation by CNC.
Animated gif of manufacturing simulation by injection moulding.
Animated gif of manufacturing simulation by sheetmetal bending.
Animated gif of manufacturing simulation by vertical Additive Manufacturing.
Animated gif of manufacturing simulation by horizontal Additive Manufacturing.

4. (ESR4)- Surface hardness evaluation of AM parts. (WP4- IQS+ESI ) AM parts provide a roughness surface consequence of steps in layer addition. Some techniques require a “glue” for the core and a type of “varnish” to avoid scratching of surface. There is a need to evaluate the roughness and surface hardness for AM parts. The fourth objective of the project is to evaluate surface roughness and hardness of AM parts defining a methodology to know where the part is surface softer. ESRs might receive training on roughness measurements (IQS) and hardness measurements (IQS) and indentation (Flubetech).
Animated gif of simulation of manufacturing process with heating to improve surface quality developed by IQS and ASCAMM.
Animated gif of devide developed between IQS and Flubetech for surface treatment of nanoparticles.
Animated gif of simulation of surface treatment of nanoparticles.

5. (ESR5)- Surface improvement of AM parts. (WP4-Flubetech+ESI) Surface might be improved by heat treatment or surface modification. Application of Physical Vapour Deposition (PVD) or Chemical Vapour Deposition (CVD) on AM parts needs to be evaluated for several combinations of materials and thicknesses. As a fifth objective of the project surface treatment are produced on AM parts defining a methodology to know the best material and thickness. ESRs might receive training on CVD and PVD (Flubetech) and software for surface treatment simulation (ESI).
Animated gif of gear application developed between IQS and Flubetech for Surface treatment.
Animated gif of simulation of impact bending developed between IQS and ESI.

6. (ESR6)- Gear core failure (WP5-IQS+KissSoft) An application of AM parts where weight optimisation, residual stresses and surface effects are critical is a gear. A first approach to gear failure is based on the failure of the core due to bending fatigue. The project should define a test where this failure is expected in order to reproduce it in the lab to understand the failure mechanism for AM parts. All data provided should create a database in order to increase the material library of simulation software with AM materials. As a sixth objective of the project core failure mechanisms of AM gear components should be analysed defining a methodology to avoid such failure. ESRs might receive training on gear core failure (IQS) and software for gears (KissSoft).
Animated gif of gear application.

7. (ESR7)- Gear surface failure (WP5-UniNorte+KissSoft) Most failures of gears start from surface as a lack of lubricant or surface defects. These failures should be addressed with special care in AM parts after some sort of surface improvement. The project should define a test where surface failure is expected in order to reproduce it in the lab to understand the failure mechanism for AM parts. All data provided should create a database in order to increase the material library of simulation software with AM materials. As a seventh objective of the project surface failure mechanisms of AM gear components should be analysed defining a methodology to avoid such failure. ESRs might receive training on gear surface failure (UNINORTE) and software for gears (KissSoft).
Animated gif of gear failure.
Animated gif of possible optimisation of gears.

8. (ER1)- Residual stresses and thickness (WP3-UoB+Veqter) An experienced researcher is expected to address topics from several work packages. The candidate should define tests from AM parts with surface treatment to measure residual stresses. The major problem is to measure residual stresses when in addition to residual stresses from AM there are residual stresses from surface treatment. As an eighth objective of the project residual stresses should be measured on AM parts with surface treatment defining a methodology to know the combined effect. ESRs might receive training on residual stresses software prediction (ESI) and deep hole drilling (Veqter).
Animated gif of design modification due to surface requirements.

Publications: Back to INDEX



• Miquel Domingo-Espin; Josep M. Puigoriol-Forcada; Andres-Amador Garcia-Granada; Jordi Llumà; Salvador Borros; Guillermo Reyes;
"Mechanical property characterization and simulation of fused deposition modeling Polycarbonate parts."
Materials & Design.
Vol. 83 Pag: 670-677 Year: 2015 DOI: http://dx.doi.org/10.1016/j.matdes.2015.06.074

• Miquel Domingo-Espin; Salvador Borros; Nuria Augllo; Andres-Amador Garcia-Granada; Guillermo Reyes;
"Influence of building parameters on the dynamical mechanical properties of Polycarbonate Fused Deposition Modelling parts."
3D Printing and Additive Manufacturing.
Vol.1 N.2 Pag: 70-77 Year: 2014 DOI: 10.1089/3dp.2013.0007

• Lacarac, VD; García-Granada, A.A.; Smith, D.J.; Pavier, M.J.;
"Prediction of the growth rate for fatigue cracks emanating from cold expanded holes"
905974 - International Journal of Fatigue
Vol.26 N.--- Pag: 585-595 Year: 2004 ISSN: 0142-1123

• García-Granada, A.A.; Lacarac, V.D.; Holdway, P.; Smith, D.J.; Pavier, M.J.;
"Creep relaxation of residual stresses around cold expanded holes"
901397 - Journal of Engineering Materials and Technology-Transactions of the Asme
Vol.123 N.--- Pag: 125-131 Year: 2001 ISSN: 0094-4289

• García-Granada, A.A.; Lacarac, V.D.; Smith, D.J.; Pavier, M.J.;
"A new procedure based on Sachs’ boring for measuring non-axisymmetric residual stresses: Experimental Application"
901393 - International Journal of Mechanical Sciences
Vol.43 N.--- Pag: 2753 final: 2768 Year: 2001 ISSN: 0020-7403

• García-Granada, A.A.; Pavier, M.J.; Smith, D.J.;
"A new procedure based on Sachs’ boring for measuring non-axisymmetric residual stresses"
901393 - International Journal of Mechanical Sciences
Vol.42 N.--- Pag: 1027-1047 Year: 2000 ISSN: 0020-7403

• García-Granada, A.A.; Smith, D.J.; Pavier, M.J.;
"Analysis for determining non-axisymmetric residual stresses"
910444 - Materials Science Forum
Vol.347-349 N.--- Pag: 119 final: 124 Year: 2000 ISSN: 0255-5476

• Lacarac,V.D.; García-Granada, A.A.; Smith, D.J.; Pavier, M.J.;
"Experimental measurement of non-axisymmetric residual stresses"
910444 - Materials Science Forum
Vol.347-349 N.--- Pag: 125-130 Year: 2000 ISSN: 0255-5476

• Pavier, M.J.; Garcia-Granada, A.A.; Lacarac, V.D.; Smith D.J.;
"Growth of Fatigue Cracks from Cold Expanded Holes"
Proceedings of International Conference of Fracture
Vol. --- N.--- Pag: ------- Year: 2001 Place of publication: Honolulu, Hawaii (ESTATS UNITS D'AMÈRICA) ISBN: ---

• García-Granada, A.A.; Lacarac, V.D.; Smith, D.J.; Pavier, M.J.; Cook, R.; and Holdway, P.;
"3D residual stresses around cold expanded holes in a new creep resistant aluminium alloy"
Proc. 4th International Conf. on Computer Methods and Experimental Measurements for Surface Treatment Effects
Vol. --- N.--- Pag: 103-116 Year: 2000 Place of publication: Assissi (ITÀLIA) ISBN: ---

• Lacarac,V.D.; García-Granada, A.A.; Smith, D.J.; Pavier, M.J.;
"The effect of creep on residual stress relaxation around cold expanded holes"
Proceedings of the 6th International Conference on Residual Stresses, 10-12 Jul. 2000, Oxford, U.K
Vol. --- N.--- Pag: ------- Year: 2000 Place of publication: Oxford (UK) ISBN: ---

• García-Granada, A.A.; George, D.; Smith, D.J.;
"Assessment of distortions in the deep hole technique for measuring residual stresses"
Proceedings of the 11th Int. Conference on Experimental Mechanics, 24-28 Aug. 1998, Oxford, U.K.
Vol. --- N.--- Pag: 1301-1306 Year: 1998 Place of publication: Oxford (UK) ISBN: ---

Contact: Back to INDEX


For any queries do not hesitate to contact:
Andres-Amador Garcia-Granada:
Via Augusta 390, 08017 Barcelona, Spain
Tel.: +34 932 672 083 / Tel.Cen.: +34 932 672 000 -ext.283
Fax: +34 932 056 266
andres.garcia@iqs.edu
www.iqs.edu
  
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