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Odenberger, Eva-Lis
Alternative names
Publications (10 of 14) Show all publications
Pérez Caro, L., Schill, M., Haller, K., Odenberger, E.-L. & Oldenburg, M. (2019). Damage and fracture during sheet-metal forming of alloy 718. International Journal of Material Forming
Open this publication in new window or tab >>Damage and fracture during sheet-metal forming of alloy 718
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2019 (English)In: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214Article in journal (Refereed) Epub ahead of print
Abstract [en]

Forming nickel-based superalloy aero-engine components is a challenging process, largely because of the risk of high degree of springback and issues with formability. In the forming tests conducted on alloy 718 at room temperature, open fractures are observed in the drawbead regions, which are not predicted while evaluating the formability using the traditional forming-limit diagram(FLD). This highlights the importance of an accurate prediction of failure during forming as, in some cases, may severely influence the springback and thereby the accuracy of the predicted shape distortions, leading the final shape of the formed component out of tolerance. In this study, the generalised incremental stress-state dependent damage model (GISSMO) is coupled with the isotropic von Mises and the anisotropic Barlat Yld2000-2D yield criteria to predict the material failure in the forming simulations conducted on alloy 718 using LS-DYNA. Their effect on the predicted effective plastic strains and shape deviations is discussed. The failure and instability strains needed to calibrate the GISSMO are directly obtained from digital image correlation (DIC) measurements in four different specimen geometries i.e. tensile, plane strain, shear, and biaxial. The damage distribution over the drawbeads is measured using a non-linear acoustic technique for validation purposes. The numerical simulations accurately predict failure at the same regions as those observed in the experimental forming tests. The expected distribution of the damage over the drawbeads is in accordance with the experimental measurements. The results highlight the potential of considering DIC to calibrate the GISSMO in combination with an anisotropic material model for forming simulations in alloy 718.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
alloy 718, damage, fracture, GISSMO, non-linear acoustic technique, optimisation
National Category
Metallurgy and Metallic Materials Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62903 (URN)10.1007/s12289-018-01461-4 (DOI)
Projects
Virtual process chain for superalloy sheet metal aero engine structures - Validation and demonstrator (NFFP6)
Funder
Vinnova, 2013-01173
Available from: 2017-04-05 Created: 2017-04-05 Last updated: 2019-10-07
Odenberger, E.-L., Pederson, R. & Oldenburg, M. (2019). Finite element modeling and validation of springback and stress relaxation in the thermo-mechanical forming of thin Ti-6Al-4V sheets. The International Journal of Advanced Manufacturing Technology
Open this publication in new window or tab >>Finite element modeling and validation of springback and stress relaxation in the thermo-mechanical forming of thin Ti-6Al-4V sheets
2019 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015Article in journal (Refereed) Epub ahead of print
Abstract [en]

In this work, a hot forming procedure is developed using computer-aided engineering (CAE) to produce thin Ti-6Al-4V sheet components in an effective way. Traditional forming methods involve time- and cost-consuming furnace heating and subsequent hot sizing steps. A material model for finite element (FE) analyses of sheet metal forming and springback at elevated temperatures in Ti-6Al-4V is calibrated and evaluated. The anisotropic yield criterion proposed by Barlat et al. 2003 is applied, and the time- and temperature-dependent stress relaxation behavior for elastic and inelastic straining are modeled using a Zener–Wert–Avrami formulation. Thermo-mechanical uniaxial tensile tests, a biaxial test, and uniaxial stress relaxation tests are performed and used as experimental reference to identify material model parameters at temperatures up to 700 °C. The hot forming tool setup is manufactured and used to produce double-curved aero engine components at 700 °C with different cycle times for validation purposes. Correlations between the predicted and measured responses such as springback and shape deviation show promising agreement, also when the forming and subsequent holding time was as low as 150 s. The short cycle time resulted in elimination of a detectable alpha case layer. Also, the tool surface coating extends the tool life in combination with a suitable lubricant. 

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Hot forming, Stress relaxation, Springback, Ti-6Al-4V, Plastic anisotropy, FE analysis
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-75356 (URN)10.1007/s00170-019-04071-9 (DOI)
Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2019-07-24
Odenberger, E.-L., Pérez Caro, L., Åhlin, H. & Oldenburg, M. (2018). Thermo-mechanical Material Characterization and Stretch-bend Forming of AA6016. Paper presented at International Deep Drawing Research Group 37th Annual Conference 3–7 June 2018, University of Waterloo, Waterloo, Ontario, Canada. IOP Conference Series: Materials Science and Engineering, 418, Article ID 012022.
Open this publication in new window or tab >>Thermo-mechanical Material Characterization and Stretch-bend Forming of AA6016
2018 (English)In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 418, article id 012022Article in journal (Refereed) Published
Abstract [en]

Lightweight design has become increasingly in focus for the manufacturing industry. Global environmental challenges, goals and legislations imply that lighter and sustainable products are imperative to remain competitive. One example is stamped products made of aluminum alloys which are of interest to the automotive industry, where lightweight designs are essential. In order to increase formability and to produce more complex geometries in stamped aluminum components there is a need to develop hot forming techniques. The Finite Element Method (FEM) has enabled important advances in the study and design of competitive manufacturing procedures for metal parts. Predicting the final geometry of a component is a complex task, especially if the forming procedure occurs at elevated temperatures. This work presents selected results from thermo-mechanical material testing procedures, FE-analyses and forming validation tests in AA6016 material. The material tests are used to determine the thermo-mechanical anisotropic properties, strain rate sensitivity and formability (Forming Limit Curves, FLC) at temperatures up to 490°C. Stretch-bending tests are performed to compare predicted results with experimental observations such as punch force, strain levels, thinning, forming temperatures, springback and failure. It was found that the heat-treatment and forming at elevated temperatures substantially increased formability and that measured responses could in general be predicted if care was taken to model the initial blank temperatures, heat transfer and thermo-mechanical material properties. The room temperature case confirms the importance of considering anisotropy.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2018
National Category
Applied Mechanics Other Civil Engineering
Research subject
Solid Mechanics; Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-71364 (URN)10.1088/1757-899X/418/1/012022 (DOI)2-s2.0-85054260019 (Scopus ID)
Conference
International Deep Drawing Research Group 37th Annual Conference 3–7 June 2018, University of Waterloo, Waterloo, Ontario, Canada
Note

Konferensartikel i tidskrift;2018-10-30 (svasva)

Available from: 2018-10-30 Created: 2018-10-30 Last updated: 2019-01-11Bibliographically approved
Odenberger, E.-L., Thilderkvist, P. & Oldenburg, M. (2014). Springback and stress relaxation in thermo-mechanical forming of thin Ti-6Al-4v sheets (ed.). Paper presented at The International Symposium on Plasticity and its Current Applications : 03/01/2014 - 08/01/2014. Paper presented at The International Symposium on Plasticity and its Current Applications : 03/01/2014 - 08/01/2014.
Open this publication in new window or tab >>Springback and stress relaxation in thermo-mechanical forming of thin Ti-6Al-4v sheets
2014 (English)Conference paper, Oral presentation only (Refereed)
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-34786 (URN)912bf0a4-9250-4796-8d58-ce2842ad239d (Local ID)912bf0a4-9250-4796-8d58-ce2842ad239d (Archive number)912bf0a4-9250-4796-8d58-ce2842ad239d (OAI)
Conference
The International Symposium on Plasticity and its Current Applications : 03/01/2014 - 08/01/2014
Note
Godkänd; 2014; 20140114 (evawes)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Odenberger, E.-L., Oldenburg, M. & Niklasson, F. (2013). Direct-hit development of manufacturing processes: Thermo-mechanical forming of Titanium aero engine structures (ed.). In: (Ed.), (Ed.), Book of Abstracts for the 4:th CEAS Conference, 2013: . Paper presented at The International Conference of the European Aerospace Scocieties : 16/09/2013 - 19/09/2013 (pp. 175). Linköping: Linkoping University Electronic Press
Open this publication in new window or tab >>Direct-hit development of manufacturing processes: Thermo-mechanical forming of Titanium aero engine structures
2013 (English)In: Book of Abstracts for the 4:th CEAS Conference, 2013, Linköping: Linkoping University Electronic Press , 2013, p. 175-Conference paper, Meeting abstract (Refereed)
Abstract [en]

In order to increase the competitiveness of the Swedish aerospace industry, alternative manufacturing processes for static load carrying aero engine structures are desired. Presently, these components mainly consist of large-scaled single castings. To increase the in-house level of processing, the Swedish aero engine industry focus on fabricated alternatives by introducing new manufacturing processes and create relations with adjacent sub-suppliers. Theconcept of fabrication involves forgings, sheet metals and small ingots assembled by welding. The possibility to reduce weight, i.e. fuel consumption and product cost also exists. In the aerospace industry extremely highdemands on safety and reliability exists which requires precise knowledge regarding the influence on the material and its properties through the whole fabrication chain. The advanced Finite Element (FE) technology makes precise analyses possible assuming that proper material descriptions are used. Analyses of sheet metal forming provides with information of formability, thinning, springback, resultant mechanical properties and residual stress state which are important input to analyses of subsequent welding and heat treatments. One challenge in producing complete structures based on fabrication isrelated to the accuracy in numerical predictions of shape deviation using FE-analyses, in order to effectively compensate forming tools forspringback and accumulated shape distortions. By fundamental research on and development of thermo-mechanical processes for hot sheet metal forming of titanium, this project shall result in that a few SME can further developtheir processes for product and process development. The project gather competence from the Swedish aero engine industry GKN Aerospace, acknowledged R&D within forming processes, FE-modelling and SME withexperience of forming. The aims of the project are:Development of methodologies for thermomechanical material characterisation of Ti-6Al- 4V and FE-models for hot sheet metal forming. Suggestion of forming procedures suitable for production of titanium components in which resultant geometry and properties are secured.Activities where Swedish SME takes necessary development steps, in order to produce desired titanium sheet metal parts and develop into new sub-suppliers for the Aero engine industry. This presentation summarise results obtained inpresent and previous research and development projects regarding short lead time design, compensation and manufacturing of deep drawing tools of titanium and super alloys. The research funding by VINNOVA - NFFP 4 and 5for SME, BFS and GKN Aerospace Sweden are gratefully acknowledged.

Place, publisher, year, edition, pages
Linköping: Linkoping University Electronic Press, 2013
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-39065 (URN)da8be1c6-8d8a-4ff5-9708-1afb6ea0e65e (Local ID)978-91-7519-520-9 (ISBN)da8be1c6-8d8a-4ff5-9708-1afb6ea0e65e (Archive number)da8be1c6-8d8a-4ff5-9708-1afb6ea0e65e (OAI)
Conference
The International Conference of the European Aerospace Scocieties : 16/09/2013 - 19/09/2013
Note
Godkänd; 2013; 20140114 (evawes)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Odenberger, E.-L., Hertzman, J., Thilderkvist, P., Merklein, M., Kuppert, A., Stöhr, B., . . . Oldenburg, M. (2013). Thermo-mechanical sheet metal forming of aero engine components in Ti-6Al-4V: Part 1: Material characterisation (ed.). Paper presented at . International Journal of Material Forming, 6(3), 391-402
Open this publication in new window or tab >>Thermo-mechanical sheet metal forming of aero engine components in Ti-6Al-4V: Part 1: Material characterisation
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2013 (English)In: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214, Vol. 6, no 3, p. 391-402Article in journal (Refereed) Published
Abstract [en]

Ti-6Al-4V is one of the most frequently used titanium alloy in aerospace applications such as for load carrying engine structures, due to their high strength to weight ratio in combination with favourable creep resistance at moderate operating temperatures. In the virtual development process of designing suitable thermo-mechanical forming processes for titanium sheet metal components in aero engine applications numerical finite element (FE) simulations are desirable to perform. The benefit is related to the ability of securing forming concepts with respect to shape deviation, thinning and strain localisation. The reliability of the numerical simulations depends on both models and methods used as well as on the accuracy and applicability of the material input data. The material model and related property data need to be consistent with the conditions of the material in the studied thermo-mechanical forming process. In the present work a set of material tests are performed on Ti-6Al-4V at temperatures ranging from room temperature up to 560°C. The purpose is to study the mechanical properties of the specific batch of alloy but foremost to identify necessary material model requirements and generate experimental reference data for model calibration in order to perform FE-analyses of sheet metal forming at elevated temperatures in Ti-6Al-4V.

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-4164 (URN)10.1007/s12289-012-1093-8 (DOI)000323246800006 ()2-s2.0-84881614342 (Scopus ID)20e76bae-7e41-4fa2-bde8-af8c7bce06f5 (Local ID)20e76bae-7e41-4fa2-bde8-af8c7bce06f5 (Archive number)20e76bae-7e41-4fa2-bde8-af8c7bce06f5 (OAI)
Note
Validerad; 2013; 20120308 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Odenberger, E.-L., Schill, M. & Oldenburg, M. (2013). Thermo-mechanical sheet metal forming of aero engine components in Ti-6Al-4V: Part 2 : Constitutive modelling and validation (ed.). Paper presented at . International Journal of Material Forming, 6(3), 403-416
Open this publication in new window or tab >>Thermo-mechanical sheet metal forming of aero engine components in Ti-6Al-4V: Part 2 : Constitutive modelling and validation
2013 (English)In: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214, Vol. 6, no 3, p. 403-416Article in journal (Refereed) Published
Abstract [en]

In this work constitutive models suitable for thermo-mechanical forming of the titanium alloy Ti-6Al-4V are evaluated. A tool concept for thermo-mechanical forming of a double-curved sheet metal component in Ti-6Al-4V is proposed. The virtual tool design is based on finite element (FE) analyses of thermo-mechanical sheet metal forming in which two different anisotropic yield criteria are evaluated and compared with an isotropic assumption to predict global forming force, draw-in, springback and strain localisation. The shape of the yield surface has been found important and the accuracy of the predicted shape deviation could be slightly improved by including the cooling procedure. The predicted responses show promising agreement with the corresponding experimental observations when the anisotropic properties of the material are considered

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-2804 (URN)10.1007/s12289-012-1094-7 (DOI)000323246800007 ()2-s2.0-84881612325 (Scopus ID)080f5d25-6705-4ea9-bfc9-3eb2e4d64aa6 (Local ID)080f5d25-6705-4ea9-bfc9-3eb2e4d64aa6 (Archive number)080f5d25-6705-4ea9-bfc9-3eb2e4d64aa6 (OAI)
Note
Validerad; 2013; 20120314 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Odenberger, E.-L., Oldenburg, M., Thilderkvist, P., Stoehr, T., Lechler, J. & Merklein, M. (2011). Tool development based on modelling and simulation of hot sheet metal forming of Ti-6Al-4 V titanium alloy (ed.). Paper presented at . Journal of Materials Processing Technology, 211(8), 1324-1335
Open this publication in new window or tab >>Tool development based on modelling and simulation of hot sheet metal forming of Ti-6Al-4 V titanium alloy
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2011 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 211, no 8, p. 1324-1335Article in journal (Refereed) Published
Abstract [en]

In the aero engine industry alternative manufacturing processes for load carrying aero engine structures imply fabrication. The concept of fabrication involves simple forgings, sheet metals and small ingots of e.g. titanium alloys which are welded together and heat treated. In the concept phase of the product development process, accurate evaluations of candidate manufacturing processes with short lead times are crucial. In the design of sheet metal forming processes, the manual die try out of deep drawing tools is traditionally a time consuming, expensive and inexact process. The present work investigates the possibility to design hot forming tools, with acceptable accuracy at short lead times and with minimal need for the costly die try out, using finite element (FE) analyses of hot sheet metal forming in the titanium alloy Ti-6Al-4 V. A rather straightforward and inexpensive approach of material modelling and methods for material characterisation are chosen, suitable for early evaluations in the concept phase. Numerical predictions of punch force, draw-in and shape deviation are compared with data from separate forming experiments performed at moderately elevated temperatures. The computed responses show promising agreement with experimental measurements and the predicted shape deviation is within the sheet thickness when applying an anisotropic yield criterion. Solutions for the hot forming tool concept regarding heating and regulation, insulation, blank holding and tool material selection are evaluated within the present work.

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-4590 (URN)10.1016/j.jmatprotec.2011.03.001 (DOI)000291172700002 ()2-s2.0-79955468380 (Scopus ID)28e14cd9-1267-4c0f-b16f-0847c6bc79ec (Local ID)28e14cd9-1267-4c0f-b16f-0847c6bc79ec (Archive number)28e14cd9-1267-4c0f-b16f-0847c6bc79ec (OAI)
Note
Validerad; 2011; 20110316 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Odenberger, E.-L. (2010). Direct hit development: Thermo mechanical sheet metal forming of components for load carrying aero engine structures (ed.). In: (Ed.), (Ed.), FLYGTEKNIK 2010, Flyg- och rymdindustri 2020–2040: . Paper presented at Flygteknik 2010 : 18/10/2010 - 19/10/2010.
Open this publication in new window or tab >>Direct hit development: Thermo mechanical sheet metal forming of components for load carrying aero engine structures
2010 (English)In: FLYGTEKNIK 2010, Flyg- och rymdindustri 2020–2040, 2010Conference paper, Meeting abstract (Refereed)
Abstract [en]

A successful development project in the modern industry can be characterised by “direct hit” development work, in which the accuracy is high and the lead time is short. The ability to realise successful projects with short lead times has become increasingly important to maintain competitiveness. To increase the competitiveness of the Swedish aerospace industry, alternative manufacturing processes for static load carrying aero engine structures are desired. Traditionally, the structures consist of large-scaled single castings delivered by only a few international suppliers. New manufacturing processes imply in this case fabricated components which mean that complete structures are built from simple forgings, sheet metals and small castings by welding and heat treatment. The concept of fabrication take advantage of the possibility to increase the own level of processing, reduce weight and thereby fuel consumption but also product cost. Concurrently new manufacturing methods for formed sheet metal parts and relations with new sub-suppliers need to be developed and introduced. One challenge in producing complete structures based on fabrication is related to the prediction ability for springback and shape deviation by simulation, in order to attain tolerances in an effective way. In the aerospace industry extremely high demands on safety and reliability exists which require good knowledge regarding the effects of the manufacturing process on the material and the influence on the resultant properties, through the whole manufacturing chain. The advanced Finite Element (FE) technology in combination with computer capacity makes precise analyses possible assuming that proper material descriptions are used. Analyses of sheet metal forming can provide information of formability, thinning, shape deviation, resultant mechanical properties and residual stress state which is important input to analyses of subsequent manufacturing processes such as welding and heat treatment. This presentation summarise results and work procedures obtained in research and development projects regarding short lead time design, compensation and manufacturing of deep drawing tools for titanium and nickel based alloys. The mechanical properties are studied by performing material tests and experimental data are used to calibrate mathematical material descriptions. Typical for titanium alloys used in aero engine applications is that the mechanical properties depend on the thermo-mechanical loading history of the blank, rolling direction, load direction in tension or compression, strain rate and temperature. The high strength properties in combination with low ductility at room temperature often imply that sheet metal forming has to be performed at elevated temperatures. Nickel based super alloys such as Inconel 718 has high room temperature ductility but due to the high strength properties, springback is often considerable in formed sheet metal parts. Responses such as punch force, draw-in, formability, thinning, strain distribution and springback are evaluated using FE-simulations of sheet metal forming in order to secure forming concepts and obtain virtual geometries within shape and thickness tolerances. Tool surfaces are compensated for springback, if necessary, using the *INTERFACE_COMPENSATED_NEW capability in LS-DYNA v971. The compensated FE-tool surfaces are used to generate high quality surfaces suitable for the milling process. Design and component solutions for hot forming tools such as heating and temperature regulation, insulation, lubricants and tool material selection are evaluated. Depending on the choice of material description, promising agreement between predicted and measured values has been obtained. Isotropic material descriptions are compared with models including anisotropy, where the latter was found important to obtain accurate predictions of strain localisation and shape deviation. The work substantiates the idea that it is possible to realise development projects for sheet metal applications in titanium Ti-6Al-4V and Inconel 718 accurately and with no further need for modifications of the tools, which is of outmost importance when developing tools at a short lead time.The need for sheet metal parts, simulation results and increased insight to the forming procedures from the Swedish aero engine industry is provided for in the projects. One main objective is to create possibilities for Swedish SMEs to develop into new sub-suppliers of sheet metal components for the aerospace industry. Collaborating companies and universities in the research and development projects are Volvo Aero Corporation, Industrial Development Centre (IUC) in Olofström AB, Luleå University of Technology and a few SMEs with practical experience in forming high performance materials. Engineering Research Nordic AB and LFT in Erlangen, Germany, are also involved in the projects. Future work is focused on studies of additional commercial geometries in which forming concepts, FE-models and material descriptions are further developed in order to obtain competitive cold and hot forming processes with minimal consumption of material. The aim considering hot forming of titanium is to fully take advantage of temperature and time dependent effects as important process parameters in the development process of new hot forming concepts. The objective is to produce components with high accuracy and low product cost.The research funding by VINNOVA - NFFP 4 and 5 for SME and Volvo Aero Corporation are gratefully acknowledged.

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-35520 (URN)a12ffc64-46a0-415e-a68f-7df2720ab616 (Local ID)a12ffc64-46a0-415e-a68f-7df2720ab616 (Archive number)a12ffc64-46a0-415e-a68f-7df2720ab616 (OAI)
Conference
Flygteknik 2010 : 18/10/2010 - 19/10/2010
Note
Godkänd; 2010; 20140114 (evawes)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Odenberger, E.-L. (2009). Concepts for hot sheet metal forming of titanium alloys (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Concepts for hot sheet metal forming of titanium alloys
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To increase the competitiveness of the Swedish aero engine industry alternative manufacturing methods for load carrying aero engine structures are desired, in order to reduce product cost and enable weight reduction and thereby fuel consumption. Traditionally, these structures mainly consist of large-scaled single castings of e.g. titanium- and nickel based super alloys. By fabrication, the structures are instead built from sheet metal parts, small ingots and simple forgings which are welded together and heat treated. The alternative approach implies the need for time and cost efficient evaluations of candidate manufacturing techniques, early in the product development process. One challenge in producing complete structures within shape tolerance lies in accurate predictions of springback and compensation for shape deviation which occurs in the different processes of the manufacturing chain. Finite Element (FE) simulations are used extensively in e.g. the sheet metal stamping industry where the technology has contributed to a better understanding of chosen forming processes and where the prediction capabilities has significantly reduced the time consuming, inexact and costly die tryouts. However, the reliability of the numerical simulations depends not only on the models and methods used but also on the accuracy and applicability of the input data. The material model and related property data must be consistent with the conditions of the material in the process of interest. In addition, creating as little deviance as possible between the FE model and the experimental setup is a prerequisite for the correlation between predicted and measured values. Naturally, difficulties regarding e.g. modelling and estimations of friction arise, among others.The objective of this thesis is to suggest possible hot and cold forming concepts based on FE analyses for the production of sheet metal prototype components in the titanium alloys Ti-6Al-4V and Ti-6242 together with the nickel based super alloy Inconel 718, respectively. The research activities are focused on material characterisation, evaluation of suitable constitutive models and its calibration, virtual tool design and manufacturing of sheet metal forming tools together with production of prototype components. The aim is to perform a direct-hit research and development work in which the lead time is short and the need for the manual die tryout can be kept at a minimum. The forming tests functions as validation tests in which predicted responses of global forming force, draw-in, temperature, strain localisation and shape deviation are correlated with predicted responses. Different yield criteria which include the anisotropy and strength differential (asymmetry in yielding between tension and compression) of the titanium alloy Ti-6Al-4V are compared with an isotropic assumption. Special emphasises are made to models and methods suitable for analyses in the medium temperature range, for evaluations early in the product development process.In paper A, compression tests on Ti-6Al-4V were performed at different temperatures in order to study the mechanical behaviour and create experimental reference data for identification of material model parameters of constitutive equations. Inverse modelling was used as a method for the parameter identification, in which three different equations were studied. At a temperature of 500°C, none of the studied constitutive equations were found able to satisfactory describe the flow behaviour. However, the method was found suitable for the purpose of identifying model parameters. Later on, the physically based constitutive equation developed by Nemat-Nasser et al. (2001) was found able to describe the flow behaviour of Ti-6242 [1]. In the work by Nemat-Nasser et al. the model has been shown to be able to describe the flow behaviour of Ti-6Al-4V at different temperatures and strain rates accurately. The equation was applied in FE analyses of a hot forming test, a U-bend test, of Ti-6242. The experimental study of Ti-6242, including U-bend tests, at different thermo-mechanical conditions performed in Paper B, revealed that the formability is increased and that the springback can be decreased with increasing temperature. However, it was also found that an increased temperature alone does not necessary imply a reduced shape deviation. In paper C, a short lead time methodology for the design, compensation and manufacturing of deep drawing tools in the nickel based alloy Inconel 718 is suggested. Rather than stating a new methodology, the work contributes to the idea that it is possible to perform a virtual direct-hit development work for the production of five different double-curved components within tolerance at an extremely short lead time. Compensation for the predicted shape deviation was performed in which the tool surfaces were over compensated by means of FE analyses. In paper D and F, the short lead time methodology was applied for the development of hot forming concepts to produce two different Ti-6Al-4V sheet metal components. The material characterisation, presented in paper E, provides with experimental reference data for calibration of three different yield criteria. Predicted responses such as punch force, draw-in and shape deviation show promising agreement with experimental observations when applying anisotropic yield formulations. The shape of the yield surface was found important for the prediction of shape deviation and the occurrence of strain localisation. Some issues of the FE-model suggest areas for further development. An interesting extension to the present work would be to include models for phase transformation and creep or stress relaxation and include the effect of strain rate for sheet metal forming in the higher temperature range. Further on, it is of interest to extent anisotropic yield criteria to function in coupled thermo-mechanical analyses and to include orthotropic elasticity. This, in order to increase the possibility to perform detailed studies of the temperature as an important process parameter for the prediction of shape deviation and studies of strain localisation limits.

Abstract [sv]

Koncept för varm plåtformning av titanlegeringarFör att Svensk flygmotorindustri ska öka sin konkurrenskraft söks alternativa tillverkningsmetoder för framtagning av lastbärande flygmotorkomponenter. Målsättningen är att uppnå en minskad produktkostnad samt möjliggöra viktminskning och därmed bränsleförbrukning. Traditionellt består dessa komponenter av stora enstycksgjutgods i titan och nickelbaserade legeringar. Genom fabrikation byggs istället strukturerna från plåtdetaljer, små gjutgods och smiden genom svetsning och efterföljande värmebehandling. Det alternativa tillvägagångssättet innebär behov av tids- och kostnadseffektiva metoder för utvärdering av möjliga tillverkningstekniker tidigt i produktutvecklingsprocessen. En av utmaningarna vid fabrikation av kompletta flygmotorstrukturer, inom tolerans, ligger i en noggrann prediktering av återfjädring och kompensering för de formförändringar som uppstår i de olika tillverkningsstegen. Simulering med Finita element (FE) metoden är ett väl använt verktyg t.ex. inom den plåtformande tillverkningsindustrin där metodiken har bidragit till en bättre förståelse för olika formningsprocesser. FE metodikens möjligheter har minskat den tidskrävande, oexakta och kostnadskrävande verktygsutprovningen betydligt. Tillförlitligheten hos numeriska simuleringar beror av tillämpade modeller och metoder men också av noggrannhet och tillämpbarheten hos experimentell indata. Materialmodell och relaterad data måste vara överrensstämmande med de förutsättningar som råder för den aktuella processen. Vidare är det en förutsättning att minimera avvikelser mellan FE modellen och den verkliga processen, för att kunna jämföra predikterade resultat med verkligt utfall. Naturligtvis uppstår svårigheter och problematik kring t.ex. modellering och identifiering av friktion, bland annat.Avhandlingens mål är att föreslå möjliga varma och kalla formningsmetoder baserat på FE analyser för formning av plåtkomponenter i titanlegeringarna Ti-6Al-4V och Ti-6242 tillsammans med den nickelbaserade legeringen Inconel 718. Forskningsaktiviteterna fokuseras kring materialkarakterisering, utvärdering av lämpliga konstitutiva modeller och metoder för parameteridentifiering, virtuellt datorbaserad verktygsutveckling samt tillverkning av formningsverktyg och pressning av prototypdetaljer. Målsättningen har varit att bedriva forskningsaktiviteter och utvecklingsarbete på ett träffsäkert sätt med korta ledtider och där behovet av den manuella inprovningen kan minimeras. Formningstesten fungerar som validerande provning där global formningskraft, plåtindrag, temperatur, töjningslokalisering och återfjädring (formavvikelse) jämförs med beräknade resultat. Olika flytvillkor som tar hänsyn till materialets anisotropa egenskaper och osymmetri vid drag- och tyckbelastning för Ti-6Al-4V jämförs med ett isotropt antagande. Tonvikten läggs vid modeller och metoder som lämpar sig väl för analyser med relativt lågt temperaturområde (upp till 560 °C) tidigt i produktutvecklingsprocessen. I artikel A, genomfördes kompressionsprover på cylindriska provstavar i Ti-6Al-4V vid olika temperaturer för att studera legeringens mekaniska egenskaper och skapa experimentell referensdata som använts vid parameteridentifiering av tre olika konstitutiva ekvationer genom inversmodellering. Vid en temperatur av 500 °C visade sig ingen av de studerade konstitutiva ekvationerna beskriva flytkurvan tillfredställande. Metodiken visade sig dock fungera väl i syftet att identifiera modellparametrar. Vid senare studier visade sig den konstitutiva ekvationen utvecklad av Nemat-Nasser et al. (2001) beskriva den sanna spännings - töjningskurvan för Ti-6242. Nemat-Nasser et al. (2001) visade att ekvationen noggrant beskriver hårdnandebeteendet hos Ti-6Al-4V vid olika temperaturer och töjningshastigheter. Modellen tillämpades i FE analyser av varmformning, ett U-bockstest, i Ti-6242 med tillräcklig noggrannhet.Den experimentella studien av plåtformning av Ti-6242 presenterad i artikel B, för U-bockstest vid olika termomekaniska förhållanden visade på en ökad formbarhet och minskad återfjädring med ökande temperatur. Det visade sig dock att enbart en ökad temperatur inte nödvändigtvis innebär en minskad återfjädring.I artikel C föreslås en metodik, ett arbetssätt, för att genomföra utveckling, kompensering och tillverkning av verktyg för plåtformning av den nickelbaserade legeringen Inconel 718. Hellre än att föreslå en ny metodik bidrar arbetet till idén att det är möjligt att bedriva en träffsäker virtuellt baserad utveckling för produktion av fem olika dubbelkrökta komponenter med en mycket kort ledtid. Genom FE analyser kompenserades verktygsgeometrier för återfjädring.I artiklarna D och F tillämpas metodiken som föreslogs i artikel C gällande framtagning av varmformningskoncept för tillverkning av två olika plåtkomponenter i Ti-6Al-4V. Materialkarakteriseringen som presenteras i artikel E bidrar med experimentell data för identifiering av modellparametrar för tre olika flytvillkor. Predikterade resultat såsom stämpelkraft, plåtindrag, och formavvikelse stämmer lovande överrens med experimentella mätvärden och observationer då anisotropa flytvillkor tillämpas. Flytytans form påverkar predikteringen av återfjädring och uppkomsten av töjningslokalisering. Vissa delar av FE modellen ger uppslag för vidare utveckling. Intressanta vidare studier innefattar inkludering av modeller för fasomvandling och kryp eller spänningsrelaxation samt att inkludera töjningshastigheten för analyser av formning vid högre temperaturer. Vidare är det av intresse att vidareutveckling befintliga anisotropa flytvillkor till att fungera i termo-mekaniskt kopplade FE analyser. Syftet är att öka möjligheten för att genomföra detaljerade studier av temperaturen som en viktig processparameter för prediktering av återfjädring och töjningslokalisering.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2009. p. 64
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Hot sheet metal forming, Titanium, FE simulation, Validation, Springback, HCP, Engineering mechanics - Solid mechanics, Varmforming, Titan, FE simulering, Validering, Återfjädring, HCP, Teknisk mekanik - Fastkroppsmekanik
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-25957 (URN)bded4fa0-cef1-11de-b769-000ea68e967b (Local ID)978-91-7439-046-9 (ISBN)bded4fa0-cef1-11de-b769-000ea68e967b (Archive number)bded4fa0-cef1-11de-b769-000ea68e967b (OAI)
Note
Godkänd; 2009; 20091111 (evawes); DISPUTATION Ämnesområde: Hållfasthetslära/Solid Mechanics Opponent: Professor Roger Reed, University of Birmingham, England Ordförande: Professor Mats Oldenburg, Luleå tekniska universitet Tid: Onsdag den 16 december 2009, kl 09.00 Plats: E 243, Luleå tekniska universitetAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-24Bibliographically approved
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