| 1. |
- Barlo, A, et al.
(author)
-
Proposal of a New Tool for Pre-Straining Operations of Sheet Metals and an Initial Investigation of CR4 Mild Steel Formability
- 2023
-
In: IOP Conference Series: Materials Science and Engineering. - 1757-899X. ; 1284
-
Journal article (peer-reviewed)abstract
- With the increased focus on reducing carbon emissions in the automotive industry, more advanced materials are introduced to reduce the vehicle weight, and more complex component geometries are designed to both satisfy customer demands and to optimize the vehicle aerodynamically. With the increase in component complexity, the strain paths produced during the forming operation of car body components often display a highly non-linear behavior which makes the task of failure prediction during the manufacturing feasibility studies more difficult. Therefore, CAE engineers need better capabilities to predict failure induced by strain path nonlinearity. This study proposes a new tool designed for creating bi-linear strain paths, by performing a pre-strain of a sheet large enough to cut out Nakajima specimens to perform the post-straining in any direction. From five pre-straining tests the tool present a stable pre-straining operation with a uniform strain field in a radius of 100 [mm] from the centre, corresponding to the region of interest of a Nakajima specimen. From the five pre-strained samples, different Nakajima specimens are cut transverse and longitudinal to the rolling direction and a failure prediction approach in an alternative, path independent evaluation space was used to predict the onset of necking with promising results.
|
|
| 2. |
- Odenberger, Eva-Lis, et al.
(author)
-
A short lead time methodology for design, compensation and manufacturing of deep drawing tools for Inconel 718
- 2008
-
In: Conference Best in Class Stamping, June 16 - 18, 2008, Olofström, Sweden. - Olofström : Industriellt utvecklingscentrum i Olofström AB. - 9789163329487
-
Conference paper (peer-reviewed)abstract
- This paper presents a systematic methodology for the design and manufacturing of deep drawing tools generating high quality components at an extremely short lead time. Prototype tools for five different super alloy Inconel 718 sheet metal components were designed, manufactured and tested in 15 weeks. Two of these prototype tools (A, B) are the topics of this paper. The methodology is based on virtual tool design in which the tool concepts are secured and optimized with respect to sheet metal formability and shape deviation using FE-analyses. Tool surfaces are compensated for springback, if necessary, using the *INTERFACE_COMPENSATED_NEW capability in LS-DYNA v971 (B).The compensated FE tool surfaces are used as reference to generate high quality surfaces suitable for the milling process. Laser scanning was used to determine shape deviation. The CAD-evaluation revealed a minor shape deviation within tolerance of component (A) and a small over-compensation of the final geometry of component (B). The maximum shape deviation was however in the order of the sheet thickness. The work presented in this paper substantiate the idea that it is possible to realize development projects for new applications in Inconel 718 accurately, which is of outmost importance when developing tools at a short lead time. The key is consistent studies according to the systematic methodology in which FEanalyses were used for the virtual tool design and compensation.
|
|
| 3. |
- Odenberger, Eva-Lis
(author)
-
Concepts for hot sheet metal forming of titanium alloys
- 2009
-
Doctoral thesis (other academic/artistic)abstract
- 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.
|
|
| 4. |
- Odenberger, Eva-Lis
(author)
-
Direct hit development : Thermo mechanical sheet metal forming of components for load carrying aero engine structures
- 2010
-
In: FLYGTEKNIK 2010, Flyg- och rymdindustri 2020–2040.
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
| 5. |
- Odenberger, Eva-Lis, et al.
(author)
-
Direct-hit development of manufacturing processes: Thermo-mechanical forming of Titanium aero engine structures
- 2013
-
In: Book of Abstracts for the 4:th CEAS Conference, 2013. - Linköping : Linkoping University Electronic Press. - 9789175195209 ; , s. 175-
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
| 6. |
- Odenberger, Eva-Lis, et al.
(author)
-
Finite element modeling and validation of springback and stress relaxation in the thermo-mechanical forming of thin Ti-6Al-4V sheets
- 2019
-
In: The International Journal of Advanced Manufacturing Technology. - : Springer London. - 0268-3768 .- 1433-3015. ; 104:9-12, s. 3439-3455
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 7. |
- Odenberger, Eva-Lis
(author)
-
Material characterisation for analyses of titanium sheet metal forming
- 2005
-
Licentiate thesis (other academic/artistic)abstract
- New demands and opportunities for simulation driven product development, that today's finite element (FE) technology allow for, exists in modern industry. Full applicability, in which decisions based on numerical evaluations and predictions, require accurate material parameters and of course accurate modelling of remaining features. To describe the deformation of a certain material a variety of material models are available (e.g. constitutive equations, models for anisotropy, creep, phase transformation and microstructure evolution) which all contain model parameters that have to be determined. Often, different material models require specific types of experimental methods to determine its material model parameters. For example, the parameters in a constitutive equation may require a different type of experiment e.g. compression tests at certain strain rates compared to a creep model which may require another type of test method under strain rates valid for creep. The objective of this thesis is first to establish an experimental foundation and comprehension on the thermo-mechanical behaviour of the titanium alloys Ti-6Al-4V but foremost Ti-6242, and to procure a good understanding of the possibilities and difficulties of used testing methods. Furthermore, experimental data are used both to obtain constitutive material model parameters trough force and displacement from elevated temperature compression tests by use of inverse modelling, and in finite element analyses for validation and prediction by analyses of sheet metal forming. Elevated temperature compression tests on cylindrical specimens are used for both Ti-6Al-4V and Ti-6242, revealing many interesting characteristics of these alloys. The experimental data are then used to estimate material parameters of different constitutive equations and used in initial predictions of sheet metal forming of Ti-6242. Cold and hot sheet metal forming tests of Ti-6242 is performed in order to evaluate suitable sheet metal forming processes for the alloy. Process parameters are studied and the tests functions as validation tests for the correlation of numerical models.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Odenberger, Eva-Lis, et al.
(author)
-
Thermo-mechanical Material Characterization and Stretch-bend Forming of AA6016
- 2018
-
In: IOP Conference Series. - : Institute of Physics (IOP). - 1757-8981 .- 1757-899X. ; 418
-
Journal article (peer-reviewed)abstract
- 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.
|
|
