| 1. |
- Pérez Caro, Lluís, 1985-, et al.
(författare)
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Prediction of shape distortions during forming and welding of a double-curved strip geometry in alloy 718
- 2020
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer. - 0268-3768 .- 1433-3015. ; 107:7-8, s. 2967-2981
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Tidskriftsartikel (refereegranskat)abstract
- The finite element method (FEM) has considerably contributed to the development of advanced manufacturing methods for metal structures. The prediction of the final shape of a component is of great interest to the manufacturing industry. The level of demand may increase due to multistage processes. Therefore, including all steps of the manufacturing chain in the simulations is a key to being successful. This has been done for a long time in the stamping industry, which involves sequences of forming, trimming, and springback. However, more complex manufacturing procedures that include assembling of formed parts with forgings and castings via welding have been modelled with simplifications, resulting in a reduced prediction accuracy. In the present study, a double-curved part manufactured from alloy 718 is formed at 20 °C and laser-welded using the bead-on-plate procedure. The coupling of different manufacturing analyses, including cold forming, trimming, result mapping, welding, cooling, and springback, is achieved using LS-DYNA. Additionally, the effect of adding a damage and failure model in the forming simulation is studied. The results of the forming analysis are used as inputs for the material model *MAT_CWM in the welding simulation. The anisotropic thermomechanical properties of alloy 718 are determined at temperatures up to 1000 °C. Encouraging agreement is found between the model predictions and the results of forming and welding tests. The findings underscore the importance of including the material history and accurate process conditions along the manufacturing chain to both the prediction accuracy of shape distortions, and to the potential of the industry.
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| 2. |
- Steffenburg-Nordenström, Joachim, 1962-, et al.
(författare)
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Comparison of forming, welding and heat treatment simulations in LS-DYNA and MSC Marc
- 2016
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Ingår i: Proceedings of 10th International Conference on Trends in Welding Research & 9th International Welding Symposium of Japan Welding, American Welding Society (AWS) & Japan Welding Society (JWS). - : American Welding Society (AWS) & Japan Welding Society (JWS). - 9781510844032 ; , s. 660-663, s. 660-663
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Konferensbidrag (refereegranskat)abstract
- The manufacturing of components for aero engine structures from a flat sheet to the final shape usually requires several steps that may introduce residual stresses and shape distortions in the part. Depending on the magnitude, sign and distribution with respect to the stresses induced by the service load, the remaining stresses may affect the service life of a component, especially when submitted to cyclic loading. Nowadays, several types of software that have the ability to predict the residual stresses and the final shape of a component subjected to various process steps are available. However, literature shows a lack of comparison studies among different software tools for multi-step simulations of a manufacturing process. In this study, the manufacturing process chain of an aerospace component including forming, welding and heat treatment in the nickel-based superalloy 718 is modelled and simulated using the two finite element software codes LS-DYNA and MSC.Marc. The results from the displacement of the blank in the punch stroke direction, the equivalent plastic strain and the von Mises stress are compared between both FE codes. The displacement of the blank after forming is slightly higher in LS-DYNA compared to MSC.Marc, as well as the equivalent plastic strain and the von Mises stress values. This tendency is also observed after trimming and welding. It can also be noted that the distribution of both strains and stresses on the trimmed and welded parts varies between the two compared codes, presumably due to the choice of different solver options, explicit and implicit.
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| 3. |
- Steffenburg-Nordenström, Joachim, 1962-
(författare)
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Process chain simulation of forming, welding and heat treatment of Alloy 718
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Manufacturing of aero engine components requires attention to residual stress and final shape of the product in order to meet high quality product standards.This sets very high demands on involved manufacturing steps to meet design requirements. Simulation of manufacturing processes can therefore be animportant tool to contribute to quality assurance.The focus in this work is on simulation of a manufacturing process chain comprising of sheet metal forming, welding and a stress relief heat treatment.Simulation of sheet metal forming can be used to design a forming tool design that accounts for the material behaviour, e.g. spring back, and avoid problems such as wrinkling, thinning and cracking. Moreover, the simulation can also show how the material is stretched and work hardened. The residual stresses after forming may be of local character or global depending on the shape that is formed. However, the heat affected zone due to welding is located near the weld.The weld also causes large residual stresses with the major component along the weld. It is found that the magnitude of the residual stresses after welding is affected by remaining stresses from the previous sheet metal forming. The final stress relieve treatment will relax these residual stresses caused by e.g. forming and welding. However, this causes additional deformations.The main focus of this study is on how a manufacturing process step affects the subsequent step when manufacturing a component of the nickel-based super alloy 718. The chosen route and geometry is a simplified leading edge of an exhaust case guide vane. The simulations were validated versus experiments. The computed deformations were compared with measurements after each manufacturing step. The overall agreement between experiments and measurement was good. However, not sufficiently accurate considering the required tolerance of the component. It was found from simulations that the residual stresses after each process affects the subsequent step. After a complete manufacturing process chain which ends with a stress relief heat treatment the residual stresses were not negligible. VIII Special experiments were performed for studying the stress relief in order to understand how the stresses evolve through the heat treatment cycle during relaxation. It was found that the stresses were reduced already during the beginning of the heating up sequence due to decreasing Young´s modulus and yield stress with increasing temperature. Relaxation due to creep starts when a certain temperature was reached which gave a permanent stress relief.
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| 4. |
- Steffenburg-Nordenström, Joachim, 1962-, et al.
(författare)
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Simulation and validation of forming, edge milling, welding and heat treatment of an alloy 718 component
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes finite element simulations of a manufacturing process chain consisting of forming, weld preparation by milling, laser welding and stress relief heat treatment of an alloy718 aero-engine part. The work also includes experimental validation with optical measurements of the part after each process step. Approximation and discretization errors were avoided by keeping the same mesh and constitutive model. The results show that the remaining stresses affect the subsequent manufacturing process step and therefore, simulation of the process chain is essential. The accuracy with respect to the geometry showed relatively good agreement between measurement and simulation.
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| 5. |
- Steffenburg-Nordenström, Joachim, 1962-, et al.
(författare)
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Simulation and Validation of Forming, Milling, Welding and Heat Treatmentof an Alloy 718 Component
- 2017
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Ingår i: International Journal of Materials Forming and Machining Processes IJMFMP). - Aveiro : IGI Global. - 2334-4563 .- 2334-4571. ; 4:2, s. 15-28
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes finite element simulations of a manufacturing process chain consisting offorming, weld preparation by milling, laser welding and stress relief heat treatment of an alloy 718aero-engine part. The work also includes experimental validation with optical measurements of thepart after each process step. Approximation and discretization errors were avoided by keeping thesame mesh and constitutive model. The results show that the remaining stresses affect the subsequentmanufacturing process step and therefore, simulation of the process chain is essential. The accuracywith respect to the geometry showed relatively good agreement between measurement and simulation.
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| 6. |
- Steffenburg-Nordenström, Joachim, 1962-, et al.
(författare)
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Simulation of the influence of forming on residual stresses and deformations after welding and heat treatment in Alloy 718
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Manufacturing of components in aero engines requires attention to residual stress and final shape of the product in order to meet high quality product standards. This sets very high demands on involved manufacturing steps. The manufacturing of a V-shaped leading edge of a vane is simulated. It is made of Alloy718, which is a nickel based heat resistant material commonly used in aerospace components. The manufacturing process chain consists of forming, welding and heat treatment. The results show that the remaining residual stresses after a manufacturing process chain are affected when the residual history from the formingprocess is considered. The residual stress decrease after heat treatment is about 55-65%. Moreover, the von Mises stress profile through thickness at the centre of the radius at the weld joint is about 25% higher when full forming history is considered.
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| 7. |
- Steffenburg-Nordenström, Joachim, 1962-
(författare)
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The evolution of residual stresses in a stress relief heat treatment of test specimen of alloy 718
- 2016
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Ingår i: Mathematical Modelling of Weld Phenomena 11. - Graz. - 9783851254907 ; , s. 331-343
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Konferensbidrag (refereegranskat)abstract
- Manufacturing of aero engine components requires attention to residual stress and final shape of the product in order to meet high quality product standards. This sets very high demands on involved manufacturing steps to meet design requirements. Simulations are used to assure the latter. This requires an appropriate model to account for stress relaxation. The study is part of a project where the aim is to simulate a chain of manufacturing steps e.g. forming, welding and heat treatment. The focus in this paper is on the stress relaxation during the heat treatment step. It is imperative to have relevant data for calibrating this part of a constitutive model. A test procedure resembling the real conditions in the manufacturing chain is proposed. Tests were carried out on test specimens made of Alloy718 and used to calibrate a constitutive model. Comparisons between experimental and simulated results showed very good agreement.
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