| 1. |
- Agelet de Saracibar, Carlos, et al.
(författare)
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Shaped Metal Deposition Processes
- 2014
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Ingår i: Encyclopedia of Thermal Stresses. - Dordrecht : Encyclopedia of Global Archaeology/Springer Verlag. - 9789400727380 ; , s. 4347-4355
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Bokkapitel (refereegranskat)abstract
- The shaped metal deposition (SMD) process is a novel manufacturing technology which is similar to the multi-pass welding used for building features such as lugs and flanges on components [1–7]. This innovative technique is of great interest due to the possibility of employing standard welding equipment without the need for extensive new investment [8, 9]. The numerical simulation of SMD processes has been one of the research topics of great interest over the last years and requires a fully coupled thermo-mechanical formulation, including phase-change phenomena defined in terms of both latent heat release and shrinkage effects [1–6]. It is shown how computational welding mechanics models can be used to model SMD for prediction of temperature evolution, transient, as well as residual stresses and distortions due to the successive welding layers deposited. Material behavior is characterized by a thermo-elasto-viscoplastic constitutive model coupled with a metallurgical model [6]. Two different materials, nickel superalloy 718 [6] and titanium Ti-6Al-4 V [7], are considered in this work. Both heat convection and heat radiation models are introduced to dissipate heat through the boundaries of the component. The in-house-developed coupled thermo-mechanical finite element (FE) software COMET [10] is used to deal with the numerical simulation, and an ad hoc activation methodology is formulated to simulate the deposition of the different layers of filler material.
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| 2. |
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| 3. |
- Fisk, Martin, et al.
(författare)
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Simulation and validation of repair welding and heat treatment of an alloy 718 plate
- 2012
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Ingår i: Finite elements in analysis and design (Print). - : Elsevier BV. - 0168-874X .- 1872-6925. ; 58, s. 66-73
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes simulation of repair welding and heat treatment together with measurements for validation. The possibility to replace global heat treatment with local using induction heating is evaluated with respect to obtained residual stresses. A physically based material model is used in the analyses. The result from the residual stress measurement shows that there are no significant differences between local heat treatment and global heat treatment.
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| 4. |
- Gad, Helge, et al.
(författare)
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MTH1 inhibition eradicates cancer by preventing sanitation of the dNTP pool
- 2014
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 508:7495, s. 215-221
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Tidskriftsartikel (refereegranskat)abstract
- Cancers have dysfunctional redox regulation resulting in reactive oxygen species production, damaging both DNA and free dNTPs. The MTH1 protein sanitizes oxidized dNTP pools to prevent incorporation of damaged bases during DNA replication. Although MTH1 is non-essential in normal cells, we show that cancer cells require MTH1 activity to avoid incorporation of oxidized dNTPs, resulting in DNA damage and cell death. We validate MTH1 as an anticancer target in vivo and describe small molecules TH287 and TH588 as first-in-class nudix hydrolase family inhibitors that potently and selectively engage and inhibit the MTH1 protein in cells. Protein co-crystal structures demonstrate that the inhibitors bindin the active site of MTH1. The inhibitors cause incorporation of oxidized dNTPs in cancer cells, leading to DNA damage, cytotoxicity and therapeutic responses in patient-derived mouse xenografts. This study exemplifies the non-oncogene addiction concept for anticancer treatment and validates MTH1 as being cancer phenotypic lethal.
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| 5. |
- Lindgren, Lars-Erik, et al.
(författare)
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Challenges in finite element simulations of chain of manufacturing processes
- 2013
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Ingår i: Physical and numerical simulation of materials processing VII. - Durnten-Zurich : Trans Tech Publications Inc.. - 9783037857281 ; , s. 349-353
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Konferensbidrag (refereegranskat)abstract
- Simulation of some, or all, steps in a manufacturing chain may be important for certain applications in order to determine the final achieved properties of the component. The paper discusses the additional challenges in this context
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| 6. |
- Lindgren, Lars-Erik, et al.
(författare)
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Thermo-Mechanics and Microstructure Evolution in Manufacturing Simulations
- 2013
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Ingår i: Journal of thermal stresses. - : Taylor & Francis. - 0149-5739 .- 1521-074X. ; 36:6, s. 564-588
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Tidskriftsartikel (refereegranskat)abstract
- Thermal stresses and deformations are present and important for many manufacturing processes. Their effect depends strongly on the material behavior. The finite element method has been applied successfully for manufacturing simulations. There are numerical challenges in some cases due to large deformations, strong non-linearities etc. However, the most challenging aspect is the modeling of the material behavior. This requires in many cases coupled constitutive and microstructure models.
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| 7. |
- Lundbäck, Andreas
(författare)
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Modelling and simulation of welding and metal deposition
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fusion welding is one of the most used methods for joining metals. This method has largely been developed by experiments, i.e. trial and error. The problem of distortion and residual stresses of a structure due to welding is important to control. This is especially important in the aerospace industry where the components are expensive and safety and quality are very important issues. The safety requirements and the high costs of performing experiments to find different manufacturing routes is the motivation to increase the use of simulations in design of components as well as its manufacturing. Thus, in the case of welding, one can evaluate the effect of different fixtures, welding parameters etc on the deformation of the component. The effects of previous processes are also important to consider, as well as it is important to bring forward the current state to subsequent processes.When creating a numerical model, the aim is to implement the physical behaviour of the process into the model. However, it may be necessary to compromise between accuracy of the model and the required computational time. The aim of the work presented in this thesis was to develop a method and model for simulation of welding and metal deposition of large and complex components using the finite element method. The model must be reliable and efficient to be usable in the designing and planning of the manufacturing of the component. In this thesis, the meaning of efficiency of a model is wider than just the computational efficiency. The time for creation and definition of the model should also be included. The developed methods enable the user to create a model for welding or metal deposition with a minimum of manual work. The method for defining weld paths and heat input together with activation of elements is now implemented in the commercial finite element software MSC.Marc. The implementation is based on the experience in this work and communication with the author. The approach has been validated against test cases. Naturally, this validation is dependent on sufficient accuracy of the heat input model and material model that are used. It is the first time a dislocation density model has been used to describe the flow stress in a welding simulation. The work has also demonstrated the possibility to calibrate heat input models with a physical based heat input model, thus relieving the need to calibrate the heat source versus measurements.Efficiency in terms of computing time has also been investigated in the course of this work. Three different methods has been explored and used, adaptive meshing, substructuring and parallel computation. The method that is found to be the most versatile and reduce the overall simulation time the most is parallel computation. It is straightforward for the user to employ and it introduces no reduction in the accuracy.
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| 8. |
- Lundbäck, Andreas, et al.
(författare)
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Modelling of metal deposition
- 2011
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Ingår i: Finite elements in analysis and design (Print). - : Elsevier BV. - 0168-874X .- 1872-6925. ; 47:10, s. 1169-1177
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Tidskriftsartikel (refereegranskat)abstract
- Modelling and simulation of metal deposition (MD) poses several challenges to the modeller in addition to the usual challenges in modelling of welding. The aim of the work presented in this paper is to enable simulation of metal deposition for large three-dimensional components. Weld paths that are created in an off-line programming system (OLP) can be used directly to prescribe the movement of the heat source in the model. The addition of filler material is done by activation of elements. Special care must be taken to the positioning of the elements, due to large deformations. Nodes are moved to ensure that the added material has correct volume and shape. A physically based material model is also implemented. This material model is able to describe the material behaviour over a large strain, strain rate and temperature range. Temperature measurements and deformation measurements are done in order to validate the model. The computed thermal history is in very good agreement with measurements. The computed and measured deformations also show quite good agreement. It has been shown that the approach yields correct results, providing that flow stress and heat input models are calibrated with sufficient accuracy. The method reduces the modelling work considerably for metal deposition and multipass welding. It can be used for detailed models but also lumping of welds is possible and often necessary for industrial applications.
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| 9. |
- Lundbäck, Andreas, et al.
(författare)
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Repair welding and local heat treatment
- 2014
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Ingår i: Encyclopedia of Thermal Stresses. - Dordrecht : Encyclopedia of Global Archaeology/Springer Verlag. - 9789400727380 ; , s. 4186-4194
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Bokkapitel (refereegranskat)
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| 10. |
- Lundbäck, Andreas, et al.
(författare)
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Simulating a chain of manufacturing processes for prediction of component properties
- 2011
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Ingår i: XXth International Symposium on Air Breathing Engines 2011. - Red Hook, NY : Curran Associates, Inc.. - 9781618391803
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Konferensbidrag (refereegranskat)abstract
- An integrated design of material and process is necessary when designing a component where the effect of the manufacturing route on its performance must be accounted for. This is particularly the case for welded components even when post weld heat treatment is performed. The paper describes developments done at Luleå University of Technology in cooperation with Volvo Aero in the Swedish National Programme for Aeronautical Research (NFFP) and in different European projects. The paper focuses on two particular issues of importance. The first is of more administrative character, the transfer of data between different finite element models used in each of the manufacturing steps. The other aspect is the extremely important issue of material modeling.Material models for simulation of a chain of manufacturing processes include additional complications besides large variations in strain rates and temperatures. These complications are caused by the changing microstructure that may occur. The authors expect that physically based models can have a larger range of applicability than engineering type of models. Physical based models are formulated by considering the underlying physics of the deformation whereas engineering type of models are more of a curve-fitting nature. The physical based models may also have a natural coupling to models of the microstructure evolution. However, the models must still be tractable for large-scale computations. Thus, they should be of the internal state variable type with relatively few additional parameters and equations to solve at the integration point level of finite elements. The paper describes a basic dislocation density model used in modelling different manufacturing processes and how it can be coupled to microstructure models. It is based on dislocation glide as the dominating mechanism for the plastic deformation. This may be models for phase changes, like in Ti6-4, or precipitate growth/dissolution as in Alloy 718. The coupled models will not only make it possible to describe the material behavior more correct over the process cycles but also predict the obtained microstructure. It is expected that future research may couple this information with defect predictions in order to contribute to life assessment. The paper includes some example of manufacturing simulations and also an example of simulation of a chain of manufacturing processes.
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