Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Modelling Aspects in Forming and Welding of Nickel-Base Superalloys
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials. RISE IVF AB.ORCID iD: 0000-0002-1432-444x
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The reduction of fuel consumption and carbon dioxide emissions are currently a key factor for the aviation industry because of major concerns about climate change and more restrictive environmental laws. One way to reduce both fuel consumption and CO2 emissions is by significantly decreasing the weight of vehicles while increasing the efficiency of the engine. To meet these requirements, the European aero-engine industry is continuously focusing on improved engine designs and alternative manufacturing methods for load-carrying structures in advanced materials, such as titanium and nickel-base superalloys. These new manufacturing methods involve sheet-metal parts, small castings, and forgings assembled using welding, enabling flexible designs where each part is made of the most suitable materials and states, with advantages such as reduced product cost, lower weight, and increased engine efficiency.

In this thesis, a manufacturing process chain including forming and welding in two nickel-base superalloys, alloy 718 and Haynes® 282®, is studied. The aim of this work is to determine which aspects within the material and process are the most relevant to accurately predict the amount of shape distortions that occur along the manufacturing chain. The effect of the forming temperature on the predicted springback is included. The results are compared with experimental cold and hot forming tests with a subsequent welding procedure. During forming of a double-curved component in alloy 718 at room temperature, open fractures are observed in the drawbead regions, which could not be predicted while evaluating the formability of the material based on Nakazima tests and forming limit curves (FLC). The generalised incremental stress-state dependent damage model (GISSMO) is calibrated and coupled with the anisotropic Barlat Yld2000-2D material model to accurately predict material failure during forming using LS-DYNA. The mechanical properties of alloy 718 are determined via uniaxial tensile, plane strain, shear, and biaxial tests at 20 °C. The deformations are continuously evaluated using the digital image correlation (DIC) system ARAMIS™. Numerical predictions are able to accurately predict failure on the same regions as observed during the experimental forming tests. Comparisons of the distribution of damage on one of the drawbeads, between simulations and damage measurements by acoustic emission, indicate that higher damage values correspond to bigger micro cracks. The history from the sheet-metal forming procedure, i.e. residual stresses, strains, element thickness, and geometry, is used as the input for the FE analysis of a subsequent welding procedure of a strip geometry in alloy 718 and Haynes® 282®. A comprehensive characterization of the elasto-plastic properties of both alloys between 20 and 1000 °C is included. Other temperature-dependent properties are extracted from JMatPro-v9 for the corresponding specific batches. The results from the simulations show that the welding procedure further increases the shape distortions over the part. Encouraging agreement was found between the model predictions and the results of forming and welding tests in alloy 718. The findings underscore the importance of including the material history and accurate process conditions along the manufacturing chain to both the prediction accuracy of accumulated shape distortions, and to the potential for the industry.

The work also comprises hot forming of the double-curved component in alloy 718 and Haynes® 282®. The presence and nature of serrations due to the dynamic strain aging (DSA) phenomenon between 300 and 800 °C is studied. Microstructural observations are consistent with the behaviour of the material at the different temperatures tested. The residual stresses obtained from the hot forming simulations are transformed based on the stress-relaxation tests performed at high temperatures ranging from 700 to 1000 °C. The results show the importance of using the novel modelling approach combining the anisotropic Barlat Yld2000-2D material model with the thermo-mechanical properties and stress-relaxation behaviour of the material to predict the final geometry of the component with high accuracy. A welding simulation of a bi-metallic strip geometry obtained from the hot formed double-curved component is performed numerically. The effect of the two superalloys on the shape distortions over the part is discussed.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords [en]
alloy 718, Haynes 282, cold forming, hot forming, material characterization, GISSMO, welding, heat treatment, manufacturing chain, springback, shape distortions, dynamic strain aging, DSA, microstructure
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Research subject
Solid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-76243ISBN: 978-91-7790-460-1 (print)ISBN: 978-91-7790-461-8 (electronic)OAI: oai:DiVA.org:ltu-76243DiVA, id: diva2:1357748
Public defence
2019-11-29, E231, Luleå, 09:00 (English)
Opponent
Supervisors
Projects
Virtual process chain for superalloy sheet metal aero engine structures - Validation and demonstrator (NFFP6)Validation of a fabrication procedure for bi-metallic aero engine components in superalloys (NFFP7)
Funder
Vinnova, 2013-01173 and 2017-04849Available from: 2019-10-04 Created: 2019-10-04 Last updated: 2019-11-14Bibliographically approved
List of papers
1. Calibration of a damage and fracture model for alloy 718
Open this publication in new window or tab >>Calibration of a damage and fracture model for alloy 718
Show others...
2016 (English)In: Advancements in Theoretical and Applied Plasticity: Proceedings of PLASTICITY ’16: The Twenty Second International Symposium on Plasticity and its Current Applications / [ed] Akhtar S. Khan, Fulton, Maryland 20759-0591, USA: NEAT PRESS , 2016, p. 223-225Conference paper, Published paper (Refereed)
Abstract [en]

Nickel-based superalloys are primarily used in the hot sections of aircraft engines because they can maintain their mechanical properties and chemical stabilities at high temperatures under severe corrosive environments i.e. for a long time. In order to simulate forming procedures in Alloy 718 sheets, the GISSMO damage and failure model is coupled with both isotropic von Mises and anisotropic Barlat YLD2000 material models in the finite element code LS-DYNA. In this study, the calibration of the GISSMO model for forming simulations at room temperature is discussed. The calibration requires failure strains for different stress states as a function of triaxiality, which are obtained by testing six different specimen geometries up to fracture. Numerical predictions will be compared with experimental observations from forming tests.

Place, publisher, year, edition, pages
Fulton, Maryland 20759-0591, USA: NEAT PRESS, 2016
Keywords
damage, fracture, nickel-based superalloys, Alloy 718, forming, GISSMO
National Category
Metallurgy and Metallic Materials Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62818 (URN)978-0-9911654-7-6 (ISBN)
Conference
22nd International Symposium on Plasticity and Its Current Applications, (Plasticity 2016), Kona, Hawaii, January 3-9, 2016
Projects
NFFP6 - Virtuell processkedja för plåtformade flygmotorstrukturer i superlegeringar – Validering och demonstrator
Funder
VINNOVA, 2013-01173
Available from: 2017-04-05 Created: 2017-04-05 Last updated: 2019-10-04Bibliographically approved
2. Damage and fracture during sheet-metal forming of alloy 718
Open this publication in new window or tab >>Damage and fracture during sheet-metal forming of alloy 718
Show others...
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
3. Comparison of forming, welding and heat treatment simulations in LS-DYNA and MSC Marc
Open this publication in new window or tab >>Comparison of forming, welding and heat treatment simulations in LS-DYNA and MSC Marc
2016 (English)In: 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) , 2016, p. 660-663Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
American Welding Society (AWS) & Japan Welding Society (JWS), 2016
Keywords
forming, welding, heat treatment, alloy 718, LS-DYNA, MSC Marc, creep
National Category
Metallurgy and Metallic Materials Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62835 (URN)
Conference
10th International Conference on Trend in Welding Research & 10th International Welding Symposium of Japan Welding Society (9WS), Tokyo, October 11-14, 2016
Projects
NFFP6 - Virtuell processkedja för plåtformade flygmotorstrukturer i superlegeringar – Validering och demonstrator
Funder
VINNOVA, 2013-01173
Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2019-10-04Bibliographically approved
4. Prediction of shape distortions during forming and welding in alloy 718
Open this publication in new window or tab >>Prediction of shape distortions during forming and welding in alloy 718
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The finite-element method (FEM) has considerably contributed to the development of more advanced manufacturing methods for metal structures. The prediction of the final shape of a component is of great interest to the manufacturing industry. In addition to its inherent difficulties, the presence of various types of processes in the manufacturing chain may dramatically increase the level of demand. Therefore, including all steps of the manufacturing process in the simulations is 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 modeled with simplifications, resulting in a reduced prediction accuracy. This hinders the compensation of accumulated shape distortions based on the simulation results. One such example is the fabrication of aero-engine structures, in which the history from the forming procedure has not been considered in subsequent welding and heat treatment analyses. In the present study, a double-shaped 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 the GISSMO damage 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.

Keywords
forming, welding, alloy 718, springback, nickel-base superalloys, superalloys, GISSMO, anisotropy
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-63348 (URN)
Projects
Virtual process chain for superalloy sheet metal aero engine structures - Validation and demonstrator (NFFP6)
Funder
Vinnova, 2013-01173
Available from: 2017-05-14 Created: 2017-05-14 Last updated: 2019-10-04
5. Cold and hot forming procedures for alloy 718
Open this publication in new window or tab >>Cold and hot forming procedures for alloy 718
2019 (English)In: Proceedings of the Processing and fabrication of advanced materials - XXVII, 2019, p. 118-124, article id Paper 14Conference paper, Published paper (Refereed)
Abstract [en]

Since the past few decades, superalloys have had an important role in the reduction of fuel consumption and carbon dioxide emissions for the transportation sector due to major concerns about climate change and more restrictive environmental laws. Advanced manufacturing methods in nickel-based superalloy aero-engine components allow lightweight designs with a reduced product cost and weight while increasing the efficiency of the engine. However, the prediction of the final geometry of a hot-formed part remains a challenge. In this work, a double-curved sheet-metal component in alloy 718 is studied. The material is characterized at 20°C and 900°C. The predicted shape deviation of the part when considering the anisotropic Barlat Yld2000-2D material model with data at both temperatures is discussed. The effect of including data from stress-relaxation tests at 900°C on the simulated springback is assessed. A hot-forming test is performed at around 900°C to validate the FE simulations regarding springback, strain levels, forming temperatures, and press forces. The results show the significance in considering the input data at high temperatures along with the stress-relaxation behaviour at different strain levels to accurately predict the final geometry of the component.

Keywords
alloy 718, hot forming, material characterization
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-76242 (URN)978-91-87289-44-6 (ISBN)
Conference
Processing and fabrication of advanced materials - XXVII (PFAMXXVII)
Projects
Virtual process chain for superalloy sheet metal aero engine structures - Validation and demonstrator (NFFP6)
Funder
Vinnova, 2013-01173
Available from: 2019-10-04 Created: 2019-10-04 Last updated: 2019-10-04
6. Validation of hot forming in alloy 718
Open this publication in new window or tab >>Validation of hot forming in alloy 718
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Demanding needs on the production of advanced parts made of nickel-base superalloys are continuously increasing to meet the requirements of current environmental laws. The use of lightweight components in load-carrying aero-engine structures have the potential to significantly reduce fuel consumption and greenhouse emissions to the atmosphere. Furthermore, the competitiveness of the aero-engine industry can benefit from reduced product costs and shorter development times while minimizing costly tryouts and increasing the efficiency of the engine. The manufacturing process of aero engine parts in superalloys at temperatures close to 950 °C produces lower stamping force, residual stresses, and shape distortions than traditional forming procedures at room temperature. In this work, a hot forming procedure of a double-curved component in alloy 718 is studied. The mechanical properties of the material are determined between 20 and 1000 °C. The presence and nature of serrations in the stress-strain curves is assessed. The novel version of the anisotropic Barlat Yld2000-2D material model, which allows the input of thermo-mechanical data, is used in LS-DYNA to model the behavior of the material at high temperatures. The effect of considering stress-relaxation data on the predicted shape distortions is evaluated. The results show the importance of considering the thermo-mechanical anisotropic properties and stress-relaxation behavior of the material to predict the final geometry of the component with high accuracy. The implementation of advanced material models in the finite element (FE) analyses, along with precise process conditions, is vital to produce lightweight components in advanced materials of interest to the aerospace industry.

Keywords
hot forming, alloy 718, superalloy, stress relaxation, anisotropy, high temperature
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-76204 (URN)
Projects
Virtual process chain for superalloy sheet metal aero engine structures - Validation and demonstrator (NFFP6)
Funder
Vinnova, 2013-01173
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-04
7. Shape prediction of a hot formed component in nickel-base superalloys
Open this publication in new window or tab >>Shape prediction of a hot formed component in nickel-base superalloys
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Current manufacturing processes of advanced aero engine components in nickel-base superalloys are performed at approximately 950 °C, with varying holding times, to reduce the amount of residual stresses, and thereby shape deviations, over the part. The aim of such procedures is to obtain the final geometry of the component within tolerance and avoid costly tryouts, which can be unfavorable to the competitiveness of the aerospace industry. In addition, a reduction in the forming temperature or holding time may significantly reduce the energy consumption and carbon dioxide (CO2) emissions while increasing the ecological sustainability of the process. In this work, the numerical study of a hot forming procedure of a double-curved component in Haynes® 282® is presented. The influence of the forming temperature and holding time on the predicted amount of springback at different stages of the hot forming procedure is assessed. The resulting shape distortions are compared with identical FE analyses in alloy 718 at 870 °C available in literature. The anisotropic properties of the material are determined at temperatures ranging from 20 to 1000 °C. A qualitative analysis of the different types of serrations present in the hardening curves between 300 and 900 °C is included in the study. Microstructural observations of selected specimens are correlated to the material-characterization tests. The thermo-mechanical data is used as input to the novel version of the Barlat Yld2000-2D material model in LS-DYNA. The results show that forming of Haynes® 282® at 870 °C produces high shape distortions over the part with values beyond the sheet thickness, in contrast to the response of alloy 718. A comparison of the stress-relaxation rate with available data in literature for alloy 718 at 870 °C reveals that Haynes® 282® relaxes about 50% slower than alloy 718, whereas reasonably analogous at 950 °C. An increase in the forming temperature to 950 °C significantly reduces the amount of springback. Therefore, it can be concluded that forming of Haynes® 282® requires a higher temperature than reported for alloy 718 to reach similar amount of springback. The presented studies indicate that the use of advanced anisotropic models together with the thermo-mechanical properties and stress-relaxation behavior of the material is of utmost importance to accurately predict the final geometry of lightweight components of interest to the aerospace industry.

Keywords
anisotropy, hot forming, alloy 718, Haynes 282, stress relaxation, superalloy
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-76239 (URN)
Projects
Validation of a fabrication procedure for bi-metallic aero engine components in superalloys (NFFP7)
Funder
Vinnova, 2017-04849
Available from: 2019-10-04 Created: 2019-10-04 Last updated: 2019-10-04

Open Access in DiVA

fulltext(59323 kB)60 downloads
File information
File name FULLTEXT01.pdfFile size 59323 kBChecksum SHA-512
43f7af2be6b6231ca7c4d7bf7f5c765482eefb80ade7855487e162285306c07e86a1df6b5b645388cb31c766476c9fafa887b24c8f83df13e59713474c3efda0
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Pérez Caro, Lluís
By organisation
Mechanics of Solid Materials
Metallurgy and Metallic MaterialsManufacturing, Surface and Joining Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 60 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 704 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf