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Process chain simulation of forming, welding and heat treatment of Alloy 718
University West, Department of Engineering Science, Research Enviroment Production Technology West. (PTW)ORCID iD: 0000-0001-7169-7069
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Trollhättan: University West , 2017. , 44 p.
Series
Licentiate Thesis: University West, 17
Keyword [en]
Forming, Welding, Stress relieve annealing, Heat treatment, Finite Element Simulation, Manufacturing process chain, Alloy 718
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-10917ISBN: 978-91-87531-54-5 (print)ISBN: 978-91-87531-53-8 (electronic)OAI: oai:DiVA.org:hv-10917DiVA: diva2:1090449
Supervisors
Available from: 2017-05-12 Created: 2017-04-24 Last updated: 2017-04-24
List of papers
1. Simulation of the influence of forming on residual stresses and deformations after welding and heat treatment in Alloy 718
Open this publication in new window or tab >>Simulation of the influence of forming on residual stresses and deformations after welding and heat treatment in Alloy 718
2014 (English)In: / [ed] E. Oñate, J. Oliver and A. Huerta, 2014, 1657-1666 p.Conference paper, (Other academic)
Abstract [en]

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.

Keyword
Manufacturing process chain, Forming, Welding, Heat treatment, Residual stresses, Alloy 718
National Category
Materials Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7109 (URN)2-s2.0-84923973244 (Scopus ID)
Conference
11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI)
Available from: 2014-12-10 Created: 2014-12-10 Last updated: 2017-04-24Bibliographically approved
2. The evolution of residual stresses in a stress relief heat treatment of test specimen of alloy 718
Open this publication in new window or tab >>The evolution of residual stresses in a stress relief heat treatment of test specimen of alloy 718
2016 (English)In: Mathematical Modelling of Weld Phenomena 11 / [ed] S. Sommitsch, N. Enzinger, P. Mayr, Graz, 2016, Vol. 11, 331-343 p.Conference paper, (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
Graz: , 2016
Keyword
Residual stress, welding, chain of manufacturing
National Category
Applied Mechanics Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-10808 (URN)978-3-85125-490-7 (ISBN)
Conference
11th International Seminar Numerical Analysis of Weldability
Funder
Knowledge Foundation
Available from: 2017-03-15 Created: 2017-03-15 Last updated: 2017-04-24Bibliographically approved
3. Simulation and validation of forming, edge milling, welding and heat treatment of an alloy 718 component
Open this publication in new window or tab >>Simulation and validation of forming, edge milling, welding and heat treatment of an alloy 718 component
(English)Manuscript (preprint) (Other academic)
Abstract [en]

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.

Keyword
Forming, Welding, Heat treatment, Finite Element Simulation, Manufacturing chain, Alloy 718
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-10916 (URN)
Note

Ingår i lic

Available from: 2017-04-24 Created: 2017-04-24 Last updated: 2017-04-24Bibliographically approved

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