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The evolution of residual stresses in a stress relief heat treatment of test specimen of alloy 718
University West, Department of Engineering Science, Research Enviroment Production Technology West. GKN Aerospace Sweden.ORCID iD: 0000-0001-7169-7069
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. Vol. 11, 331-343 p.
Keyword [en]
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: urn:nbn:se:hv:diva-10808ISBN: 978-3-85125-490-7 (print)OAI: oai:DiVA.org:hv-10808DiVA: diva2:1081938
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
In thesis
1. Process chain simulation of forming, welding and heat treatment of Alloy 718
Open this publication in new window or tab >>Process chain simulation of forming, welding and heat treatment of Alloy 718
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
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:nbn:se:hv:diva-10917 (URN)978-91-87531-54-5 (ISBN)978-91-87531-53-8 (ISBN)
Supervisors
Available from: 2017-05-12 Created: 2017-04-24 Last updated: 2017-04-24

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