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Title: Inertia friction welding of high strength aerospace alloys
Author: Bennett, Christopher J.
ISNI:       0000 0004 2742 5519
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2007
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Inertia friction welding is an important industrial joining technique for the production of axisymmetric components. Two parts, one rotating and the other stationary, are brought together under axial load and rotational kinetic energy stored in a flywheel is transformed into thermal energy and plastic deformation through friction at the interface between the work pieces. The process is quick and repeatable and generates good quality welds with a small heat affected zone (HAZ) One of the main objectives of this research was to produce a modelling tool that can be used to represent the welding of high strength aerospace alloys with particular reference to shaft applications. The commercial software DEFORM-2D was used as it contains a 2.5D modelling capability suitable for this application and can be easily used by industry. The aim of the process modelling tool is to reduce development time and cost by the use of a process modelling tool which would mean fewer development welds are required for new material combinations and geometries. Initial models created were based on the nickel-based superalloy, Inconel 718 and the capability was then extended to the high strength steels, AerMet 100 and S/CMV, which are suitable for aero-engine shaft applications. Material data required to run weld models was defined and a test programme commissioned in order to obtain the properties for the high-strength steels. Microstructural investigations, including continuous cooling and isothermal tests were also carried to determine phase transformation information that was relevant to the welding process. This included the presence of the "bainite nose", and the volume change associated with the martensite transformation on cooling. The latter was shown to have a significant effect on the residual stresses developed in as-welded components. The volume changes are shown to act as a stress relief of up to 1000MPa in the HAZ of the weld. Experimental testing, which included thermal imaging and thermocouple measurements, was carried out in order to gain more insight into the inertia friction welding of the high strength steels. This testing also included some tests using novel welding techniques to attempt to reduce the post-weld cooling rate and the effects of these techniques on the cooling rate are presented. These tests also provided data for validation of the weld model. The research concludes that DEFORM-2D can be used to model the IFW process between high-strength aerospace materials for aero-engine shaft applications and typical results show an error of ±15% with respect to the final upset value.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available