GeoVar: Non-rigid geometry variation for fabricated aero engine structure

Research Project, 2014 – 2016

Concept and objectives
Green and sustainable aero engines require weight reduction. For the open rotor technology, with rotating Ni-based superalloy components this is enabled by fabrication (welding) methods where a number of small parts, often in different materials, are welded together.

In this type of fabricated structures, variation from manufacturing of the individual parts, from the fixturing and assembly process and from the welding process itself accumulates and propagates through the structure and creates geometrical variation in the final subsystem. This in turn has an influence on the ability to meet requirements on aerodynamics and life. It is therefore extremely important to have a reliable process to control how variation affects the final welded geometries. Therefore, the proposed project combines state of the art variation simulation with welding metallurgy, welding simulation and fixture design JTI-CS-2013-02-SAGE-02-035.

In traditional 3D variation simulation (stack-up’s) it is common to consider that the parts are rigid. Often in production, forces are applied manually or by different fixturing solutions to assure that requirements on offset are fulfilled before welding parts together in an assembly. Depending on assembly sequences and geometry variation of incoming material, different fixturing forces need to be applied from component to component to assure the right fit in the seam before welding. It may even be necessary to use active fixturing where the forces are varying during the welding process.

There are 3D variation simulation software capabilities today that consider non-rigid parts but they focus on sheet metal parts. In this project the main issue is to developed knowledge about castings and forgings together with sheet metal parts to define tolerances on ingoing parts and calculate forces needed in fixturing to assure final product requirements. A virtual and a physical demonstration of a weld assembly of a complex geometry component consisting of several rigid and flexible sub parts shall be performed.

The demonstration must comprise a fixture solution that can vary the fixturing/clamping force. The geometry assurance research will be complemented by weld distortion simulations. Computational Welding Mechanics simulations of a limited numbers of geometric variations will provide the fundamental understanding as well as give quantitative prescriptions of required fixturing forces. The main deliverable in the GeoVar project is a 3D variation simulation methodology solving the stated problem above, verified to TRL 6 by a virtual and physical demonstration of capability. The main benefit for the company is that the possibility to set the right tolerances and fixturing solutions increases in early phases in product development.

Contributions

• This project proposes a novel way to combine variation and welding simulation to support the design of future welding fixtures for aircraft engine components.
• Non-rigid Geometrical Variation Simulation will be further developed to optimize locator and support positions in order to minimize geometrical variation in the weld gap and also take fixturing forces into consideration.
• Computational Welding Mechanics simulations with integrated control functions will be further developed to prescribe fixturing forces for maintaining specific tolerances ahead of the weld for a stable weld process.
• The simulation areas will be combined and integrated to support the design of a physical welding fixture suitable for fabrication of aircraft engine components. The results will be demonstrated virtually and physically.

Project Coordinator: Rikard Söderberg, Chalmers