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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - AMOS (Additive Manufacturing Optimization and Simulation Platform for repairing and re-manufacturing of aerospace components)

Teaser

Summary

An aircraft\'s wings, engines and fuselage are susceptible to damage both on ground (by service and maintenance equipment and fixtures) and in the air (by foreign objects, lightning strikes etc). Although scheduled maintenance checks are performed throughout the life of an aircraft, defects can occur at any time and affect performance. Consequently, unscheduled maintenance is often needed to replace defective components and ensure safety, reliability and airworthiness. As each defect is different, unique solutions are required for each.
Because engine suppliers are taking maintenance in-house and offering \'power by the hour\', they are paid only for the time that their parts are in service. Repairs need to be carried out within the limited timeframe agreed between aircraft providers and airlines. Components have to be assessed (cleaned, tested, inspected), repaired if necessary, then tested again and replaced within this window or there would be major disruptions to operators and significant financial consequences for suppliers. Extended repair times are therefore very expensive for engine manufacturers and it may be more cost-effective for them to replace parts early rather than repair them.
Direct energy deposition (DED) systems are very flexible and show great potential for the cost-effective and efficient repair or re-manufacture of aerospace components such as turbine blades and landing gears. Their use will allow damaged components to be repaired on demand, and material lost in service to be re-deposited to restore the component to its original shape. This will reduce repair lead times, costs and material waste, and extend the service life of damaged or worn components which can be repaired rather than scrapped.
The Additive Manufacturing Optimisation and Simulation (AMOS) project is working with a number of different AM processes and material to assess their use for repair. The objectives of the project are to:
1. Study the process accuracy, repeatability, limitations and material integrity of a number of different DED systems using a number of materials.
2. Develop an effective system to generate the repair geometry.
3. Develop accurate models to simulate the different deposition processes.
4. Develop a repair process planning module.
5. Develop a method to optimise component design for additive repair.
6. Determine the data necessary for qualification of DED technologies for repair and remanufacture.
Within AMOS, the partners are carrying out fundamental research to understand the resultant material properties of a number of different DED processes for three different materials, and investigating the accuracy and limitations of these. Common additive processes typically use either a numerical (CNC) or robotic controller, so to ensure broad applicability, both types of system will be studied. Repairs made using three aerospace alloys (Ti-6Al-4V, Inconel 718, and AerMet100) in both powder and wire form are being investigated. Depositions will use either laser or tungsten welding.
Partners are developing methods of effectively generating computer models of each unique defect which can be sent to the additive controller. In conjunction with new sensors (developed by the Canadian partners) and models of the processes, this will allow the repair trajectories and parameters to be generated for each repair, given the material and machine.
At the same time, partners will look at the overall component design process and optimise commonly damaged parts so that they are suitable for repair using DED processes.

Work performed

During the first eighteen months, the partners defined the tests to be carried out during AMOS. A test schedule was created including a list of materials to be used, the test-piece geometry, the number of samples, the standards to be used and the pre- and post-processing requirements. Partners deposited samples and began work on a comprehensive test program.
The outline of the automatic repair geometry generation and process planning systems were defined and information provided regarding the deposition machines and materials to allow modelling activities to take place.
An aerospace component was selected for optimisation. Models of the manufacturing process, typical component failures and the component lifecycle were integrated and imported to a newly developed design platform. Software to analyse the component residual stress and deformation were integrated with this system. The data required for building a business case for DED repair and for qualification was identified.
Testing continued during the second period while the other objectives were also brought to maturity. During this period, the process accuracy of the different AM systems was assessed. It was shown that for a given set of parameters, the systems used were capable of sustaining stable depositions.
McGill University developed an AMOS benchmark test for scanning equipment along with a software module for carrying out topological analysis and reconstruction of component damage.Work in the next period will concentrate on testing the software at partner facilities to assess its modularity.
The University of Ottowa are developing a new sapphire sensor to measure the temperature of the AM system during deposition, as the centre temperature of the melt-pool is crucial for accurate modelling. This will provide accurate information on the thermal gradient models and allow process models to be validated.
A process planning and simulation module was developed, which will allow repair toolpaths to be generated automatically. A low-level planner translates scan data into a format which can be recognised by the DED system, whilst a high-level module includes adaptive volume slicing and toolpath generation methods. A generic solution for the repair of aerospace components has also been developed.
A multidisciplinary design framework is being developed to integrate DED manufacturing and repair simulation with life-cycle and mechanics failure models. This will enable resilient life-cycle solutions to be developed by accounting for manufacturing and repair strategies in the design phase. Pilot case studies have been identified and scanned and the repair geometry has been generated. A thermo-mechanical model has been applied to obtain the expected thermal distortion during use. Design constraints include cost and safety. Work on different ways of optimising multiple objectives and the associated computer time is underway.
Preliminary work on the route to qualification is also underway, focussing on connecting the data produced to date in the rest of the project.

Final results

DED processes need to be qualified for aerospace repair. This requires stringent testing of new materials and processes to ensure they are safe. The data necessary for qualification will be determined in AMOS, and the DED processes will be assessed to see whether they meet early qualification criteria. The data collected will be extremely valuable for the large companies who are partners in this project (GKN, PWC, and HDI), allowing them to understand the pros and cons of these systems and helping them to select suitable repair and re-manufacturing additive technologies. The tests conducted in this research are also extremely beneficial for the SMEs in this project (Liburdi and DPS) to validate and improve their existing repair systems and techniques.