Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - DELASTI (DEvelopment of advanced LASer based technologies for the manufacturing of TItanium HLFC structures)

Teaser

World air traffic volume is expected to grow per two in the next 15 years and that is the reason why reduction of air transport contribution to climate change is nowadays one of the most challenging objectives for aircraft manufacturers. Hybrid Laminar Flow Control (HLFC) on...

Summary

World air traffic volume is expected to grow per two in the next 15 years and that is the reason why reduction of air transport contribution to climate change is nowadays one of the most challenging objectives for aircraft manufacturers. Hybrid Laminar Flow Control (HLFC) on wing and fin is key to enhance the efficiency of the aircraft and to achieve up to 10% of fuel saving in commercial passenger aircrafts.
DELASTI project aims at developing manufacturing processes and system technology for reproducible laser beam welding (LBW) and laser straightening (LS) of titanium structures for HLFC Technology.
It must be noted that targeted HLFC structures are long (up to 4.5 m) and thin (0.8 mm thickness) components which are based on T-joints between microperforated Ti Gr.2 skin and Ti Gr.5 stringers. LBW will lead to distortions and the so-called “Zepelling effect”. The goal is to reverse and remove these distortions by applying subsequent LS process on the reverse of the samples.
Main technology challenges for the present project imply the integrated fabrication on a single assembly system of large welded panels with stringent dimensional tolerances, and full process supervision, relying on vey local heating techniques involving last generation laser sources (fibre or disc laser). Additionally, a revolutionary approach is sought which implies the use of this single laser source as the only production means, in order to get the whole welding and straightening process in a single production stage. Not only, this will imply a new concept of sheet fabrication but also enable the nowadays challenging fabrication of large welded skin-stringer thin (0.8 mm) structures in which the buckling effects have proven to be of special significance.
DELASTI project pursuits the following specific objectives:
O1. Development of LBW and LS processes to obtain structures with high quality joints and aerodynamic flatness, in buckling prone large-scale thin structures.
O2. Attain the desired quality and reproducibility of Ti LBW joints, by the integration of seam tracking and development of on line process surveillance system including seam penetration control and temperature measurement.
O3. Accurate and fast prediction of distortion and residual stress by means of FE based numerical models for the whole process chain involving the welding and straightening processes.
O4. Optimize and find useful parametric distortion related correlations for LBW and LS process parameters, based on experimental and validated FE numerical models (which use of efficient local and global modelling techniques).
O5. Development of a new closed loop LS concept based on the physical model equations, and the online feedback from the measured real time angular distortion.
O6. To mature and demonstrate the fabrication of lightweight promising flow control technologies in a fully integrated large scale demonstrator up to TRL 6.

Work performed

In terms of technical progress, the following main achievements must be highlighted:
• System technology design (laser source, laser welding head, robot, seam tracking, welding monitoring system, tooling, clamping and shielding system) for LBW and LS of demo parts and final demonstrator has been identified and components have been assembled together. Two welding facilities have been prepared for LBW and LS process development and large scale demo activities at HZG and LORTEK. Related to WP2.
• LBW and LS process development has been completed (process window and shielding conditions) by HZG and the transference to LORTEK’s setup has been performed. Related to WP3.
• Metallographic and mechanical characterisation of base materials and welded samples has been performed by HZG. Related to WP3.
• LBW monitoring and seam tracking system has been developed by LORTEK. Related to WP2.
• FEM based distortion prediction activities have been accomplished by LORTEK for both LBW and LS leading to a considerable qualitative and quantitative matching between modelling predictions and experimental data. At local level, detailed transient thermo-mechanical FE models have been developed, whereas at global level simplified methods based on inherent strain (also called Eigenstrain) have been defined. Related to WP4.
• Tooling and clamping system for final demonstrator (side panel) have been designed and manufactured by LORTEK. Related to WP5.
• Several project dissemination activities have been already done by HZG and LORTEK and a complete plan has been agreed between partners for the second project reporting period. Intellectual property rights (IPR) issues are currently being discussed. Related to WP6.

Final results

Scope of DELASTI represents somehow a new flanged approach. The progress beyond the state of the art and singularities are resumed herein.
• FEM distortion prediction: a FEM modelling framework is established integrating LBW and LS simulation based on a local (detailed FEM modelling ) global (inherent deformation based) integrated approach so that the distortion can be predicted and assessed in a rapid way (minutes).
• Joint quality control: The robustness and quality of thin sheet single sided fillet T-joint is assured by a validated seam penetration system based on a vision system which analyses root geometry
• LS of titanium: process development is carried out and relevant process parameters are linked to induced straightened angles. Analysis of relevant parameters is done through a combination of experimental and FEM modelling.
• Mechanical performance: static and fatigue strength is assessed and linked to weld quality and the resulting residual stresses.
• Fully integrated manufacturing system: Full integration is demonstrated for the whole production chain, relying on the use of a single laser source (disk laser). LBW and LS of a real size demonstrator (4.5 m long) is completed.
DELASTI project aims at validating a new enabling manufacturing route for large scale perforated thin sheet structures, while achieving the required in service performance and aerodynamic flatness through combined laser welding and straightening. The final aim in the roadmap is to produce innovative wing and tail HLFC structures with reduced aerodynamic drag.
Concerning expected impact, DELASTI focuses on large scale demonstration of technologies integrated at aircraft level in Large Passenger Aircraft (LPA) IADP. Within this Demonstration Platform, DELASTI is linked to WP 1.4, focused on the application of Hybrid Laminar Flow Technology (HLFC) for drag reduction on commercial transport aircraft. HLFC area in particular expects to reach the development and manufacturing of an improved HLFC demonstrator for long-term in-service operational use. In parallel to that, the definition of rules and processes required for certification for in-service long term demonstration and deployment of the HLFC technology at major components of the airframe will be launched.
This project is based on the specific issue of the manufacturing of leading edge segments with micro perforated outer skins out of titanium, to solve the challenge of reproducibility and consistency of laser-welding process with stringent surface quality requirements.
DELASTI project entails industrial, financial, technical and environmental impacts. Main short-term beneficiaries of these impacts will be European aeronautical industry, laser market, TM, partners (HZG and LORTEK) and the global society.

Website & more info

More info: http://www.lortek.es.