Periodic Reporting for period 1 - MICROFORM (FORMING OF MICROPERFORATED OUTER SKIN OF HLFC WINGS ASSISTED BY FEM SIMULATON)
Período documentado: 2020-05-01 hasta 2021-10-31
Global aviation industry produces around 2% of all human-induced CO2 and is responsible for 12% of CO2 emissions from all transport sources. Reducing greenhouse gas emissions, fuel consumption and noise goes hand in hand with reducing operating costs and making future engines and aircraft more attractive both for the industry and society.
New generation of large Hybrid Laminar Flow Control (HLFC) structures aims to reduce complexity by using variable pitch microperforations along the outer skin in order to control suction without the need of internal chambering. Outer skins are made of Titanium alloys and variable microperforation entails a new challenge in terms of forming. This must be investigated before deciding on the most suitable skin forming technology and alloy for these new HLFC structures.
The main objective of MICROFORM is to develop a suitable forming process for the real-scale manufacturing of leading edge HLFC wing outer skins with constant and variable pitch microperforation patterns and supporting simulation tools to minimize their initial process development costs. Main research activities are focused on stretch and hot forming processes of Ti Gr.2 and Ti Gr.5 alloys.
MICROFORM will contribute to reduce global CO2 emissions in two ways:
• Emissions related to the manufacturing process: the optimisation applied to hot/stretch forming processes will allow to reduce lead time of components by 30%.
• Emissions related to the use of the aircraft: suitable forming processes will enable a reduction of 10% in fuel consumption in future LPA aircrafts. This implies the reduction by 10% CO2 footprint and air pollutant emissions of future aircrafts.
To achieve this main objective, the following technical/operative objectives have been defined:
• OB1: Make a reasoned selection of the most suitable forming technologies of HLFC wing skins.
• OB2: Demonstrate feasibility of hot forming microperforated Ti Gr 2 and Ti Gr 5 thin sheets with variable microperforation pattern.
• OB3: Demonstrate feasibility of stretch forming microperforated Ti Gr 2 thin sheets with variable microperforation pattern.
• OB4: Develop and adjust finite element models (FEM) to simulate stretch and hot forming process of these materials.
• OB5: Implement cost reduction strategies to reduce the cost of manufacturing large forming tools.
• OB6: Apply forming process developments and new simulation tools to the manufacturing of real small-scale and large-scale HLFC wing skin demonstrators.
• OB7: Characterize large-scale demonstrators to verify the compliance with requested quality and dimensional requirements.
• OB8: Define equipment and investments for an economically viable high-production rate of HLFC wings.
New generation of large Hybrid Laminar Flow Control (HLFC) structures aims to reduce complexity by using variable pitch microperforations along the outer skin in order to control suction without the need of internal chambering. Outer skins are made of Titanium alloys and variable microperforation entails a new challenge in terms of forming. This must be investigated before deciding on the most suitable skin forming technology and alloy for these new HLFC structures.
The main objective of MICROFORM is to develop a suitable forming process for the real-scale manufacturing of leading edge HLFC wing outer skins with constant and variable pitch microperforation patterns and supporting simulation tools to minimize their initial process development costs. Main research activities are focused on stretch and hot forming processes of Ti Gr.2 and Ti Gr.5 alloys.
MICROFORM will contribute to reduce global CO2 emissions in two ways:
• Emissions related to the manufacturing process: the optimisation applied to hot/stretch forming processes will allow to reduce lead time of components by 30%.
• Emissions related to the use of the aircraft: suitable forming processes will enable a reduction of 10% in fuel consumption in future LPA aircrafts. This implies the reduction by 10% CO2 footprint and air pollutant emissions of future aircrafts.
To achieve this main objective, the following technical/operative objectives have been defined:
• OB1: Make a reasoned selection of the most suitable forming technologies of HLFC wing skins.
• OB2: Demonstrate feasibility of hot forming microperforated Ti Gr 2 and Ti Gr 5 thin sheets with variable microperforation pattern.
• OB3: Demonstrate feasibility of stretch forming microperforated Ti Gr 2 thin sheets with variable microperforation pattern.
• OB4: Develop and adjust finite element models (FEM) to simulate stretch and hot forming process of these materials.
• OB5: Implement cost reduction strategies to reduce the cost of manufacturing large forming tools.
• OB6: Apply forming process developments and new simulation tools to the manufacturing of real small-scale and large-scale HLFC wing skin demonstrators.
• OB7: Characterize large-scale demonstrators to verify the compliance with requested quality and dimensional requirements.
• OB8: Define equipment and investments for an economically viable high-production rate of HLFC wings.
Until now the work performed includes:
-Benchmarking of forming technologies
-Experimental stretch forming and hot forming tests with small-scale samples
-Forming process specifications for the demonstrators
-Mechanical testing of microperforated materials
-Stretch forming and hot forming FEM simulation model development
-Manufacturing and characterisation of small-scale demonstrators by stretch and hot forming
-Design of tooling and stretch forming process simulation for final large-scale demonstrator
The main results achieved so far include:
- Microperforations significantly reduced the formability of Ti Gr 2. The forming limit at the plane strain condition was reduced from 32% for unperforated material to 10-13%.
- Microperforation did not almost affect anisotropic behaviour of Ti Gr 2 base material. Yield stress or ultimate stress were comparatively slightly higher, but elongation was considerably reduced.
- Critical process instabilities can be avoided during the forming of microperforated Ti samples by both stretch and hot forming with proper process parameters. Shapes with low curvature radius like those specified for HLFC wing edges can be obtained with both forming processes starting from flat blanks.
- For stretch forming, suitability of working with Ti Gr 2 welded blanks that are needed for the dimensions of the real scale WTT demonstrator has been proven. To avoid fracture through the welds and orange peel on the surface, maximum stretch load and strain rate have to be reduced.
- Despite stretch forming avoids critical instabilities during forming and gives rise to a manageable springback, hole size, shape and pitch are strongly modified. This must be investigated using FEM process simulation tools to meet technical specifications requested for HLFC aircraft structures.
- For hot forming, feasibility of shaping microperforated Ti Gr 2 and Gr 5 has been demonstrated. A minimum oxidation on the surfaces of the skin is generated but the influence on the mechanical properties is negligible for Gr 2 and acceptable for Gr 5. Minimum influence on hole size, shape and pitch was observed in selected geometry representative of leading edges of wings and VTP.
- Stretch and hot forming FEM process simulation tools under development will support the development of future HLFC structures with constant and variable microperforation patterns, since they will be able to capture the influence on the pitch modification in different regions of the surface of the blanks.
Additionally, management and dissemination activities have been carried out.
-Benchmarking of forming technologies
-Experimental stretch forming and hot forming tests with small-scale samples
-Forming process specifications for the demonstrators
-Mechanical testing of microperforated materials
-Stretch forming and hot forming FEM simulation model development
-Manufacturing and characterisation of small-scale demonstrators by stretch and hot forming
-Design of tooling and stretch forming process simulation for final large-scale demonstrator
The main results achieved so far include:
- Microperforations significantly reduced the formability of Ti Gr 2. The forming limit at the plane strain condition was reduced from 32% for unperforated material to 10-13%.
- Microperforation did not almost affect anisotropic behaviour of Ti Gr 2 base material. Yield stress or ultimate stress were comparatively slightly higher, but elongation was considerably reduced.
- Critical process instabilities can be avoided during the forming of microperforated Ti samples by both stretch and hot forming with proper process parameters. Shapes with low curvature radius like those specified for HLFC wing edges can be obtained with both forming processes starting from flat blanks.
- For stretch forming, suitability of working with Ti Gr 2 welded blanks that are needed for the dimensions of the real scale WTT demonstrator has been proven. To avoid fracture through the welds and orange peel on the surface, maximum stretch load and strain rate have to be reduced.
- Despite stretch forming avoids critical instabilities during forming and gives rise to a manageable springback, hole size, shape and pitch are strongly modified. This must be investigated using FEM process simulation tools to meet technical specifications requested for HLFC aircraft structures.
- For hot forming, feasibility of shaping microperforated Ti Gr 2 and Gr 5 has been demonstrated. A minimum oxidation on the surfaces of the skin is generated but the influence on the mechanical properties is negligible for Gr 2 and acceptable for Gr 5. Minimum influence on hole size, shape and pitch was observed in selected geometry representative of leading edges of wings and VTP.
- Stretch and hot forming FEM process simulation tools under development will support the development of future HLFC structures with constant and variable microperforation patterns, since they will be able to capture the influence on the pitch modification in different regions of the surface of the blanks.
Additionally, management and dissemination activities have been carried out.
MICROFORM focuses on introducing innovative solutions (FE simulation tools, process optimization based on DoE…) in state-of-the-art stretch and hot forming machines to solve the following challenges and demonstrate the feasibility of manufacturing real HLFC skins with variables microperforation patterns.
− Oxygen uptake and oxidation of surface and inside the holes
− Modification of hole size, shape and pitch after forming
− Buckling distortion due to residual stress accumulation and low sheet thickness
− Waviness or overfolds with heavy 3D contours
− Microcracks in hole walls
− Strain concentration in areas of high tensile stresses
− Poor dimensional tolerances due to springback effect
− Limitations on the size and capability of forming and microdrilling machines
The progress beyond the state of the art include:
-Until now only stretch forming of constant microperforation Ti Gr 2 has been proven, while current state of the art is the industrial hot forming of Ti Gr 5 under shielding conditions. MICROFORM will demonstrate suitability of forming Ti Gr 2 and Ti Gr 5 with different microperforation densities and variable patterns in small-scale demonstrators.
-There is commercial software to assist on the stretch forming process optimization but are black boxes. Performance of existing commercial software (FormCAM) and newly developed FEM models in MICROFORM (using vertical and more open FE packages) will be compared in small-scale demonstrator.
-Different strategies to reduce tooling manufacturing costs will be investigated
The main impact of the project is to contribute to reach the environmental objectives set up for aviation. MICROFORM will improve the wing efficiency to reduce fuel burn, CO2, NOx and noise. Thus, it will be ensured the development of cost-effective manufacturing processes for pre-serial production of HLFC wings. It is expected to reduce setup and forming process development costs of new parts by 30% and forming process development times by 30%. So, the project will also contribute to improve the European aeronautic industry competitiveness by pushing the EU to the forefront in the area of HLFC.
− Oxygen uptake and oxidation of surface and inside the holes
− Modification of hole size, shape and pitch after forming
− Buckling distortion due to residual stress accumulation and low sheet thickness
− Waviness or overfolds with heavy 3D contours
− Microcracks in hole walls
− Strain concentration in areas of high tensile stresses
− Poor dimensional tolerances due to springback effect
− Limitations on the size and capability of forming and microdrilling machines
The progress beyond the state of the art include:
-Until now only stretch forming of constant microperforation Ti Gr 2 has been proven, while current state of the art is the industrial hot forming of Ti Gr 5 under shielding conditions. MICROFORM will demonstrate suitability of forming Ti Gr 2 and Ti Gr 5 with different microperforation densities and variable patterns in small-scale demonstrators.
-There is commercial software to assist on the stretch forming process optimization but are black boxes. Performance of existing commercial software (FormCAM) and newly developed FEM models in MICROFORM (using vertical and more open FE packages) will be compared in small-scale demonstrator.
-Different strategies to reduce tooling manufacturing costs will be investigated
The main impact of the project is to contribute to reach the environmental objectives set up for aviation. MICROFORM will improve the wing efficiency to reduce fuel burn, CO2, NOx and noise. Thus, it will be ensured the development of cost-effective manufacturing processes for pre-serial production of HLFC wings. It is expected to reduce setup and forming process development costs of new parts by 30% and forming process development times by 30%. So, the project will also contribute to improve the European aeronautic industry competitiveness by pushing the EU to the forefront in the area of HLFC.