Overview
Structural testing of major aircraft components is a very expensive and time-consuming process that significantly adds to the overall cost of designing and certifying a new aircraft product. If testing can be reduced, based on validated and safe numerical analysis methods, this will provide the European aircraft industry with a significant business and technological advantage.
Structural certification, based on a virtual testing process, appears a promising way to achieve the following global objectives in a medium term of five to seven years.
The main innovation in the MUSCA was to address built-up structures with a high degree of complexity where the modelling is fine enough to capture local effects or non-linear behaviour that are necessary to predict both failure initiation and collapse. The scientific tools to reach these objectives require novel advances in computational mechanics and statistics that are addressed in MUSCA in parallel with large scale computing.
Based on the state of the art, the consortium identified three key research areas to address:
- Techniques for large scale Non Linear analysis: domain decomposition techniques coupled with advanced parallel processing Non Linear solvers, error estimator for quality assessment
- Multi-criteria failure analysis: critical review, selection and validation of the most efficient engineering procedures for multi-mode failure analysis of structural details
- Sensitivity and reliability techniques: assessment of input uncertainties (material properties, geometry and load scattering) on the structural performance using stochastic simulations, sensitivity surface response methods.
The project was structured into the following work packages (WP):
WP1 - analysis of structural certification of large components
Four large component structural tests were identified and documented by the industrial partners, with a special focus on the following items:
- description of the role of the test with regards to the overall process;
- description of the main analysis difficulties;
- process analysis, with a recommended way towards a more 'simulation assisted' process;
- delivery of CAD, FEM to the partners.
WP2 - Large modelling capabilities
The main objective of WP2 was to develop methods and computational schemes of such effectiveness that displacements, stresses and the maximum load carrying capacity of structural components of a size up to large aircraft sections can be accurately analysed with control of the error in the numerical solutions.
WP3 - Smart multi-criteria failure analysis
Within WP3 the multi-mode failure behaviour of large structures were identified and structural details were designed for each generic analysis difficulty of existent test data. Existing failure criteria were reviewed or further developed and validated using the defined structural details to provide an integrated multi-criteria failure analysis that could be accepted by airworthiness authorities.
WP4 - Reliability & sensitivity methods
The objective of WP4 was to deliver numerical tools that would be able to predict the effect of uncertainties on component performance and validate the integration of various types of data necessary to generate an understanding of a given component's characteristics including the uncertainties in materials, loading in a probabilistic sense.
Funding
Results
The three major research topics identified above will constitute the core R&D activity of MUSCA, but special attention was paid to focus partnership activities on actual analysis needs. The MUSCA consortium has therefore adopted the following work strategy:
a) WP1 analysed the certification process for some representative large aircraft components. These have been provided by industrial partners in order to demonstrate how testing and analysis are currently used to provide structural certification. Main analysis difficulties have been identified and classified for those MUSCA industrial large component benchmarks (WP1). Costs and duration have been evaluated to establish a baseline for future gains.
b) Numerical benchmark cases with associated existing structural tests were then identified representing main analysis problems derived from large-scale industrial benchmarks (WP2.0, WP3.0 and WP4.0). The partnership activities have been exclusively focused on these numerical test cases for evaluation and development of methodologies in each of the three key research areas previously defined.
c) Based on the most promising methodologies available, the actual validation of the overall multi-scale analysis process were made on three selected industrial benchmarks (WP5), with an original collaborative work organisation between partners. The validation of MUSCA developments were planned to be made using existing experimental test data provided by industrial partners for large-scale benchmark tests.
d) Potential cost savings and cycle reduction were planned to be assessed compared to base line established in WP1. Finally, with the experience gained in WP5, recommendations would be provided for an evolution of the structure justification process (WP6) that integrates the methodologies developed in MUSCA. To reach this goal, a senior expert in airworthiness requirements was associated with MUSCA in WP1 and WP6, in order to obtain information and advice on issues like analysis methods, processes, quality control and associated responsibilities.