Safe Simulation for Extreme Requirements

Eurocopter Group, formed in 1992 with three locations in Germany, is one of the leading European aerospace companies today. Numerous technological innovations enable the 100% EADS subsidiary to assume the role of a pioneer in aviation. Helicopters like the NH-90 or Tiger are among the best on the market. In particular, the sometimes extreme operating conditions of the military product line and the use of new materials as well as innovative technologies, require expensive simulations and analyses on a continuous basis in the course of development time frames of several years.

The objective is fast development processes with high product quality. The requirement for the simulation experts of the Airframe and Equipment Stress Department is a powerful Finite Element Analysis (FEA) solution. Its professional application reduces the number of cost-intensive prototypes as well as physical tests. At the same time the software supports the administration of comprehensive analysis results as well as the expensive documentation obligations to the various testing institutions in the aerospace and defense industry.

Extreme Requirements

The scenario is well-known from many TV documentaries and film productions: Task force members are flown into dangerous conflict situations under the most difficult weather conditions and dropped off. The transport helicopters on the movie or television screen brave these conditions and are usually back in the air after only a few seconds. Perhaps the NH-90 will be seen in the near future in corresponding productions as one of the most modern helicopters of this class. The experts of the Airframe and Equipment Stress Department at Eurocopter in Ottobrunn are certain it will master such scenarios.

Eurocopter Group, formed in 1992 with three locations in Germany, is one of the leading European aerospace companies today.

The experienced engineers have promoted and secured the development of the helicopter over several years through dynamic simulations and analyses. Landing and crash speeds at 6mps to 10mps were simulated and analyzed on the department computers. The landing gear and fuselage of the 9-ton NH-90 must be able to endure these "landing shocks" in extreme situations to guarantee safe delivery of the passengers.

Due to the use of innovative material components, for example, with the first aircraft cell produced completely out of carbon fiber, the employees cannot always fall back on experience. Instead they are dependent on a professional software solution for FEA with powerful pre-processing and post-processing as well as solvers. For years now, Eurocopter has been putting their money on Femap from Siemens PLM Software, part of Siemens Industry Division, and now has seven network licenses as well as one NX Nastran license in service. "Femap imports Catia 3D CAD data, which is important for us, as well as laminate layup data from Catia Fibre Sim with very little effort," explains Jyrki Majamaeki, Femap user at Eurocopter. "With clean 3D geometry the very good meshing functions enable us to continue working directly on models, which saves us a tremendous amount of time."

Simulation Instead

Static and dynamic simulations of flight/landing maneuvers make up 70% of the analyses. In the case of the former, random flight maneuvers are frozen in as time steps in order to simulate and analyze stresses on different components. Dynamic analyses include landing maneuvers as well as evaluations of crashes with speeds up to 10mps. In these scenarios possible vibrations induced by a shock are also tested.

Static and dynamic simulations of flight/landing maneuvers make up 70% of the analyses.

With Femap, all acting load conditions can be created and applied in the preprocessing stage. These conditions are clearly and traceably visualized on the model during post-processing of the calculation results. The software environment makes precise contact calculations possible between two or more components, regardless of whether these are screwed, welded or riveted. Femap visualizes the different loads and clarifies the critical areas of extreme applied forces. Even wrinkling analysis of a sandwich panel, using an industry standard method implemented into the Femap interface by means of Femap's Application Programming Interface (API) is possible. Additional data conversion and the launching of an additional application can be spared and the engineer can concentrate on working on one interface.

Complex calculations, as they are the order of the day at Eurocopter, run via the Nastran Solver on the servers, simpler and smaller calculations can be carried out via the powerful NX Nastran Solver of Femap directly at the workstations (again sparing yet another working step). The good model management and documentation of the FEA solution has two advantages for the staff members: first the human oriented functionality means a considerable savings in work hours in the long development cycles, and secondly, they meet the expensive and comprehensive documentation requirements of the various qualification and verification instances of the aviation authorities and customers.

"By using Femap we can check the progressing engineering results in the development process more quickly and often make suggestions for improvement that save time and money," Majamaeki says. "Additional advantages lie in the reduction in the number of cost-intensive prototypes as well as in the very good documentation functionality in the familiar Windows environment." The staff are very close to a standard documentation form and uniform standard evaluations. This improves communication, minimizing the need for explanation, and facilitates delivery of work.

The department staff members are very satisfied with the Support from the Smart Engineering service providers. Smart Engineering provides rapid assistance with problems and has an open ear for Eurocopter's development proposals.

Friendliness, Automation Advantages

Femap is developed in a native Windows environment and offers a high user-friendliness on the basis of the familiar Windows user interface. Another important advantage of Siemens PLM Software for simulation professionals like Majamaeki is being able to write their own Visual Basic applications using Femap's API. Using the API in Femap users can visualize all kinds of different load cases quickly and easily and further process them, accelerating the postprocessing tremendously. "Individual load results can be easily taken from the model and migrated to Microsoft Excel with the click of a mouse for specific evaluations," Majamaeki says. "The ability to create a multitude of load types using the API facilitates recurring analysis tasks and saves a huge amount of time." In addition custom programs for different evaluations and the required furnishing of evidence can be directly integrated in Femap, thus eliminating diverse work steps. The automation minimizes error sources since a conversion or manual reproduction of the results in other tools is not necessary.

Using Femap from Siemens PLM Software, Eurocopter achieves an early evaluation of engineering processes with high product quality.

Using Femap from Siemens PLM Software Eurocopter achieves an early evaluation of engineering processes with high product quality. The powerful FEA solution reduces the number of cost-intensive prototypes and physical tests through its branch-oriented depth of functionality. Particularly in the course of development processes of several years in the aviation industry, where new materials and innovative technologies must be taken into consideration; time and time again the engineers are dependent on a tool that reliably supports ongoing simulations and analyses.

"A renewed calculation and reuse of existing models must be guaranteed in spite of shorter and shorter release cycles of new software versions," Majamaeki emphasizes. "The downward compatibility of Femap has absolutely convinced us here these last few years that the software can handle our requirements."

The determined calculation results supply the foundation for the fact that the helicopters withstand the extreme loads over their long years of use and the analysis history can always be retraced. New load cases can be quickly and easily compared with old ones. The staff members can then draw rapid conclusions about the extent to which the new load types are covered by old analyses or whether further, more precise analyses are required.

Femap and its powerful Application Programming Interface for automation of recurring analysis tasks shorten the time at Eurocopter to commercial viability, prevent construction errors, and improve the entire innovation process.