Guy Ferraris

A criterion for mode shape tracking: application to Campbell diagrams

The correlation criterion proposed in this article and called nc2o (normalized cross complex orthogonality) is based on the bi-orthogonality properties between rotor mode shapes calculated at different speeds of rotation. This criterion is proved using an industrial laminated rotor composed of disks and two fluid film bearings, whose characteristics depend on the speed of rotation. The industrial finite element model shows that the nc2o criterion provides a more efficient mode pairing of rotor shapes than those obtained by using classical correlation criteria. Moreover this criterion makes it easier to plot Campbell diagrams for strongly speed-of-rotation-dependent structures.

The problem of complex shape tracking in a Campbell Diagram or how to overcome crossing/veering phenomena

The correlation criterion proposed in this article and called NC 2 O (Normalized Cross Complex Orthogonality) ensures bi-orthogonality properties between rotor mode shapes calculated at dif-ferent speeds of rotation. This criterion is proofed on an industrial laminated rotor composed of disks and two fluid film bearings, whose stiffness and damping characteristics depend on the speed of rotation. The industrial finite element model shows that the NC 2 O criterion provides a more efficient mode pairing of rotor shapes than those obtained by using the classical cor-relation criteria. Moreover this criterion maker easier the Campbell diagram plotting of strongly ϕ ˙ -dependent structures.

A Highly Accurate Beam Finite Element for Curved and Twisted Helicopter Blades

Blade optimization is more than ever a crucial activity for helicopter manufacturers, always looking for performance improvements, noise reduction and vibratory comfort increase. Latest studies have led to design new blade concepts including a double swept plan shape, an evolutionary and increased twist angle at the tip and a new layout for internal components like roving spars. Such blades exhibit a highly coupled behavior between torsion, longitudinal and bending motions that should be accurately modeled for predictive numerical tools. In this research a highly accurate beam finite element is formulated in the rotating frame to improve the static deformation calculation under aerodynamic and centrifugal loads and thus enhance dynamic and stability analysis usually performed for a helicopter development. Numerical and experimental investigations are performed to demonstrate the model reliability both for academic beams with extreme shape and for actual blade design.Copyright