Buckling load analysis methods for rotor blade design

Project Information

Grant agreement ID: JOR3950043

Project closed

Start date 1 January 1996

End date 31 December 1997

Funded under

• Specific programme for research and technological development, including demonstration in the field of non-nuclear energy, 1994-1998

Total cost

No data

EU contribution

No data

Coordinated by

ENERGY RESEARCH CENTRE OF THE NETHERLANDS
Netherlands

CORDIS provides links to public deliverables and publications of HORIZON projects.

Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .

Deliverables

Buckling load prediction programmes for curved orthotropic panels

For the buckling load prediction of rotor blades some computer programmes are developed that are used and validated within the BUCKBLADE project. These programmes all describe the buckling of long anisotropic panels and consider either simply-supported or clamped edge constraints. As such the programmes can be applied to the general problem of buckling of double curved orthotropic (sandwich-) panels of any quasi-prismatic structure. The most useful programmes are documented for use on a PC by third parties. These programmes include: -STABLAD: Stability analysis Tool for Anisotropic rotor BLADe panels. With this tool the bifurcation load can be calculated of double-curved and twisted anisotropic panels under combined loading. -IMPANAL: Imperfect Panel ANALysis. With this program the maximum load can be calculated of imperfect panels. This programme does not include anisotropy, geometric twist, shear loading and sandwich panels. -CLAMPED: A programme with which the bifurcation load can be calculated of long orthotropic panels with clamped edge constraints. A set of computer programmes have been developed for the buckling load prediction of long double-curved and twisted layered anisotropic panels under various loading. Thanks to the modular structure, all programmes share the same routines for reading input and for the general program flow. This ensures that all these programmes have input files with the same format and that –for the same input-the stiffness and geometrical properties are identical. The most versatile programmes subjected to the validation within the BUCKBLADE project are prepared and documented for use in a DOS environment (under Windows they run as Console Application). State Of The Art Of Buckling Of Orthotropic Structures: The buckling load prediction tools that were available before starting the BUCKBLADE project describe in general buckling of rectangular orthotropic panels without pre-buckling deformation, see e.g. the report of the European GARTEUR research project, the method of C.W. Bert and the method of R.C. Tennyson. For the buckling of shells in revolution in general, the programme PANDA-2 by Bushnell is available. PANDA-2 includes effects of edge constraints and of stiffeners. For the influence of geometric imperfections several tools are developed that describe buckling of imperfect cylindrical shells such as used for launch rockets. The problem of buckling of rotor blade panels has the characteristic aspect that it is (quasi-)prismatic in longitudinal direction while it has the detailed variations of geometry, loading and edge constraints in transverse direction. For this reason programmes that assume periodicity in circumferential (curved) direction such as PANDA-2 are not applicable. Innovation: In general all programmes developed within the BUCKBLADE project describe at least buckling of prismatic double curved orthotropic panels under bi-axial loading. The features with respect to the existing methods are: -1. The geometrical description of the panels has a transverse curvature that is non-uniform over the width. -2. The longitudinal loading may be non-uniform in over the panel width. -3. The pre-buckling deformation is included in terms of: -A. Out-of-plane deformation calculated from out-of-plane equilibrium. -B. Longitudinal curvature as occurs for a rotor blade (in general a beam) under bending. -4. The effect of an elastic medium supporting the panel on one side, such as for rotor blades with a foam interior. In addition to these aspects each of the programmes described here have the specifications: STABLAD, Stability analysis Tool for Anisotropic rotor BLADe panels. -1. Modelling of full anisotropic material properties. -2. Panels with sandwich structure. -3. Geometric twist. -4. Shear loading. IMPANAL, Imperfect Panel ANALysis: -1. Calculates the maximum load of a panel with initial geometric imperfections. -2. Buckling under an in-plane bending moment is described with a multi-mode deformation. CLAMPED, calculates the bifurcation load of panels with clamped edges. Although this tool does not give conservative predictions it can be used in combination with the other tools in order to estimate the possible influence of stiffness of the joints within the structure. When used with proper input, the buckling loads calculated with these tools are close to- or somewhat below the critical loads of the real structure. Other Technology: The theoretical description of the programmes is based on laminate theory and on Donnell’s quasi-shallow shell assumptions for thin-walled shells. For correct material properties it is recommended to perform tests on pieces of the same material. For a realistic estimate of the geometric imperfection one needs statistical information on the geometry of products with the same material and manufacturing process.