New software for natural vibration modes analysis

Simulation software designer Cobham Techni- cal Services has extended the multiphysics capabilities of the Opera-3D design software, a finite element analysis environment for electromagnetic design in three dimensions, by incorporating a new solver that can analyse natural vibration modes.

“The new modal solver, known as STRESS/EV, finds a user-specified number of eigenvalues within a specified frequency range and calculates the eigenvectors of each mode. It works in conjunction with the static stress analysis capa- bility of Opera-3D, which calculates the deformation, stresses and strains of a body, which, in turn, is subjected to external and internal forces. The forces calculated from electromagnetic fields can be used as input for the stress analysis,” says Cobham Technical Services senior applications engineer Jeremy Howard-Knight.

He explains that the STRESS/EV accommodates iso- tropic, orthotropic and fully aniso- tropic materials, the properties of which can be specified as a constant or an expression. The program uses Young’s modulus, which is a measure of the stiffness of an elastic material; Poisson’s ratio, which is a negative ratio of transverse to axial strain; and the shear modulus of the material, which is the coeffi- cient of elasticity for a sharing force, together with its elasticity matrix, if it is fully anisotropic.

“This new Opera-3D feature was developed partly from feedback from existing Opera users, especially those working in the environment of electrical machines area. The first sales have been to such clients and, especially, those involved in large capital project-type electrical machine design. Opera-3D is used for all kinds of electro- magnetic design, but Cobham has a large number of users in the electrical machine sector,” Howard-Knight points out.

The company says the tool is expected to prove particularly useful for electrical machine developers, which can employ it to investigate and reduce forces that might cause oscillations close to the natural frequencies of the equipment and, thereby, avoid excessive vibration or collisions between rotating and stationary parts.

“By capturing such mechanical vibration in conjunction with electromagnetic modelling and thermal performance, if required, the integrated three-dimensional tool suite can greatly reduce the complexity and timescales of design projects. One of the key benefits of this capability is a further reduction in the creation of physical prototypes to explore the behaviour of a proposed design concept,” Howard-Knight explains.

He adds that finite element simulation is the most practical tool for exploring design concepts and validating device performance. The adoption of this approach from the outset of the design cycle can stimulate innovation and lead to end products that are correct first time.

A better understanding of new designs is made possible by more thorough simulation; therefore, it is possible to reduce the real-world prototyping phase to a few iterations. This can shorten the design cycles by months and reduce the associated high costs.

Also, with engineering skills being at a premium, design automation using computer modelling is an extremely effective investment for companies, as it ensures successful products and a continuing flow of design ideas.

“This latest version of the software extends the fundamental performance advantage of Opera-3D for many common design engineering applications,” highlights Howard-Knight.