Finite Element Analysis
Finite Element Analysis (FEA) allows Tods to undertake the design of complex engineering structures for the Defence and Civil markets.
Tod finite element software has composite capability where layered composite materials with different fibre angle orientations can be modelled in order to provide structural optimisation. The range of structural analysis capability covers non-linear, dynamic, fatigue, transient, forced response, eigenvalue and buckling.
Fluid Structure
Fluid structure interaction is modelled by coupling structural finite elements with fluid finite elements, boundary elements and wave envelope elements. This allows the solution of a wide class of problems ranging from the dynamic response of fluid loaded structures to acoustic interaction. Applications include the design of sonar domes subjected to sea going loads and underwater explosive shock, the design of baffling to prevent multi-pathing within the sonar array space and the modelling of acoustic materials.
Stealth Structures
Modern warships are increasing using stealth measures to reduce early detection. The methods employed to achieve a lower RCS are as follows:
Radar Absorbing Material (RAM) applied to existing shape (for retrofit market) radar reflective materials (using embedded reflective surfaces) shape (minimising detail and providing optimum angles minimising reflection in receiver direction).
Acoustic Design
Material development for specific acoustic applications use multi-layer modelling techniques to predict transmission / reflection characteristics. Relevant acoustic wave speeds are characterised over a range of incident angles. A similar approach is used for insertion loss measurements.
Modelling of a sonar system including the outboard array and beam former can be modelled with the sonar dome to predict degradation of beam patterns. Internal reflections within the sonar dome can be modelled to optimise the array / dome geometry and acoustic baffle design.
Electromagnetic Design
Tods preferred radome skin design utilises a sandwich construction of a closed cell foam core with internal and external GRP skins. This provides a high structural specific strength and the ability to tune the electromagnetic properties of the radome by varying the cross sectional thickness.
The principles employed for accurate electromagnetic design include the use of verified Tods codes such as ETRANS and RAPS.
The scattering of electromagnetic waves by the radome joints between panels is modelled by IFR (Induced Field Ratio) methods assessing the far-field scattered energy and distortion of the antenna patterns.
FDTD (Finite Difference Time Domain) methods are used to verify the above models and to provide detailed information on how the joints interact with the propagating radar wave.
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