The finite element process requires that a determined extent of physical geometry is modelled mathematically using numerous discrete 'elements'. These 'elements' are pre-formulated for the analysis and are populated with, for example, the material stiffness or thermal properties. Each element possesses a known response to loading. They are tied together in a stiffness matrix system to which boundary conditions and loadings are applied. The analytical process 'solves' for field variables such as temperature, displacement or stress, either in time or time independent solutions as required. Linear elastic solution is straightforward but if a solution is highly non-linear, for example, using contact or cavity radiation, many hours of CPU time to compute and many megabytes of disc space may be required. From the output, generally graphical post processing provides an interpretation of the data which is assessed against pre-determined criteria. Much more detailed and comprehensive criteria are applied for nuclear related and other high integrity designs.
Finite element analysis is suitable for a wide range of applications in the power and process industries. In existing plant, failures, particularly where driven by thermal transients or un-optimised operational procedures, are not easy to calculate and explain using classical theory, so FEA can be used to demonstrate cyclic damage potential.
Although a great many organisations offer consultancy services with a wide variety of finite element modellers and solvers, Doosan Babcock has a history of demonstrated applied experience directly relevant to the power and process industries with an in-depth application of ABAQUS. Fully auditable quality assurance procedures are available and long term archiving, particularly for nuclear contracts requiring data to be retained for the plant life, can be arranged.
For new build plant, increasing confirmation is being required by owners that the plant will perform as designed for the applied cyclic loading. FEA has been applied to identify weaknesses in geometry (which then can be better optimised, or direct inspection and maintenance scheduled) or demonstrate better operational procedures for increased life, and as these are applied, reduce unplanned shutdowns.