NUMERICAL STRESS ANALYSIS

Determine and visualise stressing and deformation

Standard design methods, such as those provided in design standards, are simplified and conservative. During service, the actual operating loads on equipment may vary significantly from design. Similarly, degradation of the equipment may bring in to question the ability of the equipment to continue to operate safely and reliably. In such cases, it is necessary to obtain a more accurate understanding of the levels and distributions of stress within the equipment.

Bureau Veritas provides numerical stress analysis services. Based on the Finite Element Method, this analysis permits the calculation and visualisation of stresses and deformations resulting from applied loads. With stresses accurately calculated, actual safety margins over material strength can be determined.

This Finite Element Analysis (FEA) approach to design is recognised within the design standards as being an appropriate alternative to simpler calculation by design formula.

FEA releases the engineer from the constraints of engineering formulae as FEA has no restriction on complexity of shape or loading. Therefore complex geometries may be accurately assessed and time dependant load histories may be applied. Loading types can include force, restraint, pressure, temperature, gravity and dynamic loads. The material response may be elastic or elasto-plastic or time dependant. FEA is particularly suited for transient events such as impacts and shock loads, both mechanical and thermal.

With an accurate visualisation of the stress distribution resulting from operation, it is possible to proceed to determine the remaining strength or life and to undertake less conservative fitness for service assessments. As changes to the numerical models are relatively easy to make, it is possible to investigate the beneficial effect on integrity and life resulting from design changes and changes in operating modes. Such sensitivity analysis saves significant time and effort in comparison to undertaking trials on the equipment itself.

FEA is an integral part of advanced fitness for service assessment, where the margins of conservatism resulting from basic analytic methods need to be reduced.

What are the key benefits?

- Provides accurate visualisation of stresses and deformation under a wide range of applied loads.
- Provides stress calculations for cases where analytic solutions do not exist.
- Allows “what if” analysis of design changes and changes in operating parameters without resorting to prototype testing.
- Provides accurate stress profiles for defect tolerance assessments.
- Allows structural optimisation through the redistribution of material as required to resist the applied loads whilst maintaining acceptable stress levels.