Guidelines for the use of the results of elastoplastic FEM
The Institute for Advanced Materials of the European Commission's Joint Research Centre has published an invitation to tender concerning the development of guidelines for the use of results obtained by the elastic finite element method (FEM) in the design of pressure vessels. Pressure vessel design standards have traditionally been based on design by formula (DBF) rules. With developments in computing and of the elastic finite element method (FEM), alternative design by analysis (DBA) methodologies have been introduced as optional design routes. The DBA methodology most frequently applied is the stress categorization method (SCM), where the membrane and bending stress components are evaluated from the results of FEM stress analysis. The ready availability of increased computing power offers today's designers the possibility of performing elastoplastic FEM stress analyses. In many respects, however, the DBA methodology has not developed to the same degree so the SCM approach is often difficult to apply for complex geometries and loading conditions. The challenge is to establish guidelines for the use of the results of elastoplastic FEM analyses to establish safe design limits for pressure equipment. The draft version of the new European unfired pressure vessel standard (hereafter referred to as the European Standard) proposes such a methodology, based on the concept of limit load analysis, in addition to the more familiar SCM method. This so-called direct route bypasses the commonly encountered difficulties associated with the application of the stress categorization method. The new method is, however, largely untested by industry and it is envisaged that considerable investment in time will be required to promote its obvious benefits. It is also the case that DBA methodologies are not readily adopted by the pressure equipment industry, which generally prefers to follow the DBF route. The extent to which this is the case and the reasons for this result need to be accurately established. With this information it is an objective of this project to present a series of proposals and measures to encourage and facilitate the wider usage of DBA methodologies by the European pressure equipment industry. Further details are given in the tender specifications. The study must be completed within 18 months. Tender documents may be obtained from: European Commission Joint Research Centre Institute for Advanced Materials Purchase Department Westerduinweg 3 Postbus 2 1755 ZG Petten The Netherlands Completed tenders should be sent to the same address.