The LICON approach to life management

The prediction of long-term high-temperature material properties is difficult when the prediction is based on normal short to medium-term uniaxial creep test results. The test acceleration achieved by increasing either test temperature or stress or both, easily leads to deformation mechanism changes, which makes the prediction unreliable. In a short-term uniaxial laboratory test it is impossible to produce the same type of creep damage as observed in power plant components which have been in operation for more than 100 000 hours. An alternative method has been proposed based on using multiaxial test specimens. This concept was tested in the LICON project (BE95-3019, 1996-2001), where the theoretical basis of the method was developed and verified experimentally for three steels in base material and welded condition by using several different multiaxial laboratory specimens and full-size test components. A typical test campaigne required to apply the methodology is a series of creep crack growth tests on standard CT specimens to 0.5 mm crack extension and test durations between 1.000 and 10.000 hours. A comprehensive Code of Practice document was produced in the project, and this will be published later in 2007.