The Life Assessment Method R5 is widely used for the assessment of power plant at high temperatures. The procedure involves the application of a sequence of rules that provide margins of safety against a range of possible failure modes, plastic collapse, ratchetting, fatigue failure, creep rupture and creep/fatigue interaction. Within R5 this is achieved by using limit load and shakedown methods, combined with Neuber’s rule and the evaluation of elastic follow-up factors. In recent years, the Linear Matching Method has been developed so that it is capable of providing optimal solutions for each of these criteria, thereby giving less conservative margins of safety, but adopting the same use of material data as R5. The paper describes a detailed comparison between the approach currently used in R5 and the result of the application of the Linear Matching Method, for the entire range of failure modes and for a simple example. The purpose of this comparison is to assess the circumstances where Linear Matching Methods may have a distinct advantage over current methods. The example consists of a square plate containing a circular hole. The plate is subjected to uniaxial loading and a radial varying temperature field. For all failure modes the Linear Matching Method gives less conservative results compared with standard R5 methods. The differences can be very significant, particularly for the prediction of strength limits; limit load, shakedown load and ratchet limit. Significantly lower and less conservation elastic follow-up factors were also obtained. The comparison demonstrates the advantages of the Linear Matching Method in this context.

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