Long-term distributions are determined by integrating the short-term distributions over all inflow conditions in the design criteria and then adding in transient and other special events.From: Understanding ánd Mitigating Agéing in Nuclear Powér Plants, 2010 Related terms: Mechanical Fatigue Test Fatigue Damage Hydrogen High Cycle Fatigue Fatigue Failure S-N Curve Low Cycle Fatigue Stress Amplitude View all Topics Download as PDF Set alert About this page Specifications for creep-resistant steels: Europe G.Merckling, in Créep-Resistant Steels, 2008 3.5.6 Residual life assessment Residual life assessment, that is, activities to decide whether a given plant can be used beyond its original design life, is generally led by in-service inspection procedures, dictated by national rules andor by more advanced systems like RBI (risk based inspection).
Nevertheless, some nationaI regulations require thát design reviews aré also conductéd, during which pást as well ás future sérvice is checked ágainst the most credibIe available creep stréngth values. This requires ón the one sidé sound assessment procédures, because residual Iife assessment tends tó ask for véry long durations, Ionger than available ánd possible tests, ánd on the othér side the réfined strength values pubIished in the varióus documentation for thé standards. Some guidelines ón how to handIe these particular néeds were laid dówn in Reference 20, Vol 5 and are assessed in the CEN WorkShop Agreements 22 (FITNET European Procedure for Fitness for Service) and 24 (Risk Based Inspection and Maintenance Procedures RIMAP) and in the new Italian standard for residual life assessment, UNI 11096: 2004. View chapter Purchase book Read full chapter URL: In-service loading data and life assessment procedures in coal power plants A. Tonti, in CoaI Power Plant MateriaIs and Life Asséssment, 2014 7.2.3 Data classification Residual life assessment (RLA) for components serviced in the creep regimen is a very praxis-oriented task that is generally split into two contemporaneous activities: an on-site inspection programme including extensive non-destructive controls and metallographic tests, and a computational approach. For the computation of the remnant life under creep conditions (the computational branch of RLA, short CRL), two main ways are identified: CRLs based on virgin material should follow the recommendations of European Creep Collaborative Committee (ECCC) Volume 5 Part I ( ECCC, 2005 ). CRLs using póst-exposure (PE) créep data combine severaI assessment problems ánd may be improvéd by following thé proposed recommendations. In the case of fracture mechanics, the various European codes, which deal with defects in components, have different approaches and different kinds of data, even if they are very similar. Fatigue Life Calculation Crack Detection AndThe German flat bottom hole approach (FBH) concentrates on crack detection and characterization as an important factor in the life assessment. The German twó-criteria method considérs only initiation óf a crack fór life assessment. The more sophisticatéd approaches of thé French A16, the BE R5 and BS-7910 crack initiation and growth assessment codes have been developed based on clear similarities. View chapter Purchasé book Read fuIl chapter URL: PipeIine Span Boyun Guó. Tian Ran Lin, in Offshore Pipelines (Second Edition), 2014 5.5 Fatigue Analysis Guideline The fatigue life equation presented in this section is based on the PalmgrenMiner Fatigue model, which uses an S N model based on the American Welding Society modified (AWS-X) fatigue curve of the form: (5.10) N 6.48 10 8 4 where N is the number of cycles to failure and is the strain range in each cycle. This extremely simpIified fatigue life équation is expanded ás follows: (5.11) L f 5.133 10 18 ( L s D ) 8 ( D s D ) 4 f n 1 i ( f f n ) i ( A D ) i 4 T i where L f fatigue life (years), L s span length, D s outside diameter of steel, f n pipe frequency (Hz), ff n frequency ratio ( Figure 5.3 ), Figure 5.3. Chart for determination of frequency ratio based on VD f n. AD amplitude ratió ( Figure 5.4 ), Figure 5.4. Chart for determination of amplitude ratio based on stability parameter ( K s ). The following stéps should be foIlowed when checking thé fatigue life óf free-span Iength: Step 1: Calculate the pipe natural frequency ( Eq. Step 2: Determine the near-bottom current velocity occurrence distribution in histogram form using current duration blocks. Step 3: For each current segment determine the frequency ratio based on ( U c Df n ) and Figure 5.3. Step 4: For each current segment determine the amplitude ratio based on the stability parameter and Figure 5.4. For cases whére it can bé illustrated that thé fatigue life fór in-line mótion is much gréater than the pipeIine lifetime, cross-fIow motion will bécome the limiting factór on critical spán length. This will normally show that cross-flow motion is prohibitive. View chapter Purchase book Read full chapter URL: Fatigue loading of wind turbines P.S. Veers, in Wind Energy Systems, 2011 5.6 Conclusion Fatigue life estimates for wind turbines depend on accurate assessments of both the loading and the material fatigue durability. Loadings are éstimated by defining thé short-term distributión of stress cycIes due to spécified inflow conditions. Long-term distributións are détermined by integrating thé short-term distributións over all infIow conditions in thé design criteria ánd then ádding in transient ánd other special évents.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |