validation and case studies

(01 May 2006) FITNET MK7Pm ≤ 0.67S′y(equation (6.1) of Volume 2/3)1.633 ≤ 0.67 x 170 = 113.9 PASSEDPL + PB ≤S′y(equation (6.2) of Volume 2/3)138.3 ≤ 170 PASSED(PL + PB + Q) ≤ 2.7S′y(equation (6.4) of Volume 2/3)276.6 ≤ 2.7 x 170 = 459 PASSEDIt can be seen that the margins against plastic collapse are demonstrated for the uncracked structure.6.4 Determine Whether Creep is Significant (Step 4)Note that the following check has been applied to the uncracked body. A further check on the significance ofcreep is carried out in Step 6 of Volume 4/5. Creep can be neglected if:∑j⎡nj ⎢⎣tmt( T )ref⎤⎥⎦j≤ 1(equation (6.5) of Volume 2/3)(A8.104)where t is the hold time, nj is the number of cycles of type j and tm is determined from Volume 2/3 Figure5.3(a) at a temperature of 650°C as approximately 1.25 hours. Only the creep-fatigue cycles need beconsidered, of which there are 3129 at 1 hour each, and therefore creep is significant for the uncracked body.Demonstrate that Creep Rupture Endurance is Satisfactory (Step 5)Demonstration that creep rupture endurance is satisfactory is not necessary at this stage as calculationsperformed in Step 7 of Volume 4/5 cover this area.6.5 Perform Simple Test for Shakedown and Check for Insignificant Cyclic Loading (Step 6)6.5.1 Simple test for global shakedownIt must be shown that elastic linearised stresses are lower than the modified yield limit (KsSy) for all times andpositions. From Section A8.8.34, Ks = 1.05. Taking the most onerous position at the plate surface at thepeak of the creep-fatigue cycle gives:Δσlin( x, t) ≤ KsSy(equation (6.11) of Volume 2/3)(A8.105)138.3 ≤ 1.05 x 170 = 178.5 PASSEDThus, the simple test for global shakedown has been satisfied for the uncracked plate.6.5.2 Check for insignificant cyclic loadingThe following check has been made to determine whether the plate is in strict shakedown:el, max( KsSy) ( KsSy)cncΔ σ ≤ +(equation (6.14) of Volume 2/3)(A8.106)276.6 ≤ 2(1.05 x 170) = 357 PASSED© FITNET 2006 – All rights reserved 13-143