1、 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 1 GUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS (FOR THE SFA OF SFA (years) CLASSIFICATION NOTATION) JANUARY 2004 NOTICE NO. 3 November 2009 The following Changes become EFFECTIVE AS OF 15 NOVEMBER 2009. (See htt
2、p:/www.eagle.org for the consolidated version of the Guidance Notes on Spectral-based Fatigue Analysis for Vessels 2004, with all Notices and Corrigenda incorporated.) Notes - The date in the parentheses means the date that the Rule becomes effective for new construction based on the contract date f
3、or construction, unless otherwise noted. SECTION 8 FATIGUE STRENGTH (Revise third and fourth paragraphs of Subsection 8/3, as follows.) 3 S-N Data (15 November 2009) To provide a ready reference, the S-N Data recommended by ABS are given in Appendix 2 of this Guide. (Note: source United Kingdoms Dep
4、t of Energy (HSE) Guidance Notes, 4thEdition.) There are various adjustments (reductions in capacity) that may be required to account for factors such as a lack of corrosion protection (coating) of structural steel and relatively large plate thickness. The imposition of these adjustments on fatigue
5、capacity will be in accordance with ABS practice for vessels. There are other adjustments that could be considered to increase fatigue capacity above that portrayed by the cited S-N data. These include adjustments for compressive “mean stress” effects, a high compressive portion of the acting variab
6、le stress range and the use of “weld improvement” techniques. The use of a weld improvement technique, such as weld toe grinding or peening to relieve ambient residual stress, can be effective in increasing fatigue life. However, credit should not be taken of such a weld improvement in the design ph
7、ase of the structure. Consideration for granting credit for the use of weld improvement techniques should be reserved for situations arising during construction, operation or future reconditioning of the structure. An exception may be made if the target design fatigue life cannot be satisfied by oth
8、er preferred design measures such as refining layout, geometry, scantlings and welding profile to minimize fatigue damage due to high stress concentrations. Grinding or ultrasonic peening can be used to improve fatigue life in such cases. The calculated fatigue life is to be greater than 15 years ex
9、cluding the effects of life improvement techniques. Where an improvement technique is applied, full details of the grinding standard including the extent, profile smoothness particulars, final weld profile, and improvement technique workmanship and quality acceptance criteria are to be clearly shown
10、 on the applicable drawings and submitted for review together with supporting calculations indicating the proposed factor on the calculated fatigue life. Notice No. 3 November 2009 2 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 Grinding is preferably to be carried out by ro
11、tary burr and to extend below the plate surface in order to remove toe defects and the ground area is to have effective corrosion protection. The treatment is to produce a smooth concave profile at the weld toe with the depth of the depression penetrating into the plate surface to at least 0.5 mm be
12、low the bottom of any visible undercut. The depth of groove produced is to be kept to a minimum, and, in general, kept to a maximum of 1 mm. In no circumstances is the grinding depth to exceed 2 mm or 7% of the plate gross thickness, whichever is smaller. Grinding has to extend to areas well outside
13、 the highest stress region. The finished shape of a weld surface treated by ultrasonic peening is to be smooth and all traces of the weld toe are to be removed. Peening depth below the original surface is to be maintained at least 0.2 mm. Maximum depth is generally not to exceed 0.5 mm. Provided these recommendations are followed, an improvement in fatigue life by grinding or ultrasonic peening up to a maximum of 2 times may be granted.
