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For welds with overlaps – consider the above to make TIG welding easier. ½” weld size seems excessive, but the re-analysis will take time (at least 1 day/run). Weld Geometry A-B Flange:A Possible Alternate to the Extended Shim/ Double Fillet Weld.
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For welds with overlaps – consider the above to make TIG welding easier. ½” weld size seems excessive, but the re-analysis will take time (at least 1 day/run) Weld Geometry A-B Flange:A Possible Alternate to the Extended Shim/ Double Fillet Weld Grind 300 chamfer to improve TIG access. This is necessary to improve fusion to surfaces. 3/8” or 0.289” ?? 2” worst case 1/2” –
Double Fillet Weld • Fastest and easiest • But more distortion • Can easily peen to reduce distortion. • Candidate for testing. • NOTE: have to be sure there is enough “shelf” for this. • CONCLUSION: USE THIS FOR A-B WELD GEOMETRY. • Proceed without clamp bolts – add if needed. • Improvise clamping as needed.
For welds with overlaps – consider the above to make TIG welding easier. ½” weld size seems excessive, but the re-analysis will take time (at least 1 day/run) 2” worst case Weld Geometry A-B Flange:A Possible Alternate to the Extended Shim/ Double Fillet Weld Grind 300 chamfer to improve TIG access. This is necessary to improve fusion to surfaces. 3/8” or 0.289” ?? 1/2” –
Casting Weld Test B6 and A6 • Shim and bolt casting as it will be. • Use steel shims but fit as it really will be. • Outboard Shim drawings available this afternoon. Loose fitting central hole. Non-coated shims will be used for this test. • Inboard shims: go with U feature, ½” radius, ½” tab, ½” deep. (may need to adjust depth depending on analysis. Bill thinks it’s OK). Drawings early next week. • Torque bolts to 100% value for through bolts; 75% for tapped bolts. • 316 LN weld shims (bar stock?) or 5/8” thick plate. All shims: water jet cut, grind to thickness, anneal/rapid air cool/check permeability. MV will order material. • Lincoln weld wire • Peen intermediate weld passes. • Monitor distortion during welds with laser scanner. • Jim will ask Steve to measure B6 and A6 next week.
Pre-Casting Weld Tests • Use water jet cut A-B flanges. • Use 316-LN shims with U feature and without. • Use clamp bolts to simulate casting restraint somewhat. • Use Lincoln weld wire; keep temp to ~300F. • Mike Cole will make the CAD model. (2) flanges with 4” shims ½” thick. • Monitor distortion during welding with laser scanner. • MC will give shim profile. • Target date: week of June 25 to perform tests. • We’ll use 316 L for this test.
Casting-Casting Demo Weld Test • Casting-casting weld test: • Use actual shim design details. • Water jet cut, grind to thickness, anneal • Monitor distortion during welds with laser scanner. • Peening should be considered on inter-passes.
Fatigue Considerations • Fatigue analysis is not extremely sensitive to material properties– often carbon steel properties is adequate. (ref. Fatigue Strength Analysis of Offshore Structures). • British Standard 7910 address flaw size assessment. • Bill suggests doing a preliminary assessment to get a handle on sensitivity. • Center crack panel is ok but tension test capacity may be an issue. • EWI uses single edge notch bend tests.
Design standards for fatigue • Structual Welding Code for Steel • Has table for different geometries. • Grade of material based on yield not much of an issue. • Shear on throat of welds 8 ksi (55 MPA) in their fatigue design table. • This suggests NCSX is close to threshold for shear fatigue for 5 million cycles. • Since NCSX fatigue life of 4 x 130,000 for flaw size fracture analysis is about 1/10 of this, we’re probably OK. • Possible for EWI to compare our shear values & NCSX’s N to a number of code criteria. • Will do. Kevin will supply peak shear locations (peak values). • Irv will get (3) center crack panels made and tested. • Size and details will be determined after discussions with Westmorland. • Effect of 77 K is relatively small – minor differences in elastic properties between RT and 77K. • If state is mostly elastic, it really doesn’t matter much of stress range or strain range is used. • Question: how much weld does NCSX need, given we have discrete shims?
Clamping • Flange geometry will not permit clamping pressure to be applied where you need it – behind the welds! • Peening should be tried. • Bolts will improve clamping and should be retained. • Butting the shims together to make a continuous weld possible IS NOT a good idea – the shim intersections will probably result in stress concentrations that will crack though the welds. • Outer bolts will be fully torqued prior to welding.
