AM 11/03 1 VII Improving the fatigue life of weldments AM 11/03 2 Outline n Obvious things to do n Problems the weld toe n Fatigue life Improvement Strategies n Light and heavy industry weldments n Improving the “bad” weldments AM 11/03 3 Crude! (bad) AM 11/03 4 Better AM 11/03 5 Bad - planar weld discontinuities AM 11/03 6 Outline n Obvious things to do n Problems the weld toe n Fatigue life Improvement Strategies n Light and heavy industry weldments n Improving the “bad” weldments AM 11/03 7 Weld toe is a stress concentration AM 11/03 8 Slag entrapments at toe? Virtually eliminates fatigue crack initiation life NI AM 11/03 9 Welding procedure A Welding procedure B Cold-lap defects at weld toe Cold laps virtually eliminate the fatigue crack initiation life (NI) Such weldments may have an appreciable fatigue crack initiation life (NI) “Nominal” “Perfect” AM 11/03 10 Cold lap at a weld toe Loading Direction D Weld Metal Base Metal Heat Affected Zone Weld Toe Location Without Cold-Lap Defect Curved Path Vertical Path θ r φ [...]... 32 Outline n n n Obvious things to do Problems the weld toe Fatigue life Improvement Strategies n Light and heavy industry weldments n Improving the “bad” weldments AM 11/03 33 Light, heavy industry weldments • Light industry weldments are presumed to be fabricated from 1/2” or smaller plate and not to have large fabrication stresses • Heavy industry weldments are presumed to be fabricated from larger... fab 0 50 100 150 • Sfab ˜ SYBM 200 Base Metal Ultimate Strength, Su (ksi) BM AM 11/03 21 Outline n n Obvious things to do Problems the weld toe n Fatigue life Improvement Strategies n Light and heavy industry weldments Improving the “bad” weldments n AM 11/03 22 Good - grind off reinforcement AM 11/03 23 Good - burr grind weld toe AM 11/03 24 Very good - full face grinding AM 11/03 25 Shot peened weld... 8 Cold Lap Length, L (mm) cl AM 11/03 20 Predicted effect of SuBM Trends in “Ideal” 1.0-in plate thickness, non-load carrying cruciform weldments fatigue strength Fatigue Strength at 1E+07 cycles, Sa (ksi) 60 Q & T Steel Hot Rolled Steel 50 Over Stressed 40 •R=0 30 Stress Relieved As Welded, S = 0 fab 20 10 0 • Welding residual stresses = 50% of SYBM As Welded, S = SyBM fab 0 50 100 150 • Sfab ˜ SYBM... large fabrication stresses AM 11/03 34 Light industry weldments Remote Stress Range, ∆S (ksi) 100 t = 0.5-in (12mm); R = 0 Without Fabrication Stresses Ideal Nominal 10 Toe Ground (radius = 0.1 in.) Over Stressed Stress Relieved Weld Profile (flank angle 20 o) As Welded 1 4 10 10 5 10 6 Fatigue Life, N AM 11/03 10 T 7 10 8 (cycles) 35 Heavy industry weldments Remote Stress Range, ∆S (ksi) 100 t = 2.0-in... Remote Stress Range, ∆S (ksi) 100 t = 2.0-in (50 mm); R = 0 With Fabrication Stresses Ideal Nominal 10 Toe Ground (radius = 0.1 in.) Over Stressed Stress Relieved Weld Profile (flank angle 20 As Welded o ) 1 10 4 10 5 10 6 Fatigue Life, N AM 11/03 10 T 7 10 8 (cycles) 36 ...Effect of cold lap depth K Weld geometry correction factor, MK 10 2-D FEM D = 0.0 mm, MK CG, curved path from weld toe location D = 1.0 mm, MK CG, curved path from cold-lap defect D = 1.0 mm, MK CG, vertical path from cold-lap defect 1 0.001 AM 11/03 0.01 0.1 Crack length / main plate thickness, (a/T) 11 Effect of flank angle 10 Weld geometry correction factor,... 11/03 25 Shot peened weld toe AM 11/03 26 Remelted weld toe (laser) AM 11/03 27 Improvement Strategies TWI suggestions as to weld improvement procedures AM 11/03 28 Improvement strategies θ 15° 30° 45° Fatigue Strength (ksi) at 106 cycles 100 Shot Peen 15° 30° 45° Residual stress 10 15° 30° 45° Geometry Over Stressed plate Plain Stress Relieved As Welded Base metal strength 1 AM 11/03 1 100 Base metal... thickness, (a/T) 11 Effect of flank angle 10 Weld geometry correction factor, MK K 2-D FEM θ = 30o θ = 45o θ = 60o D = 1.0 mm 1 0.001 AM 11/03 0.01 0.1 Crack length / main plate thickness, (a/T) 12 Effect of cold root radius 10 Weld geometry correction factor, MK K D = 0.00 mm, weld toe location D = 2.00 mm, r cl = 0.146 mm D = 2.00 mm, r cl = 0.025 mm 1 0.001 0.01 0.1 Crack length / main plate thickness, . 1 VII Improving the fatigue life of weldments AM 11/03 2 Outline n Obvious things to do n Problems the weld toe n Fatigue life Improvement Strategies n Light and heavy industry weldments n Improving. industry weldments n Improving the “bad” weldments AM 11/03 7 Weld toe is a stress concentration AM 11/03 8 Slag entrapments at toe? Virtually eliminates fatigue crack initiation life NI AM. at weld toe Cold laps virtually eliminate the fatigue crack initiation life (NI) Such weldments may have an appreciable fatigue crack initiation life (NI) “Nominal” “Perfect” AM 11/03 10 Cold