cut sections / edges: connection of iso 9013 to fatigue · cut sections / edges: connection of iso...
TRANSCRIPT
Cut sections / edges: connection of ISO 9013 to fatigue
3rd Nordic Conference on design and fabrication of welded structures Waterfront Conference Center - 29 Sept 2016
Stockholm / Sweden
Bertil JonssonBerjo Weld Design AB
Contents
• Background
• Cut section & edges
• Tests & roughness
• Summary
Contents
• Background
• Cut section & edges
• Tests & roughness
• Summary
Motivation
Kitigawa diagram
Material strength important
Defects important
Fabrication quality levels
How take defects into accountin design, fabrication & inspection ?
STANDARD
GU
IDEL
INE
Combine Standard & Guideline !
Quality Levels FAT-levels
For production processes: defect governs in most cases
VCE:Quality levels: VE, VD, VC, VBSTD 181-0004Weld design guidelineAnalysis guideline
VCE:Defect levels: 2-3-4-5-6STD 330-0002 & 330-0003VPD Guideline for cast iron & steel
VCE:Quality levels: Range 1 – 2 – 3 – 4Following ISO 9013 (RZ)Guideline for design & analysis
Contents
• Background
• Cut section & edges
• Tests & roughness
• Summary
Test-results from SSAB & others
0
100
200
300
400
500
600
0 500 1000
Fati
gue
stre
ss r
ange
at 1
E6,
R=0
, me
dia
n (
Mp
a)
Yield strength Re (Mpa)
SSAB - Rz 10
SSAB - Rz 30
SSAB - Rz 60
SSAB - Rz 120
SSAB - Rz 180
Fat.strength=Δσ* / Kr
Δσ*=9,8989*Re^0,6071
Kr=1/(1-0,000254*Rm*Ln(1+Rz/6))
Rm=144+0,877*Re
Roughness & yield
Roughness (RZ) in ISO 9013
0
50
100
150
200
250
300
350
0 20 40 60 80 100 120
RZ (μm)
t (mm)
Range 1
Range 2
Range 3
Range 4
Ex of tables (1 of 13), t = 10 mm
Range 1 Range 2 Range 3 Range 4
RZ < 17 RZ < 49 RZ < 83 RZ < 130
Re (Mpa) ∆σ 50 % ∆σ 50 % ∆σ 50 % ∆σ 50 %
235-355 237 212 198 186
355-550 288 245 222 202
550-750 334 263 224 202
750-950 362 263 224 202
Range Quality level (1-4) of cut section according to ISO 9013RZ Roughness parameter [μm]Re Material yield limit [Mpa]∆σ 50 % Median fatigue stress range at 2Ee6 cycle
Start-point
Further test neededLack of knowledge
Tickness > 12 mmRZ > 120 μmConstant vs. Variabel amplitude (CA / VA)Influence on treated edge, use STD 102-0008 ?Which Wholer inclination should be used 3, 4, 5 or 6
Suggested testing of (co-oper btw VCE, KTH & SSAB)
Thicknesses t15, t25 & t50 mmMaterial Weldox Re=355, 700 & 900 MpaCut processes Laser, Plasma & GasLoads tension & bending + CA vs VA
Totally fatigue tests of appr 370 samples
SSAB will do 250 & VCE/KTH will do 120 samples
No of test samples & test-types
Geometry of sample(same for all thicknesses)
580 mm
48 mm
Measures used when assessing the plate area needed: 600*50 mm(Investigation of small distance btw cut edges gave no diffeence in fatigue)
Contents
• Background
• Cut section & edges
• Tests & roughness
• Summary
Pictures
• Measures: Rz and Ra
• Positions: at the edges & middle of section
Surface Roughness Measurement
Generally poor quality
XIII-WG4-142-16
Fatigue testing
S700 S960
XIII-WG4-142-16
Residual Stress Measurement
Majority of specimens are subjectedto compressive residual stresses
Oxygen and Laser cut specimens may show a higher fatigue strengthcompared to the surface roughness
XIII-WG4-142-16
Contents
• Background
• Cut section & edges
• Tests & roughness
• Summary
Fatigue result
Fatigue strength 10-30% higherthan predicted using ISO9013:2002
ISO9013:2002 is conservative witha weak link to fatigue
XIII-WG4-142-16
IIW Recommendation
XIII-WG4-142-16
Eurocode 3
XIII-WG4-142-16
Summary
• A connection to fatigue for cut surfaces is outlined– Based on tests from SSAB + ISO 9013 quality levels– Gives fatigue data as fcn of
• Roughness (RZ)• Thickness (t)• Yield (Re)
• Status– Roughness partly outside ISO levels– Fatigue tests indicate conservative results– Cut process best list: water –> laser / plasma –> gas
Thanks for your attention !
Questions ?