Fatigue Assessment of Seam Welded Structures Helmut Dannbauer, Engineering Center Steyr

Transcription

1 Fatigue Assessment of Seam Welded Structures Helmut Dannbauer, Engineering Center Steyr The 5 th China CAE Annual Conference July 28-29, 2009, Lanzhou

2 Contents Introduction to MAGNA and Engineering Center Steyr FEMFAT WELD Features Assessment by Notch Structural Stresses Assessment by Grid Point Forces Assessment by Standards Application Examples & Correlation to Test Results Summary 2

3 Contents Introduction to MAGNA and Engineering Center Steyr FEMFAT WELD Features Assessment by Notch Structural Stresses Assessment by Grid Point Forces Assessment by Standards Application Examples & Correlation to Test Results Summary 3

4 MAGNA s Product & Engineering Capabilities Closures Closing Systems Door Modules Window Regulator Systems Electromechanical Drives Electronics Driver Assistance & Safety Systems Body Electronics Powertrain Powertrain Engineering Services & System Integration Engine-, Transmission Comp. Axle,- AWD/4x4 Sytems Mechatronics Interiors Compl. Interior Integration Carpet & Interior Trim Cockpit Systems Roof Lining Systems Roof Systems Softtops Hardtops Retractable Steel Tops Roof Modules Metalforming Chassis Systems Shaping Technologies Body Systems Seating Seat Systems & Components Headrests & Armrests Seating Hardware Systems Exteriors Front & Rear Modules Sealing Systems Lighting systems Side Sills Vehicle Engineering & Assembly Vehicle Development Vehicle Production Comp., Modules & Tank Systems Vision Systems Inside Mirrors Outside Mirrors Engineered Glass 4

5 Engineering Center Steyr - Location 5

6 Engineering Center Steyr St. Valentin: Engineering Center Commercial Vehicle Engineering Engine & Drivetrain Engineering Technology Center FEA & Durability Thermal Management CAD/CAM Low Volume Production of Components Headcount: 440 (December 2008) ~15% deal with CAE

7 Strength & Fatigue Lab, Competence Center 12-channel road simulator V8-engine bottom end test 8-channel suspension test under corrosion 6 component wheel force transducer durability test high speed railway bogie vibration test of truck cabin

8 Weld Specimen for Overlap Joint ECS Testing Date: Author: 8

9 ECS Test Bench for Overlap Joint Date: Author: 9

10 Contents Introduction to MAGNA and Engineering Center Steyr FEMFAT WELD Features Assessment by Notch Structural Stresses Assessment by Grid Point Forces Assessment by Standards Application Examples & Correlation to Test Results Summary 10

11 Data Processing in FEMFAT WELD Weld Definition FE-Model Stress Results Load Histories FEMFAT WELD Compatible to FEMFAT BASIC & MAX WELD Database Results Damage values, Endurance safety factors, Analysis report

12 Method of FEMFAT WELD Stress-Projection into Local Coordinate System Weld node σ Parallel σ Perpendicular Anisotropic strength characteristics for welding seams Stresses perpendicular and parallel to seam are critical Transformation to local coordinate system

13 FEMFAT WELD Data Base Concept $======================================================================================= $ T-Weld, Double Fillet-Weld Situation: $ $ $ Data for a node in the middle of the weld seam $ $ MNT MNB UTL1 UTL2 UTL3 UBL1 UBL2 UBL3 WTL1 WTL2 WTL3 WBL1 WBL2 WBL3 SPTO SPBO $ $ $ BEPKT 1 BEPKT 2 BEPKT 3 BEPKT 4 $ Inclination Inclination Inclination Inclination $ Cycle Endur. Cycle Endur. Cycle Endur. Cycle Endur. $ N E WELD data base Stress conc. factors S/N-curves Haigh diagrams Material influence Thickness influence Visual representation

14 WELD/SPOT Cooperation with Carmaker OEMs 1998 AUDI: test data for steel & aluminum spot welds (H-specimen) SPOT db 2003 Honda / JSAE: test data for steel welds ~ 3 mm WELD db, VISUALIZER 2005 Nissan: spot weld benchmark software MAMBA 2005 AUDI: test data for self piercing rivets (steel & aluminum) SPOT method 2006 BMW: test data for aluminum welds ~ 3 mm WELD db 2006 Daimler: development of SSZ & MSZ method WELD method Ongoing Nissan: test data for steel extended seam weld WELD db (+model?) Volkswagen: new test data for steel spot welds SPOT stiffness model Future BMW: test data for steel welds ~ 3 mm WELD db BMW / DVS: test data for weld ends WELD db

15 Contents Introduction to MAGNA and Engineering Center Steyr FEMFAT WELD Features Assessment by Notch Structural Stresses Assessment by Grid Point Forces Assessment by Standards Application Examples & Correlation to Test Results Summary 15

16 FEMFAT WELD Mesh Independency Distances of assessment points D 1 and D 2 D 1 = f ele ( 0.5 t + t ) = 1 ( 0.5 t + t ) neighbor min 2 2 D 2 = f ele ( 0.5 t + t ) = 1 ( 0.5 t + t ) neighbor min 1 2 assessment points Automatic Stress Correction

17 FEMFAT WELD Mesh Independency Fine mesh case

18 FEMFAT WELD Assessment Points Weld ends are assessed in 3 directions

19 FEMFAT WELD Mesh Independency Model 1 (reference s=2t) Model 2 Model 3 v. Mises Stress Model 4 Model 5

20 5.00 MODEL FEMFAT WELD Mesh Independency MODEL 2 New Method Without Correction Referece (Model1) Safety Factor Against Endurance Break Distance along the weld seam [mm]

21 Model 5 (Coarse) FEMFAT WELD Mesh Independency MODEL 5 Coarse Mesh New Method Reference (Model 1) Without Correction Safety Factor Against Endurance Break Distance along the weld seam [mm]

22 FEMFAT WELD Mesh Independency 2,00 1,80 1,60 Model 1 (Reference) Model 2 Model 3 Weld Seam End Endurance Safety Factor 1,40 1,20 1,00 0,80 0,60 Model 4 Model 5 Weld end is most critical regarding mesh sensitivity 0,40 0,20 0,00 without correction with correction perpendicular to seam with correction perpend. and parallel to seam

23 Contents Introduction to MAGNA and Engineering Center Steyr FEMFAT WELD Features Assessment by Notch Structural Stresses Assessment by Grid Point Forces Assessment by Standards Application Examples & Correlation to Test Results Summary 23

24 Structural Stress Method acc. Zhang (=SSZ) 1. Line forces 2. Analytical structural stresses 3. Notch stress approximations / Weld db 4. Master SN-curve

25 Evaluation of Line Forces from Grid Point Forces f N2,E1 F N2,E1 F N1,E1 f N1,E1 f 2 ( 2F ) N1, E1 = N1,E1 FN2,E1 l1 N2 l 1 N1 f 2 ( 2F ) N2, E1 = N2,E1 FN1,E1 l1 E1 Nodal element force f E = k E u E

26 Ways to Determine Line Forces Investigated methods 1 Elementaveraging 2 Nodeaveraging 3 Method competition

27 Investigations on Line Forces and Singularities Evaluation line 30mm 40mm l = 10 mm 60mm MSC.NASTRAN Quad4 Grid point forces l = 2.5 mm l = 5 mm

28 Influence from Singularity Element-averaging Node-averaging Competition method Conclusion Element-averaging shows smallest mesh sensitivity compared to competition and node-averaging method

29 VISUALIZER: Definition Weld Type, Seam Shape, Welded Side Example: T-Joint welded at one side Selection of welding seam E A

30 Contents Introduction to MAGNA and Engineering Center Steyr FEMFAT WELD Features Assessment by Notch Structural Stresses Assessment by Grid Point Forces Assessment by Standards Application Examples & Correlation to Test Results Summary 30

31 Guidelines and Regulations in FEMFAT WELD EUROCODE 3 British Standard 7608 EUROCODE 9 DIN DV 952 DVS 1612 IIW guideline 2004, 2005 FKM guideline

32 FEMFAT WELD Database Information 2 Thickness Blechdickeneinfluss influence (0-100mm) mm Influence Einflussfaktor factor endurance σr/σr,t [-] limit 1,8 1,6 1,4 1,2 1 0,8 0,6 0,4 0,2 0 Dickeneinfluss Influence FEMFAT FEMFAT Dickeneinfluss Influence Eurocode 3 Dickeneinfluss Influence BS BS Blechdicke t Sheet thickness [mm] t [mm]

33 Contents Introduction to MAGNA and Engineering Center Steyr FEMFAT WELD Features Assessment by Notch Structural Stresses Assessment by Grid Point Forces Assessment by Standards Application Examples & Correlation to Test Results Summary 33

34 Verification H-Specimen AUDI H - Specimen Nb-Steel Force Amplitude Fa [N] ,000E+04 1,000E+05 1,000E+06 1,000E+07 1,000E+08 Load Cycles N FEMAFT WELD Calculation Test Results

35 Comparison FLP - Test bench Welding seams of IHV- tubes 29,1

36 Comparison of FEMFAT to Test Results FE-Model LC TEST 2.3 < < 5.0 LC FEMFAT Stress Distribution Damage Distribution

37 Rigid Axle with Bending Load Test setup Critical area T-joint fillet seam Load F Outer diameter D a = 85mm Tube wall thickness = 12mm Bracket wall thickness = 5mm Test load F = 44kN Pulsating load (R=0)

38 Rigid Axle with Bending Load Maximum Principal Stresses (Upper Stress) Small stresses in web plate 450 MPa Normal stress perpendicular to seam dominates

39 Rigid Axle with Bending Load Test results: Damage Crack appeared after 112,100 LC (D=1)

40 Rigid Axle with Bending Load D = 7.3 Crit. area: weld toe (tube) WELD assessment method notch stress Damage Geometry parameters: Seam thickness a = 5.1 mm Seam angle β = 45 Root fusion degree η = 0.0

41 Rigid Axle with Bending Load D = 1.0 Crit. area: weld root WELD assessment method MSZ Damage Geometry parameters: Seam thickness a = 5.1 mm Seam angle β = 45 Root fusion degree η = 0.3

42 Specimen test (SAE Weld Challenge) Test load F = 17.8kN Alternating load (R=-1) Load F

43 Specimen test (SAE Weld Challenge) Failure location Test Result : 75,000 LC with scattering between 20,000 and 200,000 LC

44 Specimen test (SAE Weld Challenge) Max. Principal Normal Stresses (Amplitude Stress) -28 MPa Max. prin. normal stress is oriented parallel to seam

45 Specimen test (SAE Weld Challenge) WELD assessment method notch stress Life (Fillet Weld) Life = 18,000 LC Crit. Area: weld root (web) Geometry parameters: Seam thickness a = 4.76 mm Seam angle β = 45 Root fusion degree η = 0.0

46 Specimen test (SAE Weld Challenge) WELD assessment FEMFAT 4.7 Life (HV seam) Life = 205,000 LC Crit. Area: weld root (web) Geometry parameters: Seam thickness a = 5.6 mm Seam angle β = 45 Root fusion degree η = 1.0

47 Specimen test (SAE Weld Challenge) WELD assessment method MSZ Life Life = 42,000 LC Crit. Area: weld root (web) Geometry parameters: Seam thickness a = 4.76 mm Seam angle β = 45 Root fusion degree η = 0.3

48 Rear Axle Support Test Setup Failure occures in this area during the test

49 Rear Axle Support Weld Modelling Load ratio R=-1 (alternating load) Load level 3kN FEMFAT BASIC Material AlMg3Mn H12 standard database T-Joints: Butt Joints: Lap Joints: HV seam I-seam Fillet seam

50 Rear Axle Support FEMFAT Results Critical point correlates to test results

51 Summary FEMFAT WELD Large basis of internal usage & test verification Technical leadership for assessment methods (stress & force based) Open database concept High analysis speed and flexibility Easy handling: minimum of settings and methods Multitude of CAE-interfaces & HW-platforms Created from engineers for engineers Competent sales and support people Licensing also via Altair HW 9.1 (lease) & MAGNA support

52 Thank you for your attention! Take a look at the full paper in Chinese language