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SR 1460 Effect of welded properties on Aluminum Structures

SR 1460 Effect of welded properties on Aluminum Structures. Dr. Pradeep Sensharma & Joey Harrington BMT Designers & Planners psensharma@dandp.com 703 920 7070 x 275 Dr. Matt Collette SAIC MATTHEW.D.COLLETTE@saic.com (301) 352-4728. Agenda. Introduction Objective Background Tasks

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SR 1460 Effect of welded properties on Aluminum Structures

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  1. SR 1460Effect of welded properties on Aluminum Structures Dr. Pradeep Sensharma & Joey Harrington BMT Designers & Planners psensharma@dandp.com 703 920 7070 x 275 Dr. Matt Collette SAIC MATTHEW.D.COLLETTE@saic.com (301) 352-4728

  2. Agenda • Introduction • Objective • Background • Tasks • Schedule • Progress

  3. Objective The goal of this project is to provide a basis for design of aluminum structures that will minimize the penalty on scantling selection Study all possible methods of modeling aluminum stiffened plate structure Provide basis for modification to existing design standard

  4. Background • The 5xxx-series (5083) and 6xxx-series(6082) aluminum alloys are extensively used for marine structures • 5xxx-series alloys are used in deck and hull plating whereas 6xxx-series alloys are used as structural reinforcements, bulkheads, and stiffeners that do not come in direct contact with seawater. • These Aluminum alloys suffer reduction in strength in the Heat Affected Zone (HAZ) of welds

  5. Background (cont.) • Reduction can be up to 50% of the strength of base material Ref: Paik et al. Ref: ONR report on Aluminum Structure Reliability Program (ASRP), 2006

  6. Background (cont.) • The traditional approach to design has been using the minimum strength of the HAZ as the design strength • This approach may seriously underestimate the strength of welded structure • Imposes a significant weight penalty on the final design

  7. Tasks Task 1 - Develop Project Plan Based on the SOW Task2 - Perform literature survey Review previous technical studies which address the impact of welds on the strength of aluminum structures Review current aluminum design standards from the marine and civil engineering communities

  8. Tasks (cont.) Task 3 - Develop Matrix of Plate-Stiffener Combinations to be analyzed

  9. Task3 (cont.) Welded Stiffeners Extruded panels Ref: Rigo et al.

  10. Tasks (cont.) Task 4 - Develop Stress-Strain relationship Develop stress-strain data for base metal and HAZ Use Ramberg-Osgood relationship or use existing data

  11. Task4 (cont.) Ref: ONR report on Aluminum Structure Reliability Program (ASRP), 2006

  12. Task 4 (cont.) Existing Stress-strain data (Rigo et al.)

  13. Tasks (cont.) Task 5 – Develop & Analyze FE Models Develop FE models using FEMAP Use plate elements only Model HAZ (3*thick.) for Plate & Stiffeners (4 or 5) Welds will not be modeled Model 3 bays or ½ + 1 + ½ bays

  14. Task 5 (cont.) Develop models for all the combinations of plate/stiffener/material discussed before Model using Material properties of Only base metal Only HAZ Base metal and HAZ Model initial distortion by applying lateral pressure Residual stress will not be modeled in this study Ref: Rigo et al.

  15. Task 5 (cont.) Use non-linear stress strain relationship Analyze model for three load cases Compression Tension Bending Perform Non-linear FEA and check for Failure using load deflection curve fro compressive loading Use max strain/max displacement for other two cases Compare results

  16. Tasks (cont.) • Task 6 – Volumetric Yield strength & ULSAP calculations • Perform volumetric yield strength calculations using Dr. Paik’s close form solution • Develop fine mesh models of same stiffener-plate combinations using MAESTRO (?) • Perform limit state calculations using ULSAP (?)

  17. Task 6 (cont.) • Check influence of HAZ, residual stress & initial distortion on Ultimate strength of a sample aluminum ship using ALPS/HULL(?)

  18. Tasks (cont.) • Task 7 – Analyze results & Recommend changes to existing design standard • Task 8 – Prepare Final report

  19. Schedule

  20. Schedule (cont.)

  21. Progress • Developed panel geometries for FEA • Paik’s Panel test data (SSC-451) Plate Slenderness ratio: 2.2 – 3.2 Column Slenderness ratio: 0.4 – 1.5

  22. Progress (Cont.) • Selected panel geometries

  23. Progress (Cont.) • Stiffener Spacing: 225mm • Plate Slenderness ratios:

  24. Progress (Cont.) • Stiffener Length: 1000 mm • Column Slenderness ratios: Heavy Stiffener Light Stiffener

  25. Progress (cont.) • Literature Survey In-Process • Experimental material properties • Base and HAZ measurements (6) • Previous design studies • Experimental and numeric compression collapse (8) • Plates and beam under lateral loads (5) • Detailed weld studies (3) • Standards • Eurocode 9, Aluminum Association, ABS.

  26. Progress (cont.) • Started developing FE models

  27. Thank You Any Questions?

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