sr 1460 effect of welded properties on aluminum structures

Ship Structure Committee

SR 1460Effect of welded properties on Aluminum

Structures

Dr. Pradeep Sensharma & Joey HarringtonBMT Designers & [email protected]

703 920 7070 x 275

Dr. Matt ColletteSAIC

[email protected](301) 352-4728


Agenda

• Introduction

• Objective

• Background

• Tasks

• Schedule


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


• 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

Background


• Reduction can be up to 50% of the strength of base material

Background (cont.)

PROOF STRESS (MPA)

ULTIMATE STRESS (MPA)

ALLOY

BASE WELDED BASE WELDED

5083-H116 214 165 303 276

5383-H321 220 165 305 290

6061-T6 (<3/8”) 241 138 290 165

Ref: ONR report on Aluminum Structure Reliability Program (ASRP), 2006


• 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

Background (cont.)


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


Tasks (cont.)

• Task 3 - Develop Matrix of Plate-Stiffener Combinations to be analyzed

Model Plate Stiffener Weld Location1 Light (4mm)/ 5083 Light (60x3/30x6)/5083 Plate stiffeners connection2 Heavy (6mm)/ 5083 Light (60x3/30x6)/5083 Plate stiffeners connection3 Heavy (6mm)/ 5083 heavy (100x6/40x10)/5083 Plate stiffeners connection4 Light (4mm)/ 5083 heavy (100x6/40x10 )/5083 Plate stiffeners connection5 Light (4mm)/ 5083 Light (60x3/30x6)/6082 Plate stiffeners connection6 Heavy (6mm)/ 5083 Light (60x3/30x6)/6082 Plate stiffeners connection7 Heavy (6mm)/ 5083 heavy (100x6/40x10 )/6082 Plate stiffeners connection8 Light (4mm)/ 5083 heavy (100x6/40x10 )/6082 Plate stiffeners connection9 Light (4mm)/ 6082 Light (60x3/30x6)/6082 Weld between two extruded

10 Heavy (6mm)/ 6082 Light (60x3/30x6)/6082 Weld between two extruded 11 Heavy (6mm)/ 6082 heavy (100x6/40x10 )/6082 Weld between two extruded 12 Light (4mm)/6082 heavy (100x6/40x10 )/6082 Weld between two extruded


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


Task4 (cont.)0.2% Proof Stress

Alloy Ten. Comp.

Elastic Modulus

Elongation at failure

Ramberg Osgood Exponent

Calculated Tensile Failure Stress

Code Tensile Failure Stress

-- MPa MPa MPa % -- MPa MPa 5083-H116

215 180 70000 12 12 302 305

6082-T6 260 260 70000 8 30 294 290-310 Mild Steel 235 235 208000 20-30 Infinite --

Ref: ONR report on Aluminum Structure Reliability Program (ASRP), 2006


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


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


Tasks (cont.)

• Task 5 – Develop & Analyze FE Models–Develop models for all the combinations of plate/stiffener/material discussed before– Model initial distortion by applying lateral pressure

Ref: Rigo et al.


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– Compare results


• Task 6 – Volumetric Yield strength & ULSAP calculations– Perform volumetric yield strength calculations using

Dr. Paik’s close form solution

– Develop fine mesh models of some stiffener-plate combinations using MAESTRO (?)

– Perform limit state calculations using ULSAP (?)

Tasks (cont.)


Task 6 (cont.)

– Check influence of HAZ, residual stress & initial distortion on Ultimate strength of a sample aluminum ship using ALPS/HULL(?)


• Task 7 – Analyze results & Recommend changes to existing design standard

• Task 8 – Prepare Final report

Tasks (cont.)


ScheduleTasks & Deliverable Expected Completion Date

Develop a work plan February 05, 2009(Deliverable 1)

Literature Survey March 31, 2009

Review of Current Design Standards April 30, 2009

Quarterly Progress Report/Review 1 May 15, 2009(Deliverable 2)

Model and Analyze FE Models November 15, 2009

Quarterly Progress Report/Review 2 (with interim results)

August 07, 2009(Deliverable 3)

Quarterly Progress Report/Review 3 (With Final FEA Results)

November 30, 2009(Deliverable 4)

Develop recommendations for changes in design standard

December 15, 2009

Draft Final Report January 05, 2010(Deliverable 5)

Final report that includes all activities and previous deliverables of this project including case studies.

February 05, 2010(Deliverable 6)


Schedule (cont.)

ID Task Name

1 Effect of Welded Properties on Aluminum Structure2 Kick - off Meeting3 Literature Survey4 Quarterly Progress Review 15 Review of Current Design Standards6 FE Modeling and Analysis7 Quarterly Progress Review 2 (Interim Results)8 Quarterly Progress Review 3 (Final FEA Results)9 Develop recommendations for Changes10 Draft Final Report11 Final Report12 Project Conclusion

2/5

5/15

8/7

11/30

2/5

February March April May June July August September October November December January February March


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


Progress (Cont.)

• Selected panel geometries

Model Plate Stiffener Weld Location1 Light (4mm)/ 5083 Light (60x3/30x6)/5083 Plate stiffeners connection2 Heavy (6mm)/ 5083 Light (60x3/30x6)/5083 Plate stiffeners connection3 Heavy (6mm)/ 5083 heavy (100x6/40x10)/5083 Plate stiffeners connection4 Light (4mm)/ 5083 heavy (100x6/40x10 )/5083 Plate stiffeners connection5 Light (4mm)/ 5083 Light (60x3/30x6)/6082 Plate stiffeners connection6 Heavy (6mm)/ 5083 Light (60x3/30x6)/6082 Plate stiffeners connection7 Heavy (6mm)/ 5083 heavy (100x6/40x10 )/6082 Plate stiffeners connection8 Light (4mm)/ 5083 heavy (100x6/40x10 )/6082 Plate stiffeners connection9 Light (4mm)/ 6082 Light (60x3/30x6)/6082 Weld between two extruded

10 Heavy (6mm)/ 6082 Light (60x3/30x6)/6082 Weld between two extruded 11 Heavy (6mm)/ 6082 heavy (100x6/40x10 )/6082 Weld between two extruded 12 Light (4mm)/6082 heavy (100x6/40x10 )/6082 Weld between two extruded


Progress (Cont.)

• Stiffener Spacing: 225mm

• Plate Slenderness ratios:

5083_4 2.852

6082_4 3.428

5083_6 1.902

6082_6 2.285


Progress (Cont.)

• Stiffener Length: 1000 mm

• Column Slenderness ratios:

5083_4_L 0.658

5083_6_L 0.723

6082_4_L 0.791

6082_6_L 0.869

Light Stiffener Heavy Stiffener

5083_4_H 0.36

5083_6_H 0.37

6082_4_H 0.432

6082_6_H 0.445


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.


Progress (cont.)

• Started developing FE models


Thank You

Any Questions?

sr 1460 effect of welded properties on aluminum structures

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