sr 1460 effect of welded properties on aluminum structures progress report 11/25/09

Ship Structure Committee

1

SR 1460Effect of welded properties on Aluminum

StructuresProgress Report

11/25/09

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

703 920 7070 x 275

Dr. Matt ColletteUniversity of Michigan

[email protected](734) 764-8422


2

Agenda

• Objective• Tasks• Schedule• Literature Survey• Failure Criteria• Stress-Strain Curves• Finite Element Models• Results• Future Work


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

Tasks

•Task 1 - Develop Project Plan Based on the SOW•Task2 - Perform literature survey•Task 3 - Develop Matrix of Plate-Stiffener Combinations to be analyzed•Task 4 - Develop Stress-Strain relationship•Task 5 – Develop & Analyze FE Models•Task 6 – Volumetric Yield strength using Dr. Paik’s formula•Task 7 – Analyze results & Recommend changes to existing design standard•Task 8 – Prepare Final report


5

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


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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)


7

Finite Element Models•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


8

Compressive Load • Tabulated results shown in next four slides• Observation

– Modeling entire structure as HAZ is extremely conservative.– In most cases modeling entire structure with Base Metal

properties gives about 10% higher strength than Combined models (Base + HAZ) for conventional model.

– Extruded models have higher strength than conventional models– Variation in strength prediction is large between models for

extruded case


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Results (compressive load)Model1 Model2

FEA Simplified FEAStrain Stress % difference Strain Stress % difference

Combined 0.002000 96.9 - 0.001985 105.0 -base only 0.002000 100.8 4.1% 0.001985 107.1 2.0%HAZ only 0.001667 83.6 -13.7% 0.001533 87.8 -16.4%

Model5 Model6FEA Simplified FEA

Strain Stress % difference Strain Stress % differenceCombined 0.002000 96.9 - 0.001985 106.3 -base only 0.002200 103.6 6.8% 0.002030 108.7 2.3%HAZ only 0.001667 83.5 -13.9% 0.001533 88.1 -17.1%




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Results (cont.)Model2 Model3








11

Results (cont.)Model3 Model4








12

Results (cont.)Model4

FEA SimplifiedStrain Stress % difference Strain Stress % difference


Model8FEA Simplified


Model12FEA Simplified



13

Preliminary ObservationCompressive Load

• Is it possible to model aluminum structure as base metal with reduced proof stress (about 10%)?


14

Preliminary ObservationCompressive Load

• Developed new Stress-Strain curve for AL5083 and AL6082 by reducing proof stress by 10%

• Analyzed models 1 through 8 using this stress-strain curve with no HAZ

• Results with Modified stress-strain curve compared against the combined model (base + HAZ) in next two slides

Ramberg- OsgoodMaterial 5083 6082

0.2% Stress (N/mm^2)= 162 234Young's Modulus (N/mm^2) = 70000 70000n = 16 30


15

Results with Modified Stress-Strain Curve

Ultimate Strength - Model 1

0

20

40

60

80

100

120

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035

Strain (mm/mm)

Str

ess

(Mp

a)

FEA (C)

FEA (B_mod)


0

20

40

60

80

100

120

140

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 0.0040

Strain (mm/mm)

Str

ess

(Mp

a)

FEA (C)

FEA (B_mod)


0

20

40

60

80

100

120

140

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 0.0040

Strain

Str

es

s (

Mp

a)

FEA (C)

FEA (B)_mod


0

20

40

60

80

100

120

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 0.0040

Strain

Str

es

s (

Mp

a)

FEA (C)

FEA (B_mod)


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0

20

40

60

80

100

120

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 0.0040

Strain

Str

ess

9Mp

a)

FEA (C)

FEA (B_mod)


0

20

40

60

80

100

120

140

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 0.0040

Strain

Str

ess

(Mp

a)

FEA (C)

FEA (B_mod)


0

20

40

60

80

100

120

140

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 0.0040

Strain

Str

ess

(Mp

a)

FEA (C)

FEA (B_mod)


0

20

40

60

80

100

120

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 0.0040

Strain

Str

ess

(Mp

a)

FEA (C)

FEA (B_mod)


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Ultimate Strength Comparison Combined properties vs. Reduced base metal properties

80

90

100

110

120

130

140

0 1 2 3 4 5 6 7 8 9

Model #

Ult

imat

e S

tren

gth

(M

pa)

FEA (C) FEA (B_mod_10%)


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• In early stages of design, aluminum structure can be modeled as base metal with reduced proof stress (about 10%). This will avoid time consuming analysis of fine mesh models with small HAZ elements.

• Dr. Paik’s empirical formula compares well with FEA and may also be used in the early stages design.

• In critical areas, structure should be modeled as combination of base metal and HAZ.

Compressive Load (cont)


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Failure Criteria for Tensile & bending Loads

• Tensile and bending loads – what failure criteria?– Compressive loads reach distinct peak – well defined ultimate

strength– Tensile and bending loads – distinct peak may not be present

– When to stop analysis?• Fracture of weld – difficult without solid element or enriched shell-

element model – not practical• Limiting stress • Limiting strain or overall deflection

• Stress is current acceptance criteria by Classification societies and used in this study


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Tensile Load Case

• Run analysis with base, base + HAZ, all HAZ models– 36 models

• Applied displacement range from 10-20mm• Compared the overall tensile force that causes a fixed

portion of the local material’s proof stress to be reached anywhere in the model

• Average stress versus strains are graphed for all 12 models (next 12 slides) along with Yield Point


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Results – Tensile LoadModel Plate Stiffener Weld Location

1 Light (4mm)/ 5083 Light (60x3/30x6)/5083 Plate stiffeners connection

Model 1 - Tensile Load

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

ess

(Mp

a)

FEA(C)

FEA(B)

FEA(HZ)

Yield Point

Model1 Model2Strain Stress % difference

Combined 0.003600 -169.7 -base only 0.003667 -174.0 2.6%HAZ only 0.003333 -139.5 -17.8%


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Results (cont.)Model Plate Stiffener Weld Location

2 Heavy (6mm)/ 5083 Light (60x3/30x6)/5083 Plate stiffeners connection



Model 2 - Tensile Load

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

es

s (

Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Y ield Point


23


3 Heavy (6mm)/ 5083 heavy (100x6/40x10)/5083 Plate stiffeners connection



Model 3 - Tension Load

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

ess

(Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Yield Point


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4 Light (4mm)/ 5083 heavy (100x6/40x10 )/5083 Plate stiffeners connection

Model4Strain Stress % difference


Model 4 - Tensiion Load

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

es

s (

Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Y ield Point


25


5 Light (4mm)/ 5083 Light (60x3/30x6)/6082 Plate stiffeners connection




-250

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

es

s 9

Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Y ield Point


26


6 Heavy (6mm)/ 5083 Light (60x3/30x6)/6082 Plate stiffeners connection




-250

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4

Strain (x 10^-2)

Str

ess

(Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Yield Point


27


7 Heavy (6mm)/ 5083 heavy (100x6/40x10 )/6082 Plate stiffeners connection




-250

-200

-150

-100

-50

00.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

ess

(Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Yield Point


28


8 Light (4mm)/ 5083 heavy (100x6/40x10 )/6082 Plate stiffeners connection




-250

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

ess

(Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Yield Point


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9 Light (4mm)/ 6082 Light (60x3/30x6)/6082 Weld between two extruded


-300

-250

-200

-150

-100

-50

0

0.00 0.10 0.20 0.30 0.40 0.50

Strain (x 10^-2)

Str

es

s (

Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Yield Point




30


10 Heavy (6mm)/ 6082 Light (60x3/30x6)/6082 Weld between two extruded




-300

-250

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

es

s (

Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Yield Point


31


11 Heavy (6mm)/ 6082 heavy (100x6/40x10 )/6082 Weld between two extruded




-300

-250

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

ess

(Mp

a)

FEA (C)

FEA (B)

FEA(HZ)

Yield Point


32


12 Light (4mm)/6082 heavy (100x6/40x10 )/6082 Weld between two extruded




-300

-250

-200

-150

-100

-50

0

0.0 0.1 0.2 0.3 0.4 0.5

Strain (x 10^-2)

Str

ess

(Mp

a)

FEA (C)

FEA (B)

FEA (HZ)

Yield Point


33

Results – Tensile Load

Tensile Load - Yield Point

-300

-250

-200

-150

-100

-50

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13

Model number

Str

ess

(Mp

a)

FEA ( C )

FEA ( B )

FEA ( HZ )


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Results – Tensile Load

Model1 Model2 Model3 Model4Strain Stress % difference Strain Stress % difference Strain Stress % difference Strain Stress % difference

Combined 0.003600 -169.7 - 0.003600 -169.5 - 0.003600 -168.1 - 0.003533 -167.8 -base only 0.003667 -174.0 2.6% 0.003667 -174.0 2.7% 0.003667 -173.7 3.4% 0.003667 -173.6 3.5%HAZ only 0.003333 -139.5 -17.8% 0.003333 -139.5 -17.7% 0.003333 -139.3 -17.1% 0.003333 -139.2 -17.0%






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• Results for Models 1- 8 show small difference between combined and base model (max 6%).

• Modeling with properties of HAZ is very conservative (17%-30%).

• Results for Models 9 – 12 (AL 6082) indicate large differences depending on the model properties.

• In early stages of design, aluminum structure can be modeled as base metal with reduced proof stress (about 10%). This will give slightly conservative results.

Tensile Load (cont)


36

Pressure Load Case

• Run analysis with base, base + HAZ, all HAZ models– 36 models

• Applied Pressure range from 0.1 – 0.2 N/mm^2• Compared overall pressure that causes a fixed portion

of the local material’s proof stress to be reached anywhere in the model


37

Results – Lateral pressure

Yield Point with Lateral Load

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 2 4 6 8 10 12 14

Model #

Lat

eral

Pre

ssu

re (

N/m

m^

2)

FEA(C)

FEA(B)

FEA(HZ)


38

Results – Lateral pressure

% Difference in Yield Point compared to Combined case

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

60%

70%

0 2 4 6 8 10 12 14

Model #

Per

cen

tag

e D

iffe

ren

ce

FEA(B)

FEA(HZ)


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• Results for Models 1- 8 indicate about 10% difference between combined and base model.

• Modeling with properties of HAZ is again very conservative (10%-30%).

• Results for Models 9 – 12 (AL 6082) indicate large differences depending on the model properties.

• In early stages of design, aluminum structure can be modeled as base metal with reduced proof stress (about 10%).

Pressure Load (cont)


40

• Further study to separate impact of material and weld location for 6082.

• Study effect of combined axial and lateral loads.

• Perform experiment under tensile, lateral and combined loads.

Future Work


41

Thank You

sr 1460 effect of welded properties on aluminum structures progress report 11/25/09

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