SR 1460: Effect of welded properties on Aluminum Structures



SR 1460: Effect of welded properties on Aluminum Structures

PI Name and Contact: Name: Dr. Pradeep Sensharma

Address1: 2120 Washington Blvd. Address 2: Suite 200 City, State, Zip Code: Arlington, VA 22204.

Email: psensharma@

Telephone: 703 920 7070 x 275

Submitted By: Pradeep Sensharma

Submission Date: 03/27/09

Progress: 1. Performed literature survey as shown below

2. Started developing fine mesh models for FEA

Literature Survey

Research on Aluminum Welds and Weld Effects

Local Studies of Welds

Nelson, F.G., and F.M. Howell. 1952. The Strength and Ductility of Welds in Aluminum Alloy Plate. Welding Journal Research Supplement (September): 397s-402s.  

• Historical paper with studies of butt and fillet welds

• Alloys used follow old naming system – not perfect match to modern alloys

• Indicates concerns about ductility from early days

Scott, M.H., and M.F. Gittos. 1983. Tensile and Toughness Properties of Arc-Welded 5083 and 6082 Aluminum Alloys. Welding Journal Research Supplement, September: 243s-252s.  

• 6082 and 5083 welds tested for strength and ductility with 4043 and 5556 filler metal

• 13mm and 3mm sheet thicknesses studies

• Base, weld, and HAZ metal tested independently, but no sub-division of HAZ.

• Various heat treatments studies

• Elongations as little as 3% recorded for butt-weld specimens in as-welded condition over 125mm (~5in) gauge length.

Matusiak, M., and P. K. Larsen. 1998. Strength and Ductility of Welded Connections in Aluminium Alloys. In Joints in Aluminium - INALCO 98, 299-310. Cambridge.

• Experimental test of butt welds at various angles to applied load and load-bearing fillet welds

• 6082-T6 welded with 5183, 8mm and 20mm plate thickness

• Small tensile specimens machined from Weld and HAZ – show weak region in HAZ some distance off weld corresponding to over-aged zone.

• Tensile deformation also studied – clear reduction in ductility of overall specimens from welds

Zhang, Z. L., J. Odegard, O.R. Mhyr, and H. Fjaer. 2001. From microstructure to deformation and fracture behaviour of aluminium welded joints - a holistic modelling approach. Computational Materials Science 21: 429-435.  

• Linked welding material microstructure simulation with non-linear finite element model

• Allows an entirely model-based approach to estimating weld joint performance

• Initial results were promising based on limited comparison.

Zheng, L., D. Petry, H. Rapp, and T. Wierzbicki. Characterization of material and fracture of AA6061 butt weld. Thin-Walled Structures In Press, Corrected Proof. doi:10.1016/j.tws.2008.08.008. .  

• Simple, easily calibrated material model for 6061-T6 extrusions

• Test specimens with local strain gauges used, simple single-parameter mesh-dependent fracture model fit to data

• F.E. simulations with fracture data showed that method was working.

• Extended in several non-review papers to predict fracture initiation and growth for train structures under crash and impact loading.

Wang, T., O.S. Hopperstad, O.-G. Lademo, and P.K. Larsen. 2007a. Finite element modelling of welded aluminium members subjected to four-point bending. Thin-Walled Structures 45, no. 3 (March): 307-320. doi:10.1016/j.tws.2007.02.009.  

Wang, T., O.S. Hopperstad, O.-G. Lademo, and P.K. Larsen. 2007b. Finite element analysis of welded beam-to-column joints in aluminium alloy EN AW 6082 T6. Finite Elements in Analysis and Design 44, no. 1-2 (December): 1-16. doi:10.1016/j.finel.2007.08.010.  

Wang, T., O.S. Hopperstad, P.K. Larsen, and O.-G. Lademo. 2006. Evaluation of a finite element modelling approach for welded aluminium structures. Computers & Structures 84, no. 29-30 (November): 2016-2032. doi:10.1016/pstruc.2006.08.011.  

Wang, Ting. 2006. Modelling of Welded Thin-Walled Aluminium Structures. PhD, Norwegian University of Science and Technology.  

• Focus on finite element modeling techniques required to capture local weld performance in larger structures.

• Studied 6082-T6 Extrusions and welds, including load-bearing fillet welds, beam-column connections, and welded beam in bending.

• Careful material property studies performed, using mix of new hardness measurements and previous studies to form a finite-element model capable of modeling plastic deformation and ductile fracture of the material

• LS-DYNA simulations, including efforts to use shell elements and shell element refinements to be able to capture strain localization better

Impact of Welds on Tensile Response

Övreas, L, C. Thaulow, and M. Hval. 1992. Effect of Geometry and Size on the Mechanical Properties of AlMgSi1 Weldments. In Proceedings of the 5th International Conference on Aluminum Welding (INALCO), 10.1.1-10.1.8.

&

Hval, M., R.H. Johnsen, and C. Thaulow. 1995. Strength and Deformation Properties of Welded Aluminium Structures With Reference to Local Design and Material Properties. In Proceedings of the 6th International Conference on Aluminum Welding (INALCO), 167-182.

• Experimental and numerical test of offshore structures ranging from simple butt welds to complex beam joints primarily in tensile loading

• 6082 alloy jointed with 5183 filler metal – thick for marine use 16mm, 35mm, 50mm

• All plastic deformation in tension concentrated in narrow HAZ region – overall ductility at failure very low (appears elastic from a global structural perspective)

• Significant implication for plastic design and also comparison between steel and aluminum design codes

• Local weld geometry important to overall response – narrower welds achieved higher constraint and therefore higher strength ~5%. This is mostly true in higher-thickness materials such as those tested here

• Leaving weld bead on butt weld does add strength by modifying local strain distribution in HAZ

• 3-D non-linear FEA did good job matching experiments.

Chan, T.K., and R.F.D. Porter Goff . 2000. Welded aluminium alloy connections: a simplified plastic model. Proc. Instn. Civ. Engrs. Structures and Buildings 140 (May): 161-168.  

• Load-carrying fillet weld plate-and-finger tension connections in 7xxx-series alloys

• Show similar strain localization to 6xxx-series joints

• Built simplified spring-type model for plastic deformation based on idealizing a two-section (over-aged and naturally aged) HAZ.

• Reasonable results based on F.E. comparison and limited experiments.

Impact of Welds on Compression Response

Paik, Jeom Kee, and Alexandre Duran. 2004. Ultimate Strength of Aluminum Plates and Stiffened Panels for Marine Applications. Marine Technology 41, no. 3 (July): 108-121.  

• Finite element study of 5383-H116 plates and stiffened panels

• One set of material properties, HAZ on all plate boundaries and stiffeners. HAZ always assumed at 3t.

• No residual stresses

• Set of regression formulas given in terms of “adjusted” non-dimensional slenderness parameters β’ and λ’

• β’ and λ’ calculated based on volume-averaged yield stress from HAZ and base material zones.

Wang, Xiaozhi, Haihong Sun, Akira Akiyama, and Aiping Du. 2005. Buckling and Ultimate Strength of Aluminum Plates and Stiffened Panels in Marine Structures. In The Fifth International Forum on Aluminum Ships. Tokyo, Japan, October.

• Finite element study of both plates and stiffened panels under compression, HAZ width not varied but strength in HAZ varied

• Modified Faulkner’s classic plate ultimate strength formula to account for HAZ strength reduction. Parameter depends upon plate slenderness and strength ratio between HAZ and base material. Stockier plates or higher strength reductions in HAZ make the reduction factor bigger. This is different from Kristensen, where HAZ reductions are a constant percentage regardless of slenderness.

• Panel formula is incomplete for ultimate strength (see SSC-454), HAZ impact is only accounted for in terms of the plate response, not stiffener, which appears adequate based on FE results

Hopperstad, O. S., M. Langseth, and L. Hanssen. 1997. Ultimate compressive strength of plate elements in aluminium: Correlation of finite element analyses and tests. Thin-Walled Structures 29, no. 1-4: 31-46. doi:10.1016/S0263-8231(97)00013-X.  

• Showed that finite element simulations (ABAQUS) can predict collapse of outstand and internal plates in aluminum alloys, including welds and residual stresses

Kristensen, Odd. 2001. Ultimate Capacity of Aluminium Plates under Multiple Loads, Considering HAZ Properties. PhD, Norwegian University of Science and Technology.  

• Extensive study of aluminum plates under axial, transverse, biaxial, and shear loads via finite element methods

• Used Mofflin PhD material properties for 5083 and 6082 alloys

• Examined the following impacts on ultimate strength

o HAZ softening with and without residual stresses

o Boundary conditions

o Aspect ratios

o Initial deflections

o Material properties

• Regression fits for several design formulas

• Conclusions of work that address the current topics:

o HAZ presence on the loading edges is the most significant for plate strength

o No significant difference in axial plate strength between plates with conventional and extruded welded patterns when loaded edges also have HAZ

o Proposed linear variation in plate strength reduction with HAZ width and an additional linear variation in plate strength reduction with proof stress differences between HAZ and base material

o Clamped boundary conditions make the plate strength less sensitive to HAZ reductions in the axial direction, but more sensitive in the transverse direction

o Stockier plates are more sensitive to initial imperfections than slender plates

o Results support constant percentage reduction in strength for HAZ regardless of slenderness ratio, which differs from Wang et al. paper

Xiao, Yugang, and Craig Menzemer. 2003. Ultimate Compressive Strength of Aluminum Plate Elements. Journal of Structural Engineering 129, no. 11 (November): 1441-1447.

• Comparison of finite element method with experiments, and a series of stub-column simulations.

• Results in line with previous experiments, impact of HAZ not specifically identified.

Mofflin, David. 1983. Plate Buckling in Steel and Aluminium. PhD, Trinity College, University of Cambridge, August.  

• Extensive experimental study of 76 5083 and 6082 plates tested under uni-axial compression with b/t ratios of 20 to 85.

• No welds on short, loaded, edges which may impact the strength predictions significantly

• Include a number of plates with simulated transverse welds which significantly reduced the strength of 6082 plates – 30%

• Longitudinal welds in 5083 plates reduced strength by 10%-15% for stockier plates, and 10%-15% for all 6082 plates.

• 5083 alloy had very loose material specification, not quite comparable to modern 5083-H116/H321

• Indicates that the shape of the stress-strain curve has important impact on buckling, as more-rounded 5083 plates had lower strengths than 6082 plates.

• 5083 alloy tested is likely not as severely impacted by welding as modern 5083 alloys as the strength were generally low (grade had a minimum strength of 125 MPa).

Rigo, P., R. Sarghiuta, S. Estefen, E. Lehmann, S. C. Otelea, I. Pasqualino, B. C. Simonsen, Z. Wan, and T. Yao. 2003. Sensitivity analysis on ultimate strength of aluminium stiffened panels. Marine Structures 16, no. 6 (August): 437-468. doi:10.1016/j.marstruc.2003.09.002.  

&&

Rigo, P., R. Sarghiuta, S. C. Otelea, I. Pasqualino, Z. Wan, T. Yao, C. Toderan, and T. Richir. 2004. Ultimate Strength of Aluminium Stiffened Panels: Sensitivity Analysis. In PRADS 2004. October.

• ISSC study of a 5 stiffener stiffened panel, studied with both a λ=1.8 and λ=0.9. The λ=1.8 was quickly abandoned as the HAZ did not have a large impact as the panel failed at a relatively low stress.

• No HAZ on the transverse frame boundaries?

• Several different FE codes and mesh densities used. All codes generally agreed very well with on another (~5%)

• For shorter panel length, extruded panel type welds had a lower impact than plate/stiffener joint welds (1-6% to 13-17%). A transverse weld in the mid or quarter region also had an impact of roughly 7%-12%

• HAZ width varied through 25mm, 50mm, 75mm, and 100mm. The biggest hit in strength comes from initial HAZ, after this point further reductions in strength diminish as HAZ expands.

• Panels not particularly sensitive to amplitude of initial imperfections

• Residual stresses generally decreased strength, except for extrusion-type welds where a slight increase was seen.

• Initial failure appears to be a plate-type failure, increasing the plate thickness made a large impact on the ultimate strength

• Rigo et. al 2004 re-did some analysis with more typical ½+1+½ bay models and imperfections generated by Eigenmode analysis. They found:

o Model was less stiff, with a significantly lower ultimate strength when modeled with Eigenmode imperfections

o However, strength reductions from welding were also lower for the Eigenmode model. This is not surprising as the failure stress was significantly lower with Eigenmode imperfections.

Impact of Welds on Bending Response

Aluminum Structural Design Standards

Aluminum Association

Hill, H.N., J.W. Clark, and A.M. Brungraber. 1960. Design of Welded Aluminum Structures. Journal of the Structural Division, Proceedings of the ASCE 86, no. ST6 (June): 101-124.

• Original paper used as the basis for much of the Aluminum Association code

• Includes data on HAZ extent and idealized modeling.

• Drew strength data from Nelson and Howell as well as other tests

• Includes formulae for tension, compression, and shear loading for a variety of welds

• Includes some methods for estimating column strength when transverse welds located in mid-region that were not included in AA code

Eurocode 9

ABS HSNC Rules

DNV Rules

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download