Department of Aeronautical & Vehicle Engineering ...KTH+Lightweight+Structur… · KTH –Royal Institute of Technology Department of Aeronautical & Vehicle Engineering Lightweight

KTH – Royal Institute of Technology

Department of Aeronautical & Vehicle EngineeringLightweight Structures Group

Design & Fabrication of Welded Structures

Contact: Zuheir Barsoum ([email protected])(phone: +46-70 230 43 42))

Research Group

Zuheir Barsoum Jack Samuelsson(Emeritus)

Mansoor Khurshid

Faculty

Researchers / PhD students

Ayjwat A. BhattiThomas Stenberg

Other / Industry: Davood Afshari, Bertil Jonsson (Volvo CE), Gert Pettersson (Titanx)

Affiliated faculty: Imad Barsoum (Petroleum Institute, UAE), Gary Marquis (Aalto University, Finland)

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Research Group

Current research topics

Mansoor Khurshid

• Multiaxial fatigue of welded structures

• Constitutive modeling of ductile failure of HSS welds

Ayjwat A. Bhatti

• Development of FEM welding simulation framework for large complex welded structures

• Development of FEM framework for simulation of weld improvement techniques

Thomas Holmstrand

• Development of algorithms and procedures for weld quality assessment and inspection

• Applied fracture mechanics and defect tolerance criteria

• Effect of cutting procceses on the fatigue life of HSS

Bertil Jonsson

• Development of weld quality system and implementation in production

Davood Afshari

• Mechanical properties of resistance spot welded thin sheet aluminum alloys for automotive applications

Gert Petterson

• Non-linear effects in finite element modeling of welded structures and fabrication

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Research Projects

Ongoing research projects

OnWeld, 2013-2016 (Vinnova)•KTH, Swerea Kimab, Volvo CE, ABB, Väderstad-verken, ESAB, GKN Aerospace•investigate and verify the potential for new laser scanning technologies and algorithms as modern tools forautomated weld quality assurance

KUIRF, 2014-2016 (Abu Dhabi Gov. UAE)•KTH, KUSTAR•Characterization of All-Aluminum Sandwich Panels for Aerospace & Civil Applications. Development ofcorrugated sandwich panels with friction stirs welding and ultrasonic welding as joining technique. Studymanufacturing aspects, structural durability, dynamic and static properties, environmental studies and LCC.

InnoDefab, 2014-2016 (Vinnova SIO)•KTH, KIMAB, CTH, HIAB, SSAB, Outokumpu, Voestalpine, NCC, WSP, Lecor, Trafikverket, ELU•Innovative concepts for lightweight design and fabrication of welded high strength steel structures. Studyingthe potential of fatigue life improvement techniques and corrugated sandwich steel structures for differentindustrial sectors.

Competitive Bridges, 2015-2017 (FORMAS/Trafikverket)•KTH, CTH, ELU•Fatigue life enhancement through post weld treatment. Application of HFMI techniques to composite steelbridges; testing, measurements and FE analysis

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Teaching Programs

Advanced design of welded structures, 6hp

� Fatigue design methods:– Nominal stress

– Hot-spot stress

– Effective notch stress

– LEFM

� Notches, defects and residual stresses

� Spectrum fatigue

� Improvement methods

� Multi-axial fatigue

� FE modelling

� Weld quality systems

� Design codes

� FEA exercises

Also given to industry, example: Caterpilar, Volvo CE, Consulting firms, among manyothers… more than 300 engineers have taken this course.

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International activities and awards

Activities (selected)

• Arranging the Swedish conference on design &fabrication of welded structures, biyearly.

• Experts/ Swedish delegates in International Instituteof Welding (IIW).

• Chairman within IIW in Commission XIII

Awards (selected)

• IIW Granjon Prize award 2010 for outstanding research results• Kjellberg medal for significant international contribution in welding research• Best paper award; 2013 ASME PVP Conference• Japan-Sweden Scholarship 2014

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Selection of ongoing research projects

Computational Weld Mechanics –

towards a simplified and effective approach for large welded structures

A.A. Bhatti, Z. Barsoum

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Development of an efficient welding simulation approach

Welding residual stresses and distortions are inherited from welding process and both have significanteffect on the structural integrity and fatigue performance of a structure/component. Experimentalmethods are expensive and sometimes not feasible. Finite element (FE) simulations are regarded asgood alternative and can be used for assessment of residual stresses and distortions in welded structure.But the highly nonlinear and transient nature of the welding process makes the FE simulationcomputationally intensive; and a large and complex welded structure would make it even more complexand time expensive.

Therefore in this research work an alternative and simplified welding simulation approach is developed,called rapid dumping. The developed approach was implemented on different small scale welded jointse.g. butt joint, tube-flange joint, T-fillet joints etc.

Stresses extracted at

the center of joint

480mm

10mm240mm

Comparison of experimental and predicted longitudinal residual stresses in butt weld using different simulation approaches.15

Back View

Weld Start

45mm

25mm

The rapid dumping approach has also been implemented on the large welded structure (bogie beam)structure in order to validate the approach for large welded structures. Furthermore, the bogie beamstructure is also analyzed with other available approaches in literature in order to devise an efficientFE simulation framework for prediction of residual stresses in large welded structures.

Bogie beam in anarticulated hauler

Sketch of bogie beam structure

Comparison of experimental and predictedradial and hoop stress using rapid dumping at90o from the weld start on back side of theplate.


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Comparison of experimental and FE measured residual stresses usingdifferent approaches along four different paths B1-B4.

The results in this research work showthat by using rapid dumping approach thecomputational time can be reducedsignificantly when compared to otherapproaches with a preserved accuracy ofthe estimated welding residual stresses.Moreover, this approach is applicable tosmall as well as large welded structures


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Thermo-mechanical properties play an important role in the accurate assessment of welding residualstresses and distortions. It is always preferred to employ experimentally measured temperature dependentmaterial properties in the welding simulations. But due to budget, time and equipment constraints thematerial properties are either extracted from literature or evaluated from simulation software. This studyinvestigates the influence of thermo-mechanical properties of different steel grades on weldingresidual stresses and distortions. The final outcome of this study will help in identifying which thermo-mechanical properties are the most influential and necessary for welding simulations.

Different thermal and mechanical cases aresimulated in which thermo-mechanicalmaterial properties of S355, S700 and S960steel grades are considered as constant,linear and as a function of temperature.

6mm

50mm

300mm

6mm

Welding

direction

Transverse stress

measurment

130mm *Angular distortion

measurementUX=UY=UZ=0

Influence of thermo-mechanical material properties on welding residual stresses and distortions

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Temperature histories at point A andB using test cases (Thermal1-5) forT-fillet joint welded with S355 steelgrade.

Comparison of angular deformationpredicted by different mechanicaltest cases in T-fillet joint welded withdifferent steel grades.


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This study has shown that the temperature dependent yield stress is the most important

material property in the mechanical analysis. Therefore, in order to develop generalizedsemi-empirical expressions for temperature dependent yield stress; piece-wise linearequations are used to describe it which are applicable to a wide range of steel grades.

1 1

1 2 2 1 1 2

2 1

2 3 3 2 2 3

3 2

3 3

( )

1( ) ( ) ( )

( )

1( ) ( ) ( )

( )

( )

RT RT f

f f f f f

f f

f f f f f

f f

f f MT

T T T T T

T T T T T T T TT T

T T T T T T T TT T

T T T T

σ σ β

σ σ β

σ σ β

σ σ

= + ≤ ≤ = − + − ≤ ≤ − = − + − ≤ ≤ −

= ≤ ≤

It is important to mention that theseequations are based on the experimentaldata (of temperature dependent yieldstress) available in literature as well as thetesting carried out within this study.

Comparison of experimentally measured and approximated yield stress for different steel grades.


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Development of Weld Quality Control and Assessment Techniques for Welded Structures

T. Stenberg, Z. Barsoum

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Background

Quality assessment and Control

Welded structures within the vehicle and transportation industry application are primarilysubjected to load time histories that give cause to fatigue failure. Since welds in highstrength steels are notch sensitive owing to their variable local geometry, sharp transitionsand flaws, these quantities will determine the fatigue strength of the welded structure.

Due to the lack of objective and accurate weld quality assurance methods in production,designers are prevented to utilize high strength steels in many design applications, whichmakes many steel structures 20-40% heavier than what is possible.

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Research objectivesDevelop accurate algorithms and implement these into an on-line measuring system, which willenable on-line monitoring of the produced weld quality. The prime objectives of this researchwork includes:

• Development of algorithms for subjective assessment of weld geometry and imperfections

• Identify quality affecting process parametersand enable improved process control

• Reduce overproduction, rework and scrapping

• Identify possibilities to enable adaptive process control of welding technologies.


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Project visualization map

Processr, u, a, etc.

On-line measuring

Future:Selected weld qualityis used as input.Full scan along thewelded / brazed joint.

Today:Received weld quality is attempted to be measuredon the final product.Few selected positions only.

Improved and early QA & control is needed


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Effect of cutting processes on the fatigue life of HSS

T. Stenberg, Z. Barsoum

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Content

• Investigate how different cut edges affect the fatigue life of different steel grades:

• Cutting methods: Laser, Plasma, Gas and Waterjet

• Steel grades: S355, S700 and S960

• Thicknesses: 16 mm, 25mm and 40 mm

Approach• Measure the cut surface, Rz, FEM and LEFM, Fatigue test


Multiaxial Fatigue Design of Welded Structures

M. Khurshid, Z. Barsoum

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Multiaxial Fatigue Design of Welded Structures

Research Objectives

To make the existing structures lightweight, energy, and cost efficient. The accurate estimation ofboth ductile and fatigue strength of the welded joints is an important assure. The prime objectivesof this research work includes:

• Development of finite element procedure to handle multi-axial fatigue of welded joints.

• Assessment of the existing stress and fracture mechanics based design principles for multi-axialfatigue.

• Investigation of multi-axial fatigue caused in welds by complex geometries and loading.

In-phase loading Out of phase loading

Investigated tubular joints-exposed to complex loading

Notch stress at weld root 29

Fatigue strength evaluation of welds-proportional stressstate

Manufactured specimens

70 degree CA testing

• Fatigue life of butt weld with different seam

angles evaluated

• Weld is subjected to tensile loading

experiences proportional multi-axial stress

state in the root

• Fatigue life estimated with reasonable

accuracy

Shear stress weld plane

Normal stress weld plane

Weld seam angle

No

rmali

zed

Str

ess [

MP

a]

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Fatigue strength evaluation of welds - non proportionalstress state

Torsion testing under internal pressureModelled specimen for notch stress analysis

Internal pressure and torsion-In phase

• Fatigue life of fillet weld in tube to plate

joint evaluated

• Weld is subjected to internal pressure and

torsion (in and out of phase loading)

• Both in and out of phase loading

introduces non-proportional stress state

• Fatigue life estimated with reasonable

accuracy

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Constitutive Modeling of Ductile Failure in High Strength Steel Welds

M. Khurshid, Z. Barsoum

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Research Objectives

Knowledge of the ductile behavior of a mechanical structure is vital to ensure safety of itsoperators. Individual mechanical behavior of the materials and geometry of the joint affects theoverall ultimate strength and deformation capacities of a weld. The aim of this study is:

• Development of a guideline for constitutive modeling of ductile failure in HSS welds.

• Study of the effect of combinations of different strength of filler and base materials on theultimate strength of the joint.

• Comparison of different ductile damage criteria.

Constitutive Modeling of Ductile Failure in High StrengthSteel Welds

Load displacement curve Ductile failure safety situation

Ductile damage plotPartially penetrated weld

Ductile damage plot fully penetrated weld

Base platefailure

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• The lack of development in strength of

filler materials lead to undermatching in

welds in steels of yield strength >700MPa

• The static strength is Influenced by filler

material strength and weld metal

penetration

• Design rules in standards are valid for

joints in steels of yield strength up to

700MPaHSS and filler development

Designed-Fully penetrated butt weld

Designed-Partially penetrated butt weld

Etched weld section for FEmodeling and hardnessmeasurements

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S960 undermatching-Fully penetrated S960 undermatching-Partially penetrated

S960 FEA, testing, and standardcomparison-partially penetrated

• Static strength of joints with

undermatching filler is affected more by

weld metal penetration

• Standards are conservative and FEA and

testing are in good agreement

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IIW Recommendations on HFMI – guidelines under development

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Selection of Publications

Journal Papers (selected, last years)

• More than 50 journal publication the last 10 years• More than 50 conference publication the last 10 years

Barsoum Z. and Samuelsson J., “Fatigue assessment of cruciform joints welded with different methods”, Steel Research International, No. 12, pp. 882-888, 2006.Barsoum Z., “Residual stress prediction and relaxation in welded tubular joints under constant cyclic loading”, Materials Science Forum, Vols. 524-525, pp. 323-328,

Trans Tech Publications, 2006.Barsoum Z., “Residual Stress Prediction and Relaxation in Welded Tubular Joint”, IIW-1773-06, Welding in the World, Vol. 51 Issue 1/2 January/February, 2007.Barsoum Z., “Residual Stress Analysis and Fatigue of Multi-pass Welded Tubular Structures”, Engineering Failure Analysis, Vol. 15, Issue 7, pp. 863-874, 2008.Barsoum Z. and Jonsson B., “Fatigue assessment and LEFM analysis of cruciform joints fabricated with different welding processes“, IIW-2175-07, Welding in the World,

Vol. 52, No. 7/8, pp. 93-105, 2008.Samuelsson J., Jonsson B. and Barsoum Z., “Service fatigue design of complex welded construction equipment”, Materials Science and Engineering Technology, Vol

39, Issue 10, pp. 734-739, 2008. (*)Barsoum Z. and Barsoum I., “Residual stress effects on fatigue life of welded structures using LEFM”, Engineering Failure Analysis, Volume 16, Issue 1, pp. 449-467,

January 2009. (*)Barsoum Z. and Gustafsson M., “Fatigue of high strength steel joints welded with low transformation consumables”, Engineering Failure Analysis, Vol. 16, pp. 2186-

2194, 2009. (*)Barsoum Z. and Lundbäck A., “Simplified FE welding simulation of fillet welds – 3D effects on the formation of residual stresses”, Engineering Failure Analysis, Vol. 16,

pp. 2281-2289, 2009. (*)Jonsson, B., Barsoum Z., Arezou, G.B, “Influence from weld position on fillet weld quality”, Welding in the World 53 (Special issue), pp. 137-142, 2009.Alam, M.M., Barsoum, Z., Jonsén, P., Häggblad, H. A., Kaplan, A., “The Influence of Surface Geometry and Topography on the Fatigue Cracking Behaviour of Laser

Hybrid Welded Eccentric Fillet Joints”, Journal of Applied Surface Science, 256, pp.1936-1945, 2010. Hatami M K and Barsoum Z, “Fatigue assessment of cruciform joints welded in different positions”, Journal of Metallurgy & Material Science, Vol. 52, No.1, pp.87-102,

2010.Barsoum Z. and Jonsson B., “Influence of weld quality on the fatigue strength in seam welds”, Engineering Failure Analysis, No. 18, pp. 971-979, 2011. (*)M.M. Alam, Z. Barsoum, P. Jonsén, A.F.H. Kaplan, H.Å. Häggblad, “Influence of defects on fatigue crack propagation in laser hybrid welded eccentric fillet joint”,

Engineering Fracture Mechanics, No 78, pp. 2246-2258, 2011.Barsoum Z., “Fatigue design of welded structures – some aspects of weld quality and residual stresses”, Welding in the World, No. 11/12, Vol. 55, 2011. (*)Jonsson B., Barsoum Z. and Sperle J.-O., “Weight optimization and fatigue design of a welded bogie beam structure in a construction equipment”, Engineering Failure

Analysis, Vol. 19, pp. 63-76, 2012. (*)Bhatti A. A., Barsoum Z., “Classification and crack growth modeling of cold lap defects in MAG welding”, Journal of Materials Science and Technology, Vol. 19, No. 2,

pp. 91-105, 2011.Khushid M., Barsoum Z., Mumtaz N.A., “Ultimate strength and failure modes for fillet welds in high strength steels”, Journal of Materials and Design, Vol 40, pp.36-42,

2012. (*)Barsoum Z., Khurshid M., Barsoum I., “Fatigue strength evaluation of friction stir welded aluminium joints using the nominal and notch stress concepts”, Journal of

Materials and Design, Vol 41, pp. 231-238, 2012. (*)Afshari D., Sedighi M., Barsoum Z., Peng R. L., “An approach in prediction of the failure load in Resistance Spot Welded Aluminum 6061-T6 under quasi-static tensile

test”, IMechE, Part B: Journal of Engineering Manufacture, Vol. 226, 6: pp. 1026-1032, 2012. (*) 37

Selection of Publications

Journal Papers (selected, last years)

Stenberg T., Lindgren E., Barsoum Z., “Development of algorithm for quality inspection of welded structures”, IMechE, Part B: Journal of Engineering Manufacture, Vol. 226, 6: pp. 1033-1041, 2012. (*)

Barsoum Z., Samuelsson J., Jonsson B., Björkblad A., “Fatigue design of lightweight welded vehicle structures - Influence of material and production procedures”, IMechE, Part B: Journal of Engineering Manufacture, Vol. 226, 10, pp.1736-1744, 2012. (*)

Pettersson G., Barsoum Z., “Finite element analysis and fatigue design of a welded construction machinery component using different approaches”, Engineering Failure Analysis, Vol. 26, pp. 274-84, 2012. (*)

Bhatti A. A., Barsoum Z., “Development of efficient 3D welding simulation approach for residual stress estimation in different welded joints”, Journal of Strain Analysis, Volume 47, Issue 8, pp. 539-552, 2012. (*)

Yildirim H., Marquis G. and Barsoum Z., Fatigue assessment of High Frequency Mechanical Impact (HFMI) Improved fillet welds by local approaches, International Journal of Fatigue, Vol. 52, pp. 57–67, 2013. (*)

Alam M.M., Kaplan A. F. H., Tuominen J., Vuoristo P., Miettinen J., Poutala J., Näkki J. Junkala J., Peltola T., Barsoum Z., ” Variety of stress raisers for laser clad bars”, Journal of Materials and Design, Vol 46, pp. 328-337, 2013.

Afshari D., Sedighi M., Barsoum Z., “Residual stress measurement in resistance spot welded aluminium alloy joints”, Journal of Mechanical Engineering, Vol. 2, No. 4, pp. 6-9, 2012.

Marquis G., E. Mikkola, H. Yildirim and Barsoum Z., “Fatigue Strength Improvement of Steel Structures by HFMI: Proposed Fatigue Assessment Guidelines”, Welding in the World, No. 57, pp. 803-822, 2013. (*)

Marquis G. and Barsoum Z., “Fatigue Strength Improvement of Steel Structures by HFMI: Proposed Procedures and Quality Assurance Guidelines”, Welding in the World, No. 58, pp. 19-28, 2014. (*)

Afshari D., Sedighi M. Karimi M. R. and Barsoum Z., “On Residual Stresses in Resistance Spot Welded Aluminum alloy 6061-T6: Experimental and Numerical Analysis”, Journal of Materials Engineering and Performance, Vol. 22, No 12, pp. 3613-19, 2013.

Bhatti A. A, Barsoum Z, Mee van der V, Kromm A., Kannengiesser T, "Fatigue strength improvement of welded structures using new low transformation temperature filler materials", Procedia Engineering, Vol. 66C, pp.192-201, 2013.

Marquis G., Barsoum Z., “A Guideline for Fatigue Strength Improvement of High Strength Steel Welded Structures Using High Frequency Mechanical Impact Treatment”, Procedia Engineering, Volume 66, pages 98-107, 2013.

I. Barsoum., F. Khan and Z. Barsoum, “Optimization of the torsional strength of an induction hardened splined shaft”, Materials and Design, Vol. 54, pp. 130–136, 2014. (*)

M. Farajian, Z. Barsoum and A. Kroom, “Residual stress engineering in fatigue resistant welds”, Materials Science Forum Vols. 768-769, pp 613-619, 2014.Bhatti A. A., Barsoum Z., Khurshid M., ” Development of FE simulation framework for prediction of residual stresses in large welded structures”, Computers & Structures,

Volume 133, pp. 1-11, March 2014. (*)Aygül M., Al-Emrani M., Barsoum Z. and Leander J., “Investigation of distortion-induced fatigue cracked welded details using 3D crack propagation analysis”,

International Journal of Fatigue, No. 65, pp. 54-66, 2014.M. Khurshid, Z. Barsoum and G. Marquis, “Behavior of Compressive Residual Stresses in High Strength Steel Welds Induced by High Frequency Mechanical Impact

Treatment”, ASME Journal of Pressure Vessel Technology, pp. 1-8, Vol. 136, August 2014.T. Holmstrand, N. Mrdjanov, Z. Barsoum, E. Åstrand, ” Fatigue life assessment of improved joints welded with alternative welding techniques”, Engineering Failure

Analysis, pp. 10-21, Volume 42, July 2014.

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Department of Aeronautical & Vehicle Engineering ...KTH+Lightweight+Structur… · KTH –Royal Institute of Technology Department of Aeronautical & Vehicle Engineering Lightweight