Newly revealed features of fracture toughness behavior of spot welded dual phase steel sheets for automotive bodies

Ibrahim Sevim

doi:10.3139/120.110798

Article

Newly revealed features of fracture toughness behavior of spot welded dual phase steel sheets for automotive bodies

Ibrahim Sevim

Published/Copyright: November 18, 2015

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From the journal Materials Testing Volume 57 Issue 11-12

Abstract

Fracture toughness is one of the parameters, which are used to estimate the fatigue life of resistance spot-welded (RSW) joints. A spot-welded pair is affected by the shear stress of the weld zone when it is exposed to tensile load. Repetitive loads reduce the fatigue life of the spot weld, and the material splits at the spot-welded region. This study investigates the effect of welding current, weld time and nucleus size ratios on the fracture toughness of RSW of galvanized DP450 steels having 1.0 mm thickness. The specimens were joined by spot welding at different welding currents and times. Welding processes were carried out using 3, 5, 7 and 9 kA welding current and 10, 20, 30 and 40 cycles (1 cycle = 0.02 s) weld time and the electrode pressure was fixed at 600 MPa. All series of specimens were exposed to tensile shear test in order to determine the fracture toughness. The fracture toughnesses for all series of RSW joints were calculated by using the formula given in the literature. The nugget diameters, core sizes and their heights were measured via an optical microscope. The Vickers microhardness measurement was carried out on the weld nugget, heat affected zone (HAZ) and base metal. Nucleus size ratios were calculated. The results of the study demonstrated that the fracture toughness of RSW depended not only on the nugget diameter D, but also sheet thickness t, tensile rupture force F, hardness H and nucleus size ratios h_n/d_n.

Kurzfassung

Die Bruchzähigkeit ist einer der Parameter, die verwendet werden, um die Lebensdauer von widerstandspunktgeschweißten Verbindungen (Resistance Spot Welds (RSW)) abzuschätzen. Ein punktgeschweißtes Blechpaar wird durch die Scherspannung in der geschweißten Zone beeinflusst, wenn es einer Zugbeanspruchung unterworfen wird. Wiederholte Beanspruchungen reduzieren die Ermüdungslebensdauer der Punktschweißung und der Werkstoff spaltet sich im Bereich der Punktschweißung. In der diesem Beitrag zugrunde liegenden Studie wurde der Effekt der Schweißstromstärke, der Schweißdauer und der Verhältnisse der Keimgrößen auf die Bruchzähigkeit von Widerstandspunktschweißungen von galvanisierten DP 450 Stählen bei verschiedenen Schweißstromstärken und Zeiten untersucht. Die Proben wurden hierzu bei verschiedenen Stromstärken und Zeiten geschweißt. Die Schweißprozesse wurden mit Stromstärken von 3, 5, 7 und 9 kA und 10, 20, 30 und 40 Zyklen (1 Zyklus = 0,02 s) ausgeführt, wobei der Elektrodendruck mit 600 MPa konstant war. Sämtliche Probeserien wurden dem Zugscherversuch unterworfen, um die Bruchzähigkeit zu bestimmen. Die Bruchzähigkeit wurde mit der Gleichung aus der Literatur berechent. Die Linsendurchmesser, die Kerngrößen und die Höhen wurden mittels eines Lichtmikroskops gemessen. Die Mikro-Vickershärte wurde in der Schweißlinse der Wärmeeinflusszone (Heat Affected Zone (HAZ)) und dem Grundwerkstoff analysiert. Die Ergebnisse der Studie zeigen, dass die Bruchzähigkeit der Widerstandspunktschweißungen nicht nur vom Linsendurchmesser D, sondern auch von der Blechdicke t, der Zugkraft F, der Härte H und der Kerngrößenverhältnisse h_n/d_n abhängen.

§Correspondence Address, Associate Prof. Dr. İbrahim Sevim, Department of Mechanical Engineering, Faculty of Engineering, Mersin University, 33343 Yenişehir-Mersin, Turkey. E-mail: ibrahimsevim33@gmail.com

Dr. Ibrahim Sevim is Associate Professor in the Department of Mechanical Engineering, Engineering Faculty, Mersin University, Turkey. He obtained his PhD degree from the Department of Mechanical Engineering of Istanbul Technical University, Turkey, in 1998. His research areas include failure analysis, welding, modeling and designing applications.

References

1 F.Ozturk, S.Toros, S.Kilic: Tensile and spring-back behavior of DP600 advanced high strength steel at warm temperatures, J. Iron Steel Res. Int.16 (2009), pp. 41–4610.1016/S1006-706X(10)60025-8Search in Google Scholar

2 C.Ma, D. L.Chen, S. D.Bhole, G.Boudreau, A.Lee, E.Biro: Microstructure and fracture characteristics of spot-welded DP600 steel, Mater. Sci. Eng. A485 (2008), pp. 334–34610.1016/j.msea.2007.08.010Search in Google Scholar

3 L.Xinsheng, W.Xiaodong, G.Zhenghongz, W.Min, W.Yixiong, RYounghua: Microstructures in a resistance spot welded high strength dual phase steel, Mater. Char.61 (2010), pp. 341–34610.1016/j.matchar.2009.12.018Search in Google Scholar

4 M.Kleiner, S.Chatti, A.Klaus: Metal forming techniques for lightweight construction,J. Mater. Proc. Technol.177 (2006), pp. 2–710.1016/j.jmatprotec.2006.04.085Search in Google Scholar

5 X. Q.Zhang, G. L.Chen, Y. S.Zhang: Characteristics of electrode wear in resistance spot welding dual-phase steels, Mater. Des.29 (2008), pp. 279–28310.1016/j.matdes.2006.10.025Search in Google Scholar

6 F.Hayat, B.Demir, S.Aslanlar, M.Acarer: Effect of welding time and current on the mehanical properties of resistance spot welded IF (DIN EN 10130-11999) steel, Kov. Mat.47 (2009), pp.11–17Search in Google Scholar

7 F.Hayat, B.Demir, M.Acarer: Tensile shear stress and microstructure of low-carbon dual phase Mn-Ni steels after spot resistance welding, M. Sci. Heat Treat.49 (2007), pp. 484–48910.1007/s11041-007-0090-xSearch in Google Scholar

8 A.Bak, S.Gunduz: Effect of strain ageing on the mechanical properties of interstitial free steels under as-received, heat treated and spot welded conditions for automotive applications, Proc. of the Institution of Mechanical Engineers Part D-J. Automob. Eng.209 (2009), pp. 785–79110.1243/09544070JAUTO1176Search in Google Scholar

9 M.Erdogan: The effect of new ferrite content on tensile fracture behaviour of dual-phase steels, J. Mat. Sci.37 (2002), pp. 3623–363010.1023/A:1016548922555Search in Google Scholar

10 M. K.Kulekci, F.Mendi, I.Sevim, O.Basturk: Fracture toughness of friction stir welded joints of AlCu4SiMg aluminium alloy, Metalurgija44 (2005), pp. 209–213Search in Google Scholar

11 I.Sevim: Fracture toughness of spot-welded steel joints, Kov. Mat.43 (2005), pp. 113–123Search in Google Scholar

12 I.Sevim: Effect of hardness on fracture toughness for spot-welded steel sheets, Mater. Des.27 (2006), pp. 21–3010.1016/j.matdes.2004.09.008Search in Google Scholar

13 L. P.Pook: Fracture mechanics analysis of the fatigue behavior of spot welds, Int. J. Fract.11 (1975), pp. 173–17610.1007/BF00034726Search in Google Scholar

14 P. C.Paris, G. C.Sih: Fracture toughness testing and its application, ASTM STP381 (1965), p. 30Search in Google Scholar

15 G. C.Sih: Handbook of Stress Intensity Factors, Lehigh University, Bethlehem, Pennsylvania, USA (1973)Search in Google Scholar

16 D.Radaj, S.Zhang: Stress intensity factors for spot welds between plates of dissimilar materials, Engineering Fracture Mechanics42 (1992), pp. 407–42610.1016/0013-7944(92)90163-9Search in Google Scholar

17 D.Zhang: Stress intensities at spot welds, Int. J. Fract.88 (1997), pp. 167–18510.1023/A:1007461430066Search in Google Scholar

18 D.Zhang: Stress intensities derived from stresses around a spot weld, Int. J. Fract.99 (1999), pp. 239–25710.1023/A:1018608615567Search in Google Scholar

19 B.Wilson, T. E.Fine: Fatigue behavior of spot-welded high strength steel joints, SAE Technical Paper No. 810354 (1981) 10.4271/810354Search in Google Scholar

20 N.Pan, S. D.Sheppard: Stress intensity factors in spot welds, Eng. Fract. Mech.70 (2003), pp. 671–68410.1016/S0013-7944(02)00076-0Search in Google Scholar

21 S. M.Darwish, M. S.Soliman, A. M.Al-Fahead: Manufacturing and characteristics of brass damping sheets, J. Mater. Process. Technol.79 (1998), pp. 66–7110.1016/S0924-0136(97)00322-1Search in Google Scholar

22 B.Chang, S. Y.Yaowu, L.Lu: Studies on the stress distribution and fatigue behavior of weld-bonded lap shear joints, J. Mater. Process. Technol.108 (2001), pp. 307–31310.1016/S0924-0136(00)00842-6Search in Google Scholar

23 R. S.Chandel, S.Garber: Mechanical and metallurgical aspects of spot-welded joints, Met. Technol.1 (1974), pp. 418–42410.1179/030716974803287645Search in Google Scholar

24 S. M.Zuniga, S. D.Sheppard: Determining the constitutive properties of the heat-affected zone in a resistance spot weld, Modeling Simul. Mater. Sci. Eng. A.3 (1995), pp. 391–41610.1088/0965-0393/3/3/007Search in Google Scholar

25 H.Tao, P. D.Zavattieri, L. G.Jr.Hector, W.Tong: Mode I fracture at spot welds in dual-phase steel: An application of reverse digital image correlation, Experimental Mechanics50 (2010), pp. 1199–121210.1007/s11340-009-9323-9Search in Google Scholar

26 M.Marya, X. Q.Gayden: Development of requirements for resistance spot welding dual-phase (DP600) steels: Part 1 – The causes of interfacial fracture, Welding Research11 (2005), pp.172–182Search in Google Scholar

27 V. H. BaltazarHernandez, M. L.Kuntz, M. I.Khan, Y.Zhou: Influence of microstructure and weld size on the mechanical behaviour of dissimilar AHSS resistance spot welds, Sci. Tech. Weld. Join.13 (2008), pp. 769–77610.1179/136217108X325470Search in Google Scholar

28 F.Hayat, I.Sevim: The effect of welding parameters on fracture toughness of resistance spot-welded galvanized DP600 automotive steel sheets, Int. J. Adv. Manuf. Technol.58 (2012), pp. 1043–105010.1007/s00170-011-3428-xSearch in Google Scholar

29 S.Aslanlar: The effect of nucleus size on mechanical properties in electrical resistance spot welding of sheets used in automotive industry, Mater. Des.27 (2006), pp. 125–13110.1016/j.matdes.2004.09.025Search in Google Scholar

30 B.Kocabekir, R.Kaçar, S.Gündüz, F.Hayat: An effect of heat input, weld atmosphere and weld cooling conditions on the resistance spot weldability of 316L austenitic stainless steel, J. Mater. Process Technol.195 (2008), pp. 327–335, 10.1016/j.jmatprotec.2007.05.026Search in Google Scholar

31 M.Vural, A.Akkus, B.Eryurek: Effect of welding nugget diameter on the fatigue strength of the resistance spot welded joints of different steel sheets, J. Mater. Process Technololgy176 (2006), pp. 127–13210.1016/j.jmatprotec.2006.02.026Search in Google Scholar

32 M. I.Khan, M. L.Kuntz, E.Biro, Y.Zhou: Microstructure and mechanical properties of resistance spot welded advanced high strength steels, Mater. Tran.49 (2008), pp. 1629–163710.2320/matertrans.MRA2008031Search in Google Scholar

Published Online: 2015-11-18

Published in Print: 2015-11-16

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https://doi.org/10.3139/120.110798