Abstract
This study provides an optimal shape of square nut for better projection welding performance. Both experimental design method and electrical-thermal-mechanical finite element analysis (FEA) are used to investigate the effects of nut shape parameters on the height decrease of nut leg, called setdown. The relationship between the setdown and weld strength is then analyzed. Also, welding time to reach 50% of setdown tset is introduced as another objective function for better welding performance. The optimal nut shape parameters are determined to maximize the setdown, and minimize the tset at the same time via Taguchi method. The difference of setdown values between experiments and FEA is within 12%, which verify the reliability of the FE model. The gap between DIN928 standard for nut leg geometry and the optimized nut leg shape is less than 0.2 mm. The differences of setdown and tset values for two nut shapes are 6% and 9%, respectively.
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References
Lasson JK, Bengtsson L (2007) The overlooked joining technology of fasteners for modern car body structure-latest experience from nut and bolt attachment to advanced high strength steels, 11th European Automotive Engineers’ Council (EAEC), Budapest, Hungary
Adams JV, Matthews GN, Begeman ML (1965) Effect of projection geometry upon weld quality and strength. Welding Journal 44:466–470
Cunningham AJR, Begeman ML (1996) Effect of projection height upon weld quality and strength. Welding Journal 45:26–30
Sun X (2001) Effect of projection height on projection collapse and nugget formation − a finite element study. Welding Journal 80:211–216
Harris JF, Riley JJ (1961) Projection welding low carbon steel using embossed projects. Welding Journal 40:363–376
Lee H, Kim N, Lee TS (2005) Overload failure curve and fatigue behavior of spot-welded specimens. Engineering Fracture Mechanics 72:1203–1221
Tolf E, Hedegård J (2007) Resistance nut welding: improving the weldability and joint properties of ultra-high strength steels. Welding in the World 51:28–36
Ringsberg JW, Orvegren P, Henrysson HF, Åkerström G (2008) Sheet metal fatigue near nuts welded to thin sheet structures. International Journal of Fatigue 30:877–887
Linden MJ (2010) Optimization of weld nut geometry by simulation, Master Thesis, KTH Royal Institute of Technology, Stockholm, Sweden
Nielsen CV, Zhang W, Martins PAF, Bay N (2014) Numerical and experimental analysis of resistance projection welding of square nuts to sheets. Procedia Engineering 81:2141–2146
Abaqus Version 6.14 User’s manual, 2013, Dassault Systems Simulia Corp., Providence, RI, USA
Peace GS (1992) Taguchi methods: a hands-on approach. Addison-Wesley, Reading, MA
Nielsen CV, Zhang W, Martins PAF, Bay N (2015) 3D numerical simulation of projection welding of square nuts to sheets. Journal of Materials Processing Technology 215:171–180
Tsai CL, Dai WL, Dickinson DW, Papritan JC (1991) Analysis and development of real-time control methodology in resistance spot welding. Welding Journal 70:339–351
Resistance Welder Manufacturers’ Association (2003) Resistance welding manual. RWMA, Philadelphia
Park YW, Son CS (2013) Weldability evaluation and process optimization of nut projection welding, Conference Proceedings of The Korean Society of Manufacturing Technology Engineers, p 262
Ha S, Murugan SP, Marimuthu KP, Park Y, Lee H (2019) Estimation of lobe curve with material strength in resistance projection welding. Journal of Materials Processing Technology 263:101–111
Zhang H, Senkara J (2011) Resistance welding : fundamentals and applications. CRC press
Lee SY (2016) A study on improvement of nut shape for quality improvement in ultra high strength steel nut projection welding, Master Thesis, Pukyong University
Anon, DIN928-square weld nuts, 2013, Deutsches Institut Fur Normung (German National Standard)
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Funding
This work was supported by the Sogang University research fund (No. 201919049.01) and the Carbon Industrial Cluster Development Program (No. 10083609) funded by the Ministry of Trade, Industry, & Energy (MOTIE, Korea).
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Giyeol Han: conceptualization, methodology, finite element analysis, writing—review and editing
Sangun Ha: experiments, data curation
Karuppasamy Pandian Marimuthu: investigation
Siva Prasad Murugan: experiments
Yeongdo Park: project administration
Hyungyil Lee: supervision
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Appendices
Appendix 1. Welding conditions for Taguchi method
FE analyses are performed by modeling square nut in accordance with the DIN928 standard [20]. The pressing force f = 5 kN is applied as per the standard. A robust weld strength can be ensured only when the nugget is sufficiently formed on both the nut and steel sheet. Each experiment requires cross-sectional cutting of the nut-steel contact area to explore the nugget formation. This process is constrained by time and cost limitations. To address this problem, we perform several FE analyses to evaluate the depth of fusion into sheet under different current intensity (Fig. 14). At low electrode current densities, i.e., I = 5 and 7 kA, the nugget was formed only on the surface of the sheet, failing to penetrate the sheet, reducing the weld strength. This analysis is consistent with the results of most studies on nut projection welding with I = 10 kA or higher. Therefore, FE analyses are performed with a fixed current of I = 10 kA in this study.
Appendix 2. Effect of noise factor on S and t set
Tables 11 and 12 show FEA results of S and tset, respectively, for various conditions according to Table 1. Zero values of tset for run #1 in Table 11 indicate that the projection collapse by pressing force exceeds 50% without current flow. To analyze the effect of noise factor, level average analyses are performed by following the equation as shown in Table 13. The level average value \( {\overline{u}}_i \) is calculated as follows
where \( {\overline{z}}_j \) is the mean value of either tset or S for each jth noise factor combination. i means the level of each noise factor and n is the total number of simulations for each level. The zero value of delta for each noise factor demonstrates negligible effect of noise factors E, F, and G on S and tset. This is because heat losses due to convection and conduction can be ignored since nut projection welding is performed within few milliseconds of the welding process, which is identical to that of resistance welding.
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Han, G., Ha, S., Marimuthu, K.P. et al. Shape optimization of square weld nut in projection welding. Int J Adv Manuf Technol 113, 1915–1928 (2021). https://doi.org/10.1007/s00170-021-06771-7
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DOI: https://doi.org/10.1007/s00170-021-06771-7