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Fatigue analysis for a multi-lap spot welded joint of high strength steel using quasi static tensile-shear test

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Abstract

The welding quality of spot weldment is an important factor that significantly affects the strength, stiffness, safety, and other performance characteristics of vehicles. Therefore, quality control and fatigue life evaluation of spot weldment are necessary processes. This paper presents a method for determining the fatigue life of multi-lap spot weldment of a high strength steel sheet. In this method, the fatigue life is estimated using the lethargy coefficient, which is the total defect coefficient according to rupture stress and time obtained by the quasi static tensile-shear test. The DC potential drop method was used to check initiation and propagation of cracks in addition to the test. Also, in this study, we modified the lethargy coefficient by using the welding current. Furthermore, we define a specific lapping constant, which is a characteristic constant of 2 or 3 lap weldments. The fatigue life obtained by the fatigue estimate equation, which contains a specific lapping constant was compared and verified with an experimental value. Finally we analyzed the relation of lap number, welding current and fatigue life. This method can save processing time and cost for predicting the life cycle of a structure.

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Abbreviations

f :

frequency, (Hz)

F :

failure energy, (kJ/mole)

k :

boltzmann constant, (kJ/mole)

t :

time, (sec)

N :

fatigue life, (sec)

t 0 :

fatigue life coefficient, (sec)

t r :

rupture time, (sec)

T :

absolute temperature, (K)

U 0 :

bonding energy, (kJ/mole)

γ :

lethargy coefficient, (kJ/mole·mm2/N)

σ r :

rupture stress, (MPa)

σ a :

alternating stress, (MPa)

σ m :

mean stress, (MPa)

β :

probability of existence 95% limit region of Stress distribution coefficient

References

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Authors and Affiliations

  1. Department of Mechanical & Aerospace Engineering, The Research Center of Industrial Technology, Chonbuk National University, Jeonbuk, 561-756, Korea

    S. R. Sin, S. M. Yang, H. S. Yu, C. W. Kim & H. Y. Kang

Authors
  1. S. R. Sin
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  2. S. M. Yang
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  3. H. S. Yu
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  4. C. W. Kim
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  5. H. Y. Kang
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Correspondence to S. M. Yang.

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Sin, S.R., Yang, S.M., Yu, H.S. et al. Fatigue analysis for a multi-lap spot welded joint of high strength steel using quasi static tensile-shear test. Int.J Automot. Technol. 9, 81–86 (2008). https://doi.org/10.1007/s12239-008-0010-0

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  • DOI: https://doi.org/10.1007/s12239-008-0010-0

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