PSI - Issue 14

L. Chikmath et al. / Procedia Structural Integrity 14 (2019) 922–929 Chikmath/ Structural Integrity Procedia 00 (2018) 000–000

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Fig 8: Material model of Lug joint in analysis

Fig 9: Variation of Hoop stress with and with cold working

3.2 Fatigue analysis The configuration is subjected to fatigue loading with different levels of maximum load in the fatigue cycle. Fastener hole is cold worked to 0.4% of hole radius and an interference fit is introduced which is 0.2% of hole radius for further analysis. The maximum hoop stress are compared for pure interference (0.2% Ri) and cold worked hole in Fig.10. At zero load, both exhibit initial residual stresses. With the increase in Pin load, the stresses vary marginally (linear) up to certain level of load. Further increase in Pin load causes the stresses to vary non-linearly. This is due to the separation of pin from the hole periphery and this is effectively analysed by adopting inverse formulation described in section 2.2. The effect of mean stress due to pure interference fit pin is brought down significantly by cold working process (point M). Also for specific load case, cold worked joint has lower alternating stresses in the local stress cycle as shown in Fig.10. Thus both smaller mean and local stresses would lead to higher fatigue life of the cold worked joint.

Fig 10: Variation of local stresses in the lug joint with and without cold working