PSI - Issue 2_A

Zhinan Zhang et al. / Procedia Structural Integrity 2 (2016) 3361–3368 Zhinan Zhang/ Structural Integrity Procedia 00 (2016) 000–000

3368

8

da dN

log( ) log( ) c 

10

total K  

(3)

n

where c=2.17x10 -12 ， n=2.94. With the measured crack growth rates, the stress intensity factor ranges for two test types can be obtained using Eqn. 3. The calculated values are plotted in Fig. 8(a). The Alderliesten model was used to calculate the stress intensity factor range under the prescribed bypass loading in Fig. 7 (Alderliesten (2007)]. The Alderliesten model only provides the stress intensity factor for a small amount of crack growth. Due to the stable crack growth behaviour in FMLs, the stress intensity factor range is extrapolated for larger crack length. In Fig. 8(b), the superposed results of the stress intensity factor range due to bypass loading and the stress intensity factor range for the specimen in type 1 joint correlate well with the results for test type 2. This correlation proves that the superposition method can also be applied to FMLs. The total stress intensity factor resulted from complex loading cases can be decomposed into simpler loading cases whose total stress intensity factor can be derived. 5. Conclusion Two kinds of test for evaluating the pin loading effect in Glare joints have been accomplished. The crack growth phenomena in FMLs with pin loading effects and in company with bypass loading have been observed. Based on this experimental investigation and the analysis of the test results, it can be concluded that:  The effects of pin loading accelerate the crack growth rate in the vicinity of a pin hole and the effects will be weaker as the crack length grows longer.  Loading is not symmetric, so the crack opening should not be symmetric either, leading to non-symmetric delamination shapes. DIC test results and etching results validate this phenomenon.  Total stress intensity factor range of pin and bypass loading specimen is superposed by that of the single pin loading and equivalent far-field loading. The effects of bypass loading and pin loading can be calculated separately in FML joints. References Galatolo R, Lazzeri R., 2016. Experiments and model predictions for fatigue crack propagation in riveted lap-joints with multiple site damage. Fatigue & Fracture of Engineering Materials & Structures 39, 307-19. Hendricks WR., 1991. The Aloha Airlines Accident — A New Era for Aging Aircraft. In: Atluri SN, Sampath SG, Tong P, editors. Structural Integrity of Aging Airplanes: Springer Berlin Heidelberg, pp. 153-65. Chang D, Kotousov A., 2012. A strip yield model for two collinear cracks. Engineering Fracture Mechanics 90. 121-8. Pártl O, Schijve J., 1993. Multiple-site damate in 2024-T3 alloy sheet. International Journal of Fatigue 15, 293-9. Silva LFM, Gonçalves JPM, Oliveira FMF, de Castro PMST, 2000. Multiple-site damage in riveted lap-joints: experimental simulation and finite element prediction. International Journal of Fatigue 22, 319-38. Rodi R, Alderliesten RC, Benedictus R., 2010. Crack-Tip Behavior in Fiber/Metal Laminates by Means of Digital-Image Correlation. Journal of Aircraft 47,1636-46. Rodi R, Alderliesten R, Benedictus R., 2009. An Experimental Approach to Investigate Detailed Failure Mechanisms in Fibre Metal Laminates. In: Bos MJ, editor. ICAF 2009, Bridging the Gap between Theory and Operational Practice: Springer Netherlands, pp. 493-512. Alderliesten RC., 2007. Analytical prediction model for fatigue crack propagation and delamination growth in Glare. International Journal of Fatigue 29, 628-46. Müller RPG., 1995. An experimental and analytical investigation on the fatigue behaviour of fuselage riveted lap joints : the significance of the rivet squeeze force, and a comparison of 2024-T3 and glare 3. Delft University of Technology.