Comparison of Crack Growth Models and Crack Closure Effect

Abstract:

According to standard test method for fatigue crack growth rates of metallic materials, the crack growth rate of 30NCD16 at three stress ratio (R=0.1, 0.3 and 0.5) were measured. Based on linear elasticity fracture mechanics theory, the fatigue crack growth rate was studied through the nonlinear least squares fitting method. The Paris model parameters at steady growth region and near threshold growth region and NASGRO model parameters were obtained. The effective stress intensity factors versus curves at three stress ratios were determined by crack closure effect. The results show that the Paris equation can preferably describe relations at steady growth region. At this region the model parameter m lies 2.5-4. This result is consistent with the known statistical facts of most metallic materials. NASGRO equation can preferably describe relations from near threshold growth region to high values region. all the test data at three stress ratio was able to correlate and . Crack closure was the major factor in correlating stress ratio and crack growth rate, the degree of crack closure weaken with increasing stress ratio.

• Periodical: Advanced Materials Research (Volumes 311-313)
• Pages: 822-825
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.311-313.822
• Online since: August 2011
• Authors: Wen Lin Liu, Ri Jie Yang, Zhi Tao Mu, Shu Yan Liu, Da Zhao Yu
• Keywords: Crack Closure, Crack Growth Rate, Effective Stress Intensity Factor, Stress Ratio

References

[1] Cairu Gao, Xianghua Liu, Lin-xiu Du, Kunning Jia. Journal of Northeastern University (Natural Science), Vol.29 No.11 (2008), p.1568~1571 (In Chinese)

[2] Lili Chang, Chunlei Liu. Journal of Taiyuan University of Science and Technology. Vol.29 No.1 (2008), p.56~59 (In Chinese)

[3] Jong-Ho Kim, Soon-Bok Leeb, Seong-Gu Hong. Fatigue crack growth behavior of Al7050-T7451 attachment lugs under flight spectrum variation. Theoretical and Applied Fracture Mechanics 40 (2003) 135~144

DOI: 10.1016/s0167-8442(03)00041-7

[4] Robert E. Vaughan and Jung Hua Chang. Life Predictions for High Cycle Dynamic Components Using Damage Tolerance and Small Threshold Cracks. Presented at the American Helicopter Society 59th Annual Forum, Phoenix, Arizona (2003)

DOI: 10.4050/jahs.49.493

[5] Lan Huang, Benyin Zeng, Pan C J. The Forman Crack Propagation Speed Curve of Four Parameters Fitting Technique. Helicopter Technology, Vol. 3 (2003), p.9 (In Chinese)

[6] Zhitao Mu, Wenlin Liu, Ping Jin. The Crack Growth Life Predictions for High Cycle Dynamic Components. 5th International Conference on Fracture and Damage Mechanics. Haerbin, China, September 13 to 15, (2006)

[7] Scott C. Forth. An Evaluation of the Applicability of Damage Tolerance to Dynamic Systems. Presented at the 8th Joint NASA/FAA/DOD Aging Aircraft Conference Palm Springs, California, USA, January 31 through February 3, (2005)

[8] Chuanfu Ding, Hui Yu, Xueren Wu. Journal of Aeronautical Materials, Vol.20 No.1 (2000), p.14~17 (In Chinese)

[9] R. Jones, L. Molent. Critical Review of the Generalised Frost-Dugdale Approach to Crack Growth in F/A-18 Hornet Structural Materials. DSTO-RR-0350(2010)