Crack Closure Behavior at Fatigue Crack Growth Under Negative Stress Ratio

2017 ◽  
Vol 2017 (0) ◽  
pp. OS0508
Author(s):  
Yoshihito YAMAGUCHI ◽  
Kunio Hasegawa ◽  
Yinsheng Li
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Stress Ratio

Effect of Stress Ratio on Fatigue Crack Growth in 95Pb-5Sn Solder

1999 ◽  
Vol 123 (3) ◽  
pp. 311-315 ◽  
Author(s):  
J. Zhao and ◽  
Y. Mutoh ◽  
T. Ogawa
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Stress Ratio ◽  
High Stress ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Threshold Region ◽  
Test Conditions

The stress ratio effect on the fatigue crack growth behavior of 95Pb-5Sn solder has been investigated. It is found that both ΔJ and ΔK can correlate fatigue crack growth data well, which means that the crack growth behavior of the 95Pb-5Sn solder under the frequency of 10 Hz was dominantly cyclic dependent. The da/dN-ΔJ relationship can be expressed as: da/dN=1.1×10−11s˙ΔJ1.45. Low level of crack closure was found only in the near-threshold region. Except in this region, no crack closure was observed in the present test conditions. Both transgranular and intergranular fractures were observed on fracture surfaces: the former was dominant in most test conditions and the latter was dominant at the high stress ratio of 0.7. Striations and striation-like features were also found. Many slip bands and cavities along the grain boundary were observed on the crack wake and ahead of the crack tip in the high crack growth rate region.

Fatigue Crack Growth Rate in Laser-Welded Web Core Sandwich Panels - Fatigue Crack Propagation in Welded Base Metal

2014 ◽  
Vol 891-892 ◽  
pp. 1212-1216
Author(s):  
Anghel Cernescu ◽  
Heikki Remes ◽  
Pauli Lehto ◽  
Jani Romanoff
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Closure ◽  
Fatigue Crack Growth Rate ◽  
Stress Ratio ◽  
Closure Effect

The all-metal web-core sandwich structure consists of two face plates stiffened by one-directional system of web plates. These web core sandwich structures are used in many structural applications such as ship hulls, offshore platforms, bridge decks, and industrial platforms. However, the stress variation caused by the service loadings can be a determinant factor for crack initiation and growth until early failure of the entire structure. This paper presents an experimental study on fatigue crack growth rate in base material from a face plate after rolling and welding. The study is focused on the analysis of the stress ratio and crack closure effect on the fatigue crack growth rate in two directions. There is a significant stress ratio effect on fatigue crack growth rate, much more pronounced in the case of crack propagation in the longitudinal direction than in the transverse propagation. For all tests, the crack closure effect is more pronounced at low stress intensity factor range (in the threshold domain).

Fatigue Crack Growth for Ferritic Steel Under Negative Stress Ratio

2018 ◽  
Author(s):  
Yoshihito Yamaguchi ◽  
Kunio Hasegawa ◽  
Yinsheng Li
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Applied Stress ◽  
Crack Closure ◽  
Stress Ratio ◽  
Stress Intensity Factor Range

Crack closure during fatigue crack growth is an important phenomenon for predicting fatigue crack growth amount. Many experimental data show that fatigue cracks close at not only negative loads but also positive loads during constant amplitude loading cycles, depending on applied stress levels. The Appendix A-4300 in the ASME Code Section XI provides two equations of fatigue crack growth rates expressed by stress intensity factor range for ferritic steels under negative stress ratio. The boundary of two fatigue crack growth rates is classified by the magnitude of applied stress intensity factor range with the consideration of crack closure. The objective of this paper is to investigate the influence of the magnitude of the stress intensity factor range on crack closure. Fatigue tests have been performed on ferritic steel specimens in air environment at room and high temperatures. Crack closures were obtained as a parameter of stress ratio. It was found that crack closure occurs at a smaller applied stress intensity factor range than the definition given by the Appendix A-4300.

Fatigue Crack Growth Behavior of FSWed Joint Joined with a Bobbin Type Tool in Different Aluminum Alloys

2013 ◽  
Vol 446-447 ◽  
pp. 32-39 ◽  
Author(s):  
Panya Buahombura ◽  
Yukio Miyashita ◽  
Yuichi Otsuka ◽  
Yoshiharu Mutoh ◽  
Seo Nobushiro
Keyword(s):  
Fatigue Crack ◽  
Aluminum Alloys ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Stress Ratio ◽  
Crack Growth Behavior ◽  
Threshold Region ◽  
Friction Stir ◽  
Base Materials

Fatigue crack growth (FCG) behavior at weld nugget zone (WNZ) and heat affected zone (HAZ) in friction stir welded (FSWed) joints joined by using a bobbin type tool in 5052, 6N01 and 7N01 aluminum alloys were investigated comparing to the base materials (BM). Constant stress amplitude fatigue crack growth tests were conducted with stress ratio of 0.1. Crack closure behavior was investigated simultaneously during fatigue test with unloading elastic compliance method. The results in this study showed that in near threshold region, FCG resistance in WNZ of FSWed 5052 and 6N01 joints was lower than that in the BM and the HAZ. In contrast, FCG resistance in WNZ of FSWed 7N01 joint was higher than that in the BM and the HAZ. At high ΔK region, WNZ of FSWed 5052 joint had the similar FCG resistance with the BM and the HAZ. However, WNZ of FSWed 6N01 joint showed lower FCG resistance compared to the BM and the HAZ. FCG resistance in WNZ of FSWed 7N01 joint was the similar with that in the HAZ but was lower than that in the BM. Crack closure behavior was observed in BM and HAZ for all materials tested. In WNZ, crack closure was found in FSWed 7N01 joint but was not found in FSWed 5052 and 6N01 joints. Difference in FCG behavior at different weld region was mainly due to difference in crack closure behavior in FSWed 5052 and 6N01 joints. However, in case of FSWed 7N01 joint, it is considered that effect of microstructure was significant on FCG behavior even at high ΔK region.

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