scholarly journals Numerical modeling and simulation of fatigue crack growth rate due to cyclic loading on doubler structure fuselage skin station number 360-380 stringer 6L-7L Boeing 737-900 extended range aircraft

2021 ◽  
Vol 13 (2) ◽  
Author(s):  
Lado Rislya Prakasa ◽  
Djarot Wahju Santoso
Keyword(s):  
Growth Rate ◽  
Numerical Modeling ◽  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Extended Range ◽  
Numerical Modeling And Simulation ◽  
Fuselage Skin

Fatigue Crack Growth Rate of Reeled Pipe in Sour Environments

2015 ◽  
Author(s):  
Javad Safari ◽  
Ramgopal Thodla ◽  
Ian Merchant ◽  
John Hamilton
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Paris Law ◽  
Number Of Cycles ◽  
Corrosive Environments

Fatigue Crack Growth Rate (FCGR) of reeled pipe (strained & aged) in sour environments was investigated. FCGR frequency scans on different microstructures, i.e. heat affected zone (HAZ), and weld center line (WCL), revealed that, FCGR in corrosive environments increased with decreasing frequency and reached a plateau value at low frequencies of 10mHz to 3mHz. At these ‘plateau frequencies’, FCGR in the moderately sour environment that was investigated were found to be about 10–18× or 30× higher than the in-air values for the WCL and HAZ, respectively. There was no effect of the reeling cycles on the FCGR of the WCL or HAZ specimens. The FCGRs of the WCL were consistently lower than that of the HAZ by about a factor of 2–3× under various conditions. The reason for the lower FCGR of the WCL is not well understood. It is possible that it may be due to the higher yield strength (YS) of the overmatched welds, differing hydrogen concentration and/or diffusion coefficient or possibly due to the differences in the microstructure between the HAZ and WCL. Paris law curves, FCGRs as a function of ΔK (stress intensity factor range), were measured on the HAZ, and WCL (both intrados) at the plateau frequency (10mHz), representative of flowline cyclic loading. They were also measured at a higher frequency of 0.33Hz, representative of Steel Catenary Risers (SCR) cyclic loading associated with wave motion. Comparisons of measured Paris law curves in corrosive environments to those in air were consistent with the results of the frequency scans. There was no effect of number of cycles of reeling on the Paris law curves in the sour environment tested for WCL and HAZ specimens at both the plateau frequency and 0.33Hz. The results of the test program suggest FCGR of WCL and HAZ in the sour environment tested are not affected by number of cycles (up to 5) of straining on the intrados side for the strain level (1.93% per cycle) used in this study.

Reliability Evaluation of Fatigue Crack Growth Rate of Heat-Treated TIG-Welded Al 6013-t4 by Two-Parameter Weibull

2020 ◽  
Vol 867 ◽  
pp. 75-81
Author(s):  
I Made Wicaksana Ekaputra ◽  
Gunawan Dwi Haryadi ◽  
Stefan Mardikus ◽  
I Gusti Ketut Puja ◽  
Rando Tungga Dewa
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Reliability Evaluation ◽  
Heat Treated ◽  
Fuselage Skin ◽  
Two Parameter

The limited data of fatigue crack growth (FCG) may cause an inaccuracy assessment of the fatigue crack growth rate (FCGR). For particular parts in aircraft such as fuselage skin, a high-reliability degree due to FCG must be determined accurately for the design and safety requirements. Generally, the 6xxx series of aluminum alloy is used as the material for the fuselage skin in the aircraft. In this study, reliability evaluation of FCGR of heat-treated TIG-welded Al 6013-t4 was investigated by two-parameter Weibull. The FCG tests were conducted by following the ASTM E647 under three different artificial aging time conditions of 6, 18, and 24 hours. The C and m constant values were obtained by drawing the regression line from FCG data following Paris’s equation and analyzed employing three methods; the least square fitting method (LSFM), a mean value method (MVM), and a probabilistic distribution method (PDM). The result showed that the PDM and MVM showed a better-fitted line to assess the C and m values than LSFM. From the reliability viewpoints, the two-parameter Weibull was proposed to be applied as the PDM. Furthermore, the MCM was successful in evaluating the probabilistic assessment of the FCGR with the 85% confidence interval.

scholarly journals Fatigue Crack Growth Under General-Yielding Cyclic-Loading

1986 ◽  
Vol 108 (3) ◽  
pp. 201-205 ◽  
Author(s):  
Zheng Minzhong ◽  
H. W. Liu
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
The Finite Element Method ◽  
General Yielding

In low cycle fatigue, cracks are initiated and propagated under general-yielding cyclic-loading. For general-yielding cyclic-loading, Dowling and Begley have shown that fatigue crack growth rate correlates well with the measured ΔJ. The correlation of da/dN with ΔJ has also been studied by a number of other investigators. However, none of these studies has correlated da/dN with ΔJ calculated specifically for the test specimens. Solomon measured fatigue crack growth in specimens in general-yielding cyclic-loading. The crack tip fields for Solomon’s specimens are calculated, using the finite element method, and the J-values of Solomon’s tests are evaluated. The measured crack growth rate in Solomon’s specimens correlates very well with the calculated ΔJ.

Evaluation of Crack Growth of Ni-Base Alloys Under Long Term Cyclic Loading in BWR Environment

2015 ◽  
Author(s):  
Masao Itatani ◽  
Takuya Ogawa
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Weld Metal ◽  
Crack Growth ◽  
Base Metal ◽  
Test Data

Crack growth test data of Ni-base alloys under cyclic loading in simulated boiling water reactor (BWR) environment including the effects of load rising time (tr) were evaluated in the view points of both fatigue and stress corrosion cracking (SCC). When the test data were plotted in the relationship between da/dt and Kmax, da/dt monotonically decreased with increasing tr and the stress ratio (R). For alloy 182 weld metal under short tr and/or low R, the crack growth rate assuming SCC is much lower than those of the test data. For alloy 182 under tr = 30 and 1000 s at R = 0.8, the crack growth rate assuming SCC almost coincided with test data. For heat affected zone (HAZ) of alloy 600 base metal (600HAZ), the crack growth rate assuming SCC had much different slope of da/dN-ΔK relationship compared with the test data in the tested range of tr up to 3000 s. From these observations, the contribution of SCC is relatively small and the main mechanism of crack growth is thought to be fatigue for the tested range (tr=1 to 1000 s for weld metal, tr=1 to 3000 s for base metal and R = 0.1 to 0.8). It was assured that the fatigue crack growth formula proposed by the authors accounts the effect of SCC adequately at long tr. Additionally, the applicability of the fatigue crack growth rate formula for austenitic stainless steels to the long term cyclic load was investigated and it was found that the formula can be applied to tr=30000 s.

scholarly journals Study on the Influence of the Gurson–Tvergaard–Needleman Damage Model on the Fatigue Crack Growth Rate

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1183
Author(s):  
Edmundo R. Sérgio ◽  
Fernando V. Antunes ◽  
Diogo M. Neto ◽  
Micael F. Borges
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Plastic Strain ◽  
Crack Growth ◽  
Damage Model ◽  
Crack Tip ◽  
Strength Parameter ◽  
Stress Intensity Factor Range

The fatigue crack growth (FCG) process is usually accessed through the stress intensity factor range, ΔK, which has some limitations. The cumulative plastic strain at the crack tip has provided results in good agreement with the experimental observations. Also, it allows understanding the crack tip phenomena leading to FCG. Plastic deformation inevitably leads to micro-porosity occurrence and damage accumulation, which can be evaluated with a damage model, such as Gurson–Tvergaard–Needleman (GTN). This study aims to access the influence of the GTN parameters, related to growth and nucleation of micro-voids, on the predicted crack growth rate. The results show the connection between the porosity values and the crack closure level. Although the effect of the porosity on the plastic strain, the predicted effect of the initial porosity on the predicted crack growth rate is small. The sensitivity analysis identified the nucleation amplitude and Tvergaard’s loss of strength parameter as the main factors, whose variation leads to larger changes in the crack growth rate.

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