scholarly journals The Effect of Loading Rate on the Environment-Assisted Cracking Behavior of AA7075-T651 in Aqueous NaCl Solution

2021 ◽  
Vol 2 (3) ◽  
pp. 360-375
Author(s):  
Zachary D. Harris ◽  
James T. Burns
Keyword(s):  
Stress Intensity ◽  
Crack Growth ◽  
Growth Rates ◽  
Loading Rate ◽  
Nacl Solution ◽  
Cracking Behavior ◽  
Testing Methodology ◽  
Rate Dependent ◽  
Specific Focus ◽  
Crack Growth Rates

The influence of loading rate on the environment-assisted cracking (EAC) behavior of AA7075-T651 immersed in 0.6 and 1.0 M NaCl solution was assessed at applied potentials ranging from −800 to −1200 mVSCE via a slow-rising stress intensity (K) testing methodology. Measured crack growth rates under rising K loading are compared to those obtained using a fixed K protocol, which revealed that rising K-based testing consistently yields increased crack growth rates relative to static K approaches across all tested conditions. However, relative to other alloy systems, EAC in AA7075-T651 is only modestly loading rate-dependent, as demonstrated by testing conducted at fixed dK/dt ranging from 0.25 to 2.0 MPaÖm/h. The implications of the observed results are considered in the context of current EAC testing specifications, with specific focus on the conservatism and efficiency of rising K-based approaches.

Crack Growth in Stainless Steel 304 under Creep-Fatigue Loading

2007 ◽  
Vol 353-358 ◽  
pp. 485-490 ◽  
Author(s):  
Y.M. Baik ◽  
K.S. Kim
Keyword(s):  
Stress Intensity Factor ◽  
Stainless Steel ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Static Loading ◽  
Fatigue Loading ◽  
Creep Fatigue ◽  
Crack Growth Rates

Crack growth in compact specimens of type 304 stainless steel is studied at 538oC. Loading conditions include pure fatigue loading, static loading and fatigue loading with hold time. Crack growth rates are correlated with the stress intensity factor. A finite element analysis is performed to understand the crack tip field under creep-fatigue loading. It is found that fatigue loading interrupts stress relaxation around the crack tip and cause stress reinstatement, thereby accelerating crack growth compared with pure static loading. An effort is made to model crack growth rates under combined influence of creep and fatigue loading. The correlation with the stress intensity factor is found better when da/dt is used instead of da/dN. Both the linear summation rule and the dominant damage rule overestimate crack growth rates under creep-fatigue loading. A model is proposed to better correlate crack growth rates under creep-fatigue loading: 1 c f da da da dt dt dt Ψ −Ψ     =         , where Ψ is an exponent determined from damage under pure fatigue loading and pure creep loading. This model correlates crack growth rates for relatively small loads and low stress intensity factors. However, correlation becomes poor as the crack growth rate becomes large under a high level of load.

Effect of Salt Water Temperature on the Crack Growth Characteristics of 12 Chrome Steel

1974 ◽  
Vol 96 (2) ◽  
pp. 81-87 ◽  
Author(s):  
R. Eisenstadt ◽  
K. M. Rajan
Keyword(s):  
Stress Intensity ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Growth Rates ◽  
Salt Water ◽  
Water Solution ◽  
Correction Term ◽  
Growth Data ◽  
Rotating Beam ◽  
Crack Growth Rates

The corrosion fatigue crack growth rates on 12 chrome steels of typical composition, 12Cr, 0.2C, 1Mo, 1W, of 150,000-ksi yield is relatively unaffected by 4.5 percent NaCl salt water solution at room temperature. There is a significant rise in the crack growth rates of 12 chrome steels with increasing temperature for salt water corrosion fatigue of about 4 to 1 for 160 deg F—4.5 percent solution. In correlating rotating beam understressing data on average crack growth rate versus stress intensity factor with 0-maximum data generated by other techniques, the value 1−R Kmax equivalent to n = 0.5 in the expression Keff = Kmax (1 − R)n correlates the rotating beam data adequately with the 0-Max data for other techniques. A correction factor for eccentric crack fronts on solid round specimens for rotating beam crack growth data to calculate stress intensity factors for solid notched round bars has been developed. The correction term is 4rd2 for the following stress intensity expression. K1=2.257Mr3+4rd20.80t+7.12r−1/2

The influence of mean stress on fatigue crack propagation in a quenched and tempered alloy steel

1977 ◽  
Vol 12 (2) ◽  
pp. 81-88 ◽  
Author(s):  
E H R Wade ◽  
G M C Lee
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Front ◽  
Mean Stress ◽  
Free Surfaces ◽  
Front Profile ◽  
Crack Growth Rates

A series of tests are reported which support the proposal that fatigue crack growth rates are retarded by crack closure at low values of applied mean stress intensity. In particular, the evidence presented indicates that closure occurs most readily at the specimen's free surfaces. This leads to dramatic changes in crack front profile under certain loading conditions.

A Superposition Approach for Time-Dependent Fatigue Crack Growth

2012 ◽  
Author(s):  
Fashang Ma
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Time Dependent ◽  
Crack Growth Rates ◽  
Time Dependent Crack Growth

High temperature fatigue crack growth is a combination of fatigue, creep and environmental attack, which greatly enhance fatigue crack growth. In order to understand the damage mechanisms and develop a physically based crack growth model, systematic experimental research has been conducted under various loading conditions for different specimen geometries made from a high strength nickel alloy. Test results from this work showed that time-dependent fatigue crack growth rates differ significantly from those observed in conventional fatigue crack growth tests. Crack geometry and loading history significantly affect fatigue crack growth rate. These results suggest the need for a change in the K based superposition approach for time-dependent crack growth modeling. A phenomenological model has been developed to predict time-dependent crack growth under various loading histories and crack geometries. In this model an effective stress intensity factor is defined to account for the effects of constraint loss of fracture mechanics due to crack-tip plasticity, and the creep stress relaxation on stress intensity factor. It is found the model can accurately predict the dwell crack growth rates for different crack geometries under various loading conditions.

Experimental Investigations of Fatigue Crack Propagation for Pipe Under Torsional Loading

2010 ◽  
Author(s):  
Motoki Nakane ◽  
Satoshi Kanno ◽  
Shota Hashimoto ◽  
Takayuki Watanabe ◽  
Yukio Takahashi
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Growth Rates ◽  
Torsional Loading ◽  
Crack Growth Rates

This study discusses methods for evaluating fatigue crack propagation under torsional loading for pipes. To achieve this objective, fatigue crack propagation tests were carried out on both stainless steel and carbon steel used in piping systems of nuclear power plants. Two different kinds of pipes were tested in this study. These pipes had the same shape but the diameter and thickness of the larger pipe were twice those of the smaller pipe. The nominal shear stress amplitudes applied to the specimen were set between 50 and 100 MPa depending on the dimension of the specimen and desired crack growth rates. All fatigue tests were conducted under pure torsional loading with stress ratio R = −1 and at room temperature. The geometrical correction factors for the specimen were derived from elastic J-integral calculated by the FEM. The fatigue crack propagation tests results show that the crack growth rates estimated by the elastic stress intensity factor with the geometrical correction factor were much faster than curves prescribed in The Japan Society of Mechanical Engineers (JSME) codes. These results suggest that elastic plastic fracture parameters should be considered into the stress intensity factor because yield stresses for torsional loading would be smaller than those of uniaxial loading. The plastic zone correction method and modified reference stress method were examined as alternative methods. The crack growth rates estimated by the proposed methods almost totally correspond to the JSME curves. The two proposed methods were found to be quite effective at correctly evaluating the crack growth rates under torsional loading.

scholarly journals Investigation of the Enhancement Interactions between Double Parallel Cracks on Fatigue Growth Behaviors

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2952
Author(s):  
Zhichao Han ◽  
Caifu Qian ◽  
Huifang Li
Keyword(s):  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Growth Rates ◽  
Shielding Effect ◽  
Enhancement Effect ◽  
Intensity Factors ◽  
Single Crack ◽  
Parallel Cracks ◽  
Crack Growth Rates

In this paper, interactions of double parallel cracks were studied by performing experiments and numerical simulations. Fatigue crack propagation tests were carried out to measure crack growth rates in the specimens with double parallel cracks or a single crack. Finite element method was adopted to calculate stress intensity factors at the crack tips. Results show that the double parallel cracks at different positions present a shielding effect or enhancement effect on crack growth rates and stress intensity factors. When the double parallel cracks are offset, crack interactions mostly behave as enhancement effects. Empirical formulas were obtained to calculate the stress intensity factor at the “dangerous” crack tip of the double parallel cracks. By modifying the material parameters in Paris equation of the single crack, the double parallel cracks are simplified into a single crack with the same crack growth rates.

Fatigue Crack Growth in Steels 42CrV and IR3Mo

2004 ◽  
Vol 261-263 ◽  
pp. 1179-1184 ◽  
Author(s):  
Qin Zhi Fang
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Measurement System ◽  
Growth Rates ◽  
Fatigue Tests ◽  
Intensity Factors ◽  
Growth Measurement ◽  
Crack Growth Rates

An automatic fatigue crack growth measurement system was developed, in which a special four-channel A-D acquisition board that could collect data in phase was used. The data collecting frequency is in the range of 4×(2~25600)Hz. The system is suitable for fatigue tests with the frequencies not higher than 250Hz. Eddy current transducers and standard load cell were used to measure displacement and load, respectively. The system can instantly calculate fatigue crack lengths, stress intensity factors and fatigue crack growth rates. As an application of the system, fatigue crack growth rates (FCG) and the thresholds of steels 42CrV and IR3Mo were presented.

Sign in / Sign up

Export Citation Format

Share Document