Environmentally Controlled Fatigue Crack-Growth Rates in SAE 4340 Steel—Temperature Effects

1970 ◽  
Vol 92 (1) ◽  
pp. 121-125 ◽  
Author(s):  
J. T. Ryder ◽  
J. P. Gallagher
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Corrosion Fatigue ◽  
Distilled Water ◽  
Corrosion Fatigue Crack

The temperature dependence of sustained-loading and corrosion-fatigue crack-propagation behavior of SAE 4340 steel immersed in distilled water was investigated using the fracture mechanics approach. During the load cycle, stress-intensity histories had values higher than the static threshold stress intensity (KIscc). For a stress-intensity range of 20 ksi in., a factor of 30 increase in the corrosion-fatigue crack-growth rate was noted for a temperature increase of 70 deg C. The mechanical variables were found to have much less influence than the environmental reaction rate. In contrast with dry air results, the fatigue crack-growth rate in a distilled water environment was dependent on the mean stress-intensity for stress-intensity histories above KIscc. This dependence varied with temperature level.

scholarly journals Effect of Various Factors Produced by Welding on the Corrosion Fatigue Crack Growth Rate

1987 ◽  
Vol 36 (12) ◽  
pp. 774-780
Author(s):  
Toshio Terasaki ◽  
Tetsuya Akiyama ◽  
Masatoshi Eto ◽  
Yasuhumi Matsuo ◽  
Masaharu Kusuhara
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Corrosion Fatigue ◽  
Corrosion Fatigue Crack ◽  
Corrosion Fatigue Crack Growth

Effect of Hold-Time Interspersed With Cyclic Loading on Corrosion Fatigue Crack Growth Rate of a Steel in Sodium Chloride Solution

2018 ◽  
Author(s):  
Raghu V. Prakash ◽  
Dhinakaran Sampath
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Corrosion Fatigue ◽  
Hold Time ◽  
Corrosion Fatigue Crack ◽  
Corrosion Fatigue Crack Growth

Corrosion fatigue growth behavior of structural steels at low cyclic frequency is characterized by an increase in crack growth rate in the threshold and Paris regions, due to the simultaneous action of cyclic mechanical load (fatigue) and corrosive environment. Knowledge on the effect of load sequence on corrosion fatigue crack growth is important to set out the realistic design and prognosis criteria for components operating under corrosive environments. In this study, the corrosion fatigue crack growth rate under the effect of hold-time (1000s), at a maximum stress intensity factor (Kmax), interspersed during cyclic load on was studied experimentally on a Mn-Ni-Cr steel under 3.5% NaCl solution at a constant stress intensity factor range (ΔK) of 15 MPa √m; the corrosion crack growth rate was evaluated for three different frequencies of: 0.01, 0.1 and 1 Hz. As a result of hold time at the peak load, the exposure time for the crack-tip to interact with the environment increased, which could enhance the corrosion crack growth rates. To verify if this corrosion effect can be contained, electrode potential of (−) 850 mV and (−) 950 mV SCE was applied to the specimen to reduce the extent of corrosion contribution to crack growth rate. The fatigue crack growth rate (da/dN) increased when the frequency was decreased from 1 to 0.01 Hz at all electrode potentials. However, the crack growth rate at 0.01 Hz increased by an order of magnitude with a tensile hold at Kmax for 1000 s compared with the crack growth rate during continuous cyclic load for a given electrode potential. The crack growth rate reduced when the electrode potential was decreased to −950 mV SCE. The enhancement of corrosion fatigue crack growth rate with the introduction of a hold-time is explained using crack-tip strain rate assisted anodic dissolution.

A Review of Fatigue and SCC Crack Growth Rate Relationships for Ferritic and Stainless Steels and Ni-Cr-Fe Materials in BWR Environment

2006 ◽  
Author(s):  
Hardayal S. Mehta
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Corrosion Fatigue ◽  
Full Range ◽  
Water Environment ◽  
Plant Component

When in-service inspection of a nuclear plant component reveals the presence of cracking, an engineering evaluation (typically called a justification for continued operation, or JCO) is required to demonstrate the structural suitability for continued operation. A key element in such a flaw evaluation is the projected crack growth over the period when the cracked component will be reinspected. The crack growth is expected to be a combination of stress corrosion cracking (SCC) and corrosion fatigue. The ASME Section XI Code is in the process of developing a full range of SCC and corrosion fatigue crack growth rate relationships (CGRs) for stainless steel and Ni-Cr-Fe materials. The objective of this paper is to summarize several available SCC and fatigue crack growth rate relationships for these materials exposed to boiling water reactor (BWR) water environments. For completeness, low alloy steel SCC and corrosion fatigue CGRs in BWR water environment are also briefly reviewed. Two example evaluations are provided that used some of these CGRs in developing the JCOs for BWR components. A detailed comparison of these CGRs along with a review of the underlying data will be part of a future effort undertaken by the ASME Section XI Task Group.

Long Fatigue Cracks — Microstructural Effects and Crack Closure

MRS Bulletin ◽  
1989 ◽  
Vol 14 (8) ◽  
pp. 25-36 ◽  
Author(s):  
P.K. Liaw
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Load Ratio ◽  
Stress Intensity Range ◽  
Intensity Range

Fracture mechanics technology is an effective tool for characterizing the rates of fatigue crack propagation. Generally, fatigue crack growth rate (da/dN) in each loading cycle can be presented as a function of stress intensity range (ΔK), where ΔK = Kmax — Kmin, Kmax and Kmin are the maximum and the minimum stress intensities, respectively. A typical fatigue crack growth rate curve of da/dN versus ΔK can be divided into three regimes, i.e., Stage I (near-threshold), Stage II (Paris), and Stage III (fast) crack growth regions, as shown in Figure 1.Depending on the region of crack growth, fatigue crack growth behavior can be sensitive to microstructure, environment, and loading conditions [e.g., R (load) ratio = Kmin / Kmax]. In the nearthreshold region, fatigue crack growth rates are very slow, ranging from approximately 10−10 to 10−8 m/cycle. In this region, the fatigue crack growth rate curve eventually reaches a threshold stress intensity range, ΔKth, below which the crack would not grow or grow at an extremely slow rate. Typically, the value of ΔKth is operationally defined as the stress intensity range which gives a corresponding crack growth rate of 10−10 m/cycle. In the nearthreshold region, the influence of microstructure, environment, and load ratio on the rates of crack propagation is very significant.

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