Comparison of Two Damage Models for Prediction of Failure in Stress Corrosion Cracking

2018 ◽  
Author(s):  
Sorabh Singhal ◽  
Yogeshwar Jasra ◽  
Ravindra K. Saxena
Keyword(s):  
Crack Initiation ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Driving Force ◽  
Damage Mechanics ◽  
Damage Model ◽  
Corrosion Cracking ◽  
Force Model ◽  
Initiation Time ◽  
Damage Models

In the present work, Stress corrosion cracking (SCC) and its mechanical behavior are presented. SCC represents complex behavior due to electrochemical and mechanical interaction. Damage models are proposed to predict crack initiation time for stainless steel under constant load using the concept of continuum damage mechanics to show incremental damage accumulation which finally leads to failure of the material. Two damage models applicable to prediction of damage in SCC, Lemaitre damage model and damage driving force model proposed by Kamaya are compared. The comparative study of the results obtained by these damage models shows that in Lemaitre damage law cracks initiate randomly while in damage driving force model the stress concentration occurs around the periphery of damaged element results in increased damage force. The study can be used to estimate the crack initiation time in SCC under corrosive atmosphere.

scholarly journals The Application of Reliability-Based Design Factors in Stress Corrosion Cracking Evaluations

2002 ◽  
Author(s):  
Edward Friedman
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Initiation ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Initiation Time ◽  
Reliability Based Design ◽  
Design Factors

First-order reliability methodology (FORM) is used to develop reliability-based design factors for deterministic analyses of stress corrosion cracking. The basic elements of FORM as applied to structural reliability problems are reviewed and then employed specifically to stress corrosion cracking evaluations. Failure due to stress corrosion cracking is defined as crack initiation followed by crack growth to a critical depth. The stress corrosion cracking process is thus represented in terms of a crack initiation time model and a crack growth rate model, with the crack growth rate integrated from the initiation time to the time at which the crack grows to its critical depth. Both models are described by log-normal statistical distribution functions. A procedure is developed to evaluate design factors that are applied to the mean values of the crack initiation time and the crack growth rate for specified temperature and stress conditions. The design factors, which depend on the standard deviations of the statistical distributions, are related to a target reliability, which is inversely related to an acceptable probability of failure. The design factors are not fixed, but are evaluated on a case-to-case basis for each application. The use of these design factors in a deterministic analysis assures that the target reliability will be attained and the corresponding acceptable probability of failure will not be exceeded. An example problem illustrates use of this procedure.

Threshold for Stress Corrosion Cracking Initiation of Alloy X750 under Long-Term Uniaxial Constant Load Test in High-Temperature Water

CORROSION ◽  
2004 ◽  
Vol 60 (3) ◽  
pp. 229-236 ◽  
Author(s):  
M. Yamamoto ◽  
J. Kuniya ◽  
S. Uchida
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Stress Corrosion ◽  
Applied Stress ◽  
Stress Level ◽  
Stress Corrosion Cracking ◽  
Pure Water ◽  
Constant Load ◽  
Corrosion Cracking ◽  
Load Test

Abstract Uniaxial constant load (UCL) tests of the nickel-based alloy X750 (UNS N07550) were performed in high-temperature pure water (288°C, 8 ppm dissolved oxygen [DO]) to investigate stress corrosion cracking (SCC) fracture time and the crack initiation process. The SCC fracture was initiated at a stress level below the 0.2% offset yield stress and many small cracks were observed in the middle of the nonfractured test specimens. The distribution of the crack length for each observation time is shown by Weibull probability distributions. Crack initiation and propagation process had different behavior depending on the applied stress level and the stress intensity factor at the crack tip. SCC initiation at the minimum applied stress is discussed with respect to the grain size, which depended on the size of an initial crack.

Initiation of Stress Corrosion Cracking; Migration of Chloride in Oxide Films on Austenitic Stainless Steel

CORROSION ◽  
1964 ◽  
Vol 20 (9) ◽  
pp. 269t-274t ◽  
Author(s):  
C. R. BERGEN
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Initiation ◽  
Tensile Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Base Alloy ◽  
Corrosion Cracking ◽  
Stress Cracking ◽  
High Nickel

Abstract The mechanism of stress corrosion crack initiation can perhaps be understood by noticing the similarities among the several corrodent-crack susceptible alloy systems. In a number of such systems the specific ion responsible for cracking is relatively large. The corrosion product formed in a corroding medium containing such ions would imbibe them. Under appropriate conditions, due to their size, the larger ions would tend to diffuse to the region of the oxide film under highest tensile stress where local high tensile stress in the base alloy would be reflected. It is postulated that the appropriate conditions for diffusion are present in stress cracking systems and that the migration of the ion to which cracking is ascribed leads to high local concentrations in turn causing a local increase in corrosivity. Where the physical properties of the alloy are such that crack propagation can occur, stress corrosion cracking results. Tests of the above hypothesis have been conducted with the chloride-austenitic stainless steel system. It was shown that chloride will migrate reversibly under the influence of tensile stress. It was also shown that the presence of nickel will inhibit the migration of chloride up a tensile gradient and the immunity to cracking of high nickel austenitic stainless alloys is attributed to this effect.

Mechanisms of High-pH and Near-Neutral-pH SCC of Underground Pipelines

2001 ◽  
Vol 123 (3) ◽  
pp. 147-151 ◽  
Author(s):  
John A. Beavers ◽  
Brent A. Harle
Keyword(s):  
Crack Initiation ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Historical Information ◽  
High Ph ◽  
Neutral Ph ◽  
Underground Pipelines ◽  
Ph Stress

This paper provides an overview of mechanisms for high-pH and near-neutral pH stress corrosion cracking of underground pipelines. Characteristics and historical information on both forms of cracking are discussed. This information is then used to support proposed mechanisms for crack initiation and growth.

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