Cohesive Zone Modeling of Hydrogen Assisted Cracking in a 15-5 PH Steel and Comparison With Experiments

2015 ◽  
Author(s):  
Giovambattista Bilotta ◽  
Mandana Arzaghi ◽  
Gilbert Hénaff ◽  
Guillaume Benoit ◽  
Clara Moriconi ◽  
...  
Keyword(s):  
Crack Growth ◽  
Growth Rates ◽  
Cohesive Zone ◽  
Hydrogen Pressure ◽  
Crack Tip ◽  
Gaseous Hydrogen ◽  
Zone Model ◽  
Loading Frequency ◽  
High Hydrogen ◽  
Crack Growth Rates

Gaseous hydrogen substantially reduces fracture properties such as threshold stress intensity factor and crack growth resistance in the precipitation-hardened martensitic stainless steel investigated in this study. Fatigue crack propagation tests were performed on CT specimens under different atmospheres (hydrogen pressures from 0.09 to 40 MPa) on the Hycomat test bench, at the Pprime Institute in Poitiers, France. A strongly enhanced crack growth regime was identified at high hydrogen pressure and low-frequency loading. Crack growth rates obtained at a constant load under same pressure levels suggest that a combination of tensile stresses above a threshold (KIscc) and fatigue cycles contribute to the hydrogen embrittlement at the crack tip. These experimental results were compared to the finite element simulation results obtained by a recently developed cohesive zone model at the crack tip. A specifically developed traction-separation law which is suitable to describe the gradual degradation of cohesive stresses under monotonic and cyclic loadings, and which is furthermore sensitive to the hydrogen concentration was used. The effects of the different testing conditions, in terms of loading frequency and hydrogen pressure, on the modeling results are discussed. It was shown that the model qualitatively predicts the detrimental influence of gaseous hydrogen on the crack growth rates.

scholarly journals Fatigue Crack Growth Behaviour of High Strength Ferritic Steels in High Pressure Hydrogen

2018 ◽  
Vol 165 ◽  
pp. 03008
Author(s):  
Ashok Saxena ◽  
Kevin Nibur
Keyword(s):  
High Pressure ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Hydrogen Pressure ◽  
Gaseous Hydrogen ◽  
Loading Frequency ◽  
Crack Growth Rates ◽  
Pressure Hydrogen

The design of safe and low-cost, high-pressure hydrogen storage systems are a critical need for harnessing clean power but must consider the propensity of hydrogen to accelerate fatigue crack growth rates in the construction materials. Design of safe pressure vessels needs robust models for predicting crack growth rates and how they are affected by variables such as loading frequency, load ratios, hydrogen pressure, gaseous impurities, temperature, and material variability. In this study, fatigue crack growth rates were measured in the liner material in 10 MPa gaseous hydrogen at various load ratios, R, in the range -1 ≤ R ≤ 0.2. The effects of varying loading frequency were investigated, and the results were pooled with those from literature for similar alloys tested in 103 MPa gaseous hydrogen pressure. The differences in crack growth rates between H2 pressures of 10 to 103 MPa as well as the effects of frequency on the environment assisted crack growth rates were assessed. Loading frequency effects tend to saturate at frequencies of 1 Hz and less. H2 pressure effects appear to saturate at pressures of 45MPa, while load ratio effects are not significant for –1 ≤ R ≤ 0.2 but become important for R ≥ 0.2.

scholarly journals Application of a Cohesive Zone Model for Simulating Fatigue Crack Growth from Moderate to High ΔK Levels of Inconel 718

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Huan Li ◽  
Jinshan Li ◽  
Huang Yuan
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Small Scale ◽  
Model Parameters ◽  
Zone Model ◽  
Crack Growth Rates

A cyclic cohesive zone model is applied to characterize the fatigue crack growth behavior of a IN718 superalloy which is frequently used in aerospace components. In order to improve the limitation of fracture mechanics-based models, besides the predictions of the moderate fatigue crack growth rates at the Paris’ regime and the high fatigue crack growth rates at the high stress intensity factor ΔK levels, the present work is also aimed at simulating the material damage uniformly and examining the influence of the cohesive model parameters on fatigue crack growth systematically. The gradual loss of the stress-bearing ability of the material is considered through the degradation of a novel cohesive envelope. The experimental data of cracked specimens are used to validate the simulation result. Based on the reasonable estimation for the model parameters, the fatigue crack growth from moderate to high ΔK levels can be reproduced under the small-scale yielding condition, which is in fair agreement with the experimental results.

Effect of Constraint Induced by Specimen Geometries on Crack Growth Behavior Under Creep-Fatigue Interaction

2018 ◽  
Author(s):  
Lei Zhao ◽  
Lianyong Xu
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Tip ◽  
Crack Growth Behavior ◽  
Growth Behaviour ◽  
Crack Growth Behaviour ◽  
Creep Fatigue ◽  
Crack Growth Rates

Creep-fatigue interaction would accelerate the crack growth behaviour and change the crack growth mode, which is different from that presenting in pure creep or fatigue regimes. In addition, the constraint ahead of crack tip affects the relationship between crack growth rate and fracture mechanics and thus affects the accuracy of the life prediction for high-temperature components containing defects. In this study, to reveal the role of constraint caused by various specimen geometries in the creep-fatigue regime, five different types of cracked specimens (including C-ring in tension CST, compact tension CT, single notch tension SENT, single notch bend SENB, middle tension MT) were employed. The crack growth and damage evolution behaviours were simulated using finite element method based on a non-linear creep-fatigue interaction damage model considering creep damage, fatigue damage and interaction damage. The expression of (Ct)avg for different specimen geometries were given. Then, the variation of crack growth behaviour with various specimen geometries under creep-fatigue conditions were analysed. CT and CST showed the highest crack growth rates, which were ten times as the lowest crack growth rates in MT. This revealed that distinctions in specimen geometry influenced the in-plane constraint level ahead of crack tip. Furthermore, a load-independent constraint parameter Q* was introduced to correlate the crack growth rate. The sequence of crack growth rate at a given value of (Ct)avg was same to the reduction of Q*, which shown a linear relation in log-log curve.

Influence of Load Ratio, Rise Time and Waveform on the Corrosion Fatigue Crack Growth of Austenitic Stainless Steel in a PWR Primary Coolant Environment

2007 ◽  
Author(s):  
Norman Platts ◽  
David Tice ◽  
Keith Rigby ◽  
John Stairmand
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Weld Metal ◽  
Crack Growth ◽  
Growth Rates ◽  
Rise Time ◽  
Load Ratio ◽  
Loading Frequency ◽  
Primary Coolant ◽  
Crack Growth Rates

The rate of growth of flaws in reactor circuit components by fatigue is usually determined using the reference crack growth curves in Section XI of the ASME Boiler and Pressure Vessel Code. These curves describe the rate of crack propagation per cycle (da/dN) as a function of the applied stress intensity factor range (ΔK). No reference curves for water-wetted defects in austenitic stainless steels are currently available. This paper describes the results of testing of austenitic stainless steel and weld metal in simulated PWR primary coolant over a range of temperatures and mechanical loading conditions. Previous data presented by the authors on wrought stainless steel demonstrated that crack growth rates can be significantly enhanced by the PWR primary environment at temperatures between 150°C and 300°C. The current study extends these data to weld metal and also investigates the impact of other loading waveforms (e.g. trapezoidal loading) on the degree of environmental enhancement. The environmental enhancement increases significantly with reducing loading frequency and decreases with decreasing water temperature. The environmental influence on fatigue is shown to be independent of load ratio over the range R = 0.1 to R = 0.8. The level of enhancement is frequently smaller at very high R ratio (≥0.85) with the enhanced rates of fatigue frequently being unsustained at these high load ratios. There is a strong correlation between the rise time and the level of enhancement of crack growth rate over inert crack growth rates at all temperatures tested. Weld metal has been shown to exhibit similar behavior to wrought material over the whole temperature range studied although the apparent rates of enhancement relative to average inert crack growth rates are lower than found for wrought material. For complex loading waveforms (e.g. trapezoidal loading with hold periods at maximum or minimum load) it is possible predict the level of enhancement on the basis of the test data generated using simpler saw tooth loading regimes.

scholarly journals Orientation Dependence of Hydrogen Accelerated Fatigue Crack Growth Rates in Pipeline Steels

2018 ◽  
Author(s):  
Eun Ju Song ◽  
Joseph A. Ronevich
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Growth Rates ◽  
Orientation Dependence ◽  
Gaseous Hydrogen ◽  
Crack Growth Rates

One of the most efficient methods for supplying gaseous hydrogen long distances is by using steel pipelines. However, steel pipelines exhibit accelerated fatigue crack growth rates in gaseous hydrogen relative to air. Despite conventional expectations that higher strength steels would be more susceptible to hydrogen embrittlement, recent testing on a variety of pipeline steel grades has shown a notable independence between strength and hydrogen assisted fatigue crack growth rate. It is thought that microstructure may play a more defining role than strength in determining the hydrogen susceptibility. Among the many factors that could affect hydrogen accelerated fatigue crack growth rates, this study was conducted with an emphasis on orientation dependence. The orientation dependence of toughness in hot rolled steels is a well-researched area; however, few studies have been conducted to reveal the relationship between fatigue crack growth rate in hydrogen and orientation. In this work, fatigue crack growth rates were measured in hydrogen for high strength steel pipeline with different orientations. A significant reduction in fatigue crack growth rates were measured when cracks propagated perpendicular to the rolling direction. A detailed microstructural investigation was performed, in an effort to understand the orientation dependence of fatigue crack growth rate performance of pipeline steels in hydrogen environments.

An Analysis of Elevated Temperature Fatigue and Creep Crack Growth

1976 ◽  
Vol 98 (4) ◽  
pp. 473-479 ◽  
Author(s):  
M. Do¨ner
Keyword(s):  
Elevated Temperature ◽  
Crack Growth ◽  
Growth Rates ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Creep Damage ◽  
Material Constant ◽  
Temperature Oxidation ◽  
Oxidation Damage ◽  
Crack Growth Rates

Existing crack growth laws which consider time and temperature effects are examined. Based on phenomenological observations, as well as mechanistic considerations, one of these laws is modified in order to provide an improved, universal elevated temperature crack growth law. It is assumed that there are essentially three processes through which crack growth rates are affected: decrease in strength and modulus with temperature, oxidation damage at the crack tip and creep damage at the crack tip. The rate controlling mechanism(s) which may be associated with each of these processes are discussed. The type of experiments which are needed for the determination of material constant(s) that describe the contribution from each process are outlined. The modified crack growth law, when applied to publish data on HS-188 alloy, results in a prediction of the crack growth rates within a factor of 2.5, in the temperature range of 873–1144 K and at cycle frequencies ranging from 0.01 to 10 Hz.

Measurement of Fatigue Crack Growth Rates for Steels in Hydrogen Storage

2009 ◽  
Author(s):  
Yoru Wada ◽  
Kouichi Takasawa ◽  
Ryoji Ishigaki ◽  
Yasuhiko Tanaka ◽  
Tadao Iwadate
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Depth ◽  
Load Ratio ◽  
Gaseous Hydrogen ◽  
Test Machine ◽  
Critical Crack ◽  
Crack Growth Rates

Fatigue crack growth rates (da/dN) in up to 90MPa high-pressure gaseous hydrogen environments of quenched and tempered low alloy Cr-Mo steel: JIS-SCM435 with ultimate tensile strength level of 950MPa were measured utilizing a cycle, ranging from 0.3sec from 1000sec long with a road ratio R = 0.1. The longer cycle time tests (15sec to 1000sec per cycle) were conducted utilizing internal pressure test apparatus by utilizing cylinder (= CY) specimens, while shorter cycle (0.3sec to 25sec per cycle) tests were performed utilizing fatigue test machine using compact tension (= C(T)) specimens. Crack depth of CY specimens were measured by Time Of Flight Diffraction (TOFD) technique and the crack length of C(T) specimens were measured by compliance technique. Both C(T) and CY specimen showed accelerated sub-critical crack growth in gaseous hydrogen compared that in air or inert gas atmosphere. The effect of load ratio was also evaluated.

scholarly journals Numerical Simulation of Fatigue Crack Growth Rate and Crack Retardation due to an Overload Using a Cohesive Zone Model

2014 ◽  
Vol 891-892 ◽  
pp. 777-783 ◽  
Author(s):  
Sarmediran Silitonga ◽  
Johan Maljaars ◽  
Frans Soetens ◽  
Hubertus H. Snijder
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Crack Tip ◽  
Zone Model ◽  
Cohesive Elements

In this work, a numerical method is pursued based on a cohesive zone model (CZM). The method is aimed at simulating fatigue crack growth as well as crack growth retardation due to an overload. In this cohesive zone model, the degradation of the material strength is represented by a variation of the cohesive traction with respect to separation of the cohesive surfaces. Simulation of crack propagation under cyclic loads is implemented by introducing a damage mechanism into the cohesive zone. Crack propagation is represented in the process zone (cohesive zone in front of crack-tip) by deterioration of the cohesive strength due to damage development in the cohesive element. Damage accumulation during loading is based on the displacements in the cohesive zone. A finite element model of a compact tension (CT) specimen subjected to a constant amplitude loading with an overload is developed. The cohesive elements are placed in front of the crack-tip along a pre-defined crack path. The simulation is performed in the finite element code Abaqus. The cohesive elements behavior is described using the user element subroutine UEL. The new damage evolution function used in this work provides a good agreement between simulation results and experimental data.

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