Evaluation of Crack Growth Behavior of Alloy 625 Under Cyclic Loading in a Steam Environment at 750°C

2011 ◽  
Author(s):  
Yoichi Takeda ◽  
Hirofumi Sato ◽  
Shuhei Yamamoto ◽  
Takamichi Tokunaga ◽  
Akio Ohji
Keyword(s):  
Growth Rate ◽  
High Temperature ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Crack Length ◽  
Crack Growth ◽  
Loading Rate ◽  
Transition Period ◽  
Growth Behavior ◽  
Crack Growth Behavior

Advanced ultra supercritical (A-USC) steam power generation, in which high-pressure steam is raised to beyond 700°C, is being studied internationally. The creep strength of Ni-based super alloys evaluated at these high temperatures in an air environment makes these materials promising candidates for the material to be used for the structural components of these generators. Since they are exposed to high temperature steam, it is important that the effect of the environment on the degradation of these materials is investigated. In this investigation, the crack growth rate under cyclic loading in a 750°C steam environment using a compact tension specimen was evaluated. Crack length monitoring using the direct current potential drop technique was applied to the growing crack in a high temperature environment in order to evaluate the time-dependent behavior of the crack growth. The dependence of the loading rate and amplitude in terms of the stress intensity factor was obtained. The crack growth rate increased with decreasing loading rate and increasing amplitude. Multiple loading patterns were applied to a single specimen during crack length monitoring. When the loading pattern was changed to a different pattern, in most of the cases, the crack growth rate started to change and then became stable aftera transition period. The influence of intermetallics and different phases on the crack growth behavior is discussed based on the oxidation rate of these phases.

Predicting the Crack Growth Behavior in a Filled Elastomer

2006 ◽  
Vol 3-4 ◽  
pp. 273-278
Author(s):  
C.T. Liu ◽  
M. Yen ◽  
H.K. Ching
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Length ◽  
Crack Growth ◽  
Growth Model ◽  
Initial Crack ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Initial Crack Length ◽  
Crack Growth Model

In this study, single-edge cracked uniaxial specimens with an initial crack length of 0.1 in. or 0.3 in. and wedge-shaped sheet specimens with an initial crack length of 0.3 in were tested at a constant displacement rate of 50 in/min under 1000 psi confining pressure. The specimens were made of a highly filled polymeric material, containing 86% by weight of hard particles embedded in a rubbery matrix, which was made of polybutadiene-acrylic acid-acrylonitrile rubber. The uniaxial crack growth data were used to develop a crack growth model, relating crack growth rate da/dt and Mode I stress intensity factor KI. The developed crack growth model was used to predict the crack growth behavior in the wedge-shaped specimen. The results of the analysis indicated that the predicted crack growth rate compared well with the experiment

Mode I Ductile Crack Growth of CT Specimen Under Large Cyclic Loading

2017 ◽  
Author(s):  
Kiminobu Hojo ◽  
Shinichi Kawabata
Keyword(s):  
Growth Rate ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Mode I ◽  
Ductile Crack ◽  
Hardening Rule ◽  
Ductile Crack Growth

Ductile crack growth calculation method under excessive cyclic loading in a fitness for service rule has not been established even in Mode I. The authors simulated ductile crack growth behavior of CT specimens under cyclic loading executed in a committee of the Japan Welding Society. Sensitivity of the used stress-strain curves by monotonic or cyclic loading and the effect of the hardening rule were investigated. For evaluation of the crack growth rate under excessive cyclic loading, the parameter ΔJ was applied and compared with the rate of the JSME rules for FFS.

Experiment and Modeling of Fatigue Crack Growth With Altering Loading Direction

2009 ◽  
Author(s):  
Wenfeng Tu ◽  
Xiaogui Wang ◽  
Zengliang Gao
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Growth Behavior ◽  
Cyclic Plasticity ◽  
Crack Growth Behavior ◽  
Loading Direction

The experiments of mixed Mode I-II fatigue crack growth with altering loading direction were conducted with compact specimens made of 16MnR steel. The specimens were tested under three loading steps. When the crack reached a certain length in the first step, the loading direction was switched to a certain angle. Finally, the loading direction was returned to the original orientation. The crack grow direction had a tendency perpendicular to the loading axis. Right after the loading direction was changed, the crack growth rate was retarded. A new approach developed was used to predict the crack growth behavior. The elastic-plastic stress analysis was performed using the finite element method with the implementation of a cyclic plasticity model. Based on the stress-strain response, fatigue damage near the crack tip was determined by a multi-axial fatigue criterion. Both the crack growth rate and cracking direction were obtained according to the maximum fatigue damage distribution on the critical material plane. The predictions for the crack growth behavior including the crack growth rate and crack growth path were in agreement with the experimental data.

scholarly journals Effect of Material Heterogeneity on Environmentally Assisted Cracking Growth Rate of Alloy 600 for Safe-End Welded Joints

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6186
Author(s):  
Kuan Zhao ◽  
Shuai Wang ◽  
He Xue ◽  
Zheng Wang
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Welded Joints ◽  
Welding Process ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Alloy 600 ◽  
Material Heterogeneity ◽  
Environmentally Assisted Cracking

Environmentally assisted cracking (EAC) is essential in predicting light water reactors’ structural integrity and service life. Alloy 600 (equivalent to Inconel 600) has excellent corrosion resistance and is often used as a welding material in welded joints, but material properties of the alloy are heterogeneous in the welded zone due to the complex welding process. To investigate the EAC crack growth behavior of Alloy 600 for safe-end welded joints, the method taken in this paper concerns the probability prediction of the EAC crack growth rate. It considers the material heterogeneity, combining the film slip-dissolution/oxidation model, and the elastic-plastic finite element method. The strain rate at the crack tip is a unique factor to describe the mechanical state. Still, it is challenging to accurately predict it because of the complicated and heterogeneous material microstructure. In this study, the effects of material heterogeneity on the EAC crack growth behavior are statistically analyzed. The results show that the material heterogeneity of Alloy 600 can not be ignored because it affects the prediction accuracy of the crack growth rate. The randomness of yield strength has the most influence on the EAC growth rate, while Poisson’s ratio has the smallest.

Statistical Analysis of Creep Crack Growth Behavior in Modified 9Cr-1Mo Steel

2010 ◽  
Vol 654-656 ◽  
pp. 516-519
Author(s):  
Seon Jin Kim ◽  
Woo Gon Kim ◽  
Ik Hee Jung ◽  
Yong Wan Kim
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Probability Distribution ◽  
Weibull Distribution ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Creep Crack ◽  
Creep Crack Growth Rate

In this paper, a series of statistical studies were conducted on creep crack growth behavior of Grade 9Cr-1Mo steel for next generation reactor. Creep crack growth tests were performed on pre-cracked compact tension (CT) specimens under the applied load ranges from 3800 to 5000N at the identical temperature condition of 600oC. The creep crack growth behavior has been analyzed statistically using the empirical equation between crack growth rate da/dt and C* parameter, namely da/dt=B(C*)q. First, the determination methods of B and q obtained from experiments were investigated by the least square fitting method and the mean value method. The probability distribution functions of B and q have been investigated using the normal, log-normal and Weibull distribution. The constant B and q are followed well 2-parameter Weibull. Second, the creep crack growth rate data were generated by Monte-Carlo simulation method assuming the 2-parameter Weibull in B and q parameters. The probability distribution of creep crack growth rate for arbitrary C* parameter values seems to follow well Weibull distribution.

SMALL CRACK GROWTH BEHAVIOR AND EVALUATION OF GROWTH RATE OF COPPER PROCESSED BY EQUAL CHANNEL ANGULAR PRESSING

2012 ◽  
Vol 06 ◽  
pp. 245-250
Author(s):  
KUSNO KAMIL ◽  
MASAHIRO GOTO ◽  
SEUNG-ZEON HAN ◽  
KWANGJUN EUH ◽  
NORIO KAWAGOISHI ◽  
...  
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Plastic Zone Size ◽  
Growth Behavior ◽  
Small Crack ◽  
Stress Intensity Factor Range ◽  
Crack Growth Behavior ◽  
Angular Pressing ◽  
Average Grain Size

Ultrafine grained copper processed by 4 cycles of equal angular pressing was fatigued to study the growth behavior of a small crack. After the crack initiation, the behavior of a major crack was monitored through plastic replication technique, showing that the crack growth rate is proportional to the crack length regardless of stress amplitudes. The crack growth rate of major cracks was evaluated by a term σanl, not by the stress intensity factor range, ΔK. Analysis on fracture surfaces by scanning electron microscopy showed a planar followed by a striated surface. The formation mechanism of fracture surface morphologies was discussed by considering the average grain size and the reversible plastic zone size at a crack tip.

Analytical Prediction of Fatigue Crack Growth Behavior Under Biaxial Loadings

2012 ◽  
Author(s):  
Ragupathy Kannusamy ◽  
K. Ramesh
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Applied Load ◽  
Biaxial Loading ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior

Aircraft and pressure vessel components experience stresses that are negative biaxial or multiaxial in nature. Biaxiality is defined as the ratio of stress applied parallel and normal to the crack front. In recent years many experimental studies have been conducted on fatigue crack growth under various biaxial loading conditions. Biaxial loadings affect crack front stresses and strains, fatigue crack growth rate and direction, and crack tip plastic zone size and shape. Many of these studies have focused on positive biaxial loading cases. No conclusive study has been reported out yet that accurately quantifies the influence of negative biaxiality on fatigue crack growth behavior. Lacking validation, implementation on real life problems remains questionable. To ensure safe and optimum designs, it is necessary to better understand and quantify the effect of negative biaxial loading on fatigue crack behavior. In this paper, attempts were made to quantify the effect of biaxial load cases ranging from B = −0.5 to 1.0 on fatigue crack growth behavior. Also an attempt has been made to establish a simplified approach to incorporate the effect of biaxiality into da/dN curves generated from uniaxial loading using an analytical approach without conducting expensive biaxial crack growth testing. Sensitivity studies were performed with existing test data available for AA2014-T6 aluminum alloy. Detailed elastic–plastic finite element analyses were performed with different stress ranges and stress ratios with various crack sizes and shapes on notched and un-notched geometries. Constant amplitude loads were applied for the current work and comparison studies were made between uniaxial and different biaxial loading cases. It was observed from the study that negative biaxiality has a very pronounced effect on the crack growth rate and direction for AA2014-T6 if the externally applied load exceeds 20% of the yield strength as compared with 40% of externally applied load for alloy of steel quoted in the literature.

Environmental Effect of Crack Growth Rate of Pipeline Steel in Near-Neutral pH Soil Environments

2004 ◽  
Author(s):  
Weixing Chen ◽  
Robert Sutherby
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Soil Chemistry ◽  
Pipeline Steel ◽  
Crack Tip ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
General Corrosion ◽  
Neutral Ph

The laboratory work reported here was initiated to determine whether different soils can be shown to give rise to different growth rate for a given pipeline steel. Two soil synthetic environments with different near neutral pH value were designed based on various soil chemistries collected near the pipeline in the field where near-neutral pH SCC was found. The crack growth behavior in both the environments were determined using compact tension specimen. The crack growth rate was in situ monitored by the potential drop system. It was found that soil chemistry has a profound effect on crack growth rate. Although it is insensitive to the soil chemistry and cyclic frequency, the crack growth rate in the high ΔK regime has been significantly enhanced in comparison with that in air. In the low ΔK regime, the growth rate is shown to have minor dependence on ΔK value but strong dependence on the testing environments. The observed crack growth behavior in different ΔK regimes and environments was related to the crack tip sharpness and crack crevice wideness as a result of corrosion and room temperature creep deformation. Soil solutions with low general corrosion rate are associated with a blunt crack tip and wide crack crevice, which would result in lower stress intensity at the crack tip and weaker crack closure effect, respectively. Similarly, a loading wave allowing shorter creep time on a given volume of material at the crack tip at high loading stress tends to produce a sharper crack tip and narrow crack crevice. These two factors have opposite effect on crack growth rate, and the observed crack growth rate reflects the combined effect of these two opposite factors.

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