The Crack Growth Evaluation of A335 P22 Steels by Acoustic Emission

2005 ◽  
Vol 297-300 ◽  
pp. 2083-2089
Author(s):  
Gee Wook Song ◽  
Jung Seob Hyun ◽  
Sung Ho Chang ◽  
Bum Shin Kim
Keyword(s):  
Acoustic Emission ◽  
Crack Propagation ◽  
Crack Growth ◽  
Compact Tension ◽  
Fatigue Tests ◽  
Remaining Service Life ◽  
Operation Conditions ◽  
Long Time ◽  
Actual Operation ◽  
Stress Ratios

Acoustic emission (AE) technique was used to investigate fatigue crack growth on compact tension specimens of aging materials at room temperature. Test materials have been sampled steam pipe serviced the actual operation conditions for a long time in fossil power plant. The compact tension test specimens were subjected to load stress ratios of 0.33, 0.5, and 0.66. All the fatigue tests were performed at a frequency of 1Hz. The test results indicate that acoustic emission counts show reasonable correlation with crack propagation rates for applied stress ratios. When the crack growth rates increase, AE’s counts and energies show increment. Also, the higher stress ratios, the faster crack propagation rates. Based on these relationships it may be possible to predict the remaining service life of fatigue-damaged steam pipes.

Fatigue Analysis of FRP Strengthened Masonry by Acoustic Emission Monitoring

2019 ◽  
Vol 817 ◽  
pp. 594-601 ◽  
Author(s):  
Alessandro Grazzini ◽  
Giuseppe Lacidogna
Keyword(s):  
Acoustic Emission ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Fiber Reinforced Polymers ◽  
Test Duration ◽  
Time Behavior ◽  
Damage Growth ◽  
Reinforced Polymers ◽  
Safety Work ◽  
Long Time

The safety work of historical and monumental building heritage requires the use of innovative materials compatible with the high architectural value. The Fiber Reinforced Polymers (FRP) represent a valid alternative to traditional ones, and the carbon fiber sheets are very light and easy to glue to the masonry structures. However, the durability of the application of FRP sheets is still uncertain in the long time behavior, especially with regard to cyclic fatigue loads such as seismic ones. In this work an experimental analysis on a set of strengthened masonry walls under fatigue tests (loading and freezing-thawing test) has been carried out in order to evaluate creep effects. During cyclic tests in the laboratory it was possible to monitor the damage pattern through the acoustic emission (AE) technique. The AE monitoring is useful to estimate the amount of energy released from fracture propagation in the adherence surface between masonry and FRP sheet. The different phases of damage evolution are recognized through the analysis of AE data over time. In particular, the time dependence of AE counting number is useful to indicate the beginning of the unstable damage growth and predicts the possible failure of the specimens at the 80% of the test duration. Furthermore, a sudden decay in the AE frequency is detected during the last phase of the fatigue tests. These results illustrate the applicability and the advantages of AE technique for the monitoring of long-term damage growth in strengthened masonry.

Effect of Environment on Fatigue Crack Propagation Behavior of an Al-Cu-Mg Aluminum Alloy

2014 ◽  
Vol 1004-1005 ◽  
pp. 142-147
Author(s):  
Ming Liu ◽  
Kun Zhang ◽  
Sheng Long Dai ◽  
Guo Ai Li ◽  
Min Hao ◽  
...  
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Fatigue Crack Growth Rate ◽  
Fatigue Crack Propagation Behavior ◽  
Stress Ratios

The fatigue crack propagation behaviors of an Al-Cu-Mg alloy are investigated in different environments and with varying stress ratios. Fatigue experiments are carried out via a fatigue crack growth rate test in laboratory air, a 3.5% (mass fraction) NaCl solution and a tank seeper. The results show that a corrosion environment has an obvious influence on the fatigue crack growth rate, and the degrees of influence of the two different corrosive environments are basically identical. When the stress ratio is R = 0.5 and 0.06 with a decrease of the stress intensity factor, the difference in the crack propagation rates for the corrosion and air environments gradually increases. However, the corrosion acceleration in each stage of crack propagation is obvious while R=−1.

Designing Light Alloys for Fatigue Crack Growth Resistance

2011 ◽  
Vol 690 ◽  
pp. 393-396
Author(s):  
Anastasios G. Gavras ◽  
Diana A. Lados
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
High Stress ◽  
Compact Tension ◽  
Fatigue Crack Growth Resistance ◽  
Reduction Strategies ◽  
Stress Ratios ◽  
And Performance ◽  
Wrought Aluminum

Fatigue crack growthresistance is critical to the design and performance of structural components.This study focuses on understanding the microstructural mechanisms of fatigue crack propagation in commonly used structural materials, cast and wrought aluminum and titanium alloys, with various microstructures resulting from changes in chemistry or heat treatment (A535-F, 6061-T6, and mill- and b-annealed Ti-6Al-4V).Stress ratio effects were evaluated by conducting fatigue crack growth tests on compact tension specimens at low, intermediate, and high stress ratios, R=0.1, 0.5, and 0.7, respectively. Initial flaw size effects were also studied by performing small crack growth tests at R=0.1. Data reduction strategies compensating for closure and Kmax effects on crack growth and design curves will be presented.

Effect of Hydrogen Gas on the Growth of Small Fatigue Crack in JIS-SCM435

2014 ◽  
Vol 891-892 ◽  
pp. 942-947
Author(s):  
Hisatake Itoga ◽  
Hisao Matsunaga ◽  
Saburo Matsuoka
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
Ambient Air ◽  
Compact Tension ◽  
Fatigue Tests ◽  
Hydrogen Gas ◽  
Small Crack ◽  
Strain Intensity ◽  
Small Fatigue Crack ◽  
Small Cracks

The fatigue crack growth (FCG) from a small hole in a low alloy steel JIS-SCM435 round bar was investigated using tension-compression fatigue tests in 0.7 MPa hydrogen gas and ambient air. In the higher FCG rate regime (e.g. da/dN > 108 m/cycle), FCG was accelerated in hydrogen gas compared to in air. On the other hand, in the lower FCG rate regime (e.g. da/dN < 108 m/cycle), FCG in hydrogen was rather slower than that in air. There was no noticeable difference in fatigue limits between these two atmospheres. The FCG in the respective atmospheres showed a typical small crack behavior, i.e. the da/dN for small cracks were much greater than those for large cracks obtained by compact tension (CT) specimen when they were compared at the same ΔK level. In order to unify such a discrepancy of FCG behavior between small crack and large crack, the strain intensity factor range ΔKε was adopted. As a result, the da/dN data for various crack sizes was gathered in a narrow band, i.e. the small crack effect was successfully evaluated with the strain intensity. Moreover, the crack growth life was predicted based on the da/dN-ΔKε relation. The reproduced S-N curve showed a conservative agreement with the fatigue life obtained by experiments.

scholarly journals Numerical Analysis of Fatigue Crack Growth Path and Life Predictions for Linear Elastic Material

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3380
Author(s):  
Abdulnaser M. Alshoaibi ◽  
Yahya Ali Fageehi
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Growth Path ◽  
Linear Elastic ◽  
Crack Growth Path

The main objective of this work was to present a numerical modelling of crack growth path in linear elastic materials under mixed-mode loadings, as well as to study the effect of presence of a hole on fatigue crack propagation and fatigue life in a modified compact tension specimen under constant amplitude loading condition. The ANSYS Mechanical APDL 19.2 is implemented for accurate prediction of the crack propagation paths and the associated fatigue life under constant amplitude loading conditions using a new feature in ANSYS which is the smart crack growth technique. The Paris law model has been employed for the evaluation of the mixed-mode fatigue life for the modified compact tension specimen (MCTS) with different configuration of MCTS under the linear elastic fracture mechanics (LEFM) assumption. The approach involves accurate evaluation of stress intensity factors (SIFs), path of crack growth and a fatigue life evaluation through an incremental crack extension analysis. Fatigue crack growth results indicate that the fatigue crack has always been attracted to the hole, so either it can only curve its path and propagate towards the hole, or it can only float from the hole and grow further once the hole has been lost. In terms of trajectories of crack propagation under mixed-mode load conditions, the results of this study are validated with several crack propagation experiments published in literature showing the similar observations. Accurate results of the predicted fatigue life were achieved compared to the two-dimensional data performed by other researchers.

Experimental Study on Fatigue Crack Propagation of Glare3-3/2 with Mechanics Properties

2012 ◽  
Vol 600 ◽  
pp. 273-278
Author(s):  
Zong Hong Xie ◽  
Tian Jiao Zhao ◽  
Rui Wu
Keyword(s):  
Growth Rate ◽  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Stress Level ◽  
Maximum Stress ◽  
Fatigue Tests

This study is to investigate the fatigue crack growth behavior of Glare3-3/2 under various stress levels. The Glare3-3/2 specimen consists of three 2024-T3 aluminum alloy sheets and two layers of glass/epoxy composite lamina. Tensile-tensile cyclic fatigue tests were conducted on centrally notched specimen at four stress levels with various maximum values. A digital camera system was used to take photos of the propagating cracks on both sides of the specimen. Image processing software was adopted to accurately measure the length of the cracks on each photo. The test results show that 1) Compared to 2024-T3 aluminum alloy, the fatigue properties of Glare3-3/2 are much better: under the same loading condition with maximum stress level of 120MPa, the crack growth rate of Glare3-3/2 is roughly 5% of the corresponding value of 2024-T3 aluminum alloy, while the fatigue life is 4 times higher than that of 2024-T3 aluminum alloy. 2) The maximum stress level shows strong influence on fatigue crack propagation behavior of Glare3-3/2. The value of steady state crack growth rate increases linearly, while the number of load cycles decreases exponentially, with respect to the maximum stress values used in the fatigue tests.

scholarly journals Fatigue crack analysis of ferrite material by acoustic emission technique

2019 ◽  
Vol 13 (2) ◽  
pp. 5074-5089
Author(s):  
Md. T. I. Islam Khan ◽  
A. A. Rashid ◽  
R. Hidaka ◽  
N. Hattori ◽  
Md. M. Islam
Keyword(s):  
Acoustic Emission ◽  
Fractal Dimension ◽  
Crack Propagation ◽  
Fatigue Loading ◽  
Dynamic Monitoring ◽  
Dynamic Crack ◽  
Propagation Behavior ◽  
Novel Approach ◽  
Crack Volume ◽  
Long Time

Recently in various fields, numerous researches are going on for the assessment of material damage on the basis of crack initiation and propagation. Various methods are available in NDT for this purpose, among which analysis using released acoustic emission (AE) waves due to crack propagation is very effective due to its dynamic monitoring features. Various approaches are proposed for long time to make it an ideal method for accurate monitoring of crack behaviors in materials. In fragmentation theory there are some proportionality among the relations of AE event, AE energy, area and volume of cracks etc., which are calculated from the released AE waves from any dynamic crack. It has been found that the necessity of calculating the fractal dimension is important in verifying these relationships. This parameter is emphasized for determining the geometry of the irregularity in crack surface and crack volume. In this paper a novel approach based on image processing is proposed to find out the fractal dimension for analyzing the crack propagation characteristics. Finally, the proportionality relationships of AE parameters with crack propagation behavior in ferrite cast iron under fatigue loading are demonstrated experimentally.

Three Dimensional Criterion for Creep Crack Propagation in C(T) Specimen

2016 ◽  
Vol 853 ◽  
pp. 142-147
Author(s):  
Wen Ming Ye ◽  
Xu Teng Hu ◽  
Wan Lin Guo ◽  
Ying Dong Song
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Growth Rates ◽  
Three Dimensional ◽  
Creep Crack Growth ◽  
Growth Control ◽  
Compact Tension ◽  
Thickness Effect ◽  
Creep Crack ◽  
Crack Growth Rates

Experimental of two kinds of compact tension (CT) specimens’ creep crack propagation are carried out in this paper. Traditional fracture mechanics and three-dimensional fracture theory are compared and the results show that: The K-Tz two-parameter model can eliminate the thickness-effect on the crack growth rates in the relatively low K range, however when K exceed certain values the effect of thickness for crack growth rates still exists; The Ct and Ct-Tz model can describe the thickness-effect of creep crack growth rates in regions of high Ct; When the crack tip stress intensity factor K of the two kinds of thickness (B=5 mm, B=10 mm) specimens equal to 35 and 31 respectively, this material’s creep crack growth control parameter change from K to Ct.

Definition of Fatigue Crack Growth Thresholds for Ferritic Steels in Fitness-for-Service Codes

2018 ◽  
Author(s):  
Kunio Hasegawa ◽  
Bohumir Strnadel
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Stress Ratio ◽  
Fatigue Tests ◽  
Ferritic Steels ◽  
Stress Ratios ◽  
Definition Of ◽  
Crack Growth Rates

Fatigue crack growth rates are expressed as a function of the stress intensity factor ranges. The fatigue crack growth thresholds are important characteristics of fatigue crack growth assessment for the integrity of structural components. Almost all materials used in these fatigue tests are ferritic steels. As a result, the reference fatigue crack growth rates and the fatigue crack growth thresholds for ferritic steels were established as rules and they were provided by many fitness-for-service (FFS) codes. However, the thresholds are not well defined in the range of negative stress ratio. There are two types of thresholds under the negative stress ratio. That is, constant thresholds and increment of thresholds with decreasing stress ratios. The objective of this paper is to introduce the thresholds provided by FFS codes and to analyze the thresholds using crack closure. In addition, based on the experimental data, definition of the threshold is discussed to apply to FFS codes. Finally, threshold for ferritic steels under the entirely condition of stress ratio is proposed to the ASME Code Section XI.

The use of the C∗ parameter in predicting creep crack propagation rates

1977 ◽  
Vol 12 (3) ◽  
pp. 167-179 ◽  
Author(s):  
M P Harper ◽  
E G Ellison
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Compact Tension ◽  
Single Edge ◽  
Single Edge Notch ◽  
Creep Crack ◽  
Edge Notch ◽  
Single Edge Notch Bend ◽  
Good Agreement

The applicability of the C∗ parameter for the prediction of creep crack propagation rates is considered. A new method for estimating C∗ is presented, the results from which show good agreement with those from an existing technique. Experimental results from creep crack growth tests, conducted on a 1 Cr Mo V steel using both compact tension and single edge notch bend specimens, indicate that good correlation with C∗ is obtained once the effects of stress redistribution become negligible. Finally, comparisons are drawn between C∗ and other possible correlating parameters, and the limitations of each approach are discussed.

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