Crack Growth Characteristics of Pure Copper for Smart Stress Memory Patch

2007 ◽  
Vol 353-358 ◽  
pp. 2045-2048
Author(s):  
Shoichi Nambu ◽  
Manabu Enoki
Keyword(s):  
Crack Propagation ◽  
Crack Length ◽  
Crack Growth ◽  
Stress Amplitude ◽  
Pure Copper ◽  
Growth Behavior ◽  
Growth Characteristics ◽  
Crack Growth Behavior ◽  
Stress Memory ◽  
The Relationship

A new sensing method called “smart stress memory patch”, which could estimate the maximum stress, the stress amplitude and the fatigue cyclic number simultaneously using Kaiser effect of Acoustic Emission (AE) and crack length of this patch, was developed. In this study, the crack growth characteristics of this patch was evaluated. Pure copper was used for this patch because its good corrosion resistance, stable crack propagation and so on. Two kinds of samples which were rolled and electrodeposited copper were prepared to investigate the effect of microstructure on crack growth behavior. Fatigue test was performed under constant stress amplitude to evaluate the crack growth behavior using the relationship between stress intensity factor range and crack propagation rate. The scattering in fatigue crack growth was also investigated to obtain the relationship between crack length and the fatigue cyclic number including two-sided 95% confidence interval. The effect of thickness and grain size on the scattering was discussed. Finally, good crack growth behavior was obtained and the fatigue cyclic number could be estimated by this patch.

Development of Smart Stress Memory Sensor Using AE Kaiser Effect

2006 ◽  
Vol 321-323 ◽  
pp. 244-247
Author(s):  
Shoichi Nambu ◽  
Yoshihiko Tsunawaki ◽  
Manabu Enoki
Keyword(s):  
Crack Propagation ◽  
Crack Length ◽  
Maximum Stress ◽  
Stress Amplitude ◽  
Pure Copper ◽  
Residual Lifetime ◽  
Kaiser Effect ◽  
Stress Memory ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

Reliability of structures is an important task to ensure the ease and safety of our life, and further development of non-destructive evaluation for structures such as bridges and tunnels is required. Some fatigue sensors that consist of sacrificed specimen have been developed to evaluate the fatigue damage of structures such as fatigue cyclic number and residual lifetime. However, these fatigue sensors can be used only when the applied stress amplitude is known. We tried to develop a new smart stress memory patch that measured both maximum stress and number of fatigue cycles simultaneously using Kaiser effect of Acoustic Emission (AE) and crack length. In this study, the characteristics of the smart patch was evaluated. Pure copper was used for this sensor because its good corrosion resistance, stable crack propagation and detectability of AE near yield point. Fatigue test was performed under the constant stress amplitude to evaluate the crack propagation behavior using the relationship between stress intensity factor and crack propagation rate. The obtained curve between crack length and number of fatigue cycles by these crack propagation behavior was in good agreement with experimental results. AE measurement after some fatigue tests was performed and AE was detected at the applied fatigue stress. These results demonstrated that number of fatigue cycles and the maximum stress could be measured by this fatigue sensor.

Fatigue Crack Growth Behavior of Autofrettaged Hydrogen Pressure Vessel Made of Low Alloy Steel

2017 ◽  
Author(s):  
Yoru Wada ◽  
Yusuke Yanagisawa
Keyword(s):  
High Pressure ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Cylindrical Specimen ◽  
Growth Behavior ◽  
Gaseous Hydrogen ◽  
Crack Growth Behavior ◽  
Low Alloy Steel

Autofrettage is used to known as an effective method to prevent fatigue crack propagation of thick-walled cylinder vessels operating under high pressure. Since low-alloy steel shows an enhanced crack growth rate in high-pressure gaseous hydrogen, this paper aims to validate the effect of autofrettage on crack growth behavior in high-pressure gaseous hydrogen utilizing 4%NiCrMoV steel (SA723 Gr3 Class2). An autofrettaged cylindrical specimen with a 70mm inside diameter and 111mm outside diameter was prepared with an axial EDM (depth of 1mm) notched on the inside surface. The measured residual stress profile coincides well with the calculated results. The fatigue crack growth test was conducted by pressurizing the cylinder and varying the external water pressure. Crack propagation from the EDM notch was observed in the non-autofrettaged cylindrical specimen while no crack propagation was observed when the initial EDM notch size was within the compressive residual stress field. When the initial EDM notch size was increased, the fatigue crack growth showed a narrow, groove-like fracture surface for the autofrettaged specimen. In order to qualitatively analyze those results, fatigue crack growth rates were examined under various load ratios including a negative load ratio using a fracture mechanics specimen. From the information obtained, crack growth analysis of an autofrettaged cylinder in a high-pressure hydrogen environment was successfully demonstrated with a fracture mechanics approach.

Effects of Loading Spectra on High pH Crack Growth Behavior of X65 Pipeline Steel

CORROSION ◽  
10.5006/3472 ◽  
2020 ◽  
Vol 76 (6) ◽  
pp. 601-615 ◽  
Author(s):  
Hamid Niazi ◽  
Karina Chevil ◽  
Erwin Gamboa ◽  
Lyndon Lamborn ◽  
Weixing Chen ◽  
...  
Keyword(s):  
Free Surface ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Strain Rate ◽  
Crack Growth ◽  
Pipeline Steel ◽  
Crack Tip ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Secondary Crack

The effects of mechanical factors on crack growth behavior during the second stage of high pH stress corrosion cracking in pipeline steel were investigated by applying several loading scenarios on compact tension (CT) specimens. The main mechanism for stage 2 of intergranular crack propagation is anodic dissolution ahead of the crack tip which is highly dependent on crack-tip strain rate. The maximum and minimum crack growth rates were 3 × 10−7 mm/s and 1 × 10−7 mm/s, respectively. It was observed that several factors such as mean stress intensity factor, amplitude, and frequency of loading cycles determine the crack-tip strain rate. Low R-ratio cycles, particularly high-frequency ones, enhance secondary crack initiation, and crack coalescence on the free surface. This mechanism accelerates crack advance on the free surface which is accompanied with an increase in mechanical driving force for crack propagation in the thickness direction. These findings have implications for pipeline operators and could be used to increase the lifespan of the cracked pipelines at stage 2. For those pipelines, any loading condition that increases the strain rate ahead of the crack tip enhances anodic dissolution and is detrimental. Additionally, secondary crack initiation and coalescence could be minimized by avoiding internal pressure fluctuation, particularly rapid large pressure fluctuations.

Study on the Influence of Crack Growth Behavior on Fatigue Life in Simulated Reactor Coolant Environment of Different Temperature

2020 ◽  
Author(s):  
Tatsuru Misawa ◽  
Takanori Kitada ◽  
Takao Nakamura
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Reactor Coolant ◽  
Different Temperatures

Abstract It has been clarified that the fatigue life is decreased in the fatigue test of high-temperature and high-pressure water that simulates PWR reactor coolant environment compared to that in the atmosphere. Temperature, strain rates, dissolved oxygen concentration, etc. affect the decrease of fatigue life. The influence of crack growth behavior on the fatigue life of Type 316 austenitic stainless steel [1] in simulated PWR reactor coolant environment of different temperatures was investigated in this study. Fatigue tests were conducted under different temperatures (200°C and 325°C) in a simulated PWR reactor coolant environment with interrupting, and cracks generated on the specimen surface were observed with two-step replica method. From the results of observation, the influence of crack growth behavior in different temperatures on the fatigue life was clarified. As a result, it was confirmed that the decrease of the fatigue life due to high temperature is mainly caused by the acceleration of crack propagation rate in the depth direction by the increase of crack coalescence frequency due to the increase of crack initiation number and crack propagation rate in the length direction.

Non-Relaxing Crack Growth and Fatigue in a Non-Crystallizing Rubber

1974 ◽  
Vol 47 (5) ◽  
pp. 1253-1264 ◽  
Author(s):  
P. B. Lindley
Keyword(s):  
Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Maximum Deformation ◽  
Fatigue Data ◽  
Tentative Explanation ◽  
Tearing Energy ◽  
Relationship Of ◽  
The Relationship ◽  
Unique Relationship

Abstract The crack growth behavior of a non-crystallizing rubber, SBR, is investigated in terms of the tearing energy T, the energy available for crack growth. For cyclic deformations in which the minimum tearing energy is zero (relaxing conditions), a unique relationship is obtained between the growth per cycle and T at the maximum deformation. This rubber also exhibits crack growth at constant tearing energies. The relationship of the crack growth rate as a function of tearing energy, when the minimum tearing energy of the cycle is not zero, can be superimposed on the relaxing relationship by scaling the rates, and a tentative explanation is proposed for the scaling factor. Fatigue data are consistent with this.

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.

scholarly journals Cyclic Crack Growth in Chemically Tailored Isotropic Austenitic Steel Processed by Electron Beam Powder Bed Fusion

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6544
Author(s):  
Matthias Droste ◽  
Ruben Wagner ◽  
Johannes Günther ◽  
Christina Burkhardt ◽  
Sebastian Henkel ◽  
...  
Keyword(s):  
Electron Beam ◽  
Crack Propagation ◽  
Austenitic Steel ◽  
Crack Growth ◽  
Manganese Content ◽  
Growth Behavior ◽  
Austenitic Steels ◽  
Crack Growth Behavior ◽  
Powder Bed Fusion ◽  
Powder Bed

The present study analyzes the cyclic crack propagation behavior in an austenitic steel processed by electron beam powder bed fusion (PBF-EB). The threshold value of crack growth as well as the crack growth behavior in the Paris regime were studied. In contrast to other austenitic steels, the building direction during PBF-EB did not affect the crack propagation rate, i.e., the crack growth rates perpendicular and parallel to the building direction were similar due to the isotropic microstructure characterized by equiaxed grains. Furthermore, the influence of significantly different building parameters was studied and, thereby, different energy inputs causing locally varying manganese content. Crack growth behavior was not affected by these changes. Even a compositional gradation within the same specimen, i.e., crack growth through an interface of areas with high and areas with low manganese content, did not lead to a significant change of the crack growth rate. Thus, the steel studied is characterized by a quite robust cyclic crack growth behavior independent from building direction and hardly affected by typical parameter deviations in the PBF-EB process.

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