Influence of cyclic loading parameters and aqueous media on the crack growth rate in steels

1985 ◽  
Vol 21 (3) ◽  
pp. 215-224 ◽  
Author(s):  
V. I. Pokhmurskii ◽  
I. P. Gnyp
Keyword(s):  
Growth Rate ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Aqueous Media

Fatigue Crack Growth Rate of Reeled Pipe in Sour Environments

2015 ◽  
Author(s):  
Javad Safari ◽  
Ramgopal Thodla ◽  
Ian Merchant ◽  
John Hamilton
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Paris Law ◽  
Number Of Cycles ◽  
Corrosive Environments

Fatigue Crack Growth Rate (FCGR) of reeled pipe (strained & aged) in sour environments was investigated. FCGR frequency scans on different microstructures, i.e. heat affected zone (HAZ), and weld center line (WCL), revealed that, FCGR in corrosive environments increased with decreasing frequency and reached a plateau value at low frequencies of 10mHz to 3mHz. At these ‘plateau frequencies’, FCGR in the moderately sour environment that was investigated were found to be about 10–18× or 30× higher than the in-air values for the WCL and HAZ, respectively. There was no effect of the reeling cycles on the FCGR of the WCL or HAZ specimens. The FCGRs of the WCL were consistently lower than that of the HAZ by about a factor of 2–3× under various conditions. The reason for the lower FCGR of the WCL is not well understood. It is possible that it may be due to the higher yield strength (YS) of the overmatched welds, differing hydrogen concentration and/or diffusion coefficient or possibly due to the differences in the microstructure between the HAZ and WCL. Paris law curves, FCGRs as a function of ΔK (stress intensity factor range), were measured on the HAZ, and WCL (both intrados) at the plateau frequency (10mHz), representative of flowline cyclic loading. They were also measured at a higher frequency of 0.33Hz, representative of Steel Catenary Risers (SCR) cyclic loading associated with wave motion. Comparisons of measured Paris law curves in corrosive environments to those in air were consistent with the results of the frequency scans. There was no effect of number of cycles of reeling on the Paris law curves in the sour environment tested for WCL and HAZ specimens at both the plateau frequency and 0.33Hz. The results of the test program suggest FCGR of WCL and HAZ in the sour environment tested are not affected by number of cycles (up to 5) of straining on the intrados side for the strain level (1.93% per cycle) used in this study.

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.

Influence of the composition of a hydrogen sulfide containing medium on crack growth rate in cyclic loading

1984 ◽  
Vol 20 (3) ◽  
pp. 226-228
Author(s):  
A. I. Radkevich ◽  
M. D. Klapkiv ◽  
T. S. Dolotova ◽  
I. I. Vasilenko
Keyword(s):  
Growth Rate ◽  
Hydrogen Sulfide ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Crack Growth

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.

Crack propagation in elastomers subjected to cyclic loading

2019 ◽  
Vol 233 (11) ◽  
pp. 2301-2310
Author(s):  
Adel Hamdi ◽  
Abdelkader Boulenouar ◽  
Noureddine Benseddiq ◽  
Sofiane Guessasma
Keyword(s):  
Growth Rate ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Crack Propagation ◽  
Crack Growth ◽  
Shear Loading ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Fracture Surfaces ◽  
Styrene Butadiene

This work tackles crack propagation mechanisms of styrene butadiene and natural rubbers, both subject to cyclic loading under a positive load ratio. The experimental evidence is based on pure shear loading of notched specimens supported by SEM analysis of fracture surfaces. Relationship between crack growth rate and tearing energy is revisited. The experimental results show that the fatigue behaviour of studied vulcanisates can be clearly separated in the power-law regime. Furthermore, the reported results from the literature extend this statement to any load condition. Fracture surface observations reveal also differences in energy dissipation mechanisms inferred to structural mutations in the case of natural rubber. Alternation of rough and smooth fracture surfaces associated with change in crack growth rate is more likely to occur for styrene butadiene rubber. All observations suggest that crack branching is a secondary ranked dissipation mechanism for the studied materials compared to crack deviation.

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