scholarly journals Fatigue life and crack growth behavior of post welded Aluminum 5183 alloy

2018 ◽  
Vol 165 ◽  
pp. 21013 ◽  
Author(s):  
Vidit Gaur ◽  
Manabu Enoki ◽  
Toshiya Okada ◽  
Syohei Yomogida
Keyword(s):  
Grain Size ◽  
Fatigue Life ◽  
Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Mean Stress ◽  
Threshold Values ◽  
R Ratio ◽  
Fatigue Failures ◽  
Mean Stresses

In this study we investigated the fatigue life and crack growth behavior of Al-5183 alloy. Microscopic analysis revealed nearly equi-axed grains and no texture in longitudinal or cross-sectional plane of the welded plates. Gas porosities with an average size of 45 μm, comparable to grain size (55 μm), were present and often initiate fatigue failures. Load-controlled cyclic tests at different stress-ratios (R = -1, -0.5, 0.1, 0.5. 0.7 and 0.8) revealed decrease in fatigue lives with increase in R-ratio. At R > 0.7, no fatigue failure could be observed, suggesting a probable mean-stress saturation effect on fatigue. Mean stress also tends to control the crack initiation sites: surface initiated failures at low mean stresses while sub-surface pores induced failures at higher mean stresses. Fatigue-crack growth tests on CT specimens at different R-ratios (0.1, 0.5 and 0.8) revealed reduction in crack growth rates (and in threshold values) with increasing R-ratio. The ΔK applied for pores responsible for fatigue failures were often lower than or near to the threshold values and also, the size of such pores was of order of magnitude of grain size, thus crack initiated from pores are short cracks and further tests are progress.

scholarly journals Influence of Pre-Stress Magnitude on Fatigue Crack Growth Behavior of Al-Alloy

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1267
Author(s):  
Chunguo Zhang ◽  
Weizhen Song ◽  
Qitao Wang ◽  
Wen Liu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Shot Peening ◽  
Fatigue Property ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Al Alloy ◽  
Fatigue Crack Growth Behavior

From tensile overload to shot peening, there have been many attempts to extend the fatigue properties of metals. A key challenge with the cold work processes is that it is hard to avoid generation of harmful effects (e.g., the increase of surface roughness caused by shot peening). Pre-stress has a positive effect on improving the fatigue property of metals, and it is expected to strength Al-alloy without introducing adverse factors. Four pre-stresses ranged from 120 to 183 MPa were incorporated in four cracked extended-compact tension specimens by application of different load based on the measured stress–strain curve. Fatigue crack growth behavior and fractured characteristic of the pre-stressed specimens were investigated systematically and were compared with those of an as-received specimen. The results show that the pre-stress ranged from 120 to 183 MPa significantly improved the fatigue resistance of Al-alloy by comparison with that of the as-received specimen. With increasing pre-stress, the fatigue life first increases, then decrease, and the specimen with pre-stress of 158 MPa has the longest fatigue life. For the manner of pre-stress, no adverse factor was observed for increasing fatigue property, and the induced pre-stress reduced gradually till to disappear during subsequent fatigue cycling.

Influence of Mean Load Pressure Fluctuations on Crack Growth Behavior in Steel Pipelines

2018 ◽  
Author(s):  
Olayinka Tehinse ◽  
Weixing Chen ◽  
Karina Chevil ◽  
Erwin Gamboa ◽  
Lyndon Lamborn
Keyword(s):  
Crack Growth ◽  
Pressure Fluctuations ◽  
Stress Sensitivity ◽  
Crack Growth Behavior ◽  
Mean Stress ◽  
Load Pressure ◽  
R Ratio ◽  
Stress Maximum ◽  
Minimum Stress ◽  
Pump Compressor

Internal pressure fluctuations during pipeline operations could contribute to crack growth in steel pipelines. These pressure fluctuations create a variable amplitude loading condition with large amplitude cycles at near-zero stress ratio, R (minimum stress / maximum stress) and small amplitude cycles (minor cycles) at near +1 R ratio which can both affect crack propagation. Mean stresses fluctuate with pressure due to fluid friction losses proportional to the distance from the pump/compressor station. A deeper understanding of mean stress sensitivity on crack growth rate in steel pipelines is sought. The aim of this research is to retard crack growth in pipelines by prescribing pressure fluctuations, thus controlling mean stress effects on imperfection growth in steel pipelines under a near neutral pH environment. This study shows that prescriptive mean load pressure fluctuations can be used to reduce crack growth rates in steel pipelines, thus expanding pipeline integrity management methods.

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.

scholarly journals IMPROVEMENT OF FATIGUE LIFE OF A HOLED SPECIMEN OF ALUMINUM-ALLOY 2024-T3 BY INDENTATION AND HOLE EXPANSION

2012 ◽  
Vol 06 ◽  
pp. 336-342 ◽  
Author(s):  
MD. SHAFIUL FERDOUS ◽  
CHOBIN MAKABE ◽  
TATSUJIRO MIYAZAKI ◽  
NOBUSUKE HATTORI
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Crack Growth ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Local Plastic ◽  
Aluminum Alloy 2024 ◽  
Pull Tests

A method of improving the fatigue life and crack growth behavior of a center holed specimen was investigated. Local plastic deformation was applied around the hole by indentation to achieve the purpose. A series of fatigue tests was conducted on aluminum-alloy 2024-T3. Push-pull tests were performed under a stress ratio of R= -1 and a frequency of 10Hz. The observations of the crack initiation and growth were performed with a microscope, and hardness around the hole was measured by Vickers hardness testing machine. In the present study, the longest fatigue life was observed in the case of an indentation specimen with the highest load. The indentation was performed on both sides of the hole edges. The crack growth rate was decreased by indentation or expansion of the material around the hole. From the experimental results, it is found that the fatigue life and crack growth behavior of a holed or notched specimen can be improved by a simple technical method that is related to the local plastic working.

Fatigue crack growth behavior of rib-to-deck double-sided welded joints of orthotropic steel decks

2020 ◽  
pp. 136943322096175
Author(s):  
Yang Liu ◽  
Fanghuai Chen ◽  
Da Wang ◽  
Naiwei Lu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Growth ◽  
Welded Joints ◽  
Mixed Mode ◽  
Fatigue Cracks ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Orthotropic Steel Decks

Innovative double-sided welding is expected to improve the fatigue resistance of rib-to-deck welded joints of orthotropic steel decks (OSDs). Welding crack-like defects are the crucial issue affecting the fatigue performance of rib-to-deck double-sided welded joints. This study presents a numerical simulation of three-dimensional (3D) mixed mode fatigue crack growth behavior of rib-to-deck double-sided welded joints of OSDs. Maximum tensile stress theory and equivalent stress intensity factor (SIF) were used to simulate mixed mode fatigue cracks growth. The Paris law model was employed to predict the fatigue life. Fatigue cracks of rib-to-deck double-sided welded joints were characterized by the presence of mixed mode cracks of modes I (open), mode II (shear), and mode III (tear), which was dominated by mode I. The equivalent SIF was found to be complex at the growth stage with the maximum value at the two ends of the crack front and the minimum value at the midpoint of the crack front. The crack shape became flatter in the later phase of the crack growth. The fatigue crack surface underwent deflections during crack growth, making the final crack shape exhibiting the characteristic of a spatial curved surface. The initial crack geometry showed a significant impact on the fatigue life.

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