Fatigue Behaviour of Dented Pipes Under Internal Pressure: A Numerical-Experimental Approach

2018 ◽  
Author(s):  
Mario A. Polanco-Loria ◽  
Håvar Ilstad
Keyword(s):  
Fatigue Life ◽  
Internal Pressure ◽  
Fatigue Behavior ◽  
Crack Depth ◽  
Fatigue Behaviour ◽  
Experimental Methodology ◽  
Experimental Program ◽  
Metal Loss ◽  
Life Predictions ◽  
Dent Depth

This work presents a numerical-experimental methodology to study the fatigue behavior of dented pipes under internal pressure. A full-scale experimental program on dented pipes containing gouges were achieved. Two types of defects were studied: metal loss (plain dent) and sharp notch. Both defects acting independently reduce the fatigue life performance but their combination is highly detrimental and must be avoided. We did not find a severity threshold (e.g. dent depth or crack depth) where these defects could coexist. In addition, based on numerical analyses we proposed a new expression for stress concentration factor (SCF) in line with transversal indentation. This information was successfully integrated into a simple fatigue model where the fatigue life predictions were practically inside the window of experimental results.

scholarly journals Multiaxial fatigue behavior of 2618 aluminum alloy

2019 ◽  
Vol 300 ◽  
pp. 09003
Author(s):  
Benaïssa Malek ◽  
Catherine Mabru ◽  
Michel Chaussumier
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Internal Pressure ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Mean Stress ◽  
Research Project ◽  
Pressure Tests

The purpose of the present research project is to study multiaxial fatigue behavior of 2618 alloy. The influence of mean stress on the fatigue behavior under tension and torsion is particularly investigated. Fatigue tests under combined tensile-torsion, in or out of phase, as well as combined tensile-torsion-internal pressure tests have also been conducted. Multiaxial fatigue results are analyzed according to Fatemi-Socie criterion to predict the fatigue life.

Predicting the Fatigue Life of Long Dents in Petroleum Pipelines

2002 ◽  
Author(s):  
Adam J. Rinehart ◽  
Peter B. Keating
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Contact Region ◽  
Laboratory Data ◽  
Prediction Method ◽  
Fatigue Cracking ◽  
Local Stress ◽  
Fatigue Damage Accumulation ◽  
Bending Stresses ◽  
Life Predictions

A full scale experimental study has demonstrated that long, unrestrained pipeline dents typically experience fatigue cracking in the dent contact region and have significantly shorter fatigue lives compared to other dent types studied. Furthermore, these dents often fully reround under normal pipeline operating pressures, making them difficult to reliably detect and assess using existing depth-based approaches. Several conditions unique to the dent contact region accelerate fatigue damage accumulation and are considered in a case-specific long dent fatigue life prediction method. First, the contact region develops significant bending stresses that contribute to a higher rate of fatigue crack growth. Second, history dependent, thru-thickness residual bending stresses that may have a significant influence on fatigue behavior are present in the contact region as a result of plastic deformation associated with dent formation and subsequent rebounding. A method for predicting the fatigue life of long dents that accounts for these factors is presented here and is used to analyze specific cases for which laboratory data is available. Nonlinear finite element modelling of the dent life cycle, including the indentation and rebounding phases, is used to determine local stress range behaviors and residual stress distributions. The application of appropriate fracture mechanics based models of fatigue is discussed and demonstrated. Fatigue life predictions are made on a case by case basis for situations studied in the laboratory so that the validity and accuracy of the approach presented here may be studied.

Fatigue behavior of graphene nanoplatelets reinforced and unreinforced basalt/epoxy composite pressure vessels subjected to low-velocity impact under internal pressure

2021 ◽  
pp. 002199832110370
Author(s):  
Harun Sepetcioglu ◽  
Necmettin Tarakcioglu
Keyword(s):  
Fatigue Life ◽  
Internal Pressure ◽  
Epoxy Composite ◽  
Fatigue Behavior ◽  
Pressure Vessels ◽  
Graphene Nanoplatelets ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Velocity Impact ◽  
The Impact

In this study, the fatigue behavior of 0.25 wt.% graphene nanoplatelets (GnPs) reinforced and unreinforced impact damaged basalt/epoxy composite pressure vessels (CPVs) was investigated. The CPVs were subjected to low-velocity impact (LVI) of 2.5 J, 5 J, 7.5 J, 10 J, 15 J, 20 J, and 25 J under internal pressure of 50 bar (hoop/axial prestresses: 98/49 MPa). Then, to detect fatigue life changes, fatigue tests were performed at load rates of 30% of ultimate hoop stress (σHS), where sweat damage occurred in the basalt/epoxy CPVs under alternating internal pressure. Considering the remaining fatigue life and formation of the damages in the CPVs for all impact energies, to investigate the fatigue behavior and GnPs effects of CPVs subjected to low-velocity impact, an impact value of 5 J was preferred. The 5 J impact damaged CPVs were subjected to fatigue cyclic following ASTM D 2992 at load rates of 20%, 25%, 30%, 35%, and 40% of the σHS. The fatigue life of damaged CPVs was compared by that of undamaged over S-N curves. As the impact energy increased, the impact damage area increased. The increased size of damage reduced the fatigue life of basalt/epoxy CPVs. At the fatigue load rates mentioned above, the GnPs improved the fatigue life of damaged basalt/epoxy CPVs by about 3.5, 3.2, 11.3, 2.4, and 5 times, respectively.

Measurement on Scale-Induced Fatigue Behaviour for Railway Axle

2008 ◽  
Vol 44-46 ◽  
pp. 65-70 ◽  
Author(s):  
Yong Xiang Zhao ◽  
Bing Yang ◽  
Ming Fei Feng
Keyword(s):  
Fatigue Life ◽  
Carbon Steel ◽  
Fatigue Limit ◽  
Fatigue Behavior ◽  
Fatigue Behaviour ◽  
Railway Axle ◽  
Material Fatigue ◽  
Lz50 Steel ◽  
The Difference

Transferring of fatigue behavior is investigated from material to structure for Chinese railway LZ50 axle carbon steel. S-N data in mid-fatigue life range and fatigue limit data of smooth small specimens are applied for material fatigue behavior. Real axles and similar smooth bigger specimens were tested with respect to fatigue limits. The data of real axles reveal the difference between material and a special structure. And the data of similar specimens play a role of bridge to connect material and material structures. Probabilistic transferring relations are deduced by the data from material, to similar specimens, and then to structures at the fatigue limit phase. Structural probabilistic S-N curves are obtained by the material fatigue behavior to extend the transferring relations to entire fatigue life range. Determinations of the fatigue behavior of the groove of LZ50 steel axle indicate availability of the present investigation.

Fatigue Life Estimates for a Notched Member in a Corrosive Environment

1987 ◽  
Vol 109 (1) ◽  
pp. 135-141 ◽  
Author(s):  
P. Kurath ◽  
Z. Khan ◽  
D. F. Socie
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Material Properties ◽  
Experimental Program ◽  
Nacl Solution ◽  
Linear Elastic ◽  
Cracked Plates ◽  
Fatigue Life Estimation ◽  
Mechanics Concepts ◽  
Life Predictions

It is often assumed that the effects of an aggressive environment can be included in fatigue life estimation procedures by determining the material properties in the environment and at the frequency of interest. An analytical and experimental program was conducted to confirm or refute this assumption. Automotive grade aluminum alloy, 5454-H32, in 3 percent NaCl solution and laboratory environment was selected for this study. A simple model where the total fatigue life is the summation of the portion where fatigue damage is best described by the notch strain field, and the portion where nominal stress and crack length dominate damage assessment, was used to estimate fatigue lives for center notched plates. Smooth cylindrical specimens were employed to determine the material properties for initiation. The environment had a large influence on the initiation resistance of this material at long fatigue lives, whereas at shorter fatigue lives (i.e., <104 cycles) there was little effect. Center cracked plates were used to determine the crack growth rates. Linear elastic fracture mechanics concepts were employed to estimate crack propagation lives. Approximately a factor of three reduction in crack propagation life was attributable to the hostile environment. Center notched plate specimens with Kt = 2.4 and Kt=5.1 were tested in both environments to examine the model. The accuracy of the fatigue life predictions in relation to the experimental data were comparable in 3 percent NaCl solution to the results obtained in laboratory air.

Fatigue Behavior of Line Pipes Subjected to Severe Mechanical Damage

1999 ◽  
Vol 121 (4) ◽  
pp. 369-374 ◽  
Author(s):  
N. Hagiwara ◽  
N. Oguchi
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Hoop Stress ◽  
Stress Amplitude ◽  
Fatigue Behavior ◽  
Mechanical Damage ◽  
Ductile Crack ◽  
Ductile Crack Growth ◽  
Power Law Equation ◽  
Dent Depth

Fatigue behavior of electrically resistance welded (ERW) line pipes with a gouge in a dent was experimentally investigated. After denting and machining a gouge, fluctuating internal pressure was applied to line pipes. The fatigue behavior differed above and below the threshold Q(Qth), as a function of defect size and fracture toughness. When Q < Qth, ductile crack growth was observed with a consequent decrease in fatigue life. On the contrary, fatigue crack growth was observed when Q ≧ Qth. Fatigue life was predictable with an experimentally based power law equation incorporating dent depth, gouge depth, and hoop stress amplitude when Q ≧ Qth.

Computational and experimental studies of the strength of full-scale samples of pipes with defects "metal loss" and "dent with groove"

2020 ◽  
Vol 10 (3) ◽  
pp. 226-233
Author(s):  
Dmitry A. Neganov ◽  
◽  
Victor M. Varshitsky ◽  
Andrey A. Belkin ◽  
◽  
...  
Keyword(s):  
Internal Pressure ◽  
Experimental Studies ◽  
Full Scale ◽  
The Other ◽  
Metal Loss ◽  
Calculation Methods ◽  
Reliable Operation ◽  
Sufficient Stability ◽  
Comparative Results ◽  
The Moment

The article contains the comparative results of the experimental and calculated research of the strength of a pipeline with such defects as “metal loss” and “dent with groove”. Two coils with diameter of 820 mm and the thickness of 9 mm of 19G steel were used for full-scale pipe sample production. One of the coils was intentionally damaged by machining, which resulted in “metal loss” defect, the other one was dented (by press machine) and got groove mark (by chisel). The testing of pipe samples was performed by applying static internal pressure to the moment of collapse. The calculation of deterioration pressure was carried out with the use of national and foreign methodical approaches. The calculated values of collapsing pressure for the pipe with loss of metal mainly coincided with the calculation experiment results based on Russian method and ASME B31G. In case of pipe with dent and groove the calculated value of collapsing pressure demonstrated greater coincidence with Russian method and to a lesser extent with API 579/ASME FFS-1. In whole, all calculation methods demonstrate sufficient stability of results, which provides reliable operation of pipelines with defects.

Factors Influencing the Fatigue Behavior of Ferrous Laminates

1987 ◽  
Vol 109 (3) ◽  
pp. 244-251 ◽  
Author(s):  
J. Wittenauer ◽  
O. D. Sherby
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Carbon Steel ◽  
Fatigue Behavior ◽  
Layered Material ◽  
Factors Influencing ◽  
Ultrahigh Carbon Steel ◽  
Processing History ◽  
Crack Blunting ◽  
Similar Processing

Laminates based on ultrahigh carbon steel were prepared and found to exhibit enhanced fatigue life as compared to a monolithic reference material. This result was achieved through the insertion of weak interlaminar regions of copper into the layered material during preparation of the laminates. The presence of these regions allowed for the operation of a delamination mechanism in advance of the propagating fatigue crack. The result was interlaminar separation and associated crack blunting. Stress-life curves show that an increase in life by as much as a factor of four is achieved for these materials when compared to monolithic specimens of similar processing history.

scholarly journals Influence of turning tool wear on the surface integrity and anti-fatigue behavior of Ti1023

2021 ◽  
Vol 13 (4) ◽  
pp. 168781402110112
Author(s):  
Li Xun ◽  
Wang Ziming ◽  
Yang Shenliang ◽  
Guo Zhiyuan ◽  
Zhou Yongxin ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Plastic Deformation ◽  
Titanium Alloy ◽  
Fatigue Life ◽  
Tool Wear ◽  
Surface Integrity ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Machined Surface ◽  
Deformation Layer

Titanium alloy Ti1023 is a typical difficult-to-cut material. Tool wear is easy to occur in machining Ti1023, which has a significant negative effect on surface integrity. Turning is one of the common methods to machine Ti1023 parts and machined surface integrity has a direct influence on the fatigue life of parts. To control surface integrity and improve anti-fatigue behavior of Ti1023 parts, it has an important significance to study the influence of tool wear on the surface integrity and fatigue life of Ti1023 in turning. Therefore, the effect of tool wear on the surface roughness, microhardness, residual stress, and plastic deformation layer of Ti1023 workpieces by turning and low-cycle fatigue tests were studied. Meanwhile, the influence mechanism of surface integrity on anti-fatigue behavior also was analyzed. The experimental results show that the change of surface roughness caused by worn tools has the most influence on anti-fatigue behavior when the tool wear VB is from 0.05 to 0.25 mm. On the other hand, the plastic deformation layer on the machined surface could properly improve the anti-fatigue behavior of specimens that were proved in the experiments. However, the higher surface roughness and significant surface defects on surface machined utilizing the worn tool with VB = 0.30 mm, which leads the anti-fatigue behavior of specimens to decrease sharply. Therefore, to ensure the anti-fatigue behavior of parts, the value of turning tool wear VB must be rigorously controlled under 0.30 mm during finishing machining of titanium alloy Ti1023.

scholarly journals Fatigue Modeling and Numerical Analysis of Re-Filling Probe Hole of Friction Stir Spot Welded Joints in Aluminum Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2171
Author(s):  
Armin Yousefi ◽  
Ahmad Serjouei ◽  
Reza Hedayati ◽  
Mahdi Bodaghi
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Element Model ◽  
Plastic Strain Amplitude ◽  
Friction Stir ◽  
Probe Hole ◽  
Good Agreement

In the present study, the fatigue behavior and tensile strength of A6061-T4 aluminum alloy, joined by friction stir spot welding (FSSW), are numerically investigated. The 3D finite element model (FEM) is used to analyze the FSSW joint by means of Abaqus software. The tensile strength is determined for FSSW joints with both a probe hole and a refilled probe hole. In order to calculate the fatigue life of FSSW joints, the hysteresis loop is first determined, and then the plastic strain amplitude is calculated. Finally, by using the Coffin-Manson equation, fatigue life is predicted. The results were verified against available experimental data from other literature, and a good agreement was observed between the FEM results and experimental data. The results showed that the joint’s tensile strength without a probe hole (refilled hole) is higher than the joint with a probe hole. Therefore, re-filling the probe hole is an effective method for structures jointed by FSSW subjected to a static load. The fatigue strength of the joint with a re-filled probe hole was nearly the same as the structure with a probe hole at low applied loads. Additionally, at a high applied load, the fatigue strength of joints with a refilled probe hole was slightly lower than the joint with a probe hole.

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