Oil Country Tubular Goods Fatigue Testing: Do We Test Them Enough?

2017 ◽  
Author(s):  
Catalin Teodoriu
Keyword(s):  
Fatigue Resistance ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Drill Pipe ◽  
High Stress ◽  
Economic Losses ◽  
Cycle Fatigue ◽  
Drill Pipes ◽  
Number Of Cycles

Fatigue is the most common known problem of drill pipes, since the combination of make-ups performed to connect the pipes and all the external loads, together with the threaded geometry of the connections, will stimulate the appearance of high stress points, cracks and finally promoting considerable economic losses. When threaded connections are used to connect the casing string, the fatigue resistance of the connection will affect the whole integrity of the string, and thus, in most cases, it is lower as the casing body. Generally, fatigue is classified as low-cycle fatigue and multi- or high-cycle fatigue. For Oil Country Tubular Goods (OCTG), a typical high cycle fatigue is represented by drill pipe fatigue in deviated wells. Unlike drill pipe, the casing may be exposed both to low-cycle as well as to high-cycle fatigue. Low-cycle fatigue is a common type of failure when the applied loads induce high stresses in the metallic material. The number of cycles may vary from as low as 10 up to 100. High-cycle fatigue requires a large number of cycles to failure. In order to avoid catastrophic failures, high-cycle fatigue resistance is usually considered to be sufficient if the number of cycles is above 106. The oil business has focused excessively on testing drilling risers and drill pipes under fatigue loads, but when it comes to casing and tubing the experimental approach may require different solutions. Drilling with casing opened the intensive testing of casing connections against fatigue resistance. Moreover, recent papers have shown intensive work on redesigning connections to withstand fatigue. New applications like rotating while running require a rethinking of testing strategy of Casing and Tubing. The following paper focuses on answering the question whether we test enough. The first part compares existing testing facilities, followed by an intensive discussion about the true loads of a casing or tubing connection. Using public testing data, the second part of the paper tries to identify how far the results provided by various types of testing machines can be compared with each other. For example, we found that low cycle fatigue results may not fully reflect the predictions based on extrapolations of high cycle fatigue results.

scholarly journals Fatigue Behavior of Linear Friction Welded Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-0.1Si Dissimilar Welds

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3136
Author(s):  
Sidharth Rajan ◽  
Priti Wanjara ◽  
Javad Gholipour ◽  
Abu Syed Kabir
Keyword(s):  
Titanium Alloys ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Aerospace Applications ◽  
Dissimilar Welds ◽  
Linear Friction ◽  
Number Of Cycles

The use of joints fabricated from dissimilar titanium alloys allows the design of structures with local properties tailored to different service requirements. To develop welded structures for aerospace applications, particularly under critical loading, an understanding of the fatigue behavior is crucial, but remains limited, especially for solid-state technologies such as linear friction welding (LFW). This paper presents the fatigue behavior of dissimilar titanium alloys, Ti–6Al–4V (Ti64) and Ti–6Al–2Sn–4Zr–2Mo–0.1Si (Ti6242), joined by LFW with the aim of characterizing the stress versus number of cycles to failure (S-N) curves in both the low- and high-cycle fatigue regimes. Prior to fatigue testing, metallurgical characterization of the dissimilar alloy welds indicated softening in the heat-affected zone due to the retention of metastable β, and the typical practice of stress relief annealing (SRA) for alleviating the residual stresses was effective also in transforming the metastable β to equilibrated levels of α + β phases and recovering the hardness. Thus, the dissimilar alloy joints were fatigue-tested in the SRA (750 °C for 2 h) condition and their low- and high-cycle fatigue behaviors were compared to those of the Ti64 and Ti6242 base metals (BMs). The low-cycle fatigue (LCF) behavior of the dissimilar Ti6242–Ti64 linear friction welds was characterized by relatively high maximum stress values (~ 900 to 1100 MPa) and, in the high-cycle fatigue (HCF) regime, the fatigue limit of 450 MPa at 107 cycles was just slightly higher than that of the Ti6242 BM (434 MPa) and the Ti64 BM (445 MPa). Fatigue failure of the dissimilar titanium alloy welds in the low-cycle and high-cycle regimes occurred, respectively, on the Ti64 and Ti6242 sides, roughly 3 ± 1 mm away from the weld center, and the transitioning was reasoned based on the microstructural characteristics of the BMs.

scholarly journals Fatigue life time modelling of Cu and Au fine wires

2018 ◽  
Vol 165 ◽  
pp. 06002
Author(s):  
Golta Khatibi ◽  
Ali Mazloum-Nejadari ◽  
Martin Lederer ◽  
Mitra Delshadmanesh ◽  
Bernhard Czerny
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Load Ratio ◽  
Life Time ◽  
Material Model ◽  
Cycle Fatigue ◽  
Rate Dependency

In this study, the influence of microstructure on the cyclic behaviour and lifetime of Cu and Au wires with diameters of 25μm in the low and high cycle fatigue regimes was investigated. Low cycle fatigue (LCF) tests were conducted with a load ratio of 0.1 and a strain rate of ~2e-4. An ultrasonic resonance fatigue testing system working at 20 kHz was used to obtain lifetime curves under symmetrical loading conditions up to very high cycle regime (VHCF). In order to obtain a total fatigue life model covering the low to high cycle regime of the thin wires by considering the effects of mean stress, a four parameter lifetime model is proposed. The effect of testing frequency on high cycle fatigue data of Cu is discussed based on analysis of strain rate dependency of the tensile properties with the help of the material model proposed by Johnson and Cook.

scholarly journals Effect of Hydrogen, Hydride Orientation and Temperature on Low-Cycle Fatigue Resistance of Zr-1%Nb Fuel Rod Claddings

2021 ◽  
pp. 53-59
Author(s):  
G. Riedkina ◽  
V. Grytsyna ◽  
S. Klymenko ◽  
Т. Chernyayeva
Keyword(s):  
Fatigue Life ◽  
Fatigue Resistance ◽  
Hydrogen Concentration ◽  
Hydrogen Content ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Outer Diameter ◽  
Cycle Fatigue ◽  
Fuel Rod ◽  
Hydride Reorientation

Low-cycle fatigue testing was conducted on annular samples with an outer diameter of 9.13 mm, a wall thickness of 0.68 mm and a width of 2.7 mm, namely: non-hydrogenated samples (cut out of standard Zr‑1%Nb cladding tubes); hydrogenated samples with a hydrogen concentration of 50 ... 400 ppm; samples cut out from hydrogenated dummy claddings after hydride reorientation tests performed according to various test modes. The tests were conducted at the temperatures of 25, 180, 350, 400 and 450 °С. The results obtained demonstrate that with increasing the hydrogen content in Zr-1%Nb alloy claddings the fatigue life increases.

High-Cycle Fatigue of Fan Blades Accounting for Fluid-Structure Interaction

2012 ◽  
Author(s):  
Priyanka Dhopade ◽  
Andrew J. Neely ◽  
John Young ◽  
Krishna Shankar
Keyword(s):  
Gas Turbines ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Experimental Studies ◽  
Peak Stress ◽  
Coupled System ◽  
Fatigue Analysis ◽  
Cycle Fatigue ◽  
Fully Coupled

Gas turbine engine components are subject to both low-cycle fatigue (LCF) and high-cycle fatigue (HCF) loads. To improve engine reliability, durability, and maintainability, it is necessary to understand the interaction of LCF and HCF in these components, which can adversely affect the overall life of the engine. The LCF loads result from the aircraft flight profile and are typically high stress, nominally rotational and aerodynamic loads. HCF loads are a consequence of high frequency vibrations, such as the fluctuating loads on blades as they rotate through the wakes from the upstream stator vanes. This paper demonstrates the importance of a fully coupled FSI analysis in conjunction with a fatigue analysis to predict the effect of representative fluctuating loads on the fatigue life of blisk fan blades. The fully-coupled FSI analysis is compared to the partially coupled FSI analysis and it is found that the former better predicts the the structural response of the titanium alloy blade to the wake impingement from the upstream stator. This results in a non-linear stress history compared to the linear response of the partially coupled system which also under-predicts the peak stress by 24%. The fatigue analysis shows the blade will fail near the root with a maximum damage of 1.079(10−17) using Miner’s rule to calculate cumulative damage. The implications of this research can influence future experimental studies that aim to generate meaningful fatigue data, which will assist in the management of safe operation of gas turbines.

Fatigue Characterization and Fractographic Analysis of Aluminium 6063 Alloy

2022 ◽  
pp. 176-194
Author(s):  
Sreearravind M. ◽  
Ramesh Kumar S. ◽  
Ahilan C.
Keyword(s):  
Cleavage Fracture ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Testing Machine ◽  
Fatigue Behaviour ◽  
Al Alloys ◽  
Cycle Fatigue ◽  
Specific Strength ◽  
Cyclic Plastic Strain ◽  
Number Of Cycles

Aluminium and its alloy are widely employed in various automobile and aircraft areas because of their unique specific strength and formability. Al alloys that have been employed in aerospace structural components will undergo dynamic loading, which leads to fatigue due to mechanical stress and thermal conditions. Considering studies toward the low cycle fatigue behaviour of Al alloys are significantly narrowed, this chapter sighted to the analysis of fatigue behaviour of Al 6063 alloy at the various total strain amplitude (TSA) of 0.4% and 0.8%, which performed through the low cycle fatigue testing machine at the frequency rate of 0.2 Hz. The test results show that for 0.4% TSA, the number of cycles to failure (N) is 1786, whereas as the TSA increases, N got reduced. For 0.8% TSA, the cycle to failure is 291 and samples undergone cyclic softening during the test. The rate of cyclic plastic strain raised up with the increase in the TSA. Crack propagation was observed along with the quasi-cleavage fracture for 0.4% TSA and cleavage fracture for 0.8% TSA.

scholarly journals Fatigue Characteristics of Selected Light Metal Alloys

2016 ◽  
Vol 61 (1) ◽  
pp. 271-274 ◽  
Author(s):  
M. Cieśla ◽  
G. Junak ◽  
A. Marek
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Light Metal ◽  
Fatigue Tests ◽  
The Other ◽  
Metal Alloys ◽  
Cycle Fatigue

The paper addresses results of fatigue testing of light metal alloys used in the automotive as well as aerospace and aviation industries, among others. The material subject to testing comprised hot-worked rods made of the AZ31 alloy, the Ti-6Al-4V two-phase titanium alloy and the 2017A (T451) aluminium alloy. Both low- and high-cycle fatigue tests were conducted at room temperature on the cycle asymmetry ratio of R=-1. The low-cycle fatigue tests were performed using the MTS-810 machine on two levels of total strain, i.e.Δεc= 1.0% and 1.2%. The high-cycle fatigue tests, on the other hand, were performed using a machine from VEB Werkstoffprufmaschinen-Leipzig under conditions of rotary bending. Based on the results thus obtained, one could develop fatigue life characteristics of the materials examined (expressed as the number of cycles until failure of sample Nf) as well as characteristics of cyclic material strain σa=f(N) under the conditions of low-cycle fatigue testing. The Ti-6Al-4V titanium alloy was found to be characterised by the highest value of fatigue life Nf, both in lowand high-cycle tests. The lowest fatigue life, on the other hand, was established for the aluminium alloys examined. Under the high-cycle fatigue tests, the life of the 2017A aluminium and the AZ31 magnesium alloy studied was determined by the value of stress amplitude σa. With the stress exceeding 150 MPa, it was the aluminium alloy which displayed higher fatigue life, whereas the magnesium alloy proved better on lower stress.

On the Use of Low and High Cycle Fatigue Damage Models

2013 ◽  
Vol 569-570 ◽  
pp. 1029-1035
Author(s):  
Magd Abdel Wahab ◽  
Irfan Hilmy ◽  
Reza Hojjati-Talemi
Keyword(s):  
Crack Initiation ◽  
Fatigue Damage ◽  
Damage Evolution ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Fretting Fatigue ◽  
Cycle Fatigue ◽  
Evolution Law ◽  
Number Of Cycles

In this paper, Continuum Damage Mechanics (CDM) theory is applied to low cycle and high cycle fatigue problems. Damage evolution laws are derived from thermodynamic principles and the fatigue number of cycles to crack initiation is expressed in terms of the range of applied stresses, triaxiality function and material constants termed as damage parameters. Low cycle fatigue damage evolution law is applied to adhesively bonded single lap joint. Damage parameters as function of stress are extracted from the fatigue tests and the damage model. High cycle fatigue damage model is applied to fretting fatigue test specimens and is integrated within a Finite Element Analysis (FEA) code in order to predict the number of cycles to crack initiation. Fretting fatigue problems involve two types of analyses; namely contact mechanics and damage/fracture mechanics. The high cycle fatigue damage evolution law takes into account the effect of different parameters such as contact geometry, axial stress, normal load and tangential load.

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