Fatigue Life Prediction of Cold Rolled Rotary Shouldered Threaded Connections

2018 ◽  
Author(s):  
Fei Song ◽  
Michael Du ◽  
Ke Li
Keyword(s):  
Fatigue Life ◽  
Cold Rolling ◽  
Fatigue Resistance ◽  
Element Model ◽  
Drill String ◽  
Directional Drilling ◽  
Drilling Tool ◽  
Threaded Connection ◽  
Threaded Connections ◽  
Cold Rolled

The bottom hole assembly (BHA) of a modern drill string for directional drilling mainly comprises a drill bit, a rotary steerable system, and a measurement while drilling tool. The tools and subs used on a BHA are screwed together through rotary shouldered threaded connections. Each connection is made up with a pin and a box. These connections are the weakest links when the BHA undergoes a large number of revolutions in a curved well section. When the fatigue life of a connection is consumed during a drilling job, a twist-off would occur, which could result in an enormous amount of non-productive time and possibly loss of the bottom BHA section in the hole. Cold rolling has proven to be able to improve fatigue resistance of a threaded connection by pressing a rolling wheel against the thread root and generating a layer of compressive residual stress at the root. Understanding how cold rolling improves fatigue resistance of a threaded connection is important for optimization of the rolling parameters and prediction of the BHA service life in a given drilling condition. In this paper, a predictive method is presented for fatigue life of a cold rolled threaded connection. A finite element model was developed to simulate the cold rolling process. The resulting deformation and stress states at the root were carried over through makeup of the pin and the box as well as through cyclic bending of the connection. The fatigue life predictions were found to be in favorable agreement with the experimental measurements from full-scale fatigue tests at different bending moment levels applied.

Evaluation of the Effect of Different Mean Stress Levels on the Fatigue Resistance of OCTG Premium Threaded Connections

2017 ◽  
Author(s):  
Yoshinori Ando ◽  
Yosuke Oku ◽  
Masaaki Sugino ◽  
Carol Johnston
Keyword(s):  
Fatigue Life ◽  
Primary Root ◽  
Initiation Site ◽  
Mean Stress ◽  
Standard Material ◽  
Root Cause ◽  
Threaded Connection ◽  
Threaded Connections ◽  
Stress Levels ◽  
Scale Test

Identification of the effect of mean stress for fatigue performance of the premium threaded connection for the OCTG pipes, was conducted via full-scale test. API standard material [grade L80-1] was used for the test. The nominal pipe outside diameter and wall thickness were 244.48 mm (9-5/8 inch) and 11.99 mm (0.472 inch), respectively. The fatigue life of the specimens tested with no mean stress was longer than that of the specimens tested with a tensile mean stress. Through-wall cracks were found at the imperfect thread area of the male embodiment, but the crack initiation site depended on the mean stress. However, the primary root cause of the failure on both mean stress levels can be regarded as the fretting fatigue. Fatigue life was also able to be estimated using modified Goodman relation.

Fatigue Assessment of Drill Pipes

2017 ◽  
Author(s):  
P. J. Haagensen ◽  
T. I. Grøttum
Keyword(s):  
Failure Modes ◽  
Fatigue Behavior ◽  
Drill String ◽  
American Petroleum Institute ◽  
Directional Drilling ◽  
Fatigue Wear ◽  
Threaded Connections ◽  
Current Design ◽  
Drilling Operations ◽  
Drill Pipes

Fatigue failures during offshore drilling operations is still a very costly problem. The fatigue behavior of drill pipes is reviewed, and typical failure modes are identified. The effects of drill string curvature during directional drilling on pipe body stress and on the fatigue life is examined. Effects on applied mean stress from drill string weight are discussed. Interaction effects of degradation mechanisms such as fatigue, wear and corrosion are evaluated. Experimental background data and statistical evaluation that form the basis for the current design practice issued by American Petroleum Institute (API) and other guidance in codes and standards is reviewed. Results from several recent testing programs performed under rotating bending of pipes with threaded connections, and tests involving the pipe body under resonance conditions are presented. The tests were made with pipe sizes from 2 7/8 in. to 5 7/8 in. in Grade S-135 pipes. The results are compared with published test data and design guidance such as API Recommended Practice G7 [1]. Recommendations are given for research and testing to improve reliability and the safe operation of drill strings.

Comparison of Two Axisymmetric Finite Element Models of Threaded Connections

1999 ◽  
Author(s):  
Mark Hommel
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Tensile Load ◽  
Bending Moment ◽  
Element Analysis ◽  
Axisymmetric Loading ◽  
Axisymmetric Model ◽  
Threaded Connection ◽  
Threaded Connections ◽  
Run Time

Abstract Predicting the fatigue life of threaded connections using finite element analysis generally requires a 2-D axisymmetric model capable of handling non-axisymmetric loading in order to simulate an applied bending moment. This is desirable from the standpoint of computer run time, as compared with the alternative approach, namely, developing a full 3-D model. Unfortunately, due to their esoteric nature, the 2-D axisymmetric elements with non-axisymmetric loading capability are not supported by the software vendors as well as the other elements, hence pre- and post-processing are more challenging. In addition, due to the Fourier representation of the non-axisymmetric load, computer run time and storage is increased significantly over that of a strictly 2-D axisymmetric model. In view of this, common practice has been to use instead the conventional axisymmetric model with an equivalent applied axial tensile stress equal to the mean bending stress through the wall thickness in order to simulate the bending moment and thereby avoid the necessity for non-axisymmetric loading. The question therefore arises as to how well the results from the strictly axisymmetric model agree with the results from the axisymmetric model with non-axisymmetric loading capability. The purpose of this paper is to compare the results of the two models. A 5-1/2 F.H. threaded connection is modeled by means of a commercial finite element code. First, the axisymmetric model with non-axisymmetric loading capability is treated and results are obtained. Second, the axisymmetric model with applied equivalent tensile load is examined and its results are compared with the former model. It is found that the value of the primary variable of interest for quantification of fatigue life, namely, alternating stress, agrees between the two models within 4%. Thus, it is concluded that the simplified model provides a viable alternative for modeling fatigue life of threaded connections.

Friction Considerations in Rotary Shouldered Threaded Connections

2007 ◽  
Author(s):  
Catalin Teodoriu ◽  
Herschel McDonald ◽  
Charles Bollfrass
Keyword(s):  
Drill Pipe ◽  
Extreme Environments ◽  
Drill String ◽  
Directional Drilling ◽  
Frictional Properties ◽  
Threaded Connections ◽  
Safety Margins ◽  
Drill Pipes ◽  
Drilling Conditions ◽  
First Time

The new connection designs introduced by the drill pipe manufacturers (double shoulder connections, intelligent drill pipes or any new design for increased torque resistance) make the use of the Farr formula for calculating proper assembly torque more problematic. Additionally, severe drilling conditions like HPHT, directional drilling and extreme environments are affecting critical thread compound performance properties, which can make it impossible to attain the optimum makeup torque for the connection. The new drilling conditions are exposing the drill string components to higher loads and consequently reduce the safety margins. Since the makeup process is the only way to control and achieve the maximum tool joint loading capacity, it becomes important to understand the effect of friction on optimum makeup torque calculation. This paper presents a modified equation for optimum makeup torque calculation by using the latest research on thread compound frictional properties. Also, the thread compound lubrication mechanism will be explained. For the first time the thread turn load will be related to the optimum makeup torque. The paper will also explain why there is a need for a new API standard for determining thread compound frictional properties. The formula developed herein, based on experimental results, demonstrates that the newly introduced overall factor may differentiate between used and new connections.

Multi-objective Optimisation of Torsion Beam Structure of Driverless Vehicle Chassis for Improved Fatigue Resistance

2021 ◽  
Vol 13 (4) ◽  
Author(s):  
Ligang Huang ◽  
Jing Wang
Keyword(s):  
Fatigue Life ◽  
Fatigue Resistance ◽  
Time History ◽  
Element Model ◽  
Kriging Model ◽  
Beam Structure ◽  
Torsion Beam ◽  
Baseline Design ◽  
Multi Objective ◽  
Torsion Stiffness

The fatigue resistance of the torsion beam is the keyway to prolong the service life of the chassis of the driverless vehicle. The rigid-flexible coupling finite element model of the chassis is constructed using anti-fatigue algorithm. In this model, the stress time history of the torsion beam is obtained by modal stress recovery. The nominal stress method is used to analyze the fatigue life of the structure. It is known that the structure weight affects the fatigue life, so the algorithm aims at lightening the structure to realize the improved fatigue resistance of the torsional beam structure. The parametric model of torsion beam is constructed with mass and fatigue life as optimization objectives, first-order torsion mode frequency and torsion stiffness as constraints. Multi-objective particle swarm optimization (MPSO) based on the Kriging model is used to achieve improved fatigue life of the torsion beam. After optimization, the structural weight of the torsion beam is reduced by 19.20%, and the light-weight and anti-fatigue effect are better than the baseline design.

scholarly journals Design characteristics that improve the fatigue life of threaded pipe connections

2011 ◽  
Vol 2 (2) ◽  
pp. 334-341
Author(s):  
Jeroen Van Wittenberghe ◽  
Patrick De Baets ◽  
Wim De Waele ◽  
Timothy Galle ◽  
Tien Thanh Bui ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Local Stress ◽  
Experimental Tests ◽  
Element Model ◽  
Stress Concentrations ◽  
Bending Fatigue ◽  
Four Point Bending ◽  
Threaded Connections ◽  
Linear Material ◽  
Design Characteristics

Threaded pipe connections are commonly used to connect risers, tendons, drill pipes and wellcasing strings. In these applications fatigue resistance plays an important role. A large variety of patenteddesign features exist, all claiming to improve the connection’s fatigue life. However, patent documents onlycontain claims and numerical or experimental data about these connection’s performance is generally notpublished. This makes it hard to make a quantitative comparison between different designs. In this study anoverview is given of fatigue resistant threaded connections. Two major methods to improve the fatigue lifeof a connection were identified. First of all, local stress concentrations can be reduced by optimizing thegeometry of the threads. Second the global shape of the connection can be optimized to obtain a moreuniform load distribution.Using a parametric finite element model, different designs were compared. The connections were modelledby a 2D axisymmetric geometry with non-linear material properties and elaborate contact conditions.Selected designs have been subjected to experimental tests in a four-point bending fatigue setup. Theexperimental tests serve as a validation for the results of the numerical simulations. It was found that themultiaxial stress distribution at the thread roots is the defining factor for the fatigue life of the connection.Nevertheless, these stresses can be changed by the global geometry of the connection. It can beconcluded that the fatigue life of threaded connections is determined by a combination of global and localaspects which should both be analysed for fatigue life calculations.

Predicting the Risk of Twist-Off for Rotary Shouldered Threaded Connections With a Statistical Approach

2019 ◽  
Author(s):  
Haitao Zhang ◽  
Ke Li
Keyword(s):  
Tensile Strength ◽  
Fatigue Life ◽  
Material Properties ◽  
Statistical Approach ◽  
Failure Modes ◽  
Drill String ◽  
Statistical Prediction ◽  
Fatigue Properties ◽  
Threaded Connections ◽  
Reduction In Area

Abstract Fatigue is one of the most frequently encountered failure modes of rotary shouldered connections (RSC) used in drill strings. Once initiated, a fatigue crack tends to grow and ultimately lead to a twist-off, which is catastrophic and often results in lengthy non-producing time and expensive fishing operations. The complexity of the fatigue mechanism, the variabilities of material properties, and the nonlinear contact interactions of the pin and the box elements of an RSC pose a substantial challenge to accurately predicting the fatigue life of the RSC. This would require considerable conservatism to be exercised to prevent a twist-off, which causes premature retirement of drilling assets. Using a statistical approach to predict the risk of twist-off (ROTO) of each RSC on the drill string could be a more economically viable solution as it would enable quantified risk assessment and scientifically calculated tradeoffs between performance, cost, and risk of failures. In this study, a methodology for statistical prediction of the ROTO of rotary shouldered threaded connections was developed. First, static material properties, including yield strength, tensile strength, elongation, and reduction in area, were extracted from a wealth of available material certificates. Feature engineering was carried out to arrive at two independent properties, tensile strength and reduction in area. Fatigue properties were then generated with the retrieved static material data and earlier established correlations between static and fatigue properties. Afterwards, elasto-plastic finite element analyses were performed on RSCs made of the same material but with different properties to determine critical fatigue indicators, stress and strain states as respective functions of the tensile strength. Finally, Monte-Carlo simulations were conducted with respect to statistical distributions of the two independent material variables to predict the ROTO as a function of fatigue life. The predictions were found to be favorable agreement with the available full-scale fatigue test data of an API connection type.

The Finite Element Analysis of the Rollers in a Rotary Steerable Drilling Tool

2013 ◽  
Vol 390 ◽  
pp. 641-645
Author(s):  
Guang Wei Zhang ◽  
Li You ◽  
Zhao Li
Keyword(s):  
Low Cost ◽  
Major Change ◽  
Drill String ◽  
Design Parameters ◽  
Directional Drilling ◽  
Element Analysis ◽  
Rotary Drilling ◽  
Drilling Tool ◽  
Thrust Bearings ◽  
Drilling Technology

Rotary steerable system (RSS) is a system complete the oriented features in real-time while a drill string rotary drilling. It is a major change since the 1990s in directional drilling technology. RSSs drilling frictional and torsional resistance is small, has a high drilling speed, low cost, the well trajectory is smooth and easy to control, it is considered to be the development direction of modern steering drilling technology .When the system working ,drilling pressure and torque are passed by the thrust bearings in the controlled bend sub oriented tool; therefore it is necessary to analysis the rollers load distribution to verify the design parameters of variation cardan shaft, thrust bearings and roller are correct or not, This article analyzed thrust bearings rollers by ANSYS. Determine its maximum stress, etc. Providing more intuitive and scientific basis for its structural optimization [1].

Fatigue life improvement of threaded connections by cold rolling

2005 ◽  
Vol 40 (2) ◽  
pp. 83-93 ◽  
Author(s):  
M. J Knight ◽  
F. P Brennan ◽  
W. D Dover
Keyword(s):  
Fatigue Life ◽  
Cold Rolling ◽  
Rolling Process ◽  
Fatigue Tests ◽  
Stress Concentrations ◽  
Threaded Connections ◽  
Industry Standards ◽  
Operational Lifetime ◽  
Life Improvement ◽  
As Stress

Failures in drillstring threaded connections continue to afflict the oil industry at a cost of millions of dollars per year. In an attempt to reduce these failures the industry has generally adopted the fatigue-life-enhancing technique of cold rolling the threaded connections which act as stress concentrations. However, this beneficial process is only specified as optional in the industry standards, and where it is performed there is very little detail provided about this important process. This paper describes full-scale fatigue tests that investigate the cold-rolling process. From the development of cold-rolling equipment and the gathering of fatigue experimental data, several key factors have been identified that influence the operational lifetime of drillstring threaded connections.

Sectionalized Mechanical Models of Drilling Tool of Trenchless Directional Drilling

2012 ◽  
Vol 268-270 ◽  
pp. 1190-1193
Author(s):  
Hui Xia ◽  
Yi Hua Dou ◽  
Xin He Wang ◽  
Jiang Wen Xu
Keyword(s):  
Axial Compression ◽  
Working Conditions ◽  
Mechanical Analysis ◽  
Drill String ◽  
Drill Bit ◽  
Straight Section ◽  
Directional Drilling ◽  
Drilling Tool ◽  
Horizontal Section ◽  
Axial Tension

There are three working conditions namely drilling a guide hole, expanding the guide hole and pulling back pipeline in trenchless directional drilling. The position of drill string in the wellbore and loads exerted on the drill string varied in different working conditions. The models of buckling analysis of drill strings under compression, mechanical analysis of drill string under axial compression near drill bit in inclined straight section, mechanical analysis of drill string with multi-centralizers under axial compression near drill bit in inclined straight section, mechanical analysis of drill string near drill bit under axial compression in horizontal section, mechanical analysis of drill string near drill bit under axial tension in horizontal section, mechanical analysis of drill strings near drill bit under axial tension in inclined straight section and mechanical analysis of drill string in failed well are established based on the characteristic of loads and trajectories in each section. The establishment of sectionalized mechanical model of drilling tool is the fundament of further study of force analysis, deformation analysis and stress analysis.

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