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.

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.

Tensile and Fatigue Properties of Miniature Size Specimen of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge Lead-Free Solder

2018 ◽  
Vol 941 ◽  
pp. 2081-2086
Author(s):  
Masaki Yokoi ◽  
Tatsuya Kobayashi ◽  
Ikuo Shohji
Keyword(s):  
Tensile Strength ◽  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Ternary Eutectic ◽  
Lead Free ◽  
Fatigue Properties ◽  
Lead Free Solder ◽  
Cycle Fatigue ◽  
Proof Stress ◽  
Free Solder

Tensile and low cycle fatigue properties of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge (mass%) lead-free solder were investigated using miniature size specimens and obtained data were compared to those of Sn-3.0Ag-0.5Cu (mass%). The microstructure of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge consists of dendritic β-Sn phases and ternary eutectic phases surrounding them which are composed of β-Sn, (Cu,Ni)6Sn5 and Ag3Sn. Tensile strength and 0.1% proof stress of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge are superior to those of Sn-3.0Ag-0.5Cu at 25°C and 150°C. However, elongation of it is inferior to that of Sn-3.0Ag-0.5Cu at both temperatures. Fatigue lives of both alloys obey the Manson-Coffin equation and are analogous at 25°C. Although fatigue lives of both alloys decrease at 150°C, the fatigue life of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge is inferior to that of Sn-3.0Ag-0.5Cu. At 150°C, the crack mainly progresses at grain boundaries of recrystallized grains. Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge has several grain boundaies which can be the origin of the crack so that fatigue lives degrade at 150°C.

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.

Reliability Evaluation of Fatigue Life for Solder Joints in Chip Components Considering Dispersion of the Shape and the Properties

2011 ◽  
Author(s):  
Yuji Nishimura ◽  
Qiang Yu
Keyword(s):  
Fatigue Life ◽  
Material Properties ◽  
Solder Joints ◽  
Test Method ◽  
Fatigue Properties ◽  
Simulation Approach ◽  
Fiber Network ◽  
Heterogeneous Model ◽  
Isothermal Fatigue ◽  
Simulation Results

Recently, the downsizing of car components becomes a big trend for the development of car electronics, and it is becoming very difficult to achieve the reliability results target without managing controlling the dispersion of the fatigue lives. The authors proposed an isothermal fatigue test method using small size solder joints to get the fatigue properties. The Manson-Coffin’s law given by this method could improve the correspondence between the simulation results and experimental results. Based upon the Manson-Coffin’s law and Miner’s law, the authors proposed a fatigue crack propagation simulation approach. Furthermore, in order to consider the heterogeneity of PCB due to the distribution of fiber network, the authors made heterogeneous model considering the distribution of the fiber. And the authors evaluated the fatigue life of solder joints in chip components with considering dispersion of the material properties by using the heterogeneous model.

Cyclic Mechanical and Fatigue Properties for Oil-Country-Tubular-Goods Materials

SPE Journal ◽  
2008 ◽  
Vol 13 (04) ◽  
pp. 480-486 ◽  
Author(s):  
Trent M.V. Kaiser ◽  
Victor Y.B. Yung ◽  
Russ M. Bacon
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Material Properties ◽  
Low Cycle Fatigue ◽  
High Amplitude ◽  
Material Behavior ◽  
Fatigue Properties ◽  
Uniaxial Tensile ◽  
Engineering Models

Summary This paper describes differences between actual material behavior and idealizations used for modeling purposes and discusses some of the implications for interpreting model predictions. Much of the design for well structures subjected to high-amplitude cyclic loading is based on material assumptions that extrapolate strength properties from uniaxial, tensile tests to conditions where multiaxial, cyclic stresses are imposed. This paper presents results from cyclic testing on a common oil-country-tubular-goods (OCTG) material and demonstrates differences between the physical behavior measured under cyclic loading conditions and theoretical behavior extrapolated by numerical modeling. Modeling theories for plastic deformation are discussed with their limitations and relevance in a cyclic-loading environment. The implications of these limitations for design choices in thermal wells also are discussed with example applications of cyclic material behavior and fatigue-life prediction. Material fatigue properties for the high-amplitude, low-cycle application of thermal operations have not been investigated in much depth previously, particularly for OCTG. Along with characterizing cyclic mechanical properties, the tests discussed here also assessed the low-cycle fatigue properties of the sample OCTG steel. The consistent fatigue measurements, combined with analysis results using representative cyclic mechanical properties, can provide a basis for estimating fatigue life. Depending on analysis-model assumptions, substantial variation in predicted fatigue life can occur; therefore, exact fatigue-life predictions are not anticipated. The primary value in such modeling is in evaluating the relative effectiveness of mitigation options for extending well life. Introduction Most thermal enhanced-oil-recovery (EOR) wells in western Canada operate using either the cyclic-steam-stimulation (CSS) or the steam-assisted-gravity-drainage (SAGD) method. In both methods, operational factors result in thermal cycles being imposed on the well structures, particularly in the intermediate casing (Placido et al. 1997). Thermal expansion is constrained by the formation and cement in CSS and SAGD wells, producing loads that exceed the yield strength of the tubulars when the well is heated. Localization mechanisms also might amplify the strain magnitude, imposing additional plastic fatigue load at discrete locations along the well structure. Thermal-well casing designs have evolved during more than 30 years of operating experience, and much of the computer modeling that describes casing performance is based on measured uniaxial tensile material properties that are extrapolated to multidimensional cyclic behavior through engineering models. Cyclic material-properties data are sparse, particularly in the temperature regime common in thermal-recovery wells. Furthermore, plastic fatigue-life information for materials commonly used in well construction is difficult to obtain. Such information, however, is required to make reliable predictions of certain deformation mechanisms and the associated fatigue life for wells exposed to cyclic, thermally imposed loading. A test program for characterizing cyclic material properties was implemented to evaluate both cyclic mechanical properties and low-cycle fatigue life. Test-result consistency indicates a reliable material characterization that can be applied in constitutive analysis models and component-life assessments. The observed cyclic-stress-strain material behavior also demonstrates different characteristics from those predicted through engineering models using uniaxial monotonic material properties for input. This has important implications for thermal-well design and operations.

The Effect of Solid Particle Erosion on the Mechanical Properties and Fatigue Life of Fiber-Reinforced Composites

2006 ◽  
Author(s):  
N. H. Yang ◽  
H. Nayeb-Hashemi
Keyword(s):  
Tensile Strength ◽  
Fatigue Life ◽  
Solid Particle ◽  
Impact Angle ◽  
Fatigue Properties ◽  
Particle Impact ◽  
Solid Particle Erosion ◽  
Particle Erosion ◽  
Erosion Damage ◽  
Impact Angles

The effect of solid particle erosion on the strength and fatigue properties of E-glass/epoxy composite was investigated. Solid particle erosion with SiC particles of 400 μm to 500 μm in diameter was simulated on 12 ply [45°/-45°/0°/45°/-45°/0°]s E-glass/epoxy composites with a constant particle velocity of 42.5 m/s and solid particle to air volume ratio of 6 kg/m3 at impact angles of 90°, 60°, and 30° for 30, 60, 90 and 120 seconds. Damaged and undamaged specimens were subjected to tensile tests while monitoring their acoustic emission (AE) activity. An erosion damage parameter was defined as a function of the particle impact angle and erosion duration to determine the residual tensile strength of the composite. Scanning electron microscope (SEM) images of the erosion damaged specimens revealed the same damage mechanism occurred at different impact angles. The AE stress delay parameter was used to predict the residual tensile strength of erosion damaged composites. Tension-tension fatigue tests were performed on virgin specimens and specimens exposed to erosion damage of 60 seconds and 90 seconds at 90° particle impact angle to observe the effects of erosion damage on the fatigue life. A modified Basquin's equation was defined to predict the fatigue life of the erosion damaged specimens.

Study on Fatigue Properties of Copper Alloy Netting Structure

2019 ◽  
Vol 814 ◽  
pp. 275-282
Author(s):  
Shao Min Wang ◽  
Yu Qiu ◽  
Jie Jin Guo ◽  
Tai Ping Yuan ◽  
Hai Yang Liu
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Ultimate Strength ◽  
Copper Alloy ◽  
Failure Modes ◽  
Copper Wire ◽  
Great Influence ◽  
Fatigue Tests ◽  
Test Method ◽  
Fatigue Properties

Aiming at the damage and failure problem of copper alloy netting structure, the ultimate strength and fatigue performance of the net structure were studied by test method. Based on the research on the ultimate strength of copper wire, through a series of fatigue tests on copper wire and net structure, the fatigue life and failure modes of copper wire and net structure under different loads are analyzed, and their fatigue life curves are also drawn. The results show that the fatigue strength of copper wire and net structure considering corner processing is lower than that of copper wire not considering corner processing, which indicates that corner processing has a great influence on the fatigue strength of actual copper net structure. Compared with the fatigue strength value of 32.8 MPa of the copper net, the fatigue strength value of the net structure decreases to a certain extent (about 14.3%), which indicates that the assembly process of the copper net has certain influence on the fatigue life of the net structure.

scholarly journals Cracking failure of curved hollow tree trunks

2020 ◽  
Vol 7 (3) ◽  
pp. 200203
Author(s):  
Yan-San Huang ◽  
Pei-Lin Chiang ◽  
Ying-Chuan Kao ◽  
Fu-Lan Hsu ◽  
Jia-Yang Juang
Keyword(s):  
Tensile Strength ◽  
Material Properties ◽  
Tree Species ◽  
Orthotropic Material ◽  
Failure Modes ◽  
Tensile Force ◽  
Bending Moment ◽  
Initial Curvature ◽  
Bending Failure ◽  
Hollow Tree

Understanding the failure modes of curved hollow tree trunks is essential from both safety and conservation perspectives. Despite extensive research, the underlying mechanism that determines the cracking failure of curved hollow tree trunks remains unclear due to the lack of theoretical analysis that considers both the initial curvature and orthotropic material properties. Here we derive new mathematical expressions for predicting the bending moment, M crack , at which the cracking failure occurs. The failure mode of a tree species is then determined, as a function of t / R and cR , by comparing M crack with M bend , where t , R and c are, respectively, the trunk wall thickness, outer radius and initial curvature; M bend is the bending moment for conventional bending failure. Our equation shows that M crack is proportional to the tangential tensile strength of wood σ T , increases with t / R , and decreases with the final cR . We analyse 11 tree species and find that hardwoods are more likely to fail in conventional bending, whereas softwoods tend to break due to cracking. This is due to the softwoods' much smaller tangential tensile strength, as observed from the data of 66 hardwoods and 43 softwoods. For larger cR , cracking failure is easier to occur in curvature-decreasing bending than curvature-increasing due to additional normal tensile force F acting on the neutral cross-section; on the other hand, for smaller cR , bending failure is easier to occur due to decreased final curvature. Our formulae are applicable to other natural and man-made curved hollow beams with orthotropic material properties. Our findings provide insights for those managing trees in urban situations and those managing for conservation of hollow-dependent fauna in both urban and rural settings.

Porosity in Aluminum Alloy Castings

2019 ◽  
Author(s):  
Lenka Kuchariková ◽  
Eva Tillová ◽  
Juraj Belan ◽  
Milan Uhríčik
Keyword(s):  
Fatigue Life ◽  
Material Properties ◽  
Cast Alloy ◽  
Fatigue Behavior ◽  
Casting Process ◽  
Sand Mold ◽  
Fatigue Properties ◽  
Behavior Changes ◽  
Metallic Mold ◽  
Alloy Castings

The inclusions and impurities (such as oxides, carbide, defect, and so on) are formed mostly during the casting process. These inclusions and impurities reduce material properties because an increase in porosity has a tendency to form failure and corrosion of aluminum alloys. The effect of porosity on the fatigue life of AlSi9Cu3 cast alloy was studied, examining the effect of porosity size, distribution, and morphology on the fatigue behavior changes, using image analysis software. A comparison of the fatigue properties was made between material casted into a metallic mold and the material casted into a sand mold under the same conditions of gravity die casting. The fatigue properties were studied on equipment Vibrophores Amsler 50–250 HFP 5100 for material casted into a metallic mold and on Rotoflex for materials casted into a sand molds. The results show that porosity has the greatest detrimental effect on fatigue life. It was found that fatigue life decreases with increasing size of the pores surface. The experimental material casted into the metallic mold had about 98.78% smaller porosity size in comparison to the material casted into the sand mold; therefore, it showed better fatigue and mechanical properties.

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