Effect of Reeling on Welded Umbilical Tubing Fatigue

2006 ◽  
Author(s):  
Jaime Buitrago ◽  
Krasimir Doynov ◽  
Allen Fox
Keyword(s):  
Plastic Strain ◽  
Fatigue Testing ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Experimental Program ◽  
Design Curve ◽  
Duplex Steel ◽  
Steel Tubing ◽  
Pressurized Fluids ◽  
Welding Procedure

One key component of umbilicals is the steel tubing carrying the pressurized fluids. During manufacturing and deployment of the umbilical, the tubing is subjected to a series of reeling and unreeling operations, resulting in a cumulative amount of plastic strain. For conventional design, this plastic strain is thought to limit the fatigue performance of the tubing, thereby limiting the number of such operations. This paper discusses an experimental program aimed at assessing the effect of the cumulative reeling strain on the fatigue life of girth-welded, super duplex steel tubing. In particular, the reeling simulation and fatigue testing equipment used are described and the experimental procedures are presented. Interpretation of fatigue tests indicate that (1) reeling degrades the fatigue performance of the welded tubing, (2) 75% of the B design curve may represent the 97.5% survival bound for tubing reeled up to 12% cumulative reeling strain, and (3) the fraction of the B design curve reduces to 40% for the same bound when the data from the 20% reeling strain tests are included. However, given the uncertainties involved, project-specific applications will require a fatigue qualification program for the specific tubing size, reeling history, and welding procedure at hand.

Effect of Reeling on Small Umbilical Tubing Fatigue

2008 ◽  
Author(s):  
Jaime Buitrago ◽  
Krassimir Doynov ◽  
Allen Fox
Keyword(s):  
Plastic Strain ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Experimental Methodology ◽  
Experimental Program ◽  
Duplex Steel ◽  
Fatigue Data ◽  
Steel Tubing ◽  
Current Design ◽  
Pressurized Fluids

Umbilicals use steel tubing of different sizes to carry various pressurized fluids. During manufacturing, transportation and installation of the umbilicals, the tubing is subjected to reeling and unreeling operations, resulting in a cumulative amount of plastic strain. The amount of strain varies with different cross-section designs and umbilical manufacturers. This plastic strain may limit the fatigue performance of the tubing in dynamic umbilicals, thereby limiting the number of reeling operations of umbilicals in deepwater. A previous paper presented a novel experimental methodology to simulate reeling and its effect on the fatigue of 57.6-mm ID × 3.4-mm WT made of super duplex steel. Results indicated that reeling can significantly degrade the fatigue performance of the welded tubing as the cumulative reeling strain increases up to 20%. This paper discusses an experimental program aimed at assessing the size effect on fatigue of reeled tubing. Ten 10 additional fatigue tests were conducted with 12.6-mm ID × 1.46-mm WT tubing reeled to 20% strain. Results indicate that the smaller tubing, once reeled to 20%, its fatigue performance degrades to the same level as that of the larger tubing. However, the combined fatigue data do not support current design criteria DnV-RP-C203. Therefore, given the uncertainty of all of the variables involved, fatigue qualification for specific applications is considered necessary.

Fatigue Performance of Thick Section Titanium Grade 29 Girth Welds

2020 ◽  
Author(s):  
Gabriel Rombado ◽  
David A. Baker ◽  
Lars M. Haldorsen ◽  
Kenneth Macdonald ◽  
Heath Walker ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Fatigue Testing ◽  
Fatigue Performance ◽  
Fluid Temperature ◽  
Design Curve ◽  
Fatigue Design ◽  
Dog Bone ◽  
Titanium Grade ◽  
Girth Welds ◽  
Welding Procedure

Abstract Design of Steel Catenary Risers (SCRs) requires the use of specialized connection hardware to mitigate the high dynamic bending moments at the hang-off location induced by host floater motion. Reliability of this connection hardware is imperative, especially in those applications involving high tension loads, high pressure and elevated fluid temperature. One option for connection hardware is a monolithic, metallic tapered stress joint. Because of its inherent density, strength, and stiffness properties, steel is not well suited for these applications due to excessive stress joint length and weight requirements. Titanium Grade 29 has been identified as an attractive material candidate for demanding service applications due to its unique mechanical properties including increased flexibility, excellent fatigue performance and corrosion resistance to sour fluids. This technology is well established in the offshore industry and utilized in over 60 SCR installations with operating lives exceeding 20 years of continuous subsea operation. Large titanium stress joints (TSJs) for deep-water applications are typically not fabricated as a single piece due to titanium ingot volume limitations thus making one or more intermediate girth weld(s) necessary to satisfy the overall length requirements. Fatigue testing of 38 mm (1.5-in) wall thickness girth welds, utilizing an optimized GTAW welding procedure to limit defect sizes to sub-millimeter, has previously been performed in seawater (OD exposure) under cathodic protection potentials and sour service (ID exposure) under galvanic potentials. Fatigue testing results fully verified the vendor S-N fatigue design curve, in addition, no appreciable differences in fatigue performance in environments were observed allowing project-specific testing to be limited to in-air testing. This paper presents in-air fatigue testing results of 51 mm (2.0-in) wall thickness Grade 29 girth welds, using the same optimized welding procedure, to assess thickness size effect on the vendor S-N fatigue design curve. Verification of the vendor fatigue design curve was demonstrated by testing curved dog-bone specimens, extracted longitudinally across the girth weld, with production level surface finishes on inner and outer surfaces in-air up to a predefined S-N fatigue target curve with 95% confidence level.

Fatigue Testing of Out-of-Plane Bending Mechanism of Chain Links

2006 ◽  
Author(s):  
Lucile Rampi ◽  
Pedro Vargas
Keyword(s):  
Fatigue Testing ◽  
Empirical Relationship ◽  
Fatigue Tests ◽  
Full Scale ◽  
Fatigue Performance ◽  
Special Focus ◽  
Out Of Plane ◽  
Plane Bending ◽  
Chain Links ◽  
Mooring Chain

Three years ago, several mooring chains of an off-loading buoy failed after only 8 months of service. These chains were designed according to conventional fatigue assessment using API RP 2SK T-N curves to a fatigue life or 20 years with a factor of safety equal to 3 on life. Of particular interest is that the mooring chain failure underwent significant mooring chain motions that caused interlink rotations. Although traditionally neglected, these interlink rotations, when combined with significant chain tensions can cause bending stresses in the chain links (See Figure 1). This recently identified phenomena, Out-of-Plane Bending (OPB), explains the extensive fatigue damage causing the mooring chains of the off-loading buoy to fail [3][4][5]. References [3] and [4] document full scale tests of the OPB mechanism using a full scale test frame with the ability of applying inter-link rotation to a pre-tensioned chain. This testing confirmed that interlink rotations with a constant tension load can result in significantly high stresses. OPB stresses were measured on four different chain sizes of various grades: 1) 81 mm Studded Grade R3S, 2) 107 mm Stud-less Grade RQ3, 3) 124 mm Stud-less Grade R4, and 4) 146 mm Stud-less Grade RQ4, Grade R3 in [3] and [4], but no actual fatigue tests were performed. References [3] and [5] document analytical and computational efforts to explain and quantify the OPB stresses. In this paper, special focus is placed on obtaining actual fatigue failures of chains from OPB loading. Smaller chain sizes (40 mm) are used to accommodate the load limits of the testing frame. To mimic the actual loading as close as possible, sub size models of actual chainhawses were used in the testing. Two chainhawses were used: 1) the chainhawse has internal curvature where a link rests on the intrados, similar to offloading buoy that failed in eight months, and 2) a straight chainhase, a design that is in use today with demonstrated improved fatigue performance over the curved chainhawse. OPB stresses are measured and reported. Fatigue loading in the OPB mode was applied for several configurations. The two chainhawse exhibit very different stress levels and fatigue performance. An empirical relationship previously reported in [3][4][5] is compared to the measured OPB stresses with mixed results. Although limited in number, the fatigue tests indicate that overall the chain fatigue performance is at or above the B1 DnV curve. The BS B1 curve is also compared.

Development of a Welding Sequence Optimized for the Fatigue Resistance of Tubular Joints With a Novel Representative Welded Sample

2018 ◽  
Author(s):  
Philippe Thibaux ◽  
Eric Van Pottelberg
Keyword(s):  
Fatigue Resistance ◽  
Fatigue Testing ◽  
Welding Process ◽  
Offshore Structures ◽  
Fatigue Tests ◽  
Complex Geometries ◽  
Tubular Joints ◽  
Welding Sequence ◽  
Welding Procedure ◽  
Welding Position

Tubular joints are complex geometries present in many offshore structures. Fatigue testing of tubular joints requires either downsizing of the dimensions of the joints or the use of a simplified geometry, to avoid prohibitive costs. For the development of a welding process optimized for the fatigue performance of tubular joints, one needs to use a representative sample: same material, same thickness, use of similar welding positions, same level of restraint as in a real structure, combined with the supplementary requirement of ease of manufacturing and testing. A novel geometry was developed to fulfil all these requirements. Then, different welds were produced using robot and manual welding in different positions. The fatigue tests proved to be very reproducible, and indicate a strong influence of the welding position on the fatigue resistance. For that reason, an optimized welding procedure and sequence was developed, in which the welds in the most fatigue sensitive locations are produced first in optimum condition, while the less sensitive parts are produced by subsequent welding in position.

Experimental Investigation of Compressive Overloads on Delamination Growth Behavior in Fatigued Composites

1999 ◽  
Author(s):  
Assimina A. Pelegri ◽  
Charles Valentine
Keyword(s):  
Fatigue Testing ◽  
Compressive Loading ◽  
Fatigue Tests ◽  
Growth Behavior ◽  
Experimental Program ◽  
Laminate Composites ◽  
Variable Amplitude ◽  
Delamination Growth ◽  
Aerospace Applications ◽  
Compressive Loads

Abstract The behavior of laminated graphite/epoxy composites under variable amplitude compressive loading is studied. Laminate composites in aerospace applications undergo both compressive and tensile fatigue stresses as well as spectrum loading. These materials are particularly susceptible to compressive loads and overloads, which cause the growth of any small pre-existing delaminations. Such delamination growth, and the resulting sublaminate buckling, are major causes of fatigue failure. This experimental program investigates the effects of overloads on laminate composite specimens in which small delaminations are introduced during fabrication. The delamination growth is monitored in real time during fatigue tests. Different variable amplitude load spectra are applied, and the delamination position through the depth of the specimens is varied. Up to now, research has focused on constant amplitude fatigue testing or simple two block testing. Some variable amplitude studies have been done but attention has mostly been given to the reduction in residual strength or stiffness of the specimen. Much of the prior work is done in tension instead of compression. This investigation will provide data specifically on the growth behavior of pre-existing delaminations in composites under compressive overloads.

Best Practice Guidance for Evaluating Knock-Down Factors in Corrosive Environments

2012 ◽  
Author(s):  
Colum M. Holtam ◽  
Charles R. A. Schneider ◽  
Graham Slater
Keyword(s):  
Corrosion Fatigue ◽  
Best Practice ◽  
Fatigue Tests ◽  
Reduction Factor ◽  
Fatigue Performance ◽  
Corrosive Environment ◽  
Design Curve ◽  
Knock Down ◽  
Girth Welding ◽  
Girth Welds

The term knock-down factor is commonly used to describe the reduction in fatigue life in a corrosive environment (e.g. sour service) compared to performance in air. However, the mere concept of such a reduction factor is potentially misleading, particularly when comparing different welding procedures that demonstrate different in-air performance. This paper examines the concept and calculation of so-called knockdown factors. To demonstrate the performance of girth welds in a corrosive environment, strip fatigue tests are conducted in air and in a simulated service environment, to determine an appropriate knock-down factor, which is then applied to the base design curve. However, there are a number of ways that such knock-down factors can be calculated, with different degrees of conservatism. For example, two different welding procedures may exhibit a different fatigue performance in air, but a similar performance when tested in a sour environment. The better performing weld (in air) is therefore assigned a greater knock-down factor, and possibly a more stringent sour design curve. In other instances, fatigue performance in air may significantly exceed that required. The determined knock-down factor, between strip tests in air and in a sour environment, can then be very large. Applying this reduction factor to the design curve results in a very stringent sour design curve, and may penalize the use of a girth welding procedure that results in good in-air fatigue performance. There are no explicit, published guidelines for calculating corrosion fatigue knock-down factors. This paper describes an approach, based on experience and considering best practice guidance for the statistical analysis of fatigue data obtained from welded joints. The method is demonstrated using published sour corrosion fatigue endurance data, evaluating both mean and design curves.

scholarly journals Experimental study on fatigue performance of Q420qD high-performance steel cross joint in complex environment

2021 ◽  
Author(s):  
Haigen Cheng ◽  
Cong Hu ◽  
Yong Jiang
Keyword(s):  
Fatigue Life ◽  
High Performance ◽  
Steel Structure ◽  
Steel Structures ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Corrosive Media ◽  
Joint Connection ◽  
High Performance Steel ◽  
The Cross

AbstractThe steel structure under the action of alternating load for a long time is prone to fatigue failure and affects the safety of the engineering structure. For steel structures in complex environments such as corrosive media and fires, the remaining fatigue life is more difficult to predict theoretically. To this end, the article carried out fatigue tests on Q420qD high-performance steel cross joints under three different working conditions, established a 95% survival rate $$S{ - }N$$ S - N curves, and analyzed the effects of corrosive media and high fire temperatures on its fatigue performance. And refer to the current specifications to evaluate its fatigue performance. The results show that the fatigue performance of the cross joint connection is reduced under the influence of corrosive medium, and the fatigue performance of the cross joint connection is improved under the high temperature of fire. When the number of cycles is more than 200,000 times, the design curves of EN code, GBJ code, and GB code can better predict the fatigue life of cross joints without treatment, only corrosion treatment, and corrosion and fire treatment, and all have sufficient safety reserve.

scholarly journals Fatigue Testing of Wearable Sensing Technologies: Issues and Opportunities

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4070
Author(s):  
Andrea Karen Persons ◽  
John E. Ball ◽  
Charles Freeman ◽  
David M. Macias ◽  
Chartrisa LaShan Simpson ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Prediction Models ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Wearable Sensors ◽  
Fatigue Tests ◽  
Proof Of Concept ◽  
Cycle Fatigue ◽  
Wearable Sensing ◽  
Failure Data

Standards for the fatigue testing of wearable sensing technologies are lacking. The majority of published fatigue tests for wearable sensors are performed on proof-of-concept stretch sensors fabricated from a variety of materials. Due to their flexibility and stretchability, polymers are often used in the fabrication of wearable sensors. Other materials, including textiles, carbon nanotubes, graphene, and conductive metals or inks, may be used in conjunction with polymers to fabricate wearable sensors. Depending on the combination of the materials used, the fatigue behaviors of wearable sensors can vary. Additionally, fatigue testing methodologies for the sensors also vary, with most tests focusing only on the low-cycle fatigue (LCF) regime, and few sensors are cycled until failure or runout are achieved. Fatigue life predictions of wearable sensors are also lacking. These issues make direct comparisons of wearable sensors difficult. To facilitate direct comparisons of wearable sensors and to move proof-of-concept sensors from “bench to bedside,” fatigue testing standards should be established. Further, both high-cycle fatigue (HCF) and failure data are needed to determine the appropriateness in the use, modification, development, and validation of fatigue life prediction models and to further the understanding of how cracks initiate and propagate in wearable sensing technologies.

scholarly journals Experimental Design and Validation of an Accelerated Random Vibration Fatigue Testing Methodology

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Yu Jiang ◽  
Gun Jin Yun ◽  
Li Zhao ◽  
Junyong Tao
Keyword(s):  
Fatigue Life ◽  
Stress Responses ◽  
Life Prediction ◽  
Random Vibration ◽  
Fatigue Testing ◽  
Fatigue Tests ◽  
Fatigue Life Prediction ◽  
Power Spectral ◽  
Vibration Fatigue ◽  
Non Gaussian

Novel accelerated random vibration fatigue test methodology and strategy are proposed, which can generate a design of the experimental test plan significantly reducing the test time and the sample size. Based on theoretical analysis and fatigue damage model, several groups of random vibration fatigue tests were designed and conducted with the aim of investigating effects of both Gaussian and non-Gaussian random excitation on the vibration fatigue. First, stress responses at a weak point of a notched specimen structure were measured under different base random excitations. According to the measured stress responses, the structural fatigue lives corresponding to the different vibrational excitations were predicted by using the WAFO simulation technique. Second, a couple of destructive vibration fatigue tests were carried out to validate the accuracy of the WAFO fatigue life prediction method. After applying the proposed experimental and numerical simulation methods, various factors that affect the vibration fatigue life of structures were systematically studied, including root mean squares of acceleration, power spectral density, power spectral bandwidth, and kurtosis. The feasibility of WAFO for non-Gaussian vibration fatigue life prediction and the use of non-Gaussian vibration excitation for accelerated fatigue testing were experimentally verified.

Gigacycle Fatigue of Welded Joints of Structural Materials (A Review)

2016 ◽  
Vol 17 ◽  
pp. 14-30 ◽  
Author(s):  
Okechukwu P. Nwachukwu ◽  
Alexander V. Gridasov ◽  
Ekaterina A. Gridasova
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Testing Machine ◽  
Structural Materials ◽  
Fatigue Tests ◽  
Material Defects ◽  
Graphite Cast Iron ◽  
Ultrasonic Fatigue ◽  
Materials Used ◽  
Fatigue Failures

This review looks into the state of gigacycle fatigue behavior of some structural materials used in engineering works. Particular attention is given to the use of ultrasonic fatigue testing machine (USF-2000) due to its important role in conducting gigacycle fatigue tests. Gigacycle fatigue behavior of most materials used for very long life engineering applications is reviewed.Gigacycle fatigue behavior of magnesium alloys, aluminum alloys, titanium alloys, spheroid graphite cast iron, steels and nickel alloys are reviewed together with the examination of the most common material defects that initiate gigacycle fatigue failures in these materials. In addition, the stage-by-stage fatigue crack developments in the gigacycle regime are reviewed. This review is concluded by suggesting the directions for future works in gigacycle fatigue.

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