Effects of proof loading test on fatigue life of mooring chain links

2019 ◽  
pp. 195-200
Author(s):  
X. Xue ◽  
N.-Z. Chen ◽  
Y.C. Pu
Keyword(s):  
Fatigue Life ◽  
Loading Test ◽  
Chain Links ◽  
Mooring Chain

FEA of Out-of-Plane Fatigue Mechanism of Chain Links

2005 ◽  
Author(s):  
Pedro Vargas ◽  
Philippe Jean
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Factor Of Safety ◽  
Finite Element Models ◽  
Chain Link ◽  
Out Of Plane ◽  
Bending Stresses ◽  
Chain Links ◽  
Mooring Chain ◽  
Loading Procedure

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 of 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. In this paper we identify a mechanism, here identified as Out-of-Plane Bending (OPB) that explains the extensive fatigue damage causing the mooring chains of the off-loading buoy to fail. A previous paper [4] presented experimental results of applying inter-link rotation to a pre-tensioned chain. Various pretension levels were used, with instrumentation to extract link angles and chain link stresses. In this paper, the physics of the OPB mechanism is examined through finite element models of the 124mm chain link tests. The various modes of interlink rotation are examined. The proof loading procedure that the chain undergoes at manufacture is identified as a likely cause for creating a tightly mated surface that is conducive to activating the OPB mechanism. To comply with Single Buoy Moorings (SBM) requirements addressing publication of internal research, many of the graphs included in this paper have had the stress values removed from the y-axis. However, with SBM’s management approval, some numerical references to stress amplitudes remain in the text. Overall, this limitation does not detract from the study, trends are evident and relevant comparisons can be made.

scholarly journals Adaptable legged-magnetic adhesion tracked wheel robotic platform for misaligned mooring chain climbing and inspection

2018 ◽  
Vol 45 (5) ◽  
pp. 634-646 ◽  
Author(s):  
Mahesh Dissanayake ◽  
Tariq Pervez Sattar ◽  
Shehan Lowe ◽  
Ivan Pinson ◽  
Tat-hean Gan
Keyword(s):  
Offshore Structures ◽  
Daily Basis ◽  
Robotic Platform ◽  
Destructive Testing ◽  
Content Type ◽  
Integrity Assessment ◽  
Human Operators ◽  
Chain Links ◽  
Mooring Chain ◽  
Magnetic Adhesion

Purpose Mooring chains used to stabilise offshore floating platforms are often subjected to harsh environmental conditions on a daily basis, i.e. high tidal waves, storms, etc. Therefore, the integrity assessment of chain links is vital, and regular inspection is mandatory for offshore structures. The development of chain climbing robots is still in its infancy due to the complicated climbing structure presented by mooring chains. The purpose of this paper is to establish an automated climbing technique for mooring chain inspection. Design/methodology/approach This paper presents a Cartesian legged tracked-wheel crawler robot developed for mooring chain inspection. The proposed robot addresses the misalignment condition of the mooring chains which is commonly evident in in situ conditions. Findings The mooring chain link misalignment is investigated mathematically and used as a design parameter for the proposed robot. The robot is validated with laboratory-based climbing experiments. Practical implications Chain breaking can lead to vessel drift and serious damage such as riser rupture, production shutdown and hydrocarbon release. Currently, structural health monitoring of chain links is conducted using either remotely operated vehicles which come at a high cost or by manual means which increase the danger to human operators. The robot can be used as a platform to convey equipment, i.e. tools for non-destructive testing/evaluation applications. Originality/value This study has upgraded a previously designed magnetic adhesion tracked-wheel mooring chain climbing robot to address the misalignment issues of operational mooring chains. As a result of this study, the idea of an orthogonally placed Cartesian legged-magnetic adhesion tracked wheel robotic platform which can eliminate concerns related to the misaligned mooring chain climbing has been established.

Experimental and numerical fatigue life assessment of SAC305 solders subjected to combined temperature and harmonic vibration loadings

2020 ◽  
Vol 32 (3) ◽  
pp. 181-187
Author(s):  
Mohammad Gharaibeh
Keyword(s):  
Fatigue Life ◽  
Compound Layer ◽  
Harmonic Vibration ◽  
Life Assessment ◽  
Lead Free ◽  
Intermetallic Compound Layer ◽  
Loading Test ◽  
Content Type ◽  
Vibration Loading ◽  
Lead Free Solders

Purpose This paper aims to investigate the fatigue life performance of SAC305 ball grid array solders under combined temperature and harmonic vibration loading conditions. Design/methodology/approach Fatigue tests were performed using a sine dwell with resonance tracking vibration and temperature loading experiment. Finite element stress analysis was also performed to help in understanding the observed failure trends. Findings Fatigue test results showed that the lead-free solders tend to fail quickly in higher temperatures and higher vibration loading test conditions. The failure analysis results revealed that in low temperatures, the solder cracks are initiated and propagated at the package side. However, in high temperatures, the cracks are observed at the board side of the interconnect. In all conditions, the cracks are propagated throughout the intermetallic compound layer. Originality/value In the published literature, there is a lack of data in the area of fatigue assessment of lead-free solders under combined temperature and vibration loadings. This paper provides useful insights into combined thermal/vibration fatigue, i.e. reliability behavior of lead-free solder joint types.

Fatigue Performance of High Strength and Large Diameter Mooring Chain in Seawater

2019 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Philip Smedley
Keyword(s):  
Large Diameter ◽  
High Strength ◽  
Crack Size ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Link Failures ◽  
Fatigue Design ◽  
Steel Grades ◽  
Chain Links ◽  
Mooring Chain

Abstract Fatigue design recommendations provided by API RP 2SK, ISO 19901-7 and DNVGL-OS-E301 for studless chain links are based on data of steel grades R3 and R4 and mainly of link diameter of 76mm. Mooring systems utilising larger diameter links and higher strength steels (e.g. grade R5) are now in operation. Consequently, industry expressed a need for fatigue test data in seawater of higher steel grade and larger diameter chain to confirm whether the existing fatigue design guidance is applicable. A joint industry project (JIP) was launched by TWI to investigate fatigue performance of high strength and large diameter mooring chain in free corrosion seawater. A test rig was designed and manufactured which was capable of testing studless mooring chain links up to 127mm link diameter under tension-tension loading. Twenty-three full-scale fatigue tests were conducted on high strength steel grades (R4 and R5) and larger diameter chains (76mm and 127mm) generating 72 link failures. Magnetic particle inspections (MPI) were carried out to characterise the location of cracking, crack size and crack growth rate. This paper describes the results obtained in the JIP.

Fracture mechanics analysis for mooring chain links subjected to out-of-plane bending (OPB)

2020 ◽  
Vol 71 ◽  
pp. 102740
Author(s):  
Xutian Xue ◽  
Nian-Zhong Chen ◽  
Yongchang Pu ◽  
Xifeng Gao
Keyword(s):  
Fracture Mechanics ◽  
Mechanics Analysis ◽  
Out Of Plane ◽  
Plane Bending ◽  
Chain Links ◽  
Mooring Chain

SCORCH JIP - Feedback on MIC and Pitting Corrosion from Field Recovered Mooring Chain Links

2014 ◽  
Author(s):  
Emmanuel Fontaine ◽  
Jeremy Rosen ◽  
Andrew Potts ◽  
Kai-Tung Ma ◽  
Robert Melchers
Keyword(s):  
Pitting Corrosion ◽  
Chain Links ◽  
Mooring Chain

Out-of-Plane Bending Testing of Chain Links

2005 ◽  
Author(s):  
Cecil Melis ◽  
Phillipe Jean ◽  
Pedro Vargas
Keyword(s):  
Empirical Relationship ◽  
Chain Link ◽  
Out Of Plane ◽  
Bending Stresses ◽  
Test Frame ◽  
Scale Test ◽  
Plane Bending ◽  
A Chain ◽  
Chain Links ◽  
Mooring Chain

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. In this paper we identify a mechanism, here identified as Out-of-Plane Bending (OPB) that explains the extensive fatigue damage causing the mooring chains of the off-loading buoy to fail. A full scale test frame was constructed that has the capacity of applying inter-link rotation to a pre-tensioned chain. Although the test frame limits the number of links that can be tested together as a chain, a significant amount of testing was performed for the following chain sizes: 1. 81 mm Studded Grade R3S. 2. 107 mm Studdless Grade RQ3. 3. 124 mm Studless Grade R4. 4. 146 mm Studless Grade RQ4. Various pretension levels were used, with instrumentation to extract link angles and chain link stresses. In this paper the OPB mechanism is explained, and the test frame and results are presented. An empirical relationship is found to predict the OPB stresses in the chain links as a function of pretension and inter-link rotation. The OPB stress relationship obtained was applied to the failed mooring chain of the off-loading buoy with reasonable agreement. To comply with Single Buoy Moorings (SBM) requirements addressing publication of internal research, many of the graphs included in this paper have had the stress values removed from the y-axis. However, with SBM’s management approval, some numerical references to stress amplitudes remain in the text. Overall, this limitation does not detract from the study, trends are evident and relevant comparisons can be made.

scholarly journals Analysis of fatigue test data of retrieved mooring chain links subject to pitting corrosion

2022 ◽  
Vol 81 ◽  
pp. 103119
Author(s):  
Jorge Mendoza ◽  
Per J. Haagensen ◽  
Jochen Köhler
Keyword(s):  
Fatigue Test ◽  
Test Data ◽  
Pitting Corrosion ◽  
Chain Links ◽  
Mooring Chain
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