Efficiently Predicting Fatigue Life of Drill Collars With Ports Subjected to Variable-Amplitude Bending or Torsional Loads

2019 ◽  
Author(s):  
Fei Song ◽  
Ke Li ◽  
Sepand Ossia
Keyword(s):  
Fatigue Life ◽  
Real Time ◽  
Elastic Stress ◽  
Time History ◽  
Remaining Useful Life ◽  
Dynamics Simulation ◽  
Cyclic Plasticity ◽  
Variable Amplitude ◽  
Torsional Loads ◽  
Stress States

Abstract To enable real-time monitoring of the physical condition of the drilling equipment such as drill collars, a methodology for efficiently predicting the fatigue life of ports subjected to variable-amplitude cyclic bending or torsional loads is needed. In this paper, such a method is reported, which involves several steps. Firstly, elastic finite element analysis (FEA) of a collar port was performed to determine the elastic stress states with unit loads. Secondly, the unit load-based linear elastic solutions with the loading history were superimposed to produce a time history of the stress tensor. Thirdly, the previously established pseudo-elastic stress states were transformed into the true elastoplastic stress and strain states with a cyclic plasticity model and a notch correction rule. Finally, the cumulative fatigue damage was computed with the rainflow counting algorithm and a damage accumulation rule. The resulting fatigue life predictions for the ports were found to agree favorably with the experimental measurements from full-scale fatigue tests of port-containing collar samples with variable-amplitude loads. This newly developed method can be used to predict the remaining useful life of a port in real time with the loads resulting from downhole measurements or a drill string dynamics simulation code.

Applicability of Equivalent Constant Amplitude Loading for Assessing the Fatigue Life of Pipelines and Risers and the Influence of Compressive Stress Cycles

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Mohammad Iranpour ◽  
Farid Taheri
Keyword(s):  
Experimental Investigation ◽  
Fatigue Life ◽  
Compressive Stress ◽  
Time History ◽  
Life Assessment ◽  
Constant Amplitude ◽  
Safety Factors ◽  
Variable Amplitude ◽  
Fatigue Life Assessment ◽  
Stress Cycles

Fatigue life assessment of pipelines and risers is a complex process, involving various uncertainties. The selection of an appropriate fatigue model is important for establishing the inspection intervals and maintenance criteria. In offshore structures, the vortex-induced vibration (VIV) could cause severe fatigue damage in risers and pipelines, resulting in leakage or even catastrophic failure. The industry has customarily used simple fatigue models for fatigue life assessment of pipelines and risers (such as the Paris or Walker models); however, these models were developed based on constant amplitude loading scenarios. In contrast, VIV-induced stress-time history has a variable amplitude nature. The use of the simplified approach (which is inherently non conservative), has necessitated the implementation of large safety factors for fatigue design of pipelines and risers. Moreover, most of the experimental investigations conducted to date with the aim of characterizing the fatigue response of pipelines and risers have been done based on incorporation of constant amplitude loading (CAL) scenarios (which is unrealistic), or converting the variable amplitude loading (VAL) scenarios to an equivalent CAL. This study demonstrates that the use of such approaches would not be lead to accurate assessment of the fatigue response of risers subject to VIV-induced VAL. The experimental investigation performed in this study will also clarify the underlying reasons for the use of large safety factors by the industry when assessing the fatigue life of pipelines and risers. In addition, an experimental investigation was also conducted to highlight the influence of the compressive portion of VIV stress-time history on the fatigue life of such components. It is shown that the compressive stress cycles significantly influence the fatigue crack growth response of risers, and their presence should not be ignored.

The Fatigue Life Simulation of the Wheel of CHR3 EMU in Random Loading

2012 ◽  
Vol 430-432 ◽  
pp. 1424-1427 ◽  
Author(s):  
Jian Wei Yang ◽  
Qi Long Shi ◽  
Guang Ye Zhang ◽  
Jiao Zhang
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Dynamic Loading ◽  
Time History ◽  
Fatigue Loading ◽  
Dynamics Simulation ◽  
Random Loading ◽  
Multi Body ◽  
To Receive ◽  
Dangerous Point

In order to calculate the EMU fatigue calculation of wheels, calculation of fatigue loading to obtain the wheel to solve problems, the method that makes use of multi-body dynamics simulation combined with finite element method is proposed, in time domain the wheel of CHR3 EMU in random loading is conducted the simulation study of the fatigue life. First of all, modal analysis of the wheels and wheel contact analysis are conducted in the ANSYS, and axle contact strength is also analyzed. Second, create a model of the EMU in ADAMS, and simulate to receive dynamic loading process. Finally, combined with the finite element stress method, dynamic loading time history and the linear cumulative damage rule, using ANSYS/WORKBENCH to get the fatigue life prediction chart of the wheel. It can be seen from the results, the safety factor of the most dangerous point of CRH3 EMU wheel type is 1.376, to meet fatigue life requirements, which provide a theoretical basis for the safety maintenance of the EMU.

scholarly journals A New Software Framework for Fatigue Life Prediction of Composite Materials under Irregular Loading

2006 ◽  
Vol 15 (1) ◽  
pp. 096369350601500 ◽  
Author(s):  
Anastasios P. Vassilopoulos
Keyword(s):  
Fatigue Life ◽  
Composite Materials ◽  
Life Prediction ◽  
Complex Stress ◽  
Fatigue Life Prediction ◽  
Software Framework ◽  
Material System ◽  
Variable Amplitude ◽  
Stress States ◽  
Irregular Loading

A new software framework for fatigue life prediction of composite materials under irregular loading is presented herein. The entire work is based on a well established methodology for the life prediction of GRP laminates under variable amplitude complex stress states. The process consists of the sequential execution of four main tasks, each one of which copes with a single subproblem in a straight forward manner. The aim of this on-going work is to create a generic software framework that will enable rapid prototyping of various life prediction schemes. Based on the software design, a software library is under development. In the current paper, the software framework is analytically presented. Two different modules are prepared for the first task of the entire methodology. Cycle counting of two different variable amplitude spectra is performed by rainflow counting technique and by simple range-mean technique. Results of both analyses are then processed by routines that solve subsequent steps of the entire methodology in order to predict time up to failure of the material system under consideration, a [0/(±45)2/0]T multidirectional laminate. Theoretical predictions are plotted against experimental data for comparison, and pros and cons of each one of the cycle counting algorithms are discussed.

An Experimental Investigation Into Fatigue Characterization of Oil Platform Risers Under Variable Amplitude Loading

2007 ◽  
Author(s):  
Mohammad Iranpour ◽  
Farid Taheri
Keyword(s):  
Fatigue Life ◽  
Time History ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Deep Waters ◽  
Fatigue Life Estimation ◽  
Induced Stresses ◽  
Offshore Industry ◽  
The Many

One of the many design challenges in offshore industry is the fatigue life estimation of risers due to the loading that is generated by vortex induced vibration (VIV). In deep waters, where the long risers are subjected to sever VIV-induced stresses and may encounter multi-modal vibration, the VIV-induced stresses could be the most significant contributor to the overall damage of the structure. The variable amplitude nature of the stress-time history often creates significant errors in the estimated fatigue life of the structure. The irregularities in the loading scenario could also create a considerable degree of plasticity at the crack tip, thus leading to. variability in material response. The uncertainties in the estimated fatigue damage under such a variable amplitude loading has resulted in the use of large safety factors by industry for establishing the fatigue life of the risers.

Low-Cycle Fatigue Performance of Buckling Restrained Braces and Assessment of Cumulative Damage under Severe Earthquakes

2018 ◽  
Vol 763 ◽  
pp. 867-874
Author(s):  
Yu Shu Liu ◽  
Ke Peng Chen ◽  
Guo Qiang Li ◽  
Fei Fei Sun
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Structural Reliability ◽  
Low Cycle Fatigue ◽  
Engineering Application ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Buckling Restrained Braces ◽  
Energy Dissipation Devices

Buckling Restrained Braces (BRBs) are effective energy dissipation devices. The key advantages of BRB are its comparable tensile and compressive behavior and stable energy dissipation capacity. In this paper, low-cycle fatigue performance of domestic BRBs is obtained based on collected experimental data under constant and variable amplitude loadings. The results show that the relationship between fatigue life and strain amplitude satisfies the Mason-Coffin equation. By adopting theory of structural reliability, this paper presents several allowable fatigue life curves with different confidential levels. Besides, Palmgren-Miner method was used for calculating BRB cumulative damages. An allowable damage factor with 95% confidential level is put forward for assessing damage under variable amplitude fatigue. In addition, this paper presents an empirical criterion with rain flow algorithm, which may be used to predict the fracture of BRBs under severe earthquakes and provide theory and method for their engineering application. Finally, the conclusions of the paper were vilified through precise yet conservative prediction of the fatigue failure of BRB.

scholarly journals Molecular dynamics simulation of sI methane hydrate under compression and tension

2020 ◽  
Vol 18 (1) ◽  
pp. 69-76
Author(s):  
Qiang Wang ◽  
Qizhong Tang ◽  
Sen Tian
Keyword(s):  
Molecular Dynamics ◽  
Methane Hydrate ◽  
Fracture Process ◽  
Md Simulation ◽  
Maximum Stress ◽  
Dynamics Simulation ◽  
Tensile Fracture ◽  
Maximum Compressive Stress ◽  
Motion State ◽  
Stress States

AbstractMolecular dynamics (MD) analysis of methane hydrate is important for the application of methane hydrate technology. This study investigated the microstructure changes of sI methane hydrate and the laws of stress–strain evolution under the condition of compression and tension by using MD simulation. This study further explored the mechanical property and stability of sI methane hydrate under different stress states. Results showed that tensile and compressive failures produced an obvious size effect under a certain condition. At low temperature and high pressure, most of the clathrate hydrate maintained a stable structure in the tensile fracture process, during which only a small amount of unstable methane broke the structure, thereby, presenting a free-motion state. The methane hydrate cracked when the system reached the maximum stress in the loading process, in which the maximum compressive stress is larger than the tensile stress under the same experimental condition. This study provides a basis for understanding the microscopic stress characteristics of methane hydrate.

scholarly journals Diagnostics and Prognostics of Energy Conversion Processes via Knowledge-Based Systems

Proceedings ◽  
2020 ◽  
Vol 58 (1) ◽  
pp. 1
Author(s):  
Roberto Melli ◽  
Enrico Sciubba
Keyword(s):  
Expert System ◽  
Knowledge Base ◽  
Real Time ◽  
System Analysis ◽  
Intelligent System ◽  
Time Derivative ◽  
Time History ◽  
Control Procedure ◽  
Time Data ◽  
Ongoing Research

This paper presents a critical and analytical description of an ongoing research program aimed at the implementation of an expert system capable of monitoring, through an Intelligent Health Control procedure, the instantaneous performance of a cogeneration plant. The expert system is implemented in the CLIPS environment and is denominated PROMISA as the acronym for Prognostic Module for Intelligent System Analysis. It generates, in real time and in a form directly useful to the plant manager, information on the existence and severity of faults, forecasts on the future time history of both detected and likely faults, and suggestions on how to control the problem. The expert procedure, working where and if necessary with the support of a process simulator, derives from the available real-time data a list of selected performance indicators for each plant component. For a set of faults, pre-defined with the help of the plant operator (Domain Expert), proper rules are defined in order to establish whether the component is working correctly; in several instances, since one single failure (symptom) can originate from more than one fault (cause), complex sets of rules expressing the combination of multiple indices have been introduced in the knowledge base as well. Creeping faults are detected by analyzing the trend of the variation of an indicator over a pre-assigned interval of time. Whenever the value of this ‘‘discrete time derivative’’ becomes ‘‘high’’ with respect to a specified limit value, a ‘‘latent creeping fault’’ condition is prognosticated. The expert system architecture is based on an object-oriented paradigm. The knowledge base (facts and rules) is clustered—the chunks of knowledge pertain to individual components. A graphic user interface (GUI) allows the user to interrogate PROMISA about its rules, procedures, classes and objects, and about its inference path. The paper also presents the results of some simulation tests.

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