scholarly journals Special Issue on Fracture and Fatigue Assessments of Structural Components

2020 ◽  
Vol 10 (18) ◽  
pp. 6327
Author(s):  
Alberto Campagnolo
Keyword(s):  
Fatigue Life ◽  
Structural Integrity ◽  
Fatigue Loading ◽  
Complex Geometries ◽  
Loading Conditions ◽  
Structural Elements ◽  
Structural Components ◽  
Special Issue ◽  
Linear Elastic ◽  
Life Predictions

This Special Issue covers the broad topic of structural integrity of components subjected to either static or fatigue loading conditions, and it is concerned with the modelling, assessment and reliability of components of any scale. Dealing with fracture and fatigue assessments of structural elements, different approaches are available in the literature. They are usually divided into three subgroups: stress-based, strain-based and energy-based criteria. Typical applications include materials exhibiting either linear-elastic or elasto-plastic behaviours, and plain and notched or cracked components subjected to static or cyclic loading conditions. In particular, the articles contained in this issue concentrate on the mechanics of fracture and fatigue in relation to structural elements from nano- to full-scale and on the applications of advanced approaches for fracture and fatigue life predictions under complex geometries or loading conditions.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

Optimized Operations and Integrity Management Through Instrumentation

2012 ◽  
Author(s):  
Peter Jenkins ◽  
Trond Pytte ◽  
Harald Holden ◽  
Ignacio Marre ◽  
Jo Espen Rønningen ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Wave Height ◽  
Oil Recovery ◽  
Structural Integrity ◽  
Weather Forecasting ◽  
Fatigue Loading ◽  
Subjective Assessment ◽  
Oil Companies ◽  
The North ◽  
Operating Limits

During drilling and well intervention (DWI) operations today operating limits are normally given as limiting wave height, and sometimes wave periods. The resulting diagrams are often not directly comparable with weather information received on the rig and the final decisions are often based on subjective assessment of wave height and period. The paper will present how BP, on the newly developed Skarv field in the Norwegian Sea, through thorough planning in the engineering phase has implemented a system where operating limits are specified based on directly measurable parameters such as rig heave and upper and lower flexjoint angles. How weather forecasting can be translated to give the rig crew direct forecasting of the limiting vessel or riser responses (e.g. flexjoint angles or heave), will also be presented. It will be shown how this allows for improved operational planning and support from onshore. Over the last years requirements for oil companies to be able to document the structural integrity of their subsea assets, including wells, has increased. On the Norwegian Continental Shelf (NCS) there has been a particular focus on fatigue loading in the wellhead structure, including the upper sections of casing and conductor, due to loads induced by the riser and BOP during DWI operations. There have been cases where the design fatigue life of a wellhead system limits the number of days one can perform operations with a rig on a given well. This in term affects future oil recovery rates as the well fatigue life may not be sufficient to allow for side step drilling or intervention work required to maintain an optimal production from the well. The paper continues to present how BP on the Skarv field, stores and utilizes the measured lower flexjoint response to track and document well integrity. It will be demonstrated how the return on investment of a drilled well can be improved by documenting actual fatigue loading from each operation on a well compared to conservative design calculations. BP has addressed the above issues in a way that is likely to set a new standard for drilling and intervention operations in the North Sea in the future. 4Subsea AS has provided the engineering and instrumentation services that formed the basis for this paper.

Probabilistic Analysis of the Fatigue Life of Offshore Wind Turbine Structures

2020 ◽  
Author(s):  
Abraham Nispel ◽  
Stephen Ekwaro-Osire ◽  
João Paolo Dias
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Structural Reliability ◽  
Research Question ◽  
Limit State ◽  
Fatigue Loading ◽  
Offshore Wind ◽  
Design Parameters ◽  
Offshore Wind Turbine ◽  
Loading Conditions

Abstract The structural response of the main components of offshore wind turbines (OWTs) is considerably sensitive to amplification as their excitation frequencies approach the natural frequency of the structure. Furthermore, uncertainties present in the loading conditions, soil and structural properties highly influence the dynamic response of the OWT. In most cases, the cost of the structure reaches around 30% of the entire OWT because conservative design approaches are employed to ensure its reliability. As a result, this study aims to address the following research question: can the structural reliability of OWT under fatigue loading conditions be predicted more consistently? The specific aims are to (1) establish the design parameters that most impact the fatigue life, (2) determine the probability distributions of the design parameters, and (3) predict the structural reliability. An analytical model to determine the fatigue life of the structure under 15 different loading conditions and two different locations were developed. Global sensitivity analysis was used to establish the more important design parameters. Also, a systematic uncertainty quantification (UQ) scheme was employed to model the uncertainties of model input parameters based on their available information. Finally, the framework used reliability analysis to consistently determine the system probability of failure of the structure based on the fatigue limit state design criterion. The results show high sensitivity for parameters usually considered as deterministic values in design standards. Additionally, it is shown that applying systematic UQ produces a better approximation of the fatigue life under uncertainty and more accurate estimations of the structural reliability. Consequently, more reliable and robust structural designs may be achieved without the need for overestimating the offshore wind turbine response.

Investigation on Fatigue Life Prediction of Riveted Cantilever Beam Using FEA Approach

2021 ◽  
Author(s):  
Yemineni Siva Sankara Rao ◽  
Kutchibotla Mallikarjuna Rao ◽  
V. V. Subba Rao
Keyword(s):  
Fatigue Life ◽  
Loading Condition ◽  
Technological Development ◽  
Fatigue Loading ◽  
Cantilever Beams ◽  
Structural Elements ◽  
Variable Loading ◽  
Variable Parameters ◽  
Aircraft Wings ◽  
Reversed Cyclic

Abstract Different structural elements of automobiles, ships, aircraft wings and fuselages, turbines, nuclear reactors, and other machine components are susceptible to variable loading condition. Due to this type of loading situation all the mentioned structures are undergone to the formation of internal cracks, these cracks will be grown and eventually lead to the failure of the structures. Hence, the fatigue phenomenon due to variable loading conditions is a major threat and has come into address with the technological development that happening is now a days. To avoid the failure of structures due to fatigue loading condition structures are provided with different fasteners like rivets, bolts, tack welds, etc. In this study, the structures analyzed are cantilever beams, the fasteners considered are rivets, the loading considered for analysis is fully reversed cyclic loading, and the analysis considered is the fatigue analysis, the mode of analysis is a simulation using FEA software named ANSYS R19.2 WORKBENCH software. The variable parameters considered are rivet diameter, load, and coefficient of friction at the common interface of riveted specimens. Here in this analysis, the beam dimensions are kept constant. Besides, in this study, the comparison of fatigue life for solid and riveted cantilever beams of identical dimensions is presented. The material considered for the rivets and beams is aluminum alloy.

Fatigue Life Calculation in Conditions of Wide Spectrum Random Loadings – The Experimental Verification of a Calculation Algorithm on the Example of 41Cr4 Steel

2012 ◽  
Vol 726 ◽  
pp. 17-26
Author(s):  
Bogdan Ligaj ◽  
Grzegorz Szala
Keyword(s):  
Fatigue Life ◽  
Wide Spectrum ◽  
Loading Conditions ◽  
Test Results ◽  
Structural Elements ◽  
Random Loading ◽  
Calculation Algorithm ◽  
Fatigue Characteristic ◽  
Life Tests ◽  
Fatigue Characteristics

Precision of fatigue life calculations of structural elements in programmed loading conditions is connected with proper elaboration of loading spectrum and assumption of a proper fatigue characteristic. On the base of literature data and own research there has been elaborated an algorithm for fatigue life calculations in random loading conditions with wide spectrum. Calculations were performed with the usage of chosen mathematical models of two-parametric fatigue characteristics. Results calculated with accordance to the described procedure were validated with experimental test results of specimens made of 41Cr4 steel with a method of programmed fatigue life tests.

Bend Stiffener Design for Umbilicals

2011 ◽  
Author(s):  
Nils So̸dahl ◽  
Torfinn Ottesen
Keyword(s):  
Structural Integrity ◽  
Fatigue Loading ◽  
General Description ◽  
Loading Conditions ◽  
Optimization Scheme ◽  
Capacity Curve ◽  
Relative Angle ◽  
Compliant Structure ◽  
Extreme Load ◽  
Design Loads

A crucial design issue for compliant risers and umbilicals for dynamic applications is termination of the compliant structure to a rigid structure. A practical way to solve this problem is to introduce a properly designed bend stiffener to limit the stresses in the compliant structure due to bending at the supports. The bend stiffener provides a gradually increase of the bending stiffness from the rather small value of the compliant structure to a significantly larger value that can be rigidly connected without compromising the structural integrity of the compliant structure. Hence, the bend stiffener geometry needs to be designed to fulfill the design requirements for extreme as well as fatigue loading conditions for the compliant structure. Furthermore, it is required that the bend stiffener is as short as possible to limit costs, support forces, and enable fabrication and installation. The main focus of this paper is to outline an optimization scheme for bend stiffeners to meet design criteria for extreme loading conditions. Measures to provide an adequate fatigue performance of bend stiffeners are also discussed. The loads on the bend stiffener are governed by effective tension and relative angle close to the support (i.e. direction of effective tension relative to the longitudinal direction of the compliant structure at the support). Combinations of effective tension and relative angle aggregated for all relevant extreme load conditions define the design loads on the bend stiffener. The capacity of the compliant structure is governed by a capacity curve expressing the allowable curvature as function of the effective tension. A general optimization scheme is outlined accounting for a general description of the design loads as well as the capacity curve. The optimization methodology is based on a general purpose optimization algorithm utilizing a tailor made non-linear static finite element solver to describe the response of the bend stiffener and the compliant structure. Non-dimensional design curves are also presented based on a simplified conservative description of the design loads and the capacity. This allows for easy practical sizing of bend stiffeners without the need for sophisticated optimization software.

Fatigue Life Estimates for a Notched Member in a Corrosive Environment

1987 ◽  
Vol 109 (1) ◽  
pp. 135-141 ◽  
Author(s):  
P. Kurath ◽  
Z. Khan ◽  
D. F. Socie
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Material Properties ◽  
Experimental Program ◽  
Nacl Solution ◽  
Linear Elastic ◽  
Cracked Plates ◽  
Fatigue Life Estimation ◽  
Mechanics Concepts ◽  
Life Predictions

It is often assumed that the effects of an aggressive environment can be included in fatigue life estimation procedures by determining the material properties in the environment and at the frequency of interest. An analytical and experimental program was conducted to confirm or refute this assumption. Automotive grade aluminum alloy, 5454-H32, in 3 percent NaCl solution and laboratory environment was selected for this study. A simple model where the total fatigue life is the summation of the portion where fatigue damage is best described by the notch strain field, and the portion where nominal stress and crack length dominate damage assessment, was used to estimate fatigue lives for center notched plates. Smooth cylindrical specimens were employed to determine the material properties for initiation. The environment had a large influence on the initiation resistance of this material at long fatigue lives, whereas at shorter fatigue lives (i.e., <104 cycles) there was little effect. Center cracked plates were used to determine the crack growth rates. Linear elastic fracture mechanics concepts were employed to estimate crack propagation lives. Approximately a factor of three reduction in crack propagation life was attributable to the hostile environment. Center notched plate specimens with Kt = 2.4 and Kt=5.1 were tested in both environments to examine the model. The accuracy of the fatigue life predictions in relation to the experimental data were comparable in 3 percent NaCl solution to the results obtained in laboratory air.

Corrosion modified fatigue analysis for next-generation damage-tolerant management

2019 ◽  
Vol 37 (5) ◽  
pp. 507-520
Author(s):  
Nathan Brown ◽  
Brandi Clark ◽  
Patrick Kramer ◽  
Noelle Easter C. Co ◽  
Fritz Friedersdorf ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Structural Integrity ◽  
Corrosion Damage ◽  
Fatigue Analysis ◽  
Element Analysis ◽  
Linear Elastic ◽  
Analysis Process ◽  
Aircraft Component ◽  
Integrity Management ◽  
Damage Tolerant

AbstractAlthough a great deal of success in structural integrity management has been achieved, it may be realized by excessively conservative assumptions, high inspection burdens, and aggressive maintenance and repair strategies. Corrosion has been found to reduce fatigue life, but methods to account for it in fatigue modeling are still limited. There is a recognized need to improve structural integrity calculations through the inclusion of the effect of existing corrosion damage on fatigue. The feasibility of a corrosion modified fatigue analysis process that uses finite element analysis and linear elastic fracture mechanics techniques to predict fatigue life of a corroded aircraft component based on the corrosion damage location is demonstrated in this work. A corrosion modified equivalent flaw size was successfully used to predict fatigue crack growth from AA7075-T651 specimens with two different notch geometries and corrosion damage at the notch center.

Prediction of Fatigue Life for Single Fastener Joints in Composite Laminates

2013 ◽  
Vol 773 ◽  
pp. 460-467
Author(s):  
Dan Yong Wang ◽  
Jun Cong Liu ◽  
Yi Wei Chen ◽  
Shu Hu Li ◽  
Hua Zhen Wei
Keyword(s):  
Fatigue Life ◽  
Material Property ◽  
Composite Laminates ◽  
Virtual Work ◽  
Three Dimensional ◽  
Fatigue Loading ◽  
Failure Criteria ◽  
Progressive Damage ◽  
Loading Conditions ◽  
Software Module

A progressive damage method of predicting the fatigue life of mechanically fastened joints in fiber-reinforced plastics was established, which is integrated fatigue material property degradation models. The equations of virtual work based on the theory of time increment were deduced to analyze stress-strain states under fatigue loading conditions. The three-dimensional Hashin-type fatigue failure criteria were introduced into the method to detect damage for diverse damage modes. The criteria of the structure catastrophe and the sudden material property degradation rules including the correlation among four basic damage mechanisms were also established. A software module of progressive damage analyses for bolted composite laminates is compiled, which is convenient for the application in engineering. The fatigue life, failure initiation, propagation and catastrophic failure of composite bolted joints under tension-tension fatigue loading conditions are predicted by using the fatigue progressive damage method established in the paper. An excellent agreement is found between data obtained from this study and the experiment.

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