Monitoring of aeronautical composites with embedded FOBG sensor: Part I—Manufacturing and strain response under incremental fatigue loading spectrum

2020 ◽  
Author(s):  
Tryfon Karagiannis ◽  
Evangelos F. Karachalios ◽  
Nikolaos D. Alexopoulos
Keyword(s):  
Fatigue Loading ◽  
Strain Response ◽  
Loading Spectrum

The Reliability of a Component Under Multiple Cyclic Stress Levels With Distributed Cyclic Numbers

2016 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Fatigue Life ◽  
Probabilistic Models ◽  
Random Variable ◽  
Fatigue Loading ◽  
Cyclic Stress ◽  
Initial Crack ◽  
Stress Levels ◽  
Single Constant ◽  
Unsolved Issue ◽  
Loading Spectrum

Fatigue damage is initiated through some “defects” on the surfaces of and/or inside the component and induced by the fatigue cyclic loadings. These “defects” are randomly scattered in components, and one of these “defects” will be randomly “activated” and finally developed to become the initial crack which causes the final fatigue failure. Therefore, the fatigue strength is inherently a random variable and should be treated by probabilistic models such as typical P-S-N curves. The fatigue cyclic loading could be presented or described in any form. But the fatigue loading spectrum can generally be grouped as and described by these five models: (1) a single constant cyclic stress (loading) with a given cyclic number, (2) a single constant cyclic stress with a distributed cyclic number, (3) a distributed cyclic stress (loading) at a given fatigue life (cyclic number), (4) multiple constant cyclic stress levels with given cyclic numbers, and (5) multiple constant cyclic stress levels with distributed cyclic numbers. The approaches for determining the reliability of components under fatigue loading spectrum of the models 1∼4 are available in literature and books. But few articles and books have addressed an approach for determining the reliability of components under the fatigue loading spectrum of the model 5. This paper will propose two approaches for addressing this unsolved issue. Two examples will be presented to implement the proposed approaches with detailed procedures.

The Effect of Fatigue Loading Spectrum on Crack Propagation in a Ship Detail

2018 ◽  
Author(s):  
Xiaoping Huang ◽  
Xiaoshun Yan ◽  
Muk Chen Ong ◽  
Yingcai Huang
Keyword(s):  
Crack Growth ◽  
Shape Parameter ◽  
Fatigue Loading ◽  
Ship Hull ◽  
Random Wave ◽  
Fatigue Assessment ◽  
Loading Sequence ◽  
Wave Induced ◽  
Loading Spectrum

The assessment of the loading sequence on fatigue crack growth of cracked details is essential when the ship hull is subjected to random wave-induced loading during the service time. In this paper, the effect of loading sequence on the crack growth life is investigated in order to find a physical engineering method to generate fatigue loading spectrum for ship fatigue assessment. The long term distribution of fatigue loading and the unique crack growth rate curve model have been employed in the analysis. The results show that the shape parameter affects the fatigue life significantly if the long-term distribution of wave-induced stress range is modeled by two-parameter Weibull distribution. Moreover, the spectral-based method provides a reasonable fatigue loading spectrum and avoid the confusion in determining the shape parameter for different empirical formulas, which are recommended by several main ship classification societies. An example of fatigue assessment for a cracked detail in a container ship is demonstrated as a reference for fatigue assessment of a ship hull based on crack growth.

Riser Resistance to In-Service Fatigue Loading

2013 ◽  
Author(s):  
Francesco Iob ◽  
Elisabetta Mecozzi ◽  
Luigi Di Vito ◽  
Philippe Darcis ◽  
Israel Marines-Garcia ◽  
...  
Keyword(s):  
Complex Loading ◽  
Fatigue Loading ◽  
Fatigue Performance ◽  
Sensitivity Analyses ◽  
Full Thickness ◽  
Constant Amplitude ◽  
Riser Pipe ◽  
Service Loading ◽  
Girth Welds ◽  
Loading Spectrum

Riser systems are subjected to complex loading spectra induced by sea states. The complex loading spectrum differs sensibly from the constant amplitude loading commonly adopted for qualification of the product (riser pipe and its girth welds). The present work deals with numerical calculations of the actual loading spectrum experienced by a Steel Catenary Riser when adopted in different scenarios, Gulf of Mexico (GoM) and West of Africa (WoA). Sensitivity analyses have been performed to evaluate the influence on applied fatigue loading of different parameters, like: water depth, seabed stiffness, hang-off angle. The variable amplitude loading, derived from in-service conditions, has been applied to laboratory scale, full thickness specimens from X65 SCR girth welds. The fatigue performance of these samples has been compared to analogous samples subjected to constant amplitude loading. The samples subjected to in-service loading conditions exhibited a lower fatigue performance than in constant amplitude. To allow a comparison with common qualification procedure under constant amplitude, full scale testing of SCR girth welds have been performed on resonance machine by in-service loading spectra rearranged in constant amplitude blocks. Laboratory full thickness specimens have been adopted to compare the girth weld fatigue performance when subjected to the original cycle-by-cycle sequence and the in-blocks rearranged sequence.

Effect of Fatigue Loading on Tendon Fascicle Extension Mechanisms

2013 ◽  
Author(s):  
Chavaunne T. Thorpe ◽  
Helen L. Birch ◽  
Peter D. Clegg ◽  
Hazel R. C. Screen
Keyword(s):  
Achilles Tendon ◽  
Fatigue Loading ◽  
Cyclic Fatigue ◽  
Tendon Injury ◽  
Sudden Onset ◽  
Applied Strain ◽  
Strain Response ◽  
Onset Condition ◽  
Energy Store ◽  
Repetitive Loading

Tendon injury is common, probably occurring due to accumulation of microdamage within the tendon matrix as a result of repetitive loading rather than as a sudden onset condition 1. The human Achilles tendon is highly susceptible to injury; this tendon functions as an energy store and experiences high stresses and strains during normal use 2. The equine superficial digital flexor (SDFT) is also an energy storing tendon and is highly injury prone, therefore it is often used as a model to study structure function relationships within this type of tendon 3. Our previous work has characterized the microstructural response of SDFT fascicles to applied strain, with results indicating the presence of a helical component to the fascicle which may facilitate extension by unwinding of the coil 4. The aim of this study was to assess the effect of cyclic fatigue loading (creep) on the microstructural strain response of the equine SDFT to test the hypothesis that fatigue loading would result in altered fascicle extension mechanisms.

The Reliability Calculation of Components Under Any Cyclic Fatigue Loading Spectrum

2017 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Stress Amplitude ◽  
Fatigue Loading ◽  
Cyclic Fatigue ◽  
Cyclic Stress ◽  
Fatigue Reliability ◽  
Cycle Number ◽  
New Approach ◽  
Systematic Description ◽  
Reliability Calculation ◽  
Loading Spectrum

The fatigue failure of metal components is due to cyclic fatigue loading. The typical cyclic fatigue loading spectrums described in the literature includes only a few simple cyclic loadings such as a constant amplitude of cyclic fatigue loading with a given cycle number, several constant amplitudes of cyclic fatigue loadings with given cycle numbers, and a distributed stress amplitude of a cyclic stress with a given cycle number or an infinite life. The systematic description of cyclic fatigue loading spectrums is necessary and wasn’t presented in the literature. This paper will present a systematic description of all possible types of cyclic fatigue loading spectrums, which includes 6 different cyclic fatigue loading spectrum models. The P-S-N curve fatigue theory is widely accepted not only for describing the fatigue test data, but also for estimating the reliability of components under cyclic fatigue loading spectrum. However, the reliability calculation of a component under several distributed stress levels with corresponding given cyclic numbers has not been solved according to the literature review. This paper presents a new approach to estimate the reliability of components under such cyclic fatigue loading spectrum. With the contribution of this paper, the P-S-N curve fatigue theory now becomes a complete fatigue reliability theory and can be used to estimate the reliability of components under any type of cyclic fatigue loading spectrum.

Hybrid Riser Resistance to In-Service Fatigue Loading

2014 ◽  
Author(s):  
Francesco Iob ◽  
Elisabetta Mecozzi ◽  
Luigi Di Vito ◽  
Philippe Darcis ◽  
Israel Marines-Garcia ◽  
...  
Keyword(s):  
Cross Flow ◽  
Complex Loading ◽  
Fatigue Loading ◽  
Fatigue Performance ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Riser Pipe ◽  
Wide Range ◽  
Girth Welds ◽  
Loading Spectrum

Riser systems are subjected to complex loading spectra. A wide range of amplitude loading are induced by naturally complex sea states. The complex loading spectrum differs sensibly from the constant amplitude loading commonly adopted for qualification of the product (riser pipe and its girth welds or threaded connections). The present paper reports numerical calculations and a comparison of the actual fatigue loading experienced by different riser systems, Steel Catenary Risers (SCR), Lazy Wave Riser (LWR), Hybrid Risers (HR). For the Hybrid riser system, a good fatigue resistance, due to the vessel and wave first motion decoupling, is obtained. On the other hand, the phenomenon of cross flow vibration induced by Vortex Induced Vibrations (VIV), could significantly affect the hybrid riser fatigue performance. In this case, a sensitivity analysis has been performed to evaluate the influence of different parameters, on the applied fatigue loading, like: riser tension, hydro diameter (i.e. external pipe diameter including coating), riser wall thickness, current velocity. The HR variable amplitude loading spectrum, derived from in-service conditions, referred to Gulf of Mexico scenario, has been calculated and applied in laboratory tests on girth welds of X65, 10.75″ OD, 25.4 mm WT riser. Furthermore, the fatigue performance of these tests has been compared to analogous tests on samples subjected to constant and variable amplitude loading available from previous work on SCR system[1].

Inhibition of RANKL-mediated bone remodeling decreases bone damage and improves strength in response to fatigue loading

2014 ◽  
Author(s):  
Nicolas Bonnet ◽  
Maude Gerbaix ◽  
Paul Kostenuik ◽  
Mike Ominsky ◽  
Serge Ferrari
Keyword(s):  
Bone Remodeling ◽  
Fatigue Loading ◽  
Bone Damage

Experimental Characterization of Mechanical Behavior of Cord-Rubber Composites

1982 ◽  
Vol 10 (1) ◽  
pp. 37-54 ◽  
Author(s):  
M. Kumar ◽  
C. W. Bert
Keyword(s):  
Response Characteristic ◽  
Cord Compression ◽  
Complete Characterization ◽  
Strain Response ◽  
Strain Gages ◽  
Experimental Characterization ◽  
Rubber Composites ◽  
Stress Strain ◽  
Strain Data

Abstract Unidirectional cord-rubber specimens in the form of tensile coupons and sandwich beams were used. Using specimens with the cords oriented at 0°, 45°, and 90° to the loading direction and appropriate data reduction, we were able to obtain complete characterization for the in-plane stress-strain response of single-ply, unidirectional cord-rubber composites. All strains were measured by means of liquid mercury strain gages, for which the nonlinear strain response characteristic was obtained by calibration. Stress-strain data were obtained for the cases of both cord tension and cord compression. Materials investigated were aramid-rubber, polyester-rubber, and steel-rubber.

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