Modelling low-cycle fatigue tests using a gradient-enhanced continuum damage model

The objective of this research is to study the damage behavior of bulk adhesive and single lap joint (SLJ) specimens during low cycle fatigue (LCF). Fatigue tests under constant stress amplitude were done and strain response was measured through cycles to failure using the bulk adhesive and SLJ data. A non linear damage model was used to fit experimental results. Identification of the damage parameters for bulk adhesive was obtained from the damage against accumulated plastic strain plot. It is shown that the plastic strain can be obtained from the constant stress test if the instantaneous elastic modulus, i.e. modulus affected by damage, is evaluated for each cycle. On the other hand, damage in SLJ was seen mainly in the adhesive for itself — no substrate failure — this fact is used to propose that fatigue response in the joint is due to continuum damage accumulation in the adhesive as the number of cycles increases. Damage behavior under compressive loads was not taken into account but good correlation of numerical and experimental data was obtained. It was found that damage evolution behaves in a non linear manner as the plastic deformation grows for each cycle: on fatigue onset an accelerated damage grow is observed, then a proportional evolution, and finally a rapid failure occurs; this characteristics were seen in both the SLJ and bulk adhesive specimen. So far, this research takes the damage model found in a standard adhesive specimen and assumes it is accurate enough to represent the damage behavior of the SLJ configuration.

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An anisotropic continuum damage model for high-cycle fatigue

Mechanics of Advanced Materials and Structures ◽

10.1080/15376494.2019.1697472 ◽

2020 ◽

pp. 1-15

Author(s):

Liang Zhang ◽

Zhenyuan Gao ◽

Robert A. Haynes ◽

Todd C. Henry ◽

Wenbin Yu

Keyword(s):

High Cycle Fatigue ◽

Damage Model ◽

Continuum Damage ◽

Cycle Fatigue ◽

Continuum Damage Model

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Continuum Damage Model of Creep-Fatigue Interaction in Ni-Base Superalloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.340-341.235 ◽

2007 ◽

Vol 340-341 ◽

pp. 235-240 ◽

Cited By ~ 1

Author(s):

Jong Taek Yeom ◽

Chong Soo Lee ◽

Jeoung Han Kim ◽

Dong Geun Lee ◽

Nho Kwang Park

Keyword(s):

Low Cycle Fatigue ◽

Fatigue Behavior ◽

Equivalent Stress ◽

Damage Model ◽

Fem Simulation ◽

Interaction Region ◽

Continuum Damage ◽

Continuum Damage Model ◽

Creep Fatigue ◽

The Continuum

A methodology for evaluating and predicting component lives in creep-fatigue interaction region was investigated for Waspaloy. A unified viscoplasticity constitutive equation including multi-back stresses was used to describe cyclic material behaviors. Also, a continuum damage model coupling with the creep-fatigue damage rules was established based on the analysis of creep and low cycle fatigue behavior. Multi-axial fatigue and creep equivalent stress concepts were employed to predict three dimensional component lives. Notched cyclic tests under various stress conditions in the creep-fatigue interaction region were carried out to validate the life prediction methodology with FEM simulation based on the continuum damage model. The comparison of experimental data and prediction results indicates that the continuum damage model is a powerful approach for the prediction of component lives.

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Fatigue Testing of Wearable Sensing Technologies: Issues and Opportunities

Materials ◽

10.3390/ma14154070 ◽

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.

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Cumulative acoustic emission energy for damage detection in composites reinforced by carbon fibers within low-cycle fatigue regime at various displacement amplitudes and rates

Polymers and Polymer Composites ◽

10.1177/0967391120985709 ◽

2021 ◽

pp. 096739112098570

Author(s):

Mohammad Azadi ◽

Mohsen Alizadeh ◽

Seyed Mohammad Jafari ◽

Amin Farrokhabadi

Keyword(s):

Acoustic Emission ◽

Carbon Fibers ◽

Polymer Matrix Composites ◽

Low Cycle Fatigue ◽

Energy Parameter ◽

Fatigue Tests ◽

Matrix Cracking ◽

Matrix Composites ◽

Cycle Fatigue ◽

Cumulative Energy

In the present article, acoustic emission signals were utilized to predict the damage in polymer matrix composites, reinforced by carbon fibers, in the low-cycle fatigue regime. Displacement-controlled fatigue tests were performed on open-hole samples, under different conditions, at various displacement amplitudes of 5.5, 6.0, 6.5 and 7.0 mm and also under various displacement rates of 25, 50, 100 and 200 mm/min. After acquiring acoustic emission signals during cycles, two characteristic parameters were used, including the energy and the cumulative energy. Obtained results implied that the energy parameter of acoustic emission signals could be used only for the macroscopic damage, occurring at more than 65% of normalized fatigue cycles under different test conditions. However, the cumulative energy could properly predict both microscopic and macroscopic defects, at least two failure types, including matrix cracking at first cycles and the fiber breakage at last cycles. Besides, scanning electron microscopy images proved initially such claims under all loading conditions.

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