A machine for cyclic creep and low-cycle fatigue tests in the complex stressed state in a broad temperature range

The low cycle fatigue behaviors of TI-6AL-4V alloy controlled by strain were investigated by experiment. The fatigue tests were performed at room temperature, and cyclic strain and stress ratio are 0.1 with triangle load wave. The results show that TI-6AL-4V alloy is soften rapidly under the cyclic tensile stresses and it is harden rapidly under the cyclic compressive stresses during the initial-stage of strain controlled fatigue, and the rates of cyclic soften and cyclic harden are decreased with the fatigue progress. The soften rate is related to the cyclic strain but little to the cyclic stress during the overall fatigue progress. The change of cyclic stress is related to the macro friction stresses. The results of experiment show that obvious cyclic creep occurs under the stress controlled low cycle fatigue conditions, and the magnitude of cyclic creep strain is related to the maximum cyclic stress. The softening of tensile friction stresses is the main factor of cyclic creep.

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Installation for high-temperature cyclic creep and low-cycle fatigue tests

Strength of Materials ◽

10.1007/bf00769202 ◽

1982 ◽

Vol 14 (1) ◽

pp. 130-133

Author(s):

V. V. Osasyuk ◽

Yu. A. Kuzema ◽

V. D. Man'ko

Keyword(s):

High Temperature ◽

Low Cycle Fatigue ◽

Cyclic Creep ◽

Fatigue Tests ◽

Cycle Fatigue

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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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Low-Cycle Fatigue Behaviour of Gas Turbine Alloys

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1974_188_037_02 ◽

1974 ◽

Vol 188 (1) ◽

pp. 321-328 ◽

Cited By ~ 1

Author(s):

W. J. Evans ◽

G. P. Tilly

Keyword(s):

Low Cycle Fatigue ◽

Fatigue Cracks ◽

High Stress ◽

Cyclic Creep ◽

Fatigue Curve ◽

Fatigue Behaviour ◽

Material Surface ◽

Tension Stress ◽

Cycle Fatigue ◽

Stress Tests

The low-cycle fatigue characteristics of an 11 per cent chromium steel, two nickel alloys and two titanium alloys have been studied in the range 20° to 500°C. For repeated-tension stress tests on all the materials, there was a sharp break in the stress-endurance curve between 103 and 104 cycles. The high stress failures were attributed to cyclic creep contributing to the development of internal cavities. At lower stresses, failures occurred through the growth of fatigue cracks initiated at the material surface. The whole fatigue curve could be represented by an expression developed from linear damage assumptions. Data for different temperatures and types of stress concentration were correlated by expressing stress as a fraction of the static strength. Repeated-tensile strain cycling data were represented on a stress-endurance diagram and it was shown that they correlated with push-pull stress cycles at high stresses and repeated-tension at low stresses. In general, the compressive phase tended to accentuate cyclic creep so that ductile failures occurred at proportionally lower stresses. Changes in frequency from 1 to 100 cycle/min were shown to have no significant effect on low-cycle fatigue behaviour.

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Evaluation of the Heat Treatment Role for Light Aluminum Alloys Subjected to Creep and Low Cycle Fatigue

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.455 ◽

2010 ◽

Vol 638-642 ◽

pp. 455-460 ◽

Cited By ~ 1

Author(s):

A. Rutecka ◽

L. Dietrich ◽

Zbigniew L. Kowalewski

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Low Cycle Fatigue ◽

Numerical Models ◽

Cyclic Hardening ◽

Fatigue Tests ◽

Cycle Fatigue ◽

Lower Stress ◽

Creep Tests ◽

Different Temperatures

The AlSi8Cu3 and AlSi7MgCu0.5 cast aluminium alloys of different composition and heat treatment were investigated to verify their applicability as cylinder heads in the car engines [1]. Creep tests under the step-increased stresses at different temperatures, and low cycle fatigue (LCF) tests for a range of strain amplitudes and temperatures were carried out. The results exhibit a significant influence of the heat treatment on the mechanical properties of the AlSi8Cu3 and AlSi7MgCu0.5. An interesting fact is that the properties strongly depend on the type of quenching. Lower creep resistance (higher strain rates) and lower stress response during fatigue tests were observed for the air quenched materials in comparison to those in the water quenched. Cyclic hardening/softening were also observed during the LCF tests due to the heat treatment applied. The mechanical properties determined during the tests can be used to identify new constitutive equations and to verify existing numerical models.

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Effect of Different Welded Structures on Mechanical Properties of TA2 Tube-to-Tubesheet Joints

Journal of Pressure Vessel Technology ◽

10.1115/1.4026566 ◽

2014 ◽

Vol 136 (4) ◽

Cited By ~ 1

Author(s):

Xinlong Wei ◽

Yang Qian ◽

Junhui Wang ◽

Jianxin Zhou ◽

Xiang Ling

Keyword(s):

Applied Load ◽

Low Cycle Fatigue ◽

Weld Zone ◽

Steel Tube ◽

Fatigue Tests ◽

Cycle Fatigue ◽

Welded Structures ◽

Pull Out ◽

Weld Toe ◽

Welded Tube

Four types of TA2 welded tube-to-tubesheet joints prepared by manual tungsten arc argon-shielded welding technique are studied in this paper. The pull-out tests and low cycle fatigue tests were performed to optimize welded structures of tube and tubesheet. The results show that fractures of welded TA2 tube and tubesheet samples occur at weld zone of TA2 steel tube for the pull-out tests and low cycle fatigue tests. The extension-tubesheet welded joints have the maximum pull-out forces and the best fatigue resistance, and the internal-bore welded joint with 45 deg bevel occupies second place. Fractures are both initiated from weld toe of the outside of tube for the pull-out tests and low cycle fatigue tests. Crack propagates along the direction of 45 deg for the pull-out test. However, crack propagates perpendicularly to the direction of the applied load for low cycle fatigue test, and then fractures immediately parallel to the direction of the applied load. Fatigue striations with a spacing of about 10 μm can be observed on the fatigue crack propagation zone. However, hemispheroidal dimples exist on instant rupture zone.

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Damage in Adhesive Joints During Low Cycle Fatigue

Volume 9: Mechanics of Solids, Structures and Fluids ◽

10.1115/imece2010-40676 ◽

2010 ◽

Author(s):

Iva´n C. Ca´bulo-Pe´rez ◽

Juan P. Casas-Rodri´guez

Keyword(s):

Plastic Strain ◽

Low Cycle Fatigue ◽

Stress Test ◽

Damage Model ◽

Fatigue Tests ◽

Constant Stress ◽

Cycle Fatigue ◽

Damage Behavior ◽

Non Linear ◽

Compressive Loads

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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