Low Cycle Fatigue, Creep-Fatigue and Relaxation-Fatigue Tests on P91

Abstract This paper experimentally investigated the creep and fatigue behaviors of a low-pressure turbine (LPT) blade with 600 hours of service using a novel test system. Pure low cycle fatigue (LCF), pure creep and creep-fatigue interaction (CFI) experiments on the full-scale serviced blades were conducted respectively. Test results showed that the increasing of deformation amplitude was divided into three stages under both pure LCF and creep-fatigue loadings. The deformation of each blade increased rapidly until failure when the test cycle exceeded the 80% of their overall life under the pure LCF and CFI condition. The hold period in creep-fatigue tests shortens the first stage of whole life and has no influence on the proportion of crack initiation life to overall life. The fractures in pure LCF, pure creep and creep-fatigue tests emerged transgranular, intergranular and both transgranular and intergranular behaviors respectively. The crack initiated and propagated in a specific zone of the blade under all the experimental loadings, which limited its creep-fatigue resistance. At last, the remaining life of turbine blade was estimated conservatively by introducing the safety limit into a statistical method.

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Study on Life Prediction Method for Creep-Fatigue Interaction at Elevated Temperature

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.353-358.190 ◽

2007 ◽

Vol 353-358 ◽

pp. 190-194

Author(s):

Nian Jin Chen ◽

Zeng Liang Gao ◽

Wei Zhang ◽

Yue Bao Le

Keyword(s):

Elevated Temperature ◽

Prediction Model ◽

Life Prediction ◽

Low Cycle Fatigue ◽

Hold Time ◽

Prediction Method ◽

Fatigue Tests ◽

Cycle Fatigue ◽

Creep Fatigue ◽

316L Austenitic Stainless Steel

The law of low-cycle fatigue with hold time at elevated temperature is investigated in this paper. A new life prediction model for the situation of fatigue and creep interaction is developed, based on the damage due to fatigue and creep. In order to verify the prediction model, strain-controlled low-cycle fatigue tests at temperature 693K, 823K and 873K and fatigue tests with various hold time at temperature 823K and 873K for 316L austenitic stainless steel were carried out. Good agreement is found between the predictions and experimental results.

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Experimental techniques to carry out low-cycle fatigue and creep-fatigue tests: a bibliographic reviewSimon, S., Rodriguez, J.M. and Fuentes, M. Rev. Metal. May–June 1989 25, (3), 184–194 (in Spanish)

International Journal of Fatigue ◽

10.1016/0142-1123(90)90319-a ◽

1990 ◽

Vol 12 (6) ◽

pp. 531-531

Keyword(s):

Low Cycle Fatigue ◽

Fatigue Tests ◽

Experimental Techniques ◽

Cycle Fatigue ◽

Creep 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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Component Low Cycle Fatigue Behavior Based on Standard Calculation Procedure and Non-Linear FEA

Volume 3B: Design and Analysis ◽

10.1115/pvp2017-66071 ◽

2017 ◽

Author(s):

Jürgen Rudolph ◽

Adrian Willuweit ◽

Steffen Bergholz ◽

Christian Philippek ◽

Jevgenij Kobzarev

Keyword(s):

Power Plants ◽

Low Cycle Fatigue ◽

Fatigue Behavior ◽

Hybrid Approach ◽

Combined Cycle ◽

Cycle Fatigue ◽

Element Analysis ◽

Constitutive Material Model ◽

Standard Design ◽

Creep Fatigue

Components of conventional power plants are subject to potential damage mechanisms such as creep, fatigue and their combination. These mechanisms have to be considered in the mechanical design process. Against this general background — as an example — the paper focusses on the low cycle fatigue behavior of a main steam shut off valve. The first design check based on standard design rules and linear Finite Element Analysis (FEA) identifies fatigue sensitive locations and potentially high fatigue usage. This will often occur in the context of flexible operational modes of combined cycle power plants which are a characteristic of the current demands of energy supply. In such a case a margin analysis constitutes a logical second step. It may comprise the identification of a more realistic description of the real operational loads and load-time histories and a refinement of the (creep-) fatigue assessment methods. This constitutes the basis of an advanced component design and assessment. In this work, nonlinear FEA is applied based on a nonlinear kinematic constitutive material model, in order to simulate the thermo-mechanical behavior of the high-Cr steel component mentioned above. The required material parameters are identified based on data of the accessible reference literature and data from an own test series. The accompanying testing campaign was successfully concluded by a series of uniaxial thermo-mechanical fatigue (TMF) tests simulating the most critical load case of the component. This detailed and hybrid approach proved to be appropriate for ensuring the required lifetime period of the component.

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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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Impact of Temperature on Low-Cycle Fatigue Characteristics of the HR6W Alloy

Materials ◽

10.3390/ma14226741 ◽

2021 ◽

Vol 14 (22) ◽

pp. 6741

Author(s):

Grzegorz Junak ◽

Anżelina Marek ◽

Michał Paduchowicz

Keyword(s):

Fatigue Life ◽

Room Temperature ◽

Low Cycle Fatigue ◽

Fatigue Tests ◽

Total Strain ◽

Cycle Fatigue ◽

Fatigue Characteristics

This paper presents the results of tests conducted on the HR6W (23Cr-45Ni-6W-Nb-Ti-B) alloy under low-cycle fatigue at room temperature and at 650 °C. Fatigue tests were carried out at constant values of the total strain ranges. The alloy under low-cycle fatigue showed cyclic strengthening both at room temperature and at 650 °C. The degree of HR6W strengthening described by coefficient n’ was higher at higher temperatures. At the same time, its fatigue life Nf at room temperature was, depending on the range of total strain adopted in the tests, several times higher than observed at 650 °C.

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