The Thermo-Mechanical Behaviour of Alloy 600 and Alloy 82 Materials

2018 ◽  
Author(s):  
Vasileios Akrivos ◽  
Mike C. Smith
Keyword(s):  
Weld Metal ◽  
Low Cycle Fatigue ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
Parent Material ◽  
Model Parameters ◽  
Alloy 600 ◽  
Cycle Fatigue ◽  
Chaboche Model ◽  
Different Temperatures

Isothermal uniaxial low cycle fatigue tests have been performed at two different total strain ranges (1.5% and 2.5%) and at different temperatures (20, 200, 400 and 600°C) for Alloy 600 and Inconel 82 materials. The materials hardening behaviour has been fitted using the Lemaitre Chaboche formulations using different fitting strategies. Thermo mechanical tests have been performed using a Gleeble machine on both parent material and weld metal. In these tests thermal cycles were applied to a constrained specimen simulating the welding conditions in both the heat affected zone and a weld bead when subsequent beads are deposited alongside. The tests were modelled using two different FE codes, namely Code_Aster and Abaqus. This allowed the validation of the Lemaitre-Chaboche model parameters when the material is subjected to realistic thermo-mechanical cycles. Simulations were conducted using both annealing and/or viscous recovery features to examine their impact on the predicted response.

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

2010 ◽  
Vol 638-642 ◽  
pp. 455-460 ◽  
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.

Isothermal Low-Cycle Fatigue Evaluation of External Weld Repair Using Alloy 182 Filler Metal With Backing Plate Design

2020 ◽  
Author(s):  
Shutong Zhang ◽  
Sebastian A. Romo ◽  
Jorge Penso ◽  
Haixia Guo ◽  
Lisa Ely ◽  
...  
Keyword(s):  
Weld Metal ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Pressure Vessels ◽  
Cycle Fatigue ◽  
Residual Oil ◽  
Weld Repair ◽  
Oil Refineries ◽  
Backing Plate ◽  
Dog Bone

Abstract Coke drums are pressure vessels used in the delayed coking process at oil refineries, which transform heavy residual oil into light-weight hydrocarbon molecules and solid coke through thermal cracking. Due to the severe thermal and mechanical loadings during operation, these vessels experienced low-cycle fatigue failure, which led to shell and skirt damage such as bulging and cracking. External weld repairs using the temper bead technique have been widely applied to repair damaged regions caused by bulging and cracking for preventing the leaks of the residual oil contents. However, a substantial proportion of the external repairs have been reported to experience post-repair cracking issues. In this study, an external weld repair mockup with a backing plate was evaluated through metallurgical characterizations and isothermal low-cycle fatigue tests. The micro-hardness mapping identified the mismatching interfaces from base metal to weld metal (WM) and from root passes to internal clad. Four types of dog-bone samples were extracted from the weld: weld metal, heat affected zone, internal clad and backing plate. These samples were used to evaluate the fatigue resistance of weld metal and transition zone under low-cycle fatigue tests. Failure analysis showed that weld metal samples were susceptible to multiple-crack initiations, while other transition samples failed at mismatching interfaces or stress concentration points at weld toes.

Study on Skirt-to-Shell Attachment of Coke Drum by Evaluation of Fatigue Strength of Weld Metal

2011 ◽  
Author(s):  
Yasuhiko Sasaki ◽  
Shinta Niimoto
Keyword(s):  
Fatigue Strength ◽  
Weld Metal ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Fatigue Design ◽  
Inner Radius ◽  
Section Viii

A skirt-to-shell attachment of a coke drum experience severe thermal cyclic stresses, which cause failures due to low cycle fatigue. Various skirt attachment designs, therefore, have been proposed and implemented. A design where the skirt is attached by a weld build-up is most commonly used. A design where the skirt is attached to the drum shell by utilizing an integral machined plate or forging has been utilized in several projects. One of the advantages of the integral skirt attachment is that a large inner radius can be formed which allows reducing stress concentration compared with the weld build-up design. This advantage can be confirmed easily by FE-analysis in recent years [1] [2] [3]. Another major advantage of the integral skirt attachment is that the area of highest stress intensity is located at the base metal section, not at the weld metal or the heat affected zone which are generally thought to have lower fatigue strength. The fatigue design curve from ASME Section VIII Division 2 [9] is based on fatigue tests for the base metal. It is necessary to reveal differences of fatigue strength among these metals. This paper describes a comparison of fatigue strength of three metals: i) base metal ii) weld metal iii) heat affected zone provided by the low cycle fatigue test for 1 1/4Cr-1/2Mo materials. Our results indicate that the fatigue life of the base metal is about twice as long as that of the weld metal and about three times as long as the heat affected zone. Accordingly, the integral skirt attachment is more resistant to cracking than its welded counterpart from a fatigue strength viewpoint.

Applicability of Nonlinear Kinematic Hardening Models to Low Cycle Fatigue Simulation of C(T) Specimen

2018 ◽  
Author(s):  
Hune-Tae Kim ◽  
Gyo-Geun Youn ◽  
Jong-Min Lee ◽  
Yun-Jae Kim ◽  
Jin-Weon Kim
Keyword(s):  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Hysteresis Loops ◽  
Load Ratio ◽  
T Test ◽  
Model Parameters ◽  
Cycle Fatigue ◽  
Hardening Models ◽  
Chaboche Model ◽  
Loading Sequence

To perform low cycle fatigue analysis on nuclear structural materials under cyclic loading, cyclic hardening rules should be determined. In this study, the determination of linear and nonlinear kinematic hardening model parameters based on limited material test data is proposed. Chaboche model parameters are determined from hysteresis loops for the purpose of comparison. Simulation of cyclic C(T) test is performed using the hardening models. In cyclic C(T) test, SA508 Gr.1a low alloy steel and SA312 TP316L stainless steel were taken and incremental loading sequence was adopted. In the loading sequence, displacement control was used for loading steps and load control was applied for unloading steps to maintain constant load ratio. A constant displacement increment was applied after each cycle. The simulation results using A&F model and Chaboche model are compared to verify the applicability of A&F model.

Modified Low Cycle Method as a New Criterion for a Life Fatigue Assessment in Foundry Industry

2013 ◽  
Vol 58 (3) ◽  
pp. 877-881
Author(s):  
M. Maj ◽  
K. Pietrzak ◽  
J. Piekło
Keyword(s):  
Fatigue Test ◽  
Low Cycle Fatigue ◽  
Cast Steel ◽  
Testing Machine ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
The Novel ◽  
Cycle Fatigue ◽  
Novel Method ◽  
New Criterion

Abstract The study describes the investigations of fatigue life carried out on selected grades of the G20Mn5 cast steel by two methods, i.e. the standard low-cycle fatigue test (LCF test) and modified low-cycle fatigue test (MLCF). The aim of these investigations was to verify the reliability of tests conducted by the novel method of MLCF [1, 2, 3]. Table 1 shows the results of mechanical tests carried out in accordance with the MLCF methodology on the G20Mn5 cast steel, while Figures 1a-b and 2 show the selected σ = f (ε) curves. Similar studies were carried out for the Mn-Ni cast steel [4]. Low-cycle fatigue tests (LCF) were carried out on an MTS 810 testing machine with control of force exerted on specimens whose dimensions were specified in [2].

scholarly journals Fatigue Testing of Wearable Sensing Technologies: Issues and Opportunities

Materials ◽  
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.

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

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.

LOW CYCLE FATIGUE BEHAVIOR AND LIFE PREDICTION OF A CAST COBALT-BASED SUPERALLOY

2012 ◽  
Vol 06 ◽  
pp. 251-256
Author(s):  
HO-YOUNG YANG ◽  
JAE-HOON KIM ◽  
KEUN-BONG YOO
Keyword(s):  
Fatigue Life ◽  
Strain Energy ◽  
Life Prediction ◽  
Prediction Models ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Total Strain ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Different Temperatures

Co -base superalloys have been applied in the stationary components of gas turbine owing to their excellent high temperature properties. Low cycle fatigue data on ECY-768 reported in a companion paper were used to evaluate fatigue life prediction models. In this study, low cycle fatigue tests are performed as the variables of total strain range and temperatures. The relations between plastic and total strain energy densities and number of cycles to failure are examined in order to predict the low cycle fatigue life of Cobalt-based super alloy at different temperatures. The fatigue lives is evaluated using predicted by Coffin-Manson method and strain energy methods is compared with the measured fatigue lives at different temperatures. The microstructure observing was performed for how affect able to low-cycle fatigue life by increasing the temperature.

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

2014 ◽  
Vol 136 (4) ◽  
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.

Damage in Adhesive Joints During Low Cycle Fatigue

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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