Comparison of Ni-Steel Dissimilar Joints for Coke Drum External Weld Repairs Based on Isothermal Low-Cycle Fatigue Tests

2021 ◽  
Author(s):  
Shutong Zhang ◽  
Sebastian Romo ◽  
Rafael Arthur Giorjao ◽  
Jorge Penso ◽  
Haixia Guo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Base Metal ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Alloy 625 ◽  
Weld Joints ◽  
Nickel Base ◽  
Filler Metals

Abstract Low-cycle fatigue failure has been widely accepted as the key mechanism causing damages of coke drums during cyclic thermal-mechanical loadings. Common damages of coke drums known as bulging and cracking are associated with accumulative plasticity caused by thermal and mechanical strains. External repairs using temper-bead welding techniques are implemented to repair welds in the damaged areas of coke drums, which provide structural support to the vessels. Compared with matching filler metals, Ni-base fillers including alloy 625 and alloy 182 are compatible with both low-alloy steel base metal and internal clads in terms of weldability and thermal expansion. However, the differences of yield strengths and cyclic hardening behaviors of nickel-base alloys from base metals compromise the fatigue resistances of weld joints. In this study, alloy 182 and alloy 625 repair coupons were evaluated and compared based on isothermal low-cycle fatigue tests. Low-cycle fatigue behaviors of both weld metals and 1.25Cr-0.5Mo base metal were measured at 1.0%, 1.5% and 2.0% strain amplitudes. Test results indicate both nickel-base filler metals exhibit overmatching strength over the base metal due to cyclic hardening. Low-cycle fatigue tests of Heat Affected zone (HAZ) samples show the failures of alloy 625 weld joints occur in the base metal, while the failures of alloy 182 weld joints occur along the fusion boundary. The observations show strength mismatch and fatigue resistance are the key factors to determine failure locations of the joints. In addition, cyclic hardening coefficients based on kinematic hardening model were extracted from experimental data to simulate the cyclic behaviors of the weld joints. Finite element simulation results were shown to be consistent with experimental data at stabilized cycles. Cyclic behaviors of weld metal and base metal within a weld transition sample were calculated based on the numerical model.

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.

Comparative Study of Microstructure and High Temperature Low Cycle Fatigue Behaviour of Nickel Base Superalloys Inconel 713LC and MAR-M247

2016 ◽  
Vol 713 ◽  
pp. 86-89 ◽  
Author(s):  
Ivo Šulák ◽  
Karel Obrtlík ◽  
Ladislav Čelko
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Casting Defects ◽  
Cycle Fatigue ◽  
Stress Strain Curve ◽  
Nickel Base

The present work is focused on the study of microstructure and low cycle fatigue behavior of the first generation nickel-base superalloy IN 713LC (low carbon) and its promising second generation successor MAR-M247 HIP (hot isostatic pressing) at 900 °C. Microstructure of both alloys was studied by means of scanning electron microscopy (SEM). The microstructure of both materials is characterized by dendritic grains, carbides and casting defects. Size and morphology of precipitates and casting defects were evaluated. Fractographic observations have been made with the aim to reveal the fatigue crack initiation place and relation to the casting defects and material microstructure. Low cycle fatigue tests were conducted on cylindrical specimens in symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 900 °C in air. Hardening/softening curves, cyclic stress-strain curve and fatigue life data of both materials were obtained. Cyclic stress-strain curve of MAR M247 is shifted approximately to 120 MPa higher stress amplitudes in comparison with IN 713LC. Significantly higher fatigue life of MAR-M247 has been observed in Basquin representation. On the other hand IN 713LC shows prolonged lifetime compared with MAR-M247 in the Coffin-Manson representation. Results obtained from high temperature low cycle fatigue tests are discussed.

Low Cycle Fatigue Study of 63Sn-37Pb Solder under Torsional Cyclic Loading

2013 ◽  
Vol 785-786 ◽  
pp. 72-75
Author(s):  
Hong Qiang Guo
Keyword(s):  
Experimental Data ◽  
Low Cycle Fatigue ◽  
Constant Strain Rate ◽  
Fatigue Tests ◽  
Stress And Strain ◽  
Cycle Fatigue ◽  
Fatigue Lifetime ◽  
Torsional Fatigue ◽  
Relationship Of ◽  
The Relationship

In this paper, the torsional fatigue tests under angle control at the constant strain rate of 5×10-3/s were conducted on 63Sn–37Pb solder over a range of . The relationship of stress and strain for the 63Sn–37Pb solder was investigated. The number of cycle with loading decrease of 25% was thought as the fatigue lifetime. The parameters of Coffin-Manson equation were determined based on the experimental data.

An Experimental Study on Low Cycle Fatigue of Inconel 617 Super Alloy

2006 ◽  
Vol 306-308 ◽  
pp. 163-168 ◽  
Author(s):  
Jae Hoon Kim ◽  
Duck Hoi Kim ◽  
Young Shin Lee ◽  
Young Jin Choi ◽  
Hyun Soo Kim ◽  
...  
Keyword(s):  
Strain Energy ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Fatigue Tests ◽  
Cyclic Behavior ◽  
Cycle Fatigue ◽  
Inconel 617 ◽  
Number Of Cycles ◽  
Cycles To Failure ◽  
Super Alloy

Low cycle fatigue tests are performed on the Inconel 617 super alloy that be used for structural material of hot gas casing for gas turbine. The relations between strain energy density and number of cycles to failure are examined in order to predict the low cycle fatigue life of Inconel 617 super alloy. The lives predicted by strain energy methods are found to coincide with experimental data and results obtained from the Coffin-Manson method. And, the cyclic behavior of the Inconel 617 super alloy is characterized by cyclic hardening with increasing number of cycles.

Fatigue resistance of Fe3Al-based alloys

2011 ◽  
Vol 1295 ◽  
Author(s):  
Florian Gang ◽  
Manja Krüger ◽  
Alexandra Laskowsky ◽  
Heike Rühe ◽  
Joachim H. Schneibel ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Iron Aluminide ◽  
Cycle Fatigue ◽  
Grain Sizes ◽  
Cast Alloys

ABSTRACTThe low cycle fatigue (LCF) behaviour of two cast as well as two hot extruded Fe3Al-based iron aluminide alloys, either with or without Cr, is investigated. All four alloys contain microalloying additions of Zr, Nb, C and B. Fatigue tests were carried out under strain control for strain amplitudes in the range of εa = 0.1 – 0.4 % for the cast alloys and εa = 0.1 – 0.7 % for the extruded materials, at frequencies of 1 Hz (extruded Fe3Al) and 3 Hz (all other alloys) and at room temperature and 300 °C. Within the first cycles all alloys show strong cyclic hardening. Furthermore the fatigue strain – fatigue life curves are steeper at 300 °C than at room temperature, showing increased fatigue strength at low cycle numbers due to increasing ductility and decreased fatigue strength at increasing cycle numbers because of reduced yield strength. Cr is found to have only a negligible influence on the fatigue behaviour of Fe3Al-based alloys. Comparison between the differently processed materials shows superior LCF properties of the hot extruded iron aluminides due to significantly smaller grain sizes.

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.

Modification of the Equation for Description of Wöhler's Curves

2010 ◽  
Vol 27 (1) ◽  
pp. 99-104 ◽  
Author(s):  
Sylwester Kłysz ◽  
Janusz Lisiecki ◽  
Tomasz Bąkowski
Keyword(s):  
Experimental Data ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Experimental Results ◽  
Fatigue Threshold ◽  
Cycle Fatigue ◽  
Exponential Equation ◽  
The Way

Modification of the Equation for Description of Wöhler's Curves The paper presents the way to modify the equation σ = f(2Nf) in order to improve the fit of experimental results from High Cycle Fatigue tests. In particular, the study deals with introduction of the 5-parameter exponential equation that enables better fit of the full Wöhler's curve to experimental data within the range of stress at the level of fatigue threshold as well as approximation to the quasi-static range and Low Cycle Fatigue tests for the highest stress values. It is illustrated how individual parameters affect the procedure and possibility to match the aforementioned equation to experimental data.

Low Cycle Fatigue Behavior of Alloy 800H Base Metal and Weldments at 700°C

2018 ◽  
Author(s):  
Seon-Jin Kim ◽  
Rando Tungga Dewa ◽  
Woo-Gon Kim ◽  
Eung-Seon Kim
Keyword(s):  
Base Metal ◽  
Deformation Behavior ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Fatigue Tests ◽  
Total Strain ◽  
Cycle Fatigue ◽  
Alloy 800H ◽  
Total Strain Range

Alloy 800H is currently being considered as one of the near-term candidate materials for design and construction of some major high temperature components of a very high temperature reactor (VHTR). System start-ups and shut-downs as well as power transients will produce low-cycle fatigue loadings of components. The aim of this work is to study the low cycle fatigue behavior of Alloy 800H base metal and weldments at 700°C. The weldment specimens were machined from gas tungsten arc welding (GTAW) butt-welded plate such that the loading direction was oriented transverse to the welding direction. Fully reversed total-strain controlled low-cycle fatigue tests have been performed at total strain ranges of 0.6, 0.9, 1.2 and 1.5%. For all the low-cycle fatigue tests, triangular test waveforms with a constant strain rate of 10−3/s were applied. Low-cycle fatigue testing was conducted in accordance with ASTM Standard E606 on servo-hydraulic test machines. And also, creep-fatigue experiments were carried out at 700°C employing 0.6% total strain range and 10−3/s strain rate using trapezoidal waveform with tension hold time. The main focus is to characterize the low-cycle fatigue properties for Alloy 800H weldment specimens from the cyclic deformation behavior and fatigue fracture behavior. The cyclic deformation behavior was influenced by total strain range and material property. The fatigue life was decreased with increasing the total strain range for both base metal and weldment. However, the lives of weldment specimens have a longer life than that of base metal at lower total strain ranges. It was also observed that creep effects play a significant role in fatigue life reduction.

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