Thermo-Mechanical Fatigue Life of Coke Drum Skirt Attachment Designs

2016 ◽  
Author(s):  
Gurumurthy Kagita ◽  
Balaji Srinivasan ◽  
Penchala Sai Krishna Pottem ◽  
Gudimella G. S. Achary ◽  
Subramanyam V. R. Sripada
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Effective Strain ◽  
Analysis Model ◽  
Transfer Coefficients ◽  
Elastic Plastic ◽  
Mechanical Fatigue ◽  
Section Viii ◽  
Thermocouple Temperature ◽  
Transient Thermal

Skirt to bottom head attachments of coke drums experience severe thermo-mechanical cyclic stresses, causing failures due to low cycle fatigue. Accordingly, many skirt attachment designs have evolved over a period of time starting with simple conventional weld build up design, improved weld build up design, integral forged attachment design and others. The objective of this paper is to compare thermo-mechanical fatigue life of three different skirt attachment designs using elastic-plastic fatigue assessment methods of ASME Section VIII, Division 2. A transient thermal analysis model is first developed incorporating appropriate boundary conditions. The time-dependent variable heat transfer coefficients at the inner surface of the coke drum, which change with the operation stages and the levels of oil filling and water quenching, are determined based on the field measured thermocouple temperature data on the outer surface of the coke drum. Sequentially coupled elastic-plastic transient thermo-mechanical stress analyses of coke drum skirt attachments are carried out using both Twice Yield and cycle-by-cycle methods. The effective strain ranges and the fatigue life of three different skirt attachment designs are calculated and compared.

A Novel Fatigue Evaluation Approach with Direct Steady Cycle Analysis (DSCA) Based on the Linear Matching Method (LMM)

2019 ◽  
Vol 795 ◽  
pp. 383-388 ◽  
Author(s):  
Xiao Tao Zheng ◽  
Zhi Yuan Ma ◽  
Hao Feng Chen ◽  
Jun Shen
Keyword(s):  
Fatigue Life ◽  
Evaluation Method ◽  
Low Cycle Fatigue ◽  
Effective Strain ◽  
Strain Range ◽  
Matching Method ◽  
Evaluation Approach ◽  
Perfectly Plastic ◽  
Fatigue Evaluation ◽  
Linear Matching Method

The traditional Low Cycle Fatigue (LCF) evaluation method is based on elastic analysis with Neuber’s rule which is usually considered to be over conservative. However, the effective strain range at the steady cycle should be calculated by detailed cycle-by-cycle analysis for the alternative elastic-plastic method in ASME VIII-2, which is obviously time-consuming. A Direct Steady Cycle Analysis (DSCA) method within the Linear Matching Method (LMM) framework is proposed to assess the fatigue life accurately and efficiently for components with arbitrary geometries and cyclic loads. Temperature-dependent stress-strain relationships considering the strain hardening described by the Ramberg-Osgood (RO) formula are discussed and compared with those results obtained by the Elastic-Perfectly Plastic (EPP) model. Additionally, a Reversed Plasticity Domain Method (RPDM) based on the shakedown and ratchet limit analysis method and the DSCA approach within the LMM framework (LMM DSCA) is recommended to design cyclic load levels of LCF experiments with predefined fatigue life ranges.

Life Assessment of a Coke Drum by Using the Thermal-Mechanical Fatigue Properties and Laser Scanning Approach

2020 ◽  
Author(s):  
Zhiyuan Han ◽  
Guoshan Xie ◽  
Zengchao Wang ◽  
Jianzhong Yin ◽  
Jin Shi
Keyword(s):  
Fatigue Life ◽  
Laser Scanning ◽  
Low Cycle Fatigue ◽  
Complex Loading ◽  
Operating Conditions ◽  
Life Assessment ◽  
Fatigue Properties ◽  
Element Analysis ◽  
Thermal Mechanical Fatigue ◽  
Mechanical Fatigue

Abstract Coke drums are critical equipments in delayed coking plants, which are operated under severe thermal-mechanical conditions by cyclic heating and quenching processes. Cracks are usually developed during service because of severe plastic deformation and low-cycle fatigue. Thus, the assessment of the deformation severity and remaining life is important for safety operating of the coke drums. This study investigated the bulging damage and fatigue life of 6 coke drums after 16 years and 22 years of service in China. A thermal-mechanical fatigue test were first performed to simulate complex loading condition experienced by the coke drum. The thermal-mechanical fatigue life curve of the fabrication material was obtained. Then, a internal laser scanning was employed to measure the deformation and bulges of drum shells. The finite element analysis was developed to calculate the cyclic stress and strain and bulging severity based on the laser mapping and operating conditions. The fatigue life of the coke drum was assessed by the Coffin-Manson-Basquin’s relationship. The life evaluation results of different methods were compared and analyzed. The results showed that a reasonable life of the coke drum can be obtained by using the thermal-mechanical fatigue properties and laser scanning approach.

Low Cycle Fatigue Behavior of Welded Components: A New Approach — Experiments and Numerical Simulation

2012 ◽  
Author(s):  
Eliane Lang ◽  
Jürgen Rudolph ◽  
Thomas Beier ◽  
Michael Vormwald
Keyword(s):  
Fatigue Life ◽  
Thermal Loading ◽  
Weld Seam ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Curve ◽  
Life Assessment ◽  
New Approach ◽  
Elastic Plastic ◽  
Weld Seams

Nuclear power plant components are often subjected to local plastic deformations due to low cycle operational thermal loading conditions. The fatigue behavior of weld seams is of particular interest in this context. Applicable design codes for fatigue life assessment use factors (e.g. Fatigue strength reduction factors – FSRF) within the simplified elastic-plastic or general elastic-plastic analysis in connection with the design fatigue curves for non-welded components. This way, the influence of the weld seam on the fatigue behavior is approximately considered. Emanating from this status quo ideas for a new approach considering the particularities of the fatigue behavior of the weld seam in more detail are developed. The proposed approach is based on material mechanics and constitutes a combination of experimental findings and numerical calculations in order to determine the local strains and the fatigue relevant influence of geometrical and metallurgical notches induced by the weld seam. Experiments on welded specimens provide the fatigue life as well as the stabilized cyclic stress-strain curve as relevant input parameters for the finite element analyses. The proposed model is capable of considering the exact geometry of the weld seam obtained by 3D scanning with very high resolution and the different material strengths due to the weld. The consideration of the principal influences on the fatigue behavior of weld seams paves the way to the application of established damage parameters such as PJ with the future objective to transfer the results also on arbitrary proportional and non-proportional loadings with variable amplitudes.

Thermo-Mechanical Fatigue Behaviour of the Gamma-Titanium Aluminide TNB-V5 with Near-Gamma Microstructure

2007 ◽  
Vol 539-543 ◽  
pp. 1559-1564 ◽  
Author(s):  
M. Roth ◽  
Horst Biermann
Keyword(s):  
Fatigue Life ◽  
Cyclic Deformation ◽  
Gas Turbines ◽  
Titanium Aluminides ◽  
Mechanical Load ◽  
Low Cycle Fatigue ◽  
Fatigue Behaviour ◽  
Attractive Alternative ◽  
Combustion Engines ◽  
Mechanical Fatigue

The efficiency of aircraft and industrial gas turbines and combustion engines depends on the maximum operation temperature and, therefore, on the properties of the commercial high temperature materials. In the temperature range 500°C to 750°C γ-titanium aluminides especially alloys of the third generation represent an attractive alternative to the established nickel-base superalloys which have the double density. Due to superimposed cyclic thermal and cyclic mechanical loadings during start-up and shut-down operations structural components in gas turbines and combustion engines may not only be exposed to isothermal but also to thermo-mechanical fatigue (TMF). In this study the cyclic deformation and fatigue behaviour under thermo-mechanical load of the γ-TiAl alloy TNB-V5 with near-gamma microstructure is evaluated. To set a fatigue-life relation strain-controlled thermo-mechanical fatigue tests were carried out with two different strain ranges, different temperature-strain cycles and different temperature ranges from 400°C to 800°C. Additional low-cycle fatigue (LCF) tests were performed at 400°C, 600°C and 800°C for comparison. Cyclic deformation curves, stress-strain hysteresis loops and fatigue lives of the tests are presented. The shortest fatigue lives are always observed in out-of phase (OP) tests, the longest in in-phase (IP) tests. Clockwise-diamond (CD) and counter-clockwise diamond (CCD) testing yield similar fatigue lives intermediate between those of OP and IP tests. For a general life prediction the double-logarithmic plot of the damage parameter by Smith, Watson and Topper vs. fatigue life is well suitable.

Research on the Dependence between the Fatigue Life of X20CrMoV12.1 and P91 Steels under the Conditions of the Interactions of Thermo-Mechanical and Isothermal Low-Cycle Fatigue

2014 ◽  
Vol 224 ◽  
pp. 93-98
Author(s):  
Anżelina Marek ◽  
Jerzy Okrajni ◽  
Grzegorz Junak ◽  
Mariusz Twardawa
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Engineering Industry ◽  
Power Engineering ◽  
Cycle Fatigue ◽  
Mechanical Fatigue ◽  
Life Values

The paper presents the correlation between fatigue life determined under the conditions of low-cycle fatigue (LCF) and thermo-mechanical fatigue (TMF). Fatigue life values computed using own parameter P and results obtained based on the author’s own research and literature from the publications have been shown. The tests LCF and TMF have been performed for steels used for devices operated in the power engineering industry under the conditions of variable mechanical and thermal interactions X20CrMoV12.1 and P91.

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