Modeling the Effects of Damage and Microstructural Evolution on the Creep Behavior of Engineering Alloys

2000 ◽  
Vol 122 (3) ◽  
pp. 273-278 ◽  
Author(s):  
M. McLean ◽  
B. F. Dyson
Keyword(s):  
Creep Behavior ◽  
Damage Mechanics ◽  
Complex Loading ◽  
Phase Changes ◽  
Life Assessment ◽  
Engineering Alloys ◽  
Improved Design ◽  
Remaining Life Assessment ◽  
Aging Phenomena ◽  
Evolution Of Microstructure

A quantitative representation of the creep behavior of materials is required to determine the operating lives of high temperature plant. Although the creep performance of such materials is normally governed by the development of microstructural features that can either be associated with the normal aging phenomena or by the development of damage in the material, most previous analyses of creep data have been empirical. It has been implicitly assumed that similar forms of creep curves can be adequately represented by a single generic equation. However, it is clear that different materials are subject to different combinations of structural change during their creep lives (e.g., cavitation/cracking, particle coarsening, phase changes, dislocation accumulation) all of which can influence the creep performance. An empirical representation can always be made to fit an available database, but effective extrapolation to longer lives and more complex loading conditions requires that the differing mechanisms be integrated in the creep equations. This paper will explore the implications of the evolution of microstructure and damage on the creep performance of a range of materials and will consider the potential of a microstructure-based state-variable (or damage-mechanics) approach for improved design life prediction of new plant and remaining life assessment of geriatric plant. [S0094-4289(00)00603-4]

Elevated-Temperature Life Assessment

2021 ◽  
pp. 146-166
Author(s):  
Arun Sreeranganathan ◽  
Douglas L. Marriott
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Stress Relaxation ◽  
Damage Mechanics ◽  
Elevated Temperatures ◽  
Constitutive Models ◽  
Life Assessment ◽  
Remaining Life ◽  
High Temperature Components ◽  
Remaining Life Assessment

Abstract This article provides some new developments in elevated-temperature and life assessments. It is aimed at providing an overview of the damage mechanisms of concern, with a focus on creep, and the methodologies for design and in-service assessment of components operating at elevated temperatures. The article describes the stages of the creep curve, discusses processes involved in the extrapolation of creep data, and summarizes notable creep constitutive models and continuum damage mechanics models. It demonstrates the effects of stress relaxation and redistribution on the remaining life and discusses the Monkman-Grant relationship and multiaxiality. The article further provides information on high-temperature metallurgical changes and high-temperature hydrogen attack and the steps involved in the remaining-life prediction of high-temperature components. It presents case studies on heater tube creep testing and remaining-life assessment, and pressure vessel time-dependent stress analysis showing the effect of stress relaxation at hot spots.

The Application of Physically Based CDM Modeling in Prediction of Materials Properties and Component Lifetime

2004 ◽  
Vol 126 (3) ◽  
pp. 369-375 ◽  
Author(s):  
J. Yang ◽  
J. S. Hsiao ◽  
M. Fong ◽  
T. B. Gibbons
Keyword(s):  
Creep Behavior ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Element Model ◽  
State Variables ◽  
Damage State ◽  
Alloy Steels ◽  
Engineering Alloys ◽  
Made In

Since the early empirically based work of Kachanov and Robotnov substantial progress has been made in developing the concept of Continuum Damage Mechanics (CDM) as a tool for predicting material and component behavior in the creep regime. The key element in this process has been the progress that has been made in understanding and quantifying the physics of deformation and fracture in engineering alloys for high temperature service. In this paper, the application of the CDM methodology has been demonstrated in the prediction of the creep behavior of alloy steels for boiler pressure parts and for predicting the life to failure of model components and tubular testpieces operating in creep conditions. A model incorporating two damage state variables formed the basis of the methodology for creep behavior and a multi-axial variant of the model was used for the component life prediction. The important development described in this work has been the use of a simplifying procedure in dealing with damaged elements in the finite-element model, so that the analysis for component life prediction can be carried out on a personal computer rather than the large mainframe computers used previously. This greatly increases the usefulness of the procedure for practical design applications. The results show that the CDM methodology can be applied successfully in these important applications and will give much more satisfactory agreement with experiment than existing less robust methods. In addition the failure profile of the tubular testpieces can be accurately represented and this is a feature unique to the CDM approach.

scholarly journals Continuum Damage Mechanics Modeling of Creep in DS GTD-111TM Superalloy

2011 ◽  
Vol 278 ◽  
pp. 234-240
Author(s):  
Sanjay Kumar Sondhi ◽  
Gaurav Singh ◽  
Francesco Mastromatteo
Keyword(s):  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Life Assessment ◽  
Creep Model ◽  
Model Parameters ◽  
Microstructural Parameters ◽  
Component Design ◽  
Remaining Life Assessment ◽  
Term Creep ◽  
Kinetics Of

Safe extrapolation of short-term creep data requires development of creep models where (a) the constitutive laws are physics based, and (b) majority of model parameters are calculated rather than empirically fitted. This paper details the structure of such a physics-based creep model and its application to DS GTD-111TM superalloy. The constitutive creep law is derived from the kinetics of dislocation-particle interactions in the presence of thermal activation. This constitutive creep law is further coupled with the evolution kinetics of controlling microstructural parameters and associated damages. The model is expected to provide vital inputs for component design as well as remaining life assessment. (GTD-111TM is a trademark of the General Electric Company).

Assessment of the Effect of Pitting Corrosion on Fatigue Crack Initiation in Hydro Turbine Shaft

2013 ◽  
Vol 633 ◽  
pp. 186-196 ◽  
Author(s):  
Radivoje Mitrovic ◽  
Dejan Momcilovic ◽  
Ivana Atanasovska
Keyword(s):  
Pitting Corrosion ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Critical Distance ◽  
Life Assessment ◽  
Stress Concentrations ◽  
Hydro Power ◽  
Turbine Shaft ◽  
Improved Design ◽  
Material Length

Energy efficiency is a key issue worldwide, and not confined solely to the realm of engineers. Past failures of mechanical power system components must be examined carefully in order to minimise future occurrences and increase energy efficiencies. Improved design procedures have been highly sought by engineers and researchers over the past few decades. The latest verified method with strong application potential within the power industry is that of the Theory of Critical Distances (TCD). TCD is not one method, but a group of methods that have a common feature; the use of a characteristic material length parameter, the critical distance L, for calculating the influence of notch-like stress raisers under static and fatigue loading. A case study from a hydro power plant turbine shaft was chosen to illustrate the development of this methodology. The paper illustrates the application of TCD to the fatigue life assessment of a turbine shaft with stress concentrations due to pitting corrosion.

Structural Response and Remaining Life of Damaged Composites

2015 ◽  
Vol 813-814 ◽  
pp. 106-110
Author(s):  
Dalbir Singh ◽  
C. Ganesan ◽  
A. Rajaraman
Keyword(s):  
Hybrid Approach ◽  
Experimental Studies ◽  
Structural Response ◽  
Material Behavior ◽  
Experimental Results ◽  
Life Assessment ◽  
Nonlinear Material ◽  
Remaining Life ◽  
Design Effectiveness ◽  
Remaining Life Assessment

Composites are being used in variety of applications ranging from defense and aircraft structures, where usage is profuse, to vehicle structures and even for repair and rehabilitation. Most of these composites are made of different laminates glued together with matrix for binding and now-a-days fibers of different types are embedded in a composite matrix. The characterizations of material properties of composites are mostly experimental with analytical modeling used to simulate the system behavior. But many times, the composites develop damage or distress in the form of cracking while they are in service and this adds a different dimension as one has to evaluate the response with the damage so that its performance during its remaining life is satisfactory. This is the objective of the present study where a hybrid approach using experimental results on damaged specimens and then analytical finite element are used to evaluate response. This will considerably help in remaining life assessment-RLA- for composites with damage so that design effectiveness with damage could be assessed. This investigation has been carried out on a typical composite with carbon fiber reinforcements, manufactured by IPCL Baroda (India) with trade name INDCARF-30. Experimental studies were conducted on undamaged and damaged specimens to simulate normal continuous loading and discontinuous loading-and-unloading states in actual systems. Based on the experimental results, material characterization inputs are taken and analytical studies were carried out using ANSYS to assess the response under linear and nonlinear material behavior to find the stiffness decay. Using stiffness decay RLA was computed and curves are given to bring the influence of type of damage and load at which damage had occurred.

scholarly journals The thermal history and stress state of a fresh steam-pipeline influencing its remaining service life

2011 ◽  
Vol 15 (3) ◽  
pp. 691-704 ◽  
Author(s):  
Gordana Bakic ◽  
Vera Sijacki-Zeravcic ◽  
Milos Djukic ◽  
Stevan Maksimovic ◽  
Dusan Plesinac ◽  
...  
Keyword(s):  
Service Life ◽  
Elevated Temperatures ◽  
Operating Temperature ◽  
Life Assessment ◽  
Temperature History ◽  
Significant Variable ◽  
Remaining Life ◽  
Pipe Bend ◽  
Steam Pipeline ◽  
Remaining Life Assessment

The service life of thick-walled power plant components exposed to creep, as is the case with pipelines of fresh- and re-heated steam, depend on the exhaustion rate of the material. Plant operation at elevated temperatures and at temperatures below designed temperatures all relates to the material exhaustion rate, thus complicating remaining life assessment, whereas the operating temperature variation is a most common cause in the mismatching of real service- and design life. Apart from temperature, the tube wall stress is a significant variable for remaining life assessment, whose calculation depends on the selected procedure, due to the complex pipeline configuration. In this paper, a remaining life assessment is performed according to the Larson-Miller parametric relation for a ?324?36 pipe bend element of a fresh steam-pipeline, made of steel class 1Cr0.3Mo0.25V, after 160 000 hours of operation. The temperature history of the pipeline, altogether with the pipe bend, is determined based on continuous temperature monitoring records. Compared results of remaining life assessment are displayed for monitored temperature records and for designed operating temperature in the same time period. The stress calculation in the pipe bend wall is performed by three methods that are usually applied so to emphasize the differences in the obtained results of remaining life assessment.

Finite Element Simulation of the Creep Behavior of 2.25Cr-1Mo-0.25V Steel Based on Continuum Damage Mechanics

2015 ◽  
Vol 750 ◽  
pp. 266-271 ◽  
Author(s):  
Yu Zhou ◽  
Xue Dong Chen ◽  
Zhi Chao Fan ◽  
Yi Chun Han
Keyword(s):  
Genetic Algorithm ◽  
Finite Element ◽  
Creep Behavior ◽  
Constitutive Equations ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Element Simulation

The creep behavior of 2.25Cr-1Mo-0.25V ferritic steel was investigated using a set of physically-based creep damage constitutive equations. The material constants were determined according to the creep experimental data, using an efficient genetic algorithm. The user-defined subroutine for creep damage evolution was developed based on the commercial finite element software ANSYS and its user programmable features (UPFs), and the numerical simulation of the stress distribution and the damage evolution of the semi V-type notched specimen during creep were studied. The results showed that the genetic algorithm is a very efficient optimization approach for the parameter identification of the creep damage constitutive equations, and finite element simulation based on continuum damage mechanics can be used to analyze and predict the creep damage evolution under multi-axial stress states.

Comparative Study on Remaining Life Assessment of a Pressure Vessel, Working in Severe Conditions, Based on Results of Metallographic Replicas and Creep Tests

2021 ◽  
Vol 1164 ◽  
pp. 67-75
Author(s):  
Iuliana Duma ◽  
Alin Constantin Murariu ◽  
Aurel Valentin Bîrdeanu ◽  
Radu Nicolae Popescu
Keyword(s):  
Stainless Steel ◽  
Life Assessment ◽  
Petrochemical Plant ◽  
Remaining Life ◽  
Creep Tests ◽  
Experimental Creep ◽  
Asme Code ◽  
Remaining Life Assessment ◽  
Service Duration ◽  
Made In

The paper presents and compares the results on the reliability and remaining life assessment of a reactor (coxing box) from a petrochemical plant. The reactor shell is made of 16Mo5 (W1.5423) steel, with a thickness of 25 mm, plated with 3 mm thick X6CrAl13 (W1.4002) stainless steel. The assessment was made in two steps. For preliminary remnant life assessment, specifications of section VII of the ASME code was used followed by iRiS‑Thermo expert system. Further, experimental creep and metallographic replica analysis were performed. Results comparison of the two methods applied revealed a reduction of the preliminary estimated remaining live obtained using metallographic replica analysis. Based on the results obtained, the possibility to extend the service duration of the coxing box in the safety condition, using current process parameters, with of 20.000 hours was highlighted.

Sign in / Sign up

Export Citation Format

Share Document