The Effects of Carburisation on Creep Response of Stainless Steel Components

2019 ◽  
Author(s):  
J. Cakstins ◽  
R. A. Ainsworth ◽  
M. Su
Keyword(s):  
Stainless Steel ◽  
Steady State ◽  
Material Properties ◽  
Creep Resistance ◽  
Creep Damage ◽  
Stress Fields ◽  
Transient Phase ◽  
Transient Period ◽  
Cylinder Model ◽  
Homogeneous Cylinder

Abstract Stainless steel components in the UK’s Advanced Gas-cooled Reactors can undergo microstructural changes near the surface due to the reactor carbon dioxide environment. Carburisation tends to increase the material’s elastic modulus, yield strength and creep resistance. However, the ductility of the material tends to be reduced. This paper assesses the effect on the component response of the changes in local elastic, plastic and creep material properties resulting from carburisation. A pressurised carburised cylinder is modelled analytically as a set of concentric, creeping homogeneous cylinders. The results show a reduced overall deformation rate in the steady state as expected. For completeness, it is shown quite generally that steady-state deformation in a creeping component is reduced by locally increased creep resistance. The cylinder model, however, shows that the locally increased creep and plastic resistance leads to higher stresses in the carburised region than in a homogeneous cylinder, particularly during the transition before steady-state conditions are established. The transient period before steady state creep is then examined in more detail numerically by allowing the material properties to change due to carburisation during the transient phase. This leads to reduced stresses in the carburised region. The influence of the results on deformation, triaxial stress fields and associated creep damage distributions are examined and used to provide guidance on both component assessment and on evaluation of carburised material properties from deformation measurements on test specimens.

Probabilistic Creep Modeling of 304 Stainless Steel Using a Modified Wilshire Creep-Damage Model

2020 ◽  
Author(s):  
Md. Abir Hossain ◽  
Jaime A. Cano ◽  
Calvin M. Stewart
Keyword(s):  
Stainless Steel ◽  
Monte Carlo ◽  
Temperature Stress ◽  
Creep Deformation ◽  
Material Properties ◽  
Probabilistic Model ◽  
Damage Model ◽  
Creep Damage ◽  
304 Stainless Steel ◽  
Creep Damage Model

Abstract Pressure vessel components subject to high temperature and pressure are susceptible to life-limiting creep and/or creep-induced failure. Traditional continuum damage mechanics (CDM) based creep-damage model are used extensively for the prediction and design against creep in these components. Conventional creep experiments show considerable uncertainty in the creep response of materials where scatter can span decades of creep life. The objective of this paper is to introduce the probabilistic methods into a deterministic creep-damage model in order to predict experimental uncertainty. In this study, a modified Wilshire model capable of creep deformation, damage, and rupture prediction is selected. Creep deformation data for 304 stainless steel is collected from the literature consisting of quintuplicate (five) tests at 600°C with varying stress levels. It is hypothesized that the scatter in creep data is due to: test condition (temperature fluctuations and eccentric loading), initial damage (pre-existing surface and sub-surface defects), and metallurgical (local variation in microstructure) uncertainties. Probability distribution functions (pdfs) and Monte Carlo simulations are applied to introduce the uncertainties into the modified Wilshire equations. The domain of each source of uncertainty must be defined. A systematic calibration approach is followed where the material constant for each creep curve (in the quintuple) are obtained and statistical analysis is performed on the material properties to assess the random distribution associated with each uncertain material parameter. The probabilistic calibration begins with the introduction of test condition randomness (±2°C and ±3.2% MPa of nominal temperature/stress) in accordance with the ASTM standards. Cross calibration of temperature-stress variability proceeds the approximation of initial damage uncertainty which captures the remaining scatter in the data. Deterministic calibration unveils the range of variabilities associated with the material properties. The best-fitted pdfs are assigned to each uncertain parameter and subsequently, the deterministic model is converted into a probabilistic model where reliability is a tunable factor. A large number of Monte Carlo simulation are conducted to generate probabilistic creep deformation, minimum-creep-strain-rate (MCSR), and stress-rupture (SR) predictions. It is demonstrated that the probabilistic model produces quantitatively and qualitatively good fits when compared with experimental data. Future work will be directed towards the inclusion of service condition related uncertainty (power plant, turbine blade, Gen IV nuclear reactor application) into the probabilistic framework where the uncertainties are more robust.

Comparison of Both Creep Resistance and Material Properties of High-Strength Low-Alloy Steel and Stainless Steel

2009 ◽  
Vol 37 (4) ◽  
pp. 102369
Author(s):  
M. R. Mitchell ◽  
R. E. Link ◽  
Josip Brnic ◽  
Domagoj Lanc ◽  
Goran Turkalj ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Alloy Steel ◽  
Material Properties ◽  
Creep Resistance ◽  
High Strength ◽  
Low Alloy Steel

Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Brahmaji Vasantharao
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Life Prediction ◽  
Creep Damage ◽  
Back Pressure ◽  
System Level ◽  
Cyclic Life ◽  
Power Turbine ◽  
The Impact

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine. This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach. Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks. Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives. The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.

Influence of high temperature sodium exposure on microstructure and material properties of AISI 440C Stainless Steel

2022 ◽  
Vol 13 (1) ◽  
pp. 1
Author(s):  
Nashine B.K. ◽  
Jose Varghese ◽  
Sreedhar B. K ◽  
Mariappan K ◽  
Chandramouli S ◽  
...  
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Material Properties

THEORY OF THE TRANSIENT PHASE IN AN ENZYME SYSTEM INVOLVING TWO ENZYME-SUBSTRATE COMPLEXES: THE CASE OF THE FORMATION OF PRODUCTS FROM THE FIRST COMPLEX

1959 ◽  
Vol 37 (4) ◽  
pp. 737-743 ◽  
Author(s):  
Ludovic Ouellet ◽  
James A. Stewart
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Active Site ◽  
Substrate Concentration ◽  
Enzyme System ◽  
Kinetic Scheme ◽  
Enzyme Concentration ◽  
Theoretical Treatment ◽  
Transient Phase ◽  
Enzyme Substrate

A theoretical treatment is worked out for the kinetic scheme[Formula: see text]in which the concentration of P1 is followed. The steady-state and transient phase equations are obtained subject to the condition that the substrate concentration is greatly in excess of the enzyme concentration. The conditions under which evidence in favor of this mechanism can be obtained from experimental data are discussed. Under certain conditions, the weight of the enzyme corresponding to one active site can be determined. Methods for the evaluation of the different constants are described.

Dissimilar Materials Laser Welding Characteristics of Stainless Steel and Titanium Alloy

2013 ◽  
Vol 465-466 ◽  
pp. 1060-1064 ◽  
Author(s):  
Zazuli Mohid ◽  
M.A. Liman ◽  
M.R.A. Rahman ◽  
N.H. Rafai ◽  
Erween Abdul Rahim
Keyword(s):  
Thermal Conductivity ◽  
Stainless Steel ◽  
Titanium Alloy ◽  
Thermal Properties ◽  
Material Properties ◽  
Dissimilar Materials ◽  
Scanning Speed ◽  
Welding Parameters ◽  
Melting Region ◽  
Offset Distance

Welding parameters are directly influenced by the work material properties. Thermal properties such as thermal conductivity and melting point are very important to estimate the range of power required and the allowable scanning speed. However, when two or more different materials are involved, modifying lasing parameters are not enough to counter the problems such as imbalance melting region and weak adhesion of contact surface. To counter this problem, the characteristics of welding beads formation for both materials need to be clarified. In this study, comparison of welding beads constructed using the same scanning parameters were done to understand the different and similarity of melted region for the both materials. Actual welding of the both materials were done under different offset distance to obtain a balanced melting area and well mixed melting region.

Sign in / Sign up

Export Citation Format

Share Document