scholarly journals Different methods to detect fatigue crack nucleation and growth rate

2019 ◽  
Vol 16 (2) ◽  
pp. 103-109
Author(s):  
Sergio Baragetti
Keyword(s):  
Crack Growth ◽  
Crack Nucleation ◽  
Numerical Models ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Nucleation ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Rate Evaluation ◽  
Crack Nucleation And Growth

This paper reports a short summary of some procedures that allow to evaluate crack growth propagation rate. Numerical models developed using the equations of linear elastic fracture mechanics are described. Confirmation of the numerical results needs comparison with experimental results. The crack replica method and crack growth gages application are reported and prove to be powerful tools for crack propagation rate evaluation.

An Approach for Fatigue Life Prediction

2005 ◽  
Author(s):  
Yanyao Jiang ◽  
Fei Ding ◽  
Miaolin Feng
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Stress Analysis ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Crack Nucleation ◽  
Nucleation And Growth ◽  
Basic Rule ◽  
Fatigue Crack Nucleation ◽  
Crack Nucleation And Growth

Fatigue damage is generally described as the nucleation and growth of cracks to final failure. These two stages of fatigue damage are often modeled with completely different methods with no quantitative relationships between them. In addition, a number of fitting parameters are needed in order to consider different effects. The current work is aimed to develop a robust approach for the prediction of fatigue life from crack initiation to final fracture. The approach bridges the gap between the crack nucleation and growth regions. Based upon the conception that fatigue damage is directly related to the stresses and strains inside the material, it is assumed that both crack nucleation and crack growth are governed by the same fatigue damage mechanisms and a single fatigue damage criterion can model both stages. A basic rule is that any material point fails to form a fresh crack if the total accumulated fatigue damage reaches a limit. Crack growth is treated as a process of continuous crack nucleation without using the stress intensity factor or J-integral concept. The approach consists of two steps: stress analysis and fatigue damage prediction. Elastic-plastic stress analysis is conducted for the component to obtain the detailed stress-strain responses. By using a general fatigue criterion, fatigue crack nucleation and growth are predicted. Notched specimens made of 1070 steel were experimentally tested from crack initiation till fracture. The approach was applied to predict the fatigue life of 1070 steel and the predicted fatigue lives were in excellent agreement with the experimental observations.

Handling Uncertainty in the Remnant Fatigue Life Assessment of Offshore Process Pipework

2016 ◽  
Author(s):  
Arvind Keprate ◽  
R. M. Chandima Ratnayake
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Life Assessment ◽  
Assessment Process ◽  
Linear Elastic ◽  
Fatigue Life Assessment ◽  
Process Piping ◽  
Growth Laws ◽  
Elastic Fracture ◽  
Offshore Industry

A typical procedure for a remnant fatigue life (RFL) assessment is stated in the BS-7910 standard. The aforementioned standard provides two different methodologies for estimating RFL; these are: the S-N curve approach and the crack growth laws (i.e. using Linear Elastic Fracture Mechanics (LEFM) principles) approach. Due to its higher accuracy, the latter approach is more commonly used for RFL assessment in the offshore industry. Nevertheless, accurate prediction of RFL using the deterministic LEFM approach (stated in BS-7910) is a challenging task, as RFL prediction is afflicted with a high number of uncertainties. Furthermore, BS-7910 does not provide any recommendation in regard to handling the uncertainty in the deterministic RFL assessment process. The most common way of dealing with the aforementioned uncertainty is to employ Probabilistic Crack Growth (PCG) models for estimating the RFL. This manuscript explains the procedure for addressing the uncertainty in the RFL assessment of process piping with the help of a numerical example. The numerically obtained RFL estimate is used to demonstrate a calculation of inspection interval.

Study on the Influence of Crack Growth Behavior on Fatigue Life in Simulated Reactor Coolant Environment of Different Temperature

2020 ◽  
Author(s):  
Tatsuru Misawa ◽  
Takanori Kitada ◽  
Takao Nakamura
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Reactor Coolant ◽  
Different Temperatures

Abstract It has been clarified that the fatigue life is decreased in the fatigue test of high-temperature and high-pressure water that simulates PWR reactor coolant environment compared to that in the atmosphere. Temperature, strain rates, dissolved oxygen concentration, etc. affect the decrease of fatigue life. The influence of crack growth behavior on the fatigue life of Type 316 austenitic stainless steel [1] in simulated PWR reactor coolant environment of different temperatures was investigated in this study. Fatigue tests were conducted under different temperatures (200°C and 325°C) in a simulated PWR reactor coolant environment with interrupting, and cracks generated on the specimen surface were observed with two-step replica method. From the results of observation, the influence of crack growth behavior in different temperatures on the fatigue life was clarified. As a result, it was confirmed that the decrease of the fatigue life due to high temperature is mainly caused by the acceleration of crack propagation rate in the depth direction by the increase of crack coalescence frequency due to the increase of crack initiation number and crack propagation rate in the length direction.

Simulation of Cracks in Fiber Reinforced Composite Plate

2011 ◽  
Vol 471-472 ◽  
pp. 892-897 ◽  
Author(s):  
Pramod Kumar ◽  
Ashish Kakyal
Keyword(s):  
Cyclic Loading ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fem Analysis ◽  
Strain Energy Release ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fiber Reinforced ◽  
Automotive Parts ◽  
Mechanical Approach

Material flaws, pre-cracks and crack initiation due to cyclic loading often lead to undetected crack propagation in commercial structures like aircraft components, automotive parts and computer motherboard. Cyclic loading can make the crack grow large into any shape with an arbitrary orientation, depending on the structure geometry, boundary and loading conditions. Since crack propagation in many cases may lead to catastrophic failure with human and monetary loss as a result, it is important to enable crack growth prediction at all stages of development and during maintenance in order to prevent such scenarios. Micro mechanical approach is used for modelling the crack in composite materials. Crack propagation in a single edge crack plate is carried out by using FEM analysis. 2D model is analysed to determine the crack growth. The crack propagation rate, stress intensity factor and strain energy release rate are predicted by varying the crack length in fiber reinforced epoxy composite using NISA/ENDURE.

FATIGUE CRACK GROWTH BEHAVIOR OF STAINLESS STEEL COATED WITH TiN FILM

2012 ◽  
Vol 06 ◽  
pp. 282-287
Author(s):  
SATOSHI FUKUI ◽  
DAISUKE YONEKURA ◽  
RI-ICHI MURAKAMI
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Crack Growth Behavior ◽  
Tin Film

In our previous study, we examined the influence of the fatigue properties of the stainless steel coated with TiN film and clarified the influence of TiN coating and the surface roughness on the fatigue property. In this study, the four point bending fatigue crack growth tests were carried out for martensitic stainless steel coated with TiN film deposited by arc ion plating method in order to investigate the effect of surface finishing on the fatigue crack behavior for film coated material. The fatigue crack growth behavior was evaluated using the replica method. As a result, the crack propagation rate of mirror polished specimens were lower than that of rough surface specimens. The crack propagation rate was especially decreased for TiN coatings deposited on the mirror polished substrate. The surface roughness near the crack initiation site increased after fatigue test. It concludes that the surface roughness of substrate influences crack propagation rate and the deposition of TiN film affected influenced crack propagation rate and fatigue strength when the surface roughness of substrate is small enough.

The Growth Rate of Semi-Elliptic Fatigue Cracks in Thick-Walled Cylinders

1983 ◽  
Vol 22 ◽  
Author(s):  
W. A. Lees ◽  
P. S. J. Crofton
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Internal Pressure ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Low Alloy Steel ◽  
Linear Elastic ◽  
Fatigue Data ◽  
Elastic Fracture ◽  
Crack Growth Rates

ABSTRACTThe rate of growth of fatigue cracks originating at the bore and at the outside surface of thick-walled low alloy steel cylinders has been measured for cylinders subjected to fluctuating internal pressure.Analysis of the results using linear elastic fracture mechanics relationships shows that crack growth rates found in air adequately predict the behaviour of cracks growing from the outside surface of a cylinder.Fatigue cracks growing from the bore of a cylinder subjected to fluctuating internal pressure are found to advance at a consistently higher rate than that predicted from crack growth rate tests carried out in air.These findings are discussed in relation to the proposed adoption of existent strain-life fatigue data for pressure vessel design.

Sign in / Sign up

Export Citation Format

Share Document