scholarly journals Modelling of Fatigue Crack Growth in Inconel 718 under Hold Time Conditions - Application to a Flight Spectrum

2014 ◽  
Vol 891-892 ◽  
pp. 759-764 ◽  
Author(s):  
Erik Lundström ◽  
Kjell Simonsson ◽  
Tomas Månsson ◽  
David Gustafsson
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Model Simulation ◽  
Hold Time ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Propagation Model ◽  
Load Spectrum ◽  
Damaged Zone ◽  
Continuous Power

Gas turbine operating cycles at high temperatures often consist of load reversals mixed with hold times; the latter occurring either as cruise for aero engines or at continuous power output for land based turbines, but also at low frequency loading conditions, e.g. slow “ramp up” of engine thrust. The hold time conditions cause the crack to grow by intergranular fracture due to material damage near the crack tip, thus rapidly increasing the crack growth rate. Since the damaged zone will affect the crack propagation rate due to cyclic loadings as well, the complete load history of a component therefore has to be considered. The crack propagation model presented in this paper is based on the damaged zone concept, and considers the history effect in the form of damaged zone build up during hold times, and subsequent destruction as the crack propagates onwards by rapidly applied load reversals. By incorporating crack closure for handling different R-values, an aero engine component spectrum is evaluated for a surface crack at 550 °C. The result shows a good correlation to model simulation, despite the complexity of the load spectrum.

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.

Comparison of Oscillography Impact Properties between a New Type Drilling Collar Steel and 4145H

2012 ◽  
Vol 463-464 ◽  
pp. 435-438
Author(s):  
Fei Liu ◽  
De Zhi Zeng ◽  
Jian Hong Fu ◽  
Xiao Ming Li ◽  
Fu Zhi Lv ◽  
...  
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Propagation ◽  
Crack Growth ◽  
Impact Energy ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Energy Impact ◽  
New Type ◽  
Lower Temperature

Average impact energy of 4145H steel and X new type drilling collar steel satisfied the standard of “SYT5144-2007 Drilling collar” and “API SPEC7”. With temperature getting down, impact energy of 4145H steel decreased, impact energy Cof X drilling collar steel is a lot higher than 4145H steel, crack propagation energy and crack propagation energy/impact energy ratio decreased. Lower temperature leads to higher crack propagation rate. The crack propagation energy of 4145H is lower than X drilling collar steel. The crack propagation energy/impact energy ratios of X drilling collar steel are at least 3% higher than 4145H for different temperature. In drilling, crack growth rate in X DC was slower than 4145H DC, crack growth rate was fast, and the DC was easy to fracture in low temperature

scholarly journals Introduction of Fatigue Markers in Full Scale Fatigue Test of an Aircraft Structure

2012 ◽  
Vol 2012 (4) ◽  
pp. 29-37 ◽  
Author(s):  
Andrzej Leski ◽  
Sylwester Kłysz ◽  
Janusz Lisiecki ◽  
Gabriel Gmurczyk ◽  
Piotr Reymer ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Test ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Full Scale ◽  
Life Assessment ◽  
Load Spectrum ◽  
Preliminary Load ◽  
Different Levels

Abstract Air Force Institute of Technology participates in the service life assessment programme SEWST. The aim of this programme, funded by the Polish Ministry of Defense, is to modify the operation system of PZL-130 "Orlik" TC-II turbo propelled trainer aircraft. The structural part of the programme is focused on the Full Scale Fatigue Test of the whole airframe to be conducted at the VZLU in the Czech Republic. The load spectrum for the test was developed by the AFIT based on the flight test results. The basic load block represents 200 simulated flight hours and consists of 194 flights showing different levels of severity. At the end of the Full Scale Fatigue Test a teardown inspection is planned during which it would be most beneficial to be able to determine crack propagation rate by means of a crack surface inspection. Markers are usually visible on most fatigue crack surfaces, however they occur randomly therefore it is almost impossible to conclude anything about the crack history. Since the preliminary load block consisted of separate flights (flight loads together with landing and taxing loads) showing significantly different levels of severity, the easiest way to modify the load block was to change the order of flights within the block. Hence a pilot programme was started at the AFIT which was focused on the determination of the influence of flight sequence on crack appearance. Several load blocks were determined using various techniques of rearranging the order of flights within the preliminary load spectrum. This approach ensured the preservation of the initial severity of the load block and simultaneously enabled a significant increase in the probability of the markers occurrence introducing neither artificial underloads nor overloads that would most probably affect the crack propagation rate. Fatigue crack surfaces were inspected using Scanning Electron Microscope. As a result of the investigations a series of images were obtained showing the specimen microstructure with visible markers arranged in the desired sequences. Based on the obtained pictures the most promising load block arrangements were chosen for the Full Scale Fatigue Test.

Fatigue Crack Propagation in 8- and 22-Layer 7075-T6 Aluminum Alloy Laminates

1978 ◽  
Vol 100 (1) ◽  
pp. 32-38 ◽  
Author(s):  
N. J. Pfeiffer ◽  
J. A. Alic
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Crack Propagation Rate ◽  
Crack Arrest ◽  
Propagation Rate ◽  
Adhesively Bonded ◽  
Crack Divider ◽  
Crack Growth Rates

Rates of fatigue crack propagation have been determined for adhesively bonded 7075-T6 laminates having a crack divider geometry. Two lamina thicknesses were used, the resulting laminates having either 8 or 22 layers. Crack growth rates were generally within the same range as for monolithic 7076-T6 alloy, and were somewhat slower in the 22-layer laminates than in those with 8 layers. Instances of decreasing crack propagation rate with increasing stress intensity amplitude, as well as of crack arrest, were observed. These are interpreted in terms of interactions between the layers during the progressive transition from a flat mode of crack growth to a slant mode.

scholarly journals Crystallographic crack propagation rate in single-crystal nickelbase superalloys

2018 ◽  
Vol 165 ◽  
pp. 13012
Author(s):  
Christian Busse ◽  
Frans Palmert ◽  
Paul Wawrzynek ◽  
Björn Sjödin ◽  
David Gustafsson ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Growth ◽  
Driving Force ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Mode I ◽  
Force Parameter ◽  
Intensity Factors ◽  
Crack Driving Force

Single-crystal nickel-base superalloys are often used in the hot sections of gas turbines due to their good mechanical properties at high temperatures such as enhanced creep resistance. However, the anisotropic material properties of these materials bring many difficulties in terms of modelling and crack growth prediction. Cracks tend to switch cracking mode from Mode I cracking to crystallographic cracking. Crystallographic crack growth is often associated with a decrease in crack propagation life compared to Mode I cracking and this must be taken into account for reliable component lifing. In this paper a method to evaluate the crystallographic crack propagation rate related to a crystallographic crack driving force parameter is presented. The crystallographic crack growth rate is determined by an evaluation of heat tints on the fracture surface of a specimen subjected to fatigue loading. The complicated crack geometry including two crystallographic crack fronts is modelled in a three dimensional finite element context. The crack driving force parameter is determined by calculating anisotropic stress intensity factors along the two crystallographic crack fronts by finite-element simulations and post-processing the data in a fracture mechanics tool that resolves the stress intensity factors on the crystallographic slip planes in the slip directions. The evaluated crack propagation rate shows a good correlation for both considered crystallographic cracks fronts.

scholarly journals The Mechanism of Creep during Crack Propagation of a Superalloy under Fatigue–Creep–Environment Interactions

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4418
Author(s):  
Minqing Wang ◽  
Jinhui Du ◽  
Qun Deng
Keyword(s):  
Fatigue Crack ◽  
High Temperature ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Fatigue Cracks ◽  
Hold Time ◽  
Propagation Rate ◽  
Stress Intensity Factor Range

In this study, we examine the mechanism of fatigue-crack propagation in 718Plus superalloy at 704 °C under fatigue–creep–environment interactions, in this case, a new turbine disc material used in aero-engines at high temperatures. The effect of creep on the fatigue-crack propagation of the superalloy at high temperature was also researched. There was an unusual inhibitory effect on the propagation of fatigue cracks in 718Plus alloy, in which the propagation rate of fatigue cracks decreased with the increase of creep time through exploration of dwell-fatigue-crack growth (DFCG) test with different creep times. In particular, under lower stress intensity factor range (ΔK) conditions, the fatigue-crack growth rate with a 90 s hold-time was one order of magnitude lower than that with a 5 s hold-time. Conversely, the gap between the two DFCGs gradually decreased with the increase of ΔK and the creep effect became less apparent. The mechanism of crack propagation in 718Plus alloy under two creep conditions was investigated from a viewpoint of the microstructure, oxidation rate at high temperature and crack path morphology under different conditions.

J-Integral Approach to Creep-Fatigue Crack Propagation in Lead-Free Solder under Various Loading Waveforms

2014 ◽  
Vol 891-892 ◽  
pp. 365-370 ◽  
Author(s):  
Keisuke Tanaka ◽  
Takashi Fujii ◽  
Kazunari Fujiyama
Keyword(s):  
Crack Propagation ◽  
Power Function ◽  
Hold Time ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Creep Crack ◽  
Creep Fatigue ◽  
Integral Range ◽  
Free Solder ◽  
Creep Fatigue Crack

Crack propagation tests of lead-free solder were conducted at room temperature in air using center-notched plates under load-controlled conditions with three waveforms: triangular pp waveform having fast loading and unloading rates, cp-h waveform having a hold time under tension, and cc-h waveform having a hold time under tension and compression. The J integral was evaluated from load-displacement curves. For fatigue loading of pp waveform, the crack propagation rate was expressed as a power function of the fatigue J-integral range. The creep component due to the hold time greatly accelerated the crack propagation rate. The creep crack propagation rate was found to be a power function of the creep J integral range for each case of cp-h and cc-h waveforms. The creep crack propagation rate for cp-h waveform was higher than that for cc-h waveform. Displacement-controlled tests were also performed under four triangular strain waveforms: pp, cp, cc and pc. For the case of pp waveform, the crack propagation rate was also expressed as the same power function of the fatigue J integral range as in the case of load-controlled tests. The creep crack propagation rate was expressed as a power function of the creep J integral range for each case of cp, pc and cc waveforms. Microscopic observations were conducted to clarify micromechanisms of creep-fatigue crack propagation.

Sign in / Sign up

Export Citation Format

Share Document