Study of the Surface Roughness Evolution of Pinned Fatigue Cracks, and its Relation to Crack Pinning Duration and Crack Propagation Rate Between Pinning Points

2017 ◽  
Author(s):  
Randall Kelton ◽  
Jalal Fathi ◽  
Efstathios I. Meletis ◽  
Haiying Huang
Keyword(s):  
Surface Roughness ◽  
Plastic Zone ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Surface Profile ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Crack Pinning ◽  
Surface Changes

Changes in surface morphology have long been thought to be associated with crack propagation in materials. In this paper, we study the changes in the surface profile of the crack-tip plastic zone with an attempt to understand the relationship between the plasticity-induced surface profile changes and the crack growth behavior. Center crack specimens were electropolished and etched to reveal the grain structure for white light interferometer (WLI) imaging prior to and during fatigue testing. After growing the crack to a predetermined pre-crack length, a viewing zone was selected outside of the plastic zone of the pre-crack. The surface profile of the viewing zone was imaged using a WLI microscope at selected fatigue cycle intervals. An image processing algorithm was developed to evaluate the changes of the surface profile. We observed that the crack growth rate is not uniform at the microscopic scale; the crack growth was retarded at crack pinning points and the crack grows at a faster rate while propagating between the pinning points. Relatively large surface topology changes were observed to be constrained to the area surrounding the tip of pinned cracks. However, there was an avalanche of surface changes covering the entire monotonic zone upon the crack being released from a pinned location. Interestingly enough, minor or no measurable surface changes could be seen for propagating cracks. These results indicate a surface roughness change threshold may exist for predicting the duration during which a crack is pinned. Results suggest the threshold and crack propagation rate between pinning locations may be functions of the amplitude of the stress intensity factor.

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.

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.

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

Effects of Grain Size on Fatigue Crack Propagation in Copper Film

2010 ◽  
Vol 452-453 ◽  
pp. 289-292
Author(s):  
Kenichi Shimizu ◽  
Tashiyuki Torii
Keyword(s):  
Grain Size ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Crack Opening Displacement ◽  
Fatigue Crack Propagation ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Opening Displacement

Using a fatigue testing method by which fatigue cracks can be initiated and propagated in a film adhered to cover a circular through-hole in a base plate subjected to cyclic loads, annealed copper films of 100m thickness with different crystal grain sizes were fatigued. The fatigue crack propagation in the film with large grains was often decelerated, so the crack propagation rate of the film with the large grain was lower than that of the film with the small grain. When the crack propagation was decelerated, the crack opening displacement obtained from the film with large grain size was smaller than that obtained from the film with small grain size. The relationship between the fatigue crack propagation rate and the stress intensity factor estimated from the crack opening displacement was identical for the cracks in the film with the large grain and the small grain.

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 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.

scholarly journals Surface Roughness and Fiber Angular Orientation Analysis Toward Laminated Composite Crack Propagation

2021 ◽  
Vol 20 (1) ◽  
pp. 44
Author(s):  
Hilmi Iman Firmansyah ◽  
Bayu Pranoto ◽  
Chandra Gunawan ◽  
Hangga Wicaksono ◽  
Muhammad Fakhruddin
Keyword(s):  
Surface Roughness ◽  
Crack Propagation ◽  
Fatigue Testing ◽  
Laminated Composite ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Metal Composite ◽  
Angular Orientation ◽  
Variable Response ◽  
Fiber Metal

Composite is a material that consisting of two or more materials, either micro or macro, where the properties of the material differ in shape and chemical composition from the original substance. In this study, fatigue testing of fiber metal composites was carried out to determine the rate of crack propagation so that the age of the fiber metal composite specimen was known. The independent variable in this research is the angular orientation of the carbon fiber and the surface roughness of the aluminum with the dependent variable response is the bridge crack rate. The manufacture of fiber metal laminates specimens uses the Vacuum Resin Infuse (VARI) method, which uses a vacuum pump as a means to flow the resin from the reservoir to the mold. This method is used to minimize the occurrence of air bubbles trapped on the specimen which causes porosity defects which will reduce the strength of the metal laminates specimen itself. Fatigue testing is performed using the stress amplitude method. That is, the value of the load when the tensile test is one third of the tensile strength. After the fatigue test was carried out, the results were obtained on specimens with an angular orientation of 0/90 ° fibers, the crack propagation rate slowed down with a cycle value of 90000 in specimens with a surface roughness value of 2.128 µm then decreased cycles on specimens with a value of 2.887 µm, namely 11000 cycles.

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