scholarly journals Effect of Electropulsing Treatment on the Fatigue Crack Growth Behavior of Copper

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2168 ◽  
Author(s):  
Yan Yin ◽  
Haibo Chen ◽  
Yasuyuki Morita ◽  
Yuhki Toku ◽  
Yang Ju
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Tip ◽  
Cyclic Stress ◽  
Crack Growth Behavior ◽  
Electropulsing Treatment ◽  
Two Sides

Crack propagation was quantitatively evaluated to investigate the effect of electropulsing treatment (EPT) on fatigue crack growth of copper specimens. Varying fatigue cycles were obtained under six different load levels. The crack lengths were measured under two load levels to examine the effect of cyclic stress. The microhardness was measured around the vicinity of the crack tip. Furthermore, the fracture surface was observed by scanning electron microscopy. Results show that EPT with electric current density of 150 A/mm2 enhances the high-cycle fatigue life, and the effect tends to increase with the decrease in cyclic stress. Vickers microhardness (HV) near the crack tip decreases to normal levels after treatment, and the approaching cracks on two sides can be observed. Local annealing and recrystallization occur around the fatigue crack tip. Accordingly, crack propagation can be delayed, and fatigue life can be prolonged by EPT.

scholarly journals An Integral Formulation of Two-Parameter Fatigue Crack Growth Model

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Jianguo Wu ◽  
Shan Jiang ◽  
Wei Zhang ◽  
Zili Wang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Closure ◽  
Crack Tip ◽  
Integral Form ◽  
Crack Growth Behavior ◽  
Crack Growth Model ◽  
Two Parameter

A two-parameter fatigue crack growth algorithm in integral form is proposed, which can describe the continuous crack growth process over the time period. In this model, the fatigue crack propagation behavior is governed by the temporal crack-tip state including the current applied load and the physical condition due to the previous load sequence. The plasticity-induced crack closure, left by the historical loading sequence, controls the following fatigue crack growth behavior and typically leads to the interaction effects. In the proposed method, a modified crack closure model deriving from the local plastic deformation is employed to account for this load memory effect. In general, this model can simulate the fatigue crack growth under variable amplitude loading. Additionally, this model is established on the physical state of crack tip in the small spatial and temporal scale, and it is used to evaluate the macroscopic crack propagation and fatigue life under irregular tension-tension loading. A special superimposed loading case is discussed to demonstrate the advantage of the proposed model, while the traditional two-parameter approach is not proper functional. Moreover, the typical various load spectra are also employed to validate the method. Good agreements are observed.

High-Temperature Fatigue Crack Propagation in P/M Ni3Al-B Alloys

1986 ◽  
Vol 81 ◽  
Author(s):  
K.-M. Chang ◽  
S.C. Huang ◽  
A.I. Taub
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Time Dependence ◽  
Crack Growth ◽  
Elevated Temperatures ◽  
Cyclic Stress ◽  
Propagation Mechanism ◽  
Crack Growth Behavior

AbstractDuctile Ni3Al-B type intermetallic alloys show a unique fatigue crack growth behavior at elevated temperatures. A crack propagation mechanism has been investigated in an experimental P/M alloy by testing the alloys with different fatigue frequencies at 400°C. The Ni3Al-B intermetallic alloy shows a substantial time-dependence of fatigue cracl growth rate when tested in air. Under a given cyclic stress intensity, an order of magnitude difference of crack growth rate was observed by decreasing the fatigue frequency. However, such a time-dependence did not occur when the alloy was tested in vacuum. It is concluded that “dynamic” embrittlement in an oxidation environment is the major factor controlling the fatigue crack growth in ordered Ni3Al-B alloys at elevated temperatures.

Fatigue Crack Growth Behavior of Autofrettaged Hydrogen Pressure Vessel Made of Low Alloy Steel

2017 ◽  
Author(s):  
Yoru Wada ◽  
Yusuke Yanagisawa
Keyword(s):  
High Pressure ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Cylindrical Specimen ◽  
Growth Behavior ◽  
Gaseous Hydrogen ◽  
Crack Growth Behavior ◽  
Low Alloy Steel

Autofrettage is used to known as an effective method to prevent fatigue crack propagation of thick-walled cylinder vessels operating under high pressure. Since low-alloy steel shows an enhanced crack growth rate in high-pressure gaseous hydrogen, this paper aims to validate the effect of autofrettage on crack growth behavior in high-pressure gaseous hydrogen utilizing 4%NiCrMoV steel (SA723 Gr3 Class2). An autofrettaged cylindrical specimen with a 70mm inside diameter and 111mm outside diameter was prepared with an axial EDM (depth of 1mm) notched on the inside surface. The measured residual stress profile coincides well with the calculated results. The fatigue crack growth test was conducted by pressurizing the cylinder and varying the external water pressure. Crack propagation from the EDM notch was observed in the non-autofrettaged cylindrical specimen while no crack propagation was observed when the initial EDM notch size was within the compressive residual stress field. When the initial EDM notch size was increased, the fatigue crack growth showed a narrow, groove-like fracture surface for the autofrettaged specimen. In order to qualitatively analyze those results, fatigue crack growth rates were examined under various load ratios including a negative load ratio using a fracture mechanics specimen. From the information obtained, crack growth analysis of an autofrettaged cylinder in a high-pressure hydrogen environment was successfully demonstrated with a fracture mechanics approach.

scholarly journals Influence of Pre-Stress Magnitude on Fatigue Crack Growth Behavior of Al-Alloy

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1267
Author(s):  
Chunguo Zhang ◽  
Weizhen Song ◽  
Qitao Wang ◽  
Wen Liu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Shot Peening ◽  
Fatigue Property ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Al Alloy ◽  
Fatigue Crack Growth Behavior

From tensile overload to shot peening, there have been many attempts to extend the fatigue properties of metals. A key challenge with the cold work processes is that it is hard to avoid generation of harmful effects (e.g., the increase of surface roughness caused by shot peening). Pre-stress has a positive effect on improving the fatigue property of metals, and it is expected to strength Al-alloy without introducing adverse factors. Four pre-stresses ranged from 120 to 183 MPa were incorporated in four cracked extended-compact tension specimens by application of different load based on the measured stress–strain curve. Fatigue crack growth behavior and fractured characteristic of the pre-stressed specimens were investigated systematically and were compared with those of an as-received specimen. The results show that the pre-stress ranged from 120 to 183 MPa significantly improved the fatigue resistance of Al-alloy by comparison with that of the as-received specimen. With increasing pre-stress, the fatigue life first increases, then decrease, and the specimen with pre-stress of 158 MPa has the longest fatigue life. For the manner of pre-stress, no adverse factor was observed for increasing fatigue property, and the induced pre-stress reduced gradually till to disappear during subsequent fatigue cycling.

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.

Experimental and Numerical Investigation of Plasticity-Induced Fatigue Crack Closure in Overmatched Welds

2013 ◽  
Author(s):  
Diego F. B. Sarzosa ◽  
Claudio Ruggieri
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Closure ◽  
Compact Tension ◽  
Cyclic Stress ◽  
Growth Behavior ◽  
Weld Strength ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior

This work provides a numerical and experimental investigation of fatigue crack growth behavior in steel weldments including crack closure effects and their coupled interaction with weld strength mismatch. A central objective of this study is to extend previously developed frameworks for evaluation of crack closure effects on fatigue crack growth rates (FCGR) to steel weldments while, at the same time, gaining additional understanding of commonly adopted criteria for crack closure loads. Very detailed non-linear finite element analyses using 3-D models of compact tension C(T) fracture specimens with square groove, weld centerline cracked welds provide the evolution of crack growth with cyclic stress intensity factor which is required for the estimation of the closure loads. Fatigue crack growth tests conducted on plane-sided, shallow-cracked C(T) specimens provide the necessary data against which crack closure effects on fatigue crack growth behavior can be assessed. Overall, the present investigation provides additional support for estimation procedures of plasticity-induced crack closure loads in fatigue analyses of structural steels and their weldments.

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