scholarly journals Identification of Relationships between Heat Treatment and Fatigue Crack Growth of αβ Titanium Alloys

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 512 ◽  
Author(s):  
Vincent Renon ◽  
Gilbert Henaff ◽  
Céline Larignon ◽  
Simon Perusin ◽  
Patrick Villechaise
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Titanium Alloys ◽  
Crack Growth ◽  
High Performance ◽  
Shielding Effect ◽  
Characteristic Parameters ◽  
Fatigue Crack Growth Resistance ◽  
Fully Lamellar ◽  
Crack Growth Rates

This study deals with the influence of microstructure on the fatigue crack growth resistance of αβ titanium alloys: Ti-6Al-4V ELI (Extra Low Interstitial) that may compete with the conventional Ti-6Al-4V alloy in the manufacture of high performance aircraft. Six different microstructures have been considered: the as-received bimodal microstructures and five distinct fully lamellar microstructures. The characteristic parameters of these microstructures were determined and crack growth tests were performed with crack closure measurements in order to evaluate the shielding effect induced by closure. A comparison of crack growth rates, fracture surfaces, and crack path was carried out for the different microstructures. The results outline a transition between two propagation regimes from a microstructure-sensitive to microstructure-insensitive propagation.

Fatigue Crack Growth Behavior of Titanium Alloy Ti-6Al-4V and Weldment

2001 ◽  
Vol 123 (3) ◽  
pp. 141-146 ◽  
Author(s):  
Mamdouh M. Salama
Keyword(s):  
Growth Rate ◽  
Titanium Alloy ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Titanium Alloys ◽  
Crack Growth ◽  
Growth Rates ◽  
Offshore Structures ◽  
Crack Growth Rates

Optimization of weight, cost, and performance of deepwater offshore structures demands the increased utilization of high strength, light weight, and corrosion resistant materials such as titanium alloys. Titanium alloy Ti-6Al-4V has been considered for several critical components such as risers and taper joints. Because of the novelty of use of titanium alloys in the offshore industry, there is currently no standard governing design of titanium components for offshore structures. Since these structural components are subjected to a complex spectrum of environmental loading, assessment of defect tolerance using fatigue crack growth analysis is generally considered an important design parameter. In this paper, more than 60 crack growth data sets from 20 independent laboratories were collected and analyzed to develop crack growth rate equations for use in defect assessment. These data include the results of fatigue testing of both base material and welded joints in air and seawater with and without cathodic protection and at different R-ratios and test frequencies. The results suggest that for crack growth rates above 10−7 in./cycle, crack growth of Ti-6Al-4V appears to be independent of testing condition and materials processing. At the low crack growth rate (below 10−7 in./cycle), the review revealed that data are very limited. These limited data, however, suggest that the crack growth threshold is dependent on the R-ratio and slightly dependent on material processing. Comparison between crack growth rates of steel and titanium alloy (Ti-6Al-4V) showed that the two materials have very similar behavior.

Improvement of Fatigue Crack Growth Resistance by Serrated Grain Boundary at High Temperature

1991 ◽  
Vol 113 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Hiroshi lizuka ◽  
Manabu Tanaka ◽  
Fumio Ashihara
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Cracks ◽  
Crack Growth Resistance ◽  
Fatigue Crack Growth Resistance ◽  
Crack Growth Rates

Effects of serrated grain boundaries on the improvement of fatigue-crack growth resistance were investigated using austenitic 21Cr-4Ni-9Mn heat-resisting steel at 973K in air. Grain boundaries were serrated by grain-boundary reaction precipitates. The crack-growth rates were considerably decreased in the specimens with the serrated grain boundaries. The fatigue cracks were largely deflected by the serrated grain boundaries, and brittle intergranular fracture was retarded. The improvement of the crack-growth resistance was obtained especially under the conditions of low crack-growth rates of less than 30 μm/cycle. The widths and the heights of the deflected portions of the cracks were in the range from about a few μm to 30 μm.

Effect of Load-Mix on Fatigue Crack Growth in 63Sn-37Pb Solder Joints

1997 ◽  
Vol 119 (2) ◽  
pp. 114-118 ◽  
Author(s):  
D. Yao ◽  
J. K. Shang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Load Ratio ◽  
Strain Energy Release ◽  
Fatigue Crack Growth Resistance ◽  
Sinusoidal Waveform ◽  
Energy Release Rates ◽  
Strain Energy Release Rates ◽  
Crack Growth Rates

Fatigue crack growth at the interface between Sn-Pb solder and Cu was examined under various mixed-mode conditions. The load-mix, in terms of the ratio of Mode-II to Mode-I stress intensities, was systematically changed by varying the thickness ratio of Cu layers in the flexural-peel specimens made from Sn-Pb/Cu joints. Fatigue crack growth experiments were conducted using a sinusoidal waveform at a frequency of 5 Hz and a load-ratio of zero. Fatigue crack growth rates were measured as a function of the total strain energy release rates for a given load-mix. Fatigue crack growth resistance was found to increase with the load-mix, with the effect of the load-mix being more pronounced in the near-threshold regime. The effect of the load-mix on fatigue crack growth is shown to result from shear-enhanced frictional sliding of fatigue crack surfaces.

Influence of Plastic Prestrain on the Fatigue Crack Growth Resistance (da/dN vs. ΔK) of ASTM A36 Structural Steel

2015 ◽  
Author(s):  
Gustavo Henrique B. Donato ◽  
Fábio Gonçalves Cavalcante
Keyword(s):  
Mechanical Properties ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Cracks ◽  
Pressure Vessels ◽  
Engineering Structures ◽  
Fatigue Crack Growth Resistance ◽  
Crack Growth Rates

High responsibility components operating under cyclic loading can have their resistance against initiation and growth of fatigue cracks highly influenced by previous thermomechanical processing. Within the interest of the present work, different manufacturing processes and installation techniques incorporate cold plastic straining to engineering structures; two typical examples on the oil and gas fields are: i) the offshore pipelines installation method called reeling; ii) the fabrication of pipes using the UOE method and pressure vessels through calendering. Within this scenario, this work investigates the effects of plastic prestrain on the fatigue crack growth rates (da/dN vs. ΔK) of a hot-rolled ASTM A36 steel. Different from previous results from the literature, in which prestrains were applied directly to machined samples, in this work uniform prestraining was imposed to steel strips (1/2” thick) and specimens were then extracted to avoid (or minimize) residual stress effects. Prestrain levels were around 4, 8 and 14% and C(T) specimens were machined from original and prestrained materials according to ASTM E647 standard. Fatigue crack growth tests were carried out under load control in an MTS 810 (250 kN) equipment using R = 0.1. Results revealed that plastic prestraining considerably reduced crack growth rates for the studied material, which was expected based on the literature and hardening behavior of the studied material. However, results also revealed two interesting trends: i) the larger is the imposed prestrain, the greater is the growth rate reduction in a nonlinear asymptotic relationship; ii) the larger is imposed ΔK, the more pronounced is the effect of prestraining. Crack closure effects were also investigated, but revealed no influence on the obtained mechanical properties. Consequently, results could be critically discussed based on effective crack driving forces and elastic-plastic mechanical properties, in special those related to flow and hardening. The conclusions and success of the employed methods encourage further efforts to incorporate plastic prestrain effects on structural integrity assessments.

scholarly journals Effect of morphology of primary a on fatigue crack propagation resistance in a near a heat resistant Titanium alloy

2020 ◽  
Vol 321 ◽  
pp. 11030
Author(s):  
Y. Sumi ◽  
H. Takabayashi ◽  
Hangyue Y. Li ◽  
P. Bowen
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Threshold ◽  
Fatigue Crack Growth Resistance ◽  
Crack Propagation Resistance ◽  
Heat Resistant ◽  
Paris Region ◽  
Crack Growth Rates

DAT54 is a new near a heat resistant Ti alloy developed for disk applications in the compressor part of jet engines. DTA54 with bimodal microstructure shows a good balance of fatigue strength and creep life, and performs better than Ti-6242s up to 873 K. However, the influence of microstructure on properties, especially the effect of the morphology of primary a on fatigue crack growth resistance is not understood. In this study, samples with different types of microstructure were prepared by applying different heat treatment temperatures, and the influence of microstructure on fatigue crack growth properties at ambient temperature and 823 K was investigated. Influence of environment was also investigated by testing in vacuum and in air condition. Acicular microstructure shows lower fatigue crack growth rates in Paris’ region than the bimodal microstructures at 823 K. For the bimodal structures, aspect ratio of primary a do not have apparent influence on fatigue crack growth rates in Paris’ region, whereas fatigue threshold (DKth) seems to be affected by the morphology of primary a.

Fatigue Crack Growth Resistance of Several Neutron Irradiated Pressure Vessel Steels and Welds

1974 ◽  
Vol 96 (4) ◽  
pp. 242-248 ◽  
Author(s):  
P. Shahinian ◽  
H. E. Watson ◽  
J. R. Hawthorne
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Growth Resistance ◽  
Stress Intensity Factor Range ◽  
Fatigue Crack Growth Resistance ◽  
Rate Versus ◽  
Pressure Vessel Steels ◽  
Crack Growth Rates ◽  
Submerged Arc

Pre and postirradiation fatigue crack growth rates in A302-B, A533-B, and A543 steel plate and in two A543 welds (submerged arc and electroslag) were determined at 550 deg F (288 deg C) in air. The fracture mechanics approach was used to analyze the experimental data. Neutron irradiation at 585 deg F (307 deg C) to 2.5 × 1019 n/cm2, > 1 MeV produced no significant effect on resistance to crack growth in A302-B steel and caused only a slight decrease in crack growth resistance of A533-B and A543 steels. Also, the resistance to crack growth of the submerged arc weld was unaffected by the irradiation, but that of the electroslag weld was substantially improved. The crack growth rate versus stress intensity factor range curve for the A302-B steel represents an upper bound for the pre and postirradiation data for the steels and welds of this study.

Fatigue Crack Growth in a TiAl Alloy with Lamellar Microstructure

1992 ◽  
Vol 273 ◽  
Author(s):  
David L. Davidson
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Titanium Alloys ◽  
Crack Growth ◽  
Growth Rates ◽  
Tial Alloy ◽  
Lamellar Microstructure ◽  
Crack Advance ◽  
Crack Growth Rates ◽  
Loading Axis

ABSTRACTThe mechanisms of fatigue crack advance are examined for a lamellar α2 + γ alloy. Crack growth rates are highly dependent on the orientation of the loading axis to the lamellae direction. Thus, the material has some of the characteristics of a composite. For crack growth perpendicular to the lamellae, the mechanisms of crack advance are similar to those of other titanium alloys, while crack growth parallel to lamellae has other characteristics.

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