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2 edition of Aspects of fatigue crack growth in [alpha] - titanium. found in the catalog.

Aspects of fatigue crack growth in [alpha] - titanium.

C. M. Ward-Close

Aspects of fatigue crack growth in [alpha] - titanium.

by C. M. Ward-Close

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Published by University of Birmingham in Birmingham .
Written in English


Edition Notes

Thesis (Ph.D.) - University of Birmingham, Dept of Physical Metallurgy, 1978.

ID Numbers
Open LibraryOL17213072M

1 INTRODUCTION. Fatigue crack growth behavior is a crucial factor for the design and performance of modern structural materials. It has been shown in the past that the presence of residual stresses, introduced during processing, dictates the fatigue performance [].In the absence of residual stresses, fatigue crack propagation depends on the material's microstructural features. The study is focused on finding and describing microscopic paths of modes II and III cracks in commercially pure α-titanium (hcp structure). Experiments were done on cylindrical bars with a circumferential cracked notch loaded in shear (modes II, III and II + III) and torsion (mode III). Fractography analysis showed that the crack growth was crystallography-controlled and the deflection .

A nonlinear creep/dwell interaction model is derived based on nucleation and propagation of a surface fatigue crack and its coalescence with creep/dwell damages (cavities or wedge cracks) along its path inside the material, which results in the total damage accumulation rate as given by d a / d N = (1 + (l c + l z) / λ) {(d a / d N) f + (d a / d N) env} ⁠, where (d a / d N) f is the pure. The crack length, a, is plotted versus the corresponding number of cycles, N, at which the crack was measured. Figure 2. Constant amplitude crack growth data. As shown, most of the life of the component is spent while the crack length is relatively small. In addition, the crack growth rate increases with increased applied stress.

FATIGUE CRACK GROWTH DATA SOFTWARE OPTIONS 10 Viewing of the FCGD Curve Fits 10 Compare FCGD Curves With User Data 11 Tutorial 12 7. THE USE OF FCGD IN DTA 12 8. REFERENCES 13 APPENDICES A—Industry Survey Results and Priority List B—Fatigue Crack Growth Data and Curve Fits C—Fatigue Crack Growth Database Software Operation. Fractography of modern engineering materials: composites and metals: a symposium. steels --Fractography in the failure analysis of corroded fracture surfaces --Micromechanisms of major/minor cycle fatigue crack growth inconel --Fractographic analysis of hydrogen-assisted cracking in alpha-beta titanium alloys --Fractographic aspects.


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Aspects of fatigue crack growth in [alpha] - titanium by C. M. Ward-Close Download PDF EPUB FB2

Environment for all the tests was high humidity for both pre-cracking and fatigue crack growth phase. Fatigue crack growth behavior of Ti-6Al-4V alloy is presented in Figure 8. The data presented in Figure 8 shows the da/dN and ∆KI for various stress ratios.

All the data were below ∆K of 20 MPa√m to show the two stages in crack growth and Author: T. Goswami. @article{osti_, title = {Dwell and environmental aspects of fatigue in alpha/beta titanium alloys}, author = {Evans, W J and Bache, M R}, abstractNote = {Dwell sensitive fatigue in titanium alloys at near ambient temperatures was first recognized as a consequence of aerospace component failures.

Previous to this, extended periods of loading at peak or high mean stress were assumed to. The corrosion fatigue crack growth characteristics of small surface and corner cracks in aluminum alloy is established.

The damaging effect of salt water on the early stages of small crack growth is characterized by crack initiation at constituent particle pits, intergranular microcracking for a less than micrometers, and transgranular small crack growth for a micrometer.

Application of the Unified Approach requires a data reduction scheme that is illustrated schematically in Fig. fatigue crack growth tests can be performed either at constant R-ratio (minimum load/maximum load) or at constant K se, crack growth rates can be represented in terms of ΔK or K max (Fig.

1a and b), and both representations are complementary since the crack growth. Stages of fatigue. Historically, fatigue has been separated into regions of high cycle fatigue that require more than 10 4 cycles to failure where stress is low and primarily elastic and low cycle fatigue where there is significant plasticity.

Experiments have shown that low cycle fatigue is also crack growth. Fatigue failures, both for high and low cycle, all follow the same basic steps. A crack growth equation is used for calculating the size of a fatigue crack growing from cyclic loads.

The growth of fatigue cracks can result in catastrophic failure, particularly in the case of aircraft. A crack growth equation can be used to ensure safety, both in the design phase and during operation, by predicting the size of cracks.

The effects of stabilization annealing and cooling rate on high cycle fatigue (HCF) and fatigue crack propagation (FCP) behaviors of β-processed Ti64 alloys were examined.

After β-process heating above β transus, two different cooling rates of air cooling (β-annealing) and water quenching (β-quenching) were utilized. Selected specimens were then underwent stabilization annealing. Conceivably there is a threshold stress intensity value ∆Kth below which there is no fatigue crack growth or the growth is too small to measure.

Although experimental verification of the existence of this threshold is difficult, ∆Kth is usually shown to be between 5 and 15 ksi-in1/2 for steels and between 3 and 6 ksi-in1/2 for aluminum alloys.

Comparison of fatigue crack growth rates. Download: Download high-res image (KB) Download: Download full-size image; Figure 4. Reduction in fatigue crack growth rate with increasing crack length. Propagation direction is from left to right, and arrows identify an arrest mark on the facet surface caused by an unload/reload cycle.

The effect of β annealing on high cycle fatigue (HCF) and fatigue crack propagation (FCP) behaviors of Ti64 alloy were examined, and the results were compared to those of mill-annealed counterpart. The tensile tests, stress-controlled HCF tests, and FCP tests were conducted, and the fractographic and micrographic analyses were performed before and after the tests.

used for obtaining fatigue crack growthdata. In all cases a thin slit, notch, or groove with a very small root radius is machined into the specimen. Fatigue crack growth testing is covered in Section The fatigue crack growth rates for Al and Ti are much more rapid than steel for a given ∆K.

However, when normalized by Young’s Modulus all metals exhibit. This research has involved studies of fatigue crack initiation as well as fatigue crack propagation.

Principal findings have been that subsurface fatigue cracks can be initiated in forgings of this titanium alloy when the alpha-phase size is of the order of 10 micron, a.

Probabilistic methods in fatigue and fracture. Statistical Modeling of Microstructural Effects on Fatigue Behavior of [alpha]/[beta] Titanium Alloys --A Titanium Aluminide Alloy --Probabilistic Fatigue Damage Assessment for Short Crack Growth --Probabilistic Modeling of Fatigue Crack Growth in Ti-6Al-4V --Cautionary Aspects of Applied.

Titanium-A Review of Current Forming and Fabrication Techniques (Critical Review). 1, J. Brooks, P.J. Bridges, and D. Stephen Microstructure and Property Modification of Cast Alpha-2 Titanium. Titanium alloy casting technology is an attractive net-shape approach which lately has been receiving increased attention.

The various aspects of the two main casting methods, the rammed graphite and the investment casting techniques, are discussed, including size, shape-making, and resulting properties, and ways to improve them. The dwell fatigue microstructure of a near-α titanium alloy was studied by optical microscopy and transmission electron microscopy.

Optical microscopy revealed primary α grains as being crack. Fatigue crack growth data for different materials (Aluminum, Titanium, ARMCO-iron) in wide stress ratio range (R > 0, R.

Primary Aspects. Titanium and its alloys ciency), fatigue crack growth rate, and fracture toughness, as well as manufacturing consider-ations such as welding and forming require-ments, are extremely important. These factors Introduction to Selection of Titanium Alloys / 7 (a) (b).

Physical Metallurgy Processing and. Applications. Fatigue Crack Growth Rate edited almost 30 books, the majority on various aspects of titanium.

Recent pub-lications include a comprehensive review of titanium powder metallurgy and an article on titanium additive manufacturing. He. Ripple fatigue is the synergy of low amplitude, high cycle fatigue crack growth and SLC. In summary, time dependent failures in titanium alloys can occur at stresses below tensile strength (UTS), stress intensity factors below K IC and when dwell or ripple fatigue loads are applied.Study of alpha-case depth in Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V R Gaddam1, B Sefer1, R Pederson1,2 and M-L Antti1 1Division of Materials Science, Luleå University of Technology, S Luleå, Sweden 2Research Centre, GKN Aerospace Engine Systems, S Trollhättan, Sweden E-mail: @ Abstract.

At temperatures exceeding °C titanium alloys generally. The physical properties of titanium and its alloys are summarised in Table 1, from which it can be seen that there is little variation from one alloy to another.

For example, coefficients of thermal expansion range from x K-1 to x K Table 1. .