Download or read book Mechanisms of starting of fatigue cracks in the titanium alloy TA6V written by Henri Octor and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Fretting Fatigue Mechanisms on 7075 T6 Aluminum Alloy and Ti 6Al 4V Titanium Alloy written by Saeed Adibnazari and published by . This book was released on 1991 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is generally believed that fretting accelerates crack nucleation. However, a method to precisely determine the end of a crack nucleation stage has not been developed. It is therefore currently difficult to determine the exact affect of fretting on the stages of fatigue. This research started by hypothsizing that fretting fatigue cracks nucleate after the damage threshold (the amount of fretting damage required to bring a reduction to fatigue life) has been reached. Similar to the fretting fatigue damage threshold concept, it was hypothesized that there exists a normal pressure threshold as well. As a consequence of verifying these hypotheses, many other valuable facts related to fretting fatigue damage production and growth, crack nucleation and propagation were discovered.
Download or read book On the Role of Crack Closure Mechanisms in Influencing Fatigue Crack Growth Following Tensile Overloads in a Titanium Alloy written by CM. Ward-Close and published by . This book was released on 1988 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comparative study has been made of the transient fatigue crack growth rate behavior following tensile overloads at low (near-threshold) and high stress intensity ranges in an ?/?-type titanium alloy IMI 550, with specific emphasis of the role of crack closure mechanisms. After tensile overloads, fatigue cracks in both coarse-grained ?-annealed and fine-grained ?/? microstructures were observed initially to accelerate, followed by significant retardation, before growth rates returned to their baseline levels. The initial acceleration was attributed to an immediate reduction in near-tip closure, as indicated by metallographic sectioning, and a slight decrease in far-field closure, as measured by back-face compliance methods. Subsequent retardation was not associated with marked changes in far-field closure, although there were indications on compliance curves of a second "closure point" at a higher load, suggesting an approximate 50% increase in near-tip closure. Load interaction effects were found to be most severe where specific mechanisms of crack closure were prominant. Thus, the maximum post-overload retardations were seen in the coarse-grained ? microstructure, and when baseline stress intensity ranges were close to the threshold ?KTH, or when the maximum overload stress intensities approached the fracture toughness.
Download or read book The Effect of O2 H2O and N2 on the Fatigue Crack Growth Behavior of an Alpha Beta Titanium Alloy at 24 C and 177 C written by Stephen W. Smith and published by . This book was released on 2001 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Crack Growth Characteristics of Thin Sheet Titanium Alloy Ti 6 2 2 2 2 written by and published by . This book was released on 2001 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Fracture Mechanics Data written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue and Fracture Mechanics written by John H. Underwood and published by ASTM International. This book was released on 1997 with total page 697 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Atmospheric Influence on Fatigue Crack Propagation in Titanium Alloys at Elevated Temperature written by S. Lesterlin and published by . This book was released on 1997 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fatigue crack propagation behavior of a Ti-6Al-4V alloy has been investigated at room temperature and at 300°C. Tests were run in air, high vacuum, and some other environments with controlled partial pressure of water vapor and oxygen. The enhancement of the fatigue crack growth rates observed in air in comparison to high vacuum, considered as an inert environment, is clearly attributed to the presence of water vapor. Tests in a controlled environment demonstrate that very low partial pressure can accelerate crack propagation. On the basis of previous studies on Al alloys and steels, two controlling mechanisms are considered and discussed, namely, a propagation-assisted water vapor adsorption and a hydrogen-assisted propagation.
Download or read book Mechanism of Corrosion Fatigue of Steel and Titanium Alloys written by G. W. Simmons and published by . This book was released on 1978 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The kinetics of subcritical-crack growth under sustained load in 3.5 pct NaCl solution have been determined over a range of temperatures from 3 to 90 C. 0.64 cm (1/4 in.) thick wedge-opening-load (WOL) specimens were used. A well defined K-independent stage (Stage II) of growth was observed at each temperature, and the rate was controlled by a thermally activated process having an apparent activation energy of 20 plus or minus 5 kJ/mol (on a 95 pct confidence level basis). These Stage II rates were substantially higher than those reported by Williams and Nelson, at corresponding temperatures, for this alloy tested in hydrogen at 0.9 atm. The apparent activation energy for crack growth in these two environments, however, are statistically equivalent. No identification of the rate controlling process (or processes) has been made.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1990 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling the Behavior of Short Fatigue Cracks in a Near Titanium Alloy written by MC. Hardy and published by . This book was released on 1996 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Low-cycle fatigue is the greatest potential cause of failure in critical aeroengine components. To prevent premature failure, the fatigue life of these components needs to be predicted accurately. This requires knowledge of crack nucleation and growth under fatigue loading. Initial crack propagation is not continuous as a result of obstacles such as grain boundaries. Laboratory observation has shown that cracks decelerate rapidly as they approach these boundaries. Further growth may be impeded for a considerable number of cycles if there is a significant difference in orientation between the cracked and adjacent grains. This behavior effectively disappears at longer crack sizes. A detailed quantitative appraisal of crack growth rates is vital for component life predictions based on fracture mechanics. Cracks that nucleate during engine operation experience very high stresses that may exceed the material yield stress. Established linear elastic fracture mechanics may not be applicable due to loss of similitude caused by violation of the small-scale yielding criterion. These concepts are also based on continuum fracture mechanics and therefore cannot describe the early stages of crack growth. This paper considers an empirical model for short crack growth in a ? heat-treated near-? titanium alloy at room temperature. Crack growth rate equations are expressed in terms of crack length and effective stress range and were derived from experimental crack length versus cycles data. These data were generated at constant peak stress and various stress ratios. The expressions are shown to give an excellent representation of experimental crack growth rate versus crack length data. In producing the model, procedures have been established to determine crack opening loads and critical crack sizes above which continuum fracture mechanics apply.
Download or read book The Effect of O2 H2o and N2 on the Fatigue Crack Growth Behavior of an Alpha Beta Titanium Alloy at 24 C and 177 C written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-11 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: To study the effects of atmospheric species on the fatigue crack growth behavior of an a+B titanium alloy (Ti 6-2-2-2-2) at room temperature and 177 C, fatigue tests were performed in laboratory air, ultrahigh vacuum, and high purity water vapor, oxygen, nitrogen and helium at various partial pressures. Accelerated fatigue crack growth rates in laboratory air compared to ultrahigh vacuum are linked to the damaging effects of both water vapor and oxygen. Observations of the fatigue crack growth behavior in ultrahigh purity environments, along with surface film analysis using X-ray photoelectron spectroscopy (XPS), suggest that multiple crack-tip processes govern the damaging effects of air. Three possible mechanisms are proposed: 1) at low pressure (less than 10(exp -1) Pa), accelerated da/dN is likely due to monolayer adsorption on crack-tip surfaces presumably resulting in decreased bond strengths at the fatigue crack tip, 2) for pressures greater than 10(exp -1) Pa, accelerated da/dN in oxygen may result from oxidation at the crack tip limiting reversible slip, and 3) in water vapor, absorption of atomic hydrogen at the reactive crack tip resulting in process zone embrittlement.Smith, Stephen W. and Piascik, Robert S.Langley Research CenterFATIGUE TESTS; FATIGUE (MATERIALS); CRACK PROPAGATION; TITANIUM ALLOYS; EMBRITTLEMENT; ATMOSPHERIC COMPOSITION; X RAY SPECTROSCOPY; WATER VAPOR; ULTRAHIGH VACUUM; PHOTOELECTRON SPECTROSCOPY
Download or read book Fretting Fatigue Behavior of a Titanium Alloy Ti 6AL 4V at Elevated Temperature written by Onder Sahan and published by . This book was released on 2002-03-01 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this research is to investigate the fretting fatigue behavior of the titanium alloy Ti-6Al-4V at elevated temperature is investigated. Fretting and plain fatigue experiments are conducted at 260 . Crack initiation location and crack initiation orientation is measured and fretting and plain fatigue life data of the specimens from these tests are obtained. Fatigue parameters capable of predicting the number of cycles to specimen failure, the crack location and the crack orientation along the contact surface are analyzed. The parameters are calculated by using the computed stresses and strains obtained from the finite element analysis. The mechanisms responsible for the fretting fatigue crack initiation are determined. The effect of elevated temperature is examined by comparing room and elevated temperature fretting and plain fatigue data.
Download or read book Understanding the Slip Deformation and Crack Initiation Mechanism in a Near alpha Titanium Alloy During Fatigue Loading written by Conghui Liu and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue written by Engineering Sciences Data Unit and published by . This book was released on 1965 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Some Aspects of Fatigue Crack Closure in Titanium Alloys written by C. J. Beevers and published by . This book was released on 1979 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack growth at intermediate rates and R 0.1 has been measured in compact tension specimens of the alloys Ti-6Al-4V and Ti-6Al-5Zr-0.5Mo-0.25Si. Crack length was determined from the output of a crack mouth displacement gauge and by using a d.c. potential drop technique. The incidence of crack closure was examined during fatigue by using both of the above methods; COD was found to be more reliable for closure measurement than potential drop. In contrast to the fine microstructured Ti-6Al-4V, the coarse Ti-6Al-5Zr-0.5Mo-0.25Si showed substantial load transfer across the crack faces during fatigue and this was attributed to a 'non-closure' mechanism. Low crack growth rates in the latter alloy were rationalized in terms of an effective delta K. Marked reductions in growth rate produced by variable amplitude loading ot Ti-6Al-4V could not be explained by crack closure. (Author).
Download or read book The Merging of Fatigue and Fracture Mechanics Concepts A Historical Perspective written by and published by . This book was released on 1997 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
