Download or read book Microplasticity and Fatigue Crack Initiation in Titanium Alloy Ti 6Al 4v written by Philip Dilan Littlewood and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Titanium alloys are often used in aerospace applications in which they are subjected to cyclic loading. It has been found that the addition of a hold at peak load greatly decreases the fatigue life of these alloys. This is referred to as "cold-dwell fatigue". In order to improve component life prediction, it is desirable to understand the mechanisms leading to initiation of fatigue cracks. Due to the high anisotropy of a-titanium, it is expected that deformation on a microstructural scale will he significantly heterogeneous. To understand the process of crack nucleation, the mecha- nisms of this deformation must first he understood. This thesis will present a series of experiments which will attempt to give some insight into this process. Two main lines of inquiry have heen undertaken. The first method uses electron hackscat- tered diffraction (EBSD) to obtain the crystal orientations within a selected region. Optical mi- croscopy and digital image correlation methods were then used to track the accumulation of strain in the region during deformation. Results were obtained for monotonic tension, cyclic fatigue, and cold-dwell fatigue. Behaviour in local strain peaks differed hetween loading modes, hut strain concentrations in the range of 2-4 times mean strain were typical. The second method uses the cross-correlation based EBSD technique developed by Wilkinson et al [1] to derive the dislocation densities present in a crystal. By tracking the changes in dislocation density after different deformation regimes, some insight can be gained into the local deformation processes that produced the dislocation densities. Strong links were found between the local crystallography and inhomogeneities in strain and dislocation density accumulation. In particular, interactions between grains of differing orientations was found to have a strong impact on deformation behaviour. Additionally, a link was found between high strain accumulation and crack initiation in both fatigue and dwell fatigue.

Download or read book Fretting Fatigue Crack Initiation Behavior of Ti 6Al 4V written by SA. Namjoshi and published by . This book was released on 2003 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fretting fatigue crack initiation behavior of titanium alloy, Ti-6Al-4V was investigated by using different geometries of the fretting pad. Specimens were examined to determine the crack initiation location and the crack angle orientation along the contact surface. Fretting fatigue experiments were analyzed with the finite element analysis. Several critical plane based parameters were used to predict the number of cycles to fretting fatigue crack initiation, crack initiation location and crack orientation angle along the contact surface. These predictions were compared with the experimental counterparts to study the role of normal and shear stresses on the critical plane in order to characterize fretting fatigue crack initiation behavior. From these comparisons, the fretting fatigue crack initiation mechanism in the tested titanium alloy appears to be governed by the shear stress on the critical plane. However, the role of normal stress on the critical plane at present appears to be unclear.

Download or read book Fatigue Crack Propagation in Titanium Alloys written by A. J. McEvily and published by . This book was released on 1977 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Annual Report covers the period Aug. 1, 1976 through Sept. 30, 1977, and deals with the topics fatigue crack initiation and growth in Ti-6Al-4V forging alloy. Subsurface crack initiation has been related to the presence of severe dislocation pile-ups and perhaps to the influence of internal hydrogen. In the fatigue crack growth progress it has been shown that different mechanism are operative in various regions of the da/dN versus delta K plot. The retardation effect associated with overload has been shown to be primarily a surface related effect due to the higher degree of crack closure which exists in the surface regions of a specimen. (Author).

Download or read book On the Process of Subsurface Fatigue Crack Initiation in TI 6AL 4V written by James Alfred Ruppen and published by . This book was released on 1978 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Investigation of Fretting Fatigue Crack Initiation Behavior of the Titanium Alloy Ti 6A1 4V written by Christopher Douglas Lykins and published by . This book was released on 1999 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microplasticity written by Charles J. McMahon and published by . This book was released on 1968 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Process of Subsurface Fatigue Crack Initiation in TI 6AL 4V written by James Alfred Ruppen and published by . This book was released on 1978 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Initiation and Propagation in Two Titanium Alloys written by R. Brown and published by . This book was released on 1978 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Accelerated Crack Propagation of Titanium by Methanol Halogenated Hydrocarbons and Other Solutions written by and published by . This book was released on 1967 with total page 70 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 National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-23 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack growth rates of Ti 6-2-2-2-2 as a function of stress ratio, temperature (24 or 177 C), tensile orientation and environment (laboratory air or ultrahigh vacuum) are presented. Fatigue crack growth rates of Ti 6-2-2-2-2 are also compared with two more widely used titanium alloys (Timetal 21S and Ti 6Al-4V). The fatigue crack growth rate (da/dN) of Ti 6-2-2-2-2 in laboratory air is dependent upon stress ratio (R), particularly in the near-threshold and lower-Paris regimes. For low R (less than approximately 0.5), da/dN is influenced by crack closure behavior. At higher R (> 0.5), a maximum stress-intensity factor (K(sub max)) dependence is observed. Fatigue crack growth behavior is affected by test temperature between 24 and 177 C. For moderate to high applied cyclic-stress-intensity factors (delta-K), the slope of the log da/dN versus log delta-K curve is lower in 177 C laboratory air than 24 C laboratory air. The difference in slope results in lower values of da/dN for exposure to 177 C laboratory air compared to room temperature laboratory air. The onset of this temperature effect is dependent upon the applied R. This temperature effect has not been observed in ultrahigh vacuum. Specimen orientation has been shown to affect the slope of the log da/dN versus log delta-K curve in the Paris regime.Smith, Stephen W. and Piascik, Robert S.Langley Research CenterCRACK PROPAGATION; FATIGUE (MATERIALS); TITANIUM ALLOYS; CORROSION; STRESS RATIO; TEMPERATURE EFFECTS; CRACK CLOSURE; STRESS INTENSITY FACTORS

Download or read book Fatigue Crack Growth Retardation After Singlecycle Peak Overload in Ti 6a1 4v Titanium Alloy written by Raymond Edward Jones and published by . This book was released on 1972 with total page 84 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 The Effects of an Aqueous Environment on the Fatigue Crack Propagation Characteristics of Titanium Alloys written by T. W. Crooker and published by . This book was released on 1967 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack propagation was studied in Ti-6Al-4V, Ti-7Al-2Cb-1Ta, Ti-6Al-6V-2Sn-1Cu-0.5Fe, Ti-6Al-3V-1Mo, and Ti-7Al-2.5Mo alloys. These materials possess yield strengths in excess of 100 ksi, combined with favorable levels of fracture toughness, and they are currently under evaluation for application in large welded structures. Where an application involves repetitive loading, a knowledge of fatigue crack propagation characteristics is required for failure-safe design against fracture. Fabrication and non-destructive testing procedures cannot guarantee that cracklike defects, which can grow to a critical size, will not be present in plate-thickness sections containing welded joints. In addition, the role of an aggressive environment, such as salt water, in this failure mechanism is of the utmost importance. Fatigue crack propagation data were taken in both ambient room air and 3.5% salt-water environments. Surface-notched plate bend specimens were cycled in full-reverse (tension-to-compression) sinusoidal loading. The fatigue crack was observed optically, and the crack growth rate was described as an empirical power-law function of the total (elastic-plus-plastic) strain range. Fatigue crack growth rate relationships were first developed in an air environment and then employed as baselines for establishing the effect of the salt-water environment. Comparisons were made among the fatigue crack propagation characteristics of the several titanium alloys and among a broad spectrum of high-strength structural alloys, both ferrous and nonferrous, previously studied. (Author).

Download or read book Influence of Metallurgical Factors on the Fatigue Crack Growth Rate in Alpha Beta Titanium Alloys written by J. C. Chesnutt and published by . This book was released on 1978 with total page 423 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research was conducted on two alpha-beta titanium alloys, Ti-6Al-4V and Ti-6Al-2Sn 4Zr-6Mo, as a function of alloy composition microstructure and strength level, environment, and fatigue loading conditions. A wide range of microstructural conditions, seven for Ti-6Al-4V and three for Ti-6Al-2Sn-4Zr-6Mo, was chosen to provide a full range of constituent types and morphologies and a range of mechanical properties. All the material for the program was obtained in the form of pancake forgings which were uniformly and weakly textured. The initial portion of the program consisted of material characterization and base line fatigue crack propagation (FCP) testing. Characterization included a full description of microstructures, as well as mechanical property testing, fracture toughness tests, S-N curve determination and measurement of other properties such as modulus and texture. Base line FCP testing in dry air at two stress ratios (R) of 0.1 and 0.3; and in a 3.5% NaCl solution at 1 and 20 Hz was conducted in this portion of the program. Results of this study included the determination that transformed beta microstructures generally exhibit the greatest fatigue crack propagation resistance and that increasing the load ration, R, can lead to significant increases in crack growth rate; the behavior in both cases was rationalized in terms of crack tip interaction with microstructural constituents.

Download or read book Fatigue Crack Growth Measurements in TMF Testing of Titanium Alloys Using an ACPD Technique written by Y. Dai and published by . This book was released on 1995 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: A thermal-mechanical fatigue (TMF) testing system has been developed which is capable of studying the fatigue behaviors of gas turbine materials under simultaneous changes of temperatures and strains (or stresses). Furthermore, an advanced alternating current potential difference (ACPD) measurement technique has been developed successfully to perform on-line monitoring of fatigue crack initiation and growth in specimens tested under isothermal and TMF conditions. In this paper, the basic principles of the ACPD technique as well as all the relevant experimental procedures for performing ACPD measurements, including probe setup, choice of alternating currents (AC) and frequencies, noise rejection, data acquisition, and signal processing, are described. The linear relationship between ACPD signals and crack lengths, as well as the effects of thermal cycling on the ACPD signal, are presented and discussed. The capabilities of the TMF and ACPD systems are well illustrated by fatigue crack initiation and growth test results under isothermal and TMF conditions. These tests were performed on two titanium forgings, Ti-6Al-4V (Ti64) and Ti-6Al-2Sn-6Mo (Ti6246), respectively. Alloy Ti64 was TMF cycled between 150 and 400°C, while Ti6246 was cycled between 200 and 482°C. The resolution for detecting crack initiation at the root of notches was found to be 50 ?m with 95% confidence while the resolution for crack growth was 2 ?m per mV change of ACPD. An environmental assisted cracking model applied to TMF crack growth is proposed for rationalizing the data.

Download or read book Post Processing Effects on the Fatigue Crack Propagation of Titanium Ti 6al 4v Alloy After Simulated Superplastic Forming Conditions written by Franna Pitt and published by . This book was released on 2000 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Crack Propagation in Metastable Titanium Alloys written by A. Raith and published by . This book was released on 1984 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fatigue crack growth rate tests of water quenched Corona-5 (Ti-4.5Al-1.5Cr-5Mo) and Ti-6Al-4V alloy were conducted in air at room temperature. The effect of the presence of the metastable retained beta phase on the fatigue crack growth rate was examined in this research. The specimens were heat treated and water quenched to have unstable beta phase that could be transformed to martensite during the fatigue crack growth testing. As quenched specimens were compared with specimens in the mill annealed condition. The fatigue crack growth rates of all the specimens were in the same order of magnitude regardless of the heat treatment. From this research it was shown that in Corona-5 and Ti-6Al-4V alloys the fatigue crack growth rates were not affected by the strain induced martensitic transformation.