Download or read book Influence of Crack Closure and Stress Ratio on Near Threshold Fatigue Crack Growth Behavior in Ti 1100 written by T. Nicholas and published by . This book was released on 1994 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present study, the fatigue crack growth behavior of a near-?, ?-processed titanium alloy, Ti-1100, was investigated with the objective of assessing the influence of crack closure and stress ratio on fatigue threshold. Measurement of the crack-opening load in single-edge tension [SE(T)] specimens was made by near-tip strain gage and DCPD methods. Fatigue threshold stress intensity ranges, ?Kth, determined under constant stress ratio and constant maximum stress intensity, variable stress ratio conditions indicate almost identical values for R above 0.5. It is postulated that while crack closure in the wake of the crack tip is responsible for the no-growth condition in the former case, lack of sufficient damage accumulation at the crack tip as a consequence of the formation of an insignificant reversed plastic zone and large planar slip band formations surrounding the crack tip appears to be responsible for no growth in the latter case. The use of an effective stress intensity based on closure data consolidates most of the threshold data, indicating the independence of the fatigue crack growth data to mean stress or R.

Download or read book Cyclic Deformation Fracture and Nondestructive Evaluation of Advanced Materials written by Michael R. Mitchell and published by ASTM International. This book was released on 1994 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt: Examines the initiation and growth of fatigue cracks and the fracture toughness of advanced materials such as silicon nitride, special alloys and steels, thermoplastics, and graphite-epoxy composites; and explains several non-destructive techniques to evaluate such materials for manufacturing defect

Download or read book Mechanics of Fatigue Crack Closure written by Wolf Elber and published by ASTM International. This book was released on 1988 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fracture Mechanics written by Walter G. Reuter and published by ASTM International. This book was released on 1995 with total page 842 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Influences of Crack Closure and Load History on Near Threshold Crack Growth Behavior in Surface Flaws written by Jira, JR. and published by . This book was released on 1990 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack growth threshold tests are conducted on a high-strength titanium alloy using a surface flaw specimen geometry. A laser interferometer is used to monitor crack-mouth opening displacements, from which compliance determined crack length is computed. Four types of loading history involving both increasing-and decreasing-?K are used to reach a threshold condition. Two of the test conditions maintain constant Kmax under computer control. Crack closure is obtained from the load-displacement plots and used to determine an effective stress-intensity range, ?Keff. Results from all four test types indicate that a single value of an effective stress-intensity range is obtained which is independent of stress ratio, R, or load history. Crack growth rate data in the near-threshold regime, on the other hand, appear to have a dependence on R even when ?Keff is used as a correlating parameter.

Download or read book Fatigue and Fracture Mechanics written by Tina Louise Panontin and published by ASTM International. This book was released on 1999 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Fatigue Crack Closure Measurement and Analysis written by R. Craig McClung and published by ASTM International. This book was released on 1999 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Analyses of Fatigue Crack Growth and Closure Near Threshold Conditions for Large Crack Behavior written by J. C. Newman (Jr) and published by . This book was released on 1999 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crack Size and Shape Considerations Related to Near Threshold Fatigue Crack Growth Rate Behavior written by J. Keith Donald and published by . This book was released on 2018 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is well recognized that crack size or load history or both have an important influence on near-threshold fatigue crack rate behavior at a low stress ratio. This investigation will compare the behavior of a radial crack, such as a surface flaw or a corner crack, to that of a linear crack to see if crack shape plays a role in physically small crack to long crack behavior. Recent research has unveiled a methodology to experimentally partition plasticity from roughness- and oxide-induced crack closure, showing that nonplasticity-induced closure mechanisms have a greater influence at low Kmax by orders of magnitude. Knowledge of this is key to understanding differences between long crack and physically small crack behavior in the near-threshold regime. In this study, the well behaved 2024-T351 aluminum alloy was used to generate threshold data using numerous specimen geometries, flaw geometries, crack sizes, and test procedures to highlight not only the significance of crack size but also the role of crack shape. It will be shown both experimentally and analytically that a radial crack (surface flaw, corner crack) has significantly less remote closure and, therefore, a lower threshold than a through crack (compact tension, middle crack tension), even if the crack size is the same.

Download or read book Fatigue Crack Closure at Near Threshold Growth Rates in Steels Effects of Microstructure Load Sequence and Environment written by Michael K. Schaper and published by . This book was released on 2012 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper summarizes long-term research on fatigue crack closure in several labs of the author. Various experimental techniques were used in different combinations. Primarily, a sophisticated dynamic compliance technique based on highly sensitive resonance vibration measurements and crack tip diffracted ultrasonic wave analysis is applied. Whereas the first method reflects the global through thickness behavior, the second method enables spatial resolution, which is achieved with a reduction of sensitivity yet has the advantage that the signal generation is independent on the stress state ahead of the crack tip. The results allow a coherent view into the effects of the stress state, material plasticity, fracture surface roughness, and oxidation tendency on the closure behavior and, therefore, on both the threshold stress intensity and near-threshold crack propagation. Specifically, the different load ratio, load sequence, and the environmental effects on the threshold values of ferritic, martensitic, and austenitic steels are addressed.

Download or read book Handbook of Fatigue Crack Propagation in Metallic Structures written by Andrea Carpinteri and published by Elsevier Publishing Company. This book was released on 1994 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hardbound. The purpose of this Handbook is to provide a review of the knowledge and experiences in the field of fatigue fracture mechanics. It is well-known that engineering structures can fail due to cyclic loading. For instance, a cyclically time-varying loading reduces the structure strength and can provoke a fatigue failure consisting of three stages: (a) crack initiation (b) crack propagation and (c) catastrophic failure. Since last century many scientists have tried to understand the reasons for the above-mentioned failures and how to prevent them. This Handbook contains valuable contributions from leading experts within the international scientific community and covers many of the important problems associated with the fatigue phenomena in civil, mechanical and nuclear engineering.

Download or read book Threshold Fatigue Crack Growth in Ti 6Al 2Sn 4Zr 6Mo written by Dale A. Nagy and published by . This book was released on 1987 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study was to examine the effects of different loading histories, closure loads, and stress ratios on the near-threshold crack growth rate of a Titanium-Aluminum alloy. Two different test types were conducted on four separate specimens to determine the threshold stress intensity of the material. The first test type maintained a constant maximum stress intensity factor, K(max) on a specimen with a growing crack. As the crack grew, the minimum stress intensity factor was increased until the crack growth rate reached the threshold level. The second test type also maintained a constant K(max). For this test a block of cycles was applied to the specimen and if the crack growth rate for the block of cycles was below the threshold level then K(min) was decreased by a small amount and another block of cycles was applied. This process was continued until the crack growth rate reached the threshold level. Once the threshold stress intensity was determined the cracks were grown under constant maximum load and stress ratio (R) to measure the threshold crack growth rate. Both test types were conducted over a wide range of stress ratios to investigate the effects of varying closure loads.

Download or read book An Indirect Technique for Determining Closure Free Fatigue Crack Growth Behavior written by SW. Smith and published by . This book was released on 2000 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of stress ratio (R) and maximum applied stress-intensity factor (Kmax) on fatigue crack growth rate (da/dN) have been investigated. Fatigue crack growth behavior was analyzed by plotting applied cyclic stress-intensity factor (?K) versus applied Kmax for an ?+? titanium alloy (Ti 6-2-2-2-2) at several values of da/dN. This analysis revealed two distinct regions of fatigue crack growth behavior. At threshold da/dN (? 10-10 m/cycle) and for Kmax 4.6 MPa?m the threshold cyclic stress-intensity factor (?Kth) is greatly influenced by crack closure. For closure free fatigue crack growth (Kmax 4.6 MPa?m), a subtle but distinct decrease in ?Kth is observed with increasing Kmax. Plots of ?K versus Kmax were also generated for AA 2024 test data produced in two different studies. These data also revealed two distinct regions of fatigue crack growth behavior consistent with the Ti 6-2-2-2-2 results. This methodology can be used to determine closure free fatigue crack growth and to monitor subtle changes in ?Kth.

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1987 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of Crack Closure in Fatigue written by T. T. Shih and published by . This book was released on 1973 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crack closure phenomenon in fatigue was studied by using a Ti-6Al-4V titanium alloy. The occurrence of crack closure was directly measured by an electrical-potential method, and indirectly by load-strain measurement. The experimental results showed that the onset of crack closure depends on both the stress ratio, and the maximum stress intensity factor. No crack closure was observed for stress ratio, greater than 0.3 in this alloy. A two-dimensional elastic model was used to explain the behavior of the recorded load-strain curves. Closure force was estimated by using this model. Yield level stress was found near the crack tip. Based on this estimated closure force, the crack opening displacement was calculated. This result showed that onset of crack closure detected by electrical-potential measurement and crack-opening-displacement measurement is the same. The implications of crack closure on fatigue crack are considered. The experimental results show that crack closure cannot fully account for the effect of stress ratio, on crack growth, and that it cannot be regarded as the sole cause for delay.