Analytical and Experimental Study of Near-Threshold Interactions Between Crack Closure Mechanisms PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Analytical and Experimental Study of Near-Threshold Interactions Between Crack Closure Mechanisms PDF full book. Access full book title Analytical and Experimental Study of Near-Threshold Interactions Between Crack Closure Mechanisms by National Aeronautics and Space Administration (NASA). Download full books in PDF and EPUB format.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781721572359 Category : Languages : en Pages : 32
Book Description
The results of an analytical closure model that considers contributions and interactions between plasticity-, roughness-, and oxide-induced crack closure mechanisms are presented and compared with experimental data. The analytical model is shown to provide a good description of the combined influences of crack roughness, oxide debris, and plasticity in the near-threshold regime. Furthermore, analytical results indicate that closure mechanisms interact in a non-linear manner such that the total amount of closure is not the sum of closure contributions for each mechanism. Newman, John A. and Riddell, William T. and Piascik, Robert S. Langley Research Center NASA/TM-2003-211755, NAS 1.15:211755, L-18207, ARL-TR-2774
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781721572359 Category : Languages : en Pages : 32
Book Description
The results of an analytical closure model that considers contributions and interactions between plasticity-, roughness-, and oxide-induced crack closure mechanisms are presented and compared with experimental data. The analytical model is shown to provide a good description of the combined influences of crack roughness, oxide debris, and plasticity in the near-threshold regime. Furthermore, analytical results indicate that closure mechanisms interact in a non-linear manner such that the total amount of closure is not the sum of closure contributions for each mechanism. Newman, John A. and Riddell, William T. and Piascik, Robert S. Langley Research Center NASA/TM-2003-211755, NAS 1.15:211755, L-18207, ARL-TR-2774
Author: RS. Piascik Publisher: ISBN: Category : Crack Languages : en Pages : 14
Book Description
An advanced model has been developed to calculate interactions between plasticity and roughness closure mechanisms resulting in the fatigue crack growth threshold. Near-threshold closure is complex because multiple closure mechanisms are likely, including roughness-, oxide-, and plasticity-induced crack closure. Results show closure first occurs either at the crack tip (tip contact), or at the fatigue-crack-surface asperity nearest the crack tip (asperity contact), in the absence of load history effects. Model calculations, verified by laboratory experiments, reveal a transition from tip contact to asperity contact produces fatigue crack growth threshold behavior; here, both model and experiment show that an abrupt increase in closure (asperity contact) results in the rapid decrease in fatigue crack growth rate at threshold. A comparison of an advanced crack-tip load displacement measurement technique, and standard global compliance methods show that global methods lack the sensitivity to accurately characterize crack closure at threshold.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781721572137 Category : Languages : en Pages : 34
Book Description
A fatigue crack closure model is developed that includes interactions between the three closure mechanisms most likely to occur at threshold; plasticity, roughness, and oxide. This model, herein referred to as the CROP model (for Closure, Roughness, Oxide, and Plasticity), also includes the effects of out-of plane cracking and multi-axial loading. These features make the CROP closure model uniquely suited for, but not limited to, threshold applications. Rough cracks are idealized here as two-dimensional sawtooths, whose geometry induces mixed-mode crack- tip stresses. Continuum mechanics and crack-tip dislocation concepts are combined to relate crack face displacements to crack-tip loads. Geometric criteria are used to determine closure loads from crack-face displacements. Finite element results, used to verify model predictions, provide critical information about the locations where crack closure occurs. Newman, John A. and Riddell, William T. and Piascik, Robert S. Langley Research Center NASA/TM-2003-212402, L-18279, NAS 1.15:212402, ARL-TR-2959
Author: Nestor Perez Publisher: Springer ISBN: 3319249991 Category : Science Languages : en Pages : 428
Book Description
The second edition of this textbook includes a refined presentation of concepts in each chapter, additional examples; new problems and sections, such as conformal mapping and mechanical behavior of wood; while retaining all the features of the original book. The material included in this book is based upon the development of analytical and numerical procedures pertinent to particular fields of linear elastic fracture mechanics (LEFM) and plastic fracture mechanics (PFM), including mixed-mode-loading interaction. The mathematical approach undertaken herein is coupled with a brief review of several fracture theories available in cited references, along with many color images and figures. Dynamic fracture mechanics is included through the field of fatigue and Charpy impact testing.
Author: D. Chen Publisher: ISBN: Category : Carbon steels Languages : en Pages : 14
Book Description
Based on the S-shaped unloading hysteresis curve a new method for determining the crack closure has been developed in which the plastic deformation near the crack tip is taken into consideration. The crack growth rate can be expressed uniquely by the effective stress intensity range, ?Keffop = Kmax - Kop or ?Keffcl = Kmax - Kcl, which is independent of the stress ratio and the loading history. The tip of a nonpropagating crack does not open even under the maximum tensile load during one loading cycle. The measured values of the crack opening ratios Uop(?Keffop/Kmax) and Ucl(?Keffcl/Kmax) of a steadily propagating crack are mainly controlled by Kmax and the stress ratio R.
Author: DL. Davidson Publisher: ISBN: Category : ASTM compliance offset method Languages : en Pages : 22
Book Description
An elastic-plastic finite element model and high resolution experimental measurements of growing fatigue cracks are employed in partnership to investigate the relationship between crack closure, near-tip deformation behavior, and remote load-displacement measurements. The model focuses on plasticity-induced closure effects for fatigue cracks in the Paris regime, while the experiments study fatigue cracks in the Paris and near-threshold regimes in a variety of materials. The suitability of the ASTM compliance offset method and the recently-proposed adjusted compliance ratio (ACR) method to characterize near-tip closure effects is evaluated. The experiments and analyses both show that crack-tip strains below the crack-opening stress, Sop, are a relatively small fraction of the total crack-tip strain range for cracks in the Paris regime, and therefore may be insignificant for crack-tip deformation and damage and crack growth. The experiments further indicate that crack-tip strains below Sop are a relatively larger fraction of the total crack-tip strain at lower ?K values, nearer the threshold, where Sop values are higher. The current ASTM compliance offset procedure for determining the crack opening load is shown to provide accurate information about true crack-tip opening loads in theory. However, due to the limited sensitivity of the method in practice, and the corresponding need to employ a non-zero compliance offset, the method gives underestimates of opening and closing loads that may be considerably in error relative to the true crack-tip values. The current ACR technique does not appear to do a good job of characterizing the near-tip deformation response for cracks in the Paris regime, because remote displacement measurements do not appear to be adequately sensitive to near-tip strains.
Author: National Aeronautics and Space Administration (NASA)
Author: National Aeronautics and Space Administration (NASA)
Author: John A. Newman
Author: John A. Newman
Author: John A. Newman
Author: RS. Piascik
Author: National Aeronautics and Space Administration (NASA)
Author: Nestor Perez
Author: D. Chen
Author: DL. Davidson
Author: