TWO AND THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS OF PLASTICITY-INDUCED FATIGUE CRACK CLOSURE? A COMPREHENSIVE PARAMETRIC STUDY. 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 TWO AND THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS OF PLASTICITY-INDUCED FATIGUE CRACK CLOSURE? A COMPREHENSIVE PARAMETRIC STUDY. PDF full book. Access full book title TWO AND THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS OF PLASTICITY-INDUCED FATIGUE CRACK CLOSURE? A COMPREHENSIVE PARAMETRIC STUDY. by . Download full books in PDF and EPUB format.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Finite element analyses are frequently used to model growing fatigue cracks and the associated plasticity-induced crack closure. Two-dimensional, elastic-perfectly plastic finite element analyses of middle-crack tension (M(T)), bend (SEB), and compact tension (C(T)) geometries were conducted to study fatigue crack closure and to calculate the crack opening values under plane-strain and plane-stress conditions. The loading was selected to give the same maximum stress intensity factor in both geometries, and thus similar initial forward plastic zone sizes. Mesh refinement studies were performed on all geometries with various element types. For the C(T) geometry, negligible crack opening loads under plane-strain conditions were observed. In contrast, for the M(T) specimen, the plane-strain crack opening stresses were found to be significantly larger. This difference was shown to be a consequence of in-plane constraint. Under plane-stress conditions, it was found that the in-plane constraint has negligible effect, such that the opening values are approximately the same for the C(T), SEB, and M(T) specimens. Next, the crack opening values of the C(T), SEB and M(T) specimens were compared under various stress levels and load ratios. The effect of a highly refined mesh on crack opening values was noted and significantly lower crack opening values than those reported in literature were found. A new methodology is presented to calculate crack opening values in planar geometries using the crack surface nodal force distribution under minimum loading as determined from finite element analyses. The calculated crack opening values are compared with values obtained using finite element analysis and more conventional crack opening assessment methodologies. It is shown that the new method is independent of loading increment, integration method (normal and reduced integration), and crack opening assessment location. The compared opening values were in good agreement with strip-yield.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Finite element analyses are frequently used to model growing fatigue cracks and the associated plasticity-induced crack closure. Two-dimensional, elastic-perfectly plastic finite element analyses of middle-crack tension (M(T)), bend (SEB), and compact tension (C(T)) geometries were conducted to study fatigue crack closure and to calculate the crack opening values under plane-strain and plane-stress conditions. The loading was selected to give the same maximum stress intensity factor in both geometries, and thus similar initial forward plastic zone sizes. Mesh refinement studies were performed on all geometries with various element types. For the C(T) geometry, negligible crack opening loads under plane-strain conditions were observed. In contrast, for the M(T) specimen, the plane-strain crack opening stresses were found to be significantly larger. This difference was shown to be a consequence of in-plane constraint. Under plane-stress conditions, it was found that the in-plane constraint has negligible effect, such that the opening values are approximately the same for the C(T), SEB, and M(T) specimens. Next, the crack opening values of the C(T), SEB and M(T) specimens were compared under various stress levels and load ratios. The effect of a highly refined mesh on crack opening values was noted and significantly lower crack opening values than those reported in literature were found. A new methodology is presented to calculate crack opening values in planar geometries using the crack surface nodal force distribution under minimum loading as determined from finite element analyses. The calculated crack opening values are compared with values obtained using finite element analysis and more conventional crack opening assessment methodologies. It is shown that the new method is independent of loading increment, integration method (normal and reduced integration), and crack opening assessment location. The compared opening values were in good agreement with strip-yield.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Elastic-plastic finite element analyses were performed to predict the crack opening level profiles in semi-elliptical surface cracks. A script was written to use the commercial finite element code ANSYS to predict opening levels in cracked geometries. The functionality of the scripts was verified by comparing predicted opening levels in two and three-dimensional center-cracked geometries to experimental results. In addition, a parameter study was performed in which various aspects of the modeling routine were modified. This included a mesh refinement study as well as a study into the effect of a strain hardening material. The main focus of the current research, however, is to compare finite element predicted opening levels with published opening levels determined experimentally. Due to the complexities and long run-times involved with these models, no attempt was made at growing the cracks from initial length to final length. Instead, discrete crack lengths at which experimental opening levels were published were instead used. Also, no attempt was made to predict the crack aspect ratio evolution. The finite element predicted opening levels were in all cases significantly lower than those reported experimentally, however, similar trends in both crack opening level profile along the crack front, and opening level variations with crack growth were shown.
Author: Jeffrey David Skinner
Publisher:
ISBN:
Category : Finite element method
Languages : en
Pages :
Get Book Here
Book Description
[3] The finite element predicted opening levels were in all cases significantly lower than those reported experimentally, however, similar trends in both crack opening level profile along the crack front, and opening level variations with crack growth were shown.
Author: Mehmet Gkhan Gken
Publisher: LAP Lambert Academic Publishing
ISBN: 9783838357911
Category :
Languages : en
Pages : 84
Get Book Here
Book Description
In spite of the fact that the use of contact elements in modeling crack surface contact, and thus in modeling of crack closure is inherently natural, almost no effort to incorporate it in the finite element analysis of fatigue crack growth has been reported in the literature. The traditional method is based on placing truss elements on the crack surface nodes In this research contact elements are used to model crack surface contact and similar to mentioned method the determination of crack opening stress is accomplished by monitoring the state of contact elements during incrementally applied loading. Instead of determining crack opening stress of every load cycle, an algorithm that makes it possible to find crack opening stress at predetermined load cycle intervals is developed. With the developed algorithm it was possible to analyze crack closure behavior during a larger number of load cycles with less execution time. Due to simulation of relatively high number of load cycles, final stabilization of crack opening stress values after a subsequent decay in the initially "stabilized" opening stress values is observed.
Author: Stephen Riley Johnston
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages :
Get Book Here
Book Description
This thesis discusses plasticity-induced crack closure based finite element simulations of small fatigue cracks in three dimensions utilizing crystal plasticity theory. Previously, modeling has been performed in two dimensions using a double-slip crystal plasticity material model. The goal of this work is to extend that research using a full three-dimensional FCC crystal plasticity material model implementation that accounts for all twelve FCC slip systems. Discussions of Python scripts that were written to perform analyses with the commercial finite element code ABAQUS are given. A detailed description of the modeling methodology is presented along with results for single crystals and bicrystals. The results are compared with finite element and experimental results from the literature. A discussion of preliminary work for the analysis of crack growth around an intermetallic particle is also presented.
Author: Marcos Lugo
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages :
Get Book Here
Book Description
From its discovery, crack closure was recognized as a key aspect in understanding the fatigue crack growth process. Considering the condition of plane stress, a vast amount of research has been conducted experimentally, analytically, and numerically to understand the complex process of fatigue crack growth and crack closure. Nonzero crack opening stress values are routinely observed, and it seems that there is a general agreement regarding the incidence of the phenomenon under plane stress. However, investigations regarding crack closure under plane strain conditions are less abundant. Moreover, the existence of crack closure under the plane strain state of the stress has been questioned. The importance of accurate measurements of closure to predict adequately fatigue crack growth rates should not be underestimated. Models employed to predict fatigue crack growth rates rely on plasticity-induced crack closure concepts, and the validity of plasticity-induced crack closure depends on crack closure measurements. Crack closure measurements can be performed with Elber's Method, the ASTM standard (Compliance offset method), or it may be done alternatively by the compliance ratio (CR) or the adjusted compliance ratio method (ACR). In this research, a small scale yielding two-parameter modified boundary layer analysis is performed to study the occurrence of plasticity-induced fatigue crack closure under constant amplitude loading and plane strain conditions. A wide range of T-stresses and KI levels are considered in the finite element analysis with the purpose of exploring the behavior of the crack opening stress. Crack closure was observed for some values of T-stress. Other values of T-stress resulted in an absence of closure under steady state conditions. In addition, an elastic-plastic finite element model was used to simulate a growing fatigue crack with WARP3D software. The computed displacements were used to determine the effective stress intensity factor range [delta]Keff with the ASTM standard compliance offset approach, the (CR) method, and the (ACR) method. Finally, measurement location effects on ACR and the ability of ACR method to remove residuals stresses were investigated.
Author: Shahrum Abdullah
Publisher: Trans Tech Publications Ltd
ISBN: 3038137405
Category : Technology & Engineering
Languages : en
Pages : 370
Get Book Here
Book Description
This special issue of Trends in Automotive Research contains papers contributed to the Regional Conference on Automotive Research (ReCAR) , held on the 14 and 15th December, 2011, in Kuala Lumpur, Malaysia. The conference was organised by the Centre for Automotive Research (CAR), Faculty of Engineering and the Built Environment, Universiti Kebangsaan Malaysia. Volume is indexed by Thomson Reuters CPCI-S (WoS).
Author: Eugene J. Bednarz
Publisher:
ISBN:
Category :
Languages : en
Pages : 186
Get Book Here
Book Description
Plasticity induced closure and its effect on the fatigue growth of short cracks were investigated analytically in a high strength titanium alloy at room temperature as well as in a nickel base alloy at elevated temperature. The analysis consisted of subjecting a single-edge cracked specimen with an initial crack length of .001 inch to cyclic loading and allowing the crack to propagate. This was accomplished using a two-dimensional finite element code and a theoretical finite element model of a typical test geometry. Visco II, the two-dimensional plane stress/plane strain finite element code, uses constant strain triangular elements and incorporates the Bodner-Partom Viscoplastic Flow Law to handle non-linear material behavior. The numerical simulations involved subjecting specimens of TI-6246 at room temperature (time-independent behavior) to cyclic loads with maximum nominal stress values of approximately 60 and 90 percent of the material yield strength and load ratios of -1.0 and 0.1 with a frequency of 1.0 Hz. The numerical simulations of specimens consisting of Inconel 718 at 1200 F (time-dependent behavior) consisted of cyclic loads where the maximum nominal stress was .90 yield strength, the applied load ratio was 0.1, and the cyclic frequencies were .01 and 1.0 Hz. The formation of a plastic wake and the affects of plasticity induced closure were observed in these specimens. (AW).
Author:
Publisher:
ISBN:
Category : Fracture mechanics
Languages : en
Pages : 434
Get Book Here
Book Description
Author: Rahmatollah Ghadimi Chermahini
Publisher:
ISBN:
Category : Materials
Languages : en
Pages : 147
Get Book Here
Book Description
