Development of Efficient Crack Growth Simulator Based on Hot-Mix Asphalt Fracture Mechanics

2003 ◽  
Vol 1832 (1) ◽  
pp. 105-112 ◽  
Author(s):  
Boonchai Sangpetngam ◽  
Bjorn Birgisson ◽  
Reynaldo Roque
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Boundary Element ◽  
Crack Growth ◽  
Hot Mix Asphalt ◽  
Displacement Discontinuity ◽  
Successful Implementation ◽  
Loading Conditions ◽  
Premature Failure ◽  
Major Mode

It has long been accepted that cracking of hot-mix asphalt (HMA) pavements is a major mode of premature failure. Many state departments of transportation have verified that pavement cracking occurred not only in fatigue cracking in which a crack initiates from the bottom of the asphalt layer but also in other modes such as low-temperature cracking and the more recently identified top-down cracking. Recent work at the University of Florida has led to the development of a crack growth law based on viscoelastic fracture mechanics that is capable of fully describing both initiation and propagation of cracks in asphalt mixtures. The model requires the determination of only four fundamental mixture parameters, which can be obtained from less than 1 h of testing using the Superpave® indirect tensile test (IDT). These parameters can account for microdamage, crack propagation, and healing for stated loading conditions, temperatures, and rest periods. The generalization of the HMA crack growth law needed for its successful implementation into a displacement discontinuity boundary element method is described. The resulting HMA boundary element approach is shown to predict the crack propagation of two coarse-graded mixtures under cyclic IDT loading conditions.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

A Fracture Mechanics Approach to Thermal Fatigue Life Prediction of Solder Joints

1990 ◽  
Vol 203 ◽  
Author(s):  
Yi-Hsin Pao
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Crack Growth ◽  
Thermal Fatigue ◽  
Solder Joints ◽  
Failure Process ◽  
Growth Equation ◽  
Thermal Fatigue Crack ◽  
Runge Kutta Method ◽  
Growth History

ABSTRACTThe approach developed is based on the assumption that thermal fatigue crack propagation in solder joints is primarily controlled by C* and J integrals. The effect of microstructural coarsening on crack propagation is discussed. A fracture criterion, J≥Jc, is used to define the failure of the joints. A crack growth governing equation has been formulated and can be numerically integrated to obtain the crack growth history given stress history as an input. The approach was applied to model the experiment by Wong and Helling [15]. In their experiment, surface-mounted electronic devices using eutectic Pb/Sn solder were tested in thermal cycles of −20 to 100°C and −55 to 125°C. A unified constitutive equation was assumed for the eutectic Pb/Sn solder. An equation for solving the shear stress in the joint was formulated and is coupled with the crack growth equation. Both equations were solved simultaneously by the Runge-Kutta method for the stress-time and crack growth history. The results of the prediction are in a good agreement with the experimental data, which indicates that fracture mechanics may be applied to describe the failure process of solder joints under cyclic thermal loadings.

Short Crack Growth Model in a Particulate Composite Using Nonlinear Elastic Fracture Mechanics

2003 ◽  
Author(s):  
Ying Zhang ◽  
Tsuchin Chu ◽  
Ajay Mahajan
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Crack Growth ◽  
Particulate Composite ◽  
Initial Crack ◽  
Short Crack ◽  
Video Tape ◽  
J Integral ◽  
Elastic Fracture ◽  
Crack Growth Model

The fracture mechanics model for a long crack does not work very well with short-crack propagation when the initial crack length is less than 5.1 mm (0.2 inch). In order to investigate the short crack effect, a series of tests of particulate composite specimens with long and short cracks were performed and the results recorded on a video tape. This test data was analyzed to determine the fracture parameters. Two initial crack lengths, 2.5 mm (0.1 inches) and 7.6 mm (0.3 inches) were used in the crack propagation tests. Based on the principle of linear elastic fracture mechanics (LEFM), the stress intensity factor KI was obtained. The instantaneous time-dependent J-integral for 0.1 and 0.3 inch crack specimens was determined by the NEFM analytical approach. The crack growth behavior was also investigated in the form of J-integral resistance curves. The calculated J-integral was reversed to derive a new KI. The new KI was compared with the measured value obtained from LEFM analysis results to determine the feasibility of applying the linear fracture approach to the non-linear behavior of the material. The results showed that the KI computed from the J-integral increased by 24.5%, and was at the time prior to the peak load for the 0.1 inch crack. For the 0.3 inch crack, the acceptable range was from the onset of propagation to the 9% strain stage (yield strain for the material), where the increase of the new KI was within 15.6%.

Numerical simulation of fatigue crack propagation in mixed-mode (I+II) using the program BemCracker2D

2019 ◽  
Vol 10 (4) ◽  
pp. 497-514
Author(s):  
Pedro G.P. Leite ◽  
Gilberto Gomes
Keyword(s):  
Numerical Simulation ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Mode I ◽  
Post Processing ◽  
Content Type

Purpose The purpose of this paper is to present the application of the boundary element method (BEM) in linear elastic fracture mechanics for analysis of fatigue crack propagation problems in mixed-mode (I+II) using a robust academic software named BemCracker2D and its graphical interface BemLab2D. Design/methodology/approach The methodology consists in calculating elastic stress by conventional BEM and to carry out an incremental analysis of the crack extension employing the dual BEM (DBEM). For each increment of the analysis, the stress intensity factors (SIFs) are computed by the J-Integral technique, the crack growth direction is evaluated by the maximum circumferential stress criterion and the crack growth rate is computed by a modified Paris equation, which takes into account an equivalent SIF to obtain the fracture Modes I and II. The numerical results are compared with the experimental and/or BEM values extracted from the open literature, aiming to demonstrate the accuracy and efficiency of the adopted methodology, as well as to validate the robustness of the programs. Findings The paper addresses the numerical simulation of fatigue crack growth. The main contribution of the paper is the introduction of a software for simulating two-dimensional fatigue crack growth problems in mixed-mode (I+II) via the DBEM. The software BemCracker2D coupled to the BemLab2D graphical user interface (GUI), for pre/post-processing, are very complete, efficient and versatile and its does make relevant contributions in the field of fracture mechanics. Originality/value The main contribution of the manuscript is the development of a GUI for pre/post-processing of 2D fracture mechanics problems, as well as the object oriented programming implementation. Finally, the main merit is of educational nature.

The Development of Fracture Mechanics for Elastomers

1994 ◽  
Vol 67 (3) ◽  
pp. 50-67 ◽  
Author(s):  
A. G. Thomas
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Test Piece ◽  
Design Procedure ◽  
Crack Growth Behavior ◽  
Large Strains ◽  
Physical Factors ◽  
Stick Slip ◽  
Premature Failure ◽  
Stage Of Development

Abstract The energy balance, or fracture mechanics, approach has proved successful in treating a number of fracture phenomena and unifying them in terms of what is believed to be a basic characteristic, the crack growth behavior when expressed in terms of the energy release rate T. It has also enabled some of the underlying physical factors to be identified and incorporated into appropriate theories. There are, however, some important limitations and outstanding problems which remain. For example, we do not at present have any quantitative understanding of what determines the precise form of the crack growth characteristic under repeated stressing. During the development of the approach, numerous checks were made of its validity by comparative experiments on different test piece geometries. This is important, as it is not certain that such comparisons will invariably give equivalent results and that the T vs. rate of tear relation is a true material characteristic. For example, if a test piece, such as the “split” test piece in Figure 2(d), is subjected to large pre-extensions in the direction of tearing, the tear resistance in some cases may apparently be much reduced from its unprestrained value. (Anisotropy is produced which is believed to be important in knotty tear development). Gent and Kim found a similar effect with laterally pre-strained pure shear test pieces. Also, if tear measurements are made with an edge crack test piece of natural rubber and the strains become great enough to produce crystallization in the main bulk of the test piece, the stick-slip behavior is suppressed and the tear strength appears to be increased. Thus it appears that in some cases the assumption that the strains just around the tip at the instant of tearing are independent of the bulk deformation is not true. Fortunately these cases seem to be the exception rather than the rule, but their occurrence demands continuing caution. Some peel tests of rubber-to-metal bonds for example show apparently anomalous force dependencies on peel angle. The current interest in the understanding and prediction of strength and durability of elastomer articles stems from the increasing importance attached to avoiding premature failure in service. The growing availability of finite element programs capable of dealing with large strains has already meant that force-deflection behavior can be at least approximately designed for; but a corresponding failure design procedure based on fracture mechanics is still in the stage of development.

Fatigue Crack Growth of Notched Tubular Specimen under Biaxial Loading Conditions

2006 ◽  
Vol 306-308 ◽  
pp. 139-144
Author(s):  
Hyun Woo Lee ◽  
Se-Jong Oh
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Growth ◽  
Biaxial Loading ◽  
Fatigue Crack Initiation ◽  
Growth Direction ◽  
Crack Growth Behavior ◽  
Loading Conditions ◽  
Tubular Specimen

Crack growth behavior of S45C notched tubular specimen was studied to predict fatigue crack initiation and crack propagation under biaxial loading conditions. Stress-strain field near the hole was analyzed by ANSYS. The crack initiation lives and the crack initiation locations were predicted from strain based theories, and the analysis results were compared with the test results. Crack propagation behaviors were studied to understand the reason of crack branching and crack growth rates changing under biaxial loading conditions. Crack growth direction was also observed to find the governing factors of the fatigue damage under biaxial loading conditions.

Augmenting Generic Fatigue Crack Growth Models Using 3D Finite Element Simulations and Gaussian Process Modeling

2019 ◽  
Author(s):  
Adrian Loghin ◽  
Shakhrukh Ismonov
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Propagation ◽  
Gaussian Process ◽  
Crack Growth ◽  
Life Assessment ◽  
Growth Path ◽  
3D Fem

Abstract Assessing the crack propagation life of components is a critical aspect in evaluating the overall structural integrity of a mechanical structure that poses a risk of failure. Engineers often rely on industry standards and fatigue crack growth tools such as NASGRO [1] and AFGROW [2] to perform life assessment for different structural components. A good understanding of material damage tolerant capabilities, and the component’s loading mission during service conditions are required along with the availability of generic fracture mechanics models implemented in the lifing tools. Three-dimensional (3D) linear elastic fracture mechanics (LEFM) finite element modeling (FEM) is also a viable alternative to simulate crack propagation in a component. This method allows capturing detailed geometry of the component and representative loading conditions which can be crucial to accurately simulate the three dimensionality of the propagating crack shape and further determine the associated loading cycles. In comparison to a generic model, the disadvantage of the 3D FEM is the extended runtime. One feasible way to benefit from 3D modeling is to employ it to understand the crack front evolution and growth path for the representative loading condition. Mode I stress intensity factors (KI) along the predetermined crack growth path can be generated for use in fatigue crack growth tools such as NASGRO. In the current study, such a 3D FEM lifing process is presented using a classical bolt-nut assembly, components that are commonly used in engineering design. First, KI solutions for a fixed crack aspect ratio a/c = 1 are benchmarked against a similar solution available in NASGRO. Next, a predefined set of crack shapes and sizes are simulated using 3D FEA. A machine learning model Gaussian Process (GP) was trained to predict the KI solutions of the 3D model, which in turn was used in the crack propagation simulation to accelerate the life assessment process. Verification of the implemented procedure is done by correlating the crack growth curves predicted from GP to the results obtained directly from 3D FE crack propagation method.

Fatigue Crack Growth Behavior of Embedded Flaws in Sour Pipelines

2016 ◽  
Author(s):  
Feng Gui ◽  
Colum Holtam ◽  
Brandon Gerst ◽  
Ramgopal Thodla
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Hydrogen Concentration ◽  
Crack Tip ◽  
Corrosion Process ◽  
Fatigue Performance ◽  
Loading Conditions ◽  
Hydrogen Charging

DNV-OS-F101 Appendix A provides procedures for the assessment of circumferential flaws located in subsea pipe girth welds using fracture mechanics methods, commonly referred to as engineering critical assessment (ECA). The purpose of the ECA approach is to provide critical flaw dimensions for given material properties and loading conditions in a conservative way. The results of the assessment are used to derive weld flaw acceptance (or weld repair) criteria to be used during pipeline installation. An ECA will typically consider flaws under installation and operation loading conditions, including fracture and fatigue crack growth (FCG) calculations. Internal and external surface-breaking flaws are assessed, along with embedded flaws. DNV-OS-F101 provides guidance on the appropriate FCG law to be used for the assessment of each flaw type under operational loading. For internal surface flaws exposed to sour production fluids (i.e. containing H2S) FCG rates (FCGRs) are known to be significantly higher than in air and, in the absence of relevant published data, project-specific testing is commonly performed to quantify fatigue performance. The recommendation for the assessment of embedded flaws is to use an air curve, as long as it can be substantiated that the fatigue performance is not reduced due to the environment. It has been demonstrated that the FCG behavior of C-Mn pipeline steels exposed to sour environments is dominated by bulk hydrogen charging effects, i.e. hydrogen charging by absorption from the exposed surfaces rather than the corrosion process at the crack tip. Therefore, it is expected that an embedded (or external) flaw in a sour pipeline will be located in steel containing absorbed hydrogen. This paper describes the results of an investigation aimed at understanding and quantifying the FCG behavior of embedded flaws in sour pipelines. For the purposes of this work, an embedded flaw refers to a crack propagating in hydrogen charged material but whose crack tip is not directly exposed to the sour environment. Hydrogen diffusion modelling and simulation studies were performed to predict the through wall hydrogen concentration in standard fracture mechanics specimens based on sour environmental conditions. Two novel test methods were developed to accurately measure FCGRs in hydrogen charged steel, one for single edge notched bend (SENB) specimens and one for compact tension (CT) specimens. FCGR tests were carried out using both methods. The FCGRs measured in hydrogen charged API 5L grade X65 pipeline steel were significantly higher than in air. In some cases, the observed FCGRs in hydrogen charged steel were higher than for specimens fully immersed in the sour environment. This is believed to be due to reduced environmental crack closure/blunting effects; the steel is charged with hydrogen, but there is no active corrosion process occurring inside the crack. The results of the present study indicate that the use of an air FCG curve for embedded (or external) flaws located in hydrogen charged steel may be non-conservative. Further work is required to establish the relationship between FCGR and hydrogen concentration in steel and to evaluate the implications for pipeline ECA calculations.

Fracture Mechanics Analysis of Aero-Engine Compressor Disc

2013 ◽  
Author(s):  
K. M. Sathish Kumar ◽  
G. V. Naveen Prakash ◽  
K. K. Pavan Kumar ◽  
H. V. Lakshminarayana
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Growth ◽  
Stable Crack Growth

Fracture is a natural reaction of solids to relieve stress and shed excess energy. The design philosophy envisions sufficient strength and structural integrity of the aircraft to sustain major damage and to avoid catastrophic failure. However there are inherent limitations in the methodology, resulting in significant under utilization of component lives and an inability to account for non-representative factors. Ductile materials used in aircraft engine are likely to experience fatigue and stable crack growth before the occurrence of fast fracture and final failure. Fatigue crack propagation can be characterized by a crack growth-rate model that predicts the number of loading cycles required to propagate a fatigue crack to a critical size. Stress Intensity Factors under fatigue loading are below the critical value for quasi-static or unstable crack propagation. Under these circumstances, Linear Elastic Fracture Mechanics helps to characterize the crack growth-rate model. Stable crack growth and final failure generally occur at the very last loading cycle of the life of aircraft. Crack propagation at this stage involves elastic-plastic stable tearing followed by fast-fracture. Since crack growth is no longer under small-scale yielding conditions, Elastic-Plastic Fracture Mechanics is needed to characterize the fracture behavior and to predict the residual strength. The most likely places for crack initiating and development are bolt holes in a compressor disk. Such cracks may grow in time leading to a loss of strength and reduction of the life time of the disc. The objective of this work is to determine Stress Intensity Factor for a crack emanating from a bolt hole in a disk and approaching shaft hole. The objective is achieved by developing a 2D finite element model of a disk with bolt holes subjected to a centrifugal loading. It was observed that stress concentration at the holes has a strong influence on the value of Stress Intensity Factor. Also, fatigue life prediction was carried out using AFGROW software. Different fatigue crack growth laws were compared. This provides necessary information for subsequent studies, especially for fatigue loads, where stress intensity factor is necessary for the crack growth rate determination and prediction of residual strength.

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