Fracture Modeling of an Embedded Crack in Self-Healing Polymers

2012 ◽  
Author(s):  
Mohammad H. Malakooti ◽  
Henry A. Sodano
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Shape Memory ◽  
Healing Process ◽  
Crack Tip ◽  
Original Material ◽  
Self Healing ◽  
Element Analysis ◽  
Elastic Gradient

The healing process exhibited by biological structures has inspired the creation of engineered materials capable of mimicking this behavior, providing adaption to impeding crack propagation and subsequently healing it. Recently, a new approach to self-healing was devised in which a sensing network was combined with shape memory polymers (SMPs) to allow the controlled response of the material to damage. The system was designed such that in the presence of a crack the polymer locally modified its modulus to toughen the damaged region and arrest crack growth. This process is followed by the shape memory response, closing the crack and healing the system. This paper will study the mechanics of the toughening portion of this self-healing system and specifically develop models to predict the stress intensity factor of a crack tip in a nonhomogeneous inclusion. The models will be formulated using finite element analysis (FEA) and a single inclusion model based on Eshelby’s equivalent theory with the elastic gradient defined by a point source thermal load. It will be shown that as the temperature of the crack tip passes the glass transition temperature of the polymer, the stress intensity factor at crack tip decreases to 95% of the original material stress intensity factor. This is due to the formed elastic gradient and deflection of the stress concentration away from the crack tip into the bulk polymer.

Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack

2019 ◽  
Author(s):  
Curtis Sifford ◽  
Ali Shirani
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Element Analysis

Abstract This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.

Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack

2018 ◽  
Author(s):  
Curtis Sifford ◽  
Ali Shirani
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Element Analysis

This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.

Finite Element Analysis on the Stress Intensity Factor under Combined Bending and Torsion Loading

2011 ◽  
Vol 462-463 ◽  
pp. 1325-1330
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
M. Abdulrazzaq
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Depth ◽  
Crack Tip ◽  
Fe Model ◽  
Element Analysis ◽  
Loading Ratio

The stress intensity factor (SIF) under the combined bending and torsion loading were studied using a finite element (FE) analysis ANSYS. A 20-node iso-parametric element was used to model the crack tip and the square-root singularity of stress/strain was employed by shifting the mid-side node to the ¼ position to the crack tip. Different crack geometries and loading ratios were used and due to the non-symmetrical analysis involved, a full FE model was developed and analyzed. Remotely applied bending and torsion moment were subjected to the FE model and the SIF were then calculated along the crack front under such loadings. The SIF calculated using the finite element analysis (FEA) was compared with those results obtained using an effective combined SIF method. According to the comparisons, the discrepancies were dependent on the normalized coordinate, x/h, the relative crack depth, a/D, the crack aspect ratio, a/b and the loading ratio, .

scholarly journals Stress Intensity Factor Assessment for the Reinforcement of Cracked Steel Plates Using Prestressed or Non-Prestressed Adhesively Bonded CFRP

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1625
Author(s):  
Emilie Lepretre ◽  
Sylvain Chataigner ◽  
Lamine Dieng ◽  
Laurent Gaillet
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Tip ◽  
Steel Plates ◽  
Experimental Investigations ◽  
Adhesively Bonded ◽  
Element Analysis

The use of adhesively bonded carbon fiber reinforced polymer (CFRP) materials to reinforce cracked steel elements has gained widespread acceptance in order to extend the lifespan of metallic structures. This allows an important reduction of the stress intensity factor (SIF) at the crack tip and thus a significant increase of the fatigue life. This paper deals with the assessment of the SIF for repaired cracked steel plates, using semi-empirical analysis and finite element analysis. Metallic plates with only one crack originating from a center hole were investigated. Virtual crack closure technique (VCCT) was used to define and evaluate the stress intensity factor at crack tip. The obtained modeling results are compared with experimental investigations led by the authors for different reinforcement configurations including symmetrical and non-symmetrical reinforcement, normal modulus and ultra-high-modulus CFRP plates, and pre-stressed CFRP plates. Results show that finite element model (FEM) analysis can obviously simulate the fatigue performance of the CFRP bonded steel plates with different reinforcement configurations. Moreover, a parametric analysis of the influence of the pre-stressing level was also conducted. The results show that an increase of the pre-stressing level results in an increase of the fatigue life of the element.

Evaluation of Stress-Intensity Factor of Mixed-Mode Crack by Hybrid Speckle Photography

2002 ◽  
Author(s):  
Kenji Machida
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Mixed Mode ◽  
Least Squares Method ◽  
Processing System ◽  
Crack Tip ◽  
Speckle Photography ◽  
Element Analysis ◽  
Virtual Crack Extension Method

The experiment was conducted on the compact normal and shear (CNS) specimens made of homogeneous and dissimilar materials subjected to mixed-mode loading. Many Young’s fringes patterns around the crack tip were taken and analyzed by the image-processing system developed in my laboratory. The displacement obtained by speckle photography is not as smooth as that obtained by the finite element analysis (FEA). Therefore, the displacement data were smoothed by 2 D FFT filtering and least squares method. The intelligent hybrid method proposed by Nishioka et al. was applied to the stress-strain analysis. Consequently, the stress and strain near the crack tip can be evaluated with high accuracy by the present stress-analyzing system. Then, the stress-intensity factor was evaluated by the virtual crack extension method (VCEM) and displacement extrapolation. The accuracy of stress-intensity factor at the free surface was discussed from both viewpoint of experiment and 3 D FEA.

A new type of cracks adding to Griffith–Irwin cracks

2019 ◽  
Vol 485 (2) ◽  
pp. 162-165
Author(s):  
V. A. Babeshko ◽  
O. M. Babeshko ◽  
O. V. Evdokimova
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Tip ◽  
Stress Concentrations ◽  
New Type

The distinctions in the description of the conditions of cracking of materials are revealed. For Griffith–Irwin cracks, fracture is determined by the magnitude of the stress-intensity factor at the crack tip; in the case of the new type of cracks, fracture occurs due to an increase in the stress concentrations up to singular concentrations.

scholarly journals Optimisation Method for Determination of Crack Tip Position Based on Gauss-Newton Iterative Technique

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Bing Yang ◽  
Zhanjiang Wei ◽  
Zhen Liao ◽  
Shuwei Zhou ◽  
Shoune Xiao ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Plastic Zone ◽  
Relative Error ◽  
Crack Tip ◽  
Image Correlation ◽  
Preconditioned Conjugate Gradient ◽  
Loading Process ◽  
Tip Position

AbstractIn the digital image correlation research of fatigue crack growth rate, the accuracy of the crack tip position determines the accuracy of the calculation of the stress intensity factor, thereby affecting the life prediction. This paper proposes a Gauss-Newton iteration method for solving the crack tip position. The conventional linear fitting method provides an iterative initial solution for this method, and the preconditioned conjugate gradient method is used to solve the ill-conditioned matrix. A noise-added artificial displacement field is used to verify the feasibility of the method, which shows that all parameters can be solved with satisfactory results. The actual stress intensity factor solution case shows that the stress intensity factor value obtained by the method in this paper is very close to the finite element result, and the relative error between the two is only − 0.621%; The Williams coefficient obtained by this method can also better define the contour of the plastic zone at the crack tip, and the maximum relative error with the test plastic zone area is − 11.29%. The relative error between the contour of the plastic zone defined by the conventional method and the area of the experimental plastic zone reached a maximum of 26.05%. The crack tip coordinates, stress intensity factors, and plastic zone contour changes in the loading and unloading phases are explored. The results show that the crack tip change during the loading process is faster than the change during the unloading process; the stress intensity factor during the unloading process under the same load condition is larger than that during the loading process; under the same load, the theoretical plastic zone during the unloading process is higher than that during the loading process.

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