A parametric study for radial cracking in cement under different loading events based on the stress intensity factor

2021 ◽  
pp. 1-35
Author(s):  
Xuelin Dong ◽  
Zhiyin Duan ◽  
Haoyu Dou ◽  
Yinji Ma ◽  
Deli Gao
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Parametric Study ◽  
Fluid Pressure ◽  
Steam Injection ◽  
Co2 Injection ◽  
Cement Interface ◽  
Increased Risk ◽  
Radial Cracks

Abstract Cement is one of the primary barriers in a wellbore and critical to well integrity. Radial cracking is a pervasive failure mode in cement due to the temperature and pressure variation during drilling, completion, or production. This work presents a comprehensive analysis of radial cracking in cement under various loading events. The proposed model estimates the stress intensity factor and fracture surface displacement as indicators for crack propagation and opening, respectively, through a distributed dislocation technique. Three types of radial cracks, divided by their tips terminating at the casing-cement interface, inside cement, or at the cement-formation interface, are considered. Based on this model, we conduct a parametric study for radial cracking under typical loading events such as steam injection, CO2 injection, and high pressure and high temperature (HPHT) drilling. Results indicate that the crack near the casing-cement interface has an increased risk for steam injection and HPHT drilling, while all three types of radial cracks are destructive during CO2 injection. The thermal expansion coefficient of cement is a significant parameter for steam and CO2 injection wells. The fluid pressure and the cement's thickness are crucial to radial cracking under HPHT conditions. Stiffer cement could promote crack opening for steam injection but prohibit the crack deformation for CO2 injection or HPHT wells. Thicker cement would accelerate radial cracking under the three loading events. These findings are helpful in designing cement to maintain long-term integrity.

A Stress Analysis of the Circular Orifice Problem for 2k Periodic Radial Cracks

2015 ◽  
Vol 744-746 ◽  
pp. 1611-1617
Author(s):  
Lu Guan
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Analytical Solution ◽  
Conformal Mapping ◽  
Stress Analysis ◽  
Complex Analysis ◽  
Crack Tip ◽  
Circular Orifice ◽  
Radial Cracks

Using the method of complex analysis, the study investigates the circular orifice problem for 2k periodic radial cracks through constructing conformal mapping, and provides an analytical solution for the crack-tip stress intensity factor (SIF). From this we have simulated the circular orifice problems of cross-shaped cracks, symmetrical eight-cracks, single cracks, symmetrical double-cracks, and symmetrical four-cracks.

Cracks Emanating From a Fluid Filled Void Loaded in Compression: Application to the Bone-Implant Interface

1987 ◽  
Vol 109 (1) ◽  
pp. 55-59 ◽  
Author(s):  
M. H. Santare ◽  
L. M. Keer ◽  
J. L. Lewis
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Numerical Scheme ◽  
Singular Integral Equations ◽  
Orthopedic Implants ◽  
Mode I ◽  
Quadratic Polynomials ◽  
Bone Implant ◽  
Cement Interface

Loosening of orthopedic implants is believed to be caused, in part, by fracture at the bone-cement interface. This loosening occurs even in regions where the interfacial load is primarily compressive. A model is developed whereby cracks can radiate from an elliptical fluid filled void. The incompressible fluid is allowed to penetrate into the cracks when the system is loaded compressively. The mode I stress intensity factor is calculated to test the feasibility of crack growth, and a numerical scheme which uses piecewise quadratic polynomials is used to solve the resulting singular integral equations. The results show the combinations of parameters for which cracks are likely to grow.

Parametric Study on Dynamics of Breathing Cracked Rotor via Laser Scanner

2015 ◽  
Author(s):  
J. Zhao ◽  
H. A. DeSmidt ◽  
M. Peng ◽  
W. Yao
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Parametric Study ◽  
Laser Scanner ◽  
Crack Model ◽  
Transverse Cracks ◽  
Time Step ◽  
Crack Open ◽  
Opening Mode

The study is based on the finite element model which was developed to investigate the nonlinear breathing behavior of transverse cracks in terms of crack location and rotation speed. The crack model is built using the released strain energy concept in fracture mechanics. Zero Stress Intensity Factor (SIF) method is employed to determine the crack closure line at each time step by calculating the stress intensity factor of opening mode for prescribed resolutions in crack area. The crack is considered open at the points where the stress intensity factor for opening mode is larger than zero. The stiffness matrix is updated at every time step by integrating compliant coefficients over instantly calculated crack open area. With the updated stiffness and force matrices, the vibration response at next time step is solved by Newmark integration method. To investigate the effectiveness of laser scanner, parametric study is conducted to analyze the vibration responses collected by the laser scanner with different scanning functions and frequencies. With this model, the displacement or velocity along the shaft can be extracted to form time based data sets for different scanning function or scanning frequency to explore its usefulness for damage identification.

Stress Intensity Factors for Unequal Longitudinal-Radial Cracks in Thick-Walled Cylinders

1991 ◽  
Vol 113 (1) ◽  
pp. 22-27 ◽  
Author(s):  
J. L. Desjardins ◽  
D. J. Burns ◽  
R. Bell ◽  
J. C. Thompson
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Finite Elements ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Two Dimensional ◽  
Intensity Factors ◽  
Radial Cracks ◽  
Good Agreement

Finite elements and two-dimensional photoelasticity have been used to analyze thick-walled cylinders which contain arrays of straight-fronted, longitudinal-radial cracks of unequal depth. The stress intensity factor K1 has been computed for the dominant crack and for some of the surrounding cracks. Cylinders with 2, 4, 6, 8, 16, 36 and 40 cracks have been considered. Good agreement has been obtained between the experimental and the numerical results and, for cylinders with 2 or 4 cracks, with previously published predictions. The results for all of the foregoing cases are used to develop simple, approximate techniques for estimating K1 for the dominant crack, when the total number of cracks is different from those that have been considered herein. Estimates of K1 obtained by these techniques agree well with corresponding finite element results.

An Analytical Theory for Radial Crack Propagation: Application to Spherical Indentation

2013 ◽  
Vol 80 (4) ◽  
Author(s):  
Andrew N. Seagraves ◽  
Raúl A. Radovitzky
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Flaw Size ◽  
Analytical Theory ◽  
Thin Body ◽  
Elastic Membrane ◽  
Spherical Indentation ◽  
Shaped Crack ◽  
Radial Cracks

A simple analytical theory is proposed for estimating the number of radial cracks which will propagate in brittle materials subjected to axisymmetric transverse surface loads. First, an expression is obtained for the stress intensity factor of a traction-free star-shaped crack in an infinite elastic membrane subjected to axisymmetric transverse loads. Combining this relation with the critical stress intensity factor criterion for fracture, an implicit expression is obtained which defines the number of cracks as a function of the applied loading, initial flaw size, and fracture toughness. Based on the form of this expression, we argue that if the initial flaw size is sufficiently small compared to the length scale associated with the loading, then the number of cracks can be determined approximately in closed-form from the analysis of a traction-free star-shaped crack in a thin body subjected to uniform equibiaxial in-plane tension. In an attempt to validate the theory, comparisons are made with spherical micro-indentation experiments of silicon carbide (Wereszczak and Johanns, 2008, “Spherical Indentation of SiC,” Advances in Ceramic Armor II, Wiley, NY, Chap. 4) and good agreement is obtained for the number of radial cracks as a function of indentation load.

Parametric Study of Stress-Intensity Factors in Bonded Composite Stringer Panels

1987 ◽  
Vol 109 (1) ◽  
pp. 36-39
Author(s):  
C. A. Bigelow
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Integral Equations ◽  
Stress Intensity Factors ◽  
Parametric Study ◽  
Crack Tip ◽  
Algebraic Equations ◽  
Intensity Factors ◽  
Variable Theory

Stress-intensity factors are determined for an infinite cracked orthotropic sheet adhesively bonded to an orthotropic stringer. Since the stringer is modeled as a semi-infinite sheet, the solution is most appropriate for a crack tip located near a stringer edge. Both adherends are treated as homogeneous, orthotropic media which are representative of many fiber-reinforced composite materials. The complex variable theory of elasticity was used to obtain a set of integral equations describing the problem. The integral equations are replaced by an equivalent set of algebraic equations, which are solved to obtain the shear stress distribution in the adhesive layer. From these adhesive stresses, the stress-intensity factors are found. A parametric study is conducted to determine the sensitivity of the system to material properties and specimen configuration. Unless the crack tip is very close to or under the stringer, the stress-intensity factor is approximately that of the unstiffened sheet. However, as the crack propagates beneath the stringer, the stress-intensity factor decreases significantly. Increasing the stringer stiffness or the adhesive stiffness also decreases the stress-intensity factor.

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