Compression and Shear Fracture Analysis of Boundary Cracks Containing Water in Rock

In order to conserve the water resource during underground mining, the fracture and mechanical properties of rock are important for the stability of water-resisting layers, especially for the fracture behavior of boundary cracks containing water in rock. Considering the swelling of rock under water environment and the influence of water on rock, the stress intensity factors of modes I and II are derived for boundary cracks in rock under compressive and shear stresses. The cracks are divided into the closed and open states. The effects of the crack inclination angle, friction coefficient between crack surfaces, and initial crack length on stress intensity factors are also taken into account. The stress intensity factors for closed and open boundary cracks are verified by numerical and physical experiments, respectively, and the deviation of the results is within 5%. It is shown that pore pressure has different effects on the relationship between stress intensity factor and friction coefficient under different lateral pressures. The effect of water on crack propagation is mainly due to the deterioration of the fracture toughness of the rock. It is found that the critical coefficient λc is a key parameter to determine whether the boundary crack propagates in rock under compression-shear stress. Further studies should be performed to apply the present fracture theory to rock mass or water-resisting layers.

Download Full-text

Reliability Analysis of the Cracked Ag-SU8 Interface on the Channel Wall in a Micro-PEMFC

ASME 2006 Fourth International Conference on Fuel Cell Science, Engineering and Technology, Parts A and B ◽

10.1115/fuelcell2006-97046 ◽

2006 ◽

Author(s):

Chi-Hui Chien ◽

Yi-San Shih ◽

Shou-Shing Hsieh ◽

Huang-Hsiu Tsai ◽

Chih-Wei Lin ◽

...

Keyword(s):

Stress Intensity ◽

Crack Length ◽

Stress Intensity Factors ◽

Channel Wall ◽

Crack Tip ◽

Electrochemical Process ◽

Shear Stresses ◽

Intensity Factors ◽

Compressive Stresses ◽

And Performance

The efficiency of the fuel cell depends on both the kinetics of the electrochemical process and performance of the components. The main aim of this research is to analysis the reliability of the cracked Ag-SU8 interface on the channel wall in a micro-PEMFC. An existed surface crack on the channel wall subjected to the flow induced compressive stresses and shear stresses will propagate and lead to the spall formation. In this paper, at first, the flow induced compressive and shear stresses are obtained through simulation of stress state and flow-field in the micro-channel by commercial package software ANSYS® 8.0. Then, the stresses arising at the crack tip due to flow induced compressive and shear stresses can be calculated and characterized by the mode I and II stress intensity factors (SIF), KI and KII, respectively. Finally, the KI and KII stress intensity factors at the crack tip are computed for the different crack sizes and loadings. The results show that the inlet pressure and crack length affect the stress intensity factors more than the inlet velocity does. Also, the results show that as the crack length increases, the value of KI will increase, but the value of KII decreases slightly.

Download Full-text

Stress Intensity Factors for Multiple Cracks in an Adhesively Bonded Sandwich Sheet

Journal of Engineering Materials and Technology ◽

10.1115/1.2902146 ◽

1993 ◽

Vol 115 (1) ◽

pp. 134-139 ◽

Cited By ~ 2

Author(s):

T. Nishimura

Keyword(s):

Stress Intensity ◽

Stress Intensity Factors ◽

Mutual Interaction ◽

Fredholm Integral Equations ◽

Multiple Cracks ◽

Shear Stresses ◽

Basic Solution ◽

Intensity Factors ◽

Adhesively Bonded ◽

Sandwich Sheet

A new method is proposed for analyzing stress intensity factors of multiple cracks in an adhesively bonded metallic sandwich sheet. Using a basic solution of a single crack and taking unknown density of surface tractions and adhesive shear stresses, Fredholm integral equations and compatibility equations are formulated based upon stress free condition along each crack and displacement continuity between the sheets and adhesive layers, respectively. These equations are solved simultaneously, and the stress intensity factors of multiple cracks are determined from the derived density of tractions. It is shown that the mutual interaction of multiple cracks in a sandwich sheet is smaller than that in a monolithic sheet. Also, mutual interaction of cracks in the same sheet is smaller than that of cracks in the different sheets.

Download Full-text

Stress intensity factors in fretting fatigue

The Journal of Strain Analysis for Engineering Design ◽

10.1243/03093247v141001 ◽

1979 ◽

Vol 14 (1) ◽

pp. 1-6 ◽

Cited By ~ 48

Author(s):

D P Rooke ◽

D A Jones

Keyword(s):

Stress Intensity ◽

Crack Length ◽

Stress Intensity Factors ◽

Polynomial Function ◽

Fretting Fatigue ◽

Mode I ◽

Mode Ii ◽

Shear Stresses ◽

Intensity Factors ◽

Tangential Forces

Solutions are derived for mode I and mode II stress intensity factors for a crack at the edge of a sheet subjected to localized fretting forces. Both normal and tangential forces are considered. These solutions are approximated by a polynomial function of crack length, which is then used as a Green's function to derive stress intensity factors for arbitrary distributions of tensile and shear stresses at the edge of the sheet.

Download Full-text

Uniform Arrays of Unequal-Depth Cracks in Thick-Walled Cylindrical Pressure Vessels—Part I: Stress Intensity Factors Evaluation

Journal of Pressure Vessel Technology ◽

10.1115/1.2929887 ◽

1990 ◽

Vol 112 (4) ◽

pp. 340-345 ◽

Cited By ~ 7

Author(s):

M. Perl ◽

K. H. Wu ◽

R. Arone´

Keyword(s):

Stress Intensity ◽

Stress Intensity Factors ◽

Initial Crack ◽

Pressure Vessels ◽

Intensity Factors ◽

Interaction Range ◽

Sequence Of Events ◽

Wide Range ◽

Final Failure ◽

Level Model

The influence of the unevenness of crack lengths on the mode I stress intensity factors (SIF) for large uniform arrays of radial cracks of unequal depth in thick-walled pressurized cylinders is investigated applying the previously proposed “two-crack-length level model.” Using the finite element method, SIFs are evaluated for numerous configurations of crack arrays bearing a wide range of crack lengths. The interaction range for various combinations of crack arrays and crack lengths is then determined. The numerical results anticipate that any statistical unevenness of the initial crack lengths, prevailing in the pressurized cylinder, will be amplified during the process of fatigue crack growth. Thus, while the fatigue life of the vessel is determined by a large number of cracks, its final failure, which is governed by a small number of the largest cracks, is likely to be caused by one major crack, as is usually the case. This sequence of events results from the particular nature of the inter-crack stress field, which is analyzed and discussed in detail in Part II of the paper.

Download Full-text

The Elliptical Crack Subjected to Nonuniform Shear Loading

Journal of Applied Mechanics ◽

10.1115/1.3423317 ◽

1974 ◽

Vol 41 (2) ◽

pp. 502-506 ◽

Cited By ~ 13

Author(s):

F. W. Smith ◽

D. R. Sorensen

Keyword(s):

Stress Intensity ◽

Stress Intensity Factors ◽

Crack Surface ◽

Shear Loading ◽

Elliptical Crack ◽

Graphical Form ◽

Shear Stresses ◽

Intensity Factors ◽

Degree Polynomial

The equations of elasticity are solved for the problem of a flat elliptical crack which has nonuniform shear stresses applied to its surfaces. The shear stresses are prescribed independently in two directions on the crack surface and are expressed in the form of a third-degree polynomial. Mode two and mode three stress-intensity factors are presented in analytical and graphical form as functions of position along the crack border.

Download Full-text