Computation of Crack Tip Mode I Stress Intensity Factor of a Specimen for Measuring Slow Crack Growth Resistance of Plastic Pipes Using Finite-Element Method

The asphalt surface crack fracture mainly includes load cracks and non-load cracks. The former is due to the weight of the vehicle itself causing excessive fatigue weight, therefore, this crack is also known as road load fatigue crack. Non-load crack is affected by nature factors such as temperature and humidity, which makes the road structure cracking. In this paper, finite element method is used to analyze the transient temperature field, and on this basis, the temperature stress simulation of pavement structure is carried out. The stress intensity factor of asphalt surface crack tip is analyzed by finite element method. The results show that the modulus of the surface and the base layer and the increase of the temperature coefficient of the base layer will lead to the increase of the stress intensity factor of the crack tip. The temperature coefficient of the surface layer has no obvious effect on the stress intensity factor. In addition, increasing the thickness of the surface layer can effectively reduce the stress intensity factor at the crack tip. The paper also concludes that the gravel base can effectively slow down the expansion of the road refection crack.

Download Full-text

Crack Growth Resistance of Carbide Reinforced Composite Ceramics Based on Alumina

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.409.231 ◽

2009 ◽

Vol 409 ◽

pp. 231-236

Author(s):

Magdalena Szutkowska ◽

Marek Boniecki

Keyword(s):

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Crack Length ◽

Crack Growth ◽

Slow Crack Growth ◽

Crack Growth Resistance ◽

Bending Test ◽

Special Device ◽

Three Point Bending

The relationship of KR versus crack length c (R curve) for Al2O3-30wt.% Ti(C,N).and for comparison alumina ceramics has been examined. The R-curve has been evaluated using pronounced long-crack formed during the three point bending (3PB) of the double edge notched beam. A combination of in situ microscopic crack growth observation and mechanical testing enabled measurement of crack growth resistance curves. The special device consisting of light microscope coupled with CCD camera, was fitted to Zwick 1446 testing machine. These observations reveal the existence of flat R-curve for Al2O3-30wt.% Ti(CN) and increasing R-curve for pure alumina. A study of slow-crack-growth (SCG) in tested materials was carried. The load-relaxation technique was used for observation at slow-crack-growth. The crack length was evaluated by linear-elastic analysis from the compliance of single-edge-notched specimen in three-point bending test. Parameters of stable crack growth n and logA, work-of fracture (WOF), stress intensity factor at the moment of crack initiation KI0 and maximum values of stress intensity factor KImax were determined. Mechanism of grain bridging responsible for occurrence of R-curve was observed by SEM and TEM.

Download Full-text

Direct Measurements of Fracture Toughness and Crack Growth in Polysilicon MEMS

MRS Proceedings ◽

10.1557/proc-854-u10.6 ◽

2004 ◽

Vol 854 ◽

Author(s):

I. Chasiotis ◽

S.W. Cho ◽

K. Jonnalagadda

Keyword(s):

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Crack Growth ◽

Critical Stress ◽

Polycrystalline Silicon ◽

Crack Tip ◽

Critical Stress Intensity Factor ◽

Mode I ◽

Direct Measurements

ABSTRACTDirect measurements of Mode-I critical stress intensity factor and crack tip displacements were conducted in the vicinity of atomically sharp edge cracks in polycrystalline silicon MEMS using our in situ Atomic Force Microscopy (AFM)/Digital Image Correlation (DIC) method. The average Mode-I critical stress intensity factor for various fabrication runs was 1.00 ± 0.1 MPa√m. The experimental crack tip displacement fields were in very good agreement with linear elastic fracture mechanics solutions. By means of an AFM, direct experimental evidence of incremental crack growth in polycrystalline silicon was obtained for the first time via spatially resolved crack growth measurements. The incremental crack growth in brittle polysilicon is attributed to its locally anisotropic polycrystalline structure which also results in different local and macroscopic (apparent) stress intensity factors.

Download Full-text

Application of Extended Finite Element Method (XFEM) to Stress Intensity Factor Calculations

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2015-45032 ◽

2015 ◽

Cited By ~ 1

Author(s):

Do-Jun Shim ◽

Mohammed Uddin ◽

Sureshkumar Kalyanam ◽

Frederick Brust ◽

Bruce Young

Keyword(s):

Finite Element Method ◽

Stress Intensity Factor ◽

Finite Element ◽

Stress Intensity ◽

Intensity Factor ◽

Degrees Of Freedom ◽

Extended Finite Element Method ◽

Partition Of Unity ◽

Extended Finite Element ◽

Element Method

The extended finite element method (XFEM) is an extension of the conventional finite element method based on the concept of partition of unity. In this method, the presence of a crack is ensured by the special enriched functions in conjunction with additional degrees of freedom. This approach also removes the requirement for explicitly defining the crack front or specifying the virtual crack extension direction when evaluating the contour integral. In this paper, stress intensity factors (SIF) for various crack types in plates and pipes were calculated using the XFEM embedded in ABAQUS. These results were compared against handbook solutions, results from conventional finite element method, and results obtained from finite element alternating method (FEAM). Based on these results, applicability of the ABAQUS XFEM to stress intensity factor calculations was investigated. Discussions are provided on the advantages and limitations of the XFEM.

Download Full-text

Slow Crack Growth in Glasses and Ceramics Under Residual and Applied Stresses

Journal of Electronic Packaging ◽

10.1115/1.3226510 ◽

1989 ◽

Vol 111 (1) ◽

pp. 61-67 ◽

Cited By ~ 3

Author(s):

F. Erdogan

Keyword(s):

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Residual Stresses ◽

Crack Growth ◽

Slow Crack Growth ◽

Threshold Value ◽

Crack Arrest ◽

Growing Crack ◽

Applied Stresses

The problem of slow crack growth under residual stresses and externally applied loads in plates is considered. Even though the technique developed to treat the problem is quite general, in the solution given it is assumed that the plate contains a surface crack and the residual stresses are compressive near and at the surfaces and tensile in the interior. The crack would start growing subcritically when the stress intensity factor exceeds a threshold value. Initially the crack faces near the plate surface would remain closed. A crack-contact problem would, therefore, have to be solved to calculate the stress intensity factor. Depending on the relative magnitudes of the residual and applied stresses and the threshold and critical stress intensity factors, the subcritically growing crack would either be arrested or become unstable. The problem is solved and examples showing the time to crack arrest or failure are discussed.

Download Full-text