NUMERICAL PARAMETRIC STUDY OF CRACK PARAMETERS NEAR CRACK TIP (original) (raw)
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NATO Science for Peace and Security Series C: Environmental Security, 2011
In the present research, T-stress solutions are provided for a U-shaped notch in the case of four specimens: CT, DCB, SENT and Romain Tile (RT). The U-shaped notch is analyzed using the finite element method to determine the stress distribution ahead of the notch tip. In contrast to a crack, it was found that the T-stress is not constant and depends on distance from the notch-tip. To estimate the T-stress in the case of a notch, a novel method, namely, method of line, inspired from the volumetric method approach proposed by Pluvinage has been developed. Thus, the two-parameter approach was adopted for the notch two-parameter fracture mechanics in terms of the notch stress intensity factor Krc and the effective (average) T-stress, Tef. Fracture toughness transferability curve (Krc -Tef) of X52 pipe steels has been established. of theories which extend significantly the range of deformation over which fracture can be applied accurately to predict the load capability of a given structure. In this way, recent numerical and experimental studies have attempted to describe fracture in terms of two or three fracture parameters [1]. One of candidate parameters is the elastic T-term stress . The T-stress is not singular as r ! 0, but is can alter the elastic crack-tip stress state described by the stress intensity factor K I . The T-stress is a function of geometry, loading conditions, and is proportional to the nominal applied stress . Sufficient information about the stress state is available, if the Stress Intensity Factor, SIF and the constant stress term, the T-stress, are know. While SIF solutions are reported in handbooks for many crack geometries and loading cases, T-stress solutions are available only for a small number of test specimens and simple loading cases for instance pure tension and bending.
Effect of Crack Length to Plate Width Ratio on Stress Intensity Distribution at the Crack Tip
Industrial Engineering Letters, 2017
To start the comprehending of the materials fracture, first must understand the stress fields and deformation distribution at the crack tips. Analysis the behavior of crack for a solid plate may be extensive importance of the plate design to evade the failure. The crack is small when rivalled to the dimension of solid plate and the smallest crack ligament to the exterior plate region is greatly than the crack can be estimated for an infinite plate with finite crack. The variant of the stress field and stress intensity distribution is not great in profile compared with the variation in values. The result evaluated using finite element method to analysis by using Ansys Parametric Design Language (APDL) code in Ansys v.11 with static analysis at two different cases for carbon steel material alloy. In the first case, tension load applied at the upper edge of the plate model and in the second case, shear load applied at the upper edge. The results extracted from the current study show in...
The effects of crack inclination angle and crack length on the through-thickness mode I (KI), mode II (KII), and effective (í µí°¾í µí°¾ í µí±í µí±í µí± = �í µí°¾í µí°¾ í µí°¼ 2 + í µí°¾í µí°¾ í µí°¼í µí°¼ 2) stress intensity factors (SIFs) have been analyzed by using three dimensional finite element analysis (3D FEA). Edge crack in semi circular bend specimen (SCB) was utilized in this investigation. The mode of mixity (Me) values are equal to 1 (pure mode I), 0.75, 0.5, 0.25, and 0 (pure mode II). The crack length ratio, crack length/specimen radius (a/R), ranging from 0.1 to 0.7 by step equal to0.1 has been studied. In SCB specimen, the mode I geometry correction factor (YI) decreased by increasing the crack length for all values of mode of mixity, while, in the case of Me = 1 & 0.75 YI reached its minimum value at a/R ≈ 0.3 then YI increased by increasing the crack length. For all values of Me, Keff increased with the increasing crack length. However, the increment of increment in Keff for a/R ≤ 0.3 is lower than that for a/R > 0.3.
Crack tip opening displacement (CTOD) in single edge notched bend (SEN(B))
2018
This thesis investigates the quantity Crack Tip Opening Displacement (CTOD) as a means to assess fracture toughness when measured in the Single Edge Notched Bend (SENB) specimen setup. A particular objective is to assess the effectiveness of the test when used for high strain-hardening materials (e.g. stainless steels). This has been an increasing concern as the current available methods were generally designed for lower strain hardening structural steel. Experimental work on CTOD tests included silicone casting of the crack, and constant displacement tests were also performed. The silicone castings enable physical measurement of the crack under an optical microscope. Results from a series of Finite Element (FE) models were validated from the experiments. δ5 surface measurements were obtained using Digital Image Correlation (DIC) as a courtesy of TWI, which were compared to surface CTOD measurements from the silicone castings. In addition to the experiments and Finite Element modell...
Estimations of Stress Intensity Factors for Small Cracks at Notches
Fatigue & Fracture of Engineering Materials and Structures, 1991
This paper presents a simple method for determining the stress intensity factors for small notch-emanating cracks. The proposed method is based on similarities between elastic notch-tip stress fields described by two parameters; the stress concentration factor K, and the notch-tip radius p. The method developed here is rather general, and can be used for a variety of central and edge notches with through-thickness of semi-elliptical cracks. The predicted values are in good agreement with the available numerical data.
Crack-tip stresses and their effect on stress intensity factor for crack propagation
Engineering Fracture Mechanics, 2008
In this paper, analytical and numerical simulations of the crack-tip stresses are presented. Analytical calculations are performed utilizing modified Rice and elastic equations. 2D finite element analyses (FEA) are conducted in parallel using ANSYS. Results from both methods are compared and discussed in terms of the crack-tip compressive residual stresses. Then, the effect of the compressive residual stresses is quantified in terms of the stress intensity factor for crack propagation, K PR , using 'clamping force' method. The comparison between the calculated K PR values and those obtained experimentally by Lang demonstrates a fairly good agreement. Both the present results and Lang data independently support a two-parameter, K maxTH and DK TH , description of the threshold condition for fatigue crack propagation.
ESTIMATION OF STRESS INTENSITY FACTOR (SIF) ON CRACK COMPONENT BY USING FINITE ELEMENT ANALYSIS
Theoretical solutions are available for idealized cases such as Infinite flat plate with edge crack, central crack etc. However main limitation of these theoretical solutions is they are very restrictive and while analyzing a normal component, a lot of assumptions go into it. Finite Element Analysis on the other hand provides good tool to determine Stress Intensity Factor. Cracks generally initiate at geometric discontinuities (such as notches, holes, weld toes, voids etc.) that induce large stress (stress concentration). Since crack growth is related to the effective stress intensity factor (SIF) which is at crack tip, the evaluation of Stress Intensity Factors. The present work would aim to fulfill this gap and generate more information thereby increased understanding on fracture behavior in 3D Components. Finite element analysis has been performed to support the results on fracture parameters like Location and Size of Cracks and results has been compared with available theoretical solutions. It is concluded that magnitude of critical Stress Intensity Factor can be used as a fracture criterion for thin Plates. Same procedure has been adapted for Analysis of connecting rod to find Stress Intensity Factor at various lengths of crack
Impact of specific fracture energy investigated in front of the crack tip of t.PDF
Presented study is focused on the analysis of the dependence of the specific fracture energy value on the assumed work of fracture in threepoint bending tests. Specimens of different sizes and relative notch lengths are assumed in this study, in order to take into account the size effect. The three-point bending test of cracked specimens is simulated numerically by means of commercial software based on the finite element method with implemented cohesive crack model. Three levels of the specific fracture energy are considered.
The Theoretical Value for the Tip Radius of Cracks and Notches
Mechanika, 2022
In this paper, an additional equation that can be used in conjunction with the Stress Intensity Factor is pro- duced, enabling the determination of all critical fracture stresses, including tensile strength, from only one mechani- cal test data. In this context, the blind elliptical hole stress distribution area equation of Creager and Paris was used and the theoretical radius value was selected to ensure that the maximum principal stress (in MPa) at the tip point and the fracture toughness (in MPa.mm1/2) were equal in value. By using the obtained equation together with the stress intensity factor, the results very close to the experimental data were obtained in the test specimens with cracks and holes, regard- less of the true radius of the crack tip.