Crack Propagation in a Strain-Crystallizing Elastomer

1962 ◽  
Vol 35 (1) ◽  
pp. 210-223 ◽  
Author(s):  
E. H. Andrews
Keyword(s):  
Stress Distribution ◽  
Crack Propagation ◽  
Natural Rubber ◽  
Crack Growth ◽  
Cyclic Deformation ◽  
Maximum Stress ◽  
Applied Strain ◽  
Small Scale ◽  
Mechanical Hysteresis ◽  
Axis Of Symmetry

Abstract The dependence of small-scale crack propagation in a strain-crystallizing elastomer (natural rubber) upon the applied strain has been studied under conditions of cyclic deformation over a range of frequencies. During each cycle the crack propagates along a well-defined path, different from the axis of symmetry, which is identified as the locus of maximum stress in a stationary stress distribution (i.e., one which does not move with small advances of the crack). The stationary stress hypothesis also accounts for the quantitative dependence of crack growth upon the external constraint. It is shown that a stationary stress distribution could arise as a result of the severe mechanical hysteresis displayed by strain-crystallizing rubbers.

Crack Growth During Full Scale Reeling Simulation of Pipes With Girth Welds

2004 ◽  
Author(s):  
Oddvin O¨rjasaeter ◽  
Olav Jan Hauge ◽  
Guy Ba¨rs ◽  
Per Egil Kvaale
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
High Strain ◽  
High Stress ◽  
Strain Range ◽  
Full Scale ◽  
Small Scale ◽  
Final Fracture ◽  
Lack Of Fusion ◽  
Girth Welds

Installation of pipelines by reeling has proved to be an effective method. However, the pipe bending results in very high stress and strain and cannot be handled by conventional design rules, as stated in design codes, e.g. [2]: High strain crack growth must be assessed according to specific case-by-case selected criterions. In the present work the performance of 10” and 12 3/4” pipes with typical weld defects is studied — from initiation of cracks at notches to final fracture. Information was obtained from several sources: full scale cyclic bending of pipes, FE simulations, and small-scale tests. The plasticity during reeling operations results in substantial non-linear behavior due to varying cross section properties, cyclic creep, and different material response at tensile and compression side of the pipe. Hence, a full scale reeling simulation must be carefully planned and include sufficient tolerances. Critical cracks in pipe girth welds initiate mainly from the surface (undercuts, lack of penetration, or lack of fusion), but potentially also internally (lack of fusion or large pores). Various configurations of these parameters were investigated in full scale pipe tests. It was possible to verify both crack propagation during the reeling cycles, and the point of final fracture (for ECA verifications). In pipe design on must assure safe conditions for both reeling operations and for later in-service loading. Proper design tools must be available. Several methods for high strain crack growth analysis were considered and also compared to small-scale specimen data. Conventional strain-life methodology failed to predict the crack propagation accurately. A new approach including a tensile strain range parameter offered promising results.

On the Influence of the Corner Singularity on Kinking Mixed-Mode Crack Propagation

2007 ◽  
Vol 348-349 ◽  
pp. 585-588
Author(s):  
Henning Schütte ◽  
Kianoush Molla-Abbasi
Keyword(s):  
Stress Intensity ◽  
Crack Propagation ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Mixed Mode ◽  
Small Scale ◽  
Intensity Factors ◽  
Plastic Energy ◽  
Mixed Mode Crack ◽  
The Impact

The aim of the presentation is to highlight the influence of the kink, developing at the beginning of mixed-mode crack growth, on the propagation behavior of the crack. Le et al. [1] have shown that the variational principle of a body containing a crack results in the principle of maximum energy release rate incorporating the stress intensity factors of the kinked crack. Here the influence of the kink and the kinking angle, resulting in a singular field around the corner, on the crack growth is analyzed. The generalized stress intensity factors at the kinks corner are computed with the help of a FEM strategy. The influence of these on the T-stresses and the plastic energy dissipated at the kink is determined using a small scale yielding approach. The impact of these results on mixed-mode crack propagation is discussed.

Experimental Study on Fatigue Crack Propagation of Glare3-3/2 with Mechanics Properties

2012 ◽  
Vol 600 ◽  
pp. 273-278
Author(s):  
Zong Hong Xie ◽  
Tian Jiao Zhao ◽  
Rui Wu
Keyword(s):  
Growth Rate ◽  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Stress Level ◽  
Maximum Stress ◽  
Fatigue Tests

This study is to investigate the fatigue crack growth behavior of Glare3-3/2 under various stress levels. The Glare3-3/2 specimen consists of three 2024-T3 aluminum alloy sheets and two layers of glass/epoxy composite lamina. Tensile-tensile cyclic fatigue tests were conducted on centrally notched specimen at four stress levels with various maximum values. A digital camera system was used to take photos of the propagating cracks on both sides of the specimen. Image processing software was adopted to accurately measure the length of the cracks on each photo. The test results show that 1) Compared to 2024-T3 aluminum alloy, the fatigue properties of Glare3-3/2 are much better: under the same loading condition with maximum stress level of 120MPa, the crack growth rate of Glare3-3/2 is roughly 5% of the corresponding value of 2024-T3 aluminum alloy, while the fatigue life is 4 times higher than that of 2024-T3 aluminum alloy. 2) The maximum stress level shows strong influence on fatigue crack propagation behavior of Glare3-3/2. The value of steady state crack growth rate increases linearly, while the number of load cycles decreases exponentially, with respect to the maximum stress values used in the fatigue tests.

Steady State Crack Growth in Shape Memory Alloys

2013 ◽  
Author(s):  
Selcuk Hazar ◽  
Wael Zaki ◽  
Ziad Moumni ◽  
Gunay Anlas
Keyword(s):  
Steady State ◽  
Stress Distribution ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Crack Growth ◽  
Crack Tip ◽  
Reverse Transformation ◽  
Small Scale ◽  
Local Algorithms ◽  
Non Local

Shape memory alloys experience phase transformation from austenite to martensite around crack tip. When the crack advances, martensitic transformation occurs at the tip and the energy that goes into transformation results in stable crack growth like in the case of plastic deformation. In literature, there are studies on steady-state crack growth in elasto-plastic materials with small scale yielding around crack tip that use stationary movement methods similar to non-local algorithms. In this work, Mode I steady-state crack growth in an edge cracked Nitinol plate is modeled using a non-local stationary movement method. The Zaki-Moumni (ZM) constitutive model is utilized for this purpose. The model is implemented in ABAQUS by means of a user-defined material subroutine (UMAT) to determine transformation zones around the crack tip. Steady-state crack growth is first simulated without considering reverse transformation to calculate the effect of transformation on stress distribution in the wake region, then reverse transformation is taken into account. Stress distribution and transformation regions calculated for both cases are compared to results obtained for the case of a static crack.

An Interpretation of the Mechanics of Crack Growth by Fatigue

1965 ◽  
Vol 87 (1) ◽  
pp. 230-236 ◽  
Author(s):  
B. Cotterell
Keyword(s):  
Brittle Fracture ◽  
Crack Propagation ◽  
Crack Length ◽  
Crack Growth ◽  
Driving Force ◽  
Maximum Stress ◽  
High Strength ◽  
Crack Driving Force

A theory for the growth of cracks by fatigue is developed that is analogous to the brittle fracture of high strength materials. It is argued that it is possible to describe crack growth with a curve of resistance which is dependent on the alternating stress at low rates of crack propagation. At higher rates there is much less dependency on the alternating stress. Once such curves have been prepared the rate of crack growth can be found from the value of the crack driving force. This force is dependent mainly on the maximum stress and crack length.

scholarly journals Cyclic Deformation Induced Residual Stress Evolution and 3D Short Fatigue Crack Growth Investigated by Advanced Synchrotron Tomography Techniques

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1562
Author(s):  
Benjamin Dönges ◽  
Melanie Syha ◽  
Anne K. Hüsecken ◽  
Ullrich Pietsch ◽  
Wolfgang Ludwig ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Crack Growth ◽  
Cyclic Deformation ◽  
Phase Contrast ◽  
Crack Nucleation ◽  
Short Fatigue Crack ◽  
Phase Contrast Tomography

Diffraction and phase contrast tomography techniques were successfully applied to an austenitic–ferritic duplex stainless steel representing exemplarily a metallic material containing two phases with different crystal structures. The reconstructed volumes of both phases were discretized by finite elements. A crystal plasticity finite-element analysis was executed in order to simulate the development of the experimentally determined first and second order residual stresses, which built up due to the manufacturing process of the material. Cyclic deformation simulations showed the single-grain-resolved evolution of initial residual stresses in both phases and were found to be in good agreement with the experimental results. Solely in ferritic grains, residual stresses built up due to cyclic deformation, which promoted crack nucleation in this phase. Furthermore, phase contrast tomography was applied in order to analyze the mechanisms of fatigue crack nucleation and short fatigue crack propagation three-dimensionally and nondestructively. The results clearly showed the significance of microstructural barriers for short fatigue crack growth at the surface, as well as into the material. The investigation presented aims for a better understanding of the three-dimensional mechanisms governing short fatigue crack propagation and, in particular, the effect of residual stresses on these mechanisms. The final goal was to generate tailored microstructures for improved fatigue resistance and enhanced fatigue life.

The Measurement Method of Internal Residual Stress Distribution Concerned with Fatigue Crack Growth

2016 ◽  
Vol 85 (2) ◽  
pp. 216-220
Author(s):  
Shinji KAWAI ◽  
Takuya NAGAI ◽  
Shigetaka OKANO ◽  
Masahito MOCHIZUKI
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Stress Distribution ◽  
Crack Growth ◽  
Measurement Method ◽  
Residual Stress Distribution

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

scholarly journals Dynamic characteristics and fractal representations of crack propagation of rock with different fissures under multiple impact loadings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bing Sun ◽  
Shun Liu ◽  
Sheng Zeng ◽  
Shanyong Wang ◽  
Shaoping Wang
Keyword(s):  
Fractal Dimension ◽  
Crack Propagation ◽  
Crack Growth ◽  
Impact Test ◽  
Fractal Theory ◽  
Dynamic Change ◽  
Fractal Dimensions ◽  
Peak Stress ◽  
Dynamic Mechanical Properties ◽  
Gravitational Potential Energy

AbstractTo investigate the influence of the fissure morphology on the dynamic mechanical properties of the rock and the crack propagation, a drop hammer impact test device was used to conduct impact failure tests on sandstones with different fissure numbers and fissure dips, simultaneously recorded the crack growth after each impact. The box fractal dimension is used to quantitatively analyze the dynamic change in the sandstone cracks and a fractal model of crack growth over time is established based on fractal theory. The results demonstrate that under impact test conditions of the same mass and different heights, the energy absorbed by sandstone accounts for about 26.7% of the gravitational potential energy. But at the same height and different mass, the energy absorbed by the sandstone accounts for about 68.6% of the total energy. As the fissure dip increases and the number of fissures increases, the dynamic peak stress and dynamic elastic modulus of the fractured sandstone gradually decrease. The fractal dimensions of crack evolution tend to increase with time as a whole and assume as a parabolic. Except for one fissure, 60° and 90° specimens, with the extension of time, the increase rate of fractal dimension is decreasing correspondingly.

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