Mechanics of Fracture in Two-Ply Laminates

1979 ◽  
Vol 52 (1) ◽  
pp. 96-109 ◽  
Author(s):  
R. F. Breidenbach ◽  
G. J. Lake
Keyword(s):  
Growth Rate ◽  
Fracture Mechanics ◽  
Crack Length ◽  
Crack Growth ◽  
Central Region ◽  
Growth Rates ◽  
Strain Energy ◽  
Reasonable Agreement ◽  
Growth Characteristics ◽  
Crack Growth Rates

Abstract This paper describes a study of fracture in two-ply rubber—cord composites subjected to repeated tensile deformations. Under the conditions used, failure occurs predominantly because of the growth of cracks between the plies. A fracture mechanics approach enables the rate of crack growth to be predicted in terms of the elastic properties and dimensions of the laminate, the magnitude of the deformations and the basic crack growth characteristics of the ply rubber. The theory indicates the growth rate to be determined by the strain energy released from the central region of the laminate and to be independent of crack length once this exceeds a small value. The latter feature has been verified experimentally and the magnitudes of the observed crack growth rates are in reasonable agreement with those predicted for various deformation cycles.

Evaluation of SCC Crack Growth Rate in BWR Water Based on Elastic-Plastic Fracture Mechanics Parameters

2015 ◽  
Author(s):  
Masahiro Takanashi ◽  
Yu Itabashi ◽  
Takashi Hirano
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Elastic Plastic ◽  
Crack Growth Rates

This paper presents an applicability of elastic-plastic fracture mechanics parameters for evaluating a crack growth rate of stress corrosion cracking (SCC). Currently linear fracture mechanical approaches have been applied for the SCC crack growth evaluation, even though some cracks due to SCC are found in plastic deformation zones near welding where linear fracture mechanics is no longer applicable. In this paper, the authors have proposed an elastic-plastic parameter “equivalent stress intensity factor KJ” for evaluating the SCC crack growth rate based on the J-integral value, which is valid in both elastic and plastic stress fields. In order to verify the applicability of the evaluation by KJ, SCC crack growth tests were carried out in a simulated boiling water reactor (BWR) water. When the SCC crack growth rate was evaluated by the stress intensity factor K, no linear relationship between the K values and the crack growth rates was observed in the high K-value region, where a small-scale yielding condition was not met. The crack growth rates increased exponentially according to increasing the stress intensity factor to exceed the linear relationship. On the other hand, when the crack growth rate was evaluated by the elastic-plastic parameter KJ, a linear correlation between the KJ values and the crack growth rates was confirmed regardless the specimen size and the stress condition. This result suggests that by applying the elastic-plastic parameter KJ, the SCC crack growth rates in a wider range could be estimated easily with using a smaller specimen.

Effect of Constraint Induced by Specimen Geometries on Crack Growth Behavior Under Creep-Fatigue Interaction

2018 ◽  
Author(s):  
Lei Zhao ◽  
Lianyong Xu
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Tip ◽  
Crack Growth Behavior ◽  
Growth Behaviour ◽  
Crack Growth Behaviour ◽  
Creep Fatigue ◽  
Crack Growth Rates

Creep-fatigue interaction would accelerate the crack growth behaviour and change the crack growth mode, which is different from that presenting in pure creep or fatigue regimes. In addition, the constraint ahead of crack tip affects the relationship between crack growth rate and fracture mechanics and thus affects the accuracy of the life prediction for high-temperature components containing defects. In this study, to reveal the role of constraint caused by various specimen geometries in the creep-fatigue regime, five different types of cracked specimens (including C-ring in tension CST, compact tension CT, single notch tension SENT, single notch bend SENB, middle tension MT) were employed. The crack growth and damage evolution behaviours were simulated using finite element method based on a non-linear creep-fatigue interaction damage model considering creep damage, fatigue damage and interaction damage. The expression of (Ct)avg for different specimen geometries were given. Then, the variation of crack growth behaviour with various specimen geometries under creep-fatigue conditions were analysed. CT and CST showed the highest crack growth rates, which were ten times as the lowest crack growth rates in MT. This revealed that distinctions in specimen geometry influenced the in-plane constraint level ahead of crack tip. Furthermore, a load-independent constraint parameter Q* was introduced to correlate the crack growth rate. The sequence of crack growth rate at a given value of (Ct)avg was same to the reduction of Q*, which shown a linear relation in log-log curve.

Fatigue Crack Growth Behavior of Titanium Alloy Ti-6Al-4V and Weldment

2001 ◽  
Vol 123 (3) ◽  
pp. 141-146 ◽  
Author(s):  
Mamdouh M. Salama
Keyword(s):  
Growth Rate ◽  
Titanium Alloy ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Titanium Alloys ◽  
Crack Growth ◽  
Growth Rates ◽  
Offshore Structures ◽  
Crack Growth Rates

Optimization of weight, cost, and performance of deepwater offshore structures demands the increased utilization of high strength, light weight, and corrosion resistant materials such as titanium alloys. Titanium alloy Ti-6Al-4V has been considered for several critical components such as risers and taper joints. Because of the novelty of use of titanium alloys in the offshore industry, there is currently no standard governing design of titanium components for offshore structures. Since these structural components are subjected to a complex spectrum of environmental loading, assessment of defect tolerance using fatigue crack growth analysis is generally considered an important design parameter. In this paper, more than 60 crack growth data sets from 20 independent laboratories were collected and analyzed to develop crack growth rate equations for use in defect assessment. These data include the results of fatigue testing of both base material and welded joints in air and seawater with and without cathodic protection and at different R-ratios and test frequencies. The results suggest that for crack growth rates above 10−7 in./cycle, crack growth of Ti-6Al-4V appears to be independent of testing condition and materials processing. At the low crack growth rate (below 10−7 in./cycle), the review revealed that data are very limited. These limited data, however, suggest that the crack growth threshold is dependent on the R-ratio and slightly dependent on material processing. Comparison between crack growth rates of steel and titanium alloy (Ti-6Al-4V) showed that the two materials have very similar behavior.

Fatigue Crack Growth in Type 316 Stainless Steel at High Temperature

1971 ◽  
Vol 93 (4) ◽  
pp. 976-980 ◽  
Author(s):  
P. Shahinian ◽  
H. H. Smith ◽  
H. E. Watson
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
316 Stainless Steel ◽  
Arrhenius Relation ◽  
Crack Growth Rates

The dependence of fatigue crack growth rates on range of stress intensity factor (ΔK) in Type 316 stainless steel was investigated over the temperature range of 75 to 1100 deg F. The data for the most part could be described by a power law relationship. An increase in temperature generally increased crack growth rate for a given ΔK and decreased fatigue life. The dependence of crack growth rate on temperature is not described adequately by an Arrhenius relation over the range investigated. On the other hand, by normalizing ΔK with respect to Young’s modulus, E, the crack growth rates for the various temperatures tend to fall within a single band.

Small Scale Sour Fatigue Testing With Dense Phase Gases

2012 ◽  
Author(s):  
Weiwei Yu ◽  
Pedro M. Vargas ◽  
Ben Crowder ◽  
Sam Mishael ◽  
Ramgopal Thodla
Keyword(s):  
Growth Rate ◽  
High Pressure ◽  
Water Content ◽  
Crack Growth ◽  
Growth Rates ◽  
Fatigue Performance ◽  
Small Scale ◽  
Dense Phase ◽  
High Crack ◽  
Crack Growth Rates

One way generally accepted by industry to evaluate the effect of sour environment on fatigue performance of girth welds is by small scale testing in sour brines. These tests are commonly done at room temperature and pressure and therefore can only contain a maximum of 14.7psia of H2S in a gaseous phase. In comparison, very little has been published about fatigue performance in sour environments where negligible amounts or no water is present. Such condition can be found for pipelines serving in a “dry” sour environment (H2S and other gases in dense phase) with high H2S concentration. This paper documents both small scale fatigue crack growth rate (FCGR) tests and S-N fatigue tests in a dense phase sour environment with ultra-low water content and high H2S concentration under high pressure. Fatigue life reduction factors were calculated from FCGR approach (with the name crack growth acceleration factor, CGAF) and S-N approach (with the name knockdown factor), respectively. Industry understanding today is that water is necessary for accelerating fatigue crack growth. Quite opposite to the expected effect of water content on crack growth, even ultra-low water content (<450ppm) resulted in high crack growth rates. Crack growth rates were comparable among tests with various water contents, all ultra low. Through limited testing, no temperature dependency on crack growth rate was identified. It is postulated that hydrogen dissociation due to high pressure and high concentration may be the cause for high crack growth rates on the absence of water. Small scale S-N tests on smooth specimens reveal that fatigue performance in ultra-low-water sour environments is the same as in air. We find that the dry gas environment dose not attack the metal surface preserving the fatigue performance.

Experimental Study on Fatigue Crack Growth and Residual Strength of Steel 30CrMnSiNi2A under Mixed Corrosive Environments

2008 ◽  
Vol 33-37 ◽  
pp. 261-266
Author(s):  
Sheng Nan Wang ◽  
Yi Li ◽  
Jian Bo Qin ◽  
Ya Long Liu ◽  
Yue Quan Zhou
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Residual Strength ◽  
Growth Rates ◽  
Critical Crack Length ◽  
Corrosive Environments ◽  
Crack Growth Rates

The effects of five single and three mixed corrosive environments on the fatigue crack growth and residual strength of steel 30CrMnSiNi2A were experimentally studied. The crack growth rates in corrosive environments, obtained by using Paris equation, were compared with crack growth rate in lab air. The results showed that the interactions of aggressive environments with fatigue loads caused the accelerations of fatigue crack growth rates in steel 30CrMnSiNi2A. But the effects of various environments on the fatigue crack growth rate are different. Among the environments the most detrimental one was oil-box zone, followed by cookroom&washroom, tank seeper, 3.5%NaCl, moist air, high altitude and dried air. Also, the test data showed the less effect of various corrosive environments on critical crack length, that is, no direct infection of corrosive environments on residual strength capability dominated by fracture toughness.

scholarly journals Orientation Dependence of Hydrogen Accelerated Fatigue Crack Growth Rates in Pipeline Steels

2018 ◽  
Author(s):  
Eun Ju Song ◽  
Joseph A. Ronevich
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Growth Rates ◽  
Orientation Dependence ◽  
Gaseous Hydrogen ◽  
Crack Growth Rates

One of the most efficient methods for supplying gaseous hydrogen long distances is by using steel pipelines. However, steel pipelines exhibit accelerated fatigue crack growth rates in gaseous hydrogen relative to air. Despite conventional expectations that higher strength steels would be more susceptible to hydrogen embrittlement, recent testing on a variety of pipeline steel grades has shown a notable independence between strength and hydrogen assisted fatigue crack growth rate. It is thought that microstructure may play a more defining role than strength in determining the hydrogen susceptibility. Among the many factors that could affect hydrogen accelerated fatigue crack growth rates, this study was conducted with an emphasis on orientation dependence. The orientation dependence of toughness in hot rolled steels is a well-researched area; however, few studies have been conducted to reveal the relationship between fatigue crack growth rate in hydrogen and orientation. In this work, fatigue crack growth rates were measured in hydrogen for high strength steel pipeline with different orientations. A significant reduction in fatigue crack growth rates were measured when cracks propagated perpendicular to the rolling direction. A detailed microstructural investigation was performed, in an effort to understand the orientation dependence of fatigue crack growth rate performance of pipeline steels in hydrogen environments.

The Correlation of Fatigue Crack Growth Rates in Rubber Subjected to Multiaxial Loading Using Continuum Mechanical Parameters

2007 ◽  
Vol 80 (1) ◽  
pp. 169-182 ◽  
Author(s):  
W. V. Mars ◽  
A. Fatemi
Keyword(s):  
Energy Density ◽  
Crack Growth ◽  
Growth Rates ◽  
Test Piece ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Driving Forces ◽  
Mechanical Parameters ◽  
Small Cracks ◽  
Crack Growth Rates

Abstract Although both the crack nucleation and growth stages of the fatigue failure process in rubber are manifestations of the same characteristic material behavior, the nucleation stage deserves special attention. In this case, continuum mechanical parameters may be used to characterize the driving forces of small cracks, without reference to the geometry of the test piece. The ability to estimate crack driving forces from continuum mechanical parameters during the growth process of small cracks has been investigated by correlating three different parameters (maximum principal strain, strain energy density, and cracking energy density) to rates of crack growth observed photographically during fatigue tests on initially uncracked specimens. Significant scatter in crack growth rates was observed resulting from high crack density and crack interactions. These results are also compared to crack growth measurements made on a pure shear (planar tension) test piece. The difference between continuum parameters that refer to a specific material plane, and those that do not is emphasized. Generally, the maximum principal strain and cracking energy density parameters provided similar levels of correlation. The strain energy density parameter consistently gave the poorest correlation. An advantage of the cracking energy density is that it considers the experiences of specific planes embedded in the material (i.e. it is a plane-specific parameter).

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