Mechanical Fatigue of Rubber

1972 ◽  
Vol 45 (1) ◽  
pp. 309-328 ◽  
Author(s):  
G. J. Lake
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Complex Shape ◽  
Atmospheric Oxygen ◽  
Fatigue Behavior ◽  
Repeated Loading ◽  
Mechanical Fatigue ◽  
Available Energy ◽  
Mechanical Deformations ◽  
Mechanical Crack

Abstract Fatigue failure of rubber under repeated loading is reviewed. The process considered is that occurring in the absence of appreciable temperature rise as a result of the development of one or more cracks. A fracture mechanics approach, based on the elastic energy available for crack propagation, enables the crack growth and fatigue behavior to be interrelated quantitatively and is helpful from both basic and applied viewpoints. Initiation of mechanical crack growth is governed by a critical value of the available energy, which is of similar magnitude for various elastomers and can be related approximately to the primary bond strength and molecular structure. Once this value is exceeded, the characteristics of growth vary markedly for different elastomers and appear to be influenced primarily by the elastic hysteresis of the rubber at high strains. Although the mechanical deformations are the basic driving force, the crack growth and fatigue behavior can also be strongly affected by atmospheric oxygen and ozone and the mechanisms of action of these gases are described. Implications of the work from the testing and service viewpoints are considered. A major problem in applying the fracture mechanics approach is to determine the energy available for crack growth in a component of complex shape. Recently-developed methods of doing this are discussed and the quantitative application of the approach to predict service performance is illustrated.

Fatigue Behavior and Damage Assessment of Stainless Steel/Aluminum Composites

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Volkan Eskizeybek ◽  
Ahmet Avci ◽  
Ahmet Akdemir ◽  
Ömer Sinan Şahin
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Fatigue Behavior ◽  
Laminated Composite ◽  
Strain Energy Release ◽  
Fatigue Loading ◽  
304 Stainless Steel

Fatigue crack growth and related damage mechanisms were investigated experimentally in a stainless steel/aluminum laminated composite with middle through thickness crack, and two different fracture mechanics approaches applied to the composite to reveal their differences under fatigue loading. The laminated composite material, which has a unidirectional continuous AISI 304 stainless steel as fibers and Al 1060 as matrix, was produced by using diffusion bonding. Fatigue tests were conducted in accordance with ASTM E 647. The relationships between fatigue crack growth rate (da/dN), stress intensity factor (ΔK), and strain energy release rate (ΔG) were determined; and damage behavior was discussed. Both linear elastic fracture mechanics (LEFM) and compliance method were used, and the results were compared with each other. It is found that as the crack propagates, the LEFM overestimates the ΔG values. Interlaminar and fiber/matrix interface damage were evaluated by fractographic examination.

A Thermo-Mechanical Fatigue Crack Growth Accumulative Model for Gas Turbine Blades and Vanes

2016 ◽  
Author(s):  
Andrea Riva ◽  
Alessio Costa ◽  
Dalila Dimaggio ◽  
Paolo Villari ◽  
Karl Michael Kraemer ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Propagation ◽  
Gas Turbine ◽  
Crack Growth ◽  
Turbine Blades ◽  
Gas Turbine Blades ◽  
Mechanical Fatigue ◽  
Safety Margins

Heavy duty gas turbine blades and vanes are operated at high temperatures and high stresses, condition where several damage mechanisms can simultaneously be present. For example creep, fatigue and oxidation play an important role in the propagation of existing cracks. Crack growth models are employed for assessment criteria, interpretation of the field feedback and non-conformities management and they are required to be as accurate as possible when predicting crack propagation under the combined effect of all the three phenomena. In this work, a Linear Elastic Fracture Mechanics (LEFM) model based on isothermal experimental tests and validated by Thermo-Mechanical-Fatigue Crack Growth tests (TMFCG), is employed to predict crack propagation of a cast Ni-base superalloy used in gas turbine blades and vanes. When calculating the individual propagation fractions of creep and fatigue crack growth, the model accounts for the instantaneous stress state and temperature in transient regime (i.e. a complete cycle of start-up, base-load and shut-down). The loss of γ’- precipitates at the crack tip due to surface oxidation is interpreted as environmental damage fraction. A complete workflow for the systematic use of the approach, comprising an in-house software, has been defined and developed. Stress intensity factors used for LEFM calculations are determined either using tabulated weight functions or with the aid of Finite Element Analysis (FEA). This flexible approach is consistent with the industrial need of a given fracture mechanics calculation, which might require different levels of accuracy and resources/time consumption case by case. The software identifies the fraction of propagation caused by oxidation, creep crack growth or fatigue crack growth. This allows checking the physical realism of the results by comparing to metallographic analysis of fracture surfaces from broken TMFCG test specimen and/or real component damage information from field. Besides, this feature can be helpful to support the engineer in residual life evaluation under damage tolerant approach because it allows the identification of the type of operational regime that minimizes crack propagation. The software also allows the execution of sensitivity analyses via Monte-Carlo calculations, identifying for a given component and operational condition the more relevant calculation inputs. This feature also quantitatively supports the engineers in the identification of the most appropriate safety margins.

scholarly journals Effect of Bond-Line Thickness on Fatigue Crack Growth of Structural Acrylic Adhesive Joints

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1723
Author(s):  
Yu Sekiguchi ◽  
Chiaki Sato
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Behavior ◽  
Adhesive Bond ◽  
Bond Line ◽  
Loading Conditions ◽  
Fatigue Crack Growth Resistance ◽  
Line Thickness ◽  
Bond Line Thickness

With an increasing demand for adhesives, the durability of joints has become highly important. The fatigue resistance of adhesives has been investigated mainly for epoxies, but in recent years many other resins have been adopted for structural adhesives. Therefore, understanding the fatigue characteristics of these resins is also important. In this study, the cyclic fatigue behavior of a two-part acrylic-based adhesive used for structural bonding was investigated using a fracture-mechanics approach. Fatigue tests for mode I loading were conducted under displacement control using double cantilever beam specimens with varying bond-line thicknesses. When the fatigue crack growth rate per cycle, da/dN, reached 10−5 mm/cycle, the fatigue toughness reduced to 1/10 of the critical fracture energy. In addition, significant changes in the characteristics of fatigue crack growth were observed varying the bond-line thickness and loading conditions. However, the predominance of the adhesive thickness on the fatigue crack growth resistance was confirmed regardless of the initial loading conditions. The thicker the adhesive bond line, the greater the fatigue toughness.

Fracture mechanics in design and service: ‘living with defects’ - Application of fracture mechanics to rubber articles, including tyres

1981 ◽  
Vol 299 (1446) ◽  
pp. 189-202 ◽  
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Strain Energy ◽  
Tensile Failure ◽  
Practical Application ◽  
Complicated Fracture ◽  
Fracture Work

The use of a fracture mechanics approach, based on the rate of release of strain energy, to account for various features of the failure of vulcanized rubbers is outlined. The properties considered include those to which fracture mechanics is often applied — tear, tensile failure, crack growth and fatigue — and others to which its application is less usual — abrasion, ozone attack and cutting by sharp objects. The relation of macroscopically observed properties to the basic molecular strength of the material is also discussed. An example of a quantitative practical application of the rubber fracture work, to groove cracking in tyres, is then considered. Finally, the rather more complicated fracture that can occur in rubber—cord laminates is discussed and it is shown that the energetics approach can be applied to some features, at least, of this.

Effective Modeling of Fatigue Crack Growth in Pipelines

2012 ◽  
Author(s):  
Steven J. Polasik ◽  
Carl E. Jaske
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Models ◽  
Critical Parameters ◽  
Operating Pressure ◽  
Mechanics Model ◽  
Key Variables

Pipeline operators must rely on fatigue crack growth models to evaluate the effects of operating pressure acting on flaws within the longitudinal seam to set re-assessment intervals. In most cases, many of the critical parameters in these models are unknown and must be assumed. As such, estimated remaining lives can be overly conservative, potentially leading to unrealistic and short reassessment intervals. This paper describes the fatigue crack growth methodology utilized by Det Norske Veritas (USA), Inc. (DNV), which is based on established fracture mechanics principles. DNV uses the fracture mechanics model in CorLAS™ to calculate stress intensity factors using the elastic portion of the J-integral for either an elliptically or rectangularly shaped surface crack profile. Various correction factors are used to account for key variables, such as strain hardening rate and bulging. The validity of the stress intensity factor calculations utilized and the effect of modifying some key parameters are discussed and demonstrated against available data from the published literature.

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