Factors Influencing the Strength of Rubbers

1975 ◽  
Vol 48 (5) ◽  
pp. 902-912 ◽  
Author(s):  
A. G. Thomas
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Characteristic ◽  
Tensile Failure ◽  
Razor Blade ◽  
New Approach ◽  
Surface Configuration ◽  
Strength Behavior ◽  
Base Of The Tongue ◽  
Good Agreement

Abstract The strength behavior of rubbers is discussed in terms of fracture mechanics which treats fatigue and tensile failure as crack growth processes from small flaws. Crack growth can be influenced by the presence of oxygen or ozone. The nature of the vulcanizing system affects strength : crosslinks probably rupture and reform under stress. A new approach to the problem of abrasion is presented using fracture mechanics. Schallamach has shown that rubber often develops a pattern of ridges perpendicular to the direction of abrasion. In the simplest case abrasion is produced by a line contact (e.g., a razor blade) which pulls a tongue of rubber from the ridge producing crack growth at the base of the tongue. Provided the surface configuration is in a steady state, the quantity of rubber abraded can be related quantitatively to the frictional force and the crack growth characteristic of the rubber on some reasonable assumptions. Good agreement with experiment is found for noncrystallizing rubbers but the behavior of strain crystallizing natural rubber suggests that crystallization cannot occur under the conditions used so that the rubber is not strengthened by this means.

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.

scholarly journals A NEW APPROACH TO DYNAMIC FINITE-SIZE SCALING

2003 ◽  
Vol 14 (07) ◽  
pp. 945-954 ◽  
Author(s):  
MEHMET DİLAVER ◽  
SEMRA GÜNDÜÇ ◽  
MERAL AYDIN ◽  
YİĞİT GÜNDÜÇ
Keyword(s):  
Three Dimensional ◽  
Finite Size ◽  
Taylor Series Expansion ◽  
Scaling Behavior ◽  
Dynamic Scaling ◽  
Finite Size Scaling ◽  
New Approach ◽  
Size Scaling ◽  
Dynamic Exponent ◽  
Good Agreement

In this work we have considered the Taylor series expansion of the dynamic scaling relation of the magnetization with respect to small initial magnetization values in order to study the dynamic scaling behavior of two- and three-dimensional Ising models. We have used the literature values of the critical exponents and of the new dynamic exponent x0 to observe the dynamic finite-size scaling behavior of the time evolution of the magnetization during early stages of the Monte Carlo simulation. For the three-dimensional Ising model we have also presented that this method opens the possibility of calculating z and x0 separately. Our results show good agreement with the literature values. Measurements done on lattices with different sizes seem to give very good scaling.

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.

Back calculation of parent austenite orientation using a clustering approach

2013 ◽  
Vol 46 (1) ◽  
pp. 210-215 ◽  
Author(s):  
V. Tari ◽  
A. D. Rollett ◽  
H. Beladi
Keyword(s):  
Face Centered Cubic ◽  
Orientation Relationships ◽  
New Approach ◽  
Austenite Grain ◽  
Parent Orientation ◽  
Back Calculation ◽  
Clustering Approach ◽  
Face Centered ◽  
Parent Austenite ◽  
Good Agreement

A new approach is presented for calculating the parent orientation from sets of variants of orientations produced by phase transformation. The parent austenite orientation is determined using the orientations of bainite variants that transformed from a single parent austenite grain. In this approach, the five known orientation relationships are used to back transform each observed bainite variant to all their potential face-centered-cubic (f.c.c.) parent orientations. A set of potential f.c.c. orientations has one representative from each bainite variant, and each set is assembled on the basis of minimum mutual misorientation. The set of back-transformed orientations with the minimum summation of mutual misorientation angle (SMMA) is selected as the most probable parent (austenite) orientation. The availability of multiple sets permits a confidence index to be calculated from the best and next best fits to a parent orientation. The results show good agreement between the measured parent austenite orientation and the calculated parent orientation having minimum SMMA.

On the Influence of a Heat Treat for an Aluminizing Progress Based on Al Microparticles Slurry for Model Ni and Ni20Cr. Experimental and Theoretical Approaches.

2012 ◽  
Vol 323-325 ◽  
pp. 373-379 ◽  
Author(s):  
B. Rannou ◽  
M. Mollard ◽  
B. Bouchaud ◽  
J. Balmain ◽  
G. Bonnet ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Substrate Surface ◽  
Single Step ◽  
Alloying Element ◽  
Aluminum Particles ◽  
New Approach ◽  
Theoretical Approaches ◽  
Barrier Coating ◽  
Coating Characteristics ◽  
Good Agreement

The use of thermal barrier coating systems allows superalloys to withstand higher operating temperatures in aeroengine turbines. Aiming at providing oxidation protection to such substrates, an aluminum-rich layer is deposited to form the α-Al2O3scale over which a ceramic layer (i.e. YSZ layer) is applied to provide thermal insulation. A new approach is now being investigated within the FP7 European project « PARTICOAT », in which a single step process is employed by applying micro-sized aluminum particles. The particles are mixed in a binder and deposited by brushing or spraying on the substrate surface. During a heat treatment, the particles sinter and oxidize to form a top coat composed of hollow con-joint alumina spheres and simultaneously, an Al-rich diffusion zone is formed in the substrate. For a better understanding of the diffusion / growth processes, preliminary tests were carried out on pure nickel and Ni20Cr model alloys prior to further application on commercial superalloys. The effect of the heat treatment on the coating characteristics (number of layers, thickness, composition, homogeneity, etc.) was particularly investigated to emphasize the mechanisms of diffusion governing the growth of the coatings. The establishment of the diffused layers occurred very readily even at intermediate temperatures (650 and 700°C). However, the layers formed did not match perfectly with the thermodynamic modeling because of the quick incorporation of Ni into molten Al at intermediate temperatures (650°C). In contrast, at higher temperatures (700 and 1100°C) the phases predicted by Thermocalc are in good agreement with the observed thickness of the diffused layers. The incorporation of Cr as an alloying element restrained Al ingress by segregation of Cr even at very low temperatures aluminizing temperatures (625°C).

A new look at filter backwash hydraulics

2001 ◽  
Vol 1 (2) ◽  
pp. 65-72 ◽  
Author(s):  
Ömer Akgiray ◽  
Ahmet M. Saatçı
Keyword(s):  
Experimental Measurements ◽  
New Approach ◽  
Ergun Equation ◽  
Mathematical Formulas ◽  
Good Agreement ◽  
New Look

A new approach to model media expansion during filter backwash is presented. The proposed approach is based on the assumption that the Ergun equation remains valid after fluidization. Mathematical formulas are derived for predicting expanded porosity for a given backwash velocity or backwash velocity for a given expanded porosity. These formulas can be easily used by the engineer. Values predicted using the proposed approach are in good agreement with experimental measurements.

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