Dissipated energy density as fatigue criterion for non-relaxing tensional loadings of non-crystallizing elastomers?

2019 ◽  
Vol 78 ◽  
pp. 105953 ◽  
Author(s):  
Oliver Gehrmann ◽  
Nils Hendrik Kröger ◽  
Maria Krause ◽  
Daniel Juhre
Keyword(s):  
Energy Density ◽  
Dissipated Energy ◽  
Fatigue Criterion

COMPARISON OF FATIGUE CRITERIA UNDER PROPORTIONAL AND NON-PROPORTIONAL MULTIAXIAL LOADING

2018 ◽  
Vol 91 (2) ◽  
pp. 320-338 ◽  
Author(s):  
J. L. Poisson ◽  
S. Méo ◽  
F. Lacroix ◽  
G. Berton ◽  
M. Hosséini ◽  
...  
Keyword(s):  
Energy Density ◽  
Strain Energy ◽  
Large Range ◽  
Viscoelastic Model ◽  
Multiaxial Fatigue ◽  
Dissipated Energy ◽  
Multiaxial Loading ◽  
Rubberlike Material ◽  
Phase Angles ◽  
Fatigue Criterion

ABSTRACTOwing to their interesting mechanical behavior and their diversity, rubberlike materials are more and more used in the industry. Previous works (Poisson et al.) presented an important experimental investigation on the multiaxial fatigue of polychloroprene rubber, with both proportional and non-proportional combinations of tension and torsion loads (with a large range of loads and three different phase angles: 0°; 90°, 180°). A fatigue criterion, based on the dissipated energy density (DED) was introduced. Comparing this parameter to the most important criteria available on literature—which are the strain energy density (SED), the cracking energy density (CED), and the Eshelby tensor—in their accuracy allows one to predict fatigue life of rubberlike material. All the predictors are computed with an analytical viscoelastic model based on the kinematics of a combined tension and torsion loading applied on a cylinder. This cylinder represents the central part of the axisymetric dumbbell specimen, and the model was identified with a polychloroprene rubber. It is finally shown that the DED and CED reach more conclusive results, provided the structure, the material, and the loads investigated.

Modeling of torsion fatigue in shape memory alloys

2019 ◽  
Vol 30 (20) ◽  
pp. 3146-3162 ◽  
Author(s):  
Mohammad Reza Mohammadzadeh ◽  
Mahmoud Kadkhodaei ◽  
Mahmoud Barati ◽  
Shabnam Arbab Chirani ◽  
Luc Saint-Sulpice
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Current Knowledge ◽  
Low Cycle Fatigue ◽  
Dissipated Energy ◽  
Loading Frequency ◽  
Thermomechanical Model ◽  
Number Of Cycles ◽  
Fatigue Criterion

Fatigue in shape memory alloys is one of the crucial aspects of their behavior; however, the current knowledge is mainly focused on uniaxial fatigue and is inadequate for engineering purposes. In this article, a fatigue criterion based on the stabilized dissipated energy has been presented to investigate the torsional low-cycle fatigue of superelastic shape memory alloys. To this aim, a one-dimensional torsional constitutive model in addition to a modified fully coupled thermomechanical model has been utilized so that the torsional cyclic responses especially in relatively high loading frequencies, which contribute to remarkable temperature variations and consequent response changes, could be taken into account. The calculated stabilized dissipated energy, then, has been used in an energy approach fatigue criterion in order to predict the fatigue life; hence, an explicit relation, which is capable of determining the number of cycles to failure for different loading conditions at a given loading frequency, has been obtained. The numerical results have been appraised for NiTi specimens, and they have been shown to be in a good agreement with the experimental data. Finally, using the proposed approach, the effect of fatigue test parameters on the fatigue life has been studied.

scholarly journals Explicit Q expressions for inhomogeneous P- and SV-waves in isotropic viscoelastic media

2019 ◽  
Vol 17 (2) ◽  
pp. 300-312 ◽  
Author(s):  
Xu Liu ◽  
Stewart Greenhalgh ◽  
Bing Zhou ◽  
Huijian Li
Keyword(s):  
Energy Density ◽  
Dissipation Factor ◽  
Energy Balance Equation ◽  
Dissipated Energy ◽  
P Waves ◽  
S Waves ◽  
Viscoelastic Media ◽  
Inhomogeneous Waves ◽  
Inhomogeneity Parameter ◽  
P And Sv Waves

Abstract We derive explicit expressions for the dissipation factors of inhomogeneous P and SV-waves in isotropic viscoelastic media. The Q−1 values are given as concise and simple functions of material parameters and the wave inhomogeneity parameter using two different definitions. Unlike homogenous waves, inhomogeneous waves may have significant differences in the values of dissipation factors because of different definitions. For example, under one of the three dissipation factor definitions that Q−1 is equal to the time-averaged dissipated-energy density divided by twice the time-averaged strain-energy density, it is found and proved that the dissipation factor of SV-waves is totally independent of the inhomogeneity parameter. For materials in which P-waves are normally more dissipative than S-waves (e.g. a porous reservoir), the dissipation factors of P-waves tend to decrease with increasing degree of inhomogeneity. Based on Buchan's classic real value energy balance equation, a parallel investigation is conducted for each step similar to that based on the Carcione equations, including derivation of explicit formulas (with inhomogeneity angle representing the degree of inhomogeneity of a plane wave), and dissipation curves calculations. We also obtain an inhomogeneity independent formula of $Q_{\, SV}^{ - 1}$, and exactly the same phase velocity and attenuation dispersion results for the example material.

MULTIAXIAL FATIGUE CRITERIA APPLIED TO A POLYCHLOROPRENE RUBBER

2012 ◽  
Vol 85 (1) ◽  
pp. 80-91 ◽  
Author(s):  
J. L. Poisson ◽  
S. Méo ◽  
F. Lacroix ◽  
G. Berton ◽  
N. Ranganathan
Keyword(s):  
Large Strain ◽  
Fatigue Behavior ◽  
Viscoelastic Model ◽  
Type Specimen ◽  
Multiaxial Fatigue ◽  
Dissipated Energy ◽  
Rubber Part ◽  
Phase Angles ◽  
Fatigue Criterion ◽  
Important Objective

Abstract Due to their interesting mechanical behavior and their diversity, rubber materials are more and more used in industry. Indeed, formulating a multiaxial fatigue criterion to predict fatigue lives of rubber components constitutes an important objective to conceive rubber products. An experimental campaign is developed here to study the multiaxial fatigue behavior of polychloroprene rubber. To reproduce multiaxial solicitations, combined tension–torsion tests were carried out on a dumbbell-type specimen (an axisymmetric rubber part bonded to metal parts with a reduced section at mid-height), with several values of phase angles between tension and torsion. A constitutive model is needed to calculate multiaxial fatigue criteria, and then analyze fatigue results. A large strain viscoelastic model, based on the tension–torsion kinematics, is then used to determine the material's stress–strain law. Dissipated energy density is introduced as a multiaxial fatigue criterion, and compared with those usually used in the literature. A multiaxial Haigh diagram is then built to observe the influence of Rd-ratio (ratio of the axial displacement's minimum to the axial displacement's maximum) on the multiaxial fatigue lives of polychloroprene rubber.

On Energy Strength Theories for Geomaterials

2013 ◽  
Vol 353-356 ◽  
pp. 901-904
Author(s):  
Shou Yi Xue
Keyword(s):  
Energy Density ◽  
Shear Strain ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Volumetric Strain ◽  
Dissipated Energy ◽  
Energy Theory ◽  
Shear Strain Energy ◽  
Shear Energy ◽  
Strain Energy Density Theory

The composition of the energy in the process of material deformation and failure and the relationship between energy and strength were summarized; the features, essences and main problems of the energy release rate theory, the three-shear energy theory and the net shear strain energy density theory were illustrated. It is pointed out that the roles of distortion strain energy, volumetric strain energy and dissipated energy are not identical, especially distortion strain energy and volumetric strain energy must be separately processed. The three-shear energy theory and the net shear strain energy density theory can properly deal with the problems, and also well reflect the intermediate principal stress effect. The above research results can provide references for further discussions.

scholarly journals Effect of Bedding Structure on the Energy Dissipation Characteristics of Dynamic Tensile Fracture for Water-Saturated Coal

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Shuang Gong ◽  
Lei Zhou ◽  
Zhen Wang ◽  
Wen Wang
Keyword(s):  
Particle Size ◽  
Energy Dissipation ◽  
Energy Density ◽  
Impact Velocity ◽  
Split Hopkinson Pressure Bar ◽  
Dissipated Energy ◽  
Tensile Fracture ◽  
Bedding Angle ◽  
Splitting Test ◽  
Water Saturated

The analysis of energy dissipation characteristics is a basic way to elucidate the mechanism of coal rock fragmentation. In order to study the energy dissipation patterns during dynamic tensile deformation damage of coal samples, the Brazilian disc (BD) splitting test under impact conditions was conducted on burst-prone coal samples using a split Hopkinson pressure bar (SHPB) loading system. The effects of impact velocity, bedding angle, and water saturated on the total absorbed energy density, total dissipated energy density, and damage variables of coal samples were investigated. In addition, the coal samples were collected after crushing to produce debris with particle sizes of 0-0.2 mm and 0.2-5 mm, and the distribution characteristics of different size debris were compared and analyzed. The results show that the damage variables of natural dry coal samples increase approximately linearly with the increase of impact velocity; however, the overall damage variables of saturated coal samples increase exponentially as a function of impact velocity. Compared with air-dry samples, the number of fragments with the particle size of 0-0.2 mm of saturated samples decreases by 14.1%-31.3%, and the number of fragments with the particle size of 0.2-5 mm decreases by 33.7%-53.0%. However, when the bedding angle is 45°, the percentage of fragment mass of saturated samples is larger than that of air-dry samples. The conclusions provide a theoretical basis for understanding the deterioration mechanism of coal after water saturation and the implementation of water injection dust prevention technology in coal mines.

Prediction of the Coating Durability Under Oscillating Sliding Contact: Introduction of a Local Energy Density Parameter

2005 ◽  
Author(s):  
S. Fouvry ◽  
V. Fridrici ◽  
T. Liskiewicz
Keyword(s):  
Energy Density ◽  
Industrial Applications ◽  
Sliding Contact ◽  
Hard Coatings ◽  
Dissipated Energy ◽  
Wear Volume ◽  
Density Parameter ◽  
Local Energy ◽  
Coating Durability ◽  
Local Energy Density

The knowledge of wear kinetics of thin soft lubricant or hard coatings under alternated sliding contact is of great interest for many industrial applications. Because the coating endurance is related to the substrate reaching condition, it has been shown that classical wear volume descriptions are not appropriated. A local damage description, based on a local friction dissipated energy density variable is then introduced. It consists to compare the coating endurance (i.e. number of sliding cycles) versus the maximum local energy density dissipated through the interface per sliding cycle. A “life time vs maximum dissipated energy density master curve” is obtained and rationalized through a parabolic evolution. The coating endurance is modelized through a simple ratio between an energy capacity variable, representative of the durability of the studied coating. Applied to hard coatings (TiN) the stability of this approach has been confirmed for solid lubricant coatings.

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