A new non-local criterion in high-cycle multiaxial fatigue for non-proportional loadings

2007 ◽  
Vol 29 (8) ◽  
pp. 1465-1474 ◽  
Author(s):  
A CHAMAT ◽  
M ABBADI ◽  
J GILGERT ◽  
F COCHETEUX ◽  
Z AZARI
Keyword(s):  
Multiaxial Fatigue ◽  
Local Criterion ◽  
Non Local

A Non Local Multiaxial Fatigue Approach to Account for Stress Gradient Effect Applied to Crack Initiation in Fretting

2010 ◽  
Vol 7 (3) ◽  
pp. 102526 ◽  
Author(s):  
R. Amargier ◽  
S. Fouvry ◽  
C. Poupon ◽  
L. Chambon ◽  
S. Kalluri ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Stress Gradient ◽  
Multiaxial Fatigue ◽  
Gradient Effect ◽  
Non Local

scholarly journals Micromechanical Modelling of the Influence of Strain Ratio on Fatigue Crack Initiation in a Martensitic Steel-A Comparison of Different Fatigue Indicator Parameters

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2852 ◽  
Author(s):  
Benjamin Josef Schäfer ◽  
Petra Sonnweber-Ribic ◽  
Hamad ul Hassan ◽  
Alexander Hartmaier
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Damage Zone ◽  
Fatigue Crack Initiation ◽  
High Strength ◽  
Strain Ratio ◽  
Multiaxial Fatigue ◽  
Total Strain ◽  
Non Local ◽  
Crack Initiation Life

Micromechanical fatigue lifetime predictions, in particular for the high cycle fatigue regime, require an appropriate modelling of mean stress effects in order to account for lifetime reducing positive mean stresses. Focus of this micromechanical study is the comparison of three selected fatigue indicator parameters (FIPs), with respect to their applicability to different total strain ratios. In this work, investigations are performed on the modelling and prediction of the fatigue crack initiation life of the martensitic high-strength steel SAE 4150 for two different total strain ratios. First, multiple martensitic statistical volume elements (SVEs) are generated by multiscale Voronoi tessellations. Micromechanical fatigue simulations are then performed on these SVEs by means of a crystal plasticity model to obtain microstructure dependent fatigue responses. In order to account for the material specific fatigue damage zone, a non-local homogenisation scheme for the FIPs is introduced for lath martensitic microstructures. The numerical results of the different non-local FIPs are compared with experimental fatigue crack initiation results for two different total strain ratios. It is concluded that the multiaxial fatigue criteria proposed by Fatemi-Socie is superior for predicting fatigue crack initiation life to the energy dissipation criteria and the accumulated plastic slip criteria for the investigated total strain ratios.

Runaway of electrons in dense gases and mechanism of generation of high-power subnanosecond beams

Open Physics ◽  
2004 ◽  
Vol 2 (4) ◽  
Author(s):  
Alexey Tkachev ◽  
Sergei Yakovlenko
Keyword(s):  
Electric Fields ◽  
Critical Voltage ◽  
Runaway Electrons ◽  
Local Criterion ◽  
Fast Electrons ◽  
Electron Multiplication ◽  
Dense Gases ◽  
Non Local ◽  
Discharge Gap

AbstractNew understanding of mechanism of the runaway electrons beam generation in gases is presented. It is shown that the Townsend mechanism of the avalanche electron multiplication is valid even for the strong electric fields when the electron ionization friction on gas may be neglected. A non-local criterion for a runaway electron generation is proposed. This criterion results in the universal two-valued dependence of critical voltage U cr on pd for a certain gas (p is a pressure, d is an interelectrode distance). This dependence subdivides a plane (U cr, pd) onto the area of the efficient electron multiplication and the area where the electrons leave the gas gap without multiplication. On the basis of this dependence analogs of Paschen’s curves are constructed, which contain an additional new upper branch. This brunch demarcates the area of discharge and the area of e-beam.The mechanism of the formation of the recently created atomospheric pressure subnanosecond e-beams is discussed. It is shown that the beam of the runaway electrons is formed at an instant when the plasma of the discharge gap approaches to the runaway electrons is formed at an instant when the plasma of the discharge gap approaches to the anode. In this case a basic pulse of the electron beam is formed according to the non-local criterion of the runaway electrons generation.The role of the discharge gap preionization by the fast electrons, emitted from the plasma non-uniformities on the cathode, as well as a propagation of an electron multiplication wave from cathode to anode in a dense gas are considered.

scholarly journals Numerical implementation of a non local criterion to describe the failure of laminates with stress concentrations

2010 ◽  
pp. 89-104
Author(s):  
Stéphanie Miot ◽  
Christian Hochard ◽  
Noël Lahellec
Keyword(s):  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Numerical Implementation ◽  
Stress Concentrations ◽  
Local Criterion ◽  
Mean Values ◽  
Behavioural Model ◽  
Non Local ◽  
The Mean

A non local ply scale criterion was previously developed for predicting the failure of balanced woven ply structures with stress concentrations. This non local criterion was based on the mean values determined over a Fracture Characteristic Volume (FCV). A behavioural model was developed from a classical Continuum Damage Mechanics (CDM) model. The FCV approach and the CDM behavioural model were implemented in ABAQUS and applied to the case of unbalanced woven ply. Comparisons are made between the experimental data and the modelling predictions obtained on plates with open holes, notches and saw cuts. The numerical implementation of this approach is studied in this paper.

A NON-LOCAL CRITERION OF STRENGTH

1988 ◽  
pp. 128-145
Author(s):  
M. Hlaváček ◽  
V. Kafka
Keyword(s):  
Local Criterion ◽  
Non Local
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