Analysis of Deformation and Damage Processes in Soil-Tool Interaction Problems

1973 ◽

Vol 31 ◽

pp. 476-477

Author(s):

L. Reimer

Keyword(s):

Electron Microscopy ◽

Radiation Damage ◽

Irradiation Time ◽

Dose Effect ◽

Primary Process ◽

Thin Specimen ◽

Secondary Damage ◽

Small Doses ◽

Micro Organisms ◽

Damage Processes

Most information about a specimen is obtained by elastic scattering of electrons, but one cannot avoid inelastic scattering and therefore radiation damage by ionisation as a primary process of damage. This damage is a dose effect, being proportional to the product of lectron current density j and the irradiation time t in Coul.cm−2 as long as there is a negligible heating of the specimen.Therefore one has to determine the dose needed to produce secondary damage processes, which can be measured quantitatively by a chemical or physical effect in the thin specimen. The survival of micro-organisms or the decrease of photoconductivity and cathodoluminescence are such effects needing very small doses (see table).

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Analytical and Experimental Characterization of Damage Processes in Composite Laminates

10.21236/ada198068 ◽

1988 ◽

Author(s):

George J. Dvorak ◽

Norman Laws

Keyword(s):

Composite Laminates ◽

Experimental Characterization ◽

Damage Processes

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Modeling and Simulation of Damage Processes based on a Gradient-Enhanced Free Energy Function

PAMM ◽

10.1002/pamm.201410063 ◽

2014 ◽

Vol 14 (1) ◽

pp. 151-152

Author(s):

Stephan Schwarz ◽

Philipp Junker ◽

Klaus Hackl

Keyword(s):

Free Energy ◽

Modeling And Simulation ◽

Energy Function ◽

Free Energy Function ◽

Damage Processes

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XFEL diffraction: developing processing methods to optimize data quality

Journal of Synchrotron Radiation ◽

10.1107/s1600577514028203 ◽

2015 ◽

Vol 22 (2) ◽

pp. 239-248 ◽

Cited By ~ 61

Author(s):

Nicholas K. Sauter

Keyword(s):

Approximate Model ◽

Difficult Problem ◽

Integration Step ◽

X Rays ◽

Experimental Conditions ◽

Structural Details ◽

Laser Sources ◽

Serial Crystallography ◽

Difference Fourier ◽

Damage Processes

Serial crystallography, using either femtosecond X-ray pulses from free-electron laser sources or short synchrotron-radiation exposures, has the potential to reveal metalloprotein structural details while minimizing damage processes. However, deriving a self-consistent set of Bragg intensities from numerous still-crystal exposures remains a difficult problem, with optimal protocols likely to be quite different from those well established for rotation photography. Here several data processing issues unique to serial crystallography are examined. It is found that the limiting resolution differs for each shot, an effect that is likely to be due to both the sample heterogeneity and pulse-to-pulse variation in experimental conditions. Shots with lower resolution limits produce lower-quality models for predicting Bragg spot positions during the integration step. Also, still shots by their nature record only partial measurements of the Bragg intensity. An approximate model that corrects to the full-spot equivalent (with the simplifying assumption that the X-rays are monochromatic) brings the distribution of intensities closer to that expected from an ideal crystal, and improves the sharpness of anomalous difference Fourier peaks indicating metal positions.

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A bi-dissipative damage model for concrete

Revista IBRACON de Estruturas e Materiais ◽

10.1590/s1983-41952015000100006 ◽

2015 ◽

Vol 8 (1) ◽

pp. 49-65

Author(s):

J. J. C. Pituba ◽

W. M. Pereira Júnior

Keyword(s):

Reinforced Concrete ◽

Structural Engineering ◽

Damage Mechanics ◽

Damage Model ◽

Continuum Damage Mechanics ◽

Concrete Material ◽

Framed Structures ◽

Energy Equivalence ◽

Proposed Model ◽

Damage Processes

This work deals with an improvement of an anisotropic damage model in order to analyze reinforced concrete structures submitted to reversal loading. The original constitutive model is based on the fundamental hypothesis of energy equivalence between real and continuous media following the concepts of the Continuum Damage Mechanics. The concrete is assumed as an initial elastic isotropic medium presenting anisotropy, permanent strains and bimodularity induced by damage evolution. In order to take into account the bimodularity, two damage tensors governing the rigidity in tension or compression regimes are introduced. However, the original model is not capable to simulate the influence of the previous damage processes in compression regimes. In order to avoid this problem, some conditions are introduced to simulate the damage unilateral effect. It has noted that the damage model is agreement with to micromechanical theory conditions when dealing to unilateral effect in concrete material. Finally, the proposed model is applied in the analyses of reinforced concrete framed structures submitted to reversal loading. These numerical applications show the good performance of the model and its potentialities to simulate practical problems in structural engineering.

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Acoustic emission signatures prior to snow failure

Journal of Glaciology ◽

10.1017/jog.2018.43 ◽

2018 ◽

Vol 64 (246) ◽

pp. 543-554 ◽

Cited By ~ 5

Author(s):

ACHILLE CAPELLI ◽

INGRID REIWEGER ◽

JÜRG SCHWEIZER

Keyword(s):

Loading Rate ◽

Critical Phenomenon ◽

Acoustic Emissions ◽

Test Apparatus ◽

Snow Layer ◽

Loading Rates ◽

Damage Process ◽

Damage Processes ◽

Increasing Load ◽

Snow Samples

ABSTRACTSnow slab avalanches are caused by cracks forming and propagating in a weak snow layer below a cohesive slab. The gradual damage process leading to the formation of the initial failure within the weak layer (WL) is still not entirely understood. To this end, we designed a novel test apparatus that allows performing loading experiments with large snow samples (0.25 m2) including a WL at different loading rates and simultaneously monitoring the acoustic emissions (AE) response. By analyzing the AE generated by micro-cracking, we studied the evolution of the damage process preceding snow failure. At fast loading rates, the exponent of the AE energy distribution (b-value) gradually changed, and both the energy rate and the inverse waiting time increased exponentially with increasing load. These changes in AE signature indicate a transition from small to large events and an acceleration of the damage processes leading to brittle failure. For the experiments at slow loading rate, these changes in the AE signature were not or only partially present, even if the sample failed, indicating a different evolution of the damage process. The observed characteristics in AE response provide new insights on how to model snow failure as a critical phenomenon.

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Study of Resistance to Helium Swelling of Lithium-Containing Ceramics under High-Temperature Irradiation

Crystals ◽

10.3390/cryst11111350 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1350

Author(s):

Dmitriy I. Shlimas ◽

Artem L. Kozlovskiy ◽

Askar Kh. Syzdykov ◽

Daryn B. Borgekov ◽

Maxim V. Zdorovets

Keyword(s):

Surface Layer ◽

High Temperature ◽

Radiation Damage ◽

Thermal Annealing ◽

Reactor Core ◽

Strength Properties ◽

Radiation Defects ◽

Temperature Irradiation ◽

Thermal Sintering ◽

Damage Processes

The aim of this work was to study resistance to helium accumulation processes in the structure of the surface layer of lithium-containing ceramics and the subsequent destruction and embrittlement processes, depending on radiation fluence. The objects of study were Li2TiO3-type ceramics obtained by thermal sintering. The fluence dependency of changes in the structural and strength properties of ceramics was determined to be in the range from 1018 to 1022 ion/m2, which corresponded to the concentration of implanted helium from 0.01% to 0.8–1 at.%. Irradiation was carried out at a temperature of 700 °C, which made it possible to simulate the processes of radiation damage that were closest to the real conditions in the reactor core. During the studies carried out, it was found that, at irradiation fluences of 1018–1020 ion/m2, the formation of point radiation defects was equaled by the process of thermal annealing of defects, as a result of which the concentration of defects and their effect on the change in the structural and strength properties of ceramics were insignificant. An increase in the concentration of implanted helium in the structure of the surface layer to above 0.5 at.% led to the dominance of radiation damage processes over the annealing of defects and the formation of gas-filled cavities, which negatively affects the strength of ceramics.

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