Amplitude expansion for the Grinfeld instability due to uniaxial stress at a solid surface

1993 ◽  
Vol 3 (3) ◽  
pp. 681-686 ◽  
Author(s):  
P. Nozières
Keyword(s):  
Solid Surface ◽  
Uniaxial Stress

Microwave resonance method for measuring microliter volumes of free moisture in aviation fuels

2020 ◽  
pp. 49-56
Author(s):  
Vitaly V. Volkov ◽  
Michael A. Suslin ◽  
Jamil U. Dumbolov
Keyword(s):  
Solid Surface ◽  
Free Water ◽  
Resonance Method ◽  
Cavity Resonator ◽  
Maximum Error ◽  
Aviation Fuel ◽  
Fuel Quality ◽  
Microwave Resonance ◽  
Free Moisture ◽  
Microwave Losses

One of the conditions for ensuring the safety of air transport operation is the quality of aviation fuel refueled in aircraft. Fuel quality control is a multi-parameter task that includes monitoring the free moisture content. Regulatory documents establish the content of free water no more than 0.0015% by weight. It is developed a direct electrometric microwave resonance method for controlling free moisture in aviation fuels, which consists in changing the shape of the water drops by pressing them on a solid surface inside a cylindrical cavity resonator. This can dramatically increase dielectric losses. Analytical and experimental analysis of the proposed method is carried out. The control range from 0,5 to 30 μl of absolute volume of moisture in aviation fuels with a maximum error of not morethan 25 % is justified. The sensitivity of the proposed method for monitoring microwave losses in free moisture drops transformed into a thin layer by pressing is an order of magnitude greater than the sensitivity of the method for monitoring microwave losses in moisture drops on a solid surface in a resonator. The proposed method can be used as a basis for the development of devices for monitoring the free moisture of aviation fuels in the conditions of the airfield and laboratory. The direction of development of the method is shown.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

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