scholarly journals Fundamentals of electro-mechanically coupled cohesive zone formulations for electrical conductors

2021 ◽  
Author(s):  
T. Kaiser ◽  
A. Menzel
Keyword(s):  
Electrical Properties ◽  
Cohesive Zone ◽  
Jump Conditions ◽  
Finite Element Implementation ◽  
Interface Damage ◽  
Faraday’S Law ◽  
Micro Cracks ◽  
Electrical Conductors ◽  
Damage Processes ◽  
Stationary Problems

AbstractMotivated by the influence of (micro-)cracks on the effective electrical properties of material systems and components, this contribution deals with fundamental developments on electro-mechanically coupled cohesive zone formulations for electrical conductors. For the quasi-stationary problems considered, Maxwell’s equations of electromagnetism reduce to the continuity equation for the electric current and to Faraday’s law of induction, for which non-standard jump conditions at the interface are derived. In addition, electrical interface contributions to the balance equation of energy are discussed and the restrictions posed by the dissipation inequality are studied. Together with well-established cohesive zone formulations for purely mechanical problems, the present developments provide the basis to study the influence of mechanically-induced interface damage processes on effective electrical properties of conductors. This is further illustrated by a study of representative boundary value problems based on a multi-field finite element implementation.

Electrical Properties of AlN-SiC Ceramics

2006 ◽  
Vol 317-318 ◽  
pp. 641-644
Author(s):  
Ryota Kobayashi ◽  
Junichi Tatami ◽  
Toru Wakihara ◽  
Takeshi Meguro ◽  
Katsutoshi Komeya
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Seebeck Coefficient ◽  
Gas Flow ◽  
Room Temperature ◽  
Xrd Analysis ◽  
Sic Ceramics ◽  
Sic Ceramic ◽  
Powder Compacts ◽  
Electrical Conductors

AlN-SiC ceramics with 0 to 75 mol% of AlN were fabricated through pressureless sintering of very fine AlN and SiC. Powder compacts with different amounts of AlN were fired at 2000°C for 1 h in Argon gas flow using an induction-heating furnace. The microstructure and phases present in the products were evaluated using SEM and XRD. The AlN-SiC ceramics had a porous structure with 30% porosity, and the grain size was increased with the addition of AlN. XRD analysis showed that 2H was a main phase in all samples, though 3C and 6H phases were found in 25 mol%AlN-75 mol%SiC ceramic. The electrical properties of the AlN-SiC ceramics were evaluated at various temperatures ranging from room temperature to 300°C. The electrical conductivity of the AlN-SiC ceramics depended on the amount of AlN and on the temperature. The 75 mol%AlN-SiC ceramic had higher electrical resistance, though the other samples were electrical conductors. The highest electrical conductivity was obtained with the 25 mol% AlN composition, which was 7 S/m at room temperature and 30 S/m at 300°C. The Seebeck coefficient for the AlN-SiC ceramics increased with rising temperatures. The AlN-SiC ceramics with 50 mol%AlN had the highest Seebeck coefficient of 220 2V/K at 300°C.

scholarly journals Studies on explosive antimony. II―Its structure, electrical conductivity, and rate of crystallization

1935 ◽  
Vol 152 (875) ◽  
pp. 47-63 ◽  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Temperature Coefficient ◽  
Microscopic Examination ◽  
Electrical Resistance ◽  
Ohm’S Law ◽  
Electrolytic Deposit ◽  
Faraday’S Law ◽  
Ohm's Law ◽  
Etched Surface

The first paper of this series dealt with the microscopically visible changes in structure that occur when the presumably amorphous electrolytic deposit of antimony "explodes." It was shown that a rapid (20-40 cm/sec) autogenous crystallization spreads spherically throughout the metal, leaving it with an onion-like structure visible on a polished and etched surface as a sequence of closely spaced (2000-3000 per/cm) concentric lines. The present paper is concerned with the nature of the amorphous deposit as revealed by a microscopic examination of etched surfaces, 3, and by a study of its electrical resistance, 4, The rate of crystallization at temperatures below that at which explosion occurs has also been determined, 5. It is found that the explosive deposits are characterized by a heterogeneous gel-like structure definitely oriented with respect to the cathode receiving surface. The electrical properties of the deposits are non-metallic in that conductivity is very small and has a positive exponential temperature coefficient. Ohm's law is obeyed, but Faraday's law does not seem to be involved, although a small polarization is built up at the higher temperatures. At temperatures too low to initiate explosion the deposits crystallize at a rate which is independent of the extent to which they have already crystallized. The rate of crystallization increases exponentially with the temperature.

A Quasi-Static Delamination Model with Rate-Dependent Interface Damage Exposed to Cyclic Loading

2018 ◽  
Vol 774 ◽  
pp. 84-89 ◽  
Author(s):  
Roman Vodička ◽  
Katarína Krajníková
Keyword(s):  
Numerical Analysis ◽  
Cyclic Loading ◽  
Cohesive Zone ◽  
Cyclic Load ◽  
Cohesive Zone Model ◽  
Zone Model ◽  
Interface Damage ◽  
Domain Structures ◽  
Rate Dependent ◽  
Damage Process

A model for numerical analysis of interface damage which leads to interface crack initiationand propagation in multi-domain structures under cyclic loading is considered. Modelling of damagetakes into account various relations between interface stresses and displacement gaps providing theresponse of a cohesive zone model, additionally equipped by a kind of viscosity associated to theevolution of the interface damage. Together with repeating loading-unloading conditions, it makesthis damage process to have a fatigue-like character, where the crack appears for smaller magnitudeof the cyclic load than for pure uploading.

scholarly journals A finite deformation electro-mechanically coupled computational multiscale formulation for electrical conductors

2021 ◽  
Author(s):  
T. Kaiser ◽  
A. Menzel
Keyword(s):  
Electrical Properties ◽  
Electric Field ◽  
Finite Deformation ◽  
A Priori ◽  
Three Dimensional ◽  
Coupled Problem ◽  
Direct Extension ◽  
Deformation Processes ◽  
Electrical Conductors ◽  
Theoretical Developments

AbstractMotivated by the influence of deformation-induced microcracks on the effective electrical properties at the macroscale, an electro-mechanically coupled computational multiscale formulation for electrical conductors is proposed. The formulation accounts for finite deformation processes and is a direct extension of the fundamental theoretical developments presented by Kaiser and Menzel (Arch Appl Mech 91:1509–1526, 2021) who assume a geometrically linearised setting. More specifically speaking, averaging theorems for the electric field quantities are proposed and boundary conditions that a priori fulfil the extended Hill–Mandel condition of the electro-mechanically coupled problem are discussed. A study of representative boundary value problems in two- and three-dimensional settings eventually shows the applicability of the proposed formulation and reveals the severe influence of microscale deformation processes on the effective electrical properties at the macroscale.

Review of the Radiation Damage Problem of Organic Specimens in Electron Microscopy

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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