scholarly journals Electrical conductivity determination of semiconductors by utilizing photography, finite element simulation and resistance measurement

2021 ◽  
Author(s):  
Rui Wang ◽  
Ralf Moos
Keyword(s):  
Electrical Conductivity ◽  
Finite Element ◽  
Finite Element Simulation ◽  
Arbitrary Shape ◽  
3D Model ◽  
Geometry Factor ◽  
Element Simulation ◽  
Semiconductor Specimen ◽  
Measured Resistance

AbstractA new method is developed to measure precisely and reliably the electrical conductivity of a block-shaped semiconductor specimen using four-wire technique with electrodes in arbitrary shape and position. No effort for accurate electrode preparation is necessary anymore. This method may be especially applied to measure the conductivity of ceramics at high temperatures, when typical spring-contacts or clamp-contacts are not possible and instead wound wires are used for electrically contacting the specimen. The method comprises the following: An image of the specimen is processed to a 3D model. By applying a finite element simulation on this 3D model, a form factor (also called geometry factor) that considers the effect of the non-infinitesimally small electrodes is calculated. Together with the measured resistance (preferably in four-wire technique), the actual conductivity of the sample is derived. Experimental results confirmed the validity of the proposed method. As a limitation of the method, the conductivity of the specimen should be within the range of 0.01 Sm−1 and 106 Sm−1.

Local Approach of Fracture in the Ductile Regime and Application to VVER Materials

2002 ◽  
Author(s):  
B. Z. Margolin ◽  
V. I. Kostylev ◽  
E. Keim ◽  
R. Chaouadi
Keyword(s):  
Finite Element ◽  
Crack Resistance ◽  
Ductile Fracture ◽  
Finite Element Simulation ◽  
Volume Fraction ◽  
Stress Triaxiality ◽  
Local Approach ◽  
Gurson Model ◽  
Element Simulation

Within the TACIS R2.06/96 project: “Surveillance Program for VVER 1000 Reactors”, sponsored by the European Commission, the local approach of fracture has been applied in the ductile regime. Two different models were applied and compared, namely Tvergaard-Needleman-Gurson versus Prometey model. The main tasks are: • perform special Local Approach experiments on smooth and notched cylindrical specimens; • predict JR-curve on the basis of the ductile fracture models; • compare two models of ductile fracture, namely, the Tvergaard-Needleman-Gurson model and the Prometey model. In this paper, the Tvergaard-Needleman-Gurson and Prometey models are briefly described. The parameters of both models were calibrated by using experimental data obtained on tensile specimens. While only smooth tensile specimens are used to calibrate the Tvergaard-Needleman-Gurson model, notched tensile in addition to smooth tensile specimens are used to calibrate the Prometey model. In the latter, standard smooth tensile specimens are used to determine the mechanical properties (the yield stress σy, the ultimate stress σu, the ultimate elongation δu, the area reduction Z) and notched cylindrical specimens to determine the strain at rupture. The numerical analysis comprises essentially two steps: • Step 1: finite element simulation of the smooth tensile specimen (determination of true stress-strain curve and critical void volume fraction for the Tvergaard-Needleman-Gurson model) and simulation of the notched cylindrical specimen up to rupture (determination of stress triaxiality for the Prometey model); • Step 2: finite element simulation of the 2T CT specimen and determination of the crack resistance behaviour in the ductile regime (J-Δa curve). It is found that both models were able to correctly predict the crack resistance behaviour of the investigated materials. The numerical and the experimental results were in very good agreement. The main difference between the two models is that the required number of calibrated parameters in the Prometey model is less than in the Tvergaard-Needleman-Gurson model but additional tests on notched specimens are required for the Prometey model.

Finite Element Simulation of Welding Sequences Effect on Residual Stresses in Multipass Butt-Welded Stainless Steel Pipes

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
S. Feli ◽  
M. E. Aalami Aaleagha ◽  
M. Foroutan ◽  
E. Borzabadi Farahani
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Heat Source ◽  
Residual Stresses ◽  
Finite Element Simulation ◽  
3D Model ◽  
Axisymmetric Model ◽  
Element Simulation ◽  
Starting Point ◽  
Welding Sequences

In this paper, a finite element simulation, based on abaqus software is presented for analyzing the temperature history and the residual stress states in multipass welds in stainless steel pipe. The uncoupled thermal–mechanical a three-dimensional (3D) model and a two-dimensional (2D) model are developed. The volumetric heat source with double ellipsoidal distribution for front and rear heat source, proposed by Goldak and Akhlaghi, has also been used. Furthermore, a moving heat source has been modeled by abaqus subroutine DFLUX. A user subroutine FILM has also been used to simulate the combined thermal boundary conditions. The results of both a 3D model and a 2D axisymmetric model which are compared with the available experimental measurements show good agreements. Predictions show that the axial and hoop residual stresses in a 3D model and a 2D axisymmetric model have the same distributions in all locations except the starting point of welding. The effects of welding sequences on the thermal and structural analysis are also investigated. Four types of welding sequences for circular welds of pipe have been used and thermal history and axial and hoop residual stresses are compared. Predictions show that for other locations (except the starting point of welding) there are no important differences of axial and hoop residual stresses for welding sequences and they have the same distribution along axial direction.

Determination of thermophysical properties of yacon (Smallanthus sonchifolius) to be used in a finite element simulation

2013 ◽  
Vol 67 ◽  
pp. 1163-1169 ◽  
Author(s):  
Camila Augusto Perussello ◽  
Viviana Cocco Mariani ◽  
Maria Lúcia Masson ◽  
Fernanda de Castilhos
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Thermophysical Properties ◽  
Smallanthus Sonchifolius ◽  
Element Simulation

scholarly journals Mechanical property determination of bone through nano- and micro-indentation testing and finite element simulation

2008 ◽  
Vol 41 (2) ◽  
pp. 267-275 ◽  
Author(s):  
Jingzhou Zhang ◽  
Glen L. Niebur ◽  
Timothy C. Ovaert
Keyword(s):  
Mechanical Property ◽  
Finite Element ◽  
Finite Element Simulation ◽  
Indentation Testing ◽  
Element Simulation ◽  
Micro Indentation
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