Selecting Suitable Probes Distances for Sizing Deep Surface Cracks Using the DCPD Technique

2006 ◽  
Vol 129 (1) ◽  
pp. 205-210 ◽  
Author(s):  
Fumio Takeo ◽  
Masumi Saka ◽  
S. Reaz Ahmed ◽  
Seiichi Hamada ◽  
Manabu Hayakawa
Keyword(s):  
Three Dimensional ◽  
Potential Drop ◽  
Surface Cracks ◽  
Deep Surface ◽  
Input And Output ◽  
Wide Range ◽  
Current Input ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
The Way

In this study, the way to enhance the sensitivity of evaluating deep surface cracks by DCPD technique using four probes is considered. The potential drops across two-dimensional cracks having different depths are analyzed by the three-dimensional finite-element method. The effect of the distance between current input and output probes and the distance between measuring probes on the change in potential drops are analyzed for a wide range of crack depths. By extending the distance between current input and output probes, the change in potential drop with the change in the depth of deeper crack becomes large. But the voltage of potential drop becomes small to measure. Finally, the way to select the appropriate distances between the probes for the measuring sensor is shown from the viewpoints of sensitivity and the required current.

DC Potential Drop Technique Selecting Probes Distances Properly for Sizing Deep Surface Cracks

2005 ◽  
Author(s):  
Fumio Takeo ◽  
Masumi Saka ◽  
Seiichi Hamada ◽  
Manabu Hayakawa
Keyword(s):  
Power Plants ◽  
Potential Drop ◽  
Small Crack ◽  
Surface Cracks ◽  
Structural Components ◽  
Deep Surface ◽  
Close Proximity ◽  
Current Input ◽  
Quantitative Nde ◽  
Drop Technique

D-C potential drop (DCPD) technique is a powerful tool for quantitative NDE of cracks. The technique using four probes which are in close proximity to each other has been proposed for NDE of surface cracks; that is the closely coupled probes potential drop (CCPPD) technique. It has been shown that the sensitivity of CCPPD technique to evaluate a small crack is enhanced significantly in comparison with the usual method. On the other hand, since CCPPD technique has been developed to evaluate a small crack sensitively, it is not fit to evaluate deep cracks which are sometimes found in the structural components of power plants. The objective of this study was to enhance the sensitivity of evaluating deep surface cracks. By extending the distance between current input and output probes, the change in potential drop with the change in the depth of deeper crack becomes large. But the voltage of potential drop becomes small to measure, because the current density in the material becomes low. The voltage of the potential drop can be increased by increasing the applying current, but the current would also be limited by the equipment or contacting probes. Then the way to select the appropriate distances between probes from the viewpoints of the sensitivity and the required current has been shown.

Continuum-Micromechanical Modeling of Microcapsules-Based Composites

2017 ◽  
Vol 909 ◽  
pp. 311-316
Author(s):  
Abdalla Ahmed ◽  
Kazuaki Sanada ◽  
Mohamed Fanni ◽  
Ahmed Abd El-Moneim
Keyword(s):  
Phase Change Materials ◽  
Three Dimensional ◽  
Micromechanical Modeling ◽  
Service Needs ◽  
Self Healing ◽  
Numerical Investigations ◽  
Wide Range ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Properties Of Composites

Microcapsules are used in a wide range of applications, especially in self-healing composite materials and phase change materials. There is a growing body of literature that recognizes the importance of reinforcement on the mechanical properties of composites, however the effect of microcapsules during service needs to be further investigated. In this study, numerical investigations were conducted to examine the effects of the various geometric parameters on the mechanical behavior of microcapsules-based composites. The effective Young’s modulus and Poisson’s ratio of core-shell microcapsules distributed in a continuous matrix were predicted. A detailed three-dimensional finite element modeling (FEM) was presented. The numerical results were compared with a hierarchical proposed analytical model for three-constituent composites. Good agreements were achieved.

scholarly journals Analysis and Mitigation of Stray Capacitance Effects in Resistive High-Voltage Dividers

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2278
Author(s):  
Jordi-Roger Riba ◽  
Francesca Capelli ◽  
Manuel Moreno-Eguilaz
Keyword(s):  
High Voltage ◽  
Three Dimensional ◽  
Alternating Current ◽  
Stray Capacitance ◽  
Element Analysis ◽  
Wide Range ◽  
Resistive Divider ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Capacitance Effects

This work analyzes the effects of the parasitic or stray distributed capacitance to ground in high-voltage environments and assesses the effectiveness of different corrective actions to minimize such effects. To this end, the stray capacitance of a 130 kV RMS high-voltage resistive divider is studied because it can severely influence the behavior of such devices when operating under alternating current or transient conditions. The stray capacitance is calculated by means of three-dimensional finite element analysis (FEA) simulations. Different laboratory experiments under direct current (DC) and alternating current (AC) supply are conducted to corroborate the theoretical findings, and different possibilities to mitigate stray capacitance effects are analyzed and discussed. The effects of the capacitance are important in applications, such as large electrical machines including transformers, motors, and generators or in high-voltage applications involving voltage dividers, conductors or insulator strings, among others. The paper also proves the usefulness of FEA simulations in predicting the stray capacitance, since they can deal with a wide range of configurations and allow determining the effectiveness of different corrective configurations.

scholarly journals 3-D Finite Element Investigation of Flux Regulation Performance of a Novel Hybrid Excitation Brushless Claw-Pole Alternator

2012 ◽  
Vol 614-615 ◽  
pp. 1226-1229
Author(s):  
Dong Wei Qiao ◽  
Xiu He Wang ◽  
Chang Qing Zhu
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Analysis ◽  
Wide Range ◽  
Hybrid Excitation ◽  
Field Control ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Control Principle

In consideration of low power density of electric excitation claw-pole alternator (EECA) and some difficulties in magnetic field regulation of permanent magnet claw-pole alternator (PMCA), a novel hybrid excitation brushless claw-pole alternator (HEBCA) is proposed in this paper. Its structure and field control principle are described. Three dimensional finite element analysis is used to obtain the no-load magnetic field distributions and field control capability under different field currents. The result shows that the flux of the prototype machine can be adjusted over a wide range with a relatively low field current

Surface Cracks in Round Bars under Cyclic Tension or Bending

2008 ◽  
Vol 378-379 ◽  
pp. 341-354 ◽  
Author(s):  
Andrea Carpinteri ◽  
Sabrina Vantadori
Keyword(s):  
Three Dimensional ◽  
Fatigue Behaviour ◽  
Surface Cracks ◽  
Displacement Method ◽  
Element Analysis ◽  
Cyclic Tension ◽  
Step Procedure ◽  
Dimensional Finite Element ◽  
The One ◽  
Three Dimensional Finite Element

The fatigue growth of a surface crack in a metallic round bar under cyclic tension or bending is analysed. The stress-intensity factor (SIF) along the crack front is computed through a three-dimensional finite element analysis and the one-quarter point displacement method. The results are compared with those presented by other Authors. Then, the fatigue behaviour of the cracked bar is numerically determined by a step-by-step procedure.

Limit Loads for Circumferential Cracked Pipe Bends under In-Plane Bending

2006 ◽  
Vol 321-323 ◽  
pp. 38-42
Author(s):  
Yun Jae Kim ◽  
Chang Sik Oh ◽  
Bo Kyu Park ◽  
Young Il Kim
Keyword(s):  
Three Dimensional ◽  
Surface Cracks ◽  
Plastic Limit ◽  
Limit Loads ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Dimensional Finite Element ◽  
Plane Bending ◽  
Elastic Perfectly Plastic ◽  
Three Dimensional Finite Element

This paper presents limit loads for circumferential cracked pipe bends under in-plane bending, based on detailed three-dimensional finite element limit analyses. FE analyses are performed based on elastic-perfectly-plastic materials and the geometrically linear assumption. Both through-wall cracks and part-through surface cracks (having constant depths) are considered, together with different crack locations (extrados and intrados). Based on the FE results, closed-form approximations are proposed for plastic limit loads of pipe bends. It is found that limit loads of pipe bends are smaller than those of straight pipes, but are close for deep and long cracks.

scholarly journals A New Technique for Intergranular Crack Formation in Alloy 600 Steam Generator Tubing

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Tae Hyun Lee ◽  
Il Soon Hwang ◽  
Han Sub Chung ◽  
Jang Yul Park
Keyword(s):  
Steam Generator ◽  
Three Dimensional ◽  
Potential Drop ◽  
Crack Size ◽  
Element Analysis ◽  
Current Test ◽  
Dimensional Finite Element ◽  
Integrity Management ◽  
A New Technique ◽  
Three Dimensional Finite Element

For the integrity management of steam generator (SG) tubes, nondestructive evaluation performed using eddy current test (ECT) is necessary in the assessment. The reliability of ECT evaluation is dependent on the accuracy of ECT for various kinds of defects. For basic calibration and qualification of these techniques, cracked SG tube specimens having mechanical and microstructural characteristics of intergranular cracks in the field are needed. To produce libraries of laboratory-degraded SG tubes with intergranular cracks, a radial denting method was explored for generating inside diameter and outside diameter axial cracks by three-dimensional finite element analysis and experimental demonstration. The technique is proven to be applicable for generating axial cracks with long and shallow geometries as opposed to the semicircular cracks typically obtained by the internal-pressurization method. In addition, a direct current potential drop method with array probes was developed for accurate monitoring and controlling of crack size and shape. By these methods, long and shallow intergranular axial cracks more typical of actual degraded SG tubes were successfully produced.

Investigation on T11-Stress for Semi-Elliptical Surface Cracks in Finite Thickness Plates under Remote Tension

2012 ◽  
Vol 525-526 ◽  
pp. 237-240
Author(s):  
Wei Xie
Keyword(s):  
Finite Element ◽  
Crack Front ◽  
Finite Thickness ◽  
Three Dimensional ◽  
Fracture Analysis ◽  
Surface Cracks ◽  
Finite Element Analyses ◽  
Current Stress ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In the present work, three-dimensional finite element analyses have been conducted to calculate the-stress for semi-elliptical surface cracks in finite thickness plates under remote tension. The-stress solutions are presented along the crack front for cracks with values of 0.2, 0.4, 0.6 or 0.8 and values of 0.2, 0.4, 0.6 or 1.0. The current-stress solutions are suitable to be used as the constraint parameter for the fracture analysis.

Three-dimensional tensile stress concentration in countersunk rivet holes

2007 ◽  
Vol 111 (1126) ◽  
pp. 777-786 ◽  
Author(s):  
A. Bhargava ◽  
K. N. Shivakumar
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Tensile Stress ◽  
Three Dimensional ◽  
Design Equation ◽  
Finite Element Stress Analysis ◽  
Wide Range ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Tension Loading

Abstract A detailed and accurate three-dimensional finite element stress analysis was conducted on countersunk rivet holes in a plate subjected to tension loading. The analysis included a wide range of countersunk depths, plate thicknesses, countersunk angles and plate widths. The study confirmed some of the previous results, addressed their differences, provided many new results, and investigated countersunk angle and width effects. Using the detailed FE results and the limiting conditions, a design equation for stress concentration was developed and verified.

Sign in / Sign up

Export Citation Format

Share Document