Eta Factors Research Articles

Big Data Visualization by MapReduce for Discovering the Relationship Between Pollutant Gases

Big data mining and pollution are extremely important issues in todays. An innovative method in this study was used for visually discovering the relationship between pollutant gases by MapReduce. One dimensional, two-dimensional, and three-dimensional visualization used to visualize the data, that was processed as an hourly reading for one year from an air quality monitoring station to study the behaviors of pollutant gases distribution, and to show graphically the distribution of one, two, or three gases. The number of readings used in this paper are 8760 hourly readings for each of the five pollutant gases under this study. Pearson correlation used to explore numerically the correlation between the pollutant gases, and eta factor used to evaluate the effect of one gas on the other pollutant gases. We found out by both methods, visually and numerically the same facts that related between the pollutant gasses. The ozone has a moderate negative correlation of value -0.622 with nitrogen dioxide, and weak negative correlation of value -0.248 with carbon monoxide, and -0.155 with carbon dioxide. Ozone has approximately no correlation of value .060 with silver dioxide. The carbon monoxide has moderate positive correlation of value 0.364 with carbon dioxide. The eta factor between ozone and nitrogen dioxide is very weak of values 0.292, and 0.009 with Sulphur dioxide, this proved an important fact that the ozone, nitrogen dioxide, and Sulphur dioxide sources are different. The study recommends that each country must analysis visually and numerical the big data that was collected yearly from the monitoring stations to control the pollution gases especially near the large industrial factories.

Sensitivity of Iodine-Mediated Stratospheric Ozone Loss Chemistry to Future Chemistry-Climate Scenarios

As the chemical and physical state of the stratosphere evolves, so too will the rates of important ozone-destroying reactions. In this work, we evaluate the chemistry-climate sensitivity of reactions of stratospheric iodine, reporting the iodine alpha factor (the efficiency of ozone loss mediated by a single iodine atom relative to the ozone loss mediated by a single chlorine atom) and the iodine eta factor (the efficiency of ozone loss mediated by a single iodine atom relative to the ozone loss mediated by a single chlorine atom in a benchmark chemistry-climate state) as a function of future greenhouse gas emissions scenario. We find that iodine-mediated ozone loss is much less sensitive to future changes in the state of the stratosphere than chlorine- and bromine-mediated reactions. Additionally, we demonstrate that the inclusion of the heterogeneous reaction of ozone with aqueous iodide in stratospheric aerosol produces substantial enhancements in the iodine alpha and eta factors relative to evaluations that consider gas-phase iodine reactions only. We conclude that the share of halogen-induced ozone loss due to reactions of iodine will likely be greater in the future stratosphere than it is today.

The effectiveness of a training program based on international standards of instructional technology in improving teaching practices and professional leadership skills among Arabic language teachers at the secondary level: فاعلية برنامج تدريبي قائم على المعايير العالمية لتكنولوجيا التّعليم في تحسين الممارسات التّدريسية ومهارات القيادة المهنية لدى معلمي اللغة العربية بالمرحلة الثانوية

The current study aimed to identify the effectiveness of a training program based on international standards of instructional technology in improving teaching practices and professional leadership skills of Arabic language teachers at the secondary level in the State of Kuwait, and to achieve the study objectives, the semi-experimental approach based on one group was used with pre-post measurement. Of (30) teachers of the Arabic language at the secondary stage in the Hawalli Educational Zone in the State of Kuwait, and a note card for teaching practices and a measure of professional leadership skills were prepared, and their validity and reliability were confirmed. The results showed a statistically significant difference at the level of significance (α ≤ 0.05) between the average scores of the pre and post application of the observation card related to the teaching practices of teachers attributed to the benefit of the training program, and the program has achieved effectiveness in improving the teaching practices of teachers amounting to (0.95) according to ETA. A statistically significant difference was found at the level of significance (α ≤ 0.05) between the average scores of pre and post application in the professional leadership skills scale for teachers attributed to the benefit of the training program. The program also achieved effectiveness in improving teachers' professional leadership skills, reaching (0.94), according to the ETA factor. The study recommended the adoption of the training program used by the study, as it was based on international standards for educational technology, working to spread it and circulating it within the training programs for Arabic language teachers, and paying attention to holding training courses for teachers during service to familiarize them with international standards for educational technology.

New formulation for fracture toughness characterization using four-point bend specimens

The present work aims to present a new complete procedure to characterize fracture toughness in terms of stress intensity factor K or the J−integral for Mode I of loading using four-point bend specimens. Four-Point Bend (4PB) specimens are shown to be valid configurations for fracture toughness characterization tests with certain advantages when compared to traditional three-point bend geometries and single edge notch tension SE(T) specimens under clamped conditions. Fracture toughness is a key parameter in defining critical flaw sizes in a fitness-for-service (FFS) procedure based upon fracture mechanics principles. Accurate estimation of fracture toughness is therefore necessary to assess the integrity of critical engineering structures by following the failure assessment diagram concept. Extensive 3D finite element analyses were performed to obtain the analytical relationships necessary to calculate the fracture toughness parameters. New formulas are provided for the elastic compliance, stress intensity factor, and eta factor for calculating fracture toughness valid for four-point bend specimens. Using the distance between inner and outer roller supports as a normalization parameter, the stress intensity factor and the normalized elastic compliance equations are shown to be independent of the specimen supporting configuration. The eta factor based upon the CMOD is dependent on the distance between external and internal roller supports as well as a∕W. Experimental fracture tests were carried out to check the practicality of the methodology. J-R curves obtained by four-point bend specimens were compared to resistance curves derived from three-point SE(B) specimens and clamped SE(T) samples which are standardized specimens. The results show that the four-point bend specimens provide reliable fracture toughness values somewhat higher than three-point bend geometries.

Estimation of plastic eta factors for clamp-end SE(T) specimens with undermatched weld metal based on 3D finite element analyses

To ensure the corrosion resistance property of girth welds of clad or lined pipes, nickel based alloy consumable is often utilized, indicating that the yield strength of base metal is higher than that of weld metal. To test the fracture toughness of the undermatched weld metal, the plastic eta factors for clamp-end single-edge tension specimens with various configurations and different undermatched levels are determined based on detailed 3D finite element analyses. Finally, a set of equations of the plastic eta factor is developed.

Plastic eta factor and blunting line for characterization of fracture toughness of dissimilar metal weld

AbstractThis paper addresses the fracture toughness evaluation procedure of different zones of dissimilar metal weld (DMW). Experiments have been conducted on compact tension specimens from DMW joint having initial notch in centre of weld and fusion boundaries. Plastic eta factors (ηp) and slope of blunting line (bl) for above specimens have been evaluated numerically. Experimental load, load line displacement, and crack growth data along with numerically evaluated ηp and bl have been used for calculation of fracture resistance curve and initiation fracture toughness, and finally, it has been compared with that evaluated as per ASTM E1820 and ESIS standard.

Investigation on plastic eta factors for SE(T) specimens with undermatched weld metal based on plane strain finite element analysis

At present, the growing demand for the subsea transport of the highly corrosive media has driven the oil and gas industries to use clad or lined pipes. In order to ensure the corrosion resistance performance of circumferential welds in clad or lined pipes, nickel based alloy consumables are routinely used, which indicates that the yield strength of the weld metal is lower than that of base metal. To measure the toughness of the undermatched weld metal, plastic eta factors for clamped-end and pin-loaded single-edge tension specimens with a wide range of configurations and different undermatched levels were obtained based on detailed plane strain finite element analysis. From this analysis, a set of equations for the plastic eta factor is proposed.

Load separation in 17 mm wide CT specimen of Zr-2.5Nb pressure tube material

In PHWR community 17 mm wide curved compact tension (CCT) specimen is most commonly used for fracture toughness testing in axial direction of pressure tube. This specimen geometry is different from Conventional CT specimen (ASTM E 1820–11) in two aspects. First being the curvature of the CCT specimen and second is that it does not meet the alternate thickness criteria of 2≤W/B≤4 for B = 3.6 mm. Despite these differences, the eta and gamma factors used for the fracture toughness measurement of Conventional CT specimen according to ASTM E 1820 –11 are also applied for CCT specimen. In this work, 17 mm wide blunt notched Conventional CT specimens of Zr-2.5Nb pressure tube with different a/W ratios between 0.3 and 0.7 were loaded up to maximum load. The load separabilty was checked and eta factor was calculated using load separation method. The investigation of separation parameter (S) for reference cracks (ai/W) between 0.45 and 0.7 showed that (a) load was separable over whole range of plastic displacement for the CT specimens with ai/W between 0.45 and 0.7, except for small initial inseparable region, and (b) load was not separable over whole range of plastic displacement for the CT specimens with ai/W of 0.35 and 0.40. The small inseparable region in the CT specimens with ai/W between 0.45 and 0.7 is reported in literature to be due to initial blunting of the CT specimen. The eta factor, calculated using load separation method proposed by Sharobeam and Landes, was found to have a constant value of 2.08 for ai/W in range of 0.45 and 0.70. The eta factor was found to be lower than that reported by Sharobeam and Landes as well as in ASTM 1820 – 11. Since load was not separable for CT specimens with a/W of 0.35 and 0.4, eta factor derived for this CT geometry cannot be used for a/W below 0.45.

Comparison of J Equations for SENT Specimens

A test standard for single edge notched tension (SENT) fracture toughness testing was issued in 2014 by British Standards as BS 8571:2014. Prior to BS 8571, most guidance on SENT test methodology was taken from DNV RP F108:2006 for installation of girth welds under high strain, which is still commonly cited by pipeline design and fabrication standards such as DNV OS F101:2013 for subsea pipelines. The intention of BS 8571 was to maintain some continuity with DNV RP F108 to allow users time to adopt the new Standard, and therefore BS 8571 included the DNV specimen design and J formulae, but also offered a different J approach based on work by Shen & colleagues (2009) from CanmetMaterials, for specimen designs currently beyond those permitted in DNV RP F108 but included in BS 8571. However, recent independent research by Zhu & McGaughy (2015) has identified an error in the K solutions adopted from DNV RP F108 into BS 8571, and therefore, there is a need to review the various equations to calculate J for SENT specimens to ensure that the optimum approach is employed in BS 8571, both in terms of accuracy and ease of application. A review of different published solutions for the elastic K solutions, and plastic eta factor solutions, which comprise parts of the calculation of J has been carried out, to compare the range of possible solutions in relation to those currently used in BS 8571:2014. Furthermore numerical modelling of crack tearing resistance curves was undertaken to compare the two different methods currently given in BS 8571 to determine which would provide the best single approach appropriate for all SENT specimens tested to BS 8571. The analyses determined that the ‘Canmet’ solutions should be used for a single equation for J to cover specimens with W/B ratios from 0.5 to 2 in future versions of BS 8571. This change will improve the accuracy of the determination of J from SENT specimens, with a simpler method, but little difference to the values of J for typical specimens which have been tested using BS 8571 to date.

Effect of Crack Front Curvature on Experimental Evaluation of J-Integral for Single-Edge Bend Specimens

Abstract This paper presents three-dimensional (3D) finite element analyses of plane-sided single-edge bend specimens to investigate the effect of the crack front curvature on the accuracy of the average J-integral (J) evaluated over the crack front using the plastic eta-factor-based approach specified in ASTM E1820-11. Specimens with average crack lengths of 0.3, 0.5, and 0.7 and thickness-to-width ratios of 1, 0.5, and 0.25 were analyzed. The analysis was based on the J2 deformation theory of plasticity and assumed stationary cracks with sharp crack tips. The curved crack front was characterized by a power-law expression proposed by Nikishikov et al. that was validated using crack front data collected in this study. The plastic eta factors specified in ASTM E1820-11 and proposed by Zhu et al. were employed. The analysis results indicate that the errors in the plastic eta-factor-based J were generally between −7 % (i.e., underestimation) and 6 % (i.e., overestimation) for the specimens that had curved crack fronts with crack front curvature equal to the maximum allowable value specified in ASTM E1820-11. Based on the analysis results, crack front straightness criteria that are in most cases less stringent than those specified in ASTM E1820-11 are recommended. The suggested criteria could potentially lead to reduced specimen rejection rates and cost savings.

Investigation of plastic eta factors for clamped SE(T) specimens based on three-dimensional finite element analyses

Three-dimensional finite element analyses of clamped single-edge tension (SE(T)) specimens are performed to evaluate the plastic eta factors (i.e. ηpl) for computing the J-integral. The analysis covers both plane-sided and side-grooved specimens with a wide range of specimen configurations (a/W from 0.2 to 0.7 and B/W equal to 1 and 2) and strain hardening exponents (n=5, 8.5, 10, 15 and 20). Based on the analysis results, a set of expressions for ηpl are proposed.

Fracture Toughness Measurement by Using Pipe-ring Specimens

Fracture toughness Measurement of thin walled pipe-line with flaw or defect in most critical axial direction is difficult. In this paper the non-standard modified specimens has been proposed for simple fracture testing. The comparison between fracture behaviour of single edge notch bending (SENB), compact tension (CT) and pipe-ring specimens with notch and fatigue pre-crack were analysed. In order to determine CTOD-R curve the normalization method by using remote measurement CMOD has been used for all specimens. For non-standard pipe ring pre-cracked specimens the plastic correction eta factor is determined by using finite element method. The stable crack growth initiation was determined also as a crack tip surface strain-relaxation by using stereo-optical grading method. Comparison between CTOD-R curves of all three types of specimens shows quite similar fracture toughness in stable crack initiation range.

Further results in J and CTOD estimation procedures for SE(T) fracture specimens – Part II: Weld centerline cracks

This work examines the effect of weld strength mismatch on J and CTOD fracture parameters using single edge notch tension (SE(T)) specimens. A central objective of the study is to enlarge on previous J and CTOD estimation procedures based upon plastic eta factors (η) described in Part I for centerline-cracked welds. The present analyses provide a large set of η-factors for a wide range of crack sizes (a/W-ratio) and material properties, including different levels of weld strength mismatch, which are applicable in improved estimation equations for J and CTOD for weld centerline notched SE(T) specimens.

Effects of weld strength mismatch on J and CTOD estimation procedure for SE(B) specimens

This work examines the effect of weld strength mismatch on fracture toughness measurements defined by J and CTOD fracture parameters using single edge notch bend (SE(B)) specimens. A central objective of the present study is to enlarge on previous developments of J and CTOD estimation procedures for welded bend specimens based upon plastic eta factors (η) and plastic rotational factors (rp). Very detailed non-linear finite element analyses for plane-strain models of standard SE(B) fracture specimens with a notch located at the center of square groove welds and in the heat affected zone provide the evolution of load with increased crack mouth opening displacement required for the estimation procedure. One key result emerging from the analyses is that levels of weld strength mismatch within the range ±20% mismatch do not affect significantly J and CTOD estimation expressions applicable to homogeneous materials, particularly for deeply cracked fracture specimens with relatively large weld grooves. The present study provides additional understanding on the effect of weld strength mismatch on J and CTOD toughness measurements while, at the same time, adding a fairly extensive body of results to determine parameters J and CTOD for different materials using bend specimens with varying geometries and mismatch levels.

Work of fracture and cohesive stress distribution resulting from triaxiality dependent cohesive zone model

A new law has been proposed to describe the distribution of the cohesive forces present within the internally structured nonlinear zone that precedes the leading edge of a moving crack contained within a nonelastic solid. The nonlinear effects are modeled by the narrow strips emanating from the crack front and endowed with a certain internal structure (unlike the classic models of Barenblatt and Dugdale). The bulk of the material, though, is assumed to behave as linear elastic solid. Mathematical form the law resembles somewhat the Planck's formula used to explain radiation given off by a perfectly black body at very short wavelength of the visible light spectrum. With Sneddon's integral transformations employed and properly modified, the quantities essential in the Nonlinear Mechanics of Fracture have been quantified. In particular another so-called `ubiquitous eta factor' is discussed and related to the material microstructure by means of a certain transcendental equation. The eta-factor enters the formula for the specific work of fracture measured with specimens of various geometrical and loading configurations, and so far is known only empirically. Both the stationary and quasi-static crack problems are discussed. It has been shown that the variations in the microstructural parameters strongly affect the process zone along with the associated work of separation. The other important factors that influence the cohesive stress distribution and all the resulting fracture parameters, specifically those that are responsible for a ductile-to-brittle transition of fracture mode, are the characteristics of the state of stress induced in the vicinity of the crack front. These 3D effects are best represented by the triaxiality parameter, defined as the ratio of the mean stress to the von Mises effective stress

Calculation of Energy Transaction Allocation Factors

The ability to allocate the MW loading on transmission lines and groups of lines is the basis of NERC's "flow based" transmission allocation system. In such a system, the MW flows must be allocated to each line or group of lines in proportion to the MW's being transmitted by each transaction. This is accomplished through the use of the linear power transfer distribution factors. Unfortunately, no linear allocation models exist for other transmission phenomena such as MW losses, MVA flows, etc. This paper presents a methodology to calculate energy transaction allocation factors (ETA factors, or η factors), using the well-known process of integration of a first derivative function. The factors give a highly accurate allocation of any nonlinear transmission system quantity to the active transactions placed on a transmission system.

Calculation of energy transaction allocation factors

The ability to allocate the MW loading on transmission lines and groups of lines is the basis of NERCs flow based transmission allocation system. In such a system, the MW flows must be allocated to each line or group of lines in proportion to the MWs being transmitted by each transaction. This is accomplished through the use of the linear power transfer distribution factors. Unfortunately, no linear allocation models exist for other transmission phenomena such as MW losses, MVA flows, etc. This paper presents a methodology to calculate energy transaction allocation factors (ETA Factors, or /spl eta/ factors), using the well-known process of integration of a first derivative function. The factors give a highly accurate allocation of any nonlinear transmission system quantity to the active transactions placed on a transmission system.

A JD expression for the double edge notch tension configuration

The paper derives an expression for the plastic component, JDP, of the deformation J integral, JD, for the double edge notch tension configuration. JDP is expressed in terms of the energy and complementary energy integrals via eta factors, whose values are obtained by ensuring that JDP assumes the correct form at the two extreme levels of deformation: extensive deformation at limit load conditions and small-scale yielding. The expression gives a greater JDP value than that given by the expression which is obtained by assuming that the remaining ligament width is small compared with the specimen width; this latter expression is sometimes used when determining a JDP crack growth resistance curve using a double edge notch tension specimen.

The representation of J in terms of eta factors and energy integrals for an elastic softening solid

With a knowledge of the opening displacement at the initial crack tip, and J as determined from measurements using specimens with different initial crack sizes, Li and Ward have been able to obtain the complete softening p (stress)− v (relative displacement) curve of an elastic softening material displaying cohesive zone characteristics. The present paper investigates whether J can be determined using a single specimen, i.e. one initial crack size, via load and load-point displacement measurements and thereby energy and complementary energy integrals, coupled with the use of appropriate eta factors. However, in contrast with the behaviour of a metallic-type material where the plastic deformation characteristics are not associated with a length dimension, with an elastic softening material that exhibits cohesive zone characteristics, there is an extra length dimension associated with the softening. This means that, unlike the case of a metal, J cannot be determined for all loading levels using a single specimen. Nevertheless it is shown that, with an elastic softening material, the single specimen procedure can in principle be used at small loading levels, i.e. where the cohesive zone is only partially developed, so as to give the initial portion of the p− v softening curve.

Non-proportionally scaled lefm components and the scaling of elastic eta factors

Non-proportionally scaled lefm components and the scaling of elastic eta factors