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International audience; Using cracked pipes design standards and finite element analysis, the limit load analysis for pipes containing surface cracks was determined. The study was performed on five pipes of different diameters with a constant crack length and depth. The crack geometry is a semi-elliptical surface crack. The cracked pipes are subjected to internal pressures which are obtained from formulas of cracked pipes design standards. Due to the ductile behavior of polyethylene pipes, the failure occurs when the critical stress reaches a value equal to the ultimate tensile strength multiplied by a constraint factor. In this work, the constraint factor was calculated and its evolution with the pipe diameter was analyzed. Three different definitions of a constraint factor based on global or local approaches were also compared, so that a new failure criterion can be obtained. The new failure criterion makes the prediction of the pipe residual life possible which, in turn, facilitates a systematic approach to maintenance and replacement of pipes.

Power transformers are key components in the power grid, so it is of great importance to protect them from an unplanned outage. With the increase of social electricity consumption, the overload accidents of transformer have become increasingly frequent. In order to avoid the overload accidents, we investigate the loading capacity of transformer based on temperature rise characteristics. Firstly, considering the influence of sunshine radiation, we establish the improved thermal model. Because the DC resistance of winding and oil viscosity change with oil temperature, the algorithms of load loss and thermal resistance are modified to improve the calculation accuracy of hot-spot temperature (HST). Compared with conventional IEC standard method, the relative error of the improved model of hotspot temperature is reduced by about 2.5%. Further, the constraints of loading capacity for transformer are studied. Taken temperature rise characteristics with load current and the loading constraint factors of transformer into account, the evaluation model for loading capacity of transformer is proposed. The results show that the main constraint factor is the relative life loss of transformer under the normal periodic load; the main constraint factor is the capacity of auxiliary equipment of transformer under the long-term emergency load. The capacity of short-term emergency load is not only limited by the top-oil temperature and hot-spot temperature, but also affected by the initial load rate of transformer and the ambient temperature.

The quality of transportation service it’s a main factor to increase the level of economic and social in Sarawak. By increasing the system may buzz-up all sector and may contribute the benefit to the community. This research will be conducting in four selected locations consist of Sibu, Miri, Bintulu and Kuching. The reason to choose these four locations it’s because of the role that each location plays in contributing to the economic sector in Sarawak state itself. Methodology to be used to conduct this research its quantitative method. Where, 300 set of questionnaire to be distributing to the stated locations to get a perception on the concept of sustainable transportation among respondents. Questionnaire distributing to those who has knowledge towards sustainable transportation and it’s limited to those who have experience in construction sector only. The objectives of this research it’s to investigate the construction player’s perception towards sustainability transportation in Kuching, Miri, Bintulu and Sibu; and to identify the barriers factor to implementing this concept. Expecting distribution from this research it’s to create awareness by implementing this concept it’s beneficial to the routine activities as well as can generate and increase the Sarawak’s economic sector.

The purpose of this study is to examine the constraint factors of the e-learning learning system. This type of research is literature review research with a descriptive approach. The results of the study obtained regarding the constraint factors in the e-learning learning system include; quota and network/internet connection, equipment used, learning facilities, understanding of course management in e-learning, limited time for managing e-learning, lack of commitment from schools and teachers regarding the development of e-learning learning, funds needed for e-learning implementation still limited, school leadership policies in allocating funds for the development of learning media, long loading times for information or films, mentoring time by parents, teachers' technological abilities, costs, psychologically face-to-face directly affect the level of understanding

Cooperative localization of the connected vehicles is significant for many advanced intelligent transportation system (ITS) applications. Vehicle-to-vehicle communication using dedicated short-range communication (DSRC) has great potential to enhance global navigation satellite systems (GNSSs) for the capability of cooperative localization. In the integration of DSRC and GNSS, the tolerance against the unknown and time-varying observation conditions is a key factor to fulfill the requirements of several specific ITS applications. Under a GNSS/DSRC integrated architecture for cooperative localization, a novel robust cubature Kalman filter (CKF) is proposed in this paper to improve the performance of the data fusion under uncertain sensor observation environments. In the proposed solution, the structure of the standard CKF is enhanced using the Huber M-estimation technique, in which the original measurement update in the CKF is modified considering the probable anomalies in state estimation. Furthermore, based on the investigation of the adjustment effect from the constraint factor, an adaptive strategy for this parameter is introduced to optimize the performance comprehensively. The proposed method is validated using a specific simulation system. Results of experiment and simulations demonstrate the capability of improving the robustness and adaptive performance over the original filters under the unknown operation conditions.

The strip-yield model and the Generalized Willenborg model from the Nasgro 7.0 software have been applied to predict fatigue crack growth in an AlMgSi aluminium alloy under constant amplitude loading and single peak overloads. The model performance has been evaluated based on the comparison between the predicted and the experimentally observed crack growth behaviours. The crack propagation tests have been performed in agreement with ASTM E647 standard, using Middle-Tension, M( T ), specimens under load control conditions. The strip-yield model enables the reproduction of the retardation behaviour following a single overload. Generally, the predictions are in agreement with the typical experimentally observed crack growth rate response. A high effect of the constraint factor in the predictions by the strip-yield crack closure model is observed. The Generalized Willenborg model is always significantly more conservative than the strip-yield model. However, it is clear that more investigation is needed in order to clarify some assumptions.

This paper explores the prospect for achieving an equitable allocation of country-specific carbon dioxide emissions from the energy sector within the framework of the Cancun climate stability target, as represented by Representative Concentration Pathway 2.6. Three allocation principles are considered, with the primary one (Egalitarian) based on equal per capita emissions for all countries by 2050. The two secondary allocation principles, termed Emission-based and GDP-based, distribute allowable emissions according to cumulative historical emissions and cumulative historical GDP respectively. Neither of these two allocation principles can deliver equal per capita emissions by 2050. Only when a global average constraint factor is introduced, designed to enable countries with less than allowed global average per capita emissions in any year to increase their emissions to this level, can emissions parity (the Egalitarian principle) be achieved by 2050. Finally, it is argued that achieving the widespread agreement needed to achieve climate stability is likely to be difficult, given both the size of reductions needed, especially by high-emission countries, and the inadequacies of the technical fixes proposed.

International audience; The application of the concept of the representative strain is often used in the stress-strain curve determination from indentation test because it can significantly simplify the analysis of the indentation response. A new methodology for determining the representative strain for Vickers indentation is presented in this article. Following a procedure based on finite element simulations of indentation of elastoplastic materials, two representative strains are defined: the representative strain characteristic of the mean pressure and the representative strain characteristic of the Martens hardness or the indentation loading curvature. The results obtained from this methodology show that there is no universal value of representative strain independent of the mechanical parameters of materials indented by Vickers indentation. It is also shown that the representative strain, obtained by Vickers indentation is much lower when it is obtained from the relationship between the applied force and the penetration depth, F-h, rather than from the relationship between the applied force and the contact radius, F-a. The values of the calculated representative strains show that simultaneous measurement of relationships F-a and F-h make it possible to characterize the hardening law with two unknown parameters by Vickers indentation.

The extension of the available stress-based predictive models from uniaxial to multiaxial feature is uncertain due to the difficulty to justify the model transferability to the cases which involves complex deformation and fracture mechanisms. This paper presents a new approach to predict the creep rupture life of Grade 92 steel under multiaxial stress state as the case of notched bar samples using Kachanov's Continuum Damage Mechanics (CDM) model. Combining the CDM model with the concept of Hayhurst's representative stress and accounting two extreme conditions; fully dislocation-controlled and diffusion-controlled creep mechanisms provide the bounds for short- and long-term rupture data of notched bar up to 10,000 h. Although the CDM is scientifically relevant and fundamental in their approach, it is generally complex and contains too many variables. Therefore, it needs proper measurements or numerically intensive to make the model acceptable for industrial applications. Alternatively, the recent developed strain-based exponential-type predictive model which links globally uniform failure strain with a multiaxial constraint factor was employed with the intention to reduce the large number of CDM parameters. The approach is relatively simple yet reliable to be used for high temperature creep rupture assessment.

Fatigue damage is one of the most common failure modes of large-scale engineering equipment, especially the full-face tunnel boring machine with characteristics of a thick plate structure bearing strong impact load. It is difficult to predict the location and propagation life of crack of cutterhead under strong impact load. Unseasonal maintenance of equipment caused by inaccurate prediction of life cycle of cutterhead seriously affects the construction efficiency of the equipment and the life safety of the operators. Determining the crack location of tunnel boring machine cutterhead structure under strong impact load and predicting the crack propagation life are difficult scientific problems. To solve them, first, the location of the stress concentration of the cutterhead is determined by using finite element analysis method of statics. Second, prediction model for crack propagation life of tunnel boring machine cutterhead characteristic substructure based on time integration is built. And the test of crack growth of cutterhead characteristic substructure is performed. The feasibility and accuracy of the prediction model are verified by contrasting crack prediction models and the results of the test. Finally, the life prediction of tunnel boring machine cutterhead of water diversion project in Northwest Liaoning Province is carried out by using crack propagation model based on time integration. Results show that the maximum error of theoretical prediction and experimental results of crack propagation is 16%. So the feasibility of crack propagation model based on time integration in predicting the crack growth of cutterhead is verified. It is predicted that the tunnel boring machine cutterhead panel can work normally for 5.9 km under the condition of ultimate load. Building the crack propagation model considering the influence of plate thickness and strong impact load has important research value for improving the working efficiency of engineering equipment, prolonging service time, and improving the working safety.

To accurately predict damage behavior in engineering applications, it is important to investigate the three-dimensional (3D) stress state near a real crack border. Introducing the out-of-plane stress constraint factor T z , Guo and his colleagues derived out the 3D asymptotic fields near the tensile crack border in power law plastic ( Guo, 1993a, 1993b, 1995 ) and creeping solids ( Xiang et al., 2011 ). However, these theoretical solutions are presented in curves and too complicated for application. Here we formulize the 3D theoretical solutions into a set of empirical explicit formulae in the whole range of out-of-plane stress constraint from T z = 0 at plane stress state to T z = 0.5 at plane strain state. At the two limits of T z = 0 and 0.5, the empirical formulae degrade into the two dimensional (2D) HRR ( Hutchinson, 1968; Rice and Rosengren, 1968 ) or RR ( Riedel and Rice, 1980 ) solutions with high accuracy. Detailed finite element analyses are performed for cracked plates with finite thickness under power law plastic and creeping conditions to verify the formulation of the asymptotic crack border stress fields. It is shown that the in-plane stress components and stress triaxiality on the ligament ahead of the crack border can be efficiently predicted by the explicit formulae. We also investigate the dominance of the formulation of stress components in the whole forward sector to give a more convenient description for wide applications. Based on the formulation, we discuss the influence of both in-plane and out-of-plane constraints. Three-parameter descriptions, such as the J – T z – Q T description for plastic solids proposed by Guo (2000) and the C ( t )– T z – Q ∗ description for creeping solids proposed by Xiang et al. (2011) are evaluated based on comparison of the empirical formulae and 3D finite element results. The three-parameter descriptions are shown to be necessary and efficient under large scale yielding or extensive creeping conditions in the whole forward sector of cracked plates with finite thickness.

UWASNs are deployed in environments of sea and shallow water, which are composed of many nodes that communicate through acoustic wave. The preliminary problem in UWASNs different with on land WSNs is the severe demand of delay time constrain. It becomes a crucial problem that how to reduce unnecessary path that waste time. In this proposed paper, we present an energy efficient protocol with low delay time. Orient constraint factor is a constitute element of this proposed protocol, which instructs node how to select the next hop from neighbor nodes. The orient constrain factor is composed of the distances of source node, neighbor nodes and destination node (commonly pointed to sink node). Simulations show that this protocol can efficiently reduce the delay time and hold a high level of energy efficient.

As China's economy continues to develop, it has formed a long-term conflict between the people's cultural requirements and cultural productivity. Development of folk music culture of our country needs to reform and innovation to another level. There are still many problems in Folk Music Teaching in our country, such as backward teaching methods , improper specialty setting, they have became an important constraint factor for Folk Music teaching Development. Therefore, how to promote the deep reform of folk music teaching development from all aspects, is a problem that we and the whole China need serious consideration. This article will elaborate existing problems and corresponding measures from various aspects of the system of National Folk Teaching.

A complete three-parameter K–T–Tz description of the mixed-mode I/II three-dimensional (3D) crack-tip stress fields has been proposed, in which the stress intensity factor K, T-stress and out-of-plane constraint factor Tz around mix-mode I/II crack front in compact-tension-shear specimens are all the functions of the Poisson ratio v, thickness ratio zB and load angle φ. By fitting the numerical results with the least squares method, empirical formulae have been obtained to accurately describe the 3D distributions of the three parameters for the convenience of engineering applications, which can be used to characterize the 3D crack-tip stress fields completely and establish the three-parameter dominated stress fields.

Creep fracture of solids at high temperature is vital to applications of many advanced materials, but most of the previous works are performed within the frame of two-dimensional theory. By using the out-of-plane stress constraint factor T z , here we derive out three-dimensional asymptotic fields near the border of mode-I through-thickness cracks in power law creeping solids. It is found that the asymptotic fields near the crack border are dominated by both T z and C ( t ) integral. Detailed finite element analyses are carefully performed for single-edge cracked specimens and centre-cracked tension specimens to investigate the dominance of the asymptotic solution for the crack border fields. It is shown that the C ( t ) − T z description based on the obtained three-dimensional asymptotic solution can provide efficient prediction for the tensile stress ahead of the crack front under small scale creep condition. Under extensive creep conditions, a third parameter Q ∗ should be introduced to take into account of the loss in the in-plane constraint caused by in-plane geometries and loading configuration at extensive creeping, and a three-parameter C ( t ) − T z − Q ∗ description is proposed and proven to be efficient to predict the tensile stress on the ligament ahead of the crack for both specimens. Therefore, the two-parameter C ( t ) − T z and three-parameter C ( t ) − T z − Q ∗ descriptions can provide advanced theoretical basis for small and extensive creeping fracture assessments, respectively.

The concept of the T-stress as a local constraint factor has been extended to U-notch tip stress distribution as the effective T-stress. The effective T-stress has been estimated as the average value of the T-stress in the region corresponding to the effective (characteristic) distance ahead of the notch tip. The T-stress is evaluated by finite element method using the experimental load for crack initiation and computing the difference between principal stresses along ligament. A large range of critical effective T-stress values is investigated for different specimen configurations and notch aspect ratios. Crack stabilisation and crack bifurcation for fracture emanating from notches according to the critical effective T-stress is discussed. A model involving the influence of the critical effective T-stress on void growth for ductile failure in the vicinity of the notch tip has been proposed.

The present paper describes a method for evaluating the collapse load from the tension- and bending-displacement charts. The plastic constraint factor, the collapse load and the 0.2% proof strength all exceeded the upper bound solution. The two collapse mechanisms observed are tension and bending collapses. Interaction of tension and bending results in a larger collapse load than that obtained from evaluating photo-plastic fringe, especially under simultaneous tension and bending loadings. The maximum load yielded more easily the test collapse load than the two-elastic-slope method.

On the basis of agricultural recycling economy"s connotation, this paper constructs index system to comprehensively evaluate the development of agricultural recycling economy, which includes 4 classification indexes, namely, economic and social development, resource reduction and input, resource recycling and reutilization, and resource environment and security, altogether 16 operational indexes. Then, this paper assesses the development of agricultural recycling economy in Hebei from 2004 to 2013. The results show that the overall level of Hebei agricultural recycling economy increases gradually, which is mainly driven by the increase of agricultural output. Reduction of resource input is the major constraint factor; resource recycling level has been maintaining the same for years; agricultural resource environment and security are basically guaranteed.

The historical developments of the fracture mechanics from planar theory to threedimensional (3D) theory are reviewed. The two-dimensional (2D) theories of fracture mechanics have been developed perfectly in the past 80 years, and are suitable for some specific cases of engineering applications. However, in the complicated 3D world, the limitation of the 2D fracture theory has become evident with development of the structure toward complication and micromation. In the 1990’s, Guo has proposed the 3D fracture theory with a 3D constraint factor based on the deformation theory and energy theory. The proposed 3D theory can predict accurately the fracture problems for practical and complicated engineering structures with defects, by integrating the 3D theory of fatigue, which has been developed to unify fatigue and fracture. Our efforts to develop the 3D fracture mechanics and the unified theory of 3D fatigue and fracture are summarized, and perspectives for future efforts are outlined.

“Plasticity-induced crack closure” phenomenon is the leading mechanism of different effects (R-ratio, overload retardation, … ) acting on crack growth rate in many metallic materials. Experimental tests are carried out to quantify the physical phenomenon, while Strip-Yield analytical models have been developed for predicting life of components. In the present work, an additional module to be applied to a Strip-Yield model is proposed in order to derive the strains near the crack tip. Particularly, the module is based on the Westergaard’s elastic complex potential. The presented algorithm allowed us to obtain the correlation between “local compliance” experimental results and the corresponding Strip-Yield analyses. This method can be taken as a semi-analytical procedure for calibrating the constraint factor, i.e., the most delicate parameter for Strip-Yield models.

Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks, near-threshold growth behavior of large cracks at constant Tirade/ decreasing ΔK and constant K max /decreasing AK, respectively, for 9310 steel. The results showed that a pronounced small-crack effect was not observed even at R = -1, small cracks initiated by a slip mechanism at strong slip sites. Worst-case near-threshold testing results for large cracks under several K max values showed that an effect of K max on the near-threshold behavior does not exist in the present investigation. A worst-case near-threshold test for a large crack, i.e. constant K max /decreasing AK test, can give a conservative prediction of growth behavior of naturally initiated small cracks. Using the worst-case near-threshold data for a large crack and crack-tip constraint factor equations defined in the paper, Newman's total fatigue-life prediction method was improved. The fatigue lives predicted by the improved method were in reasonable agreement with the experiments. A three-dimensional (3D) weight function method was used to calculate stress-intensity factors for a surface crack at a notch of the present SENTspecimen (with r/w = 1/8) by using a finite-element reference solution. The results were verified by limited finite-element solutions, and agreed well with those calculated by Newman's stress-intensity factor equations when the stress concentration factor of the present specimen was used in the equations.

In the present paper two methods are introduced to estimate the tensile properties of welded joints. The studies indicate that single-edge precracked three-point bend specimen tests can be successfully used to estimate the local yield strength of material sampled by crack tip in welded joints. The constraint factor of the specimens may be experimentally calibrated by weld metal or base metal. Moreover, microshear tests can be conveniently used to estimate the ultimate tensile strength and tensile yield strength of materials in each zone of welded joints, and the cost of such tests is low. The tensile yield strength and ultimate tensile strength estimated by either method will play an important role in fracture mechanics tests of welded joints and integrity assessment of welded structures. Furthermore, the present studies on the welded joints of Welten 80C pressure vessel steel and API X65 welded pipe steel indicate that the methods for estimating the tensile properties of welded joints are successful.

A series of laboratory experiments on smooth and side-grooved compact specimens, as well as plates under tension with surface flaws, has been reevaluated by means of three-dimensional elastic-plastic finite-element analyses. Particular emphasis is laid on the calculation of the local crack-tip loading parameter, J, and of the local constraint factor, q. These parameters are correlated with experimental findings concerning initiation and stable crack propagation. A first-guess correlation between q and the slope of J(Δa) curves is established.

Fracture mechanics, in terms of crack propagation, is one of the most popular approaches for life prediction of components and structures subjected to fatigue loads. Experimental tests (as an example for a structural steel see Fig. 1) are carried out in order to quantify crack growth rates and thresholds.

The purpose of this study was to assess barriers to sports and recreation participation among men and women aged 18-40 years in three communities in Botswana. Four hundred and thirty-two respondents (201 women and 231 men) participated in the study. A questionnaire was used to assess barriers to sports and recreation participation among men and women of the three communities in five barrier categories: aptitude, socio-economic, socio-cultural, awareness of facilities and facility constraints. Descriptive statistics were used to analyse the data. T-test was used to determine the significant difference between genders in each respective constraint factor. Analysis of variance was used to test the variability for each gender. A frequency table was generated to reflect the rate of constraint factors among men and women in three communities in Botswana. The results showed that men and women of the three communities were constrained by socio-economic and facility barriers. Analysis of variance showed a significant difference among women of the three communities in the 3 barrier categories (aptitude, socio-economic and awareness of facilities), while no significant differences were found among men. Strategies that limit the adverse impact of socio-economic and facility constraints were suggested for the three communities. Key Words: Communities, barriers, constraints, leisure, recreation, sport, Botswana. AJPHERD Vol.10(4) 2004:306-316

The compressive behaviour of paper honeycombs is studied by means of an experimental analysis. Experiment results show how geometry aspects of hexagonal paper honeycombs,e.g. the height of paper honeycomb,the thickness and length of honeycomb cell-wall,the drawing ratio of hexagonal honeycomb,affect the compressive properties of the paper honeycombs. It is in good agreement with the theory model. The constraint factor K of the critical buckling stress is mainly determined by the length of honeycomb cell-wall. It can be described as K=1.54 for B type paper honeycombs and K=3.32 for D type paper honeycombs. The plateau stress is the power exponent function of the thickness to length ratio of honeycomb cell-wall,and the experiment results show that the constant is 13.2 and the power exponent is 1.77. The research results can be used to characterize and improve efficiently the compressive properties of paper honeycombs.

Lately in the connection of beam knees, welding has been taking the place of rivetting. But as the basis of the design of their type or size, we have no theoretical standard but only the customary practices or experiences. So there are some questions about the propriety of the plane application of the type and size of the rivetted knees to the welded ones.As the first step of the research of this problem, the author studied here about the so-called “constraint factor” of the welded beam knees in the elastic range.After the theoretical analysis of the “constraint factor” in an idealized condition, the author has looked experimentally for its value “β” of simple welded knees of common type, from the bending tests of four structural specimens having different sizes of knee, and gained β_??_0.85 regardless of their sizes, which is pretty larger value than usualy accepted.From these results it is concluded that, the welded knees are more effective to the strength and weight saving than the rivetted ones, and we can reduce the dimensions of the knees or stiffeners from the present values, and that we shall be able to improve the type of the knees to more effective one suitable to the welded knees.

Three dimensional elastic body fracture analysis, considering lateral constraint factor contour plots

Effect of dimensional parameters on the notch toughness values of a HSLA steel has been studied. The notch mouth opening displacement, notch root contraction and load point displacements were measured experimentally during the test. Experimental data obtained from SEN three point bend specimens showed that the toughness as indicated by NTOD and J increases with increasing width, thickness, notch root radius and decreasing notch depth to width ratio. The yielding constraint factor, M and the general yielding constraint, m appeared to lie in the range of 1.3 to 2.3 in the various notched specimens investigated. The sizes of dimple in the notch or crack tip region seem to be largely influenced by the stress state prevailing at the crack tip, and the dimple size is found to be increasing with increasing triaxiality level. The state of stress at notch tip (ρ ≃ 0.2 mm) is found to be mixed type and at the crack tip it is triaxial, as indicated by σm/≃ values (≃ 0.5~1.2 for ρ=0.2 mm and about 3.2 for ρ≃0).

In this communication the I-similarity of fatigue fracture in stage II and cyclic fracture toughness criterion KIS is proposed. The parameter KIS corresponds to the threshold δK = KIS, at which the self-similar elastic-plastic transition at I = I* is effected under maximum plastic strain constraint factor.

The effect of defects on the entity of the fatigue limit is nowadays well known and is demonstrated to be equivalent to the nonpropagating condition of short cracks. The influence of constraint at the defect tip has been addressed in the present paper considering a mild steel whose mechanical behavior has been experimentally determined together with the propagation threshold values for long cracks. The activity has first dealt with the determination of the Kitagawa diagram by means of fatigue limit tests using specimens containing micro-notches with different shapes (drilled holes and narrow slits). Experimental results showed a significant influence of the defect shape on the fatigue limit and thresholds. In order to understand the reasons, defects have then been analyzed by elasto-plastic FEM analyses. Computational results have confirmed a significant difference in the global constraint factor at the crack tip between round and narrow defects.

The sectional thickness of plate-like components has a significant influence on the fatigue and fracture properties. This effect is primarily due to the differences in the through-the-thickness stresses prevailing at the tip of a crack in a finite-thickness plate or shell. Characterization of this effect to date has remained largely empirical. The current paper presents new analytical results for CTOD for the through-the-thickness crack in infinite plates with various thicknesses. These results are based on a recently developed solution for an edge dislocation in infinite plate of arbitrary thickness. The analytical predictions of the CTOD and the constraint factor are compared with the three-dimensional FE results. It is shown that the analytical and the numerical results are in good agreement when the numerical calculations are not affected by the size of the FE mesh and by the boundaries of the FE model.