Proposed Engineering Approach Research Articles

An engineering approach for the prediction of fatigue damage in the part load regime

Due to the volatile electricity received from solar and wind power plants, the energy market requires highly variable hydropower machines which are able to cope with fast changes of their operating regimes. With the need for flexible operation, Francis runners are exposed to various operating conditions outside the traditional operating range. Hence, the runners must be specifically designed for long time part load operation to meet hydraulic and structural requirements. Therefore, it is inevitable to have a reliable but also practical engineering approach in the design phase of the projects in order to ensure sufficient fatigue life of the Francis runners. Deep part load operation mainly consists of stochastic loads acting on the runner blades. Previous publications show that it is reasonable to normalize the Rainflow matrix of stress amplitudes to represent the characteristic behaviour at deep part load operation. Hence, it is feasible to utilize the normalized Rainflow matrix to predict the fatigue damage of Francis runner designs without prototype measurements. Within this paper, a scaling method to derive project specific fatigue results for deep part load is introduced and subsequently validated through an intercomparison of available strain gauge measurement data and prediction. Based on the results, the accuracy of the proposed engineering approach and possible impacts of different boundary conditions are discussed.

Modelling non-ideal detonations in commercial explosives

Highly non-ideal explosives usually react expressively below their ideal velocities of detonation. In these cases, dimensional effects and product heterogeneities become important to proper model their respective detonation state. Although Direct Numerical Simulation (DNS) techniques can provide a complete and exact solution for this problem, their actual computation cost are still not practical for industrial applications. In order to minimize these constrains, a simplified two-dimensional steady non-ideal detonation model for cylindrical stick explosives is presented. Based on an ellipsoidal shock shape approach (ESSA), the proposed model combines the quasione-dimensional theory for the axial flow solution with the unconfined sonic post-flow conditions at the edge of the explosive. Once calibrated, the model offers the possibility to predict the non-ideal detonation state for any charge diameter, resulting in a full mapping of the diameter-effect curve of the explosive. In addition, the effect of the inert confiner on the detonation flow is calculated by coupling a mechanistic confinement approach with the ESSA model. Thus, the proposed engineering approach is used to model the main properties of one of the most common ammonium nitrate-based explosive used in mining and quarrying industries, including the complete axial flow solution.

A High-Temperature Quenching Reactor

This article reports results of modeling, design, and experimental investigation of a heat exchanger to be used downstream of a radio frequency plasma torch for a variety of applications. A heat exchanger is designed for a plasma generator with thermal power of 30 kW and a maximum air plasma temperature of about 6000 K. The design can also be scaled to accommodate higher power plasma generators. The proposed engineering approach is double stage quenching of intermediate and unstable products from plasma chemical reactions. The design can be used in various technological processes, particularly for fixing atmospheric nitrogen and obtaining nitrogen oxides.

Engineering Simulation of Market Value of Construction Materials

Material resources are one of the main elements of the construction cost estimate. The nomenclature of material resources includes a large number of items. It is impossible to objectively estimate the construction cost, capital construction, and maintenance works without carrying out monitoring of the prices of constructional resources and accounting for these data in estimates. The purpose of the present study consists in developing an engineering approach to the simulation of pricing in the construction materials’ market. To achieve this purpose, we use mathematical statistics methods such as linear regression and autoregressive integrated moving average, as well as machine learning methods, namely gradient boosting and recurrent neural networks. In consequence of this work, we proposed a scheme to store statistical information based on the SpagoBI business intelligence platform, as well as designed hybrid intelligent predictive model, which allowed automating the engineering approach to the prediction of prices and objectifying advanced analytics of the construction materials’ market. The proposed engineering approach allows predicting the dynamics of the construction materials’ market segments when managing the construction cost at the level of enterprise and the region that will enable adequate decision- making in the course of investment projects development.

Probabilistic fatigue crack growth assessment of Al 7075-T6 aerospace component

In this paper, an engineering approach of fatigue crack growth mechanism of Al 7075-T6 aerospace component is proposed. The proposed approach was implemented by coupling of Extended Finite Element Method (XFEM), Residual Corrected Stress intensity Factor (RC-SIF) and Monte Carlo simulation (MCS) method. Particular focus was put on considering the effect of material dispersions and the residual stress distribution near the crack tip for evaluating FCG life of cracked attachment lug. Lemaitre-Chaboche's model has been used to describe material behavior. The iso-probabilistic a-N curves corresponding to5%, 50% and 95% of reliability are determined. The reliability of the proposed engineering approach is verified through a comparison with experimental FCG life data.

An Engineering Predictive Approach of Kitagawa-Takahashi Diagrams of defective A356-T6 alloy considering SDAS dispersion

This attempt proposes a probabilistic framework to predict the High Cycle Fatigue (HCF) behavior of A356-T6 aluminum alloy considering the modifications introduced by the microstructure heterogeneities (the Secondary Dendrite Arming Spacing (SDAS)). The proposed approach was carried out by coupling of Finite Element (FE) simulation, Defect Stress Gradient (DSG) criterion and Monte Carlo (MCS) method. A 3D FE model representing the defective material, was implemented to evaluate the A356 HCF response under different load conditions. Lemaitre-Chaboche's model has been usedto describethe material behavior. The iso-probabilistic Kitagawa-Takahashi corresponding to5%, 50% and 95% of reliability are determined.The reliability of the proposed engineering approach is verified through a comparison with experimental HCF data.

A transferability approach for reducing excessive conservatism in fracture assessments

A source of uncertainty and conservatism in structural integrity assessments is the value of fracture toughness (Kmat) that is used. For conservative results, the value of Kmat is commonly derived from deeply cracked specimens, such as standard compact tension specimens, C(T). High constraint conditions near the crack tip are ensured and this corresponds to lower-bound toughness values independent of specimen size and geometry. However, the local stress fields in single edge notched tension, SE(T), specimens and pipes, for example, are known to be less severe than those at the tip of a deep sharp crack, resulting in an increased capacity to sustain load and higher toughness. Similar behaviour is expected when assessing non-sharp defects (e.g., pits, gouges, dents). The constraint loss or the notch effect produce a relaxation in the triaxial stress field in comparison to the severe stress fields present at deeply sharp cracked specimens. A methodology providing a simple procedure to evaluate the suitability of the use of a higher fracture toughness to reduce excessive conservatism is then required. This study uses a two-parameter fracture mechanics approach (J-Q) to quantify the level of constraint in a component (e.g. a pipe with a surface crack) and in fracture test specimens, i.e. single edge tension [SE(T]), standard compact tension [C(T)] and notched compact tension [C(T)ρ] specimens. The ability of the structure to resist fracture is given by the fracture toughness of the test specimen with a similar J-Q response. Fracture toughness values for different specimens have been obtained from tearing resistance curves (J-R curves) constructed by means of a virtual testing framework. The proposed engineering approach is used as a platform to perform more accurate fracture assessments by the use of a ductile fracture model that informs a classical fracture mechanics approach (J-Q) by incorporating more fundamental understanding of the driving forces and the role of the geometry and loading conditions.

Improvement of free fatty acid production using a mutant acyl-CoA thioesterase I with high specific activity in Escherichia coli.

BackgroundMicrobial production of oleochemicals has been actively studied in the last decade. Free fatty acids (FFAs) could be converted into a variety of molecules such as industrial products, consumer products, and fuels. FFAs have been produced in metabolically engineered Escherichia coli cells expressing a signal sequence-deficient acyl-CoA thioesterase I (‘TesA). Nonetheless, increasing the expression level of ‘TesA seems not to be an appropriate approach to scale up FFA production because a certain ratio of each component including fatty acid synthase and ‘TesA is required for optimal production of FFAs. Thus, the catalytic activity of ‘TesA should be rationally engineered instead of merely increasing the enzyme expression level to enhance the production of FFAs.ResultsIn this study, we constructed a sensing system with a fusion protein of tetracycline resistance protein and red fluorescent protein (RFP) under the control of a FadR-responsive promoter to select the desired mutants. Fatty acid-dependent growth and RFP expression allowed for selection of FFA-overproducing cells. A ‘TesA mutant that produces a twofold greater amount of FFAs was isolated from an error-prone PCR mutant library of E. coli ‘TesA. Its kinetic analysis revealed that substitution of Arg64 with Cys64 in the enzyme causes an approximately twofold increase in catalytic activity.ConclusionsBecause the expression of ‘TesA in E. coli for the production of oleochemicals is almost an indispensable process, the proposed engineering approach has a potential to enhance the production of oleochemicals. The use of the catalytically active mutant ‘TesAR64C should accelerate the manufacture of FFA-derived chemicals and fuels.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0622-y) contains supplementary material, which is available to authorized users.

Ductile fracture modelling and J-Q fracture mechanics: a constraint based fracture assessment approach

The reduced state of stress triaxiality observed in shallow cracked components allows an increased capacity to resist crack propagation compared to that observed in deeply cracked specimens. This may be regarded as a higher fracture toughness value which allows a reduction in the inherent conservatism when assessing components in low constraint conditions. This study uses a two-parameter fracture mechanics approach (JQ) to quantify the level of constraint in a component (e.g. a pipe with a surface crack) and in fracture test specimens, i.e. single edge tension [SE(T]) and compact tension [C(T)] specimens, of varying constraint level. The level of constraint of the component is matched to a specific test specimen and therefore the ability of the structure to resist fracture is given by the fracture toughness of the test specimen with a similar J-Q response. Fracture toughness values for different specimens have been obtained from tearing resistance curves (J-R curves) constructed by means of a virtual testing framework. The proposed engineering approach shows that the combination of a local approach and two-parameter fracture mechanics can be used as a platform to perform more accurate fracture assessments of defects in structures with reduced constraint conditions. KEYWORDS. Crack tip constraint; Ductile fracture modelling; J-Q fracture mechanics.

Translation of statechart agents into a BDI framework for MAS engineering

In the agent-oriented computing area, different programming paradigms have been to date proposed to design and implement multi-agent systems (MAS). Among them, the Belief-Desire-Intention (BDI) and Statecharts-based models have emerged as they effectively support the definition of rational and protocol-oriented agent behaviors, respectively. In this paper, we investigate the translation between such models by using two available agent modeling languages: PROFETA, which is based on the BDI agent model, and the agent-oriented Distilled StateCharts (DSC) formalism, which allows modeling agent behaviors based on Statecharts-like state machines. In particular, we propose a mapping from DSC to PROFETA that can enable visual programming of PROFETA programs to facilitate the development of PROFETA-based autonomous systems. A case-study is also developed to exemplify the proposed engineering approach.

Quality of consumer experience data mining for mobile multimedia communication networks: learning from measurements campaign

This paper presents an experimental approach of the major data mining algorithms which can be applied to the quality prediction of provided services by contemporary mobile communication networks. Recent developments in performance evaluation of rollout mobile communication networks are based on drive-test measurement campaigns as well as on network monitoring and management systems. In addition, large measurement databases as well as data warehouses are created, updated and used for a drill-down statistics analysis. An empirical comparison of modern data mining methods for quality prediction and estimation of speech and video telephony services is presented. Learning prediction models are constructed from live network measurements which have been previously collected by experimental equipment during measurement campaigns. Practically and summing up, the proposed engineering approach is general and is applicable to various radio access network technologies during planning and optimisation phases.

Materials and Engineering Design for Human Performance and Protection in Extreme Hot Conditions

The level of protective material performance attributes are well defined and highly regulated, however the attributes related to the thermo physiological comfort of materials are not. In this chapter, the application of new materials to firefighting protective clothing systems used in extreme heat is addressed, with a focus on thermo physiological comfort. The new generation of protective textile materials and their structures are evaluated through use of both objective laboratory testing and mathematical modeling methods. In addition, 3D body imaging technology is utilized to demonstrate a method of assessing the fit of protective garments and its potential impact on the thermal status of the wearer. The proposed engineering approach could be used in other areas where the balance between clothing performance and wear comfort is critical, e.g. sport, work wear etc.

An enhanced engineering perspective of global climate systems and statistical formulation of terrestrial CO2 exchanges

This paper designs a comprehensive approach based on the engineering machine/system concept, to model, analyze, and assess the level of carbon dioxide (CO2) exchange between the atmosphere and terrestrial ecosystems, which is an important factor in understanding changes in global climate. The focus of this article is on spatial patterns and on the correlation between levels of CO2 fluxes and a variety of influencing factors in eco-environments. The engineering/machine concept used is a system protocol that includes the sequential activities of design, test, observe, and model. This concept is applied to explicitly include various influencing factors and interactions associated with CO2 fluxes. To formulate effective models of a large and complex climate system, this article introduces a modeling technique that will be referred to as stochastic filtering analysis of variance (SF-ANOVA). The CO2 flux data observed from some sites of AmeriFlux are used to illustrate and validate the analysis, prediction, and globalization capabilities of the proposed engineering approach and the SF-ANOVA technique. The SF-ANOVA modeling approach was compared to stepwise regression, ridge regression, and neural networks. The comparison indicated that the proposed approach is a valid and effective tool with similar accuracy and less complexity than the other procedures.

Theoretical and experimental study of electron-optical systems in low-energy wide-aperture electron accelerators

A large-area electron accelerator based on filament cathodes that operates in a continuous mode is described. The results of calculations of electron-optical systems of triode- and tetrode-type accelerators in accordance with the proposed engineering approach are considered, and experimental and calculated parameters of the accelerator are compared.

FEM modelling of faults occurred in buried power cables due to the removal of tree roots

AbstractAn engineering approach to numerical modelling of power cable heating due to a line‐to‐earth short‐circuit caused by previous mechanical damages of a cable sheath and insulation is proposed in this paper. Nonlinearity of the finite element model is based on the soil thermal conductivity and heat sources as functions of temperature and time. The nonlinear transient analysis is applied to an authentic example of line‐to‐earth short‐circuit caused by a mechanical damage of the cable sheath and insulation that has arisen during the previous removal of tree roots. The represented fault occurred on 14 November 2007 in a buried 0.4 kV cable line installed in the city of Bijelo Polje, Republic of Montenegro. Also, this paper outlines a proposition of a technical report prescribing procedures for the removal of tree roots from the soil surrounding cables and for laying power cables nearby high vegetation. The proposed engineering approach is applicable to power cables of all voltage levels laid in soils with changeable moisture content. Copyright © 2009 John Wiley & Sons, Ltd.

The Creep Line-Spring Model. Estimates of Creep Fracture Parameters for Surface-Cracked Plates.

Extending the engineering approach for elastic-plastic fracture analysis(EPRI approach)to creep crack analysis, in this study we examine an engineering approach for estimating the displacement, crack-tip J and C integrals under nonsteady creep conditions. On the bases of the proposed engineering approach and the elastic-plastic line-spring method, a creep line-spring method is proposed and the fundamental equations are established. The creep line-spring method is used for estimating the creep fracture parameters for three-dimensional creep cracks. In order to check its accuracy, several surface-cracked plates under uniform tension are analyzed by the creep line-spring method and the three-dimensional finite-element method. The numerical results show that the creep line-spring method is in good agreement with the finite-element method and has the same accuracy as the common elastic-plastic line-spring method.