Search

For security requirements, no fatigue failure of axles is admitted in railway industry. Design process of axles must ensure that there is no crack initiation during its life. Maintenance inspections guarantee that no defect initiates critical propagation of fatigue cracks. In order to remove surface defects, wheel grinding is realized during maintenance task. The present paper addresses a lifetime comparative study of an axle with and without grinding operation. The goal is to investigate the influence of the grinding parameters on the lifetime of axle. In the first part of the paper, the context of maintenance of railway axle is briefly described and the grinding process is presented. The grinding process modifies the roughness, the microstructure of the surface and induces residual stresses: some experimental results are presented. In the second part, the case of a ground axle is considered without defect. A study of the effect of the grinding process on the lifetime of fatigue samples is presented. In the third part, the case of a ground axle is considered with defects. In this case, a study of the effect of the grinding process on the lifetime is presented for different types of defects. Fatigue tests results on specimens are presented. Numerical simulations results for lifetime evaluation are also presented. [ABSTRACT FROM AUTHOR]

Numerical simulation is more and more used in automotive industry to reduce design time and cost. Moreover, for high performance engines, the development of cylinder heads requires well known and adapted materials to ensure their reliability. The estimation of adapted fatigue criteria based on few experiments is thus an important challenge: to obtain more predictive model on more complex mechanical phenomena. This paper describes the methodology adopted by Renault to estimate fatigue life of a new aluminum-silicon alloy. A low copper aluminum-silicon alloy has been developed for a new generation of cylinder heads. Those kinds of alloys provide a good compromise between the two main failure modes encountered for cylinder heads: high cycle fatigue of water jacket and low cycle fatigue of fire deck. However, those materials are subjected to thermal ageing that can affect mechanical behavior, such as yield stress and hardening, but also fatigue mechanisms at higher temperatures. This article presents first the selected constitutive equations that introduce thermal ageing effect in a cyclic elasto-viscoplastic model. The low cycle fatigue criterion is then calibrated on the relevant database, which includes isothermal and non-isothermal tests. The fatigue criterion is a specific version of a classical model previously developed at Onera. The critical variables for the fatigue part are the stress amplitude and the mean stress, both of them being normalized by an ultimate stress which depends on temperature and ageing state. Finally, the constitutive and damage models have been applied on 3D cylinder head numerical analysis. The paper proposes a brief comparison of those results with more classical simulations made on cylinder heads and highlights the perspectives offered by this new aluminum-silicon alloy. [ABSTRACT FROM AUTHOR]

As is known to all, the cable corridor is one of the most important projects in China. In this paper, the fire temperature field distribution of L-type corridor under the condition of different fire source location height is studied through numerical simulation. When the heat release rate of the ignition source is 250 kW and longitudinal wind speed is fixed 0.5 meters per second, the temperature changing rule of the inflection point of L-type corridor is discussed. Furthermore, the temperature prediction formula is established based on the height of the ignition source at different stages according to the fire situation. Combined with the results of these studies, the paper shows that there is obvious "smoke accumulation effect" in L-type cable corridor. [ABSTRACT FROM AUTHOR]

Due to located underground and relatively closed space, casualties would be caused if fire happens in subway station. The effect of suction velocity on the smoke control effect are analyzed to determine the optimal exhaust velocity for the safety evacuation in a subway station. In this paper, a full-scale experiment was conducted to obtain the effect of smoke exhaust system in a subway platform fire. Numerical simulation on smoke control effect was also conducted by Fire Dynamics Simulator software (FDS). The appropriate parameters were verified by comparing the simulation results with the experimental results. It has been found that the optimal exhaust velocity at dampers for a platform fire was about 8m/s. The results in the paper may serve as a useful reference for the smoke control design in case of subway platform fires. [ABSTRACT FROM AUTHOR]

In this paper, hot smoke test was carried out in the atrium of 60m high in Shanghai Tower, the law of fire smoke movement and smoke control effect has been studied under different fire release rate and different ventilation conditions. In this paper, the Influence of different air supply volume on mechanical smoke exhaust in the atrium of Shanghai Tower has also been studied by numerical simulation. The results showed that: in the tall atrium, smoke rise rapidly with the speed of 2-3 m/s because of “chimney effect”; Because of the “thermal barrier effect”, when the fire power is small, the smoke tends to subside and cannot be effectively discharged; When air supply volume is 50% of smoke exhaust, it is beneficial to exhaust smoke. [ABSTRACT FROM AUTHOR]

The paper presents the main theoretical backgrounds and application of FE program ATENA to simulation of severe accident in nuclear structures. The software was developed by Cervenka Consulting, Prague, Czech Republic with the aim to offer a tool for numerical simulation of concrete structures subjected to actions in service, ultimate as well as extreme limit states due to mechanical as well as physical effects. Nonlinear behavior of concrete is modeled by theories of damage and plastic flow [1]. Paper outlines the basic features of the used material model. It demonstrates the model accuracy on results from recent blind prediction competitions [2]. In the last section, it shows examples of simulations of severe accidents scenarios in nuclear power plants structures [4]. [ABSTRACT FROM AUTHOR]

In metal forming processes, friction between tool and workpiece is an important parameter influencing the material flow, surface quality and tool life. Theoretical models of friction in metal forming are based on analysis of the real contact area in tool-workpiece interfaces. Several research groups have studied and modelled the asperity flattening of workpiece material against tool surface in dry contact or in contact interfaces with only thin layers of lubrication with the aim to improve understanding of friction in metal forming. This paper aims at giving a review of the most important contributions during the last 80 years covering experimental techniques, upper bound solutions, slip-line analyses and numerical simulations. Each of the contributions shed light on the importance of the real contact area and the influencing parameters including the material properties, surface conditions, normal pressure, sliding length and speed, temperature changes, friction on the flattened plateaus and deformation of the underlying material. The review illustrates the development in the understanding of asperity flattening and the methods of analysis. Finally, the present paper discusses the necessary future work in order to advance further in modelling of real contact area in relation to implementation of frictional conditions existing finite element codes for simulation of metal forming processes. [ABSTRACT FROM AUTHOR]

Large continuous casting billet always contain void defects which may adversely affect the mechanical properties and safe performance of final products. The void must be completely eliminated during hot forging process. In this paper, different types of void defects in large billet are showed and analyzed. It is found that the voids have different geometry, orientations and positions. Using finite element (FE) software DEFORM 3D, a FE model was developed to investigate the void closure in large continuous casting billet during multi-pass stretching process. The wide die heavy blow forging (WHF) method which has been proved to be an effective method to eliminate void defects was adapted during the stretching process. Then, the stretching processes of various sizes of billets which contained different kinds of void defects were simulated. The closure processes of different kinds of void defects were obtained. The critical forging ratio for large billets from Φ500mm to Φ1000mm was obtained as 2.40. In addition, the void closure evaluation index is analyzed, and the critical value for the closure of all voids is 0.87. The work in this paper is verified by actual production, which illustrates that the simulation results and the proposed criterion in this research are reliable. [ABSTRACT FROM AUTHOR]

Development of two approaches for creation of digital microstructure representations of sintered porous metals for further numerical simulations is the goal of the paper. Initially, an approach based on series of exact replicas of real 2D microstructures processed by image analysis and reconstruction algorithms was proposed. Thus, developed in-house code for 3D reconstruction of 2D images obtained from optical microscopy is briefly described within the paper. Advantages and limitations of the approach are discussed in that part. Then, to facilitate the process of generation of digital models, another solution, based on synthetic microstructures, was developed with discrete numerical method and is presented within the work. Two algorithms based on the Cellular Automata (CA) technique were developed and implemented. Description of major models assumption including generation of computational domains, cells states, boundary conditions and finally transition rules is presented for the proposed CA model. Obtained digital microstructure models are eventually subjected to numerical simulation by means of finite element tool to highlight capabilities offered by synthetic microstructures in evaluation of local material behavior. [ABSTRACT FROM AUTHOR]

Toothing of bevel gear is a crucial operation for the automobile industry. To achieve the required performance characteristics of the gear it is essential to optimize the toothing process. Herewith, the task of understanding the proceeding the heat processes during cutting is important to forecast of the tool wear, accuracy, and undulation of the processed surface. In the article the results of numerical simulation of thermal processes appearing during processing of bevel gear are considered. This paper presents the results of numerical modeling of thermal processes occurring in a tool, workpiece, and chips during bevel gear cutting. Also the influence of the design parameters of the cutting tool on the value of maximum temperatures and heat flows occurring in the process of cutting was investigated. The approaches which were used in that paper can also be applied to other cutting processes with the removal of a complex U and / or L shaped chips (gear shaping, broach etc.) [ABSTRACT FROM AUTHOR]

Computer fire modelling and design fire scenarios are traditionally used in the tunnel design process to challenge tunnel systems, e.g. smoke ventilation, evacuation routes and strategy, and the exposure of structural members. In general, any such fire scenario should be reasonably severe, however, not unrealistically, which may lead to unnecessary over-designing and cost increase. This approach is commonly referred to as the worst-case design fire approach. The objective of the paper is to analyze the impact of uncertainties associated with input data and design fire selection on the representativeness of the design fire scenario. Firstly, the design fire scenario specifications are mapped and uncertainties relating to input data identified and quantified. Subsequently, a risk-based design fire selection approach is introduced taking into account the objective of the analysis: life safety or property protection. The paper is concluded with recommendations regarding the significance of selected input parameters, given analysis objectives, and the possibilities of their uncertainty treatment. [ABSTRACT FROM AUTHOR]

This paper deals with the usage of a toolkit Control Design & Simulation in development software LabVIEW for simulation of a two-position controller. This automatic control can be used to regulate regulation processes with high rise time such as temperature processes. Many of these processes can be categorized as second order systems. Main topic of this paper is the description of on-off controllers, their abilities and shortcomings and the way of use of such controllers to regulate processes of a second order. The publication then describes the development software LabVIEW, mainly useful toolbox Control Design & Simulation. This module was then used to design, simulate and optimize two-position controller. [ABSTRACT FROM AUTHOR]

Cumulative nonlinear Lamb waves have been widely reported in experimental studies. These studies report on cases where nonlinear Lamb waves will increase in amplitude with propagation distance because the entire specimen is responsible for generating harmonics. The applications for nonlinear Lamb wave propagation include distributed damage such as fatigue and even identifying one type of metallic alloy from another. In this paper, nonlinear elasticity is presented as the key mechanism responsible for cumulative second order Lamb wave generation. This is followed by a series of numerical simulations which will shed light on how to achieve efficient generation of cumulative nonlinear Lamb waves. The effects of excitation amplitude and frequency-thickness will be explored through numerical modelling. The numerical results presented in this paper will support rules prescribed by other authors. It is found that both factors are crucial in producing a measurable nonlinearity. [ABSTRACT FROM AUTHOR]

This paper presents a study of the drawing process, 3D finite element simulations and show the dies geometry influences on the drawing force for steel wires. The wire drawing process is done with high energy consumption and the combination of the 5 regions of the die geometry contributes to the final properties of the product. In this way, the optimization and the control of process drawing by his automation leads to lower consumption of electricity (by minimizing the force necessary) and to a lower consumption of necessary dies (with a perfect geometry set). The simulations made in this paper shows that drawing forces are strongly influenced by variation of certain process parameters such as half approach angle or different values for the length of the bearing area. [ABSTRACT FROM AUTHOR]

This paper presents a method for defining and improving the traffic conditions in a set of cross section in the city of Cluj-Napoca, using microsimulation software for the traffic. Simulation models are designed to mimic the behavior of traffic in a time and space transport system in order to predict the system's performance. A simulation model studies a real world system, considering mathematical and logical concepts associated with the system operation and analyzes them using complex computer programming. Each simulation model presents a set of advantages such as: it can be more accurate than an analytical approach, it is able to test new conditions, it can improve the perspective concerning the significance of variables and of the way these variables interact. A case study is presented, using a set of three street intersections. In these intersections measurements of traffic during morning peak hours were performed. The measurements were acquired both manually and automatically, using time slots of 15 minutes each. The collected data was also used for model calibration. With the help of microsimulation software and a well-balanced model, information regarding traffic conditions can be found, resulting in analyses of the traffic evolutions. Some traffic conditions issues are identified and a set of improvement suggestions are presented. The measures proposed in this paper need to be tested and further optimized also by means of microsimulation, before being implemented, in order to obtain satisfactory results. The area under investigation exhibits quite large delays in traffic, in present-day conditions. This means smaller displacement speed, and, implicitly, more toxic emissions, that make the system be farther from the idea of sustainable transportation. [ABSTRACT FROM AUTHOR]

This paper presents the mathematical modeling of a multivariable process used in level control, under the assumptions that all pipes are filled with fluid and the inertial effects caused by flow variations, in case of small accelerations, are neglected. Because of the way the two tanks are interconnected and interact with each other, the resulting mathematical model is nonlinear. In the paper it is proposed a robust control algorithm for this plant developed based on H-infinity loop shaping procedure. The required computations and the study of the behavior of the system are done in the Matlab simulation environment. [ABSTRACT FROM AUTHOR]

The paper presents a numerical analysis of the resistance and stiffness of an aluminium-concrete beam with steel connectors. Aluminium-concrete structures are less known than steel and concrete composite structures, they do, however, have a lot of applications. In this paper, the resistance and midspan deflection of a composite beam calculated using the Abaqus program was compared with the results obtained in an experimental study. [ABSTRACT FROM AUTHOR]

This paper presents the basic methodologies used for Natural Smoke and Heat Ventilation Systems design under wind conditions, along with chosen numerical tools such as Computational Fluid Dynamics method and evacuation modelling as their supplement. First, results of comparison of different natural ventilation systems a series of transient CFD simulations are shown, illustrating potential problems in the system design with traditional approach. Later in the paper, authors focus on complete analysis of fire related phenomena in wind conditions, for a real historical shopping mall in Warsaw with vertical natural smoke ventilators. All of the steps of the analysis are described, together with some practical remarks. The reference analysis were carried in ANSYS Fluent CFD model, followed by evacuation study with building Exodus software. [ABSTRACT FROM AUTHOR]

The submerged floating tunnel is a new tunnel type, with complex structure and requiring high construction demands. While it has been theoretically researched for a long period of time, there is no application example. The uplift pile, with fatal research significance, is the structure foundation of a floating tunnel. The paper starts with the cable arrangement form of floating tunnels and gives an analysis on the force-bearing characteristics of pile foundation in the submerged floating tunnels; it integrates numerical simulation to analysis the characteristics of the bearing capacity of pile foundations changing with displacement curve (Q-S curve) under different inclinations. The soil deformation in the limit state of bearing capacity, the distribution of plastic failure zone and their relative causes are analyzed. The paper acquires the envelope curve of bearing capacity under the displacement effect of different inclinations, as well as the conclusion that 30° is a suitable temperature for cable arrangement. The research achievement has a certain guiding significance for the cable arrangement angle setting of floating tunnels and the reinforcement treatment of pile foundation. [ABSTRACT FROM AUTHOR]

The paper describes various modified algorithms of classical sinusoidal pulse width modulation (PWM) serving for a three-phase two-level inverter control. The paper presents the results of a research of 3 PWM versions with varying duty cycle parameters and frequency of the pulse signal modulation. The method is to divide the modulated sinusoidal signal cycle (half-cycle) into intervals in order to change the modulation frequency within the separate sectors of forming the quasi-sinusoidal output voltage waves. In addition, algorithmic ways to compensate the additional losses in the inverter and the induction motor at high modulation frequencies of a discrete control signal are investigated and described in the paper. Calculations and simulations are performed by NI Multisim simulation program and NI LabVIEW visual programming environment. Theoretical studies are performed using the electric drive theories, discrete control systems and spectral analysis. The practical implementation performed by Texas Instruments Stellaris Launchpad using the Energia prototyping platform, field-programmable gate arrays (FPGA) of National Instruments CompactRIO-9074 and NI Single-Board RIO GPIC (sbRIO-9606, NI 9683 (GPIC), LX45 FPGA) using NI LabVIEW software and add-on modules (LabVIEW Real Time, LabVIEW FPGA). The suggested inverter control methods make it possible to reduce the distortion of the output quasi-sinusoidal signal and reduce the power consumption of the DC link while significantly reducing the number of inverter transistor switching in comparison with the classical method without premodulation or technical devices (filter-compensating devices). [ABSTRACT FROM AUTHOR]

Precedence logic's four types of relationships, four types of margins and by simulating the work production through lags present several shortcomings that affect the accuracy of the schedule and margin calculations, as is well documented in the literature. To overcome these gaps, the Chronographic Method has proposed many developments over several years, including allowing for split activities with internal divisions according to quantities. Internal divisions extend the relationships between activities to deterministic and probabilistic point-to-point, by-section or continuous relations, generating realistic dependencies and new types of floats (Complete, Start, Finish and Partial floats). Activities and divisions may also have external and internal scales. External horizontal scales may designate the measuring unit of the x-axis for an orthogonal system and should be unique for the entire project (e.g. time that defines the external horizontal scale unit of the bar chart diagram). Internal horizontal scales can be distinct for each activity or section. External and internal scales may be based on time, cost, work progress, quantity, risk or performance. For the purposes of calculation, this paper uses time as the external scale and the amount of work as the internal scale. Relations and margins can then be calculated according to the external scale (time) or the internal scale (quantity). The calculation constraints and project tracking can then be based on either time or quantity. This paper explains this concept and the calculation equations for these new types of margins; discusses the limitations of the traditional margins and the use of time as the only scale required for relationship and margin calculations; and demonstrates the relevance of using other measures, including the amount of work, Site occupations for scheduling calculations. The proposed chronographic logic and margin calculations can then be used to simulate the project's real conditions. [ABSTRACT FROM AUTHOR]

The design of sport buildings has great impact on top-sport as well as on recreational sport-activities. It implies challenging tasks in meeting the performance-requirements. This includes the control of factors like daylight/lighting, air flow, thermal conditions, just to name a few. Such factors impact the performance of athletes and are hard to control in large sport halls; their control is even harder when the public/audience is located within the halls and require different climate conditions. While mechanical installations are often needed during competitions in order to guarantee constant conditions, relaying on mechanical installations during the daily and recreational use of the venues challenges their medium/long term sustainability. Computational form finding approaches can favour the achievement of high-performing and sustainable sport buildings. In this light, the paper tackles the use of Multi-objective and Multidisciplinary design optimization. The paper presents the concept of Multi-objective Multidisciplinary design optimization techniques to support trade-off decisions between multiple conflicting design objectives and interdisciplinary design methodology, during the conceptual design of sport buildings. The proposed method is based on parametric modelling, performance simulation tools and algorithms for computational optimization, for which the paper tackles three specific aspects. First of all, due to the complexity of large sport buildings, the formulation of the optimization and the screening of the related design variables is crucial in order to obtain a meaningful design space, which helps reducing unnecessary computational burden. Secondly, assessing performance based on measurements and analyses is crucial and can be supported by performance simulations tools; however effectively integrating performance simulations tools in the early phase of the design requires new tools. In this light, a customized computational process for the rapid assessment of temperature and airflow patterns is presented. Thirdly, the process requires the combination of design optimization and design exploration, while searching for well-performing solutions. The importance of design exploration is emphasized also for sub-optimal solutions. In order to facilitate the design exploration, the combination of optimization algorithms, multi-variate analysis algorithms and options for exploring design solutions via an interactive dashboard connected to a database are presented. To exemplify the method, specific case studies are developed as collaboration between Delft university of Technology and South China university of Technology. [ABSTRACT FROM AUTHOR]

Bicycle comfort is very important especially for enthusiastic road cyclists who can spend several hours astride their bicycle in a single ride. Being an abstract concept, several researchers proposed to assess bicycle comfort by measuring the level of vibration transmitted to the cyclist. This can be measured in a controlled laboratory environment but it requires cumbersome and expensive road excitation simulation setup. In-situ measurements are an alternative solution but the experiment repeatability is not as good as in the laboratory because many experimental factors are difficult to control while riding a bicycle on the road (e.g. cyclist's posture on the bicycle). This paper presents a test protocol to evaluate bicycle comfort with minimal uncertainty inherent of the in-situ experiment. Three main elements are used to enhance measurement repeatability and therefore increase the differentiating capability of the protocol: the measurand selection, the bicycle propulsion and the design of experiments. The power absorbed by the cyclist is used to quantify the level of vibration transmitted to the cyclist because it is far less sensitive to variation of cyclists’ posture than to the other measurands used to assess comfort such as acceleration. The bicycle is propelled from an external source which increases precision of the bicycle speed control during the experiment and eliminates measurement noise coming from the bicycle drivetrain. The experiment is specifically designed in term of test runs’ duration and replication to improve its repeatability. The protocol is presented in this paper as a case study of bicycle wheel comfort comparison and can be extended to any components or a complete bicycle comfort comparison. The same case study has been performed with different test methods in the laboratory which are used to assess and validate the accuracy of the presented in-situ protocol. [ABSTRACT FROM AUTHOR]

Salt expansion is one of the major problems of subgrade involving saline soils. Salt expansion is induced by the crystallization of salt when the soil water content or temperature decreases. A case of salt expansion in subgrade composed by saline soil is introduced. It is located in G314 Road, which is one of the national highways in China, from Urumqi to Khunjerab. There is 3.40 ∼5.91% salt within 1.0 depth in the ground surface of the G314 (K587 + 035), which belongs to strong sulphate salty soil. The maximum salt expansion is up to 20 cm in G314 Road, which has a serious impact on the road. Salt expansion is majorly controlled by the salt crystallization and the transmission of water and salt. Based on the solute transport theory in porous media, the water flow theory and thermal conduction theory, the govern differential equations of coupled salt crystallization, salt transmission and water flow are established in this paper. The coupled water and salt transfer problem of saline soil is solved by a software named as COMSOL with the use of a secondary development module. To verify the method for simulating the coupled water and salt transmission process, the water and salt transfer process in a 1D soil column is simulated and the results are compared with the theoretical solution. The results show that coupled model of water and salt established in this paper can accurately predict salt migration and crystallization of saline soil. [ABSTRACT FROM AUTHOR]

In modern ages, universities have shaped the civilized society and contributed to its knowledge base by educating the workforce, and providing consultation to government and businesses. In the wake of globalization, it is necessary to establish mutual beneficial relationships between universities and their urban areas; hence, the university - city complex model. In the context of Vietnam, most universities are located in urban areas; none of which, however, has fully engaged in the local community in meaningful ways. With the core idea of “Building an intelligent and ecologically friendly city”, this paper proposes the design of a university - city complex in Hung Yen province, Vietnam. This design will stimulate sustainable development of the local community through green architecture, spatial planning of university complex, and careful design of education programs and services. This paper will also present the conceptual knowledge of the subject, potential factors driving the development, and successful case studies of university - city complexes. [ABSTRACT FROM AUTHOR]

Coat-hanger dies are widely used in the extrusion of plate and sheet, since it can achieve uniform velocity attribution on the outlet according to balancing the distribution of flow through the die. A failure ABS extrusion die of a petrochemical company is studied in this paper through the method of numerical simulation which was done by finite element software Polyflow with structured grid meshed by ICEM. The results show that the pressure drop in the die exceed the maximum allowable value, which is the main cause of die failure, in addition to the exceeded pressure drop the fluctuation of the velocity on the outlet is too large, which would lead to poor quality of product. The work in the paper provides guidance for the future die design and optimization. [ABSTRACT FROM AUTHOR]

The inter-stand tension inferential control systems are used to stabilize the rolling motor torque. To stabilize the motor torque the electric drive system with the properties of the rolling motor torque supply may also be used. An alternate option may include torque stabilization by to the effect on speed of the previous, further or controlled mill stand. The tension control accuracy depends on how exact the unhindered rolling torque is determined. Nevertheless, a change in tension due to this factor may result in improving gauge accuracy in some systems. Using the model of the continuous rolling mill, the paper considers the force interaction between the stand electric drives for different technological conditions of rolling. It analyses the operation of the rolling mill using different system for tension inferential control. The finished studies prove that size alignment is provided with the tension control system affecting speed of the further stands. The paper verifies that the characteristics of the rolling mill including aligning ability depend on the rolling speed. It is a good practice to apply those results during the selection and calculation of the inferential tension controllers. [ABSTRACT FROM AUTHOR]

Transient analysis of the pipe flow is often more important than the analysis of the steady state operating conditions that engineers normally use to withstand the additional loads resulting from instantaneous rapid valve closures. The flow rate and fluid pressures in the system may change from significantly high to an extremely low magnitude after some time interval of valve closure. These types of unsteady flows are frequently encountered in sudden closing of upstream valve of a turbine in hydroelectric power station. The governing equations of unsteady flows in closed conduits are partial differential equations of hyperbolic type. One simple numerical solution technique available in the literature is the method of characteristics (MOC). In the current paper, the MOC model is explained through one case study of valve closure. One bench mark problem of reservoir on upstream end and a valve on the downstream of pipeline end is demonstrated in this paper. Fluid pressure and flow rate variations in pipeline with respect to time after the valve closure are arrived from MOC model. It is observed that pressure head increased after development of first pressure wave which is due to instantaneous closure of the valve at the downstream end of the pipe. The pressure head and flow rates are not dampened but they were found to be oscillating by increasing and decreasing in the total simulation time which may be due to wave propagation time and consideration of series pipe of different diameters in the current study. [ABSTRACT FROM AUTHOR]

In this paper an attempt has been made with experimental as well as theoretical analysis to find the variation in heat transfer coefficient with Reynolds number and numerical simulation attempt has also been done with different turbulence models in forced convection turbulent flows. Experimental analysis was carried out by using forced convection experimental setup at constant power supply to the heater and by varying the different flow rates of air with the help of a blower. The tube heat exchanger is fully insulated. In turbulent flows, the heat transfer coefficient is greatly affected by the turbulence, hence in this paper numerical analysis was carried out with different turbulence models and analysis has been done with both experimental and theoretical values to find the best turbulence model. [ABSTRACT FROM AUTHOR]

In this paper an attempt has been made to find the enhancement of heat transfer with different types of twisted tape inserts (TTWTT), that is inserts of twisted tape over the twisted tape at an angles of 90 and 180 degrees twist. In plain twisted tape at the location of swirl flow the mixing of fluid particle are not satisfactory so that the heat transfer is somewhat less than the turbulent regime so in this paper numerical analysis of thermal and hydraulic characteristics of water flow has been studied by inserting twisted tapes over the main twisted tape at the location of uniform stream lines forming zone. The numerical simulation was performed in order to gain an understanding of physical behaviour of the fluid flow (decaying swirling flow field), fluid temperature and local Nusselt number characteristics of a tube fitted with TTWTT. [ABSTRACT FROM AUTHOR]

In order to understand thermal characteristics of high altitude airships, the numerical simulation of convective-radiative coupled heat transfer performance at a certain time in a day is carried out using Ansys Fluent software. The governing equations of flow are using the compressible Reynolds averaged N-S equations and standard κ-ɛ turbulence model. A non-uniform temperature distribution boundary condition in the complex thermal environment and heat transfer mechanism is applied on the surface of high altitude airships based on user definition function (UDF) programming. The paper then simulates the external convection heat transfer characteristics at various flow conditions at 40 degrees north latitude at the altitude about 20 km at noon in the summer solstice. Finally, the corresponding calculation results of the surface temperature distribution, the flow field distribution and the convective heat flux distribution of airship envelope are presented, which are also analyzed in this paper. [ABSTRACT FROM AUTHOR]

In the mechanical ventilation room, human body will block the air flows and change the original airflow organization. In the crowd places, the influence of the crowd may greatly change the indoor air movement and even worsen the environment. So the effect can not be ignored. The paper studied the influence of the human body to the indoor air movement by using the method of Particle Image Velocimetry (PIV) and numerical simulation (CFD). The PIV experiment and numerical simulation contain two conditions. One condition is an empty room and another contains models of human body in the room. The paper compared the result of experiment and numerical simulation. Numerical simulations are demonstrated to be accurate in the two conditions, and the Standard k-ɛ model most accurately predicts the flow in a room contains crowd model. In this study, the numerical simulation and measurements show that the crowds will greatly change the air distribution and the residence time of the flows in the building. Therefore, it is important that crowds be considered in ventilation design. [ABSTRACT FROM AUTHOR]

This paper presents a simple membrane fouling model intended for use in conjunction with an activated sludge model to form an integrated model of a membrane bioreactor (MBR). It is based on an earlier development of Liang et al.[1] who divided fouling into short-term reversible fouling tantamount with cake deposition and long-term irreversible fouling representing th effects of irreversible particle deposition inside membrane pores. The original model was extended to account for cake detachment, back- flushing, and dependency of soluble microbial products (SMP) deposition on permeate flux. The model was identified on two sets of data from two experiments: a short-term flux stepping experiment under fluxes higher from the ‘threshold flux’ and a long-term filtration experiment under fluxes not exceeding the ‘threshold flux’. Additionally, the paper proposes a simple ‘pen and ruler’ identification method for unique estimation of model parameters based on the information obtained from flux stepping experiments. [ABSTRACT FROM AUTHOR]

This paper focusses on robust decision-making in disaster response where pre-existing logistical structures have not been destructed yet but where a great risk of delayed consequences exists if the functioning of these structures is not strengthened. Responsible decision-makers are companies as operators of the logistical structures themselves, particularly those whose businesses refer to the critical infrastructure sectors food, water, health care, and energy. This paper outlines a conception of a simulation model which combines approaches of scenario-based optimization, stress testing, and robustness measurement.The conception is developed for a decision problem of a food retail company where a society must be prevented from threatening food shortages due to a flu epidemic in Berlin, Germany. [ABSTRACT FROM AUTHOR]

In this paper, we propose an approach to constructing an index of air traffic control difficulty based on exponential functions of proximity parameters of aircraft pairs, i.e. the time to closest point of approach and miss distance. The index is given by single value between 0 and 1 in order to simplify its presentation, such as in a heat map. The approach deals with the mapping of aircraft trajectory information onto proximity parameters and the derivation of the real-valued index in [0,1]. The approach consists of the following steps: 1) Formulation of the concept of a difficulty index calculated from the trajectories of a pair of aircraft at a given time; 2) Determination of an objective function which evaluates the projected difficulty; and 3) Derivation of the difficulty index as a function of the trajectory information and model parameters. This paper briefly describes the method of mapping and some results from numerical calculation examples using the proposed method. [ABSTRACT FROM AUTHOR]

This paper first analyzes the causality of the maintenance and support (M&S) cost's generation; then draws the stock and flow diagram, establishes the correlation equation of stock, flow, instrumental variables, constants and determines their initial value; on the basis of the model reasonable, analyzes the model's calculation results, observes the change of the model results by adjusting model's parameters to determine the optimal strategy, provides decision support for decision-makers. Emphatically analyzes the influence of parts’ failure rate and preventive maintenance rate on maintenance costs during the equipment's life circle. The analysis results have verified this paper's simulation method's practicality. [ABSTRACT FROM AUTHOR]

The research on the concentrated smoke extraction system of crossrange exhaust duct in double-layer shield tunnel is still very lack in the world. This paper is on the smoke extraction system of double-layer shield tunnel. It will provide the supports and references for the smoke control of tunnel fire and the determination of related technical parameters in the design of tunnel fire ventilation and smoke extraction, so it has important scientific value, practical significance and application prospects. This paper bases on the tunnel project of Slender West Lake in Yangzhou. By using the method of combining theory and numerical simulation, a conclusion can be drawn that the reasonable smoke exhaust rate of the upper tunnel is 140 m 3 /s. [ABSTRACT FROM AUTHOR]

This paper focuses on a technique for predicting surface cracks in hot free forging. These surface cracks occur at the side on which strains concentrate when a round bar is compressed by hot free forging. A final product has hardly any surface cracks because they are removed by gas scarfing. These conventional manufacturing processes have an industrial problem of low productivity with a waste of time. The suppression of the surface cracks is required. The mechanism and criteria for the surface cracks are not clear. In this paper, the mechanism of surface cracking was estimated, compared with the actual forging process. The mechanical property was evaluated by a high temperature tensile test. Various numerical simulations which changed the damage parameter ( C value) were carried out. The critical value ( C 1 ) is calculated by shape comparison between the tensile test and the numerical simulation. It is possible to predict the surface cracking in the hot forging process by using this parameter. [ABSTRACT FROM AUTHOR]

Friction dampers are one type of energy dissipation devices that are able to forms an efficient seismic protection system for seismic structures. Nevertheless, traditional friction dampers can only be designed under a target earthquake of a given intensity. Complied with the current design code, this target earthquake usually has an intensity of the return period of 475 years. Consequently, traditional friction dampers may function well under earthquakes with the intended design level, but may not be functional for earthquakes with lower intensities. This situation may pose a problem particularly for some functional facilities, which usually contain vibration-sensitive equipment that is vulnerable to earthquakes with moderate intensities. In order to satisfy the aforementioned multiple functional demands, this paper investigates the possible use of a novel multi-functional friction damper (MFD). Different from traditional friction dampers, the MFD has two-stage slip forces that can be activated in a moderate and a strong seismic level, respectively. The theory of the MFD and the formulation of a SDOF system with the MFD are both given in this paper. The results of the numerical simulation reveals that the MFD is able to reduce the structural responses under strong and moderate ground motions, simultaneously. In addition, the MFD is also more effective at reducing the structural responses under a moderate earthquake, as compared to the response result from a traditional friction damper. [ABSTRACT FROM AUTHOR]

Abstract: Electric utilities and end users of electric power are becoming increasingly concerned about meeting the growing energy demand. Renewable energy source (RES) form an invincible part of electric power distribution. Wind energy which forms one of the major available renewable energy sources. In this paper a grid interfacing inverter is designed which acts as a power converter to inject power generating from RES to grid and also act as Shunt Active Power Filter (SAPF) to minimize the harmonics, load neutral current. A new control approach named Unit Vector Template Generation (UVTG) is designed for SAPF and presented in this paper. The simulation has been done for three phase four wire (3P4W) distribution system. [Copyright &y& Elsevier]

Abstract: The merging behavior at the floor-stair interface of high-rise building based on computer simulations is investigated in this paper. A landing with dogleg stairs is adopted in this research. Four different configurations show that the evacuation time is almost a linear function to the number of storeys. Furthermore, the door from the floor to landing, which is on the opposite side of the landing to the incoming stair, is the best situation to improve the upper floors’ evacuation effect, and restrain the lower floors’ evacuation. At the same time, the door from the floor, which is adjacent to the incoming stair, is the worst situation to improve the lower floors’ evacuation, and restrain the upper floors’ evacuation. Additionally, with these results obtained in this paper, the building designer can select a more suitable position to place the evacuation doors. [Copyright &y& Elsevier]

Abstract: The work described in this paper uses the Holmquist-Johnson-Cook equation of state and constitutive model for concrete and appropriate material parameters derived from mechanical test data to perform numerical simulations of penetration and perforation of adobe building material. Experimental results from the literature are modeled, and two-dimensional numerical simulations are carried out using the CTH Eulerian shock physics code. Two groups of simulations were performed in accordance with the experimental results. The first group is tungsten rod penetrators, with impact velocities ranging from 340 to 820 m/s, perforating adobe targets with thicknesses ranging from 71 to 497mm, and comparison of the residual velocities predicted by the numerical simulations with the available experimental results. The second group is steel spheres, with impact velocities ranging from 500 to 3230 m/s, penetrating into adobe targets of semi-infinite thickness, and comparison of the depths of penetration predicted by the numerical simulations with the available experimental results. The technique described in this paper for modeling and simulation of adobe penetration and perforation is able to adequately predict the residual velocities and depths of penetration for the conditions modeled. [Copyright &y& Elsevier]

Abstract: In the paper the analysis of the influence of fire load on class of cross-section of steel structural elements is presented. In the fire situation some cross-sections may have a different class than at room temperature. Special attention is focused on steel structural elements which are Class 3 at room temperature and Class 4 in the fire situation. The examples illustrate a steel element, which obtain different class of cross-section at room temperature and in the fire situation. The reduction of critical temperature and fire resistance time is also taken in to account. The structure under consideration pertains the steel beam, which is a part of the existing building in Poznan. In the paper, the comparison between fire resistance of the beam using simulation of fire in FDS software and procedure according to standard time- temperature ISO curve is presented. [Copyright &y& Elsevier]

Abstract: The evacuation process in a supermarket is simulated by a two-dimensional Cellular Automata (CA) model in this paper. In this model, the interactions among people and those between people and obstacles in forward direction are considered, and the ‘Danger-degree’ concept is introduced to solve the path select of people evacuation process. This paper studies the effect of different shelves’ orientation and personal familiarity degree of exits to evacuation time. The result shows if occupants are fewer in supermarket, shelves orientations have little influence on evacuation time; but when occupants are larger, the longitudinal shelves orientation is more appropriate for evacuation in supermarket than transverse shelves orientation. The study also found that the evacuation time reduces, the exits’ available time improve with the increase of personal familiar with exits by induction. This can provide theoretical foundation for arranging the shelves orientation in supermarket as well as drafting contingency plans of pedestrians’ induction evacuation. [Copyright &y& Elsevier]

Induction hardening as common heat treatment process for highly-stressed automotive components significantly affects the surface layer properties leading to a compressive residual stress condition and a local hardening of the material. The beneficial effect of the post-treatment is generally well investigated and already implemented in industrial applicable guidelines by considering nominal fatigue strength enhancement factors. However, as the fatigue strength improvement essentially depends on the applied manufacturing process parameters, the resulting local material properties and the local load stress distribution, an elaborated numerical fatigue assessment procedure based on a manufacturing process simulation of a notched round specimen is presented in this paper. Thereby, a two-dimensional axi-symmetric model is set-up, whereby the inductive heating process is performed in COMSOL® and the subsequent quenching process in SYSWELD®. The resulting axial residual stress condition at the notch area of the specimen reveals a sound accordance to X-ray measurements. Finally, a local fatigue strength assessment based on the local strain approach is shown. Herein, manufacturing dependent residual stress states are considered as mean stresses on the basis of the damage parameter by Smith, Watson, and Topper. The estimated fatigue data points agree well to results of four-point bending fatigue tests, which basically prove the applicability of the presented fatigue design methodology. [ABSTRACT FROM AUTHOR]

This paper is to investigate the smoke flow temperature beneath the ceiling in an atrium-style subway station. Numerical simulations were carried out in a full-scale model to study the temperature profile beneath the ceiling by considering different fire source locations. Results show that the maximum smoke temperature beneath the ceiling can be predicted using the three models developed by Alpert, Heskestad and McCaffrey. The choice of the most suitable model depends on the fire source location. For the longitudinal temperature distribution along the ceiling, if the disturbance region is far away from the fire source, the temperature profile can be well correlated by the Li’s model. However, if the disturbance region is close to the fire source, the models proposed by Li and He should be used together. The temperature profile beneath the ceiling in this kind of subway station with different fire source locations can be obtained by the combination of these models. [ABSTRACT FROM AUTHOR]

This paper presents computer simulation investigations on the fire smoke movement above street canyons under a velocity condition. Two buildings with different aspect ratios, when the range of windward building height is 5 ~ 17 m and the leeward building height is remain at 18 m, have been considered. Besides, the width of the street canyon has been taken as an important factor to influence the critical velocity here. It is shown that the critical velocity of the fire smoke, which moves from windward building to the leeward building, decreases with the height of windward building firstly, but increases with its further increase. According to the theoretical analysis, it is found that the critical velocity is a function of dimensionless width of street canyon. And a developed model has been developed to predict the critical velocity above the street canyon. [ABSTRACT FROM AUTHOR]

Electrohydraulic forming (EHF) is one of the high-speed forming process that uses high-voltage discharge in liquid. Shockwave resulting from the discharge is generated between two electrodes in liquid and it deforms the blank into the die. When the blank is deformed in a very short time, the formability is enhanced and springback can be reduced. Furthermore, in electrohydraulic forming, the blank has no bouncing effect that happens in other high-speed forming process. Therefore, it is possible to deform the blank into a complex shape with only one operation. In this paper, numerical and experimental study of electrohydraulic forming was performed using an Al 6061-T6 sheet material. Numerical model was formulated in LS-DYNA program. ALE (Arbitrary Lagrange-Eulerian) scheme was applied to create the elements of the fluid parts and structural parts were modelled using shell elements. From the results of the numerical simulation, it was observed that the pressure of the fluid parts was increased by the electric energy and the movement of the water part could deform the blank into the die. In addition, electrohydraulic forming apparatus was developed and experiment was carried out using an equipment of 32 kJ capacity and conical die. Comparison of the numerical and experimental results was also conducted on the bulge height of the blank and it also showed similar tendency in relation to the deformed shape. [ABSTRACT FROM AUTHOR]

Laboratory testing of tribo-systems for sheet metal forming applications must ensure similar conditions with the tribo-parameters that are commonly utilized in real production in order to generate data that is meaningful for industry. The main parameters to consider are the tool and workpiece materials, surface roughnesses, normal pressure, sliding length, sliding speed, interface temperature and lubrication. This paper proposes a new Strip Reduction Test (SRT) for industrial ironing processes that is capable of replicating the highly severe tribological conditions that are experienced during both the forward stroke and the backward retraction of the punch. The new SRT tool design is implemented in a new Universal Sheet Tribo-Tester (UST), which can run multiple tests continuously from a coil. The test is capable of simulating various process parameters such as reduction, drawing speed, tool temperature, sliding length and quantifying the onset of breakdown of the lubricant film and subsequent galling after several strokes not only when emulating the forward strokes but also the backward strokes. Preliminary tests disclose promising results as regards the identification of lubricant film breakdown by detecting changes in measured force, surface roughness and/or torque values. [ABSTRACT FROM AUTHOR]

In hot strip rolling, the work roll shifting method has been widely used to disperse thermal crown and wear of the work rolls in the axial direction. This paper provides a strategic control method for the work roll profile which surpasses the conventional work roll shifting method. A numerical simulation model which enables prediction of thermal crown and wear of work rolls with high accuracy has been developed, and a new shifting method has been proposed, focusing on the problems of the conventional shifting method. In the conventional shifting method, the work roll shift position follows the prearranged pattern, and the work roll profile is not controlled intentionally. On the other hand, in a new work roll shifting method, the work roll profile of all coils in the rolling campaign are predicted by the numerical calculation, and controlled so as to be equal to the target profile by considering the work roll shift position. An evaluation function consisting of the error between predicted work roll profile and the target profile of all coils in the rolling campaign has been used, and the work roll shift position has been decided by the optimum calculation with minimizing the evaluation function. [ABSTRACT FROM AUTHOR]