Journal of Mechanical Engineering 58 (2012) 2

 

 

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Backward Hole-Flanging Technology Using an Incremental Approach

Authors - Aleš Petek* – Karl Kuzman

Abstract

The manufacturing of necks on the sheet metal parts using conventional hole-flanging process in small series production is sometimes too expensive or even impossible due to the complexity of the product. For these reasons, a modern manufacturing concept called the “backward incremental hole-flanging process” is proposed. It enables producing necks on the final products that can be very complex or even closed with minimal expense.
Special attention is dedicated to researching technological particularities and limitations according to industrial requirements. Due to numerous input factors having various levels of influence, empirical modelling was selected with the aim of ensuring better prediction of results. It enables predicting the impact of each particular input parameter and their iterations on the selected output variables. Results show that forming tool diameter, and horizontal and vertical step sizes have the greatest influence on the process. Moreover, the appropriate selection of process parameters results on a higher forming limit ratio and consequently, on larger necks achieved without cracks in comparison to the conventional hole-flanging process. The reason could be found in local incremental deformation of the sheet metal and a more suitable stress state.

Keywords - backward hole-flanging, incremental forming, sheet metal

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 58(2012)2, 73-80
DOI:10.5545/sv-jme.2011.194

Backward Hole-Flanging Technology Using an Incremental Approach (.pdf 1.3MB)

 

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A Dynamic Rescheduling Model with Multi-Agent System and Its Solution Method

Authors - Fuqing Zhao* ‒ Jizhe Wang ‒ Junbiao Wang ‒ Jonrinaldi Jonrinaldi

Abstract

Dynamic rescheduling problem is an important issue in modern manufacturing system with the feature of combinatorial computation complexity. A dynamic rescheduling model, which is based on Multi-Agent System (MAS), was proposed. The communication and negotiation mechanism between agents were addressed to support the autonomic decision for each individual agent and the multi-agent system. Furthermore, the simulation results in dynamic scheduling accompanying with its perturbation show that the proposed model and the algorithm are effective to the dynamic scheduling problem in manufacturing system.

Keywords - MAS, agent, dynamic scheduling, Contract Net Protocol, negotiation mechanism, perturbation

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 58(2012)2, 81-92
DOI: 10.5545/sv-jme.2011.029

A Dynamic Rescheduling Model with Multi-Agent System and Its Solution Method (.pdf 2.1MB)

 

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Neural-Network Estimation of the Variable Plant for Adaptive Sliding-Mode Controller

Authors - Suzana Uran ‒ Riko Šafarič*

Abstract

The Lyapunov based theoretical development of a neural-network sliding-mode based estimation of highly non-linear and variable robot plant for a direct-drive robot controller is shown in the paper. Derived adaptive control law was tested for four types of robot neuralnetwork sliding-mode controllers: centralized, simplified centralized, decentralized and simplified decentralized, which were verified on a real laboratory direct-drive 3 D.O.F. PUMA like mechanism. Centralized and decentralized control approaches estimate only a part of the variable robot dynamic model (torque model due to friction, Coriolis, centripetal and centrifugal forces) and use only the part of a dynamic plant model (the so called estimated inertia matrix M). Both simplified methods do not need any plant model parameter for an accurate estimation of the direct-drive robot plant, but need some more time to learn dynamic model parameters. All four types of the neural network continuous slidingmode controllers were successfully tested for algorithm’s adaptation capability for sudden changes in the manipulator dynamics (load).

Keywords - sliding-mode adaptive controller, neural-network, robot

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 58(2012)2, 93-101
DOI: 10.5545/sv-jme.2011.098

Neural-Network Estimation of the Variable Plant for Adaptive Sliding-Mode Controller (.pdf 728KB)

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Effect of Agitation Work on Heat Transfer during Cooling in Oil ISORAPID 277HM

Authors - Bohumil Taraba* − Steven Duehring − Ján Španielka − Štefan Hajdu

Abstract

The article focuses on the issue of heat treatment. The cooling curves were obtained for Isorapid 277HM with an experimental way of temperature measuring and their statistical processing. Experimental method was consistent with the test normative ISO standard 9950 (Wolfson’s test). The cooling oil Isorapid 277HM was agitated with different agitation work and had a constant temperature of 50 °C. In the next part of this article the surface temperature depended combined heat transfers were calculated. The methodology was based on inverse heat transfer. The interpretation code was software ANSYS and ORIGIN.

Keywords - quenching, cooling curve, agitated oil, heat transfer, Wolfson’s probe, ANSYS

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 58(2012)2, 102-106
DOI:10.5545/sv-jme.2011.064

Effect of Agitation Work on Heat Transfer during Cooling in Oil ISORAPID 277HM (.pdf 2.0MB)

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Analysis of Building Electric Energy Consumption Data Using an Improved Cooling Degree Day Method

Authors - Gorazd Krese – Matjaž Prek* – Vincenc Butala

Abstract

In cases where a quick insight into the operation of an HVAC system is more important than accuracy, cooling degree days can be used for monitoring electric energy consumption dependent on meteorological conditions. Cooling degree days are calculated from differences between outdoor temperatures above the base temperature and the base temperature itself, therefore containing both climate and building information. The difficulties in applying this method are the determination of base temperature and choosing a procedure for calculating degree days, which vary depending on the resolution of the weather data used. In addition, the cooling degree method has a major flaw, i.e. it considers only a linear dependence between cooling energy consumption and sensible cooling load, thereby ignoring latent loads, which become more significant at higher outdoor temperatures.
In this article an analysis of real electric energy consumption data using the cooling degree method and an improved method derived from it that includes latent loads, as well as a comparison between them, are shown. Both methods are applied several times to metered data, each time with a different combination of a method for determining base temperature and a degree day calculation technique.

Keywords - building electric energy consumption, cooling degree day, base temperature, latent load, wet-bulb temperature

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 58(2012)2, 107-114
DOI:10.5545/sv-jme.2011.160

Analysis of Building Electric Energy Consumption Data Using an Improved Cooling Degree Day Method (.pdf 1.3MB)

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Finite Mixture Estimation Algorithm for Arbitrary Function Approximation

Authors - Matej Volk* – Marko Nagode – Matija Fajdiga

Abstract

The paper considers a new prospect of the arbitrary continuous function approximation from a limited set of input data with the REBMIX algorithm, developed for the finite mixture density estimation. Since the REBMIX estimates the unknown parameters with the unique semiparametric method, it is assumed that it could be used also for the estimation of the unknown parameters in the fields that are not directly connected to density function estimation.
For the approximation of the arbitrary continuous function with the REBMIX algorithm, the required procedure is developed in the paper. The results gained by the proposed procedure and by the radial basis function network for three different datasets are compared by calculating the RMSE values between estimated and test output values. The adequacy of the proposed procedure is estimated by using both univariate and bivariate datasets. It can be concluded that with the developed procedure, the REBMIX algorithm can be applied successfully for the continuous function approximation.

Keywords - REBMIX algorithm, function approximations, finite mixtures, RBF networks, parameter estimation

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 58(2012)2, 115-124
DOI:10.5545/sv-jme.2011.085

Finite Mixture Estimation Algorithm for Arbitrary Function Approximation (.pdf 895KB)

 

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Description and Modeling of the Additive Manufacturing Technology for Aerodynamic Coefficients Measurement

Authors - Saeed Daneshmand* ‒ Cyrus Aghanajafi

Abstract
Casting, machining and additive manufacturing technologies are used in order to produce wind tunnel testing models. The models can also be analyzed by computational fluid dynamics methods. Both have their advantages and disadvantages. Since several wind tunnel models are required to accomplish aerodynamic experiments, nowadays, one of the best methods for models and airfoils manufacturing are additive manufacturing technologies. These methods are increasingly used in aerospace industry. In this research, wing and tail of a wind tunnel test model which has complicated sections, are produced by fused deposition modeling technology. In order to improve mechanical properties and surface roughness an electroplating is used on the surface of a RP model. Metal models along with fused deposition modeling models and electroplating models were tested in wind tunnels with different angels of attack. Results indicated that aerodynamic coefficients of electroplating model with a chromium coating was closer to metal model than those of AM model without electroplating. Substituting conventionally made parts with electroplating models, saves both cost and time. These models can be used in wind tunnel tests and aerodynamic data have acceptable quality.

Keywords - additive manufacturing, wind tunnel, angels of attack, aerodynamic coefficient

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 58(2012)2, 125-133
DOI: 10.5545/sv-jme.2010.238

Description and Modeling of the Additive Manufacturing Technology for Aerodynamic Coefficients Measurement (.pdf 783KB)

 

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Application of CFD Simulation in the Development of a New Generation Heating Oven

Authors - Zlatko Rek* − Mitja Rudolf − Iztok Zun

Abstract
This paper deals with the application of Computational Fluid Dynamics simulation in the development of a new generation cooking appliance in Gorenje concern. As the oven is multifunctional, radiation, conduction, natural and forced convection mechanisms of heat transfer are used. The Discrete Ordinate (DO) model is used for radiation. The density of air is described by incompressible ideal gas equation in a natural convection model. The intention was to create the best possible baking conditions for different heating systems. Several discrete models were created. The influence of geometry change and boundary conditions variations to the velocity and temperature field distribution in the oven cavity was analyzed. The results of numerical simulations are validated with measurements taken from an oven prototype. The agreement was good. After successfully passing the standard tests, the oven came into serial production and was launched on the market.

Keywords - oven, heat transfer, CFD simulation

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 58(2012)2, 134-144
DOI:10.5545/sv-jme.2011.163

Application of CFD Simulation in the Development of a New Generation Heating Oven (.pdf 678KB)

 

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