Krešimir Grilec, Lidija Ćurković, Irena Žmak: Wear Rate Evaluation of Sol-Gel TiO2-ZrO2 Films by Quantitative Depth Profile Analysis

Wear resistance of metallic materials can be improved by modifying their surface with different coating deposition techniques, one of which is the sol-gel technology. The sol-gel technology is simple, easy to adopt, requires low processing temperatures and leads to a high degree of purity of oxide coatings. In this paper, the erosive wear resistance of a ceramic nanostructured sol-gel TiO2-ZrO2 film consisting of three layers, deposited on a stainless steel substrate (X5CrNi18-10) by means of the dip coating technique has been studied. Quartz sand was used as an erodent with an impact angle of 30deg. Quantitative Depth Profile (QDP) analysis was used for the determination of the coating thickness and chemical composition before and after solid particle erosion. Glow Discharge Optical Emission Spectrometry (GDOES) was used for the analysis of the chemical composition of the bulk material (substrate) and the quantitative depth profiling of the deposited sol-gel film. The obtained results show that solid particle erosion of nanometric films can be monitored by depth profiling of the deposited sol-gel film.

Key words: sol-gel; TiO2-ZrO2 film; tribology; quantitative depth profiling

Original scientific paper

Yang Wu, Li Hou, Dengqiu Ma, Yongqiao Wei, Lan Luo: Milling Machine Error Modelling and Analysis in the Machining of Circular-Arc-Tooth-Trace Cylindrical Gears

This paper is to study errors of a milling machine used for the machining of Circular-Arc-Tooth-Trace (CATT) cylindrical gears. A topological structure model of the milling machine is established using the lower numbered body array approach. Coordinate transformation matrices between adjacent parts of the milling machine are set up by the D-H homogeneous transformation matrix. Based on the topological structure model and transformation matrices, a comprehensive error model of a milling machine used for the machining of CATT gears is established. According to the error model, the angle errors of the milling point are linear combinations of the angle errors of moving parts, while the displacement errors of the milling point are related to displacement errors, the angle errors of moving parts, the adjustment parameters of machine tools, and the geometric parameters of the gear. Finally, the influence of the errors of the cutter head on the milling point errors in the machining of CATT gears are discussed. The research can provide a theoretical basis for the error analysis, precision design, and the geometric error compensation of a milling machine used for CATT gear machining.

Key words: Circular-Arc-Tooth-Trace (CATT) cylindrical gear; milling machine; topological structure model; coordinate transmission matrix; comprehensive error model

Original scientific paper

Milica Nikodijevic, Zivojin Stamenkovic, Jelena Petrovic, Milos Kocic: Unsteady Fluid Flow and Heat Transfer Through a Porous Medium in a Horizontal Channel with an Inclined Magnetic Field

This paper investigates the unsteady flow and heat transfer of a viscous, incompressible, and electrically conducting fluid through a porous medium in a horizontal channel. The basic physical properties of the fluid and the porous medium are constant. The fluids considered are those with the Prandtl number less than 1. The channel walls are made of horizontal permeable plates, which are at constant but different temperatures. Fluid suction/injection through the plates occurs at a velocity perpendicular to the plates, whose intensity is a cosine function of time. The applied external magnetic field is homogeneous and inclined in relation to the transverse plane of the channel. The problem is dealt with through an inductionless approximation. Fluid flow is instigated by constant pressure drops along the channel. The equations used to describe the problem are transformed to dimensionless forms and solved analytically using the perturbation method. Approximate analytical expressions for dimensionless fluid flow velocity and dimensionless temperature are determined as functions of the following physical parameters: Prandtl number, Hartmann number, porosity factor, frequency, amplitude, and magnetic field inclination angle. Numerical results are presented as diagrams and tables and are used to analyse the influence of physical parameters on the fluid flow velocity and temperature.

Key words: Fluid flow; Heat transfer; Prandtl number; Hartmann number; Perturbation method

Original scientific paper

Hacı Bekir Özerkan, Can Çoğun: Electrochemical Small Diameter Deep Hole Drilling of Powder Metal Steel

In this study, a new hybrid electrochemical drilling (ECD) method is proposed. The method makes use of a tubular tool capable of rotating and an electrolyte flushing through the inner hole at the same time. The designed and manufactured small size ECD machine’s most important features are the regulation of the tool feed rate via current feedback control and the use of a rotating tubular tool with internal electrolyte flushing. The powder metal (PM) FLN2 4405 steel was drilled by using a brass tubular tool with various combinations of machining parameters such as machining voltage, electrolyte concentration and flushing pressure, and tool rotation speed. The machining performance outputs, namely, material removal rate (MRR), average radial overcut (RADOC), conicity (CO) and hole geometries were calculated and compared in different machining conditions. The results have shown that the aforementioned variables had a direct impact on the machining performance outputs in ECD. In all experiments, MRR increased with an in increase in machining voltage, tool rotational speed, electrolyte concentration and flushing pressure. RADOC values decreased with the rotational speed of the tool. The present study shows that deep holes with precise geometries and dimensions can be drilled successfully by employing the proposed hybrid ECD method. The method is economical and environmentally friendly since it requires low machining current values (0.1 to 0.7A) and a small amount of non-hazardous halide salt solutions instead of acidic solutions throughout the drilling process.

Key words: electrochemical drilling; rotational tubular tool; current feedback control; PM steel workpiece

Original scientific paper

Zhang Qi, Wen Guang, Luo Lan, Tang Rui: Contact Stress Prediction Model for Variable Hyperbolic Circular Arc Gear Based on the Optimized Kriging-Response Surface Model

In order to study the influence of design parameters (pressure angle, tooth width, tooth line radius, modulus, and moment) on contact stress of variable hyperbolic circular arc gear (VHCAG) and to obtain the best manufacturing parameters, The Kriging-Response Surface Model, a hybrid surrogate model with adaptive quantum particle swarm optimization (QPSO) algorithm was proposed to establish the expression prediction model for the relation between design parameters and contact stress. An intelligent quantum particle swarm optimization algorithm based on adaptive weight and natural selection is proposed to optimize the parameters of Gaussian variation function of the kriging surrogate model to improve its fitting accuracy. The global search ability of quantum particles is improved, and the accuracy and stability of the algorithm are improved by adjusting the weight of quantum particles adaptively and by optimizing the elimination iteration process, and the response relationship between design parameters and contact stress was established. The binomial response surface model of gear design parameters and contact stress is established based on the output obtained through the improved kriging model; this simplifies the complex expression of the kriging model. The effects of parameters and their cross-terms on contact stress are analysed based on the contact stress prediction model established by using the optimized Kriging-Response Surface Model hybrid surrogate model. The hybrid Kriging-Response Surface Model surrogate model lays a foundation for the research on the reliability and robust optimization of cylindrical gears with variable hyperbolic arc tooth profile.

Key words: contact stress; design parameters; Latin square sampling method; prediction model; hybrid surrogate model; parametric impact analysis

Original scientific paper

Michal Zoubek, Peter Poór, Tomáš Broum, Michal Šimon: Methodology Proposal for Storage Rationalization by Implementing Principles of Industry 4.0. in a Technology-Driven Warehouse

The paper deals with storage rationalization and brings forward a proposal of a methodology for the rationalization of storage systems in warehouses of industrial companies. The methodology emphasizes the new concept of Warehouse 4.0, including Industry 4.0 warehouse applications in general. The first part of the paper starts with the theoretical background and a description of logistics, Logistics 4.0, warehouse systems, Warehouse 4.0 and modern approaches linked to Industry 4.0 that can be implemented in logistics. Then, the factors influencing the effectiveness of the warehouse are summarized – this is an original summary based on the available literature and other sources. After this, storage rationalization and the related costs are described. The main subject of the paper is explained in the second part of the paper, which concentrates on the proposal of a methodology for storage rationalization of warehouses in industrial companies. The individual steps in the storage rationalization are described. The purpose of the paper is to share information, firstly, about the summarised factors influencing the effectiveness of a warehouse and, secondly, about the methodology proposal itself. This information may inspire other research institutions to consider aspects of this subject matter, which could be otherwise overlooked.

Key words: logistics; warehouse; rationalization; Warehouse 4.0; Industry 4.0

Original scientific paper

Jan Furch: The Model Prediction of Life Cycle Ownership Costs of Special Motor Vehicles

The paper deals with the prediction of life cycle costs related to special motor vehicles. In the first part, there is an analysis of the applied commercial software programs used for calculating and predicting the life cycle cost of vehicles. Next, there is a description of risks which might occur when calculating the life cycle cost and of the possible risk management. In the second part of the paper it is suggested that the motor vehicle life cycle cost can be predicted based on accurate data which are generally difficult to obtain, e.g. failure intensity z(t) or mean time between failures (MTBFs) used for calculating the cost after maintenance. The final part includes a proposal for the prediction of the ownership life cycle cost which consists of the operating and maintenance costs of special motor vehicles. This proposal is based on the company logistic information system, which at regular intervals assesses special vehicle life cycle cost during operation and maintenance. Under special motor vehicles here we understand the vehicles which are equipped with a chassis and a special vehicle superstructure which consumes operation units and on which maintenance is performed. Such vehicles are used in the construction or agricultural industry as well as in the military environment. The paper focuses on the design of a prediction model of the ownership life cycle cost of the military environment, where a relevant military logistic information system is used.

Key words: motor vehicle life cycle cost; prediction model; life cycle cost prediction; ownership cost; operating cost; preventive maintenance cost; corrective maintenance cost

Original scientific paper

Mirko Đelošević, Goran Tepić: Buckling and Vibration of a Stepped Plate

This study analyses the elastic stability and free vibration of a simply supported stepped plate under combined loading conditions defined by the parameter α. Mathematical identification of these phenomena has been made using Levy’s method as implemented in the conditions of equivalent fictitious load. The buckling coefficient k and the frequency parameter λ of the stepped plate were verified according to literature sources. Influential parameters of stability and the free vibration of the stepped plate under combined load were identified. It has been concluded that the buckling coefficient primarily depends on the relative thickness Δt, while the frequency parameter λ was significantly affected by the position of discontinuity Δb. Pure bending (α=2) induces several buckling modes for the same plate geometry with respect to uniform compression (α=0), thus creating a considerable technological stability reserve, particularly at higher discontinuities. Formulation of the frequency parameter enables us to choose the optimum geometry with minimal susceptibility to the appearance of free vibration in the plate.

Key words: stability; vibration; stepped plate; buckling coefficient; frequency parameter

Original scientific paper

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