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Open access

Nikodem Wróbel, Michał Rejek and Grzegorz Królczyk

Abstract

The purpose of this study is to form and test inseparable tight joints, commonly used in the construction of heat exchangers, by crimping operation on designed prototype stand. Crimped joints are made by tools in form of cones with two types of shapes, each of the designed tools have got identical forming angle. This study uses two types of connecting blocks and plates, differing in diameters of hole and flange. Elaboration contains a case study of joints being made by the stand, which in addition to the crimping operations for some cases were glued or brazed. The article presents the features of the formed joints, by examining them by destructive testing: Micrography, tensile strength test, and non-destructive testing: Leakage test. The examined elements have been made of aluminum 6060, which is well suited to indirect or direct operations of forming joints for all kinds of coolers or condensers. Elaborated tests and studies in this study allowed to state, that joining the connection block to plate with the small diameter, was more energy-consuming than in sample sets with bigger diameter, use of glue increasing the strength of the joints by 20%, significant strength increase can be obtained after mechanical clinching with brazing operation or modification of geometrical shape of the jaws

Open access

Frederik Stefanski and Bartosz Minorowicz

Abstract

This paper is focused on the open loop control of a piezoelectric tube actuator, hindered by a strong hysteresis. The actuator was distinguished with 22 % hysteresis, which hinders the positioning of piezoelectric actuator. One of the possible ways to solve this problem is application of an accurate analytical inversed model of the hysteresis in the control loop. In this paper generalized Prandtl-Ishlinskii model was used for both modeling and open loop control of the piezoelectric actuator. Achieved modeling error does not exceed max. 2.34 % of the whole range of tube deflection. Finally, the inverse hysteresis model was applied to the control line of the tube. For the same input signal (damped sine 0.2 Hz) as for the model estimation the positioning error was max. 4.6 % of the tube deflection. Additionally, for a verification reason three different complex harmonic functions were applied. For the verification functions, still a good positioning was obtained with positioning error of max.4.56 %, 6.75 %and5.6%of the tube deflection.

Open access

Konrad Łyduch and Wojciech Gęstwa

Abstract

The paper presents the influences of nanofluids, which are used in hardening process, to dimension changes, hardness and microstructure of hardened construction of steel samples. An analysis was also carried out with the use of English methods of cooling abilities of nanofluids environments based on water, solid nanoparticles of Al2O3 and ammoniac water. The results of this experiment show, that only one of specific dimensions of cooled samples, in the distilled water, changed for about 9%, but when using nanofluids this change was smaller. The hardness of alloy materials got a few percent more when nanofluids were used in comparasion to using the distilled water. The gained results allow to conclude the positive influence of nanofluids on parameters of the hardened materials.

Open access

Vladislav Kaverinsky

Abstract

Using an originally-developed computer model and appropriate software the impact of deformation on austenite phase transformation in low carbon alloyed steel was carried out. The computer simulation takes into account an impact of the deformation degree and takes into account non-constant cooling rate. That makes it useful for the development of thermal and deformation technological processes development. Based on the simulation results a technology of controlled rolling of low carbon steel alloyed by carbide forming elements (Nb, V, Ti) was developed. The proposed technique allows production of rolled steel sheets with high strength and plastic properties, as well as high impact strength in normal and low temperatures.

Open access

Agata Felusiak and Paweł Twardowski

Abstract

The present paper presents comparative results of the forecasting of a cutting tool wear with the application of different methods of diagnostic deduction based on the measurement of cutting force components. The research was carried out during the milling of the Duralcan F3S.10S aluminum-ceramic composite. Prediction of the toolwear was based on one variable, two variables regression Multilayer Perceptron(MLP)and Radial Basis Function(RBF)neural networks. Forecasting the condition of the cutting tool on the basis of cutting forces has yielded very satisfactory results.

Open access

Martyna Wiciak, Paweł Twardowski and Szymon Wojciechowski

Abstract

In this paper, the problem of tool wear prediction during milling of hard-to-cut metal matrix composite Duralcan™ was presented. The conducted research involved the measurements of acceleration of vibrations during milling with constant cutting conditions, and evaluation of the flank wear. Subsequently, the analysis of vibrations in time and frequency domain, as well as the correlation of the obtained measures with the tool wear values were conducted. The validation of tool wear diagnosis in relation to selected diagnostic measures was carried out with the use of one variable and two variables regression models, as well as with the application of artificial neural networks (ANN). The comparative analysis of the obtained results enable.

Open access

S. Islak

Abstract

In this study, wear properties of FeW-B4C coatings produced by tungsten inert gas (TIG) process on the AISI 1060 steel were investigated. TIG process was selected because it is a cost-effective approach for melting-based coatings. The treated surfaces were evaluated and characterized by means of scanning electron microscope (SEM), X-ray diffraction analysis, and electron dispersive spectrometry (EDS). The microhardness and wear experiment were also performed by using a microhardness machine and ball-on-disk tribometer. SEM observations showed that the obtained coating had a smooth and uniform surface. According to XRD analysis, borides and carbides phases formed in the coatings. The wear behavior of the coatings was compared with ball-on-disc configuration wear tests, at the same conditions. Average coefficient of friction values of the coatings were obtained at relatively low levels.

Open access

M. Piasecka, K. Strąk and B. Grabas

Abstract

The paper describes applications of the vibration-assisted laser surface texturing and spark erosion process as methods of modifying properties and structures of metal surfaces. Practical aspects of the use of produced surfaces in the heat exchanger with a minichannel have been described. Compared with smooth surfaces, developed metal surfaces obtained by vibration-assisted laser surface texturing and electromachining show more effective heat transfer. The local heat transfer coefficient for the saturated boiling region obtained for developed surfaces had the values significantly higher than those obtained for the smooth plate at the same heat flux. The experimental results are presented as the heated plate temperature (obtained from infrared thermography) and relationships between the heat transfer coefficient and the distance along the length of the minichannel for the saturated boiling region.

Open access

R. Bęczkowski, J. Wróbel and A. Kulawik

Abstract

In the paper, the regeneration process of the material in grade C45 using the MAG welding was analysed. The effect of preheating on the properties of the regenerated layers was determined. Preheating technology was used to facilitate the process of regeneration and minimize the risk of imperfections. The use of numerical methods allows one to observe the direction of changes in the properties, structures and emerging stresses and accompanying strains of the elements depending on the temperature applied for preheating. Modeling of the stress state in the element made of medium carbon steel during the regeneration process was performed on original software based on the finite element method. The implemented numerical model consists of three basic elements – thermal phenomena, mechanical phenomena and phase transformations in the solid state. The performed numerical analysis made determining the optimum heating conditions possible, so that the material in the area of joint didn’t show tendency to create structural notches associated with the stress state.

Open access

M.W. Richert, G. Boczkal, A. Hotloś, P. Pałka and M. Karpiński

Abstract

The effect of tribological wear of contacts made from an AgNi10 alloy on microstructure and electrical properties was investigated. The contacts were tested in duty cycles loaded with alternating current of 10A intensity. With this value of the current, intensive arcing of contacts occurred. The contacts were tested in the range of 125 to 500 thousand cycles. The contacting surfaces were reported to suffer a high degree of wear, but electrical resistance of the contact system remained stable.