Robert Koteras, Michał Wieczorowski, Piotr Znaniecki and Natalia Swojak
The purpose of the article is to show the practical side of reverse engineering.Many times during the process of optimizing parts, before we intervene in the tool that produces them, we want to makesure that the optimization will work in practice.For this purpose, currently, we often use 3D printers. Unfortunately, they introduce distortions of geometry to the printed prototyperesultingfrom the technology of its production.
Demand for thin-walled structures has been increasing for many years. Cold- formed, thin-walled channel beams are the subject of presented research. The local elastic buckling and limit load of these beams subjected to pure bending are investigated. This study includes numerical investigation called the Finite Strip Method (FSM). The presented results give a deep insight into behaviour of such beams and may be used to validate analytical models. The number of works devoted to the theory of thin-walled structures has been steadily growing in recent years. It means that is an increasing interest in practical methods of manufacturing cold-formed thin-walled beams with complicated cross-sections, including also beams with web stiffeners. The ratio of transverse dimensions of beam to its wall-thickness is high, therefore, thin-walled beams are prone to local buckling that may interact with other buckling modes. The stability constraints should be always considered when using cold-formed thin-walled beams.
Krzysztof Jarosz, Piotr Niesłony and Piotr Löschner
In this article, a novel approach to computer optimization of CNC toolpaths by adjustment of cutting speed vcand depth of cut apis presented. Available software works by the principle of adjusting feed rate on the basis of calculations and numerical simulation of the machining process. The authors wish to expand upon this approach by proposing toolpath optimization by altering two other basic process parameters. Intricacies and problems related totheadjustment of apand vcwere explained in the introductory part. Simulation of different variant of the same turning process with different parameter values were conducted to evaluate the effect of changes in depth of cut and cutting speed on process performance. Obtained results were investigated on the account of cutting force and tool life. The authors have found that depth of cut substantially affects cutting force, while the effect of cutting speed on it is minimal. An increase in both depth of cut and cutting speed affects tool life negatively, although the impact of cutting speed is much more severe. An increase in depth of cut allows for a more significant reduction of machining time, while affecting tool life less negatively. On the other hand, the adjustment of cutting speed helpsto reduce machining time without increasing cutting force component values and spindle load.
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.
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.
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.
Nikodem Wróbel, Michał Rejek and Grzegorz Królczyk
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
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.
Martyna Wiciak, Paweł Twardowski and Szymon Wojciechowski
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.
This paper presents research on the accuracy and repeatability of CNC axis positioning in an innovative lathe with an additional Xs axis. This axis is used to perform movements synchronized with the angular position of the main drive, i.e. the spindle, and with the axial feed along the Z axis. This enables the one-pass turning of non-circular surfaces, rope and trapezoidal threads, as well as the surfaces of rotary tools such as a gear cutting hob, etc. The paper presents and discusses the interpretation of results and the calibration effects of positioning errors in the lathe’s numerical control system. Finally, it shows the geometric characteristics of the rope thread turned at various spindle speeds, including before and after-correction of the positioning error of the Xs axis.