Key Engineering Materials Vol. 572

Abstract: Tool presetter is a type of precision measuring instrument that associates to CNC machine tools and machining centers, which integrates the technologies of optics, mechanics and electrics all together, and its measuring accuracy gives direct influence on machining accuracy of CNC machines. The main factors that influence measuring accuracy of tool presetter include: image edge detection, image positioning and accuracy of its mechanical system. This paper gives analysis on these main factors and puts forward three newly developed algorithms for improving measuring accuracy of tool presetter. First algorithm is image edge detection algorithm based on subpixel that increases the edge positioning accuracy by more than 10 times. Second one is uniformity compensation algorithm for whole view measurement that is able to capture accurate real pixel size so that image movement is more precise, which further increases the measuring accuracy. The third one is linear compensation algorithm in the measuring space that makes effective compensation to the mechanical system errors, which can compensate any position in measurement space so that system accuracy increases significantly. These algorithms are tested in CoVis software and the results show that the total measuring accuracy of tool presetter is improved dramtically to 2 μm.

Abstract: This paper presents results of theoretical and experimental research works on metal forming process of a hub. A typical technology of forging on hammer of this part with flash was discussed. Two new processes of a hub forging were proposed, characterized by large material savings in comparison with typical technology. The first process is based on forming without flash of a forging with axial cavity. The second one is connected with forming of forging from pipe billet. The realization of these processes is possible at the application of a press with three movable working tools. Theoretical research works were done on the basis of simulations by means of finite element method. Simulations were made mainly in order to determine kinematics of material flow in forging processes and precision of shape and dimensions of obtained products. The first of the proposed processes was experimentally verified and a product of good quality was obtained. Material consumption of the analyzed processes and other factors acting on their effectiveness were also compared.

Abstract: The use of tube hydroforming in manufacturing is increasing in popularity, particularly in automotive applications where it offers numerous cost and well-recognized performance advantages over conventional stamping and welding processes. In this paper, the use of indirect Additive Tooling is explored in the creation of tool inserts to be used in the production of exhaust manifolds for the automotive industry. The principal focus of this research concerns the identification of operational issues arising from the exploitation of Additive Tooling, together with the suggestion of a number of techniques and solutions which may be applied to mitigate the problems inherent in the rapid manufacture of tube hydroforming tools.

Abstract: Unstructured finite volume method applied in structural static mechanics has been discussed to direct at the difficulty of dealing with irregular boundary, unstructured triangle elements have been used in computational domain, the basic equations of unstructured finite volume method applied in structural static mechanics has been deduced. Comparing the unstructured grids with the structured grids, the former has obvious advantage on dealing with irregular boundary by theoretical analysis. According to examples analysis, the comparison of numeric results with analytic solutions and FEM solutions showed the effectiveness of the unstructured finite volume method.

Abstract: In order to improve the self-lubricating and anti-wear performances of metal surfaces in the extreme conditions, Sn-Ni-PTFE composite coating was electrodeposited on metal surfaces from the electrolyte containing PTFE emulsion. Microstructure, microhardness and tribological properties of the Sn-NiPTFE composite coatings were investigated. Results show that Sn-Ni-PTFE composite coating has smooth surface and fine microstructure. PTFE particles disperse uniformly in the composite coatings. Simultaneously, the incorporation of PTFE particles significantly improves the tribological performance of Sn-Ni coatings. SnNiPTFE composite coatings exhibits lower friction coefficient and better wear resistance in contrast with Sn-Ni coating.

Abstract: The surface topography errors of micro-EDM are mainly composed of surface roughness, surface waveness and so on. Research shows that the surface morphology provides a lot of useful information, which has serious influence on the friction and lubrication characteristics of the surface. However, for the micro-EDM surface topography evaluation problem, researchers have been using surface roughness parameters and evaluation method of mechanical process, which restrict the micro-EDM technology further development. On this account, the surface roughness parameters of micro-EDM have been deeply studied in this paper according to its technology characteristics and the surface morphology characteristics, therefore, the main researches and creative points are obtained, which the influence that the surface roughness of micro-EDM parts impact on their using performance is analyzed, and based on the surface morphology characteristics, some roughness evaluation parameters are given respectively according to peaks and valley, moreover, their numerical calculation are also gained.

Abstract: Amplitude parameters and functional parameters of three-dimensional roughness are established by statistics geometry. Since micro wire electric discharge machining (MWEDM) surface approximately follows the Gauss distribution, its statistical characteristics are different from cutting processing surface. Characterization meaning between MWEDM surface and cutting processing surface is rather different. This study begins with shape parameters’ mathematics essence of surface height distribution of three-dimensional roughness, analyzes their definite characterization meanings for MWEDM surface, deeply researches bearing ratio curve of MWEDM surface, reasonably ascertains its functional areas and finally establishes nine functional parameters where volume parameter is the main one.

Abstract: Since 3D micro-topography of the Micro Wire Electrical Discharge Machining (MWEDM) surface is an isotropy surface which is composed of innumerable ellipsoid profile peaks and pits, shape and distributing characters of surface structure can bring direct influence on characterization precision or calculating method of 3D roughness parameters, which needs considering surface measure direction or is influenced by surface structure. Through researching structural characters of 3D micro-topography of MWEDM surface, this article improves arithmetic method of space parameters of 3D roughness influenced by structure, which predigests calculating process and advances calculating precision.

Abstract: The paper proposes mechanism of electrochemical discharge ECD based on the results of experiments in stagnant electrolyte cell (SEC). The experiments conducted in SEC have demonstrated that the physical characteristics of ECD, instantaneous current wave form (ICWF) in the cell at the time of discharge and voltage gradient developed near the tip of the discharging electrode are polarity dependant. It has been also observed that the formation of gas-vapour sheath round the tip of electrode is the benchmark leading to the discharge. Hence, an attempt has been made to suggest the polarity dependant ionization processes that can take place in the gas-vapour sheath near the discharging electrode, assuming that the ionic processes taking place at the electrodes in an electrochemical cell do not change at the time of discharge. The emission of electrons can take place from the surface of cathode due to either the field emission or thermionic emission (since the temperature of cathode shoots up in the film boiling regime) or by positive ion impact. The field ionization of gas molecules in the sheath formed around the anode tip can take place leading to tunneling of electrons from neutral gas molecules under the action of high electric field (2-510¹⁰V/m) [1] into the surface of the anode.

Abstract: A new rule extraction algorithm based on convex hull for strip hot-dip galvanizing process monitoring is proposed in this paper. It overcomes the black-box problem of support vector machine. The zinc coating weight is used as the investigated subject. The sample datasets are trained by support vector machine rule extraction method, and the quantitative relationship can be obtained in the form of knowledge rules among input variables (such as the parameters of raw materials and control parameters of production) and output ones (the quality parameters), with which the production control parameters can be set and updated easily.