Papers by Keyword: Surface Quality

Abstract: The article deals with peculiarities of restoration of steel parts by electrolytic Chromium-Plating depending on structural heterogeneity of worn surfaces. The possibility of assessing the quality of surface preparation for the process of Chromium-Plating by the results of measuring the thermal EMF in local areas of the restored surface is shown. A technological route of quality control in restoration of heavily loaded parts of gas turbine engines implemented in working environment is proposed.

Abstract: The purpose of the investigations carried out is the formation of qualitative nanostructured coatings and development of methods for their application on product surfaces. The principle of a staged study of regularities in the formation of vibration mechanical-chemical coatings from “top to bottom” and “bottom-up” formed a basis of a methodological approach to investigation carrying out. Experimental researches were carried out with the use of specially developed working chambers installed upon vibration machines. As an indenter there were used metal balls 2-5 mm in diameter and made of steel of ShH15 type, samples material – steel 45. The assessment of coating characteristics was carried out with the use of optical, raster scanning probe microscopy. It is determined through the result in the investigations of the impact-pulse interaction of a working environment part under conditions of vibration impact that there are grindings and changes in particles dimensions up to 100 nm and lesser in coating material which allows them to penetrate into micro-and nanocavities of basic metal and, in such a way, to form coating with high antifriction properties. The influence of amplitude-frequency properties of vibro-wave activation upon quality and performance attributes of coating surfaces and also process duration is determined.

Abstract: The effects of serials of electric parameters (i.e. electric pulsed current, electric pulse width, etc.) on machining speed and surface quality were investigated. Furthermore the selected parameters in electrical discharge machining (EDM) were optimized. Experiments indicate that the machining speed of EDM increases with the increasing of pulse current and pulse width. On the other side, the surface quality decrease with the increasing of pulse current and pulse width.

Abstract: Classical surveying of the machined surface quality is performed very often with using roughness profile recording by means of contact mechanical profilometer [4-7]. Also classical attitude to the profile run elaboration is to regard it as to a curve composed of the three main components: shape – treated mostly as deterministic, waviness – treated essentially as deterministic with some probabilistic component, and roughness itself – treated to as purely probabilistic. The question is: how to estimate this three components quantitatively and extract for individual evaluation. In our works we have developed methodical procedures of profile elaboration divided into three major steps: shape estimation and extraction with using polynomials of the order fitted to the evaluated profile, waviness estimation and extraction with using spatial filtering methods employing so called notch filters, statistical roughness estimation with using the set of tests and methods devoted especially to roughness runs of the purely probabilistic type. The notch filters are filters cutting out one, well determined spatial frequency λ₀ from the spectrum of frequencies related with investigated profile. The second but not less important advantage of this choose, was the phase characteristics of this filter, which tends rapidly to zero outside the “notch” band, not distorting unfiltered spatial signal. The width of cutting “notch” is controlled with using one independent variable Q. Our methodology is based upon cutting out a set of frequencies from the profile, tuned separately for to achieve as well reflection of the periodic impulse-like signal as possible, due to the well known theorem of decomposing physical, periodical signals into their harmonic components. In our researches we have employed the set of 8 filters providing us with good results even with profiles “scared” with substantial tracks of periodically acting tool. Of course, it is still possible to employ even greater number of filters, due to their low numerical complexness. Also the comparison has been performed with the profile not affected by waviness for to convince, that this type of filter simply do not affect the probabilistic roughness component. All of the profile elaboration stages have been checked due to their spatial spectrum with using classical tool – FFT transform of the roughness profile autocovariance function. As the major check of the proposed procedure correctness, i.e. proper extraction of the waviness component without disturbing of the statistical roughness parameters we assumed checking of the shape factor R_q/R_a before and after waviness extraction, which turned to be the same at the good level of accuracy. Our results, basing on simple and fundamental frequency analysis seems to be the good alternative to much complicated and time consuming analysis based on wavelet transforms in different forms.

Abstract: Abstract. The rapid prototypes of different printing temperature by Objet30 Stratasys Pro printer were found a certain difference in performance in the process of using the process.In order to studied the effect of printing temperature on the rapid prototyping of photosensitive resin, tensile and bending tests were carried out on the rapid prototyping parts at 12°C, 18°C, 21°C, 23°C, 25°C, 30°C,respectively,and the rigidity and surface roughness of rapid prototyping parts were measured.Research shows：the tensile strength increases with the increase of printing temperature , tensile elastic modulus fluctuates with the printing temperature , they all increases rapidly after 25°C;The bending strength increases proportional with the increase of printing temperature, and the bending modulus increases first and then tends to decrease with the increase of printing temperature;The hardness value increases slowly with the increase of printing temperature, and increases obviously after 20°C,the hardness value in the middle of the prototype parts is bigger than the edge parts；The surface roughness with increasing printing temperature, although it is floating up and down, but have little effect.

Abstract: In the sheet metal forming industry, tools are subject to mechanical, thermal, chemical and tribological loads. One of the major problems in forming operations of hot-dip galvanized sheet metal is galling (build-up of zinc flakes on the tool). This phenomenon develops gradually as an adhesion on the tool surface. The adhesive wear leads to high rejection and reworking costs for large car body forming tools. Due to economic aspects and the easy castability, the forming tools are made of cast iron. These materials tend to high adhesive wear. The aim of this project is to find a three-dimensional surface parameter, which describes a tribologically advantageous surface of forming tools in order to reduce galling. An additional objective is to optimize tool materials, heat treatment and surface coating. The evaluation of galling under laboratory conditions is based on strip drawing tests. The characterization of tool materials was executed for grey cast iron (EN-GJL-200/250) and nodular cast iron (EN-GJS-700). Investigations demonstrate that the processing methods and test parameters like sliding speed and temperature have a significant influence on galling. Three-dimensional surface parameters have also shown an effect on galling.

Abstract: The incremental forming of titanium alloy sheets combines the advantages of this advanced flexible manufacturing process, that allows to produce complex components without using dedicated tools, with the interesting properties of the material under consideration. In this study, thin sheets of grade 1 titanium were incrementally formed to evaluate their formability and surface quality by varying the tool-sheet contact conditions. Experimental tests and surface analyses highlight dependence on the contact conditions of the surface quality rather than of the formability. Moreover, they emphasize that the tool-sheet contact conditions mainly affect the repeatability of the process due to the occurrence of galling.

Abstract: With some conductivity and low grinding affectivity, a hybrid machining process termed electrical discharge diamond grinding (EDDG) is applied to the precision machining of reaction bonded silicon carbide (RB-SiC) ceramic. As there is electrical spark in the hybrid machining process, the electrical parameters are varied to explore their effects on the surface quality of RB-SiC ceramic with EDDG. In this paper, the experiments of different polarity and gap voltage with EEDG were investigated, and the microstructure and surface roughness on the machined surface of RB-SiC ceramic were analyzed. The surface morphology and micro-cracks were examined with a scanning electron microscope, and the surface roughness was measured with a confocal scanning laser microscope. It is found that surface roughness initially increases and then decreases with increase of the gap voltages and is higher with negative polarity than that with positive polarity. The micromorphology Micro-cracks were observed on the surface machined and are outstanding in re-solidified zone with EDDG.

Abstract: Si₃N₄ is difficult to be machined due to its hard and brittle nature. In order to improve its machining quality, a new method of ultrasonic-assisted laser machining is proposed. The machining device is established including Nd: YAG pulsed laser, ultrasonic vibration stage and water flow system. Etching experiments of laser machining with and without sample vibration in anhydrous conditions and in water conditions are studied respectively. A VM-3030E two-dimensional image measuring instrument is applied to detect shape and measure dimension of the sample. Microstructure morphology of the sample is observed by a JSM-7500F scanning electron microscope. Experimental results show that there are fewer slags on inner surfaces of V-shaped grooves when laser machining with water flow. The surface quality and depth-to-width ratio of grooves machined by laser with vibration on sample are improved significantly in comparison with those without vibration. The depth-to-width ratio of groove machined by laser with 90.1W vibration power is near twice than that without vibration.

Abstract: For optimization and control of the grinding process, it is necessary to monitor the process state. Fluid selection for grinding process is also considered as key factor for surface quality. This study focuses on the effects of different fluids in grinding process using Acoustic Emission technology. The analysis is carried out grouping the tests according to the main measured: Acoustic Emission (AE) signals, Normal and Tangential Forces on the workpiece surface, Grinding Temperature and Surface Roughness. The potential of real-time monitoring grinding process using Acoustic Emission technology is also tested. The results of this research show that selections of grinding fluids do have a significant influence on response factors such as surface roughness and AE signals. Further, prediction of surface roughness during the grinding process using AE signal monitoring is demonstrated in this work.