Papers by Keyword: Roughness

Abstract: Electro erosion is a manufacturing process designed for machining difficult-to-process materials. This paper presents the fabrication of a miniature punching die used for perforation and cutting, made from X15 steel, using electro erosion. Due to its properties, such as high hardness, complexity, and the need for protection against surface layer damage, this material cannot be processed with conventional methods. The electro erosion process ensures high quality and dimensional precision in the finished product. A digital surface roughness meter and the functional schematic of the PGI system are also discussed. Various roughness measurement techniques are presented, along with graphical representations and the bearing area curve. The paper highlights variations in parameters at four measurement points, as well as changes in the "c" coefficient. Finally, the surface roughness parameters Ra, Rq, and Rz are analyzed.

Abstract: Skin-pass rolling is commonly used to adjust the surface quality of high-strength aluminum alloys. Lubrication plays an important role in this process, as it minimizes material adhesion to the work roll, extends its service life, and also influences the contact conditions and the final surface topography. However, most numerical studies represent lubrication only through an effective friction coefficient. In this work, a finite-element framework that explicitly accounts for lubricant entrapment in engineered surface pockets by using a coupled Eulerian-Lagrangian (CEL) approach is introduced to investigate lubricant-topography interaction. The skin-pass rolling process is approximated by a plane-strain upsetting test to represent the parameters relevant for mapping the interaction between lubricant and mechanical stress, as the rolling process has a large number of influencing factors. The precipitation-hardenable aluminum alloy EN AW-6016 is modeled with rate-dependent plasticity based on experimental flow curves, while the lubricant is represented as a Eulerian material governed by an equation-of-state formulation. The effects of strain rate, friction and different lubricant filling levels in surface pockets are analyzed. The results show that variations in friction mainly affect the global force level, while the presence of lubricant leads to changes in local deformation and stress distributions. Fully filled pockets require higher forming forces due to lubricant compression, whereas partially filled pockets show behavior close to dry conditions. The CEL approach proves suitable for modeling lubricated plane-strain upsetting tests and provides a basis for further investigations of lubricated skin-pass rolling processes.

Abstract: Titanium scaffolds produced by additive manufacturing were studied using the scanning electron microscopy (SEM) and the confocal optical microscopy (COM). The previous research has shown that the titanium scaffolds with porous filaments (14 % porosity) exhibited markedly better fatigue resistance than those with compact filaments (6 % porosity). This article is devoted to macroscopic and microscopic images of fracture surfaces of both types of scaffolds after cyclic compression (CC) tests and after cyclic three-point bending tests (CTPB). A high density of cracks and broken filaments was indicated particularly in scaffolds with porous filaments. The fatigue crack growth was highly affected by the microporosity. Fracture facets were smaller and rougher for the porous filaments compared to the compact ones. Values of roughness parameters S_a and S_v for porous filaments were significantly higher than those for compound fibres. Both SEM and COM studies confirmed an important role of crack-pore interactions especially in the porous filaments.

Abstract: Currently, one of the most used electrodes are brass wire electrodes, which, thanks to their good electrical conductivity, suitable mechanical properties and acceptable performance, can meet the high demands placed on the cutting tool. A special type are coated wire electrodes, which include a range of specifics regarding machining efficiency and the quality of the machined surface. Therefore, the aim of the research was to identify these parameters based on the experiments carried out in connection with the quality of the machined surface and the productivity of the electro-erosive process in the machining of high-speed steels. The influence of a standard brass multipurpose wire electrode and two brass wire electrodes coated with a double layer of gamma diffuse zinc and zinc alloy on the quality of the machined surface and the productivity of the EDM process was investigated.

Abstract: Besides conventional shaping methods like injection molding and extrusion, various additive manufacturing (AM) techniques have been steadily gaining prominence due to the numerous benefits they offer. These advantages include swift and uncomplicated shaping, the capability to produce components with intricate geometries during both the design and production phases, manufacturability enhancements, and cost-efficiency.In the context of the automotive industry, components produced often need to adhere to stringent standards. When it comes to these manufactured parts, the precision of processing and the quality of the surface represent the paramount complex metrics that dictate the performance attributes of the specific part.The surface roughness of parts produced by 3D printing depends on many factors: from CAD to stl (standard triangular language) conversation and from the chosen method, layer thickness, printing speed, printing temperature.It can be done surface modification by different methods: application of coatings, surface modification procedures (chemical, e.g. etching, physical, e.g. chipping (milling, turning), ironing (software based method)The surface roughness depends also the place of the investigation: Horizontal or vertical walls, sloping surfaces. Surface roughness also varies on the same surface by changing slope due to the staircase effect.Moreover the surface roughness depends on the method of the investigation parallel or perpendicular to the layers and the printing or infill direction.In the last two cases it should be a good choice to use S_a which is the extension of Ra (arithmetical mean height of a line) to a surface. It expresses, as an absolute value, the difference in height of each point compared to the arithmetical mean of the surface.In this paper, we explore this issue

Abstract: A mechanical work piece created industrially frequently contains more than one machining process. Furthermore, it is a common activity of programmers, who make this selection every time a milling and drilling operation is conducted. Tool wear and borehole quality are two essential challenges for high precision drilling procedures, with Al 356 alloy being employed in experimental planning. Drilling specifications will be assessed in this work to get optimal parameters in minimizing the influence of drilling damage on alloy using a swarm-based optimization model. The drilling parameters are optimized using the Bacterial Foraging Optimization (BFO) method, which includes three control factors: depth, feed rate, and spindle speed. Each parameter is designed in three levels, with multiple performance characteristics such as thrust force, surface roughness, and delamination factor. This investigation was carried out in order to obtain the proper optimization. The feed rate, next to the spindle speed, was discovered to be the essential element inducing lamination in drilling, with this phenomenon occurring in each diameter of the drill bit. The results reveal that the feed rate and drill type are the most important parameters influencing the drilling process, and that employing this strategy can successfully improve drilling process outcomes.

Abstract: The article presents some new theoretical and experimental solution of a scientific and applied problem of technological support for vibratory centrifugal processing of complex-profiled parts in a bulk abrasive environment. This solution aims to increase productivity while ensuring the desired quality of the processed surfaces. The authors have developed a mathematical model that describes the action of abrasive particles on the surface of the parts, taking into account the parameters of the granular abrasive medium based on Voigt’s law. This allows the description of dynamic processes in the processing environment for a wide range of material types. The natural frequencies of oscillations of the processed medium layer have been determined, which depend on the amplitude of its vibrations for different densities of soft and hard materials of the processed medium and the medium with linear-elastic properties. The methodology includes the use of test equipment to conduct experimental research on the process, which involves determining changes in specific metal removal rates and surface roughness using the frequency converter Altivar 71 with the PowerSuite v.2.5.0 software.

Abstract: In the article, the influence of the surface roughness of the printing plate on the thickness of the ink layer on the surfaces of the cylinders of the printing apparatus during ink transfer was studied. An analysis was made of the works devoted to the contact of the cylinders of the printing apparatus, as well as to the ink transfer and division of the ink layer. The influence of the surface roughness of the printing plate on the thickness of the ink layer, which ensures the quality of prints, has been established. A technique has been developed for determining the thickness of the ink layer, consisting of two stages, taking into account the roughness of the surface of the printing plate. At the first stage, the thickness of the ink layer on the printing plate after rolling, but before contact, was determined, and at the second stage, the thickness of the ink layer was determined on the offset blanket (deckle) after contact between the plate and offset cylinders. The thickness of the ink layer on the surfaces of the cylinders of the printing apparatus was estimated by the gravimetric-weight method. To estimate the amount of ink, the printing plate was weighed three times - before applying ink, after applying ink - before contact and after contact with the deckle. The difference in weights made it possible to have an idea of the mass of paint on the surfaces of the cylinders. On the basis of the experimental results obtained by the proposed method, the values of the thickness of the ink layers on the plate (on the form) and on the offset cylinders (on the deckle) were determined, taking into account the surface roughness of the printing plate. It has been established that at high roughness values, the amount of paint increases, which increases the thickness of the ink layer. The obtained results of the thickness of the ink layer on the deckle make it possible to determine the technologically necessary thickness of the ink layer on the print, which is the main factor for ensuring print quality. Taking into account the values of the surface roughness of the printing plate, it is possible to determine the technologically necessary pressure in the contact zone of the cylinders, which is an important factor for ensuring the technologically necessary thickness of the ink layer on the print. The results of the studies show that the data obtained are significantly different from the results of similar studies on the division of the ink layer between the cylinders of the printing apparatus and are more accurate, which is important for setting up the printing machine and ensuring the quality of prints.

Abstract: Electropolishing has been widely used for surface finishing of metallic products in the industry, owing to its excellent capability of producing metallic components with a homogeneously smooth surfaces. However, this treatment is often constrained by the long duration required for the processing. Therefore, an improvement in this process is needed. The aim of this research is to introduce the use of electropolishing with circulated electrolytes for improving the surface finish of brass. In this work, electropolishing was carried out by using circulated H₂SO₄ electrolyte for 10 to 30 min in a customized electropolishing chamber. The effect of this treatment on surface morphology, surface roughness, and thickness reduction of the brass specimen was determined. The results showed a better capability of electropolishing with circulated electrolyte in decreasing the brass roughness, i.e., by 84%, than that without electrolyte circulation which only reached 45% during 30 min of the treatment.

Abstract: This paper reports on the mechanisms and provides worked examples of using pulsed electric current to improve the surface properties of conductive materials during solidification. A rough surface is formed via the freezing of thermomechanical fluctuations and external disturbances during solidification. Pulsed electric current provides an extra driving force for the fluctuations to relax in a shorter duration toward the equilibrium state before the material loses the fluidity during cooling. This additional mechanism is associated with the electric current free energy, which depends on the current density distribution at various materials geometries, including the surface profile. The mechanism has been validated by experimental characterization of the surface roughness evolution with and without electropulsing treatment.