Papers by Keyword: Burnishing

Abstract: This study evaluates the effect of the vibration assisted ball burnishing method on surface integrity of maraging C300 steel surfaces printed by additive manufacturing with Selective Laser Melting (SLM) technology. The analysis contemplates variations in tool preloads and applied force. The analyzed C300 material is based on the as-built (AM), machined (M) and vibration assisted ball burnishing (VABB) states. Surface roughness was evaluated to assess topographical conditions both before and after the burnishing process. Microstructure and mechanical deformation were analyzed by Scanning Electron Microscopy (SEM) technique to examine the stresses generated by compression effect. It was found that forces in the range of 180 to 220 N reduce the roughness Sa value by up to 59% with respect to the M finish and up to 97% with respect to the AM finish. Furthermore, burnishing parameters significantly vary the final quality of the surfaces depending on the initial state of the surface and the conditions of the material.

Abstract: This study aims to evaluate the functionality and effectiveness of a new tool for ironing 3D printed components using FDM technology. The ironing process draws inspiration from the ball burnishing process, employing a spherical tool that, by exerting pressure, modifies the component's surface. The process involves heat transfer between the tool and the component to soften and deform the surface more easily. A theoretical analysis of the resulting surface roughness following this process was conducted to identify the parameters at play and their influence. It was found that the two main parameters are the fillet radius and the distance between passes. Additionally, practical tests were carried out to confirm the hypotheses, revealing the influence of three other parameters: tool Z-axis positioning, temperature, and movement speed. The surface after treatment exhibits an average roughness of Ra = 0.378 μm, significantly better than values obtained with ironing performed with the nozzle and with quality comparable to grinding. This lays the groundwork for possible future optimization of parameters based on the component's characteristics and the material used.

Abstract: Nowadays, the increased average age of patients and the decreased age at which arthroplasty is carried out represents a reason for the necessity of higher quality standards for prostheses. In particular, tribocorrosion generates an irreversible transformation of the materials and the release of particles and metal ions in toxic concentrations in the biological environment in which the systems are implanted. One of the most used materials for prosthetic implants is the Ti6Al4V alloy but its tribological behavior is still challenging for the application. Employing and optimizing severe plastic deformation processes represents a way to obtain prostheses with superior performance improving patients’ quality of life and reducing the burden on National Health Cares. Ti6Al4V bars have undergone machining with semi-finishing parameters and burnishing processes. Tribocorrosion tests have been performed in a custom-made cylinder-on-disk configuration employing Al2O3 counterparts and phosphate buffer solution with the addition of albumin as simulated body fluid. The effects of sole machining and its combination with burnishing on surface quality and specific wear rate (SWR) have been assessed with respect to as received surface conditions. Optical microscopy, stylus profilometry and sample weighing before tests and at specific intervals during the tests have been employed for characterization. As a main result, it has been found that burnishing process is able to improve SWR of Ti6Al4V samples with respect to both as received and machined samples. Furthermore, the overall behavior of tribological system is gradually improved first employing sole machining and then combining machining and burnishing, reducing SWR of counterparts as well.

Abstract: The paper presents the results of the computer modelling of the stressed state and relative density when burnishing a porous hollow cylinder, made from copper sintered powder material. The mathematical model, based on the theory of porous bodies’ plasticity, is used for the analysis. The paper researches the impact of the initial porosity of the material on the effective stresses distribution, relative density and force change when free burnishing of hollow cylinders. It is ascertained that with the decrease of the initial porosity of the sintered material there is the increase of the burnishing force, stresses rate and relative density on the inner sur-face of a hollow cylinder. For porous materials at a certain stage of burnishing, the deformation zone is transformed into the compaction zone with a high relative density which de-creases while moving away from the inner surface of hollow cylinders. The maximum value of the relative density is implemented directly on the inner surface of hollow cylinders; along with this the density value is evenly distributed on the inner wall.

Abstract: Article explains manufacturing capability of titanium parts reliability enhancement and life cycle enhancement by electrospark deposition using low energy discharges. Carbon electrodes used to form functional properties of parts surface layer. Alloyed carbooxide zone consist of highly dispersed structure (with particles of titanium carbide, titanium oxide, graphite), with 3-10 micron thick, and high hardness antifrictionality. Alloyed layer contain ordered phase Ti₈C₅, TiC, and the structure of Ti₆C_3,75. Parts dimensions almost do not changed after electrospark deposition with carbon electrodes. Subsequent diamond burnishing decrease friction coefficient and surface roughness. Fatigue resistance increased after healing of defects and microcracks. Local carbooxidation and burnishing used to increase wear resistance of titanium alloys.

Abstract: Slide-burnishing is one of the most powerful processes for microstructural evolution. Here slide-burnishing was performed by a cemented carbide ball loaded and fed on the flat surface of a rotating disk specimen of carbon steel using a lathe machine. This process provides many advantages: burnishing reduces the surface roughness, increases the surface hardness due to grain refinement, improves the wear resistance, and requires no special equipment. Transmission electron microscopy (TEM) observation revealed that nano-crystalline structures in the 10–300 nm grain size range were formed at the burnished sub-surface layer and that grain size increased approximately linearly with depth below the surface due to the strain gradient. High rotation speed in the burnishing process prompted further grain refinement, as evidenced by ultrafine and equiaxed grains in the 10 nm size range at the top surface layer of the specimen burnished at the highest rotational speed. Burnishing increased the indentation hardness of the nano-crystalline layer by a factor of 3.5. The expected linear relationship between hardness and inverse square root of grain size was identified.

Abstract: This paper provides a framework for the transcription of the surface of a mirror-finished die onto a metal plate by friction stir forming (FSF). In FSF, a material is put on a die, then friction stirring was conducted on its back surface for the transcription of the profile of the die onto the material. In this paper, a mirror-polished die of JIS SUS304 stainless steel with surface roughness Sz 0.014 mm and a probe-less friction-stirring tool in 18 mm shoulder diameter were employed for the experiment. A5083P-O aluminum plates, 3 mm thick, were utilized as base metals for the transcription. The authors varied tool spindle speed and tool feed rate to evaluate the forming results. Consequently, a mirror-finished surface under the friction-stirring tool was successfully transferred from the die to the aluminum alloy plate. The roughness of the base metal before processing was Sz 0.022 mm and that of the processed metal was Sz 0.012–0.016 mm. Higher spindle speed and faster feed rate resulted in a smoother surface; it is thought that high spindle speed and faster feed rate should be effective for higher contact pressure between a die and a material.

Abstract: Over the past decades the science of friction has got great development. Processes of friction and wear significantly depend on constructive junction design, selection of wear resistant materials and effective lubricants for them, as well as the conditions of the machinery operation. Currently, a large number of scientific works [7-11, 16-20] are devoted to the review of the contact interaction conditions with the use a lubricant. The method of elastohydrodynamic lubrication is of particular interest when studying different kinds of lubrication. According to the elastohydrodynamic lubrication theory, contact conditions of two elastic bodies are characterized by high pressures which cause the elastic deformation of solids and by the dependence of a lubricant viscosity from the pressure. When using the elastohydrodynamic lubrication the layer profile, the sum amount of elastic deformations, elastic deformations and the lubricant viscosity dependence from pressure are given by set equations [12-15]. The impact of elastohydrodynamic lubrication method on the surface layer of the contacting parts is of great interest.

Abstract: It is advantageous to use the method of surface plastic deformation in order to get high-quality surfaces that meet increased requirements for strength and reliability. For efficient process of surface plastic deformation, it is required to define a set of conditions to provide minimum roughness of a machined surface. The paper addresses the problem of experimental search of optimal burnishing modes using the simplex design to minimize roughness of a machined surface. The significance of variable factor ranking was observed for this technique. A specific set of tests resulted in decrease in the initial surface roughness almost by 15 times in the specimens made of aluminum alloy after burnishing with the steel indenter. It was established that the surface quality was significantly affected by a new factor – angle of indenter contact with the machined surface, which had a damping effect on the machine-fixture-tool-workpiece system. The experiments showed that polished indenter balls significantly lowered the roughness grade of the machined surface under the same conditions.

Abstract: Burnishing as a forming finishing process enables the production of precise and mechanical compressed surfaces. The forming operation can be easily integrated into cutting processes due to its kinematic similarities. Through this integration it was possible to create highly efficient process chains for the machining of rotational symmetrical parts. The formed surface qualities are also interesting for prismatic geometries, but the adaptation of this force controlled process is challenging, because of its multiaxial characteristics. A main limiting factor for burnishing on plain surfaces is the formation of a burnishing bulge on the edges of the burnished area. Several investigations of the process on plain surfaces where done to analyse the bulge formation characteristics of the aluminium EN AW-2007 material. Experiments of different single burnished paths and burnished areas with the subsequent 3D capturing of the created surfaces were done. The investigations show, that the deformation is highly dependent on the applied burnishing force and the burnishing feed. The length and width of the burnished area does not have an influence on the bulge formation.