Papers by Keyword: Surface Quality

Abstract: Incremental sheet forming is a viable method for manufacturing highly customized components from non-conventional materials. Among these, niobium is a metal of growing interest due to its potential in various technological applications. In this experimental study, the incremental forming of high-purity annealed niobium sheets was investigated, with particular attention given to the surface finish of the formed parts. To this end, the surface morphology of the components, specifically fixed wall conical frusta, and the forming forces were analyzed. The results indicate that, despite the material’s notable formability, the incrementally formed niobium surfaces exhibit poor quality. This is attributed to the unique properties of niobium, suggesting that the development of surface treatment strategies is advisable to improve this aspect.

Abstract: Laser powder bed fusion (PBF-LB) technique can currently offer the lowest surface roughness among all available techniques for metal additive manufacturing. Still the measured values for R_a can easily be over 10 μm depending on the used layer thickness and printing parameters. The current work focuses on improving the surface roughness by utilizing dry electropolishing machine. While suitable for many materials, the material selected for this study is one of the most used in PBF-LB manufacturing, stainless steel 316L. In addition, multistep pre-grinding with the grade of the final finish varied was used to investigate what is the most efficient way to distribute manual preparation work and automated polishing to reach the desired surface roughness. Furthermore, severe shot peening was used before the polishing to study the effect on residual stresses and fatigue life of the material. Laser optical microscopy was used to investigate the surface properties and it was found that dry electropolishing with pre-grinding could be succesfully used to obtain average roughness levels as low as 0.13 μm. The highest reductions in surface roughness were reached with the rougher initial surfaces where it could be reduced by 80% at best. Residual stresses measured after the severe shot peening were preserved after the polishing but did not result in increased fatigue strength.

Abstract: Fused Filament Deposition (FDM) additive manufacturing technology allows the generation of three-dimensional parts by overlapping layers of an extruded polymer. The staircase effect caused by overlapping is well known and makes the manufactured parts have poor surface quality. This problem has been focused on by numerous works trying to optimize the surface quality by studying the process technological parameters or part geometry. Also, post-processing techniques have been developed that improve this roughness, but which involve an increase in manufacturing time and cost. In this work, a methodology to measure the roughness based on laser confocal microscopy is proposed. To evaluate the methodology, an experimental study is carried out that relates the surface roughness of parts manufactured with FDM with the building orientation and the layer height. The main objective of this study is to compare two roughness measurement methodologies: a mechanical measurement with a conventional contact roughness meter, and an optical measurement with a confocal microscope. The contact roughness meter provides a direct value of the roughness of the part wall profile, while the confocal microscope provides an image of the three-dimensional surface of the part wall, which must be processed. The data from the confocal microscope are evaluated with the Internet-based software Surface Metrology Algorithm Testing System (SMATS) developed by the National Institute of Standards and Technology (NIST) of the USA. The SMATS will provide an average value of the roughness of the analyzed surface. The test results with both methodologies are very similar, with an average difference of 5%. These results show the influence of the printed plane inclination angle on the roughness, which is higher for low values of the angle. It can also be seen that this influence decreases for low-layer heights.

Abstract: The use of advanced materials in new fields of applications is usually related with specific properties and great advantages. However, it may become an important technological challenge for the manufacturing and joining of these materials. Carbon Fiber Reinforced Plastic (CFRP) is widely used in aerospace or automotive industry, but currently is starting to be used as structural component in the building industry. In contrast to the thin parts developed for aircraft. the elements for construction are characterized by high thicknesses. This fact increases the abrasive effect of carbon fibre on cutting tools when it is machined by conventional processes. For this reason, non-conventional technologies. as Abrasive Water Jet Machining (AWJM), could be a suitable technology for this purpose. An operation of great interest for these materials is drilling. The industry demands the drilling of a wide range of increasingly large diameters. This, in combination with large thicknesses in CFRP, makes the machining process more difficult. Technologies such as orbital drilling are limited by the range of diameters that can be obtained and the abrasive wear between the material and the cutting-tool. Therefore, the use of abrasive waterjet cutting is proposed as an alternative technology capable of machining diameters in a wide range. One of the main limitations for the use of AWJM on large thickness parts of CFRP comes from the surface finish of the machined surfaces. where high values of roughness can be found. In this research, the effects of water jet cutting parameters have been evaluated for the machining of 17 mm thickness CFRP specimens. By variations on the traverse speed. abrasive mass flow rate and hydraulic pressure. differences in the performance and micro-geometrical characteristics of the machined surfaces were obtained, allowing to identify most significant affecting parameters of the process.

Abstract: Thin profile wires made of stainless steels are widely used for production of industrial screens used for filtration and separation processes. Industrial screens made of resistance spot welded thin profile wires are used e.g. in baskets for centrifuges or filtration screens and find a wide range of applications in various branches of the industry (mining, food and sugar industry, paper industry, wastewater treatment, oil and gas and many more). Regardless of the application, increased durability and surface quality of the screens is of paramount importance. Improvement of the longevity of manufactured items, process efficiency and environmental performance can be achieved only when interactions between initial wire rod quality and its susceptibility to metal forming operations are fully understood. Due to the complexity of the manufacturing process of industrial screens (precise and small gaps, narrow ranges of dimensional tolerances), forming of thin, so-called precision profiled wire is difficult. The influence of the charge, i.e. wire rod, parameters of the wire drawing / rolling process play a key role in obtaining semi-finished products characterized by high strength, low surface roughness and a low level of residual stresses. The paper discusses the influence of the initial state of wire rod and deformation parameters on the quality of thin austenitic and lean duplex steel profile wires as well as the possibility of replacing austenitic wires by lean duplex wires and their possible benefits.

Abstract: Poor fatigue life is a huge issue of additively manufactured parts, despite the unique qualities characterizing this manufacturing process (such as low waste of material and geometry freedom). Fatigue life is strongly affected by both surface defects and internal defects, metal AM is characterized by extremely poor surface quality, internal porosities and lack of fusions. For this reason, many researchers investigated methods to improve manufacts quality. The most promising methods are surface finishing treatments and thermal treatments which provide an enhancement of fatigue behavior. A focal point of the research should be evaluating the respective contribution of surface treatments and thermal treatments. In order to evaluate the effectiveness of surface treatment, it is necessary to highlight the surface quality contribution in terms of fatigue life thus a specific testing method is necessary. Rotating beam fatigue test fits this requirement because each point of the specimen’s surface is subjected to the maximum stress. The aim of this work is to present the experimental setup for rotating beam fatigue testing that has been used to evaluate the fatigue behavior of AM SLM IN718 specimens.

Abstract: Resin Coated Sand (RCS) is an important raw material for the Shell mould process. This research aimed to study the effect of silica content on the surface quality of cast iron in the shell mould process. The four kinds of sand are Australian sand, Rayong sand, Reclaimed sand and River sand. All sand was mixed with phenolic resin for making Resin Coated Sand. The chemical composition of sand was tested by X-Ray Fluorescence. The result found that the SiO₂ content of each sand was different. The SiO₂ content of Australian sand 99.8%, Rayong sand 98.6%, Reclaimed sand 90.3% and River sand 89.2%. The morphology from the microscope was found that sand grains exhibited different shapes that affect mechanical properties such as bending strength and thermal expansion of Resin Coated Sand. The qualification of Resin Coated Sand is bending strength and thermal expansion from Australian sand is the highest. On the other hand, River sand is the lowest bending strength and thermal expansion. The casting result showed that the burn on and veining defects were found on the casting surface. The veining occurred with Australian sand. While, the burn on occurred with Rayong sand, Reclaimed sand and River sand.

Abstract: The article contains the results of experiments carried out on laser irradiation of steels in a constant magnetic field. The experiment shows it possible to increase the cooling speed while heat transfer decreases from the surface into lower metal layers, which slightly reduces laser-hardened layer depth, increases convective mixing of the fusion area, which have a positive impact on the surface layers quality of steel and alloys. This has a positive effect on strength product properties. Magnetic field processing of metal reduces the degree of local plastic deformation of irradiated layer due to magnetostriction phenomenon. Magnetic field superimposition contributes to two-phase decay of the martensite, and reduces residual stresses and crack risk.

Abstract: With the development of advanced manufacturing technology, ceramic matrix composite materials, a typically hard and brittle material, have been widely used in high-tech fields such as aerospace manufacturing. Due to the anisotropy of materials, the quality of conventional processing workpieces is poor, and the processing accuracy is difficult to guarantee. In this experiment, ceramic matrix composite materials are machined by ultrasonic vibration grinding with the CBN grinding rods. The influence of amplitude on the grinding force and the surface quality of the workpiece in the grinding process are analyzed by a series of experiments on ceramic matrix composites. The results show that, compared with the conventional grinding process, in the ultrasonic vibration-assisted grinding process, the grinding force is reduced by about 60%, and the surface quality is also improved significantly,the surface roughness Sa is reduced by about 25%.

Abstract: The article summarizes the results of the of the titanium alloy surface morphology and chemical composition study after grinding with a wheel of cubic boron nitride on a ceramic bond. The titanium alloy was treated using the method of cut-in grinding in the finishing mode using a synthetic water-soluble lubricant-cooling liquid that does not contain mineral oil. The research was carried out using the FEI Versa 3D LoVac electron microscope. Digital photos of the titanium alloy surface at different magnifications are given. Individual objects’ morphology allows us to identify them as wear products of abrasive tools. The chemical composition of the selected objects was studied by local x-ray spectral analysis. CBN crystals are partially or completely pressed into the treated surface and covered with a layer of the treated material. On the surface of CBN crystals, there are chemical elements that are part of the abrasive tool bond.