Materials Science Forum Vol. 952

Abstract: In order to study the pre-straining and natural aging effects on the age-hardening response of EN AW 6082 and EN AW 6023 aluminium alloys during artificial aging at 170°C, the pre-straining by 5% was performed immediately after solution treatment of alloys at 550°C and subsequent quenching. The age-hardening response during artificial aging applied after various natural aging time (from 0.1 to 5 000 hours) was investigated using Vickers microhardness measurements and transmission electron microscopy characterization. It was found that pre-straining of quenched alloys state caused a dislocation density increasing in solid solution, which resulted in an immediate microhardness increase of alloys. During the subsequent natural aging of EN AW 6082 alloy, its microhardness increased right after alloy quenching and pre-straining, but only to the values obtained for the unstrained alloy state. On the contrary, the hardness of pre-straining EN AW 6023 alloy that is alloyed by Sn did not increase either after 10 hours of natural aging. This phenomenon is attributed to the effect of Sn on suppression of the strengthening clusters formation. The hardness of alloys increased greatly during artificial aging after pre-straining and natural aging due to accelerating the formation of coherent β″-phase particles. The negative effect of natural aging on the maximum age-hardening response obtained during alloys artificial aging had been observed for most of the pre-strained and naturally aged alloys states, with exception of EN AW 6023 alloy states that were pre-strained and shortly naturally aged (up to 100 hours).

Abstract: This paper describes the development and operation of a small parts coating device in an electrophoretic manner. The cataphoretic coating process is nowadays highly desirable and generates a continuous coating against corrosion. The aim of the research is to find solutions or innovations to coat small parts in bulk. Small parts are inserted inside the device and painted in a cataphoretic manner. Painting is based on rotary device and random contact between small parts and cathode.

Abstract: Principle, significance and history of cast iron surface hardening. Benefit of high-energy heat sources. Cast iron resistance against thermal shock. Production of large surface hardening. Measurement of its depth and hardness - hardening depth definition of cast iron. Practical results and experience with large castings for machine tools. Research of diagnostics of magnetic spot method application. Optimization of diagnostics of layer depth and hardness using special developed non-destructive structuroscope DOMENA ZL.

Abstract: Four hard thin coatings (TiSiN, TiN-CrN multi, AlTiN a WC) were deposited on the WC+Co substrate by cathodic arc deposition. Adhesion test of PVD coatings was evaluated by comparison failure of coating surfaces. The surface features after the Rockwell indentation test were examined by light microscopy. The results showed that the AlTiN and WC coatings exhibited acceptable failure and are appropriate for usage in practice. Unlike them, had TiSiN and TiN-CrN coatings poor adhesion, which resulted in unacceptable failure after Rockwell C test.

Abstract: The manufacture by casting, remains the most economical way to obtain pieces with complex geometries and diverse alloys. This is a highly complex process given the large number of variables and factors involved in it, thus, when one of these is ignored and/or left out of control, process errors and distortions usually occur. The present paper introduces a design of experiment of the type: Central Composite Design (2²) + Star, that took into account the variation of important parameters in the pouring, solidification and cooling process, such as pouring temperature and pouring ratio, and that also added the “coefficient factor” relating the geometric parameters of the risers. This design studied the factors ‘effects in 16 runs, including 2 central points per block, with the aim of finding the best working area of the risers and the optimal values of the parameters studied under specific conditions. The statistical processing of the data obtained showed the relationships between the parameters studied and the different regression equations. The results obtained allowed to establish new procedures and work volumes for the risers in order to reduce the consumption of material during the process.

Abstract: One of the advanced ways of provision of functional properties of interference fit joints is to control contact interaction between mating parts, particularly by assembling with application of anaerobic materials polymerizing in contact area. The main advantage of using anaerobic materials is that this technology allows us to harden different parts of the joints selectively. The purpose of the work is to study the possibility of rational provision of functional properties of interference fit joints by selective hardening in case of assembling with the use of anaerobic materials. Modelling of bearing strength of interference fit joint is carried out according to finite element method, with theory of contact interaction between mating surfaces being used. The results of experimental research are given. Anaerobic material is used as a material for hardening of joints. It was discovered that exploitation load in form of torque or axial force is distributed along the length of interference fit joint rather nonuniformly. To decrease expenses, it is necessary to harden those areas of joint which are located by the side of load application. The way of assembling of interference fit joints by pressing with selective use of hardening material is proposed. The technique of reliable identification of the necessity and the moment to apply anaerobic material while assembling parts was developed. As a result, functional properties of pressure joints are reached the most rational way.

Abstract: The paper focuses on the field of unconventional technologies, specifically on ultrasonic welding of polymeric materials. Ultrasonic welding is one of the well-known techniques of plastic bonding, which significantly reduces the production process. It differs from other welding and connecting processes by the fact that the heat required for joining two plastic materials is obtained solely by mechanical vibrations between the connected parts. The paper aims to assess the strength of the welded specimens and then compare them with the model situation. For experimental welding, polypropylene was chosen. The specimens in the form of standardised test blades were subjected to a tensile test after welding in order to evaluate the effect of the length of the overlapping joint on the final strength of the joint. The resulting weld strength (bearing capacity) was also compared to the strength of the basic material to determine the degree of the strength loss against the basic material.

Abstract: The article focuses on the research of selected thermoplastic materials processed by the Fused Deposition Modeling (FDM) additive manufacturing method and dimensional accuracy of parts in particular. The selected thermoplastic materials were ABS, PLA and HIPS. The digital model of the object (upper teeth) was obtained by the intraoral 3D scanner of 3Shape TRIOS used in dentistry. Based on the 3D (Three Dimensional) scanned digital model, the manufacturing of the upper teeth was performed on the Zortrax M200 FDM 3D printer. Parameters of the manufactured parts were as follows: Layer thickness 0.09 mm, infill 20% and model orientation 0°. The manufactured parts were digitized by the GOM ATOS Triple Scan optical 3D scanner with the measuring volume of MV 170. The dimensional accuracy of the parts was evaluated in the GOM Inspect software.

Abstract: Paper focuses on additive manufacturing of assembly tool for hole selection. One of the most important part in design and optimization process in additive manufacturing for assembly tool is material selection and technology. In this case was chosen plastic material know as poly-lactic-acid. Polylactic acid has low shrinkage and huge potential in assembly tooling and assembly fixture manufacturing. Main benefits are in use of additive manufacturing for this purpose because of huge manufacturing variability and time savings in case of frequent design changes. From filament fused fabrication technology stand point is important to determine right manufacturing orientation of part. Main material benefit is bio-degradability and recyclability. Current trend in manufacturing is bio materials, clean manufacturing and ecofriendly products. Correct orientation of assembly tool will optimize manufacturing process in one way. Article is aimed on manufacturing precision in each orientation of part on build late. With right orientation of part in additive manufacturing process is determined exact precision of assembly tool manufacturing. For measurement was used coordinate-measuring machine. In this case measurements and precision checking are made only in exact spots where is needed the most precise distance

Abstract: Good quality of surface layer is an important aspect for correct function and longevity of final product. Surface layer was modified by beta radiation with differing intensity. Radiation caused creation of three dimensional spatial network, that directly leads to improvements of the tested polymer’s (PA11, PA12) surface properties. Surface properties (micro-creep) were measured by micro-indentation test on MHT³ machine. Goal of this paper is to modify the surface layer (by using several different intensities of beta radiation) in a way, that causes increase in resistance against long term stress (micro-creep) in the final product, which is an important property that ensures correct function of the product. The changes in micro-creep were compared and afterwards confirmed by the use of gel test, that showed us what percentage of the whole part was crosslinked.