Materials Engineering 2017

文章题目 页数

作者: Mart Kolnes, Jakob Kübarsepp, Fjodor Sergejev, Märt Kolnes
摘要: Friction stir welding is a novel and promising joining process and most common welding tool failure is transformation of geometry caused by wear. In our point of view, this is adhesion wear. The lathe testing of adhesion wear was conducted to compare wear resistance of following materials: Co-25wt%Cr, TiC-25wt%Ni/Mo and WC-6wt%Co. According to characteristics of investigated materials, they are capable to become alternatives for conventional frictional stir welding (FSW) tool materials. Adhesive wear tests were performed by turning aluminium alloy AW6082-T6 at low speed – travel length, turning speed and feed rate were selected to simulate FSW conditions. The adhesive wear was determined as the change of the geometry of the cutting edges of the tool measured using SEM images. Most promising tool material in terms of adhesion wear resistance is WC-Co hardmetal. The two main stages of wear were distinguished: at first, the appearance of intensive adhesion wear followed by steady state wear. Surface fatigue wear complements development of the adhesive wear.
224
作者: Lembit Kommel, Janis Baroninš
摘要: Wear of material in unlubricated sliding type electrical contact (e.g. contact wires for trolleys and rotor materials in electric engines and current generators) is one of the main failure causing modes of copper (Cu)-based alloys. High electrical conductivity, high tensile strength, suitable hardness and wear resistance under such conditions should be provided. In a present paper required properties of dispersion-hardened Cu-based electrical conductive alloy (Cu-0.68 wt. % Cr-0.02 wt. % S) were obtained by equal-channel angular press treatment with following six press treatments by Bc route and suitable heat treatment. The wear tests were carried out in unlubricated sliding pair with graphite disk. Optimal properties were reached after annealing at 450 °C for 1 h, exhibiting a lowest wear rate (~1.9268·10-9 g·m-1), high electrical conductivity (up to 95 % IACS) and Vickers microhardness up to 1.7 GPa, respectively.
229
作者: Lukas Widder, Markus Varga, Karl Adam, Andreas Kuttner
摘要: In heavy industries like mining or steel production vast amounts of loose materials need to be transported, relocated or otherwise processed. During these routines severe stresses are applied on heavy machinery components such as excavator grabs and clamshells, which ultimately lead to excessive wear. The dominant wear mechanisms under such conditions are impact and abrasion. The focus of this paper is to investigate the fracture behaviour of various abrasives as experienced under real application in the steel industry. Breaking events of abrasive particles affect the impact energies on tool equipment. The Cyclic Impact/Abrasion Test rig (CIAT) was applied to investigate the stability and fracture behaviour of the abrasives. Rotating counter bodies made of martensitic quenched and tempered steel were used to generate impact events on loose abrasive particles. After certain time intervals the abrasives were screened and particle size fractions documented. Impact energy is strongly dependent on size and density, as well as fragility and cracking of particles. As fracturing events diminish particle dimensions and shift size distributions to lower size fractions, each abrasive showed a distinctive impact energy distribution over the course of the test duration. Impact energy distributions of abrasives were correlated to wear rates of the steel samples for each abrasive used. The results indicate a distinct behaviour of each abrasive, yielding certain impact energy distributions. Depending on processing specific abrasive goods in actual applications, impact energies and associated wear loss can differ significantly.
234
作者: Marek Góral, Tadeusz Kubaszek
摘要: Thermal Barrier Coatings (TBC) is the most advanced system for protection of turbine blades and vanes against high temperature, and oxidation. They are used in most advanced jet engines. In present article the new Plasma Spray Physical Vapour Deposition Technology was used to obtain yttria stabilized zirconia oxide coating with columnar structure. In research the different process parameters were changed. It was observed that powder feed rate had big influence on coating thickness. The large amount of Ar in plasma gasses combined with high powder feed rate resulted in partial evaporation of ceramic powder and splat-type structure. The same effect was observed when the power current was decreased form 2400 to 1600 A as well as pressure was increased to 200 Pa when the powder feed rate was 30 g/min. The obtained results showed that full evaporation of ceramic powder requires very low feed rate of ceramic material (2 g/min), high power current and high He content into plasma.
243
作者: Alexey Tatarinov, Viktor Mironov, Dmitry Rybak, Pavels Stankevich
摘要: Possibilities of non-destructive testing (NDT) methods to assess the quality of permanent joints of powder metal parts were evaluated. Antifriction bushing-bushing couples used in transport braking systems were investigated. The parts made of bronze graphite were crimped by pulsed magnetic deformation by means of electromagnetic equipment with a maximum discharge energy of 30 kJ. The gap between joint parts in the couples was assessed by ultrasonic and radiographic methods. A standard ultrasonic flaw detector Krautkramer USM-25 with an Olympus 4MHz dual-element echo transducer and an industrial x-ray apparatus YXLON EVO 200D were used, correspondingly. In first trial, both methods were equally sensitive to tight and weak connection of joints.
248
作者: Jing Fu Song, Gai Zhao, Qing Jun Ding, Jin Hao Qiu
摘要: Space exploitation and development need high-performance polymer based tribo-materials in order to reduce the weight and improve the reliability of mechanical moving components. However, the wear resistance of polymer composites will decrease after space irradiation. In order to improve the anti-irradiation and wear resistance, the high performance polyimide (PI) composites reinforced with aramid fibers (AF), filled with polytetrafluoroethylene (PTFE) and Al2O3 were designed and prepared using hot press sintering. The effect of the individual atomic oxygen or proton irradiation as well as both on the tribological properties of the PI composites were systematically investigated against Si3N4 ball on a ball-on-disk test rig under simulating space environment system, and coefficient of friction and wear rate were considered as responses. The worn surfaces of the composites were observed by scanning electrical microscopy to reveal wear mechanisms of the materials’ damage. Experimental results indicated that the wear rate of the PTFE/AF/PI greatly increased after atomic oxygen and proton irradiation due to oxidation degradation effect on the polymer matrix. However, filling Al2O3 nano-particles into polyimide matrix can improve the wear resistance because of oxidation layer, gradually formulated during the process of atomic oxygen irradiation, which can protect the polymer composites and avoid further oxidation. This study will expect to provide the helpful guidance for designing high performance polymer based frictional materials in the application of space science.
253

显示46个文章标题中的41到46个