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New Method for Dynamic Tribological Test of Engineering Polymers
25-29Views:238In this article, tribological tests of Polyamide 6 (PA 6), Ultra High Molecular Weight Polyethylene (UHMW PE) and Polyoxymethylene copolymer (POM C) by a new testing method is introduced. The tribometer used in the test is capable for pin-on-disc measuring within all possible layout known in tribology practice, otherwise can be modified into special model of fatigue sliding test. The pin was a specimen made from examined materials, always in contact with a rotating metal disc under a normal load, which is usually static. However, since vibration exists in every practical scene as an important phenomenon, for instance in turning process, we added vibration load into the test. The supplement load is generated by a special-designed vibrating machine. Then properties of examined materials can be studied more profoundly under vibration load. As a result, different value of friction coefficient in static and vibration load have been discovered and taken into comparison.
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Effect of Heat Input on the Toughness Properties of S690QL Steel during Hardfacing
1-12Views:53In recent years, the use of high-strength steels in hardfacing process has become increasingly common. One typical industrial example is the case of hydraulic shears used in building demolition operations, where the components are exposed not only to significant abrasive wear but also to intense dynamic loading. The use of quenched and tempered high-strength steel grade S690QL has become particularly widespread in this field, primarily as the base material for the hardfacing applied to the most heavily loaded regions of demolition shears. However, quenched and tempered high-strength steels are highly sensitive to the effects of the welding thermal cycle, which typically cause detrimental changes in the microstructure and mechanical properties of the heat-affected zone. The thermal cycles occurring during hardfacing differ from those typical of fusion welding, and consequently, the structure and mechanical properties of the resulting heat-affected zone may also vary. In addition, the penetration depth of the hardface layer can differ, which may significantly alter the load-bearing cross-section of the high-strength steel and, thus, the in-service behavior of the component. In the experimental work, hardfaced samples were performed on S690QL base material using different levels of heat input, thereby producing varying penetration depths. The aim of the study was to determine the effect of penetration depth on the resistance of the hardfaced component to dynamic loading. The tests were carried out at both +20 °C and –40 °C. The results clearly demonstrated that samples with deeper penetration exhibited reduced toughness at both investigated temperatures.
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Introduction to Design and Analysis of Torsional Vibration Dampers in Vehicle Industry
310-324Views:494The crankshaft of today’s internal combustion engines with high performance output are exposed to harmful torsional oscillations originated from the unbalanced gas and inertial forces. To avoid the fatigue damage of engine components, caused by the undesired vibrations, torsional vibration dampers can be applied. Viscodampers are one type of the torsional vibration dampers, which operational fluid is silicone oil. For cost-effective R&D activities and production, finite element and finite volume numerical discretization methods based calculation techniques must be involved into the engineering work supported by the modern computer technology. The aim of this paper is to provide an insight into the multidisciplinary design and development process of visco-dampers in vehicle industry applications. Four different examples as structural, fatigue, CFD analyses and structural optimization have been introduced in the present work. It turned out from the static structural and fatigue analyses, that the investigated damper has safety factor over the limit for both static structural and fatigue analyses, so it is suitable for the given load conditions. In the structural optimization process 34.36% mass reduction has been achieved. According to the coupled fluid dynamic and heat transfer simulations a rather stagnating air zone evolved between the engine and the damper during the operation, which can cause efficiency reduction of cooling fins mounted onto the housing. In light of the numerical results, the suitable damper position has been determined for the highest heat transfer.
