The article presents the problem of quality management in the process of material selection for structural elements of a car dump truck. The study took into account the classical management pyramid and there was used the optimization method (generalized objective function). The center that manages the process of production / assembly of the dump truck should be the level of organization that has the highest degree of processing of required information and making strategic decisions in this respect. The design process of structural elements is carried out primarily in terms of the ability to provide adequate physical and mechanical properties in the process. There is a very strong tendency to reduce the own weight of the semi-trailers by increasing the weight of the load. This is an important criterion from the point of view of the economics of operation of technical facilities of this type. The article presents the results of the application of a generalized objective function in the field of material selection for construction elements of a dump truck. The analysis includes structural elements made of S355 steel and Hardox 400 and 450 fine-grain steel.
František Nový, Otakar Bokůvka, Libor Trško and Michal Jambor
In this paper the authors introduce their own selected experimental results in the field of the investigation of fatigue resistance of structural steels. The experiments were carried out on the nine structural steels including high strength steels, DOMEX 700MC, HARDOX 400, HARDOX 450, 100Cr6 (UTS from 446 MPa to 2462 MPa) at high-frequency cyclic loading (f = 20 kHz, T = 20 ± 5 °C, R = -1) in the region of number cycles ranged from N ≈ 2×106 to N ≈ 2×109 cycles of loading. The continuous decrease of fatigue strength in dependence on the number of loading cycles was observed with the average value of ratio σa2×109/σa2×106 = 0.69.
Otakar Bokůvka, Michal Jambor, Libor Trško, František Nový and Barbara Lisiecka
In this paper, the authors publish their own experimental results of the examination of the different holes (milled, drilled and drilled + shot peened) on the fatigue lifetime of 20MnV6 steel. The experiments were carried out at low-frequency loading (f = 10 Hz, pulsating tension loading) in the region from N = 2×105 up to N = 2×106 cycles. The best fatigue properties were obtained in the parts with drilled + shot peened holes.
Michal Jambor, Otakar Bokůvka, František Nový, Libor Trško and Juraj Belan
Nickel base superalloys are hi-tech materials intended for high temperature applications. This property owns a complex microstructure formed by matrix of Ni and variety of precipitates. The type, form and the amount of these phases significantly affect the resulting properties of these alloys. At sufficiently long exposure to high temperatures, the transformation phase can occur, which can lead to degradation of properties of these alloys. A cyclic plastic deformation can accelerate these changes, and they could occur at significantly lower temperatures or in shorter time of exposure. The aim of this study is to describe phase transformation, which can occur by a cyclic plastic deformation at high temperatures in nickel base superalloy Inconel 718.
The article deals with a reduction of friction coefficient of bearing steel 100Cr6. Reduction of friction was achieved by means of a CarbonX DLC coating. The coating exhibited excellent friction and mechanical properties. This coating was applied to samples made of 100Cr6 bearing steel. The friction results of the CarbonX coating were compared to the friction results of the 100Cr6 bearing steel. Reducing the friction of 100Cr6 bearing steel resulted in reduced wear and increase lifetime. The friction process of the samples will take place in an environment without lubrication. The aim of the article is to verify the behaviour of the DLC coating without the presence of lubricant in the friction node. The achieved results are to be interpreted in the conclusion of article.