A Method to Solve the Stiffness of Double-Row Tapered Roller Bearing

By analyzing the roller force, the nonlinear stiffness model of the double-row tapered roller hub bearing is derived, and the method of solving the hub bearing stiffness matrix is summarized: if the displacement between the inner and outer rings is known, the stiffness of the hub bearing can be directly calculated. If only the external load of the hub bearing is known, the displacement of the hub bearing needs to be solved by numerical method, and then the stiffness of the hub bearing can be calculated. The improved Newton-Raphson method is used to solve the stiffness matrix of the hub bearing. Three-dimensional FE model of DRTRBs is presented and validated the proposed the stiffness matrix of the hub bearing. It is found that the radial stiffness of the hub bearing is greater than the axial stiffness. The stiffness of the hub bearing is greatly affected by the vertical force of the ground and the wheel driving torque, showing obvious nonlinearity. The smaller the vertical ground load and wheel driving torque, the greater the influence of vertical ground load and wheel driving torque on the hub bearing stiffness.

Composite Deposits Developed by Welding on Horizontal Mill Hammers

The paper presents the concept of designing active hammer edges of horizontal mills for grinding tungsten carbide waste by making composite layers deposited by welding. The new generation of hammers is carried out on the principles of preventive and repetitive maintenance, by endowment with wear addition, predetermined as volume and geometric configuration, depending on the specific conditions of uninterrupted use for a period of time established for economic reasons. The main demands that affect the integrity of the active areas of grinding mills (high pressure abrasion wear, thermo-mechanical fatigue) generate both material losses and output from working rates, as well as excessive elongation of the support elements under the combined action of centripetal force and of the pressure exerted by the ground load. Under these conditions, the technically and economically optimized solution is to design the modular active elements in the form of easily assembled detachable components, made of a low alloy steel with average tear resistance (450-600MPa) on which we deposit by welding layers of composite austenitic steel, hardened by compression, so as to increase the lifetime of the hammers by up to 35% compared to the present solution, which can be upgraded up to 3 times for reuse.

Experience in design and construction of the Log tunnel

A twin highway Log tunnel is a part of a new motorway connection between Maribor and Zagreb, section Draženci-Gruškovje, which is located towards the border crossing between Slovenia and Croatia. The tunnel is currently under construction, and only the excavation works have been completed during the writing of this paper. The terrain in the area of the Log tunnel is diverse, and the route of the highway in its vicinity is characterised by deep excavations, bridges or viaducts. The Log tunnel is approximately 250 m long, partly constructed as a gallery. The geological conditions are dominated by Miocene base rock, featuring layers of well-connected clastic rocks, which are covered by diluvium clays, silts, sands and gravels of different thicknesses. Due to the short length of the tunnel, the usual separation of the motorway route to the left and the right tunnel axes was not carried out. Thus, the tunnel was constructed with an intermediate pillar and was designed as a three-lane tunnel, including the stopping lane. The construction of the tunnel was carried out using the New Austrian tunnelling method (NATM), in which the central adit was excavated first and the intermediate pillar was constructed within it. The excavation of the main tubes followed and was divided into the top heading, bench and the invert, enabling the intermediate pillar to take the load off the top heading of both tubes. The secondary lining of the tunnel is currently under construction. The experience of the tunnel construction gathered so far is presented in the paper. The main emphasis is on the construction of the intermediate pillar, which had to take the significant and asymmetrical ground load.