Theoretical and experimental research indicates that radial loads have a significant influence on the value of belt-on-idler rolling resistances. Computational models discussed in literature use the notion of unit rolling resistance, i.e. rolling resistance per unit length of the idler. The total value of the rolling resistance of belt on a single idler is determined by integrating unit rolling resistance with respect to the length of the contact zone between the belt and the idler. This procedure requires the knowledge of normal load distribution along the contact zone between the belt and the idler. Loads acting on the idler set have been the object of both theoretical analyses and laboratory tests. Literature mentions several models which describe the distribution of normal loads along the contact zone between the belt and the idler set (Krause & Hettler, 1974; Lodewijks, 1996; Gładysiewicz, 2003; Jennings, 2014). Numerous experimental tests (Gładysiewicz & Kisielewski, 2017; Król, 2017; Król & Zombroń, 2012) demonstrated that the resultant normal loads acting on idlers are approximate to the loads calculated in theoretical models. If the resultant normal load is known, it is possible to assume the distribution of loads acting along the contact zone between the belt and the idler. This paper analyzes various hypothetical load distributions calculated for both the center idler roll and for the side idler roll. It also presents the results of calculations of belt rolling resistances for the analyzed distributions. In addition, it presents the results of calculations with allowance for load distribution along the generating line of the idler.
In multi-stage wire drawing machines productivity growth can be achieved at higher drawing speeds by preventing wire breakage during the process. One disadvantage of high-speed wire drawing is the requirement imposed by machine dynamics in terms of its stability and reliability during operation. Tensile forces in the wire must maintained by fast synchronization of all capstans speed. In this process, the displacement sensors play the main role in providing the control system with feedback information about the wire condition. In this study, the influences between the sensors and actuator driven capstans have been studied, and tuner roll concept of a wire drawing machine was experimentally investigated. To this aim, measurements were carried out on two drawing stages at different drawing speeds and obtained results were presented. These results clearly show the fast changes of the capstans speed and the angular displacements of the rollers that tighten the wire, which only confirms the high dynamics of the wire drawing machine.
The paper presents a new method for building measuring instruments and systems for gyro-free determination of the parameters of moving objects. To illustrate the qualities of this method, a system for measuring the roll, pitch, heel and trim of a ship has been developed on its basis. The main concept of the method is based, on one hand, on a simplified design of the base coordinate system in the main measurement channel so as to reduce the instrumental errors, and, on the other hand, on an additional measurement channel operating in parallel with the main one and whose hardware and software platform makes possible performing algorithms intended to eliminate the dynamic error in real time. In this way, as well as by using suitable adaptive algorithms in the measurement procedures, low-cost measuring systems operating with high accuracy under conditions of inertial effects and whose parameters (intensity and frequency of the maximum in the spectrum) change within a wide range can be implemented.
The rolls for the hot rolling finishing stands are cast centrifugally as two or three-layer rolls. The working layer is called a shell. The material of the shell is selected according to the position of the respective roll in the final finishing stand of the rolling mill. Typically, a combination of rolls made of a high-chromium cast iron + indefinite cast iron or high-speed steel + indefinite cast iron is commonly used. Great attention has been paid to indefinite cast iron in recent years and this material received a number of modifications that led to the increase of material properties up to 20% in comparison to the ordinary indefinite cast iron. But the goals of the new generation of material for hot rollers were chosen higher: increasing of production about 30% and more. This material has specific physical properties, heat treatment requirements as well as rolling mill requirements as is stated in the paper. It is expected that introduction of this material will reduce the difference between wear of the front and finishing stands, which can extend rolling campaigns and have a positive effect on the reduction rolls exchanges, the grinding of the rolls and the reduction of downtime.
An important phenomenon of delta wing is the mechanism of vortex core, which indicates the increase in lifting force until the occurrence of the vortex breakdown. The computational fluid dynamics (CFD) is very helpful in visualizing and providing analysis of the detailed data. The use of turbulent models will affect the quality of results in obtaining the vortex breakdown phenomenon. This study used several models of turbulence to capture the occurrence of vortex breakdown and compare it with experiments using water tunnel test facility. The results show that all turbulence models give good results at a low angle of attack (AoA), but at a high AoA the DES model gives the results closest to experimental ones with Cl error value of about 1%. Taking into account the time required and the acceptable level of accuracy, the use of SST and k-omega models is an alternative option for use in the detection of vortex breakdown.
A cold roll-bonding process was applied to fabricate an AA1050/AA6061/AA1050 multi-layer sheet. Three Al sheets in which an AA6061 sheet is inserted inside two AA1050 sheets of 2 mm thickness, 40 mm width and 300 mm length were stacked up after surface treatment, and the material was then reduced to a thickness of 1.0 mm by multi-pass cold rolling. The AA1050/AA6061/ AA1050 laminate complex sheet fabricated by roll bonding was then hardened by a natural aging (T4) and an artificial aging (T6) treatments. The microstructures of the as-roll bonded and the age-hardened Al complex sheets were revealed by optical microscope and electron back scatter diffraction analysis, and the mechanical properties were investigated by tensile and hardness testing. The strength of the as-roll bonded complex sheet was found to increase by 2.6 times, compared to that value of the starting material. Both AA1050 and AA6061 showed a typical recrystallization structure in which the grains were equiaxed after heat treatment. However, the grain size was smaller in AA6061 than in AA1050.