Research on rolling stability of the flexible waverider based on computational fluid dynamics/computational structural dynamics/rigid body dynamics coupling methodology

The shape of hypersonic aircrafts represented by waveriders is becoming more slender and flatter, thereby greatly reducing the structural rigidity. This innovation is applied to satisfy the demand of long-range flight. The rolling stability of the waveriders is poor due to the slender shape. Therefore, the effect of the elastic deformation on the rolling stability cannot be ignored. The effect of the elastic deformation on the stability of rolling and forced pitching/free rolling coupling motions of the waveriders is studied through computational fluid dynamics (CFD)/computational structural dynamics (CSD)/rigid body dynamics (RBD) coupling methodology. Comparison results of numerical simulation indicate that the elastic deformation of the structure increases the local angle of attack, thereby enhancing the static stability of the waveriders. The rolling motion of the waveriders changes from point attractor to periodic attractor when the vibration velocity due to elastic deformation is considered. The rolling oscillation frequency of the flexible model is higher than that of the rigid model. For the forced pitching/free rolling motion, stability theory based on the rigid body hypothesis is unsuitable when the elastic effect is taken into consideration.

Producing Hollow Shafts in a New Horizontal Mill by Novel Flat-Knifing Cross-Wedge Rolling With Single Guide

To meet the requirement of lightweight, there are increasing solid shafts being designed to be hollow in transportation industry. In this study, a novel method of flat-knifing cross-wedge rolling (FCWR) with single guide is proposed including a modified roller, a horizontal mill and a single-guide structure, and its key problems are studied by numerical simulations and experimental tests. A mathematical model of FCWR roller is established, which reveals the wedge length of rollers is effectively reduced by modifying knifing wedge from normalized roller. Further, a horizontal multifunctional mill is invented and constructed to carry out the FCWR experiment with single guide. According to the results from the numerical simulations and corresponding experiments, it is observed that the typical defects of hole expansion and knifing groove are absolutely avoided because the improved flat-knifing wedge produces a radial force to shrink the inner hole and avoid the deformation concentration of the outer surface during knifing stage. Moreover, the single guide rolling performed in the horizontal mill efficiently improve rolling stability because the workpiece is restricted into a smaller workspace. To the authors’ knowledge, all these integrated improvements of FCWR roller, single guide rolling and horizontal mill are innovative, which are of great engineering significance to manufacture hollow shafts on account of the advantages of avoiding forming defect, reducing roller diameter, improving rolling stability and simplifying mill structure.

Control of speed modes of heavy-plate mills rolling.

Control of speed modes on heavy-plate mills is one of the factors that determine the efficiency of the rolling process. The choice of speed controls influences the mill productivity, geometric dimensions of the rolled product (longitudinal thickness variations) and compliance with the set temperature mode which determine the mechanical properties of the rolled product, etc. The article considers the limitations in the choice of speed controls which can be divided into two groups: limitations of the capabilities of rolling engines and technological limitations. The first group is determined by the allowable engine under the conditions of reliable current switching on the collector and the maximum allowable engine speed. Technological limitations of speed controls are considered in the paper as well. The speed of grasp is limited to the maximum un-der the condition of metal grasp without skew, blows and dynamic torque overloads in spindles and maintenance of constant grasp without slipping, as well as the possibility of prevention of emergencies. Steady (maximum) rolling speed can be limited to the maximum by the conditions of rolling stability and prevention of sticking of metal to the rolls. The rate of metal release from the rolls is usually chosen in the way so that the pause stipulated by the braking of the sheet on the roller conveyor and its subsequent return to the rolling mill would not exceed the operating time of the pressure mechanism. In some cases, the release rate can be determined by other technological operations. The maximum acceleration of the main drive of the horizontal mill is limited by the conditions of slipping of the working roll towards the sup-port roll. The paper also considers rational speed graphs of rolling on heavy-plate mills. They are the most common type of high-speed rolling graphs on heavy-plate mills. The listed above solutions for the control of high-speed rolling modes can be used in the development of APCS of heavy-plate mills rolling.

STUDI PERENCANAAN PONDASI TIANG PANCANG PADA JEMBATAN KERETA API KM 95+870 JOMBANG MADIUN

ABSTRACTBridges are complementary buildings that are used to continue the road or railroad that are cut off due to obstacles such as rivers, waterways, roads and valleys. As with the Jombang - Madiun railway bridge BH 258 km 95 + 870 Kertosono. The bridge that was built on the Brantas river aims to increase the number of new lanes to four lanes.The author wants to plan the development with a pile foundation. This foundation is planned by the Mayerhof method based on the SPT data obtained from the Contractor on the construction of the project namely Hutama, Modern Mitra, KSO.In the study of pile foundation planning obtained a vertical load of 8,708,531 tons, horizontal load of 567.69 tons, bearing capacity of the foundations was equal to 10.006.22 tons greater than the axial force that occurred which was 8,708,531 tons. The rolling stability value is 16.04 greater than 1.5 and the stability of the displacement is 4.46 more than 1.5, the stability of the decrease is 22.34 tons / m2 > the carrying capacity of the soil is 12.2 tons / m2 (not okay) then the pile is needed to hold vertical style.Keywords: Bridge, Mayerhof, Pile

Research and Application of Work Roll Contour Technology on Thin Gauge Stainless Steel in Hot Rolling

Shape control is the key technology for thin gauge stainless steel in hot rolling. Because of high rolling force, work roll can suffer from serious uneven wears, edge drop of strip temperature and so on. And in turn these imperfections lead to defects in thin gauge stainless steel production, such as big crown value, quarter wave, edge profile anomalies, poor rolling stability. In order to improve shape the control ability, one will have to eliminate the quarter wave, make roll wear uniform, increase rolling stability in the thin gauge stainless steel production, use high performance variable crown technology in upstream stands, use mixed variable crown technology in last stand, and use conventional work roll with variable shifting stroke strategy in other downstream stands. The above technologies have been successfully applied in several stainless steel productions, which have completely independent intellectual property rights, and the crown control precision of thin gauge stainless is 98.1%, flatness control precision is 97.5%, also a 1260 mm × 1.6 mm ultra-thin gauge stainless steel was successfully developed.