Papers by Keyword: Rolling

Abstract: Microstructures and properties of ultrafine grained (UFG) iron by different rolling processing are investigated. By applying the asymmetric rolling (ASR), the equiaxed UFG iron with the grain size of 0.9 μm has been obtained due to the shear strain induced by the mismatch of the two roll during ASR. With the same rolling reduction, the ASR processed iron shows higher yield strength than that of the symmetrically rolled one. When the ASR processed iron is further symmetrically rolled, the grain morphology maintains equiaxed and the grain size decreases to about 0.3 μm.

Abstract: Chatter is one of the most encountered vibration problems in high-speed rolling of thin steel sheets in tandem mills. Due to its negative cause on product quality and maintenance costs, chatter is a technical and economical problem in rolling mills. To study chatter in rolling, it is necessary to set up models for the rolling process as well as the mill stand. Existing models of rolling process are analytic and are based on many simplifying assumptions. In current work the finite element method is utilized for the first time to model the chatter vibrations in rolling, which relaxes many of these assumptions. The model has the benefit of mass translation to the computational region by using Arbitrary Lagrangian Eulerian (ALE) technique, which tremendously reduces huge computational requirements of common Lagrangian models. Four chatter mechanisms in rolling are reviewed in this paper, but the presented model is updated for simulating the negative damping effect by means of some online velocity sensors and signal filtering method in applying the ALE boundary conditions. Using this new model, single stand negative damping mechanism of chatter and its effect on the sheet surface is understood more accurately. Simulation results are in comprehensive agreement with the experimental and industrial observations.

Abstract: The demand on closely-tolerated and complex functional components in the automotive sector, like e.g. synchronizer rings, leads to the development of a new process-class named “sheet-bulk metal forming”. Within this technology bulk metal forming operations are applied on sheet metals. In the following two novel approaches considering machines and tools for sheet-bulk metal forming are presented. The first approach aims on a technology based on rolling, which is suitable for mass production. The second one is an incremental forming solution for low batch production. Both machine concepts allow the application of different forming strategies to manufacture individual tailored semi-finished products in term of a pre-distribution of material. These products feature variable sheet thicknesses and mechanical properties, which can be adapted to their case of applica-tion. Depending on the individual batch size, the blanks can be finished to functional parts by sub-sequent forming processes like deep drawing and upsetting, extrusion or incremental forming. In this paper the case of an incremental tooth-forming is mainly considered. Forming sequences and resulting loads are modeled and calculated by finite elements simulations for all discussed processes to serve as a basis for the design and dimensioning of the machine components and forming tools.

Abstract: In order to solve the problem of path planning for mobile robot in unknown environment, improving overall performance of the planned path, a multi-constrained local environment modeling method is used in which the traversability, security, movement smoothness and goal-guiding are taken into consideration. On the basis of environment modeling, improved local path planning algorithms is proposed by combining Bug algorithm and rolling path planning algorithm. That improved algorithm contains Move to Goal behavior and Wall Following behavior, for overcoming local minimum, designed for robot using adaptive dynamic window. Simulation results show that the proposed methods have a good safety obstacle avoidance capabilities and environmental adaptability.

Abstract: Among the materials employed for orthopedic implants, Ti-6Al-4V is definitely the best choice due to its excellent properties. However, a more intense use is hindered by high cost and the presence of harmful elements, viz. Al and V. A solution can be found in commercially pure Ti, provided its tensile and fatigue properties can be upgraded by some process of Severe Plastic Deformation. In the present work, Grade 2 Ti was submitted to up to four Equal Channel Angular Pressing passes, followed by cold rolling (30 70 and 90% reduction ratio) Hardness and tensile properties were determined, paying attention to the work hardening behavior. Results show that Severe Plastic Deformation gives a 442 MPa increase over the yield strength of annealed Grade 2 Ti (originally 337 MPa), while elongation reached 21%. Best results were obtained with four passes followed by 70% cold rolling reduction. Finally, the microstructural stability was assessed by hardness measurements.

Abstract: The effects of asymmetric and symmetric rolling at room temperature on mechanical properties and microstructure of the commercial purity Ti were investigated by means of mechanical test, optical microscopy, X-ray diffraction and transition electron microscopy. The results show that through asymmetric and symmetric rolling processes the ultimate tensile strength is substantially increased from 450 MPa to 960 MPa. Microstructure observation illustrates this variation in mechanical property is caused by the grain refinement and work hardening.

Abstract: A new continuous severe plastic deformation (SPD) procedure integrating conventional rolling with equal-channel angular deformation (designated CR-ECA deformation procedure) was investigated. Experimental results show that the SPD procedure has the capacity of realizing continuous SPD processing of long-size work-pieces with good surface qualities. Numerical simulations by using finite element code DEFORM-3D show that the number of roller pairs had significant influences on the the CR-ECA deformation procedure. As the number of roller pairs changed from 1 to 2, 3 and 4, the effective strain increased by 10.1 %, 10.1 % and 16.1 %; the output velocity increased by 10.8 %, 15.9 % and 14.4 %; the torque of the primary feeding roller decreased by 19.0 %, 34.7 % and 45.6 %; the total torque increased by 7.0 %, 11.8 % and 13.4 %; and the energy consumption used for making unit volume work-piece subjected to unit effective straining decreased by 12.2 %, 15.0 % and 19.4 %.

Abstract: Finite element model was established for the special-section ring rolling. The whole process of ring rolling was simulated based on the DEFORM software. The law that the rolling force is influenced by the idle roll feed speed and main roll rotational speed were found. The results show that the roughcast structure should be similar to finished product structure. IT is significant to optimize roughcast structure and processing parameter, and to improve efficiency of rolling.

Abstract: The aim of this study is to get a better understanding of Micro Flat-Wire Roll Forming Technology. There are three methods for Mirco flat-wire forming, i.e., drawing, extrusion, and rolling. Without replacing the equipment, rolling method only demands to adjust the relative roll gap between the pressure and the wire deformation that it can produce different specifications of mirco flat-wire. The rolling equipment was introduced and can be divided into three parts, the mechanism section, the control part and the wire-locating device. Furthermore, the rolling process parameters were summarized as well. The effect of rolling amount and rolling speed on the wire surface quality was also discussed.

Abstract: This paper analyzed the microstructure evolution and grain-refining mechanism in producing ultra-fine grained steel sheet by heavy rolling of lath martensite. The results show that this technique is composed of three processes with different grain-refining mechanism respectively: i) austenite grains subdivide into homogeneous and tiny martensite laths during quenching; ii) martensite laths are thinned and damaged during heavy rolling; iii) equiaxed ultra-fine ferrite forms during low temperature recrystallization annealing.