Papers by Keyword: Multi-Pass

Abstract: Roughing has been simulated with the Finite element software Abaqus^TM to replicate an industrial-scale process. The model has been made to be as close as possible to its real counterpart. For this purpose, an automated controlling logic has been created to simulate the multiple passes as well as inter-pass times for roughing. Simulating multiple passes with FEM is computationally very demanding, so new methods to reduce computing times are worth considering. During a roll pass an explicit solver is necessary due to high deformation amounts and rates. An explicit solver is tied to a very small time increment, so it takes a long time. On the other hand, inter-pass periods do not include any deformation or roller contact, so an implicit solver is quite capable of computing this portion of the simulation. An implicit solver can speed up the time increment considerably when compared to the explicit solver, so using it potentially saves a significant amount of computing time. Unfortunately, Abaqus does not include any methods to change the solver during a single simulation. Instead it is possible to communicate between the two solver types by manually importing data from a completed simulation to a new simulation model. A new method to change solvers automatically using a self-made Python code is proposed in this paper.

Abstract: In the present investigation, friction stir processing (FSP) is carried out with multi pass processing having 100 % overlap zone on the workpiece material of aluminum alloy 6061 with constant FSP parameters and varying multi pass processing conditions. Novel processing concept of multi pass FSP was performed with different rotation directions (such as clock wise and anti-clock wise directions) and processing directions (such as forward, reverse and revert directions). Surface inspection, macrographs and microstructures of the processed regions are evaluated and compared with each other. Multi-pass FSP with 100 % overlapping of two passes caused intense dynamic recrystallization and resulted in reduced grain size. Hardness of processed zone was found increased in case of two pass FSP. Minimum tensile strength was reported with double sided FSP compare to single pass and two pass FSPs. No major variations in tensile strength were reported in case of single pass and two pass FSPs.

Abstract: Incremental Sheet Forming (ISF) is a promising rapid prototyping technology used to form complex three-dimensional shapes. For forming a part with severely sloped regions, design of multi-stage deformation passes (intermediate shapes or preforms) before the final part, is widely adopted as a desirable and practical way to control the material flow in order to obtain a more uniform thickness distribution and avoid forming failure. However, a problem sometimes encountered in multi-pass forming is wrinkling deformation between two adjacent deformation passes. This may lead to forming process instability and even fracture. The overall quality of the final part may also deteriorate even if the part is formed successfully. In this paper, the wrinkling phenomenon in multi-pass incremental sheet forming is investigated by means of finite element analysis (FEA) and experimental tests to analyse the wrinkling formation mechanism. This research gives an insight into the optimized design of deformation passes in order to eliminate the unwanted wrinkling deformation in multi-pass incremental forming process.

Abstract: Metal spinning on NC machine-tools is a very flexible and complex manufacturing method which has a high efficiency for small series of parts and prototype parts. The algorithms used for calculating the roller trajectory during the metal spinning process are usually complicated and hard to apply into production. This article presents an original application developed using Visual LISP that can be used for calculating and then simulating and testing the roller trajectory in the case of manufacturing rotational complex parts by metal spinning. The simulation prevents any errors that can occur during the process of manufacturing before the parts are actually put into production.

Abstract: The governing equations and the finite element model for the coupled thermo-mechanical multi-pass vertical-horizontal rolling process of a zircaloy strip are established. Considering the temperature-dependent and strain rate-dependent constitutive relation of zircaloy, the numerical simulation of the three-pass V-H rolling process is realized by the coupled thermo-mechanical dynamic explicit finite element method. The computational results such as the plastic deformation, the size variations and the temperature variations in three passes are discussed. The research results indicate that edging by vertical roller benefits improving the sizes of the strip and the temperature variations are rather obvious during the three-pass hot rolling process. The research provides experience and foundations for the FEM simulation of the hot rolling process of composite slabs for nuclear fuel elements.

Abstract: The multi-pass compression deformation of low carbon bainitie steel was carried out on a thermal simulator between a temperature range of 1050~800°Cwith accumulated 60.7% deformation and a deformation rate of 2s-1. The recrystallization behavior of the tested steel during high temperature deformation was discussed after comparatively analyzing the stress-stain curves and austenite deformation structures under different deformation conditions. The results show that with the same strain rate and total deformation, the grain size of recrystallized austenite is mainly determined by pass temperature and pass deformation, especially the latter, while has little relation with quantity of pass. The ultimate deformation stress is determined by ultimate deformation temperature and improved by the increasing quantity of pass.

Abstract: The multi-pass nanometric machining of copper with diamond tool was carried out using the Molecular Dynamics (MD) simulation. The copper-copper interactions were modelled by the EAM potential and the copper-diamond interactions were modelled by the Morse potential. The diamond tool was modelled as a deformable body and the Tersoff potential was applied for the carbon-carbon interactions. It was observed that the average tangential and the normal components of the cutting forces reduced in the consecutive cutting passes. Also, the lateral force components are affected by atomic vibrations and the cross sectional area during the cutting process.

Abstract: The present work concerns the simulation of metallurgical evolutions in 3D multi-pass forming processes. In this context, the analyzed problem is twofold. One point refers to the management of the microstructure evolution during each pass or each inter-pass period and the other point concerns the management of the multi-pass aspects (different grain categories, data structure). In this framework, a model is developed and deals with both aspects. The model considers the microstructure as a composite made of a given (discretized) number of phases which have their own specific properties. The grain size distribution and the recrystallized volume fraction distribution of the different phases evolve continuously during a pass or inter-pass period. With this approach it is possible to deal with the heterogeneity of the microstructure and its evolution in multi-pass conditions. Both dynamic and static recrystallization phenomena are taken into account, with typical Avrami-type equations. The present model is implemented in the Finite Element code FORGE2005®. 3D numerical simulation results for a multi-pass process are presented.

Abstract: In this paper, 3-dimension finite element model was applied to analyze the commercial pure Ti billet subjected to four-pass equal channel angular extrusion process at 400°C with Bc route. The effective strain distribution and the damage within up to four-pass were described with friction conditions in 3D. The propensity for cracks was predicted, which did correlate approximately to the experiment.

Abstract: Ultrafine-grained steel sheets with the chemical composition of 0.15%C-0.74%Mn- 0.01%Si have been prepared using a laboratory rolling mill by Super Short Interval Multi-pass Rolling (SSMR) process, in which the inter-pass time is extremely shortened to enhance the cumulative strain. The SSMR process with a finish rolling around Ae3 leads to ultrafine equiaxed ferrite structure with 1μm in average grain size. In order to clarify the grain refinement mechanism in the SSMR process, the deformation substructure in deformed austenite was simulated using 70%Ni-30%Fe, which was a fcc alloy with equivalent stacking fault energy to C-Mn steels. TEM observations have shown that the dislocation substructure in the Ni-Fe alloy hot-rolled by SSMR process mainly consists of dislocation cells, of which size are refined to less than 1μm with shortening inter-pass time. It is concluded that the SSMR process can accumulate the deformation strain in austenite enough to densely nucleate ferrite inside austenite grains.