Hot rolling is one of the most widely used hot metal forming processes by shaping the hot workpiece with cylindrical rolls. Its harsh working conditions, including high loading (up to 0.5 GPa), ...elevated temperature (600–1100 °C) and high speed (above 10 m/s), lead to the problems of high friction, severe wear, oxidation at the tool/workpiece rubbing surfaces. Lubricants are essential to reduce the rolling force, prolong the service life of work rolls, and improve overall process efficiency. In this work, the mixture of sodium polyphosphate and nano-TiO2 as water-based hot rolling lubricants were studied using a laboratory hot rolling mill. Aqueous lubricant with 2 wt.% TiO2 in 20 wt.% sodium polyphosphate demonstrates an excellent lubrication performance with a reduction of a rolling force of 10% compared to pure water lubrication condition. The sodium polyphosphate can not only act as a surfactant to improve the dispersibility of TiO2 nanoparticles in water, but also form an easily sheared glass melt at high temperature to lubricate the workpiece/roller. Focused ion beam and transmission electron microscope analysis of the sliding interface demonstrate that some nano-TiO2 were contained in the polyphosphate melt. The concept that combines the inorganic polymer with nanoparticles to produce the synergy effects of glass lubrication and nanoparticle lubrication can provide new insight into the design of lubricants for the hot metal forming process.
•Water-based lubricant with a mixture of sodium polyphosphate and nano-TiO2 for hot rolling process was studied.•Sodium polyphosphate can act as a surfactant to improve the dispersibility of TiO2 NPs, and lubricate the strips/roller.•Aqueous lubricant with 2 wt.% TiO2 in 20 wt.% sodium polyphosphate demonstrates an excellent lubrication performance.•The synergy effects of glass lubrication and nanoparticle lubrication can be extended to other hot metal forming process.
Flexibility in metal forming Yang, D.Y.; Bambach, M.; Cao, J. ...
CIRP annals,
2018, 2018-00-00, Letnik:
67, Številka:
2
Journal Article
Recenzirano
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Flexibility in metal forming is needed more than ever before due to rapidly changing customer demands. It paves the way for a better control of uncertainties in development and application of metal ...forming processes. Although flexibility has been pursued from various viewpoints in terms of machines, material, process, working environment and properties, etc., a thorough study of the concept was undertaken in order to with problems of manufacturing competiveness and tackle new challenges of manufacturing surroundings. Therefore, in this paper, flexibility in forming is reviewed from the viewpoints of process, material, manufacturing environment, new process combinations and machine–system–software interactions.
In this paper, a novel triangular prism solid and shell interactive mapping element is proposed to solve the coupled magnetic–mechanical formulation in electromagnetic sheet metal forming process. A ...linear six-node “Triprism” element is firstly proposed for transient eddy current analysis in electromagnetic field. In present “Triprism” element, shape functions are given explicitly, and a cell-wise gradient smoothing operation is used to obtain the gradient matrices without evaluating derivatives of shape functions. In mechanical field analysis, a shear locking free triangular shell element is employed in internal force computation, and a data mapping method is developed to transfer the Lorentz force on solid into the external forces suffered by shell structure for dynamic elasto-plasticity deformation analysis. Based on the deformed triangular shell structure, a “Triprism” element generation rule is established for updated electromagnetic analysis, which means inter-transformation of meshes between the coupled fields can be performed automatically. In addition, the dynamic moving mesh is adopted for air mesh updating based on the deformation of sheet metal. A benchmark problem is carried out for confirming the accuracy of the proposed “Triprism” element in predicting flux density in electromagnetic field. Solutions of several EMF problems obtained by present work are compared with experiment results and those of traditional method, which are showing excellent performances of present interactive mapping element.
Flexible metal forming processes are novel ways to meet the growing needs for maintaining economic feasibility in mass production and customization. The flexible forming processes inherently have ...more process parameters to control than conventional processes, and thus they may be less economical. However, owing to the rapid development of computing technology over the last two decades, the numerical simulation approach has gained significant attention for optimizing the process parameters. Based on the numerical analysis, sophisticated theories have also been developed to describe the material deformation characteristics during forming processes. In this paper, incremental sheet metal forming, incremental bulk forming, and flexible roll forming are briefly overviewed with regard to innovative techniques for numerical simulations of various flexible metal forming processes.
In metal forming processes, friction between tool and workpiece is an important parameter influencing the material flow, surface quality and tool life. Theoretical models of friction in metal forming ...are based on analysis of the real contact area in tool-workpiece interfaces. Several research groups have studied and modeled the asperity flattening of workpiece material against tool surface in dry contact or in contact interfaces with only thin layers of lubrication with the aim to improve understanding of friction in metal forming. This paper aims at giving a review of the most important contributions during the last 80 years covering experimental techniques, upper bound solutions, slip-line analyses and numerical simulations. Each of the contributions shed light on the importance of the real contact area and the influencing parameters including the material properties, surface conditions, normal pressure, sliding length and speed, temperature changes, friction on the flattened plateaus and deformation of the underlying material. The review illustrates the development in the understanding of asperity flattening and the methods of analysis.
•Applications of Machine Learning to sheet metal constitutive modelling are reviewed.•Multiple different Machine Learning application methodologies are explored.•Neural Network based algorithms are ...the most prominent in literature.
The numerical simulation of sheet metal forming processes depends on the accuracy of the constitutive model used to represent the mechanical behaviour of the materials. The formulation of these constitutive models, as well as their calibration process, has been an ongoing subject of research. In recent years, there has been a special focus on the application of data-driven techniques, namely Machine Learning, to address some of the difficulties of constitutive modelling. This review explores different methodologies for the application of Machine Learning algorithms to sheet metal constitutive modelling. These methodologies include the use of machine learning algorithms in the identification of constitutive model parameters and the replacement of the constitutive model by a metamodel created by a machine learning algorithm. A discussion about the merits and limitations of the different methodologies is presented, as well as the identification of some possible gaps in the literature that represent opportunities for future research.
Lightweight sheet metals are attractive for aerospace and automotive applications due to their exceptional properties, such as low density and high strength. Sheet metal forming (SMF) is a key ...technology to manufacturing lightweight thin-walled complex-shaped components. With the development of SMF, numerical simulation and theoretical modelling are promoted to enhance the performance of new SMF technologies. Thus, it is extraordinarily valuable to present a comprehensive review of historical development in SMF followed by state-of-the-art advanced characterization and modelling approaches for lightweight metallic materials. First, the importance of lightweight materials and their relationship with SMF followed by the historical development of SMF are reviewed. Then, the progress of advanced finite element technologies for simulating metal forming with lightweight alloys is covered. The constitutive modelling of lightweight alloys with an explanation of state-of-the-art advanced characterization to identify the constitutive parameters are presented. Then, the formability of sheet metals with major influencing factors, the techniques for measuring surface strains in SMF and the experimental and modelling approaches for determining the formability limits are clarified. Finally, the review is concluded by affording discussion of the present and future trends which may be used in SMF for lightweight metallic materials.
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•The original and shear-modified GTN ductile fracture criteria are utilized during the stretch bending process.•The original GTN model can be used only in processes where the stress ...state is the same as the calibration test stress state.•The evolution of damage, principal strains, and displacement of fractures under different forming conditions are investigated.
In this paper, the original and shear-modified GTN ductile fracture criteria are utilized to investigate the fracture behavior of the AA6061-T6 aluminum alloy sheet during the stretch bending process. An appropriate calibration strategy is presented to find the unknown coefficients of the fracture models. In this way, different tension tests such as uniaxial tension, plane strain, notched tension, and shear tension specimens are utilized. Results show that the shear-modified GTN model calibrated by the mentioned tension tests is able to predict the onset of fracture of the stretch bending process with a 5% error, while the original GTN model, calibrated by the uniaxial tension is unable to predict the fracture properly. Since the accuracy of fracture prediction depends on the stress state, the effects of the calibration test on onset of fracture were investigated. It is shown that using the original GTN model with a proper calibration test (plane strain tension) can achieve a good accuracy with 3.5% error in the stretch bending process. In addition, results show that any change in the friction coefficient and bending radius in the stretch bending process can lead to different fracture behavior. Several investigations are carried out to examine the evolution of damage and displacement of fractures in the stretch bending process under different forming conditions.
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