Papers by Keyword: Metal Forming

Abstract: Since the beginning of the 90’s, research activities focused on friction and wear in metal forming have been developed at the LAMIH UMR CNRS 8201 in Valenciennes. Specific methodologies have been designed to optimize a given forming process (bulk forming process or sheet forming process). These methodologies involve prototype benches which have been built to reproduce contact conditions encountered in manufacturing plants by taking specimens and contactors from the real industrial workpieces and tools. The evaluation of the friction coefficient added to the fine analysis of the surfaces have helped us to better understand friction and wear during processes. These facilities have been settled by numerical simulation at meso and macro scales by means of finite element methods. So, this paper is the sum up of the output of these methodologies with a specific focus on wear and lubrication, at room and hot temperatures.

Abstract: In this study, temperature distribution that occurred during cold and hot rolling of AA5454-O alloy has been investigated. Temperature variation taking place in the aluminium alloy that has undergone plastic deformation between the rollers during hot and cold rolling process is of major importance in terms of determining the positive and negative characteristics or features which such temperature variation adds to the formation of the internal structure of the material concerned. Temperature distribution has been measured by use of the installed laboratory equipment and respective data recorded has been presented in the form of graphic charts. Temperature distribution has varied depending on the application of hot or cold rolling process and it has been noted that variations in terms of temperature reduction took place depending on the number of roll passes. While average temperature variation has occurred as a 16°C increase in the case of cold rolling, it has been observed that such variation appeared as a 100°C decrease on the average in the case of hot rolling.

Abstract: This paper presents the use of meta-heuristics one of the most popular types of optimisation methods for solving real engineering applications. The general procedure of meta-heuristics is detailed. The applications are related to metal forming processes. Two design examples, optimisation of a strip coiling process and the non-circular wire drawing process, are demonstrated. The results obtained are compared while advantages and disadvantages of using the optimisers are discussed.

Abstract: The feasibility of combining spinning, shear forming and flow forming processes has been demonstrated through manufacturing of a representative of a hub component using industrial scale hybrid-forming machine available at the Advanced Forming Research Centre (AFRC). The manufacturing cycle consisted of single to multiple passes of shear forming, spinning and flow forming. The research has proven that the spinning, shear forming and flow forming can be combined using a single machine with a single set of tooling and single process cycle. Circumferential and axial cracking was observed in initial set of trials which were eliminated using a series of experiments. The methodology that was used in these series of trials to remove the cracks/defects that may occur during forming of such component is presented here.

Abstract: Investigation of the mechanical behaviour of multilayered metallic materials obtained during novel joining technique called Constrained Compression (CC) is presented. 316L stainless steel material was used in CC to achieve multi-layered structure. Microstructural study based on light microscopy was performed focused presumably on the joining areas of the deformed metallic laminate. The qualitative and quantitative assessment of the processing conditions, microstructure development and microhardness distributions showed the possibility of achievement good bonding quality. Experimental study was supported by numerical stress and strain analysis. It has been shown that determination of the optimum processing parameters allowed for improvement of the joining process, which in turn will enable to produce multilayered metallic materials on a larger scale.

Abstract: The theory of sheet and bulk ideal plastic flows is used for the preliminary design of metal forming processes. The present paper develops an approach to incorporate the Cockroft and Latham ductile fracture criterion in this design method for stationary bulk flows. In particular, it is demonstrated that the initiation of ductile fracture can be predicted without having the ideal flow solution for stress and strain in the plastic zone (it is only necessary to know that the solution exists). Using the approach proposed the initiation of ductile fracture in axisymmetric drawing is predicted.

Abstract: Seamless rings are applied in several industrial sectors and are mainly produced by radial-axial ring rolling. Ring climbing is one of the most occurring process errors leading to a distortion of the ring’s cross section. This paper presents the determination of the influencing factors and their impact and correlations on the process error of ring climbing via Design of Experiment. The highest impact on the climbing height of a ring has the adjustment of the rolling table and the guide rolls. Relatively low but still noticeable is the influence of the process parameters of the rings displacement and the unequal axial rolling speeds. With this knowledge it will be possible to develop, test and implement a rolling strategy that may reduce or avoid ring climbing successfully.

Abstract: Due to the limitations of other processes in joining different types of material, mechanical joining methods can be alternatively used. Joining by upset bulging can be employed for joining tubes with other structures such as sheets, plates, tubes or profiles as well as for joining different materials. In spite of successful industrial applications of this joining process, material damage is still a challenge. This damage affects the resistance of the created joint to service loads. Thus, in this paper, a local heating is studied, which aims at avoiding pre-damage or failure of the joint. A parametric FE model is developed to analyse the influence of local heating on the bulging process. It is found that the process window set by the bulge length suitable for joining is widened, but only to a minor extent. The marginal influence of local heating on the bulge geometry allows designing the process in the same way as room temperature processes. Metallographic investigations confirm the damage-free bulging of tubes by forming at elevated temperatures. Another important result is that tubes can be equipped with predefined bulge zones by local heating zones to 700 °C for 15 seconds for example. This enables bulging of tubes during joining by applying an axial load only, without using tools to define the location of the bulge or its length, thus enabling joining operations with limited access.

Abstract: The article presents the results of computer modelling and numerical simulations the deformation and stresses occurring in the surface layer of the product after the burnishing cold rolling operation. Technological processes were considered as a geometrical and physical boundary and initial value problem, with unknown boundary conditions in the contact zone. An incremental model of the contact problem between movable rigid or elastic body (tool) and elastic/visco-plastic body (object) in updated Lagrange formulation, for spatial states (3D) was considered. The incremental functional of the total energy and variational, non-linear equation of motion and deformation of object on the typical step time were derived. This equation has been discretized by finite element method, and the system of discrete equations of motion of objects was received. For solution of these equations the explicit methods was used. The applications were developed in the ANSYS/LS-Dyna system, which makes possible a complex time analysis of the states of displacements, strains and stresses, in the workpieces in fabrication processes. Application of this method was showed for examples the modelling and the analysis of the asperities with apex angles θ = 85°, 120° and 156°. The Bielajew point using finite elements methodology was indicated. The simulation results were verified experimentally.

Abstract: The article represents the theoretical basis for the generation of virtual material models with the given crystallographic orientation (CGO) of the structure in metals and alloys with the cubic crystal lattice. The obtained functional interrelations allow to take into consideration a metal sheet CGO in technological calculations of metal forming processes and, most significantly, a priori by means of calculations to determine the structure CGO meeting the requirements of increasing the materials formability and the product performance. It is given an example of the implementation of the calculated CGO of the structure while rolling can sheet from aluminum alloy 3104.