Papers by Keyword: Flattening

Abstract: Sheet metal components with complex geometries are typically recycled by remelting. Direct remanufacturing necessitates the flattening of parts, which requires the implementation of cuts to facilitate unwinding. The exact positioning of these cuts is a complex planning task, because several influencing factors can be considered, such as material usage, ease of flattening, or minimal forming required. This study presents a geometry-based concept addressing this challenge and demonstrates its use for a test geometry. The finite element method is applied to simulate the flattening process of the resulting sections, and the results are evaluated in terms of planarity and induced plastic strain. The findings of the present work indicate a discernible dependency of results on the selection of the flattening directions. In particular, curved areas impact the induced plastic deformation and springback of flattened sections. This is a crucial consideration when planarity is prioritised over material utilisation.

Abstract: Friction is one of the key parameters in sheet metal forming. During forming process, the surface of aluminum sheet undergoes flattening and roughening, leading to changes in real area of contact and therefore friction between tool and workpiece. Predicting real area of contact based on the loading condition is fundamental to model friction in a forming process. For this purpose, we designed a setup to conduct the combined normal load – bulk strain experiments on two different aluminum grades. The real area of contact for each sample was measured and characterized using the surface height probability density distribution. The results show that strain can significantly affect the real area of contact in both A6016 and A5182 grades.

Abstract: This paper considers the softening and flattening treatment of Schizostachyum Lumampao Bamboo as part of a process in its preparation for utilization. Bamboo half-culm samples with thicknesses of either 5.00 mm or 6.00 mm was soaked in palm oil at either of two temperatures (100°C or 160°C) with an application of 50 N load to simulate the flattening process for a period of either 2700 sec. (45 mins.) or 3600 sec. (60 mins.). By measuring the height of the bamboo half-culm before and after the thermal treatment, a relationship was derived between the total heat transferred into the bamboo culms and the flattening behavior. Furthermore, after the flattening, the bending strength of the culms exhibited an exponentially decaying trend and the fracture strength a bi-modal behavior which is confirmed by other studies. This study reports a derived parameter designated as the thermodynamic bending stiffness of about 4 MPa for the flattening process.

Abstract: In multi-high mills, the slim fixed floating work rolls are supported by primary and secondary intermediate rolls and several supporting rolls mounted pairs-wise on supporting shafts. Over the eccentric adjustment of saddle assemblies and hydraulic adjustment device the roll gap adjusts the specific elastic bending deformation of the support system. Based on a hybrid calculation model the influence and limits of an active adjustment device for 20 roll mill will be presented. Thereby the bending deformations as well as the contact deformations of the complete system including the forming process in settings of the elementary plasticity theory (EPT) will be considered.The modeling of the bending deformations of the roll systems are based on FE-Beam elements. The flattening in the contact zone between the rolls will be formulated by a modified non-linear approach, according to Hertz-Johnson. The contact of the deformed zone is aligned in the discretized EPT-roll model by Alexander with Hitchcock-flattening. The iterative analysis of the compact models leads to “force-deformation-relations”, which provides the influence of the variation of the gap. The force-deformation-relations will be detailed discussed in parameter studies of a real 20 roll mill.

Abstract: In order to acquire reasonable blank shape of sheet metals with complex surface, surface flattening method based on triangle and energy model is put forward. According to equal surface principle, the surface is divided into many triangles, which are flattened one after another. Meanwhile, the surface is regarded as energy model, which is used to alter original flattened discrete points. Finally, surface approximate flattening is completed with second development technology based on Pro/ENGINEER platform. In sheet metal manufacturing process, reasonable blank shape is generated quickly.

Abstract: Plasma spray deposition is one of the most important technologies available for producing the high-performance surfaces required by modern industry. In this process, powder of the coating material is fed into high-temperature plasma, which melts and accelerates the powder; the molten particles subsequently hit and solidify on the surface to be coated. To obtain good quality coating, the powder particle must be at least partially molten and hit the substrate with a high velocity. The flattening characteristics of the droplets impinging on a substrate are important determinants in governing the eventual quality of the plasma spray coating. Different codes have been developed in recent years to simulate the overall thermal spraying process, as well as the growth of the 3D coatings, in which entrained particles are modeled by stochastic particle models, fully coupled to the plasma flow. The present investigation was carried out to have an approach to systematize the atmospheric plasma spraying process in order to create a basis for numerically modeling the plasma dynamics, the coating formation mechanisms and to predict the particle thermo- kinetic state at impact.

Abstract: The Coulomb friction model is frequently used for sheet metal forming simulations. This model incorporates a constant coefficient of friction and does not take the influence of important parameters such as contact pressure or deformation of the sheet material into account. This article presents a more advanced friction model for large-scale forming simulations based on the surface changes on the micro-scale. When two surfaces are in contact, the surface texture of a material changes due to the combination of normal loading and stretching. Consequently, shear stresses between contacting surfaces, caused by the adhesion and ploughing effect between contacting asperities, will change when the surface texture changes. A friction model has been developed which accounts for these microscopic dependencies and its influence on the friction behavior on the macro-scale. The friction model has been validated by means of finite element simulations on the micro-scale and has been implemented in a finite element code to run large scale sheet metal forming simulations. Results showed a realistic distribution of the coefficient of friction depending on the local process conditions.

Abstract: An effective and efficient production method of narrow and thin strips made of steel, non-ferrous metals and their alloys is wire flattening in a ball rolling mill. In this device cylindrical rollers have been replaced with balls of diameter ca. 15 mm. Proper selection of deformation process parameters enables to obtain strips with the required geometrical characteristics. Experimental planning method was applied to evaluate the influence of flattening process technological parameters on strip geometrical features. Statistical analysis enabled to determine mathematical models of stainless steel 5XCrNi18-10 strips flattening. It was established that strip widening depends on ball roughness, draft applied, relation of wire diameter to ball diameter, back-tension stress. Strips flatness depends on draft applied. It was observed that strips feature uniform thickness over their width, parallel flat surfaces, narrow dimensional tolerance, high quality surface and naturally rounded edges.

Abstract: Synthesis of Zn-doped PbTiO3 was done using solid-state method. The effects of varying amount of Zn were investigated. Stoichiometric amount of precursors were mixed and ground. The pressed mixtures were calcined at 800°C and sintered at 1,100 °C after regrinding. The samples were characterized using X-ray Diffraction (XRD), Differential Thermal Analysis (DTA), and Scanning Electron Microscopy (SEM). The XRD verifies the existence of PTO in the samples. DTA shows the thermal profile of the samples. Among the different concentrations of Zn that were added, the sample with 5% mole fraction showed the lowest melting point. For 5% mole fraction and greater, SEM images showed flattening and fusing of grains.