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Session 11

Warm Forming Simulation of 7075 Aluminium Alloy Tubes Using LS-DYNA
The demand for lightweight tubular products, designed specifically for transportation and recreational applications, is currently on the rise. In general, performance increase and energy cost reduction are the main reasons justifying the need for these specialty products. Hence, to reach these goals, both industries are turning to complex-shaped tubes for various types of applications. However, high performance aluminium tubes, such as 7075 alloy, provide very low formability characteristics at ambient temperature and do not have the ductility needed for hydroforming-based applications. A 1,000-ton hydroforming press, located at the Aluminium Technology Centre, was equipped with a + 600 oC heating die designed for such tube and sheet forming applications. The die has 10 separate heating zones that can be adjusted independently. The first application was employed to form a tubular bicycle component. To achieve this, a thermo-mechanical model was developed using LS-DYNA to determine the tube temperature distribution around the heating zones. To this end, conduction, convection, radiation and contact heat transfer conductance were the physical phenomena considered in the thermal model. Prior to developing the mechanical model, a heating chamber was designed and fabricated. Tube samples underwent in-chamber testing using a servo-hydraulic system at various temperatures and strain rates. With the results, an elastic viscoplastic temperature-dependent material constitutive law was used to properly predict tube strains and stresses. The finite-element model can predict the necessary tube temperature and gas pressure during the heat-based forming process, thus enabling to obtain optimum formability of 7075 aluminium alloy tubes.
FEM study of metal rolling in grooved rolls
LS-DYNA was used to model the rolling process in grooved rolls. One-pass and two-pass (with rotation of the metal sheet at 90° a fter first pass) rolling in grooved rolls, as well as four-pass rolling in plain rolls and various combinations of these two types of rolling were simulated. With the help of finite-element analysis we estimated the influence of the areas of deformation hardening on the stress-strain state of metal sheet. The developed finite-element model allows analyzing stress-strain state of the system caused by variation of parameters, such as: geometry (design), rolling speed, physical- mechanical properties of materials, temperature and friction coefficient. Process parameters can be fine-tuned to achive the desired improvement of physical-mechanical properties of the rolled metal .
Cowper-Symonds material deformation law application in material cutting process using LS-DYNA FE code: turning and milling
Finite element modeling becomes the huge support in understanding technological process. Besides, there are no so much milling process studies, or these studies are simplified to, as orthogonal cutting process. This paper presents experiences results from orthogonal turning and face milling process. These results were taken for FE model validation and material deformation law constants prediction. In both cases some cutting process simplifications were taken, in order to define contact interaction - to execute meso-scale FE analysis. Concerning FE modeling, calculation scheme is presented in order to evaluate removing material load to cutting tool. Secondly, material behaviour characteristics were evaluated, assuming high speed deformation and material failure. Thirdly, cutting tool path is modeled in order to evaluate his influence on chip formation.
3-Dimensional Forming of Thick Plates - A Comparison of Deep Drawing and an Approach of Rolling and Bending within a Single Process
A variety of industries require certain 3-dimensional formed thick plates, for example in shipbuilding for shell plates. Nowadays the production of curved ship plates is mainly based on the experience of the worker and is performed manually. The results are good and sufficient for the heretofore use in industry, taking into account that the number of curved plates with the same geometry is quite small. Moreover thick plates with a variable thickness are used for instance as so called longitudinal profiles for bridge building. Currently the combination of curved plates with variable thickness does not meet a wide range of applications. But it has high potential in future. In modern shipbuilding this kind of plates offers special applications with a broad scope, e.g. reduction of weight. Renewable energies are another huge market in future. Today, wind turbines are mostly made of glass or carbon fiber. The manufacturing process leads to high precision and quality of the final product. Nevertheless, this fabrication method of rotor blades is very cost intensive and its production technology is not the best in terms of recyclability. In addition to its good reusability, the handling of steel is well known and its fabrication is inexpensive. Due to these facts an idea of rotor blades to be produced from steel arose. However, when desiring a huge output of a product with the same geometry a manual approach is inappropriate. A new process should be repeatable and within a certain accuracy. Deep drawing of the product is a natural choice but is not used for thick plates of enlarged sizes until now. This paper presents a comparison of deep drawing and a new approach. The developed process is based on a superposition of flat rolling and 3-dimensional bending. A major advantage of combining these steps is the opportunity to deliver formed plates with a variable thickness. This paper presents numerical simulations of deep drawing and rolling processes. The results are compared in terms of practicability for the production of rotor blades.