On the influence of material properties in sheet bending processes

In order to achieve the high performance and precision requirements of modern sheet bending processes, an appropriate implementation of material properties is essential. Experiments have shown that even variations within a lot of a specific material play an important role. For this sake, detailed knowledge of the influence of the specific properties like flow curve, rolling direction, strain rate, anisotropy etc. is required. In a first step, tension tests have been performed for some materials which are frequently used in industrial applications. In order to simulate the sheet bending process, advanced simulation models have been implemented. Detailed parameter studies have been performed, and the essential parameters and their influence on the bending process have been found out. The results have been compared to measurement results of the bending process

Dynamic displacement tracking in viscoelastic solids by actuation stresses: a one-dimensional analytic example involving shock waves

A one-dimensional (1D) analytic example for dynamic displacement tracking in linear viscoelastic solids is presented. Displacement tracking is achieved by actuation stresses that are produced by eigenstrains. Our 1D example deals with a viscoelastic half-space under the action of a suddenly applied tensile surface traction. The surface traction induces a uni-axial shock wave that travels into the half-space. Our tracking goal is to add to the applied surface traction a transient spatial distribution of actuation stresses such that the total displacement of the viscoelastic half-space coincides with the shock wave produced by the surface traction in a purely elastic half-space. We particularly consider a half-space made of a viscoelastic Maxwell-type material. Analytic solutions to this tracking problem are derived by means of the symbolic computer code MAPLE. The 1D solution presented below exemplifies a formal 3D solution derived earlier by the present authors for linear viscoelastic solids that are described by Boltzmann hereditary laws. In the latter formal solution, no reference was made to shock waves. Our present solution demonstrates its validity also in the presence of singular wave fronts. Moreover, in our example, we show that, as was also indicated in our earlier work, the actuation stress can be split into two parts, one of them producing no stresses, and the other no displacements in two properly enlarged problems

On the Use of Piezoelectric Sensors in Structural Mechanics: Some Novel Strategies

In the present paper, a review on piezoelectric sensing of mechanical deformations and vibrations of so-called smart or intelligent structures is given. After a short introduction into piezoelectric sensing and actuation of such controlled structures, we pay special emphasis on the description of some own work, which has been performed at the Institute of Technical Mechanics of the Johannes Kepler University of Linz (JKU) in the last years. Among other aspects, this work has been motivated by the fact that collocated control of smart structures requires a sensor output that is work-conjugated to the input by the actuator. This fact in turn brings into the play the more general question of how to measure mechanically meaningful structural quantities, such as displacements, slopes, or other quantities, which form the work-conjugated quantities of the actuation, by means piezoelectric sensors. At least in the range of small strains, there is confidence that distributed piezoelectric sensors or sensor patches in smart structures do measure weighted integrals over their domain. Therefore, there is a need of distributing or shaping the sensor activity in order to be able to re-interpret the sensor signals in the desired mechanical sense. We sketch a general strategy that is based on a special application of work principles, more generally on displacement virials. We also review our work in the past on bringing this concept to application in smart structures, such as beams, rods and plates

LEAN PANEL BENDER – Einige mechanische Aspekte der Modellierung in Echtzeit für Produktion in Losgröße 1

Nachfolgend werden einige wissenschaftliche Aspekte der Echtzeit-Materialerkennungsstrategie MAC diskutiert, die in der neuen Maschinenfamilie LEAN PANEL BENDER der Firma Salvagnini Maschinenbau realisiert ist und die eine hochpräzise und hocheffiziente Herstellung von komplex geformten Blechprodukten sowohl bei Losgröße 1 als auch in der Serie erlaubt.(VLID)342339

Advanced mechanical simulation models for automatic panel benders

With automatic panel benders complete products are manufactured from sheet metal. In order to achieve short cycle times with high flexibility, a deep insight into the non-linear bending process is required. For this reason, efficient mechanical simulation models have been implemented, combining Finite Element Method, multibody dynamics simulation tools, contact mechanics algorithms and substructuring. Scope of this work is the comparison of several simulation models with measurement results performed on a Salvagnini P4XeD automatic panel bender

Industrial application of advanced adaptive concepts for automatic panel benders

Recently, the requirements on sheet metal production processes have increased significantly. Highest precision and flexibility with efficient energy consumption and short cycle times can be achieved by advanced concepts only. This requires a deep insight into the non-linear bending process. For this sake, efficient simulation models have been implemented to model the bending process: two and three dimensional finite element models combined with multibody simulation tools, contact mechanics algorithms and substructure techniques. The simulation tools have been successfully calibrated by measurement results. With the obtained detailed process knowledge, new adaptive concepts have been introduced, e.g. a smart crowning system in order to achieve straight profiles. The industrial application has shown the advantage of utilizing the above mentioned techniques. The straightness of the bends has been significantly increased, while energy consumption and cycle times have been reduced. Secondly, the development time of new machine concepts has been drastically reduced, such that the first prototype can be transferred to series production within short time. Moreover, the applied strategies show a large potential for future developments

Similarity methods in elasto-plastic beam bending

In industrial metal forming processes a large number of parameters has to be considered. As is well known, this number can be reduced by a non-dimensional representation. Based on the example of an elasto-plastic cantilever beam, the non- dimensional form is derived in the framework of the Bernoulli-Euler theory. In the second step, a Finite Element analyis of a drop-test experiment is performed, and the results are presented in non-dimensional form. The results illustrate the advantage of the normalization

Influence of rate dependent plasticity on a sheet metal bending process

The high demands on precision and quality of industrial sheet metal forming processes are increasing steadily. Therefore, more and more effects concerning the machines but also the material behaviour of the workpiece must be considered. Here, we consider an automatic panel bender of Salvagnini Maschinenbau GmbH. In this application, it turned out that the speed of bending is a relevant influence factor. Goal of this work is to estimate the influence of strain rate on bending forces and the shape of the bent profile

Das Morsche Verfahren zur Berechnung von Biegebalken mit nichtlinearem Werkstoffgesetz

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