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Oya T.,University of Tokyo | Tiesler N.,Wurzburg-Schweinfurt University of Applied Sciences | Kawanishi S.,University of Tokyo | Yanagimoto J.,University of Tokyo | Koseki T.,University of Tokyo
Journal of Materials Processing Technology

In this study, the bending formability of multilayered steel sheets is evaluated by tensile tests, V-bending tests, and hemming tests. Enhanced formability was observed in these experiments, namely, the constituent high-strength materials were elongated beyond the original fracture strain limit. As a result of this effect, multilayered steel sheets were successfully formed in V-bending tests and even in hemming tests. Observations using a scanning electron microscope verified that no delamination occurred at interfaces. To represent the geometrical features of a multilayered steel sheet, a solid-element model under an isostrain condition was utilized in finite element modeling, where the rule of mixtures was adopted to obtain the flow curve of the constituent high-strength material, and a good agreement with experimental results was observed. Analyses using this finite element model were conducted to investigate the effect of the geometry on the springback of multilayered steel sheets undergoing V-bending. © 2010 Elsevier B.V. All rights reserved. Source

Herrmann V.,Wurzburg-Schweinfurt University of Applied Sciences
KGK Kautschuk Gummi Kunststoffe

Dynamic mechanical analysis at different temperatures and frequencies of Carbon Black and Silica loaded rubbers is carried out and mastercurves are created. For higher filler loadings poor coincidence of the isothermal curves can be observed. In this case no proper mastercurves can be constructed by horizontal shifting only. A vertical shift factor is introduced in order to get proper mastercurves of the storage as well as loss modulus of the highly loaded rubber systems by means of additional subsequent vertical shifting of the isothermals. The meaning of this vertical shift factor is discussed and this treatment leads to a filler network agglomeration energy which can be interpreted as a measure of the thermal activated part of the filler network. Source

Yanagimoto J.,University of Tokyo | Oya T.,University of Tokyo | Kawanishi S.,University of Tokyo | Tiesler N.,Wurzburg-Schweinfurt University of Applied Sciences | Koseki T.,University of Tokyo
CIRP Annals - Manufacturing Technology

The formability of multilayer metallic sheets is evaluated by tensile, V-bending, hat bending and hemming tests. A monolithic type-420J2 stainless steel sheet cannot be formed because of poor elongation as small as 1.7%. Marked enhancement of the bending formability was observed in the bending of type-420J2 stainless steel sheets when they are layered by type-304 stainless steel sheets and composed into a multilayer metallic sheet. The mechanism of the enhancement of the formability of type-420J2 stainless steel in a multilayer metallic sheet is investigated analytically by focusing on the delay of the initiation of necking, and by performing stress analysis by finite element method (FEM). © 2010 CIRP. Source

Wimmer G.,Wurzburg-Schweinfurt University of Applied Sciences
Proceedings - International Conference on Computer Communications and Networks, ICCCN

The simulation of transient magnetic field problems requires the repeated and successive solution of high-dimensional linear systems with near-identical system matrices and different righthand side vectors. The combination of conjugate gradient method with subspace projection methods is shown. Additionally, the formulation for the azimuthal component of the magnetic vector potential for axisymmetric magnetostatic applications reveal a singularity which is the source of numerical instability. A variable transformation is introduced to remove the singularity from the numerical scheme and to move it to the postprocessing. © 2014 IEEE. Source

Glock C.H.,University of Wurzburg | Schwindl K.,Wurzburg-Schweinfurt University of Applied Sciences | Jaber M.Y.,Ryerson University
International Journal of Services and Operations Management

This paper develops an economic order quantity (EOQ) model with fuzzy demand that may vary between upper and lower limits. The imprecision in demand is assumed to reduce with time because of learning. The results from the developed model are compared to those of an EOQ model with fuzzy demand and no learning. It is shown that learning in fuzziness improves the information base for future orders by reducing uncertainty, which favours delivering demand in smaller lots which are delivered more frequently. As the learning rate increases and fuzziness in demand reduces, the results were shown to converge to those of the classical EOQ model. Copyright © 2012 Inderscience Enterprises Ltd. Source

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