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F. D. Berg M. Pfeiffer O. Schwalb M. Appenheimer W. Döring M. Franke W. Kühn V. Metag W. Niebur R. Novotny J. Ritman M. Röbig H. Ströher A. Boonstra H. Löhner A. Raschke L. Venema H. W. Wilschut N. Brummund W. Henning S. Hlavac R. Holzmann R. S. Simon 《Zeitschrift für Physik A Hadrons and Nuclei》1990,337(3):351-352
π0 -production probability of (9± 2)· 10? 3 per20Ne+Al reaction has been measured at 350 MeV/u using the Two Arm Photon Spectrometer TAPS. This yield is consistent with an interpolation of published π-production rates in heavy ion collisions. 相似文献
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F. D. Berg A. Boonstra H. P. Braak N. Brummund W. Döring M. Franke P. Gonthier W. Henning W. T. Hering S. Hlaváč R. Holzmann B. Krusche W. Kühn H. Lohner R. Lorencz V. Metag W. Niebur R. Novotny R. Ostendorf M. Pfeiffer A. Raschke J. Ritman M. Röbig Y. Schutz O. Schwalb R. S. Simon H. Ströher L. Venema H. W. Wilschut 《Zeitschrift für Physik A Hadrons and Nuclei》1991,340(3):297-302
The production of
0 and mesons has been studied in the reactions20Ne +Al at 350 MeV/u and40Ar + Ca at 1.0 GeV/u. Rapidity distributions and transverse momentum spectra have been measured and are compared to thermal distributions.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday 相似文献
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Isotopic-yield ratios of complex fragments from intermediate-energy heavy-ion reactions 总被引:1,自引:0,他引:1
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Multiscale methods are frequently used in the design process of textile reinforced composites. In addition to the models for the local material structure it is necessary to formulate appropriate material models for the constituents. While experiments have shown that the reinforcing fibers can be assumed as linear elastic, the material behavior of the polymer matrix shows certain nonlinearities. These effects are mainly due to strain rate dependent material behavior. Fractional order models have been found to be appropriate to model this behavior. Based on experimental observations of Polypropylene a one-dimensional nonlinear fractional viscoelastic material model has been formulated. Its parameters can be determined from uniaxial, monotonic tensile tests at different strain rates, relaxation experiments and deformation controlled processes with intermediate holding times at different load levels. The presence of a process dependent function for the viscosity leads to constitutive equations which form nonlinear fractional differential equations. Since no analytical solution can be derived for these equations, a numerical handling has been developed. After all, the stress-strain curves obtained from a numerical analysis are compared to experimental results. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The subjects of the analysis are glass/epoxy‐composites with biaxial weft knitted fabric reinforcement. This fabric combines the advantages of high in‐plane stiffness and delamination resistance provided by the biaxial and knitted fabric, respectively. The asymptotic homogenisation procedure based on the displacement method in conjunction with a finite element model provides the possibility to obtain the effective material stiffness. The effort to generate a pure 3D‐model of the unit cell would be extremely high. A solution of this problem gives the Binary Model where a simplified geometry of the interior structure is used. Additionally, the Voigt and Reuss bounds for the Young's and shear moduli are found by using the 3D orientation averaging procedure. The results obtained with the Binary Model will be compared to these bounds and the experimental results. The work done for this paper is sponsored by the German Research Community (DFG) in the context of the priority program (SPP) no. 1123. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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For a consequent lightweight design the consideration of the nonlinear macroscopic material behaviour of composites, which is amongst others driven by damage and strain–rate effects on the mesoscale, is required. Therefore, the modelling approach using numerical homogenization techniques based on the simulation of representative volume elements which are modelled by the extended finite element method (X–FEM) is currently extended to nonlinear material behaviour. While the glass fibres are assumed to remain linear elastic, a viscoplastic constitutive law accounts for strain–rate dependence and inelastic deformation of the matrix material. This paper describes the process of finding suitable constitutive relations for the polymeric matrix material Polypropylene in the small–strain regime. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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For a consistent lightweight design the consideration of the nonlinear macroscopic material behaviour of composites, which is amongst others driven by damage and strain-rate effects on the mesoscale, is required. Therefore, a modelling approach using numerical homogenization techniques is applied to predict the effective nonlinear material behaviour of the composite based on the finite element simulation of a representative volume element (RVE). In this RVE suitable constitutive relations account for the material behaviour of each constituents. While the reinforcing glass fibres are assumed to remain linear elastic, a viscoplastic constitutive law is applied to represent the strain-rate dependent, inelastic deformation of the matrix material. In order to analyse the influence of the nonlinear matrix material behaviour on the global mechanical response of the composite, effective stress-strain-curves are computed for different load cases and compared to experimental observations. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Venema LB Braak H Löhner H Raschke AE Siemssen RH Sumbera M Wilschut HW Berg F Kühn W Metag V Notheisen M Novotny R Pfeiffer M Ritman J Schwalb O Gobbi A Hildenbrand KD Hlavác S Holzmann R Simon RS Sodan U Teh K Wessels JP Herrmann N Wienold T Kotte R Mösner J Neubert W Wohlfarth D Ostendorf R Schutz Y Brummund N Santo R 《Physical review letters》1993,71(6):835-838
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An increasing importance of composites with sandwich architecture and fibre-reinforced components is recognizable especially in aerospace and light weight industry. Due to the inner structure such materials often exhibit a complex behavior. If the ratio of micro- and macroscopic length scales, l and L, violates the condition l/L ≪ 1, a higher order continuum should be used to describe the macroscopic material behavior correctly. The numerical simulation requires reliable material constants, for which the experimental determination is laborious and sometimes impossible. Alternatively homogenization methods can be used for the numerical identification of overall material parameters. A short introduction to the linear Cosserat theory is followed by an extended homogenization procedure to derive the macroscopic material constants of a linear Cosserat continuum. The parameters obtained with a heterogeneous cell are used to simulate different bending load cases. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献