Studies in the synthesis of 7,8-benzo[5]metacyclophane

Compound 5 reacted with silver perchlorate in anhydrous benzene to give 3a and in wet acetone to give a mixture of 9 and 10; treatment of 9 with potassium t-butoxide in dimethyl sulphoxide gave 11.     

Anisotropic multiplicative elastoplasticity for the prediction of earings in sheet forming

In this work, the simulation of earings in cup drawing by means of a recently developed anisotropic combined hardening material model is discussed. The model represents a multiplicative formulation of anisotropic elastoplasticity in the finite strain regime with nonlinear kinematic and isotropic hardening. Plastic anisotropy is described by the use of second-order structure tensors as additional arguments in the representation of the yield function and the plastic flow rule. The evolution equations are integrated by a form of the exponential map that preserves the plastic volume and the symmetry of the internal variables. Finite element simulations of cylindrical cup drawing processes are performed by means of ABAQUS/Standard where the discussed material model has been implemented into a user-defined reduced integration solid-shell element. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

FE Modelling of NiTi‐Composed Structures

The present contribution focuses on the finite element modelling of NiTi‐based shape memory alloys. For this purpose, the concept of Helm [1] has been further developed and implemented into a finite element formulation. The model is able to describe the multiaxial behaviour of SMA and therefore useful for the simulation of complex problems. Additional emphasis is put on the modelling of the shape memory effect in composites where the interaction between the alloy and other materials like e.g. polymers plays an important role. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Linewidth Analysis of Spin Labels in Liquids: II. Experimental

This work demonstrates that homogeneous linewidths can be extracted from continuous wave electron paramagnetic resonance spectra and that they quantitatively agree with the predictions of existing relaxation theory. We suggest that relaxation theory can be used to predict experimental lineshapes provided that the simulations properly include sources of broadening. We have found that the rotational correlation times for spin labels in different percentages of glycerol/water mixtures are best modeled by a power law treatment for the viscosity, similar to that for translational diffusion. The translational diffusion coefficients themselves also have a power law dependence on the viscosity for glycerol/water mixtures. The linewidths were linearly dependent upon both the oxygen and the spin label concentration. The hyperfine splittings of all nuclei were observed to decrease linearly with increasing spin label concentration, completely at odds with existing theory which predicts a quadratic dependence upon concentration. The linear dependence was independent of hyperfine splitting until the magnitude of the hyperfine splitting was less than the homogeneous linewidth.     

Infrared and Raman spectra, conformational stability, ab initio calculations and vibrational assignments for trans-3-chloropropenoyl chloride

The infrared (3500-30 cm(-1)) spectra of gaseous and solid and the Raman (3500-200 cm(-1)) spectra of the liquid with quantitative depolarization ratios and solid trans-3-chloropropenoyl chloride (trans-ClCHCHCClO) have been recorded. These data indicate that both the anti (carbonyl bond trans to the carbon-carbon double bond) and syn conformers are present in the fluid states but only the anti conformer is present in the crystalline state. The mid-infrared spectra of the sample dissolved in liquid xenon as a function of temperature (-55 to -100 degrees C) have been recorded. Utilizing conformer pairs at 870 and 725 cm(-1), 1215 and 1029 cm(-1), and 1215 and 1228 cm(-1), the enthalpy difference has been determined to be 136+/-5 cm(-1) (389+/-14 cal mol(-1)) with the anti conformer the more stable form. Optimized geometries and conformational stabilities were obtained from ab initio calculations at the levels of RHF/6-31G(d), MP2/6-31G(d), MP2/6-311 + + G(d,p), MP2/6-311 + + G(2d,2p) and MP2/6-311 + + G(2df,2pd) with only the latter two calculations predicting the anti rotamer to be the more stable form. The vibrational frequencies, harmonic force constants and infrared intensities were obtained from the MP2/6-31G(d) calculations, whereas the Raman activities and depolarization values were obtained from the RHF/6-31G(d) calculations. The spectra are interpreted in detail and the results are compared with those obtained for some related molecules.     

Topology Optimization of 3D Elastic Structures Using Boundary Elements

A numerical approach for the topological optimization of 3D linear elastic problems using boundary elements and the topological derivative is presented in this work. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modelling and simulation of process-integrated powder coating by radial axial rolling of rings

In this paper, we present finite element (FE) process simulations of a new production method used to coat ring-shaped work pieces with functional layers. Similarly to the conventionally applied hot isostatic pressing (HIP), this new coating method is based on powder metallurgy. It is expected to overcome some important drawbacks by integrating the consolidation of the powdery layer material into the hot rolling of the substrate ring. This makes HIP dispensable. Nevertheless several difficulties arise through the process integration. E.g., the presence of the compactable layer requires a different handling of the rolling stage compared with classical ring rolling. FE simulations shall support the design of this new process in order to investigate critical process parameters. For this purpose, new finite element modules have to be developed. A crucial point is the adequate modelling of the layer material. In this regard, we present a rate-dependent finite strain material model that describes the consolidation of the layer material in a thermodynamically consistent way. Moreover, FE process simulations of the new production method are presented and compared with experimental results.     

Experimental and Numerical Study of Paperboard Interface Properties

Laminated paperboard is widely used in packaging products. Interface delamination plays a crucial role in converting paperboard to a carton through the creasing and folding process. Thus, the aim of this study is to experimentally and numerically investigate the interface fracture behavior in pure crack opening mode (mode I) and sliding mode (mode II). Four experimental tests have been evaluated and compared to numerical simulation, namely, the z-directional tensile test (ZDT), double-notch shear test (DNS), double-cantilever beam test (DCB) and end-notched flexure test (ENF). It was shown that, for the paperboard specimens tested, the ZDT test was sufficient to fully characterize the mode I crack growth response. However, the DNS and ENF tests were required to determine the maximum shear stress and the fracture toughness of pure mode II, respectively. Further mixed-mode investigation would enable the analysis of paperboard delamination behavior during the creasing and folding process.