Dual approach in non-linear fracture mechanics

A dual approach in fracture mechanics based on complementary energy is proposed. The analysis of the dissipation shows that the thermodynamical force associated with the evolution of a crack is an energy release rate, form of which depends on the presence or not of mechanical discontinuities. This energy release rate is given as a integral based on free or complementary energy. The invariance of sintegrals is analysed and the obtained results in elastoplasticity are discussed. The energy release rate is determined in terms of potential energy or complementary energy, first in elasticity and secondly in elastoplasticity. Associated to these definitions, the law of propagation of the crack is chosen as a Griffith law and the propagation is governed by a normality rule. In this framework we formulate the evolution problem concerning crack propagation in an elastoplastic material. Variational formulations are obtained in terms of rate of displacement, of stresses and of crack length.     

Chemistry effects on the crack susceptibility of structural steels during continuous casting

This work is a review of research results, which have been determined in recent years in order to reveal the effects of the chemical compositions on the high temperature properties of structural steels. Special emphasis has been laid on the solidification structure, phase reactions and precipitates. For this comparison exemplary different structural steel grades have been chosen. The effect of the chemical composition on the solidification structure is shown by increasing Ni mass contents up to 10 %, the influence on the phase transformation is illustrated on the basis of a steel with a Mn mass content of 1.6 % and varying carbon contents. The influence of precipitates has been investigated both on the basis of the Mn/S‐ratio and by microalloyed structural steels with different Nb, V and Ti additions. For all these steel grades the laboratory testing conditions were the same. The high temperature properties of steels can be investigated by high temperature tensile tests; the range of good ductility is determined by the measurement of the reduction of area, e.g. RoA > 50 % or >70 %. The upper limit of the ductility range is the temperature of zero ductility, T_ZD%. The lower limit of the good ductility range is marked by the transition to the ductility minimum II. The experiments for a series of different structural steels show that the hot ductility properties are affected by the metallurgical phenomena mentioned before.     

Determination of crash‐relevant material parameters by dynamic tensile tests

The mechanical properties of eight different steels, representing the wide range of steels for automotive application, are determined by accomplishing high speed tensile tests using flat sheet specimens. The steels chosen for investigations are deep drawing grade DC04, high strength steel ZStE340, three dual phase steels with strengths of 600, 800 and 1000 MPa, a TRIP steel and two austenitic stainless steels 1.4301 and 1.4318. Tests are carried out at five different strain rates within the range of 5‐10^?3 and 200 s^?1, all at room temperature. The results show different strain rate sensitivities according to the different grades of steel. The TRIP steel and both stainless steels show a great potential for energy consumption, when tested at high strain rates.     

Correspondence effects with manual gestures and postures: A study of imitation.

In this study, the authors applied methods and theories from research of stimulus–response compatibility (SRC) to action imitation. In 6 experiments, they adopted the logic of the Simon paradigm (B. Hommel & W. Prinz, 1996) to explore interference between task-relevant symbolic stimulus features (color) and task-irrelevant iconic stimulus features (2 hand gestures and 2 postures). The same 2 hand gestures served as responses. Pronounced correspondence effects for both gestures and postures showed up throughout. In line with theories of SRC, the authors account for these correspondence effects in terms of overlap arising between stimulus and response features in a common representational domain. As a specific extension of this approach, they propose 2 functionally independent mechanisms: One operates movement-based when dynamic information is provided, and the other operates state-based with static postures as stimuli. Implications for theories of both SRC and action imitation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Finding Quadratic Schedules for Affine Recurrence Equations Via Nonsmooth Optimization

Frequently, affine recurrence equations can be scheduled more efficiently by quadratic scheduling functions than by linear scheduling functions. In this paper, the problem of finding optimal quadratic schedules for affine recurrence equations is formulated as a convex nonsmooth programming problem. In particular, sufficient constraints for causality are used generalizing Lamport's condition. In this way, the presented problem formulation becomes independent of the problem size. The research tool AQUAD is described implementing this problem formulation. Several nontrivial examples demonstrate that AQUAD can be effectively used to calculate quadratic schedules for affine recurrence equations. Finally, it is shown how array processors can be synthesized from affine recurrence equations which are scheduled by quadratic functions with a singular Hessian matrix.     

Bemessungsrelevante Kennwerte von Feinbeton für einaxiale Druckbeanspruchung

Design Parameters of Fine Grained Concrete for Uniaxial Compressive Loading Textile reinforced concrete (TRC) allows the design of thin‐structured concrete elements with a high load‐bearing capacity. The mechanical properties and stress‐strain relations under shortterm compressive loading of so called fine grained binder systems which are used as matrix are presented in this paper. The application of known mathematical formulations (e. g. simplified parabola‐rectangle stress‐strain curves for dimensioning purposes, prediction models for characteristic creep parameters) is investigated and design values of fine grained concrete are proposed.     

Parkhaussysteme in Stahlverbundbauweise

Multi‐storey car parks in steel composite construction. Due to technical and economic reasons steel composite structures are a standard construction for open multi‐storey car parks without fire protection. Characteristics of typical structures and slab systems are pointed out. Regular measures to ensure durability of both steel and concrete members are shown.