All real materials are heterogeneous, e.g.polycrystalline metal alloys, reinforced concrete, carbon fibre reinforced polymer (CFRP), wood, nuclear graphite or bone.Modelling of such materials involves concurrent simulation of multiple interacting and competing physical processes, acting at different length and time scales, e.g.dislocation flow, ply debonding or separation of atomic layers.In this work we demonstrate a multi-scale fracture framework where cellular automata (CA) represents material evolution, deformation and fracture at micro-or nano-scales and finite elements (FE) are used at structural scales.Fortran coarrays offer simple and intuitive data structures for 3D CA modelling of material microstructures.Fortran 2008 and 2015 coarrays are native Fortran means for SPMD style of parallel programming.CA is a structured grid and thus is well suited for implementation in coarrays.Design of a coarray cellular automata microstructure evolution library CGPACK is described.Simulations of solidification, recrystallisation and grain coarsening, and fracture can be performed at arbitrary length and time scales with CGPACK.We show how coarrays can be used together with an MPI FE library to create a two-way concurrent hierarchical and scalable multi-scale CAFE deformation and fracture framework.A highly portable MPI FE library ParaFEM was used in this work.Both CGPACK and ParaFEM are developed and distributed under BSD license, allowing free use, modification and redistribution in academia and for profit.The CAFE framework is based on mapping coarrays to MPI data structures.There are identical numbers of MPI ranks and coarray images in the framework.Data stored in coarray variables on each coarray image is mapped onto data stored on each MPI process, based on fact that the material and the structure occupy the same physical space.Continuum mechanics quantities, e.g.stress and strain tensors are passed from FE integration points to the CA, where they are distributed over cells (localisation) based on existing damage and microstructure heterogeneity.After each fracture propagation increment at the CA scale, the microstructural damage is encoded in a scalar damage variable (homogenisation) which is passed back to
In this study, theoretical models and design procedures of the behavior of thin-walled simply supported steel beams with an open cross section under a large torsional effect are presented. I-sections were chosen as the cross section types. Firstly, the widely used differential equations for the lateral buckling for the pure bending moment effect in a beam element were adopted for the various moment distributions along the span of the beam. This solution was obtained for both mono-symmetric and bisymmetric sections. The buckling loads were then obtained by using the energy method. When using the energy method to solve the problem, it is possible to locate the load not only on the shear center but also at several points of the section depth. Buckling loads were obtained for six different load types. Results obtained for different load and cross section types were checked with ABAQUS software and compared with several standard rules.
The here presented wind tunnel study focuses on the Reynolds- and Mach number dependence on the aeroacoustic noise emitted by the first bogie of the 1 : 25 scaled model of the Next Generation Train. The knowledge of the aeroacoustic scaling is essential for the correct interpretation of measurements with down-scaled models. For the sound source analysis the microphone array technique is applied. To achieve comparable aerodynamic conditions, the Reynolds number realised with the scaled model must be similar to the one obtained for the full-scale train. Therefore, cryogenic wind tunnel measurements were conducted for which the Reynolds number was increased by cooling the fluid. In addition, this facility admits to vary the Mach- and Reynolds numbers independently, which is very valuable to gain insight into the aeroacoustic scaling, without changing the scale of the model. A double-model setup is used, which provides a realistic underfloor flow. The analysis of the acoustic spectra reveal strong tonal components, which are sensitive to variations of the Mach - and Reynolds number.
In this paper the pressure-wave generation and propagation in a rail tunnel and the influence of an extended tunnel portal on this phenomenon are discussed. A new test facility is introduced, which was built in 2010 and allows the investigation of the pressure waves due to train-tunnel entry. It is a moving-model rig, which enables to investigate a realistic tunnel passage of the train. The first measurements of the pressure waves generated by a high-speed train entering a tunnel, which were done with the new facility, and their results are presented here. Furthermore a hood acting as extension of the tunnel portal is studied.
The European train control system (ETCS) is one of the core parts of the European rail traffic management system (ERTMS) [1]. It has been specified by a European team in the last years [2]. The specification is published by the European Railway Agency (ERA). Different industry suppliers developed products according to this specification. Now those products have to be tested according to the testing requirements. Technical tests are used to prove that the product fulfil the technical requirements of the specification. They are called the conformity tests. Operational tests are used to show that the system fulfils the operational requirements of the railway operator. The idea presented here aims to show, that technical tests as well as operational tests can be defined according to a common standard. The main advantage of this approach is to perform the tests in the same lab environment. The system under test should be integrated in the Lab only once. Both kinds of tests can be executed without any modification of the lab integration. This leads on the one hand to a significant reduction of integration effort in the lab and on the other hand to a reduction of redundancy in the tests itself. This second increase in efficiency needs a methodical basis for the definition of the tests to be executed. This methodical base supports the optimization of the tests. Practically seen the approach allows identifying which parts of the requirements are already tested in the technical tests. In the next step the operational tests are designed by using test cases from the technical tests and adding the missing operational test cases. Finally the operational tests can be designed by focussing on the requirements which not tested yet. The full contribution shows the method of designing tests and the suitable test environment. As a perspective an approach for the generation of field test templates from the operational lab tests is given. The approach used for the conformity tests for ETCS can be extended for operational and safety lab tests as well as for operational field tests. The method of the generation of the test sequences can be used for the different types of tests. The optimization criteria as well as the rules for the parameterization differ for the different kinds of tests. If the same approach for the formalisation and parameterization is used, the lab environment can be used for any type of test.
Aim of WIM Systems (Weight In Motion) is to evaluate the loading conditions (axle/wheel weight) of a railway vehicle in motion from the measurement of induced stress-deformations on railway infrastructure (rails, sleepers, etc.).This kind of measurements are quite important for safety and maintenance purposes in order to verify the loading conditions of a wide population of vehicles using a limited number of WIM devices distributed on the rail network.The evaluation of axle loading conditions is quite important especially for freight wagons, more subjected to the risk of unbalanced loads which may be extremely dangerous both for vehicle safety and infrastructure maintenance costs.Also some typical defects of rolling surfaces such as wheel flat should be identified especially by considering frequency and time domain analysis or mixed/hybrid approaches as wavelet transformations.In this work a simplified FEM model of vehicle-rail interaction is used to investigate potential performances and robustness of a proposed WIM algorithms against disturbances, bandwidth/resolution limitations and sensors and estimators bias errors.
