Computational morphogenesis of free form shells: Filter methods to create alternative solutions

p. 536-547Actual trends in numerical shape optimal design of structures deal with handling of very large dimensions of design space. The goal is to allowing as much design freedom as possible while considerably reducing the modelling effort. As a consequence, several technical problems have to be solved to get procedures which are robust, easy to use and which can handle many design parameters efficiently. The paper briefly discusses several of the most important aspects in this context and presents many illustrative examples which show typical applications for the design of light weight shell and membrane structures.Bletzinger, K.; Firi, M.; Linhard, J.; Wüchner, R. (2009). Computational morphogenesis of free form shells: Filter methods to create alternative solutions. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/654

Modeling of Self-Organizing Systems: An Overview

This paper gives a systematic overview on modeling formalisms suitable for modeling self-organizing systems. We distinguish between micro-level modeling and macro-level modeling. On the micro level, the behavior of each entity and the interaction between different object must be described by the model. Macrolevel modeling abstracts from the individual entities and only looks at the behavior of the system variables of interest. The differentiations between discrete and continuous time and between discrete and continuous state space lead to different descriptions of the model

Calculation of static deformation of membrane structures under the load of ponding water

Ponding refers to a phenomenon of accumulation of water on top of a structure. Even though most light weight membrane structures are designed to prevent its occurrence, it can be initiated in some cases during rainfall by an event such as drifted snow settling on the surface of the structure causing a local depression of the membrane structure. The present work proposes a method to calculate the static deformation of a membrane structure due to a given volume of ponding water. The method involves coupling of a structural solver for the membrane and a volume conserving solver representing the static behavior of an incompressible fluid. The coupling is performed in a partitioned manner with the linearized behavior of the incompressible fluid incorporated in the structural equations to accelerate the coupling iterations. Using this method, the final deformation of the structure due to ponding is calculated by applying loads due to a fixed volume of water

Neural Network-Based Surrogate Models Applied to Fluid-Structure Interaction Problems

Traditional computational methods face significant challenges with ever-increasing complexity in the problems of engineering interest. One category of problems that suffer from this phenomenon is those where Fluid-Structure Interaction (FSI) is present. One set of problems that suffer from this phenomenon is those where Fluid-Structure Interaction (FSI) is present. FSI simulations are traditionally time-consuming and computationally extremely expensive. Potential alternatives rely on using a surrogate model to substitute one or more systems involved. A promising approach employs artificial neural networks as the basis for such a surrogate model combined with strong physics simulations based on finite element methods (FEM). This approach requires the seamless integration of AI algorithms and packages into the simulation workflow. Such an example is the NeuralNetworkApplication developed in KratosMultiphysics. The routines related to the neural networks are executed through an interface with the Keras API. Mok's benchmark is chosen as the study case to test the capacity of the previous method applied to FSI problems. Two cases in which one of the systems is substituted by a neural network-based surrogate model are analyzed. Strong and weak coupling scenarios are considered. The results present improvements in simulation time without sacrificing accuracy, especially when compared with the original benchmark. This contribution discusses the influence of the original data and network architecture on the simulation outcome and different considerations for generating surrogate models for FSI

The eXtended Updated Reference Strategy for the form finding of tensile structures

In this paper, the eXtended Updated Reference Strategy is presented. Starting from the established Updated Reference Strategy all related issues, which are involved for this methodology, are identified. It will be shown that the eXtended Updated Reference Strategy is able to solve the “correct” form finding problem in one non-linear iteration step. By applying the eXtended Updated Reference Strategy to well-known form finding problems the difference in convergence in comparison to establish methods like the force density method or the Updated Reference Strategy is discusse

Advanced cutting pattern generation – Consideration of structural requirements in the optimization process

This paper presents extensions to optimized cutting pattern generation through inverse engineering regarding structural requirements. The optimized cutting pattern generation through inverse engineering is a general approach for the cutting pattern generation which is based on the description of the underlying mechanical problem. The three dimensional surface, which is defined through the form finding process, represents the final structure after manufacturing. For this surface the coordinates in three dimensional space Ω3D and the finally desired prestress state σprestress are known. The aim is to find a surface in a two dimensional space Ω2D which minimizes the difference between the elastic stresses σel,2D→3D arising through the manufacturing process and the final prestress σprestress. Thus the cutting pattern generation leads to an optimization problem, were the positions of the nodes in the two dimensional space Ω2D are the design variables. In this paper various improvements to the method will be shown. The influence of the seam lines to the stress distribution in the membrane is investigated. Additionally, the control of equal edge length for associated patterns is an example for important enhancement

Energieeffiziente und rechtzeitige Ereignismeldung mittels drahtloser Sensornetze

This thesis investigates the suitability of state-of-the-art protocols for large-scale and long-term environmental event monitoring using wireless sensor networks based on the application scenario of early forest fire detection. By suitable combination of energy-efficient protocol mechanisms a novel communication protocol, referred to as cross-layer message-merging protocol (XLMMP), is developed. Qualitative and quantitative protocol analyses are carried out to confirm that XLMMP is particularly suitable for this application area. The quantitative analysis is mainly based on finite-source retrial queues with multiple unreliable servers. While this queueing model is widely applicable in various research areas even beyond communication networks, this thesis is the first to determine the distribution of the response time in this model. The model evaluation is mainly carried out using Markovian analysis and the method of phases. The obtained quantitative results show that XLMMP is a feasible basis to design scalable wireless sensor networks that (1) may comprise hundreds of thousands of tiny sensor nodes with reduced node complexity, (2) are suitable to monitor an area of tens of square kilometers, (3) achieve a lifetime of several years. The deduced quantifiable relationships between key network parameters — e.g., node size, node density, size of the monitored area, aspired lifetime, and the maximum end-to-end communication delay — enable application-specific optimization of the protocol

Coupling of structural solver and volume-conserving solver for form-finding of membrane structures subjected to ponding

The current study deals with coupling of a volume conserving solver and a structural solver to calculate the static deformation of flexible structures under the load of a given volume of water. The volume-conserving solver contains a horizontal plane representing the free surface of the fluid, which is moved in the non-linear iterations to conserve the volume. The Partitioned approach is chosen to have code modularity and reusability with many structural codes