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Laser beam welding is a metal fusion technique that, with its high advance speed and low thermal distortion, is used more frequently nowadays in industry. During welding, the solidification front is located in the so‐called mushy zone, which forms the transition region between the completely solidified and mixture zone of solid and fluid material behind the laser beam. In this zone, various process...
For modeling materials with size‐effects, the classical Cauchy linear elasticity theory and first‐order homogenization procedures are insufficient. Enriched continua are able to capture such phenomena in principle. In this work, we model the size‐effects of metamaterial beams via the relaxed micromorphic continuum. The material parameters of the relaxed micromorphic model are evaluated. We present...
Laser beam welding is a contact free fusion technique which has gained importance during the last years due to rising need for automatization in industrial processes. However, a well‐known problem is the formation of solidification cracks in the rear region of the melting pool. In order to investigate the formation of solidification cracks which is highly dependent on the chemical composition, the...
The cost‐ and time‐efficient design of today's manufacturing processes is closely linked to numerical simulations. By developing and applying suitable simulation models, component properties can be specifically predicted and, if necessary, modified according to the customer's specifications. One important aspect of this is the adjustment towards advantageous residual stress profiles, for example to...
In this contribution, an adaptive method for Model Order Reduction (MOR) is presented for simulating physically non‐linear material behavior of micro‐heterogeneous structures. The method is purely online and includes a Galerkin projection, which is performed using a projection operator initially gained by a Proper Orthogonal Decomposition (POD). By this projection, the number of degrees of freedom...
The FE2 method, cf. [1], a direct micro‐macro homogenization approach, has become a standard procedure for scale‐transition applications. Therein, the modeling of a micro‐heterogeneous material described by a representative volume element (RVE) based on realistic microstructures can give rise to a barely unmanageable computational effort. Alternatively, statistically similar RVEs (SSRVEs) can be used,...
Mechanical metamaterials are media with periodic unit cells comprised of tailored geometry in order to accomplish extraordinary bulk mechanical properties which can not be found in conventional materials. However, metamaterials exhibit size‐effect phenomena which can be captured by enriched continua. In this work, the relaxed micromorphic model will be used to reproduce the mechanical response of...
In the field of single crystal plasticity, different algorithms exist for the solution of the constitutive equations. They can be grouped into rate independent and rate dependent approaches, where both classes are governed by inherent shortcomings, as discussed in, e.g., [3]. This contribution outlines an algorithmic formulation for single crystal plasticity at small strains for the rate independent...
The relaxed micromorphic model is a generalized continuum model that reduces the complexity of the general micromorphic theory [1] and shows many advantages such as the bounded stiffness for small sizes [2–4]. It keeps the full kinematics of the micromorphic theory but employs the matrix Curl operator of a second‐order micro‐distortion field for the curvature measurement. The solution of the micro‐distortion...
The direct consideration of residual stresses can positively influence the properties of a component and offers a new perspective compared to the typical strategy of avoiding residual stresses. Instead of minimizing residual stresses in forming processes, their consideration can positively influence the properties of the final component. For instance, the targeted adjustment of residual stresses can...
In this paper, an adaptive reduced order method for small strain elasto‐plasticity is discussed. This method works purely online, meaning no preliminary offline calculations have to be conducted. Using a GALERKIN projection, the high‐fidelity problem is reduced to a lower vector space. For this, the basis is extracted from an initial POD after the first few load steps of the simulation. Later on,...
The paper presents a comparative study of the finite element method (FEM) and the scaled boundary finite element method (SBFEM) for the numerical evaluation of the volume‐averaged stress of composites. Two‐dimensional meso‐scale models of concrete represented by digital images and discretized using an automatic mesh generation algorithm are considered. The different computational approaches are discussed...
The consideration of residual stresses in forming processes is a promising opportunity to influence the final component's properties in a positive manner. Instead of their minimization, a targeted application of residual stresses can extend life time or durability and enhance manufacturability of metallic components. For this reason, detailed experimental and numerical analyses are an object of current...
In this contribution, an online adaptive reduced order model is presented for small‐strain elasto‐plasticity. Using the GALERKIN method, the problem is projected to a lower subspace giving a reduced problem based on the displacement field snapshots. The adaptivity lies in the update of the projection operator, which is carried out in different parts of the simulation if certain criteria related to...
The paper presents a novel approach for rate‐independent single crystal plasticity based on the Infeasible Primal‐Dual Interior Point Method in a small strain framework. Therein, the principle of maximum dissipation together with the yield functions on the slip systems in the crystal are considered as the constrained optimization problem. The constraint conditions adapted using slack variables and...
The adjustment of targeted residual stress states is important in order to improve the properties of a component. Here, especially hot forming processes offer a meaningful potential since a number of parameters such as deformation state, temperature profile or cooling media can be adapted independently. This publication presents first simulation steps for the calculation of residual stresses on microscale...
Dual‐Phase (DP) steels exhibit excellent macroscopic properties such as high strength, ductility and energy absorption. However, the increase of strength also results in a large springback behavior which should be considered for an optimal production process design. Thus, accurate modeling of springback during forming applications is important. The macroscopic behavior of DP steels is closely tied...
A precise representation of the residual stresses, their development in numerical simulations as well as their interpretation in experimental results requires a profound knowledge of the thermal, mechanical as well as metallurgical properties of the considered material. This publication presents initial approaches for the calculation of residual stresses. For this purpose, the thermo‐mechanical behaviour...
A key function of the brain is to filter essential information and store it in the form of stable, long-term memory (LTM). We demonstrate here that the Dunce (Dnc) phosphodiesterase, an important enzyme that degrades cAMP, acts as a molecular switch that controls LTM formation in Drosophila. We show that, during LTM formation, Dnc is inhibited in the SPN, a pair of newly characterized serotonergic...
Understanding how the various memory components are encoded and how they interact to guide behavior requires knowledge of the underlying neural circuits. Currently, aversive olfactory memory in Drosophila is behaviorally subdivided into four discrete phases. Among these, short- and long-term memories rely, respectively, on the γ and α/β Kenyon cells (KCs), two distinct subsets of the ∼2,000 neurons...
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