bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physically constrained deep recurrent neural network for stiffness computation of plate structures
Authors: Tandale Saurabh Balkrishna , Markert Bernd , Stoffel Marcus 
Published: March 2023

AbstractIn the present study, we introduce two Neural Network (NN) enhanced methods to approximate the local tangent stiffness matrix and the internal force computation for a 2D Finite Element. The proposed model is based on Long‐Short Term Memory (LSTM), which inherently captures the required path‐dependent behavior through its internal parameters. Furthermore, we propose an enhanced training algorithm where an additional loss term corresponding to the derivative of the NN following the Sobolev training procedure is introduced. Such a learning algorithm combines the data‐driven approach with the necessary physical constraint to train the NN. Thus, the present work focuses on introducing the NN at an element level for plate structures taking physical non‐linearities into account. The performance of the proposed methods is demonstrated in an academic example showing a maximum of 90.564% boost in simulation speed.
Simulations of the snap‐through behavior of a fiber reinforced elastomer structure for the design of a simple clamping mechanism
Authors: Schasching Marius M. , Duy Robert , Todt Melanie , Pettermann Heinz E. 
Published: March 2023

AbstractA glass fiber reinforced elastomer (FRE) sheet is used to design a simple clamping mechanism for prospective engineering applications. The mechanism is based on the phenomena of snap‐through buckling of a segment of a shallow cylindrical shell. It is simply supported at the straight edges and actuated by edge moments. The main objective of such a mechanism is the resulting clamping force, being related to the response of the material under bending. Bending includes compressive stresses, and since the fibers are embedded in a very soft matrix, it is important to understand their contribution to the compressive stiffness of the FRE sheet. For this purpose, numerical simulations by means of the Finite Element Method are performed and a simulation strategy for predicting the clamping force of the mechanism is presented. The clamping forces predicted for FRE composites with and without the contribution of fibers to the compressive stiffness are compared to that of the pure elastomer. The results illustrate the potential of FRE based structures in mechanism‐like applications. If an adequate clamping force is desired, the pure elastomer is not suitable for being used in this kind of clamping mechanism and the fiber reinforcement is necessary. If the fibers contribute to the compressive stiffness, a significantly higher clamping force is predicted. Furthermore, the FRE based structure shows a complex snap‐through deformation pattern, which has to be taken into account in the design of the mechanism and which requires non‐trivial simulation strategies.
Material‐informed training of viscoelastic deep material networks
Authors: Gajek Sebastian , Schneider Matti , Böhlke Thomas 
Published: March 2023

AbstractDeep material networks (DMN) are a data‐driven homogenization approach that show great promise for accelerating concurrent two‐scale simulations. As a salient feature, DMNs are solely identified by linear elastic precomputations on representative volume elements. After parameter identification, DMNs act as surrogates for full‐field simulations of such volume elements with inelastic constituents.In this work, we investigate how the training on linear elastic data, i.e., how the choice of the loss function and the sampling of the training data, affects the accuracy of DMNs for inelastic constituents. We investigate linear viscoelasticity and derive a material‐informed sampling procedure for generating the training data and a loss function tailored to the problem at hand. These ideas improve the accuracy of an identified DMN and allow for significantly reducing the number of samples to be generated and labeled.
Hybrid Position‐Compliance Control of Redundantly Actuated Parallel Kinematic Manipulators Equipped with Serial Elastic Actuators
Authors: Kordik Thomas , Gattringer Hubert , Müller Andreas 
Published: March 2023

AbstractRedundantly actuated parallel kinematic manipulators (RA‐PKM) are ideal candidates in robotic applications combining dynamic performance with high accuracy. Actuation redundancy further allows for modulation of the end‐effector (EE) stiffness. A recent trend in robotics is the use of inherently compliant and elastic components, eventually leading to soft continuum robots, which shall provide tailored solutions for human‐robot collaboration and assistance applications. One way to introduce compliance is to use serial elastic actuators (SEA). This yields two kinematically decoupled dynamic systems, the RA‐PKM mechanism and the actuation system, that are force‐coupled by (passive) elastic elements. The DOF of the actuation system exceeds the DOF of the RA‐PKM according to the degree of actuation redundancy. Due to the kinematic decoupling the RA‐PKM is underactuated. To address this issue, a flatness‐based feedback‐linearizing position control approach along with a stiffness modulation approach is proposed.
Hybrid modeling of viscoelastic and switching–induced heating in ferroelectrics
Authors: Warkentin Andreas , Ricoeur Andreas 
Published: March 2023

AbstractThis contribution focuses on two effects causing a temperature change in electrically loaded ferroelectrics. These materials are often subjected to cyclic loading, where viscoelasticity prevails at lower electric fields, whereas dissipative heating by domain switching dominates above the coercive field. While viscoelasticity is modeled within a phenomenological, rheological framework, the ferroelectric constitutive behaviour is described based on a microphysical model. Merging both approaches results in the hybrid model presented in this paper.
Optimization of the dimensional stability of paper‐based sandwich panels during the pressing process using design of experiments
Authors: Wei Yuting , Hirsch Franz , Süße Dietmar , Lutsch Birgit , Kästner Markus 
Published: March 2023

AbstractIn this contribution, the causes leading to the undesired unevenness on the exterior surface of a paper‐based sandwich structure during the manufacturing process are investigated. This provides insight into the manufacturing parameters that need to be adjusted to reduce this waviness. A finite element model of the pressing process is developed in the commercial software ABAQUS and then used to analyze the formation of the surface unevenness. The sandwich structure adopted in the model consists of a decorative layer, an intermediate layer, a corrugated core and a bottom layer. In particular, the core has a sinusoidal structure with various geometry parameters, which are adjusted in the model to investigate the effect on the waviness of the top surface. The results of the quasi‐static process simulation correlate well with the experimental results. A subsequent parameter study based on the design of experiments (DoE) shows the relationship between the material parameters of the intermediate/bottom layer and the resulting waviness.
Analysis of a phase‐field finite element implementation for precipitation
Authors: Safi Ali Reza , Chafle Rupesh , Klusemann Benjamin 
Published: March 2023

AbstractPrecipitation hardening is an essential mechanism in materials design of age‐hardenable aluminium alloys. The occurrence and distribution of nano‐sized particles in such alloys can lead to superior material properties. During thermo‐mechanical processing, these particles evolve dynamically as function of temperature and applied load. Therefore, sophisticated modelling frameworks are required to study the underlying phenomena of this microstructural evolution in depth. Phase‐field method based on the diffuse interface approach has been successfully employed in literature to study particle nucleation and growth, as well as equilibrium particle shapes. Although phase‐field models provide reliable results due to the flexible adaption of the free energy, the method is computationally expensive, requiring efficient solution schemes. The finite‐element discretization in deal.II can overcome scalability disadvantages and can outperform standard finite‐difference codes. In this work, we used adaptive mesh refinement and adaptive time‐stepping and investigate how AMR and the use of the same stiffness matrix for a certain amount of time steps affect the performance of the phase‐field model. Particle growth simulations are performed to outline the major benefits of the finite element phase‐field model. The numerical strategy is shown to be effective regardless of the initial particle shape by considering different particle morphologies. The results illustrate a significant increase in simulation performance with the applied numerical techniques.
On the numerical homogenization of real polycrystalline microstructures
Authors: Scheunemann Lisa , Schröder Jörg 
Published: March 2023

AbstractThe 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, which are constructed based on morphological information of the real microstructure and lead to a reduction of computational cost, see [2]. In their construction, a least‐square functional is used to minimize the deviation of statistical properties, such as volume fraction, spectral density and lineal‐path function, of the SSRVE and the real microstructure. The application of SSRVEs has been shown to lead to an adequate representation of the mechanical behavior of the real microstructure. The first part of the talk will give an overview on the construction of SSRVEs and present examples of multiscale analyses using the FE2 approach with simplified microstructures in different engineering applications of steel material.The paper also focusses on the details of the microstructure and discusses crystal plasticity models, see e.g. [3], in order to account for the material anisotropy induced by the texture of the crystalline structure of steel. It is well known that for rate independent single crystal plasticity, the ambiguity of the choice of active slip systems and linear dependency of slip criteria may cause instabilities in the algorithm. Classical perturbation methods are often used to solve the problem as well as rate dependent algorithms which model the rate independent case as the limit of vanishing viscosity. However, this leads to stiff constitutive equations and thus requires small time increments. In [4], an alternative approach has been proposed recently which is based on handling the constrained optimization problem in the framework of infeasible primal‐dual interior point methods (IPDIPM). We modify the original constrained optimization problem using slack variables in order to stabilize the algorithm and allow for temporary violation of the constraints. Numerical examples are presented for crystalline structures with face centered cubic properties.
Incorporation of thermal effects into the energy‐momentum consistent elastic model for fiber‐bending stiffness in composites
Authors: Dietzsch Julian , Kalaimani Iniyan , Gross Michael 
Published: March 2023

AbstractOwing to the wide acceptance of fiber reinforced composites in the lightweight structure industry, the need to study its thermo‐elastic behavior in dynamical multi‐body systems still remains an open question. Standard continuum models, by virtue of first‐order gradient of deformation, cannot capture curvature effects and hence appropriate extensions of the standard modeling techniques are indispensable to model the accurate physical stiffness. The fiber‐bending curvature are captured by introducing a higher‐order gradient of the deformation as an independent field in the standard continuum. This work explores in detail, a further extension of this continuum to understand the thermal effects on the bending stiffness of fiber bundle in fiber‐reinforced composites. Our proposed model incorporates the temperature of the composite and its bidirectional dependency with the higher‐order gradients of the deformation into the extended mechanical continuum model. The implementation of the model is pursued in the context of multi‐field mixed finite element method and dynamic variational principle. The principle of virtual power enables our extended non‐isothermal continuum to derive an energy‐momentum scheme of higher order. The resulting time‐integrator exhibits physically consistent locking‐ free numerical behavior in dynamical simulations. Our novel approach is illustrated by simple transient dynamic simulations with a hyperelastic, transversely isotropic, polyconvex material behavior. We investigate the conservation of total energy and total momentum in the framework of thermo‐elasticity and study the spatial and temporal convergence for long‐term dynamic simulations with coarser grids and increased accurate numerical solutions.
Wetting of rough surfaces in a phase field model
Authors: Wolf Jana , Flieger Yannic , Diewald Felix , Langenbach Kai , Stephan Simon , Hasse Hans , Müller Ralf 
Published: March 2023

AbstractSurface wetting can be simulated using a phase field approach which describes the continuous liquid‐gas transition with the help of an order parameter. In this publication, wetting of non‐planar surfaces is investigated based on a phase field model by Diewald et al. [1, 2]. Different scenarios of droplets on rough surfaces are simulated. The static equilibrium for those scenarios is calculated using an Allen‐Cahn evolution equation. The influence of the surface morphology on the resulting contact angle is investigated while the width of the phase transition from liquid to gas is varied as a model parameter.
Investigation of turbulent mixing using a stochastic hierarchical parcel swapping mixing model
Authors: Starick Tommy , Schmidt Heiko 
Published: March 2023

AbstractTurbulent mixing plays an important role in a variety of applications ranging from astrophysics to combustion and even pollutant dispersion. The Direct Numerical Simulation (DNS) that resolves all scales is not feasible for most engineering applications since the flow has a wide range of length and time scales, which yields extremely high resolution requirements. Large Eddy Simulations (LES) overcome this limitation by modeling the sub‐grid scale effects. In transported Probability Density Function (PDF) methods, the key challenge is to develop an accurate mixing model. At this point, the Hierarchical Parcel‐Swapping (HiPS) model, introduced by A.R. Kerstein [J. Stat. Phys. 153, 142‐161 (2013)], is an attractive candidate. It is characterized by a computationally efficient representation of the effects of turbulence on a time‐evolving structure of diffusive scalar fields. The interpretation of the diffusive scalar fields or a state space as a binary tree structure is an alternative approach compared to the most common mixing models. The characteristic feature of HiPS is that every level of the tree corresponds to a specific length and time scale, which is based on turbulence inertial range scaling. The state variables only reside at the base of the tree and are understood as fluid parcels. The effects of turbulent advection are represented by stochastic swaps of sub‐trees at rates determined by prevailing turbulent time scales associated with the sub‐trees. The mixing of adjacent fluid parcels is done either instantaneously or at rates consistent with the corresponding diffusion time scales. In this work, HiPS is detailed for the simulation of passive scalar mixing first. Preliminary results for the scalar power spectra, mean square displacement and scalar dissipation rate are shown and reveal a reasonable agreement with experimental findings. Furthermore, the integrated binary tree structure allows to satisfy a large number of criteria for a good mixing model. Considering the reduced order and computational efficiency, HiPS is an attractive candidate for modeling the mixing in transported PDF methods.
Influence of Tyre Characteristics on Periodic Motions for an Understeering Vehicle
Authors: Steindl Alois , Edelmann Johannes , Plöchl Manfred 
Published: March 2023

AbstractWe investigate the dynamics of a two‐wheel vehicle model after deviating from an unstable steady powerslide motion. For a model with brush tyre characteristics we observed that for a range of constant driver inputs (front steering angle, driving torque) the motion converges to a periodic oscillation around a circular path with a very small radius of curvature. In this paper we investigate, how a modified tyre model with decreasing friction coefficient for large slip velocities influences the stability and domain of existence for these periodic motions. We also compare the obtained solutions with those using Pacejka's Magic Formula for the tyre characteristics and find a remarkable good agreement.
Modeling the anisotropic elasto‐plastic material behavior of paper and paperboard at finite deformations
Authors: Kopic-Osmanovic Nadir , Prume Erik , Felder Sebastian , Kloppenburg Greta , Simon Jaan-Willem 
Published: March 2023

AbstractAccurately modeling the material behavior of paper and paperboard is proven to be highly demanding. Most difficulties arise from the pronounced anisotropic nature of the material. Additionally, differences in the in‐plane and out‐of‐plane behavior as well as non‐isochoric plasticity, which affects the elastic behavior, further deepen the issue at hand. Therefore, an material model is proposed, capable of capturing the anisotropic elasto‐plastic behavior of paper and paperboard. The constitutive framework was derived in a thermodynamically consistent manner, valid for finite deformations, and accounting for the coupling of in‐plane and out‐of‐plane behavior. The influence of the orthotropic anisotropy on the elasto‐plastic material response was introduced through the concept of structural tensors. A slight generalization of the elastic part of the free energy was made in order to incorporate the densification effect. A well known yield criterion was modified in order to account for some inconsistencies. Non‐isotropic hardening was considered by defining a set of coupled internal variables. The model's capabilities were demonstrated by simulating the process of folding and creasing.
Effect of the combination of diuretics, renin–angiotensin–aldosterone system inhibitors, and non‐steroidal anti‐inflammatory drugs or metamizole (triple whammy) on hospitalisation due to acute kidney injury: A nested case–control study
Authors: Calvo Dulce Maria , Saiz Luis Carlos , Leache Leire , Celaya Maria Concepción , Gutiérrez‐Valencia Marta , Alonso Alvaro , Erviti Juan , Alzueta Natalia , Echeverría Amaya , Garjón Javier , Fontela Carmen , Sanz Lorea , Acín Maria Teresa , Fernández Maria Loreto , Gómez Nerea 
Published: March 2023

AbstractPurposeConcomitant use of diuretics, renin–angiotensin–aldosterone system (RAAS) inhibitors, and non‐steroidal anti‐inflammatory drugs (NSAIDs) or metamizole, known as ‘triple whammy’ (TW), has been associated with an increased risk of acute kidney injury (AKI). Nevertheless, there is still uncertainty on its impact in hospitalisation and mortality. The aim of the study was to analyse the association between exposure to TW and the risk of hospitalisation for AKI, all‐cause mortality and the need for renal replacement therapy (RRT).MethodsA case–control study nested in a cohort of adults exposed to at least one diuretic or RAAS inhibitor between 2009 and 2018 was carried out within the Pharmacoepidemiological Research Database for Public Health Systems (BIFAP). Patients hospitalised for AKI between 2010 and 2018 (cases) were matched with up to 10 patients of the same age, sex and region of Spain who had not been hospitalised for AKI as of the date of hospitalisation for AKI of the matching case (controls). The association between TW exposure versus non‐exposure to TW and outcome variables was analysed using logistic regression models.ResultsA total of 480 537 participants (44 756 cases and 435 781 controls) were included (mean age: 79 years). The risk of hospitalisation for AKI was significantly higher amongst those exposed to TW [adjusted odds ratio (aOR) 1.36, 95% confidence interval (95%CI) 1.32–1.40], being higher with current (aOR 1.60, 95%CI 1.52–1.69) and prolonged exposure (aOR 1.65, 95%CI 1.55–1.75). No significant association was found with the need of RRT. Unexpectedly, mortality was lower in those exposed to TW (aOR 0.81, 95%CI 0.71–0.93), which may be influenced by other causes.ConclusionVigilance should be increased when diuretics, RAAS inhibitors, and NSAIDs or metamizole are used concomitantly, especially in patients at risk such as elderly patients.
Social media multitasking and college students' academic performance: A situation–organism–behavior–consequence perspective
Authors: Zhao Lei 
Published: March 2023

AbstractA growing number of researchers have begun to highlight the potential negative effects of the excessive use of social media on college students. In particular, college students engage in social media multitasking, in which they perform multiple tasks simultaneously. Such action could adversely influence their academic performance. Hence, on the basis of the situation–organism–behavior–consequence paradigm, we developed a research model to explore the etiology of social media multitasking and its impact on college students' academic performance. Using partial least squares–structural equation modeling techniques to analyze the survey data of 523 Chinese college students, we found that the fear of missing out (the situation) is positively associated with social media multitasking (the organism), which in turn is positively related to cognitive distraction (the behavior) and ultimately leads to a decline in academic performance (the consequence). Our study deepens the understanding of the phenomenon of social media multitasking among college students and can provide a reference for educators to implement intervention measures.