bluuebunny/crossref_metadata_2025_split huggingface dataset:
Constitutive modelling of the deformation‐induced martensite transformation observed in metastable austenitic CrNi steels
Authors: Thammineni Hari Kisan , Zhu Tong , Smaga Marek , Beck Tilmann , Müller Ralf 
Published: December 2021

AbstractMetastable austenitic CrNi steels undergo phase transformation when loaded or deformed plastically. In the current work a macroscopic and phenomenological constitutive model is presented to model the strain induced transformation of austenite to martensite. The approach is based on the previous works of Olsen and Cohen [1] & Stringfellow et al. [2]. The kinetics of the phase transformation is modelled based on the assumption that the intersections of the shear bands in the austenitic phase, act as potential martensite nucleation locations. Evolution of the shear band density and their intersections are modelled using the plastic strain in the austenitic phase. The probability of the intersection creating martensite is given by a Gaussian cumulative distribution, which in turn depends on the temperature and stress triaxiality. The resulting stress‐ strain behavior considers the volume fraction, plastic strains and the strain hardening parameters of the individual phases as internal variables. An explicit formulation of the material model is implemented as a user subroutine in a bi‐linear element formulation of FEM. Some of the required material parameters are estimated by fitting experimental stress‐strain and martensite volume evolution curves. For the purpose of illustrating the model's behavior, boundary value problems of components with structured surfaces are presented.
On the incorporation of curvature effects into the isogeometric analysis of fibre‐reinforced solids
Authors: Witt Carina , Kaiser Tobias , Menzel Andreas 
Published: December 2021

AbstractIn the context of engineering on the micro‐ and nanoscale, size‐dependency is an important characteristic of material behaviour. In order to avoid complex experiments and predict size effects in simulations instead, classic continuum approaches are extended by the introduction of a length scale, e.g. through the consideration of gradient contributions. For the particular case of fibre‐reinforced materials, such a gradient‐enhanced approach can be achieved by introducing the fibre curvature as an additional kinematic quantity. This implies that basis functions with a global continuity higher than C0 are required for a finite element‐based approach which accounts for these fibre curvature effects. The present contribution shows that the isogeometric finite element method can provide a framework for the simulation of the respective higher‐gradient continua.
Surrogate Modeling of a Nonlinear, Biphasic Model of Articular Cartilage with Artificial Neural Networks
Authors: Egli Franziska S. , Straube Richard C. , Mielke André , Ricken Tim 
Published: December 2021

AbstractThe increasing number of cartilage diseases negatively affects the quality of life for a large part of the population. Understanding the mechanical properties of cartilage is a key component in investigating and mitigating the effects of such diseases. To describe the behavior of articular cartilage, a biphasic fiber‐reinforced numerical model based on the Theory of Porous Media (TPM) has been developed. To possibly provide an alternative for the corresponding time‐consuming computational simulations, the suitability of Artificial Neural Networks (ANNs) as surrogate models is investigated. For this purpose, the simulation results of a compression‐relaxation test are compared with the predictions of the ANN.
A multi‐level data‐driven finite element method in polymorphic uncertainty quantification
Authors: Korzeniowski Tim Fabian , Weinberg Kerstin 
Published: December 2021

AbstractThis contribution explores the ability to conduct polymorphic uncertainty computations within the data‐driven finite element framework. The constitutive equation is replaced by data sets that determine the material behavior, and a fuzzy load is used for the polymorphic approach. To conduct many simulations with the discretized variables and to increase numerical efficiency, the numerical cost is reduced by a multi‐level method.
A strain gradient enhanced model for the phase‐field approach to fracture
Authors: Makvandi Resam , Abali Bilen Emek , Eisenträger Sascha , Juhre Daniel 
Published: December 2021

AbstractPhase‐field modelling has been shown to be a powerful tool for simulating fracture processes and predicting the crack path under complex loading conditions. Note that the total energy of fracture in the classical phase‐field formulations includes the strain energy density from the linear elasticity theory resulting in singular stresses at the crack tip. Recently, we have demonstrated that integrating the strain gradient elasticity into the conventional phase‐field fracture formulations may improve the final results by alleviating the effects of a singular stress field around the crack tip [1]. The current contribution focuses on a more general formulation of strain gradient elasticity.
Integral effects of the Debye layer on a sedimenting particle with zeta‐potential variations
Authors: Marthaler Philipp G. , Class Andreas G. 
Published: December 2021

AbstractFluid‐solid interfaces give rise to electro‐hydrodynamic effects at microscale. In a macroscale model, those effects can be represented by jump conditions. This report focuses on the derivation of such jump conditions for integral parameters, like mass flux, forces and charge fluxes. In particular, the effect of spatial and temporal variations in the ζ‐potential on the solid's surface are discussed, using the generic problem of a sedimenting particle.
Remarks on a primal‐dual interior point algorithm for single crystal plasticity
Authors: Scheunemann Lisa , Nigro Paulo S. B. , Schröder Jörg 
Published: December 2021

AbstractIn 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 case relying on an infeasible primal‐dual interior point method, which has been presented in [5]. It is able to bypass several issues known in rate independent algorithms. Besides a brief overview of the continuum mechanical and algorithmic framework, aspects on different formulations related to the Karush‐Kuhn‐Tucker (KKT) conditions are discussed.
Energy related thermomechanical material model validation in complex tensile testing with self heating
Authors: Sparr Holger , Roszak Robert , Sagradov Ilja , Schob Daniela , Ziegenhorn Matthias 
Published: December 2021

AbstractThe objective of this work is the application of viscoplastic material models in a consistent thermomechanical framework to make use of infrared thermography as one source of a phenomenological model validation. The thermomechanical foundation led to the understanding, that each mechanical deformation can be analysed as a thermodynamical process. The usual balance equations applied in a mechanical process are completed by the first and second law of thermodynamics. In this setup, the classical stress‐strain characteristics is accompanied by the temperature evolution and the evolution of derived quantities such as the energy resp. energy‐rate transformation ratio (ETR). These three characteristics combined can improve the assessing procedure of the investigated deformation load path qualitatively as well as quantitatively. The initial boundary value problem of the coupled displacement and temperature fields is experimentally well supported by a high‐resolution infrared camera. A reduced thermal boundary value control simplifies the experimental measures to be realised. It is shown in the analysis, that the attained surface temperature accuracy is well‐suited for the identification of model parameters related to dissipative deformation phenomena. The common split into different fractions of free energy allows a detailed evaluation in terms of hardening related stored energy and other derived state entities. The potential of the instantaneous rate of energy storage is with respect to the comparability of different modelling approaches explained and is illustrated by experimental results. As a further consequence, a more complex tensile testing regime is proposed to validate the applied material model for metals.
Model‐free Data‐Driven simulation of inelastic materials using structured data sets, tangent space information and transition rules ‐ convergence test
Authors: Ciftci Kerem , Hackl Klaus 
Published: December 2021

AbstractData‐driven computational mechanics replaces phenomenological constitutive functions by performing numerical simulations based on data sets of representative samples in stress‐strain space. The distance of modeling values, e.g. stresses and strains in integration points of a finite element calculation, from the data set is minimized with respect to an appropriate metric, subject to equilibrium and compatibility constraints, see [1,2]. Although this method operates well for elasticity problems it challenges dealing with history‐dependent materials. One approach by [3], is the inclusion of local histories into the data set. However, it is still necessary to include models for the evolution of specific internal variables. In the presented approach, the data set is augmented with directions in the tangent space of points in stress‐strain space. Moreover, the data set is divided into subsets corresponding to different material behavior, e.g. elastic and inelastic. Based on the classification, transition rules map the modeling points to the various subsets. The convergence will be demonstrated by applying it to a model of elasto‐plasticity with isotropic hardening.
Analysis‐Suitable T‐Splines of arbitrary degree and dimension
Authors: Morgenstern Philipp , Görmer Robin 
Published: December 2021

AbstractThis paper defines analysis‐suitable T‐splines for arbitrary degree (including even and mixed degrees) and arbitrary dimension. We generalize the concept of anchor elements known from the two‐dimensional setting, extend two existing concepts of analysis‐suitability and justify their sufficiency for linear independence of the T‐spline basis.
Using Deep Learning to Enhance Compton Camera Based Prompt Gamma Image Reconstruction Data for Proton Radiotherapy
Authors: Barajas Carlos A. , Kroiz Gerson C. , Gobbert Matthias K. , Polf Jerimy C. 
Published: December 2021

AbstractProton beam radiotherapy is a cancer treatment method that uses proton beams to irradiate cancerous tissue while simultaneously sparing doses to healthy tissue. In order to optimize radiational doses to the tumor and ensure that healthy tissue is spared, many researchers have suggested verifying the treatment delivery through real‐time imaging. One promising method of real‐time imaging is through a Compton camera, which can image prompt gamma rays emitted along the beam's path through the patient. However, the images reconstructed with modern reconstruction algorithms are often noisy and unusable for verifying proton treatment delivery due to limitations with the camera. This paper demonstrates the ability of deep learning for removing false prompt gamma couplings and correcting the improperly ordered gamma interactions within the data for the case of Triples and Doubles‐to‐Triple events.
Structural topology optimization of 3D‐printable microlattices for lightweight materials
Authors: Krischok Andreas , Keip Marc-André 
Published: December 2021

AbstractWe present a micro‐macro approach for the structural optimization of graded microlattices that contain unit cells with a triply periodic structure. These individual unit cells are based on minimal surface problems such as the the Schwarz Primitive surface or the Gyroid and exhibit a porous structure that allows for a macroscopic grading of the material fraction of the cells. Both the macro‐scale and the micro‐scale are optimized by means of a Cahn‐Hilliard phase‐field model that is coupled with an elastic problem. The optimization on the macro‐scale is performed with the finite element method (FEM) while the micro‐scale optimization makes use of a spectral method that solves the periodic problem in a fast manner by means of fast Fourier transforms (FFT).
Neural Network Parameter Identification Based Constitutive Modeling of Superelastic Shape Memory Alloys
Authors: Kaup Andreas , Lenzen Niklas , Altay Okyay 
Published: December 2021

AbstractSuperelastic shape memory alloys (SMAs) are two‐phase polycrystal materials with hysteretic energy dissipation and deformation recovery capabilities. This feature opens numerous application possibilities, particularly using SMA wires in structural vibration control. However, vibrations, such as wind and earthquake induced, may occur in high rate regimes with alternating amplitudes. Experiments show that the thermodynamically coupled SMA behavior is highly sensitive to strain rate and amplitude. Accordingly, the prediction accuracy of the constitutive models depends notably on their thermodynamic parameters, such as latent heat, heat transfer coefficient and specific heat. The identification of these parameters requires extensive experiments. To circumvent this challenge, this study proposes for SMA wires a machine learning based parameter identification procedure using artificial neural networks (ANNs). In this approach, a recently improved uniaxial macroscopic constitutive SMA model is utilized as a forward physics based model to compute all possible responses in an expected parameter space. With the generated data, a multilayer ANN is trained as a data based inverse model. The Latin hypercube sampling and the backpropagation learning algorithms are applied. After training, the data based model is able to identify suitable thermodynamic parameters from SMA stress responses. With the identified parameters, the constitutive model replicates the strain rate and amplitude dependent SMA response effects. The experimental results are matched by the model with high accuracy.
Investigation of high temperature vulcanized and room temperature vulcanized silicone rubber based on flexible piezo‐electric energy harvesting applications with multi‐walled carbon nanotube reinforced composites
Authors: Manikkavel Amutheesan , Kumar Vineet , Kim Jaehoon , Lee Dong Joo , Park Sang Shin 
Published: December 2021

AbstractFlexible energy harvester can be able to produce continuous voltage output under the mechanical deformations. High temperature vulcanized (HTV) and room temperature vulcanized (RTV) silicone rubbers are used for making the flexible piezo‐electric energy harvester. A total of 1 and 2 phr of multi‐walled carbon nanotube (MWCNT) are used as the electrode material mixed with the rubber solution for the preparation of flexible electrode. Cyclic loading machine is used for the application of 2 Hz of bi‐axial load and uniaxial compression load in the specimen. One centimeter depth of displacement is applied during the bi‐axial cyclic loading and 4 mm amplitude of displacement is applied during the compression loading. Tensile and compression tests are performed to determine the engineering properties of the material. Tensile load withstanding value of the silicone rubber is increasing as increasing the MWCNT filler in the rubber. Tensile value of the pure HTV silicone rubber is 10.020 N and for 2 phr MWCNT reinforced rubber is 22.106 N. Compressive withstanding load of pure HTV rubber is 189.565 N and for 2 phr MWCNT reinforced rubber is 287.066 N. HTV silicone rubber is the highly stiffness material on compares with RTV rubber based on the tensile and the compressive value. Transmission electron microscopy, optical micrographs, and scanning electron microscope show the morphology of MWCNT and surface image of specimen. A total of 2 mm substrate based 2 phr MWCNT reinforced HTV flexible energy harvester undergo decrease in voltage during the cyclic loading due to breakage of electrode. A total of 2 phr MWCNT electrode‐based sample can be able to produce more output voltage than 1 phr MWCNT electrode‐based sample during bi‐axial and compression loading. More voltage is produced in the compression specimen than bi‐axial one.
Covalent crosslinks turn natural Eucommia ulmoides gum/polybutene‐1 composites into multiple shape memory materials
Authors: Wang Yan , Pei Xianqiang , Xia Lin , Xin Zhenxiang 
Published: December 2021

AbstractA series of shape memory natural Eucommia ulmoides gum (EUG)/polybutene‐1 (PB‐1) composites were developed based on polymer blending. It was revealed that covalent crosslinks turned typical “sea‐island” phase morphology in the EUG/PB‐1 blend into a chemical co‐continuous structure, which played a vital role in promoting mechanical performances and fulfilling multiple shape memory effect dominated by the two well‐separated crystalline and melting phase transitions. Although the increase in cross‐linking density was a disadvantage to mechanical performances and shape fixing, the composite with more covalent crosslinks displayed better shape recovery capacity. The EUG/PB‐1 composite crosslinked by 0.4 phr diycumyl peroxide (DCP) displayed the highest shape fixing capacity, while the best shape recovery ability was given by that crosslinked by 1.6 phr DCP. The findings would provide a new technique to develop intelligent materials applied in smart packaging and hot‐shrinkable products.
Accuracy of identifying diagnosis of moderate to severe chronic kidney disease in administrative claims data
Authors: Paik Julie M. , Patorno Elisabetta , Zhuo Min , Bessette Lily G. , York Cassandra , Gautam Nileesa , Kim Dae Hyun , Kim Seoyoung C. 
Published: December 2021

AbstractBackgroundPrior validation studies of claims‐based definitions of chronic kidney disease (CKD) using ICD‐9 codes reported overall low sensitivity, high specificity, and variable but reasonable PPV. No studies to date have evaluated the accuracy of ICD‐10 codes to identify a US patient population with CKD.MethodsWe assessed the accuracy of claims‐based algorithms to identify adults with CKD Stages 3–5 compared with laboratory values in a subset (~40%) of a US commercial insurance claims database (Optum's de‐identified Clinformatics® Data Mart Database). We calculated the positive predictive value (PPV) of one or two ICD‐9 (2012–2014) or ICD‐10 (2016–2018) codes for CKD compared with a lab‐based estimated glomerular filtration rate (eGFR) occurring within prespecified windows (±90 days, ±180 days, ±365 days) of the ICD‐based CKD code(s).ResultsThe study population ranged between 104 774 and 161 305 patients (ICD‐9 cohorts) and between 285 520 and 373 220 patients (ICD‐10 cohorts). The mean age was 74.4 years (ICD‐9) and 75.6 years (ICD‐10) and the median eGFR was 48 ml/min/1.73 m2. The algorithm of two CKD codes compared with a lab value ±90 days of the first code achieved the highest PPV (PPV 86.36% [ICD‐9] and 86.07% [ICD‐10]). Overall, ICD‐10 based codes had comparable PPVs to ICD‐9 based codes and all ICD‐10 based algorithms had PPVs >80%. The algorithm of one CKD code compared with laboratory value ±180 days maintained the PPV above 80% but still retained a large number of patients (PPV 80.32% [ICD‐9] and 81.56% [ICD‐10]).ConclusionAn ICD‐10‐based definition of CKD identified with sufficient accuracy a patient population with CKD Stages 3–5. Our findings suggest that claims databases could be used for future real‐world research studies in patients with CKD Stages 3–5.
Biases associated with epidermal necrolysis reporting in pharmacovigilance: An exploratory analysis using World Health Organization VigiBase
Authors: Bettuzzi Thomas , Ingen‐Housz‐Oro Saskia , Maison Patrick , de Prost Nicolas , Wolkenstein Pierre , Lebrun‐Vignes Bénédicte , Sbidian Emilie 
Published: December 2021

AbstractBackgroundPossible biases in pharmacovigilance reporting may impact epidermal necrolysis (EN) and drugs associations.ObjectivesTo assess biases associated with EN‐reporting.MethodsUsing VigiBase, the World Health Organization‐pharmacovigilance database, among drugs associated with EN between 2016 and 2020, we used an unsupervised clustering including reports characteristics, that is, reporter quality, time from drug intake to EN onset, and only one suspected drug in the report.ResultsAmong 152 drugs, three clusters were identified. Cluster 1 (n = 41) exhibited drugs frequently reported within a time from intake to onset longer than 4 days, in 57 ± 13% of reports. It corresponded to well‐reported drugs and was composed mainly of antivirals and antiepileptics. Cluster 2 (n = 42) exhibited drugs frequently reported within a time from drug intake to onset shorter than 4 days, in 31 ± 12% of reports. It corresponded to drugs with a high risk of protopathic bias and was composed of nonsteroidal anti‐inflammatory drugs (NSAIDs), analgesics, and antibiotics. Cluster 3 (n = 69) exhibited drugs frequently reported with an unavailable time from drug intake to reaction, in 66 ± 11% of reports, and reported by a high frequency of consumers (9 ± 9%). It corresponded to drugs reported with a high risk of classification bias, and was composed of anticancer therapies and cardiovascular drugs.ConclusionProtopathic and classification biases impact EN‐reporting and should be considered regarding associations with antibiotics, NSAIDs, analgesics, anticancer therapies, and cardiovascular drugs.
Does acute flaccid myelitis cause respiratory failure in children?
Authors: Lazzarini Laura M. , Werner Julie M. , Perez Iris A. , Seruya Mitchel , Ramos‐Platt Leigh , Tiongson Emmanuelle , Keens Thomas G. 
Published: December 2021

AbstractIntroductionAcute flaccid myelitis (AFM) is a rare disease that affects spinal cord gray matter, results in acute flaccid weakness of one or more limbs and predominantly involves the cervical spinal cord, which places patients at higher risk for respiratory failure. Our study aims to describe respiratory failure in pediatric AFM patients with emphasis on the need for assisted ventilation and respiratory nerve involvement from an acute and long‐term perspective.Materials and MethodsWe reviewed the medical records of patients diagnosed with AFM seen in a multidisciplinary clinic for persistent limb weakness between 2016 and 2020.ResultsWe studied 54 patients, 35% were female. The median age of patients at illness onset was 5 years (range 7 months−19 years). The median age of patients at the time of study was 8.5 years (range 2−20 years). Eleven patients (20%) required assisted ventilation for acute respiratory failure. Of those that experienced acute respiratory failure, 81% developed chronic respiratory failure. Fifty‐six percent of patients with chronic respiratory failure were able to wean off assisted ventilation by 1 year. All patients that experienced unilateral diaphragm impairment with AFM onset experienced acute and chronic respiratory failure.DiscussionMany patients with AFM may experience respiratory compromise and develop chronic respiratory failure. However, most of these patients can be weaned off ventilatory support by 1 year from illness onset. Most children with unilateral diaphragm impairment can sustain adequate ventilation without the need for long‐term ventilatory support.