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94th Annual Meeting of the International Association of applied Mathematics and mechanics, GAMM 2024

作者： Schuttert, Wouter J. Abdul Rasheed, Mohammed Iqbal Rosić, Bojana Applied Mechanics and Data Analysis Faculty of Engineering Technology University of Twente Enschede Netherlands

Induction welding utilizes electromagnetic induction to heat carbon fiber reinforced thermoplastic (CFRTP) materials, enabling their fusion without direct contact. This heating process directly impacts material viscosity and bonding strength, with optimal temperatures ensuring proper fusion and strong adhesion between composite layers. The process is strongly influenced by material quality,as poor-quality materials can lead to uneven heating, incomplete fusion, and compromised structural integrity. To investigate the influence of the variation of CFRTP material properties on the generated heat, in this paper, we proposea novel way of modeling and propagating the stochastic electrical conductivity tensor through the physics based model describing the fusion bonding. The electrical conductivity of CFRTP is an anisotropic and inherently variable material property. To model this variation, we propose a stochastic model belonging to a family of positive definite tensors. In particular, we suggest the stochastic modelin which both the scaling/strength and orientation of the tensor are separately modeled as stochastic. In this manner, we are capable of assigning a specific class of spatial symmetries and invariances to individual realizations of the stochastic tensor, all the while insisting that the average of the entire population adheres to a potentially ‘higher’ spatial invariance class. Finally, the proposed model is incorporated to the physics based model based on which the variation in the temperature field characterizing the fusion bonding process is quantified with the help of the sparse grid integration. © 2024 The Author(s).

关键词： Electric conductivity

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Decentralized feedback damping with distributed control applied to ducts and anechoic chambers 31

Decentralized feedback damping with distributed control appl...

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31st International Conference on Noise and Vibration Engineering, ISMA 2024 and 10th International Conference on Uncertainty in Structural Dynamics, USD 2024

作者： Berkhoff, A.P. University of Twente Faculty of Engineering Technology Department Applied Mechanics and Data Analysis Drienerlolaan 5 Enschede7522NB Netherlands

ISBN: (纸本)9789082893175

This paper considers techniques to improve stability robustness and performance robustness of controllers in ducts and anechoic chambers. Aspects that are considered are the stability of transfer functions that are obtained from system identification, the size of the quiet zone, and reduction of controller complexity by limiting the number of control parameters. The methods that are considered in this paper are decentralized acoustic feedback to dampen resonances, directional sensors for a larger and predictable region of silence, current drive with velocity feedback, and distributed control. For loudspeakers a feedback structure is proposed which consists of two nested feedback loops. The methods are numerically evaluated for controlling reflections to realize anechoic properties in a duct and a full-size anechoic chamber. © 2024 Proceedings of ISMA 2024 - International Conference on Noise and Vibration Engineering and USD 2024 - International Conference on Uncertainty in Structural Dynamics. All rights reserved.

关键词： Decentralized control

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Surrogate modelling for finite element simulations Towards a stochastic surrogate approach

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VDI Berichte 2022年第2407期2022卷 555-562页

作者： van de Weg, B.P. Greve, L. Rosic, B. Volkswagen AG Wolfsburg Germany Applied Mechanics and Data Analysis Faculty of Engineering Technology University of Twente Enschede Netherlands

To reduce required used knowledge and simultaneously improve generalization in finite element surrogate modelling, a stochastic weight assembly is introduced to the well-known traditional long short-term memory (LSTM) neural network. Due to the propagation of uncertainties and simultaneous sparsity favouring weight optimization, it is shown using a structural application that an auto-adaptive recurrent LSTM neural network is created which automatically adapts its architectural complexity to the problem provided, hereby improving LSTMs generalization capabilities. © 2022 the authors.

关键词： Long short-term memory

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AUTOMATIC KINEMATIC ALIGNMENT OF FLEXURES IN PARALLEL MECHANISMS

AUTOMATIC KINEMATIC ALIGNMENT OF FLEXURES IN PARALLEL MECHAN...

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ASME 2024 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC-CIE 2024

作者： Piening, Patrick V.L. Nijenhuis, Marijn Aarts, Ronald G.K.M. Brouwer, Dannis M. Precision Engineering Faculty of Engineering Technology University of Twente Enschede Netherlands Applied Mechanics & Data Analysis Faculty of Engineering Technology University of Twente Enschede Netherlands

ISBN: (纸本)9780791888414

Compliant mechanisms offer a number of benefits over sliding joint based mechanisms;however, their design is more complicated. As a result multiple design methods have been developed to assist with the design of compliant mechanisms. The kinematic FACT method assists in the manual design of mechanisms but has seen limited use in computational optimization. This research presents an alternative kinematics based computational optimization approach towards the automatic placement of a chosen set of flexures in 3D space such that a desired constraint space is obtained while minimizing the redundancy of constraints within a parallel spatial mechanism. A continuous measure for vector space misalignment is developed and utilized in a cost function optimization to manipulate the coordinate frame transformation of screws associated with flexural building blocks. This continuous measure is also used to formulate constraints for the cost function optimization. The approach is tested in three design cases within a limited design volume: a spherical hinge composed of wire flexures, a single rotation degree of freedom (DOF) hinge composed of leaf flexures and a parallel mechanism with three non-intersecting rotational DOFs consisting of wire flexures. The flexures are introduced and optimized sequentially and kinematically valid designs are obtained. This research is a stepping stone towards the development of a more general automatic 3D building block based synthesis approach for compliant mechanisms. Copyright © 2024 by ASME.

关键词： Cost functions

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CHARACTERIZING REFLECTANCE PATTERNS OF UD CF/PAEK COMPOSITES FOR LASER ASSISTED FIBRE PLACEMENT 23

CHARACTERIZING REFLECTANCE PATTERNS OF UD CF/PAEK COMPOSITES...

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23rd International Conference on Composite Materials, ICCM 2023

作者： Asijee, Tom J. Grouve, Wouter J.B. Krämer, Erik T.M. Rasheed, Mohammed Iqbal Abdul ThermoPlastic composites Research Center Palatijn 15 Enschede Netherlands Production Technology University of Twente De Horst 2 Enschede Netherlands Applied Mechanics & Data Analysis University of Twente De Horst 2 Enschede Netherlands

In-situ consolidation during laser assisted fibre placement (LAFP) has the potential to provide a fast and cost-effective manufacturing solution, that can be used for manufacturing large scale aerospace components. The processing temperature plays a vital role in obtaining consistent consolidation quality and interlaminar bond strength when manufacturing parts with in-situ consolidation. The heat flux distribution may be influenced by the reflection patterns of a composite surface, and therefore accurate descriptions of these patterns are important to obtain a good prediction of the thermal response during processing. The present study proposes a fast methodology to characterize the reflective patterns of a composite surface subjected to near-infrared laser light under a shallow incidence angle, using a technique based on high dynamic range imaging. It is observed that, in line with other studies, the reflection pattern of a CF/LM-PAEK composite tape changes considerably with fibre orientation. Moreover, the radiance maps of the reflected patterns showed a 15% decrease in the light received on the screen for a composite under 45° fibre orientation in comparison to same light shone on a sample with 0° fibre orientation. © 2023 International Committee on Composite Materials. All rights reserved.

关键词： Optical properties

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Stochastic Modelling of Elasticity Tensors

arXiv

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arXiv 2024年

作者： Shivanand, Sharana Kumar Rosić, Bojana Matthies, Hermann G. Scientific Computing Center Karlsruhe Institute of Technology Germany Applied Mechanics and Data Analysis University of Twente Netherlands Institute of Scientific Computing Technische Universität Braunschweig Germany

We present a novel framework for the probabilistic modelling of random fourth order material tensor fields, with a focus on tensors that are physically symmetric and positive definite (SPD), of which the elasticity tensor is a prime example. Given the critical role that spatial symmetries and invariances play in determining material behaviour, it is essential to incorporate these aspects into the probabilistic description and modelling of material properties. In particular, we focus on spatial point symmetries or invariances under rotations, a classical subject in elasticity. Following this, we formulate a stochastic modelling framework using a Lie algebra representation via a memoryless transformation that respects the requirements of positive definiteness and invariance. With this, it is shown how to generate a random ensemble of elasticity tensors that allows an independent control of strength, eigenstrain, and orientation. The procedure also accommodates the requirement to prescribe specific spatial symmetries and invariances for each member of the whole ensemble, while ensuring that the mean or expected value of the ensemble conforms to a potentially ‘higher’ class of spatial invariance. Furthermore, it is important to highlight that the set of SPD tensors forms a differentiable manifold, which geometrically corresponds to an open cone within the ambient space of symmetric tensors. Thus, we explore the mathematical structure of the underlying sample space of such tensors, and introduce a new distance measure or metric, called the ‘elasticity metric’, between the tensors. © 2024, CC BY.

关键词： Tensors

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Correction to: Third-order geometric stiffness formulation for improved mesh convergence of thin and wide spatial beams in the generalized strain beam formulation (Computational mechanics, (2024), 10.1007/s00466-024-02570-5)

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Computational mechanics 2025年第4期75卷 1449-1449页

作者： Nijenhuis, M. Meijaard, J.P. Naves, M. Aarts, R.G.K.M. Precision Engineering Faculty of Engineering Technology University of Twente Enschede Netherlands Applied Mechanics & Data Analysis Faculty of Engineering Technology University of Twente Enschede Netherlands Industrial Automation & Robotics University of Applied Sciences Windesheim Zwolle Netherlands

The original version of the article has a error in the equation 70 (Derivative was missing). The corrected equation is given below: (Formula presented.) The uncorrected equation is given below: (Formula presented.) Th...

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A compliant and redundantly actuated 2-DOF 3RRR PKM: Less is more 10th

A compliant and redundantly actuated 2-DOF 3RRR PKM: Less is...

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10th ECCOMAS Multibody Conference 2021

作者： Berendsen, Dustin Sridhar, Aditya Aarts, Ronald Faculty of Engineering Technology Applied Mechanics & Data Analysis University of Twente P.O. Box 217 Enschede7500 AE Netherlands

ISBN: (纸本)9789634218708

The development of a compliant (or flexure-based) manipulator with redundant actuation has been considered before, showing that the redundancy can be exploited to increase the support stiffness and reduce actuator loads. In this previous design the manipulator’s workspace has been defined to encompass all kinematically accessible end effector positions. In this paper we reconsider the design philosophy. It appears that limiting the workspace ("less") ultimately results in a better performance in a larger area ("more") as before. The dynamic performance of the manipulator is evaluated with a flexible multibody model. The links are assumed to be rigid. The SPACAR software is used as its flexible beam element can describe the non-linear behaviour of the flexure joints well at rather large deflections. This numerically efficient model is well-suited for design optimisation which aims at the largest workspace area while assuring a minimal parasitic natural frequency and limiting the local stresses throughout the full workspace. Furthermore, the simulations show that preloading of the flexures results in smaller required actuator torques. An optimised design has been build. A control system has been synthesised that handles the actuator redundancy by minimising the 2-norm of the driving torques. It is demonstrated that the setup’s behaviour is similar to the model and that in particular the preloading significantly lowers the required actuator torques. © 2021, Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics. All rights reserved.

关键词： Actuators

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data-driven identification of latent port-Hamiltonian systems

arXiv

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arXiv 2024年

作者： Rettberg, Johannes Kneifl, Jonas Herb, Julius Buchfink, Patrick Fehr, Jörg Haasdonk, Bernard Institute of Engineering and Computational Mechanics University of Stuttgart Pfaffenwaldring 9 Stuttgart70569 Germany Institute of Applied Mechanics – Data Analytics in Engineering University of Stuttgart Universitätsstr. 32 Stuttgart70569 Germany Department of Applied Mathematics University of Twente P.O. Box 217 Enschede7500 AE Netherlands Institute of Applied Analysis and Numerical Simulation University of Stuttgart Pfaffenwaldring 57 Stuttgart70569 Germany

Conventional physics-based modeling techniques involve high effort, e.g., time and expert knowledge, while data-driven methods often lack interpretability, structure, and sometimes reliability. To mitigate this, we present a data-driven system identification framework that derives models in the port-Hamiltonian (pH) formulation. This formulation is suitable for multi-physical systems while guaranteeing the useful system theoretical properties of passivity and stability. Our framework combines linear and nonlinear reduction with structured, physics-motivated system identification. In this process, high-dimensional state data obtained from possibly nonlinear systems serves as input for an autoencoder, which then performs two tasks: (i) nonlinearly transforming and (ii) reducing this data onto a low-dimensional latent space. In this space, a linear pH system, that satisfies the pH properties per construction, is parameterized by the weights of a neural network. The mathematical requirements are met by defining the pH matrices through Cholesky factorizations. The neural networks that define the coordinate transformation and the pH system are identified in a joint optimization process to match the dynamics observed in the data while defining a linear pH system in the latent space. The learned, low-dimensional pH system can describe even nonlinear systems and is rapidly computable due to its small size. The method is exemplified by a parametric mass-spring-damper and a nonlinear pendulum example, as well as the high-dimensional model of a disc brake with linear thermoelastic *** Codes 93B30, 37E99 Copyright © 2024, The Authors. All rights reserved.

关键词： Hamiltonians

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Mathematical analysis of Dynamic High Power Laser Beam Shaping Using Galvanometer Scanners or Deformable Mirrors

SSRN

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SSRN 2023年

作者： Bremer, Scholte J.L. Aarts, Ronald G.K.M. Römer, Gert-Willem R.B.E. Department of Mechanics of Solids Surfaces & Systems Faculty of Engineering Technology University of Twente Drienerlolaan 5 Enschede7522NB Netherlands Chair of Applied Mechanics and Data Analysis Department of Mechanics of Solids Surfaces & Systems Faculty of Engineering Technology University of Twente Drienerlolaan 5 Enschede7522NB Netherlands

In high power laser material processing technologies, such as laser welding, laser cladding or laser surface treatment, tailoring the spatial intensity profile of the laser beam, popularly known as beam shaping, is used to optimise the processing results in terms of processing quality and/or production rate. To allow for dynamic beam shaping — i.e. tailoring the intensity profile during processing — dynamic optics in the optical setup are required. Current dynamic optical devices suitable to shape a single high power laser beam are Galvanometer Scanners and Deformable Mirrors. However, an objective comparison of the beam shaping capabilities, such as resolution and shaping performance, of these beam shaping devices is lacking. This work proposes a novel mathematical framework to analyse and compare the two beam shaping concepts. This framework is used to quantify beam shaping capabilities as function of relevant laser setup parameters. Next, using the mathematical framework, the performance of the Galvanometer Scanner and Deformable Mirror is simulated when targeting a splitted laser beam, creating a horseshoe shaped intensity profile and creating a square uniform profile. Results show that, in practice, both devices will be able to create these three desired laser intensity profiles in the focal plane, with similar small average errors when compared to the desired beam shape. However, the error distributions show differences which are characteristic for the physical limitations of each individual beam shaping device. © 2023, The Authors. All rights reserved.

关键词： Laser materials processing

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