Scholarly Publications - Mechanical Engineering

Permanent URI for this collectionhttps://hdl.handle.net/11693/115626

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Open Access
An adaptive human pilot model with reaction time delay for enhanced adaptive control in piloted systems
(John Wiley & Sons Ltd., 2026-01-23) Habboush, Abdullah; Yıldız, Yıldıray
Adaptive controllers have proven successful in handling uncertain dynamical systems. Yet, their integration into piloted applications remains uncommon owing to their nonlinear characteristics, which give rise to unfavorable interactions between adaptive controllers and human pilots in certain applications. To enable their safe implementation in the loop with human pilots, we introduce an adaptive human pilot model suited for predicting human interactions with adaptive controllers. This model accounts for the time delay in the pilot's response when operating on an adaptive control system, thereby facilitating the evaluation of adaptive controllers in simulation environments and guiding their design to ensure smooth pilot-controller interactions.
Open Access
Multiscale analysis and texture design for hydrodynamically lubricated interfaces with variable viscosity and density liquids
(Elsevier Ltd., 2025-12-01) Koç, Sarp Ilgaz; Temizer, İlker; Biancofiore, Luca
In this work, a numerical framework is developed for the analysis and design of textured interfaces with piezoviscous, compressible and shear-thinning lubricants. This framework is based on a modified viscosity approach alongside homogenization as a mathematical technique for the upscaled solution of the Reynolds equation to alleviate the inherent computational difficulties to model roughness. Good agreement is observed between (i) direct numerical simulations, (ii) nonlinear Reynolds equation results and (iii) homogenized Reynolds equation results. Furthermore, the developed numerical framework has been used in conjunction with a topology optimization algorithm to design different surface textures that are dependent on the fluid rheology. These textures are shown to (i) minimize energy dissipation, or (ii) increase the traction to amplify the grip between the surfaces depending on the respective lubrication application.
Open Access
CPHS–XR: a unifying framework for understanding cyber physical human systems in the realm of extended reality
(Springer Science and Business Media Deutschland GmbH, 2026-01-02) Eraslan, Emre; Yıldız, Yıldıray; Annaswamy, Anuradha; Cecil J.; Gupta, Avinash; Chen, J.Y.C.; Fragomeni, G.; Fang, X.
As digital, physical, and human systems continue to converge, the vocabulary used to describe these integrations has become increasingly fragmented. Terms such as Human Computer Interaction, Human Machine Interaction, Cyber Physical Systems, Human Extended Reality Interaction, and Cyber Physical Human Systems (CPHS) describe varying system configurations in which humans, technologies, and environments interact to achieve shared goals. However, the proliferation and overlapping use of these terms have introduced conceptual ambiguity, complicating system comparison, evaluation, and design. This paper introduces the CPHS–XR framework as an enhanced and structured extension of CPHS. While grounded in the foundational tripartite structure, which comprises cyber, physical, and human components, CPHS–XR adds conceptual clarity by introducing technology enablers as cross-cutting elements that empower system components without altering their core integration. These enablers, such as extended reality, artificial intelligence (AI), Internet of Things, and perceptual technologies, give rise to diverse system behaviors, resulting in variations like immersive, adaptive, predictive, or actuated CPHS. Building on this foundation, the paper proposes a taxonomy based on three dimensions: immersion level, decision-making level, and granularity assignment. This taxonomy provides a systematic method for classifying CPHS variations as empowered configurations rather than as disconnected or standalone system types. By simplifying terminological complexity and contextualizing system evolution, the framework supports system classification, design, and analysis across domains. It also lays a foundation for future research in human-centered AI, immersive interfaces, and adaptive systems by ensuring that emerging technologies enhance rather than fragment the integration between human operators and cyber-physical systems.
Open Access
Nonlocal integral-type elasticity: Foundations of continuum-kinematics-inspired peridynamics (CPD)
(Springer Science and Business Media B.V., 2025-10-27) Steinmann, Paul; McBride, Andrew; Javili, Ali
This chapter explores the theoretical foundations and formulation of Continuum-Kinematics-Inspired Peridynamics (CPD), a recent paradigm in strongly nonlocal (integral-type) elasticity. CPD modifies and extends classical peridynamics by incorporating the pertinent kinematic measures of continuum mechanics, enabling, for example, accurate modelling of the Poisson ratio, among other attractive features. The governing equations of CPD are achieved via a variationally consistent procedure at large deformations. CPD offers a robust framework to capture the nonlocal behaviour of materials. Due to its inherent integral format, CPD naturally accommodates discontinuities and is therefore as well suited to describe fracture. Admissible stored energy densities of CPD are outlined whereby in the limit of infinitesimal affine deformations their relationship to classical linear elasticity is established.
Embargo
A nonlinear correspondence model for three-dimensional continuum-kinematics-inspired peridynamics
(Elsevier Ltd, 2025-11-12) Javili, Ali; Ekiz, E.; Steinmann, P.
Peridynamics (PD) is a nonlocal continuum mechanics theory that inherently allows for singularities and fracture. However, the classical PD theory restricts the Poisson ratio. This issue is rectified in continuum-kinematics-inspired peridynamics (CPD) that has been recently proposed. Because of its variational consistency and geometrically exact nature, CPD does not suffer from zero-energy modes, and thus, it furnishes an ideal nonlocal elasticity framework for large deformations. In a three-dimensional setting, CPD builds upon one-, two-, and three-neighbor interactions. One-neighbor interactions capture length-associated elasticity between pairs of points, equivalent to the original PD formalism. The two-neighbor interactions of CPD recover area-associated elasticity between triplet of points. The three-neighbor interactions of CPD recover volume-associated elasticity between quadruplet of points. This contribution provides for the first time a nonlinear correspondence material model for CPD in a three-dimensional setting such that it recovers a well-established compressible neo-Hookean energy density of nonlinear elasticity at large deformations. At small deformations, the proposed model reduces to classical isotropic linear elasticity. The current manuscript is the three-dimensional extension of the recent two-dimensional contribution of the authors.
Open Access
The role of viscoelastic stress in an abruptly converging/diverging channel under the thin film approximation
(Elsevier BV, 2025-08-07) Mehmet, Hakan Sarı; Ahmed, Humayun; Putignano, C.; Carbone G.; Biancofiore, Luca
We analyze a viscoelastic fluid, modeled by the Oldroyd-B constitutive equation, flowing in a sliding abruptly converging/diverging channel. We have chosen this geometry since it has connections to the typical elastohydrodynamic lubricated (EHL), for which recently (Sarı et al., 2024) have illustrated how a viscoelastic lubricant has a positive effect on the tribological performance by raising load and decreasing friction coefficient. We assume that the channel is thin and the magnitude of the “jump” is small enough allowing to take advantage of the thin film approximation. We observe that the step location is a critical factor for generating viscoelastic pressure due to the positive and constant increase in the volumetric flow rate. Presence of viscoelasticity quantified by the ratio between fluid relaxation time and residence time, called Deborah number. A high Deborah number leads to a significant increment in pressure if the step is close to the inlet, while, if it is close to an outlet, the pressure decreases compared to Newtonian flows. While in most of the work, the pressure at the boundaries (inlet and outlet) is set to zero, we also tested more realistic boundary conditions in which the pressure is equal to the average elastic stress, showing that the two kinds of boundary conditions have a similar qualitative behavior. Lastly, a texture geometry, composed by one converging followed by one diverging steps, is inspected to mimic an EHL profile. We find what is the optimal distance between the steps to maximize the load. The role of the elastic stress in this texture profile is finally discussed.
Open Access
Detection of microplastic waste by using a novel microfluidic system with an integrated object tracking algorithm
(Institute of Electrical and Electronics Engineers Inc., 2025-08-19) Khalak, Bushra Begum; Durmaz, Doruk; Külekçioğlu, Okan; Bahşi, Ela; Kasap, Selin; Onkal Engin, Güleda; Sarıtaş, Emine Ülkü; Erdem, Emine Yegan
Over the last couple of decades, microplastics, MPs, have become a large focus for pollution evaluation and sustainability. Water has become increasingly concentrated with MPs due to waste disposal and degradation over time. This project's goal is to detect and distinguish microplastics from other materials using a novelty microfluidic design. Analysis was done using multiple novel microchannel designs and Polydimethylsiloxane, PDMS, microchips. An object tracking algorithm, OT, was used to observe MPs and record flow through the microchannel. Footage tested on the microchips with the OT found that the varying pixel area shows the deformation of a microplastic under the chosen parameters.
Open Access
Comparison of integral equation formulations for Stokesian particulate flow simulations
(Sakarya University, 2025-02-28) Kabacaoğlu, Gökberk
Particulate Stokesian flows describe the hydrodynamics of rigid or deformable particles within Stokes flows, where viscous forces dominate over inertial effects. These flows are characterized by highly nonlinear fluid-structure interactions, moving interfaces, and multiple spatial and temporal scales, making numerical simulations both complex and computationally expensive. Accurately capturing these interactions requires sophisticated numerical approaches. The boundary integral equation method (BIEM) is a powerful tool for modeling such flows, as it reduces computational complexity by limiting the discretization to the immersed particle boundaries rather than the entire flow domain. This efficiency makes BIEM particularly suitable for studying systems with many particles or complex boundary geometries. In this work, we explore two fundamental BIEM formulations for Stokesian flows involving rigid particles: the first-kind and second-kind integral equations. These formulations differ in their mathematical structure and computational properties, impacting their stability, accuracy, and overall performance. By comparing these two approaches, we aim to highlight their respective advantages and limitations, providing insights into their applicability to different particulate flow scenarios. This analysis contributes to the broader understanding of numerical methods for Stokesian flows, addressing challenges inherent to fluid-structure interactions and advancing computational techniques in this field.
Open Access
A fault-tolerant model predictive controller with reconfiguration for optimal lateral stability in over-actuated electric vehicles
(IEEE, 2024-07-15) Koysuren, Kemal; Çakmakçı, Melih
This paper presents a fault-tolerant reconfigurable model predictive control method to improve the longitudinal and lateral reference tracking of four-wheel-steering and four-wheel-drive vehicles under concurrent steering actuator faults and fault modes. The proposed method detects, isolates, and then estimates the magnitude of individual faults. Fault magnitude information is then forwarded to the model-predictive controller, which configures its state-space input matrix and constraints based on the information provided to overcome the adverse effects of these faults that may manifest as both actuator loss of effectiveness and jam. It is shown that the integration of the fault estimation and the reconfiguration procedure does not affect the stability of the control system. The performance of the proposed method is first verified using obstacle avoidance maneuvering in a control-oriented, simpler vehicle model. An experiment with a scaled test vehicle is also conducted to prove the real-time applicability of the proposed control algorithm. Our analysis with two representative scenarios shows that the proposed reconfigurable fault-tolerant MPC algorithm can improve the system's performance by a minimum of 30% (and as much as 86%) compared to the conventional and adaptive model predictive controllers designed for vehicle stability.
Open Access
Dynamic behavior of helical gear pairs: model and experiments available
(The American Society of Mechanical Engineers, 2026-01-14) Ahi, T.; Kahraman, A.; Dönmez, Ata
While helical gears are critical components of many power transmission systems, their dynamic behavior has not been studied extensively, perhaps due to their complex vibratory motions and lack of experimental data to guide sound modeling efforts. This study proposes a general dynamic model of a helical gear pair supported by realistic shaft-bearing structures. Aiming at the examination of main assumptions regarding the modeling of helical gears, two versions of the model are constructed, a nonlinear time-varying (NTV) version with gear backlash and time variation of gear mesh stiffness included, and a linear time-invariant (LTI) version, both subject to nonproportional damping. An extensive experimental study is performed covering a large portion of the helical gear design space. Simulations of these experiments indicate that the LTI version of the model with both backlash and mesh stiffness variations ignored compares well with the experiments. The model predictions and measurements collectively show that a helical gear pair acts as a linear system with the loaded motion transmission error as its main excitation. They also indicate that the helical gear motions are three-dimensional, requiring an accurate description of the support structures in the model.
Open Access
Human-like learning in car following: an attention-based driving strategy with memory-inspired adaptation
(Elsevier, 2025-10-29) Al Habboush, Şeymanur; Yıldız, Yıldıray; Annaswamy, Anuradha M.
Traffic simulators are essential for testing autonomous driving algorithms, and they require driver models that accurately emulate human behavior to reflect real traffic conditions. Our study focuses on developing human driver models to be used in these simulators. We address the limitations of fixed driver models, which do not adapt to new information, by introducing an attention-based learning mechanism inspired by human memory. This mechanism is integrated into a multi-type car following model we developed. Unlike existing car following models, our approach allows the ego driver's decisions to be influenced, without any bias, by both the vehicle in front and the vehicle behind them. We demonstrate the predictive capabilities of the proposed model using real traffic data and provide a comprehensive statistical analysis of the model parameter distributions. This analysis shows how the model captures general behavioral tendencies across different data sets, enhancing the understanding of interactions between human drivers and providing more realistic simulations for testing purposes. Finally, we offer a step-by-step guide for implementing the model in the development of high-fidelity traffic simulators.
Open Access
Assessment of anticancer effects of Aloe vera on 3D liver tumor spheroids in a microfluidic platform
(John Wiley and Sons Inc, 2025-06-20) Tevlek, Atakan; Kibar, Güneş; Çetin, Barbaros
The search for effective anticancer therapies has increasingly focused on natural compounds like Aloe vera, renowned for its therapeutic properties. This study investigates the anticancer properties of Aloe vera on 3D liver tumor spheroids via a PDMS-based microfluidic device, providing a more physiologically realistic model compared to traditional 2D cultures. HepG2 cells were cultivated to generate 3D spheroids on-chip, thereafter subjected to different concentrations of Aloe vera and the chemotherapeutic drug Doxorubicin to evaluate cytotoxic effects. The microfluidic system, validated by COMSOL simulations, facilitated continuous perfusion and real-time assessment of cell viability over a duration of 10 days. The results indicated that Aloe vera markedly diminished cell viability by triggering apoptosis at concentrations over 12.5 mg/mL. IC50 values were determined at 72 h: 25 ± 0.10 mg/mL for Aloe vera and 5.47 ± 0.03 µg/mL for Doxorubicin in 2D cultures, but in 3D cultures, the IC50 values were 31.25 ± 0.14 mg/mL for Aloe vera and 8.33 ± 0.05 µg/mL for Doxorubicin. This study underscores the promise of Aloe vera as a natural anticancer agent and illustrates the efficacy of microfluidic platforms for enhanced drug screening and customized medicine applications.
Open Access
Development of a novel adaptive driver assistance based on real-time cornering parameter identification
(Elsevier, 2024-12-01) Keleş, Ahmet Faruk; Dağ, Doğa; Çakmakcı, Melih
In this paper, a novel adaptive driver assistance system was presented based on real-time cornering parameter identification using deep learning. Modern vehicle safety systems, like ESP (electronic stability program) and ADAS (advanced driving assistance systems), operate under specific conditions, requiring an adaptable system to perform as intended in all conditions. Our approach addresses this gap by continuously evaluating and adapting the vehicle's response to real-time traction conditions. We introduce a cornering coefficient identification method using deep learning for instantaneous parameter estimation and combine it with an advanced driver assistance system. This system adapts driver inputs to current road conditions while maintaining stability and desired vehicle dynamics. The paper details the mathematical modeling of a four-wheel-drive, four-wheel-steering vehicle, the development of the parameter identification method, and the implementation of the adaptive driver assistance system. Experimental results demonstrate the system's capability to enhance vehicle handling and safety across various driving conditions.
Open Access
A damage formulation for continuum-kinematics-inspired peridynamics to capture fracture experiments
(Elsevier, 2026-02-07) Laurien, Marie; Javili, Ali; Steinmann, Paul
Peridynamics (PD) is a nonlocal continuum formulation that naturally allows for discontinuities, such as cracks. It has therefore become attractive in the field of fracture modeling. Continuum-kinematics-inspired peridynamics (CPD) is a novel peridynamic reformulation that overcomes the fundamental limitation of classical bond-based PD, i.e. a fixed Poisson’s ratio. The novelty of this work is (i) the introduction of damage into the formulation of CPD and (ii) the comparison of the numerical results with fracture experiments conducted as a part of this study. In CPD, nonlocal interactions between material points are captured via one-, two- and three-neighbor interactions, allowing to measure length, area and volume changes. For each type of interaction, a separate damage variable is employed, depending on the associated strain. For a two-dimensional problem, the damage parameters of the model are derived from the classical fracture energy. In order to assess the model’s performance in predicting experimental outcomes, a series of fracture experiments is performed. Diagonally loaded square plates with center cracks of varying inclination angle are tested to study different fracture modes. The results demonstrate the model’s capability to capture the maximum loads and the crack paths observed in the experiments. This is the first contribution that integrates theory, computation and experiment within the framework of CPD.
Open Access
Maneuverable multilegged locomotion through anisotropically arranged soft backbones in a single-actuator modular miniature robot
(John Wiley and Sons Inc, 2026-01-06) Yaman, Yiğit; Arslan, Burak; Ergin, Ömer Çağrı; Aukes, D. M.; Özcan, Onur
Under-actuated compliant systems have emerged as a promising solution to the challenges of actuation and control in soft robotics. By leveraging structural compliance and material dynamics, such systems reduce the need for complex actuators and controllers. Herein, a centimeter-scale, eight-legged robot composed of four C-shaped modules connected via soft PDMS backbones is presented, powered by a single DC motor that induces vibration through a rotating unbalanced mass. This configuration enables four distinct locomotion modes: forward motion, turning, and lateral translations. The design simplifies fabrication and aligns with the Soft Curved Reconfigurable Anisotropic Mechanism paradigm. A modified pseudo-rigid body model is developed and integrated into the MuJoCo simulation environment to accurately capture the robot's dynamics. Experimental validation and sensitivity analysis are conducted to evaluate performance under varying conditions, and reinforcement learning is employed to optimize locomotion strategies. This work demonstrates a novel approach to versatile and scalable robotic motion using minimal actuation.
Open Access
Using plunging-type testing to investigate process mechanics at micro scale machining
(Elsevier BV, 2025-04-03) Adeeb, Syed Ahsan; Karpat, Yigit
In plunging-Type tests, a cutting tool is given a sinusoidal movement as the work material with a web on its surface is rotated at a constant speed. If the amplitude and feed rate of the cutting tool and rotational speed of the work material are correctly set, the plunging test can be completed within a full rotation. As a result, a detailed investigation of different episodes of micro-scale machining, such as rubbing, plowing, and shearing, can be conducted with a single test. Combined with force measurements and cut chip morphology, the process mechanics can be investigated in detail. This study conducted plunging tests on an ultra-precision CNC with a diamond cutting tool on commercially pure titanium alloy. The differences in tangential and normal forces observed during plunge-in and pull-out periods corresponding to the same amplitude were analyzed using an analytical model. Resultant forces during the pull-out phase are larger than those observed in the plunge-in phase, attributed to an increase in cut chip thickness. A computational model of the plunging-Type experiment has also been developed based on the findings of the analytical model. The proposed hybrid approach may be useful to improve identification of material constitutive model parameters based on micro scale machining experiments.
Open Access
Optical levitation of Janus particles within focused cylindrical vector beams
(Walter de Gruyter GmbH, 2025-04-28) Magazzù, Alessandro; Kasianiuk, Iryna; Kasyanyuk, Denis; Callegari, Agnese; Volpe, Giovanni; Maragò, Onofrio M.; Biancofiore, Luca
The confinement and manipulation of Janus particles have recently garnered significant interest due to their potential applications in fields such as nanotechnology and biophysics, where, under specific circumstances, they can act as microengines and drug carriers. However, the dynamics of Janus particles mostly rely on chemical reactions or thermal gradients, limiting their precision application. To tackle these limitations, we propose the 3D manipulation of Janus particles using focused cylindrical vector beams with a doughnut shaped intensity profile above the focal spot. In particular, we study the behaviour, orientation and manipulation of different highly reflective Janus particles composed of silica or polystyrene with a gold cap in the presence of optical potentials generated by focused cylindrical vector beams. Where the radiation pressure predominantly affects the gold cap rather than the bare particle body of the particle. We demonstrated the potential of the proposed levitation technique for controlling a wide range of Janus particles and real-life complex objects with high reflectivity.
Open Access
Human-inspired learning for car following models
(Elsevier BV, 2024) Al Habboush, Şeymanur; Yıldız, Yıldıray; Annaswamy, Anuradha M.
In this paper, we propose a human-inspired learning mechanism in the context of car following models. We use a memory structure to gather information from other drivers and make inferences about their driving styles. Then, this information is used to determine the ideal driving strategy. Subsequently, the learning process between the current and the ideal driving strategies is modeled with the help of adaptive control techniques. Finally, we incorporate the proposed learning mechanism into a multi-type car following model that we introduce. The performance of the proposed method is investigated using the NGSIM traffic data set.
Embargo
On a canonical interface model with application to micro-heterogeneous elastic solids
(Elsevier BV, 2025-03-22) Javili, Ali; Larsson, Fredrik; Runesson, Kenneth; Steinmann, Paul
Finite-thickness interphases between different constituents in heterogeneous materials are often replaced by a zero-thickness interface model. Due to increasing area-to-volume ratio with decreasing size of microstructures, interfaces introduce a physical length into the effective response at the macroscale. The most commonly studied interface models are the cohesive interface model and the elastic interface model. The cohesive interface model allows for a displacement jump across the interface, in contrast to the elastic interface model that requires displacement continuity across the interface. The classical general interface model assumes that the interface displacement itself must coincide with the displacement average across the interface. The recently proposed extended general interface model defines the interface displacement kinematically via the weighted average of displacement across the interface. Here, we propose a canonical interface model based on a variationally consistent approach, which encompasses all previous interface models. We implement our model with the finite element method and illustrate its consequences through a series of numerical examples. Moreover, variationally consistent homogenization is employed to upscale an elastic composite with particles surrounded by a canonical interface and embedded in a matrix. The numerical results highlight the significance of the canonical interface model on the overall response of composites, at times leading to counter-intuitive behavior at the macroscale.
Open Access
A geometrically nonlinear correspondence model for continuum-kinematics-inspired peridynamics
(Springer International Publishing, 2025-03-19) Javili, Ali; Ekiz, Ekim; Steinmann, Paul
Peridynamics (PD) has proven to be a promising theory to describe the behavior of materials allowing for singularities and fracture. The classical PD theory restricts the Poisson ratio. To address this issue, Continuum-kinematics-inspired Peridynamics (CPD) has been proposed as a variationally consistent formulation that can capture the Poisson effect exactly. Due to its geometrically exact nature, CPD does not suffer from zero-energy modes and displacement oscillations, making it an ideal nonlocal elasticity framework for large deformations. In a two-dimensional setting, CPD builds upon one-neighbor and two-neighbor interactions. One-neighbor interactions capture length-associated elasticity between pairs of points, equivalent to the original PD formalism. The two-neighbor interactions of CPD recover area-associated elasticity between triplet of points. This contribution provides for the first time a correspondence material model for CPD in a two-dimensional setting such that it recovers a well-established compressible neo-Hookean energy density of nonlinear elasticity at large deformations. At small deformations, the proposed model reduces to classical isotropic linear elasticity. The theory is illustrated via a series of numerical examples. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.