Magnetic driven tentacles for bio-mimic motion

To improve the wide-frequency vibration control capability of semi-active vibration isolators, the bidirectional variable modulus performance of hard magnetic magnetorheological elastomers (H-MRE) is crucial. To further enhance the characteristics of H-MRE, various technical solutions have been implemented in recent years, including filling H-MRE with pre-magnetized hard magnetic particles and doping soft magnetic particles into H-MRE. However, existing studies have faced issues such as particle agglomeration and complex preparation processes. In response to the contradiction between the complexity of the H-MRE preparation process and performance improvement in existing research, this study improves MRE performance by optimizing the hard magnetic particles and their distribution in H-MRE. By replacing traditional hard magnetic particles with magnetocrystalline anisotropic NdFeB particles, which exhibit better magnetic properties such as remanent magnetization, coercivity and saturation magnetization. The study systematically investigates the mechanism by which particle distribution influences H-MRE performance. Experimental results show that while enhancing the amplitude of positive modulus changes, the reverse modulus change amplitude of H-MRE is increased to 23.3%. This study lays an important foundation for the application of H-MRE in vibration control fields.

Magnetic field-assisted manufacturing of groove-structured flexible actuators with enhanced performance

Inspired by ciliate microorganisms such as Paramecium, this study designs and optimizes a cilia-driven magnetic soft robot based on gradient magnetization. The robot is primarily composed of a non-magnetic body and magnetic ciliary legs embedded with hard magnetic particles, aiming to achieve efficient and controllable locomotion. Finite element simulation was employed to systematically analyze the influence of external magnetic field parameters and the connection method of the hinge-like structure on the robot's leg deformation and locomotion efficiency. Through experimental optimization of the driving magnetic field parameters, the optimal driving conditions were determined to be <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$7 \text{mT}, 20 \text{Hz}$</tex>, and a duty cycle of 0.6, under which the robot's locomotion speed increased by approximately 40%. Furthermore, trajectory planning experiments verified that the robot can achieve stable and controllable movement at the air-liquid interface under these optimized conditions, with a mean trajectory tracking error of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$429.8 \pm 289.2 \mu \mathrm{m}$</tex>. This demonstrates the effectiveness of the structural optimization and magnetic field control methods.

In the contemporary era, novel manufacturing technologies like additive manufacturing (AM) have revolutionized the different engineering sectors including biomedical, aerospace, electronics, etc. Four-dimensional (4D) printing aka AM of smart materials is gaining popularity among the scientific community, which has the excellent ability to make soft structures such as soft robots, actuators, and grippers. These soft structures are developed by applying various stimuli such as pH, temperature, magnetic field, and many combinations onto soft materials. Stimuli in 3D printing permit various shape-morphing behaviors such as bending, twisting, folding, swelling, rolling, shrinking, origami, or locomotion. A wide variety of soft magnetic structures can be fabricated through the incorporation of soft or hard magnetic particles into soft materials resulting in magneto-active soft materials (MASMs). With this integration, magneto-thermal coupling actuation allows diverse magneto-deformations, facilitating the development of personalized devices that are capable of enhanced deformation. In this review, guidelines are provided on the 3D printing for MASMs such as magneto-active polymers (MAPs), magneto-active composites, and magneto-active hydrogels (MAHs) on the booming development of various smart and flexible devices such as soft robots, wearable electronics, and biomimetic devices. Moreover, 3D-printed soft robotics have an outstanding capacity to adapt to complicated situations for many advanced actuating applications. Finally, some current challenges and emerging areas in this exciting technology have been proposed. Lastly, it is anticipated that technological advancements in developing smart and intelligent magneto-active structures will have a significant impact on the design of real-world applications.

A microstructure enhancement method for hard magnetic particle chains based on magnetic field oscillation sieve

Exploring the effect of exchange coupling in (SrFe9.8Al2La0.2O19)1-x/(Co0.7Zn0.3Fe2O4)x nanocomposites synthesised by sol–gel auto combustion method

A new approach of data recording during manufacturing is to store information directly on machine components. This way, the components may serve as their own information carrier throughout the whole manufacturing process, and later in the working cycle. Such a concept is called “gentelligent” (for genetically intelligent) and aims at allowing to inherit fabrication and application data to the product's next generation. This requires a new kind of machine parts, which are capable for collecting, preprocessing, and storing information (e.g. temperature and forces during use of the component) on their surface. For storing the required information, proven principles of the peripheral magnetic data recording including inductive writing and a magneto‐optical readout are applied. The storage medium used is a material developed recently: “magnetic magnesium”, i.e. magnesium filled with hard magnetic particles. To allow a magneto‐optical readout based on the Magneto‐optical Kerr Effect (MOKE), bulk material is covered with a soft magnetic layer, called a keeper layer. The keeper layer is supplied to generate a homogeneous magnetic and reflective surface which is not provided by pure “magnetic magnesium”. This paper describes the development of the recording system. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

A new approach on tracking components throughout the entire manufacturing processes is to apply magnetic recording technology to storing key production data on the component itself. The system investigated uses magnetic magnesium , i.e. a magnesium matrix filled with hard magnetic particles. For storing the data, a classic inductive write head, consisting of a soft magnetic ring core with a write gap in the flux path and a coil for creating the magnetic flux is chosen. For an application in a machine environment, readout has to be done at a distance. On approach of such non-contact readout, an advantage of the Magneto-Optical Kerr Effect (MOKE), which senses the direction of magnetization of a reflecting surface, is to be taken. As in the case of data storage, information is encoded in the magnetization pattern of data tracks.

We investigate the effects of B2O3 addition on structural and magnetic properties of hard magnetic BaFe12O19 particles. The conventional solid state reaction method is used as the synthesis route. Single phase BaFe12O19 could be synthesized with very small amounts of B2O3 addition and with calcination at low temperatures (850° C) in short times (1 h). B2O3 addition also improves the magnetic parameters significantly. Remanence magnetization and specific magnetization at 1.5 T increase by ∼40% in magnitude although no significant variations on coercivity is observed.

9 - Textile fabrics and ferrite-loaded composite materials for electromagnetic-shielding applications

Completion time is an important issue on construction projects with limited practical duration usually studied comparing to construction or implementation cost. In this research work, the fuzzy behaviour of cost and time for project activities has been investigated based on predicted completion time followed by developing a mathematical model for making a trade-off approach for project planning. The objective function is to minimise project cost which is defined in discrete and continuous domains considering limited implementation time. According to the constraints, a nonlinear model was developed, so a linearisation technique has been utilised to convert that to linear. In addition, an acceptable range of changes (tolerance) is considered for the project completion time to achieve better solutions followed by making a sensitivity analysis process on results of time-cost trading-off approach. Installing a weigh in motion (WIM) system in the central Iranian road of Isfahan-Naein has been selected as case study and the proposed model has been validated using experimental data. Results revealed that the proposed model, which has been converted to linear, is capable to perform a time-cost trading-off approach for projects of those that do not have exact time and cost for project activities.

Three-dimensional large-deformation model of hard-magnetic soft beams

Turbomachinery aerodynamic and aeroacoustic modelling is recognized to be one of the main areas of interest in the frame of industrial engineering, due to the large number of applications concerning the rotating fluid machines. Numerical modelling is today widely integrated in the design and development process of industrial components, as well as Computational Fluid Dynamics (CFD) is a tool well integrated into the industrial development and production life-cycles. This has been made because of two main factors: the increase in the performance of relatively cheap computing systems and the progress made by development of integrated CAE virtual environment even more oriented to design and optimization. Furthermore well established and validated CFD methodologies able to deal with the high complexity of geometries and multiphysics approaches are available and practicable within the industrial environment. Nevertheless since for many of applications such as aerodynamics, heat exchange, etc., CFD is largely used, there are still some areas where it represents a challenge, in particular for its industrial applicability. One of these areas is the Computational AeroAcoustics (CAA), whose interest is rapidly growing due to the increasing demand of quick and efficient numerical tools for the design-to-noise approach to airframe components. The major difficulty of CAA is that noise is a secondary effect of other physical phenomena, and noise prediction has to deal with highly complex topics such as turbulence modelling and transition to turbulence prediction. Moreover the sound pressure compared with the hydrodynamic pressure is several orders of magnitude smaller making its numerical prediction very difficult. The goal of the present work is to perform investigations on two rotating fluid machines: the vertical axis wind turbines (VAWT) and the high speed transonic cruise propellers. The investigations performed were focused on the aerodynamic and aeroacoustic theoretical and numerical modelling in order to achieve the numerical results that actually miss in the literature improving the know-how for two classes of problems which play a central role in the modern industry: the renewable energies and the advanced transportation systems. VAWT modelling was approached from a theoretical point of view, by the implementation of a modern unsteady aerodynamic model for non-stationary airfoil aerodynamic coefficients prediction (the Beddoes Leishman model) into a classical theory, the Double Streamtube Paraschivoiu model. The acoustic modelling of WT was approached on a general basis with the modelling of the airfoil self-generated problem. It was chosen as it is one of the most prominent noise sources for wind turbines and it represents a big challenge for CFD. The preliminary literature review pointed out how there are different airfoil self-generated noise typologies, according to the laminar/turbulent characteristics of the flow field, airfoil aerodynamic parameters and far-field flow conditions. Different CFD numerical approaches were used for the different noise generation mechanisms, including transient RANS/LES simulations with a particular focus for novel turbulence modelling methodologies, involving transitional models and Embedded LES. The acoustic pressure flow computations were performed with the Ffowcs Williams Hawkings (FW-H) acoustic analogy and pressure time signals post-processed with an in-house built acoustic tool. Deep explorations of acoustic signal noise processing, Fast Fourier Transformation techniques and noise signal corrections have been necessary in order to achieve good agreement between experimental and computational data. The reference test-case was the NACA 0012 airfoil, chosen for the wide amount of experimental data available in literature in a significant range of velocities and angles of attack. The problem of propeller aerodynamic and aeroacoustic modelling was approached with the CFD and CAA simulation of a subsonic propeller, the NACA 4-(3)(08)-03, chosen for the experimental results available in literature for the 2-bladed and 7-bladed configurations. This test-case allowed us to set up properly the numerical simulation, the CAD model and the computational grid requirements for such kind of geometries. In a second stage the attention was focused on the NASA SR2 and SR3 geometries, both in the 8-bladed configuration. Experimental data in transonic conditions for wind tunnel and flight test were available for these two geometries, and numerical simulations were performed for 5 different data sets, for asymptotic Mach numbers between 0.6 and 0.9 and rotational speeds between 6000 and 9000 rpm. Results of the simulations are compared with experiments, showing the ability of this approach to predict noise with a discrepancy within a few dB for the different simulated conditions and microphones locations. Particular attention is given to the set of corrections to be applied to acoustic experimental data in order to be consistently compared with free field CFD results. The CFD simulation strategy has been refined to perform complete aerodynamic and aeroacoustic calculations with highly competitive computational cost.

In this book, the global sequential scenario of bifurcation trees of periodic motions to chaos is presented through a 1-dimensional, time-delayed, nonlinear dynamical system. The sequential periodic motions in such a 1-dimensional time-delayed system is achieved semi-analytically, and the corresponding stability and bifurcations are determined by eigenvalue analysis. A global sequential order of bifurcation trees of periodic motions to chaos is given by $${G_{1\left( S \right)}} \triangleleft {G_{1\left( A \right)}} \triangleleft {G_{3\left( S \right)}} \triangleleft {G_{2\left( A \right)}} \cdots \triangleleft {G_{m\left( A \right)}} \triangleleft {G_{2m + 1\left( S \right)}} \triangleleft \cdots \left( {m = 1,2, \ldots } \right),$$ where Gm(A) represents a global bifurcation tree of an asymmetric period-m motion to chaos and G2m+1(S) is for a global bifurcation tree of a symmetric period-(2m + 1) motion to chaos. Each bifurcation tree of a specific periodic motion to chaos are presented in detail. The bifurcation tree appearance and vanishing are determined by the saddle-node bifurcation, and the cascaded period-doubled periodic solutions are determined by the period-doubling bifurcation. From finite Fourier series, harmonic amplitude and harmonic phases for periodic motions on the global bifurcation tree are obtained for frequency analysis. Numerical illustrations of periodic motions are given for complex periodic motions in global bifurcation trees. The rich dynamics of the 1-D, delayed, nonlinear dynamical system is presented. Such global sequential periodic motions to chaos also exist in nonlinear dynamical systems.

ABSTRACTMachine hammer peening is a surface treatment technique originally developed for smoothening tools and mold surfaces. Treated surfaces are locally cold-worked, which results in a hardness increase and the induction of compressive residual stresses. In the present work, the feasibility of using this technique as a tool for embedding tungsten carbide hard particles on engineering-relevant substrate materials is systematically investigated. Tungsten carbide particles of three different sizes were embedded onto selected substrates using machine hammer peening. The particle embedment quality of the engineered surfaces was evaluated and correlated to the substrates' mechanical properties. The resulting tribological performance was investigated under reciprocating sliding conditions and the dominant wear mechanisms were correlated with the diameter of the embedded particles. The results show that machine hammer peening is a suitable technique for embedding hard particles in substrates of various materials, which additionally results in an enhancement in wear resistance, thus opening up a wide range of potential applications in tribologically loaded surfaces.