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The control bandwidth of a flexure mechanism is typically limited by parasitic resonance frequencies with low structural damping. Such resonances can be suppressed by including active material in the mechanism, which is used to dissipate energy at specified frequencies. The active material is typically placed in areas with high strain, in order to obtain the highest possible coupling and therefore dissipation. However, due to the low ultimate strain of some common active materials, the included active material will limit the deflection of the mechanism. In this work we introduce a design method that improves the closed-loop performance of a low pivot shift cross hinge mechanism by including active material in the leaf springs, without sacrificing the achievable deflection of the mechanism. The coupling between the active material and a selected undesired parasitic frequency is maximised by placing the material in locations with high modal strain. At the same time, the piezoelectric patches are only included in regions where the strain due to the nominal deflection is limited, such that the maximum deflection of ± 15 degrees is maintained. Using the patches as sensors and actuators, positive position feedback control is applied. Using simulations, it is shown that a selected resonance peak can be decreased by 16.3 dB for the considered mechanism, enabling 88% higher bandwidth.

Many precision machines, such as wafer scanners, have an internal motion stage. These stages generate reaction forces that act directly on the machine frame. A common method to minimize the effect of these reaction forces is a balance mass. To eliminate the need for this balance mass, it is proposed to use an active vibration isolation system as a virtual balance mass. Such can be achieved by constructing a force that is based on the reference of the motion stage that cancels its correlated reaction force. This appends the primary objective of an active vibration isolation system, which is to reduce the sensitivity to direct and indirect disturbances. A self-tuning algorithm is implemented to deal with parameter uncertainty and variation. The performance of the proposed method is experimentally validated on a 6-DoF active vibration isolation system, which is appended with a flexure based, straight guided motion stage. A 300 Hz frame mode is introduced of which the displacement can be measured to assess the performance of the method. The proposed method improved the tracking accuracy of the motion stage by a factor of 3.8 and reduced the settling time of the frame mode by a factor of 91, compared to the system without a virtual balance mass.

Leafsprings are commonly used in flexure mechanisms to enable repeatable motion and provide support stiffness. In various applications, the torsional stiffness needs to be increased. This paper presents the concept of using warping constraints distributed along the leafspring to increase the torsional stiffness relative to the stiffness in other directions. A beam-based model of nonuniform torsion is used to estimate the relationship between the geometrical design parameters and the expected increase in torsional stiffness. The model predicts that an order of magnitude increase in stiffness is feasible. Compared to other solutions, the distributed warping constraints have a less obtrusive shape that offer more design freedom.

In the design process of high-precision motion stages, the dynamic behavior is of paramount importance. Manual design of such a stage is a time-consuming process, involving many iterations between engineers responsible for mechanics, dynamics and control. By using topology optimization in combination with additive manufacturing, post-processing using traditional machining and parts assembly, it is possible to arrive at an optimal design in an automated manner. The printing, machining, and assembly steps are incorporated in the optimization in order to directly arrive at a manufacturable design. With a motion stage demonstrator optimized for maximum eigenfrequencies, it is shown that combining additive manufacturing and topology optimization at industry-relevant design precision is within reach and can be applied to high-performance motion systems.

Six degree of freedom manipulation provides full control over position and orientation, essential for many applications. However, six degree of freedom closed kinematic (parallel) manipulators either have a limited range of motion combined with a good repeatability when comprising flexure joints, or they have limited repeatability with a large workspace when using traditional rolling- or sliding-element bearings. Employing recent developments in large stroke flexures and design optimization, a fully flexure-based large range of motion hexapod robot has been designed. The resulting system allows for ±100 mm of translational and more than ±10 degrees of rotational range of motion in each direction combined with a small mechanism volume below 0.25 m3. Furthermore, a dedicated flexure-based design for the actuators combines high actuation forces without impairing precision, allowing for accelerations exceeding 10g. Experiments on a preliminary prototype validate the large workspace and confirm a high repeatability below 0.1 µm can be achieved, which is currently limited by electronics.

High accelerations of fast moving robots induce high fluctuating reaction forces and moments, resulting in undesirable vibrations and loss of accuracy. These fluctuations can be reduced or even eliminated by dynamic balancing techniques, e.g. by addition of counter-masses. However, these techniques typically disregard the flexibility of the mechanism. This flexibility potentially leads to undesirable eigenfrequencies and unbalance of an otherwise perfectly balanced mechanism. In this paper, the effect of link flexibility on the force balance quality is investigated in the frequency domain. This is done for a 2-DOF parallel manipulator with realistic stiffnesses. With the use of flexible multi-body software, the frequency transfer functions for the shaking forces are obtained for an unbalanced, a force balanced and a partially balanced case. The results show that, firstly, force balance results in a strong attenuation of the shaking forces’ frequency content up to the first eigenfrequency. Secondly, the addition of balance mass results in a reduction of the first parasitic eigenfrequency of the system leading to a worsened performance around the first eigenfrequency and a reduction in controller bandwidth. Identification of these effects leads to an optimal, intermediate solution, which mitigates the negative effects of dynamic balance, resulting in low-frequency shaking force attenuation of 30 dB without loss of controller bandwidth.

Flexure mechanisms are commonly designed to be exactly constrained to favour determinism, though at the expense of limitations on parasitic eigenfrequencies and support stiffness. This paper presents the use of viscoelastic material for providing additional stiffness without the indeterminism commonly associated with overconstraining. It is demonstrated experimentally that a custom synthesised elastomer compound can compensate for unintended misalignments without internal stress buildup, while improving the dynamic performance in terms of the first parasitic eigenfrequency. The measurements are corroborated by a nonlinear flexible multibody analysis.

Iron core torque motors provide a high power density, but require high off-axis stiffness, which is normally too demanding for flexure mechanisms especially when considering large range of motion applications. In this paper, a flexure-based suspension for a high torque iron core direct drive torque motor with a large range of motion of 60 degrees is presented. This flexure-based suspension provides the required high radial stiffness (>1000N/mm) combined with a high radial load capacity (500N) over the full range of motion. Furthermore, the suspension maintains a constant position of the pivot axis within 0.1mm, which is required to limit pull-in forces and to stay within alignment tolerances of the actuator. A prototype has been designed and constructed and experimental validations confirm the high radial stiffness and load capacity of the rotor suspension.

Interventional X-ray systems are used to acquire 2D and 3D images of complex anatomical structures (e.g. the cardiovascular system). These images provide a clinician with feedback in a medical procedure, which enables advanced minimally invasive treatments. A typical interventional X-ray system contains an X-ray source and detector, connected by a C-shaped arm. Several stacked motion systems enable the C-arm and imaging equipment to move spherically around an isocentre. This allows for 2D X-ray images to be taken at various projection angles. Other imaging techniques such as 3D computed tomography are enabled by this core functionality. Developments in interventional X-ray systems are often a compromise between performance, clinical usability, and cost. This paper presents three novel mechatronic architectures, which are designed to break through this trade-off. The proposed designs aim to improve the interventional X-ray system on multiple, application-specific levels. The first system focusses on improved image quality and clinical usability of 3D scans (high-end applications). A dual stage design allows for significantly extended and faster scanning motions, with a 55% smaller footprint in the operating room. It is based on a quasi-kinematic roll guide design, resulting in less nonlinear behaviour, and improved alignment of the imaging equipment. The second system decreases cost and installation requirements, while maintaining and adding to the current imaging capability (low-end applications). By reconsidering the degrees of freedom needed, a lightweight design is created (>50% mass reduction), with an improved stiffness to mass ratio. Both system 1 and 2 present an evolutionary improvement on existing architectures. As a revolutionary alternative, the third system pursues high-end performance and optimised workflow, at reduced overall cost. It features a compact and lightweight (~500 kg) mechatronic design which makes optimal use of the space available in the operating room. A full scale mock-up of this system has been built. Currently, a detailed design, including hardware realisation is being made for experimental performance validation at subsystem level.

WOS: 000311653300001 In this study, the evaluation of therapeutic effects of probiotic bacteria, in comparison with single supportive and symptomatic therapy. in CPV (canine parvovirus) infection was aimed. A total of 20 naturally infected dogs, 1-6 months old, exhibiting enteritis and for which the diagnosis were confirmed by an ELISA commercially available test, were randomly divided into two equal groups. Only supportive and symptomatic therapy was applied in group I, whereas a commercial probiotic product which contained different probiotic bacteria (VSL#3) was used as adjuvant oral therapy in the group II. Clinical scores established from complete clinical examinations performed at the beginning and on every subsequent day during the therapy and haematological parameters determined before and 5 days after treatments were compared between the 2 groups. A moderate anaemia (low haemoglobinemia) coupled to reduction in the mean corpuscular volume and haemoglobin concentration was evidenced in 55% of parvovirus infected clogs and a relatively leukopenia when compared with after the treatment was observed in all diseased animals. Seven (70%) and nine (90%) dogs in the groups I and II respectively, survived during the trial. Moreover, the clinical scores have declined significantly more rapidly in the group II than in the group I. While the erythrocyte parameters have not significantly differed between the 2 groups, leukocyte and lymphocyte numerations were significantly improved during the treatment course only in clogs additionally treated with probiotics. The present study indicates that probiotics may be beneficial in CPV therapy. especially for shortening the recovery time, under optimal care conditions. Commission of Scientific Research Projects of Ondokuz Mayis UniversityOndokuz Mayis University [VET- 014] This study was supported by the Commission of Scientific Research Projects of Ondokuz Mayis University (Project No: VET- 014).

WOS: 000287897300001 In this study, the effects of florfenicol and tulathromycin on clinical recovery and acute-phase proteins in bovine respiratory diseases (BRD) were evaluated under the field conditions. A total of 30 local race feedlot cattle were used in the study. Twenty naturally infected beef and 10 healthy beef were used for the experimental and control groups, respectively. Sick animals were randomly divided into two groups of 10 and subcutaneously 40 mg per kg florfenicol was administrated in group I and 2.5 mg per kg tulathromycin was administrated in group II as single dose. The animals were clinically examined before (0 h) and 9 days after the treatment. Also, blood samples were taken and serum haptoglobin and serum amyloid A concentrations were measured before and 9 days after the treatment. It was concluded that although the clinical findings and recovery were not always correlated with serum acute phase proteins levels, florfenicol and tulathromycin can be effective for BRD therapy under field conditions.

PubMed: 20001994 The aim of this study was to describe and quantify the therapeutic value of honey in oral mucosal ulcers healing in comparison with Glyceroloxytriester (TGO). We also aimed to biochemically evaluate the healing effects of honey which had been collected from the Blacksea region flora on mucosal ulcers resulting in material loss. Thirty wistar rats (240±30 g) were enrolled in this study. Excisional wounds were performed in all rats for animal oral mucosal ulcer model. They were randomly allocated to three groups: group 1 was treated with Apitherapeutic agent or honey (0,1 ml, 2x1), group 2 was treated with TGO (0,1ml, 2×1) locally, Group 3 served as the control group. Following the surgical procedure on day 7, biopsy specimens were taken from right buccal mucosa and on day 14 biopsy specimens were taken from left bucal mucosa in all rats. Afterwards, hydroxy pyroline levels were measured. Data were analyzed statistically There was no statistically significant difference between Group 1 and 2, and also between Group 2 and 3, but there was statistically significant difference between Group 1 and 3 on day 7. There was no statistically significant difference between Group 1, 2 and 3 on day 14.

/0000-0002-0636-4214 WOS: 000268128600005 PubMed: 25903514 This randomized study was designed to establish the efficacy of platelet-rich plasma (PRP) gel and topical estradiol alone, or in combination, on healing of full-thickness wounds created on the trunk of rabbits. Fifteen New Zealand white female rabbits and 60 wounds were studied. Four 2.25-cm(2) full-thickness wounds were created using a template and treatments including a sterile saline solution that were assigned randomly to the wounds. Wounds were bandaged, dressed intermittently, and assessed by wound measurements and a collection, of samples at 7, 14, and 21 days to evaluate healing. Variables of interest were hydroxyproline concentration and scored gross and microscopic morphologic characteristics reflective of wound healing. PRP gel + estradiol-treated wounds completely healed faster than wounds given other treatments. Granulation tissue growth to the skin level was faster (P < 0.05) in the PRP gel + estradiol group than the other groups. Only the PRP gel + estradiol group had a significantly lower collagen level than the sterile saline solutions on day 7 (P < 0.05). The PRP gel + estradiol group and estradiol group led to an increase in angiogenesis on day 14 (P < 0.05). Complete epithelization was observed only in the PRP gel + estradiol group compared with the other groups on day 7. PRP gel + estradiol-treatment enhanced healing in full-thickness wounds by reducing the contraction rate with a trend toward accelerating both epithelial migration and the angiogenic response.

34th Congress of the Federation-of-European-Biochemical-Societies -- JUL 04-09, 2009 -- Prague, CZECH REPUBLIC WOS: 000267069900927 … Federat European Biochem Soc

Guvenc, Tolga/0000-0003-1468-3415 WOS: 000254907600039 Clinical signs and necropsy findings were described in a four-year-old female rhesus macaque with diabetes mellitus, resulting from spontaneous amyloidosis. Weakness, polyphagia, polydipsia, and polyuria, which lasted for a few weeks, were determined from anamnesis and clinical investigations. Highly increased serum BUN, AST, ALP levels, glycosuria, and proteinuria was detected in the biochemical analysis. According to these clinical, haematological, and biochemical data, it was thought that the monkey was affected with diabetes mellitus. Despite all efforts to cure the animal, the patient died. Diffuse amyloidosis was detected in the kidney and pancreas at the necropsy and histopathological examinations.

Additive manufacturing (AM) has recently gained popularity over the conventional manufacturing methods as it allows for innovative design solutions in terms of geometric complexity and shape optimization. As a result of the geometry, size and heterogeneous microstructure of the AM samples, conventional macroscale experiments are, however, frequently inadequate in determining the resulting material parameters. In such cases, nanoindentation represents a viable non- destructive technique for determining the mechanical properties such as Young’s modulus (EIT) and hardness (HIT) of small samples’ volumes. The nanoindentation measurements on a Keysight G200 machine equipped with a standard Berkovich tip are performed in this study on AISI 316L wrought samples as well as samples obtained via the laser-powder bed fusion (L-PBF) AM process. The standard depth-controlled loading- unloading method is used. With the aim of comparing the material properties on the macro- and microscale, conventional monotonic uniaxial tensile tests are also performed on both samples types. The possibility of calibrating the material parameters of finite element (FE) numerical models using nanoindentation test results to obtain the load vs. the indentation depth curve is finally discussed. Experimentally obtained load- displacement curves are used to calibrate the elastic and plastic material parameters of the FE model. Since FE modelling of the nanoindentation process is a nonlinear elasto-plastic contact problem, Young’s modulus and hardness alone are, in fact, not sufficient to characterize properly the overall material behaviour.

Losing hand functions due to ischemic or haemorrhaging stroke, often resulting in spasticity, causes difficulties in the activities of daily living (ADL), making rehabilitation challenging and important. Using robotic rehabilitation devices is a promising novel approach to exercise the hands, promote patient volition and increase the neural connections. The human hand, with its many degrees of freedom (DOFs), evolutionary formed for precision and power gripping, introduces, however, difficulties in developing specialized rehabilitation devices. Grasp-oriented modelling of hand’s kinematics with simplified but effective mathematical representations is, therefore, critical. The kinematic characterisation performed in this work simplifies the available 24 DOFs biomechanical model to 9 DOFs by constraining the joints via synergies specific to different grasp types and fingers’ inclination angles.The acquired model is compared to the anatomical one, and the effects of intra- and inter-dependent joints are studied. Although the used dependencies reduce slightly the joints’ ranges of motion (ROMs), the important grasping types and the ROMs used in ADL are preserved. The proposed model increases also positioning accuracy.

Autonomous sensor nodes, enabled by the integration of energy harvesting principles, create the preconditions for a significant simplification and mass reduction in aircraft structural health monitoring. A promising energy harvesting approach to collect and convert the energy from random aircraft vibrations during operation, is to use piezoelectric energy harvesters. Due to the narrow operating frequency bandwidth of the considered harvesters, a frequency up-conversion mechanism, based on plucking the free end of the piezoelectric devices by using rotating plectra, and letting the transducers oscillate at their eigenfrequencies, is introduced in order to enable their utilization while operating in the considered random excitation environment. An experimental investigation of fused deposition modelling 3D printed plectra is therefore carried on to better understand the effects of the respective design parameters, i.e., their size, stiffness and material types, on the resulting performances of the piezoelectric energy harvesters in terms of the obtainable specific power outputs. The voltages generated by the harvesters, as well as their maximal free end deflections, are thus measured for different plectrum materials, different plucking frequencies and different geometries of the plectra. Design-of-experiments (DoE) methods are employed in the setup of the experiments, whereas advanced numerical algorithms are used for the analysis of the hence obtained results. A comprehensive insight into the effects of plectrum properties on the responses of the piezoelectric energy harvesters is therefore provided, which represents another step towards the design of autonomous energy harvester powered sensor nodes to be used in aircraft structural health monitoring applications.

Frictional characteristics are an important factor in the design and exploitation of precision positioning systems and components. In fact, friction is a complex stochastic phenomenon depending on an intricate interplay between materials’ physical and chemical properties, as well as on the contact conditions influenced by the exerted normal forces, sliding velocities, contact area, temperature etc. Experimental measurements of the nanoscale friction force of an X39CrMo17-1 high-alloy steel thin film, deposited on a silicon wafer, are obtained in this work via elaborated lateral force microscopy (LFM) measurements performed on a scanning probe microscope using silicon-nitride microcantilever probes. The thin-film samples are synthesised by using pulsed laser deposition, which enables obtaining precise stochiometric elemental properties. The LFM measurements allow obtaining single-asperity contact conditions in the studied tribo-pair, which is studied experimentally considering the mentioned external influences as the variable process parameters. In order to obtain an in-depth insight into the dependencies of nanoscale friction on these parameters, the obtained experimental data is used to train various machine learning (ML) algorithms. The resulting predicted values of the nanoscale friction force are therefore obtained by using random forest, multilayer perceptron and support vector regression ML methods. In order to assess their predictive performances, all the used algorithms are validated on a separately measured test dataset. The best predictive performances are obtained by using the support vector regression algorithm, resulting in the highest achieved coefficient of determination (R2), allowing the prediction of 90 % of the variance of the experimental measurements.

In more than half of the stroke survivors aged 65 or more, serious long-term disability is developed. Patients’ arms are often affected, resulting in a partial or complete loss of motor functions. Therapy waitlists, influenced also by the global population ageing, are therefore growing, while the sessions last too short. A possible solution to these challenges is the development of active rehabilitation devices that enable more frequent and intensive rehabilitation sessions. A concept of a compact rehabilitation device for the elbow, the forearm and the wrist, with an additional hand module treated as an end- effector, is proposed in this work. The device has five active and three passive joints. The dimensions of the exoskeleton links are designed by using a fully functional human arm model corresponding to the 50th percentile male ; the installation can, however, be adjusted to a wider range of dimensions via configurable prismatic joints. The device is conceptualized and modelled by using Blender. Its configuration is based on kinematic analyses and compared to the ranges of motions of each forearm joint. The concept and its kinematics are structured as a transformation tree and implemented via the Unified Robot Description Format in the Robotic Operating System. An inverse kinematics problem is formulated next by employing homogenous transformation matrices ; a custom-made closed-form analytical solver is generated to obtain faster and more consistent real-time solutions. To validate the suitability of the device for sensory-motor rehabilitation of the activities of daily living, a reachability analysis is finally performed by using reachability maps implemented in the open-source library OpenRAVE.

The growing use of energy harvesting in wearable technologies made evident the potential limits in applying piezoelectric devices excited by random human motion. Piezoelectric energy harvesters are, in fact, characterised by a narrow area of optimal operation around their eigenfrequency. An optimization of the design parameters of such harvesters by using the design-of-experiments methodology, coupled with suitable frequency up- conversion excitation, can lead to the development of improved configurations of functional wearable devices. The validation of this approach via elaborated finite element models performed in this work allows proving its validity, but the resulting designs have to be experimentally verified as well. Suitable experimental setups, enabling harmonic, as well as frequency up-conversion excitation, are thus developed, enabling the validation of different dynamical conditions. The thus obtained experimental responses are compared to those attained via numerical simulations, allowing to deduce considerations important for the development of piezoelectric energy harvesters applicable in factual wearables.

A viable approach to obtain mechanical properties such as Young’s modulus and hardness, is testing on a nanoindentation device. Such an experimental procedure can, however, be time-consuming and expensive. Finite element analysis (FEA) can be employed to minimize the number of required measurements, i.e., to obtain numerically the load vs. indentation depth curves for varying input parameters, hence extracting the resulting elasto-plastic material properties. A methodological approach is used in this work to correlate the responses obtained via FEA to nanoindentation experimental data. A (100)- oriented single crystal silicon wafer is used as a testing sample. Numerical simulations are performed by employing a bilinear elasto-plastic material model. A sensitivity analysis of the characteristic parameters of the material model is then conducted on the numerically obtained load vs. displacement curves. The proposed methodology enables replicating the experimental curves with estimated errors lower than 1 % and 15 % for Young’s modulus and hardness, respectively. The performed analyses allow establishing also that, when evaluating numerically hardness, the tip radius and shape significantly affect the accuracy of the results, especially for lower indentation depths.

Rehabilitating patients with upper limb poststroke paresis is a difficult challenge for both therapists and patients. In fact, to be as effective as possible and enable long-term restoration of arm’s motoric function, therapy must be introduced early and combined with frequent rehabilitation sessions. Active rehabilitation devices are establishing themselves as a likely solution, as they not only provide highly repetitive movements enabling to reinforce the connections between the visual and the motion sensory systems, but also allow alleviating the workload of physiotherapists. The conceived design configuration of an upper limb rehabilitation device, comprising 14 degrees of freedom, of which 8 are active, is thoroughly analysed in this work. The ranges of motion are validated against human arm movements using functional model representations. The sensors and their approximate positioning are considered as well. An in-depth analysis and characterization of the kinematic performances of the device is performed by using the Denavit-Hartenberg parameters. The simplified model of the rehabilitation device, and the resulting kinematic tree, are then implemented in the robotic operating system, enabling the simulation of its behaviour. The compatibility of the device for the rehabilitation of daily life activities is also validated by using a workspace analysis based on the functional representation of the arm.

Friction is an omnipresent phenomenon in all mechanical systems, inducing uncertainties and acting as a major disturbance in manufacturing technologies and in the field of the micro- and nanoelectromechanical systems (MEMS & NEMS). The effects of friction can generally be compensated in the macro- and mesoscale applications. Multiple concurrent effects of various atomic-scale phenomena in the asperity contacts hinder, however, the prospect of a satisfactory insight into the fundamental tribological behaviour in the micro- and nanoscales. An in-depth fundamental understanding of nanoscale frictional behaviour is, thus, of outmost technological importance. An approach using molecular dynamics (MD) simulations is, hence, proposed in this work to study the tribological behaviour in the nanoscale (atomic) contacts. Recent thorough scanning probe microscopy experimental measurements of nanoscale friction on various thin-film materials are thus used as benchmark for MD simulations, allowing to attain important insights into the dynamics of a sliding tip on an aluminium thin-film surface while varying the normal loads. A sound basis for future more complex models, which will include adhesive effects and oxide layers, is thus accomplished, creating the preconditions to deepen further the fundamental knowledge of important tribological phenomena.

Publisher Copyright: © 2021 Proceedings of the 21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021. All rights reserved. Aerostatic bearings are externally pressurized gas lubricated bearings. Aerostatic bearings are used in high speed and precision motion applications due to low friction and high accuracy. They use a restrictor to limit the flow of the gas into the bearing gap. The presence of the restrictor increases the stability of the bearing against self-excited vibrations. This study focuses on porous graphite restrictors and the effect of permeability on the behaviour of the bearing. The bearings were studied both experimentally and with a simulation model. Flat bearing pads with 37 mm diameter and different restrictor bulk permeability were manufactured and tested. Experimental measurements were conducted on a test setup allowing loading of the bearing against a ground steel plate. The load was supplied with a series of weights. The air gap was measured with a linear length gauge, measuring the displacement of the air bearing. The pressure was controlled with a regulator and the flow rate into the bearing was measured.In order to build an accurate simulation model, the permeability of the used material was calculated from the measured short circuit flow through each 4.5 mm thick sample. The flow in the porous material and in the restrictive layer follows Darcy’s law, the flow in the air gap is described by the Navier-Stokes-equation. The simulation model was validated with experimental results. Measurement and simulation results include the air gap height, load and flow rate at a supply pressure of 0.4 MPa. According to previous research and preliminary results the surface restrictor layer has increased the resistance of the bearing to self-excited air-hammer vibration, leading to a higher load capacity.

As a major source of uncertainties in micro- and nanopositioning devices, friction, characterised by complex stochastic phenomena, is one of the major challenges in developing reliable predictive models od systems’ behaviour. Based on recently performed lateral force microscopy experimental measurements of thin films’ nanoscale friction, fundamental frictional mechanisms in atomic-scale single- asperity contacts are investigated in this work vs. the concurrent influence of multivariate process parameters. The hence proposed nanoscale friction models are developed using innovative artificial intelligence-based methods. In fact, although in a previous study the employment of conventional (black box) machine learning methods provided rather good predictive performances, the intrinsic nature of these models prevents their usage in most practical applications. The novel methodology proposed in this work allows, in turn, attaining an extremely simple mathematical formulation (i.e., a white box model) providing an immediate insight and a unique scientific perspective into the multidimensional dependence of nanoscale friction on the studied variable influencing parameters. What is more, this artificial intelligence-based approach allows achieving a high predictive performance with R2 values in the range of 0.75, while the simplicity of the obtained expressions makes future studies and possible practical applications (e.g. in the corresponding control algorithms) rather straightforward.

High aspect ratio manufacturing in the micro dimensional range by the micro milling process represents some difficulties for diverse applications such as micro moulds, micro channels, micro gears, miniaturized surgical instruments, etc. This study investigates the thin wall machining with different machining approaches and applies 3D finite element modelling (FEM) for the minimum machinable wall thickness to improve the experimental machining and enhance the quality of the machined features. The high stress distribution during machining the thin features are presented and the smallest machined wall is investigated. Finally, the FEM prediction resultsare compared against the experimental tests.

Portable machine tools are developed to address specific applications needs, such as machining of large components. However, they lack in performance such as stiffness. For such a low-stiffness portable machine tool, in this work, it is analysed the possibility and feasibility of employing the motors absorbed current measurements during actual machining operations as a means to monitor the cutting process and eventually compensate the tool deformations due to the cutting forces. In-process tool-path compensation achieved through a sensorized machine is of extreme interest from the costs point of view, especially for portable or dedicated task machine tool. In this paper, measurements of cutting forces, feed axes and spindle motors absorbed currents were carried out simultaneously for different cutting conditions. It is found that good correlations can be established between specific feature of the cutting force and axis motors absorbed current, the result demonstrates that the absorbed current measurements are reliable indirect measurements of the cutting forces and can therefore be employed in an in-process tool-path compensation.

Micro polishing is an important process when fine surface quality and low form error are required in the micro scale domain. This process has several differences from conventional polishing and some of the factors can not be neglected any longer. In this work, a study on the thermal behaviour of a micro hexapod-based machine is conducted. The main causes of thermal deformations are addressed and analysed. The contributions are then evaluated and compensation path strategies are discussed. The main criticalities when dealing with micro polishing are due to the small tools used. Micro tools require higher speeds than conventional polishing. High spindle speeds generate heat and therefore thermal deformations. This adds up to the movement of the Hexapod while performing polishing. The observed total deformation in the polishing tool axial direction reached 8.2 μm. Such a large deformation can introduce a potential error in the final material removal up to 50% if not adequately compensated.

The present work focuses on the influence of the composition of the protective gas (argon or nitrogen) used in laser‐based powder bed fusion (L‐PBF) on the nitrogen content, microstructure and hardness of AISI 316L austenitic stainless steel. L‐PBF of AISI 316L powder using Ar gas resulted in loss of nitrogen in the final part. On the other hand, L‐PBF using N2 gas resulted inan increase in nitrogen content in the final part, showing that nitrogen is absorbed during L‐PBF manufacturing in N2 gas. The nitrogen absorption implies that the build part is actually AISI 316LN rather than AISI 316L.The microstructures of 316L specimens manufactured in both atmospheres exhibited highly elongated γ‐austenite grains, with acellular structure. The hardness of the part manufactured in N2 gas was systematically higher than the part manufactured in Ar. For the part manufactured in Ar, a clear gradual decrease in hardness was observed with increasing distance from the build plate, whilefor the N2 manufactured part this hardness decrease is first observed at some distance from the build plate.For the part manufactured in Ar, a larger variation in the measured nitrogen content was observed. Moreover, a systematically lower and position dependent micro‐hardness and inhomogeneous etching response of this specimen indicate an inhomogeneous microstructure in the build.The results demonstrate that the nitrogen content of L‐PBF manufactured AISI 316L depends on the composition of the gas atmosphere used in the chamber. It is discussed qualitatively how desorption and absorption of nitrogen from the applied atmosphere play a role on the resulting composition and microstructure of the build part.

Different fabrication methods can be applied for micro fabrication, all characterized by their specific processing time and cost. However, by using the additive manufacturing (AM) technologies for direct micro manufacturing of complex micro geometries the average production time and cost can be drastically reduced. This study investigates an AM-based fabrication method for the production of microstructure surfaces with different feature sizes (50-150 μm). The experiments presented in this work have been carried out in a specifically designed vat photopolymerization AM machine suitable for precision printing developed, built and validated at the Technical University of Denmark (DTU). The AM method was evaluated in terms the capability of the system to produce micro pillars and holes array in different sizes and with increasing geometrical complexity.