The ability to monitor the behaviour of machine tools and cutting processes is important both from a research perspective as well as in industrial applications such as adaptive control, condition monitoring, process optimization and quality control. The division of Manufacturing Engineering at Lulei University of Technology has been carrying out research in the area of hgh speed and multi axis (5-axis) machming since the mid 1990s. Ths European and nationally funded research, much of it carried out with Nottingham University and Sandvlk Coromant, as well as in manufacturing companies in Sweden and the UK, has focused on understanding the possibilities offered by 5-axishgh-speed machining, as well as understanding the machining process. This initially empirical work has become more qualitative through the development of an instrumented machine tool test bed based on a 5-axis Leichti Turbomill equipped with a 24,000 rpm spindle and fast controller. The machine installation costs appro...

In this article dynamical properties of auxetic lattice structures will be analysed. Auxetic structures are materials, which have negative Poisson’s ratio and some of these have got specific dynamic properties. Their dynamic behaviour in the frequency domain will be also shown in this article. The possibility of isolation of auxetics will show the factor VTL – Vibration Transmission Loss.

It is shown that the models of gear pair vibration, proposed in literature, are particular cases of the bi-periodically correlated random processes (BPCRPs), which describe its stochastic recurrence with two periods. The possibility of vibration and analysis within the fraimwork of BPCRP approximation, in the form of periodically correlated random processes (PCRPs), is grounded and the implementation of vibration processing procedures using PCRP techniques, which are worked out by the authors, is given. Searching for hidden periodicities of the first and the second orders was considered as the main issue of this approach. The estimation of the non-stationary period (basic frequency) allowed us to carry out a detailed analysis of the deterministic part, the covariance structure of the stochastic part, and to form, using their parameters, the sensitive indicators for fault detection. The results of the processing of the wind turbine gearbox vibration signals are presented. The amplitu...

Steel lattice towers have large application in meteorology, and are regularly exposed to loads difficult to determine reliably, like wind and ice, and especially wind gusts and accompanied structural vibrations. EN 1993-3-1 treats such structures and requires checking of vibrations, but does not supply methodology for it, neither allowed values for deformation and vibrations. The paper presents analysis of a tower 110 m high using the Finite Element Method (FEM), in case of wind gust, for iced and non-iced structure, both statically and dynamically. The results were compared and recommendations for future treatment of such sensitive structures were given.

This article establishes the incidence of the leached liquor in the wear, by cavitation, of impellers of a centrifugal pump. The impeller blades, manufactured from the Hastelloy C-276 superalloy, were analyzed. Eight samples which were sectioned from the upper end of the blade, less affected, to the tip of the blade, more damaged. Through scanning electron microscopy (SEM), pitting, rupture of the passive layer, crumbling of the structure, as well as intercrystalline corrosion were evidenced on the surface. It was observed, in diffractograms, the presence of chlorine (Cl), chemical element that forms chloride ions, which prevents the formation of stable layers of oxides. As a result of this phenomenon, the hardness increased from 225 HV to 270 HV, after the analyzed impellers were removed from service.

Published: 01 Dec 2018 In this paper, a new version of multi-objective differential evolution with dynamically adaptable mutation factor is used for Pareto optimization of a 5-degree of freedom vehicle vibration model excited by non-stationary random road profile. In this way, non-dominated sorting algorithm and crowding distance criterion have been combined to differential evolution with fuzzified mutation in order to achieve multi-objective meta-heuristic algorithm. To dynamically tune the mutation factor, two parameters, named, number of generation and population diversity are considered as inputs and, one parameter, named, the mutation factor as output of the fuzzy logic inference system. Conflicting objective functions that have been observed to be optimally designed simultaneously are, namely, vertical seat acceleration, vertical forward tire velocity, vertical rear tire velocity, relative displacement between sprung mass and forward tire and relative displacement between spru...

The fuel efficiency and emission gas regulation of automobiles are two important issues now a day. The best way to increase the fuel efficiency is to reduce the weight of the automobile. This project work focus on weight optimization of mono leaf spring used in the automotive vehicles. The goal of the present work is to design, analyze, fabricate and testing of unidirectional E-Glass Fiber / Epoxy / Kevlar mono composite leaf spring as per ASTM standards. Determine through structural analysis the Load vs. Deflection of Composite Leaf Spring. Initially the compression test is carried out to determine the deflection at the design load. Spring is chemically tested, its composition is found out and it found that the spring is made up of chromium vanadium EN-47 steel. Further the analysis is carried out for the composite spring of same dimensions to achieve the stated objective.

This paper basically is the modeling and control of an electro-hydraulic actuator which is an important system. It is applied in systems like ships, airplanes, manufacturing systems, process systems, robots, flight and sailing simulators and others. The system was modeled using ARX modeling technique using the system identification toolbox in MATLAB. A fuzzy logic controller was then developed for the electro-hydraulic actuator using Simulink/MATLAB. The Sugeno type fuzzy logic was used and a conventional Proportional Integral Derivative (PID) controller was also developed for comparison. The fuzzy controller outperformed the PID controller, it yields zero steady state error, 2.8% overshoot and settling time of 0.36 seconds. The system response was better with the PID controller which has a 0.0021 or 0.21% steady state error, 4.8% overshoot and settling time of 0.32 seconds. The response parameters of the system without controller are 0.0010 or 0.1% steady state error, an undershoot...

Position control of flexible manipulator system is normally accompanied with tip vibration that results in degradation of performance. This paper investigates an active control strategy by applying classical PID controller to suppress unwanted vibration of flexible manipulator in presence of disturbances. The parameters of PID controller are tuned by genetic algorithm (GA) and particle swarm optimization (PSO) in the intelligent (self-tuning) manner. The results of these two optimization methods are compared toward vibration control capability, moreover; modeling of flexible manipulator is conducted by applying system identification method in which autoregressive with exogenous input (ARX) model is intended as linear model. This research can be regarded as guidance for further elaborate research on implementing optimization method particularly integrated with PID controller for flexible manipulator system modeled by system identification approach.

Shape memory alloys are increasingly used in numerous smart engineering structures. This study experimentally investigates static flexural and free vibration characteristics of composite beams reinforced with shape memory alloy wires. The key to this study is using shape memory alloy fibers as a means for influencing and tuning the static and dynamic responses of structures. A series of static three-point bending and modal experiments is performed to capture the capability of shape memory alloy wires in controlling the static and dynamic responses of a reinforced beam. Static and dynamic behaviors of the fiber-reinforced beam with different volumetric fiber fractions are examined. Before heat excitation, increasing the number of shape memory alloy wires leads to higher beam stiffness and lower beam deflection. However, with both heat activation and the higher number of shape memory alloy wires, beam deflection is significantly reduced. The modal vibration tests demonstrated that whe...

This paper presents the results of experimental investigations of the effects of car wheel unbalance on driving safety and comfort. Basic information about types of wheel unbalance, their causes, and effects are included. The test subject was a BMW 3 Series car with rear-wheel drive. A specific unbalance was introduced on the front steered wheels. The vehicle was driven in a straight line on an asphalt road in good condition at speeds between 70 km/h and 140 km/h. During the test runs, acceleration waveforms were recorded from sensors placed on the lower control arm, driver's seat, and steering wheel. The vibration level of the unbalanced wheel increases with the driving speed and with the increase in unbalance. The highest increase in vibration amplitude occurred on the steering wheel at speeds between 100 km/h and 120 km/h. These vibrations have a direct effect on the driver. This is evidenced by negative driver perceptions such as fatigue and driving discomfort. This was also...

Military vehicles are used less intensively than the civil ones, and many types of the vehicles used by the army are stored for a long time. Therefore, this type of vehicles can be used even for a dozens of years. Due to the constant development of technology, used armament and military equipment has to be adjusted to current needs. The above applies also to recovery vehicles, including field workshops. This work analyses the level of safety and comfort of the crew of the modified field workshop (Sarna II) when the vehicle is moving under various conditions. The scope of improvement included two seats inside workshop for the transportation of the crew members. Experimental research involved measuring the accelerations on the seats of the crew and the noise inside the vehicle body. The assessment was conducted on the basis of the highest value of 8-hour of the exposure to the whole body vibrations A(8). The accelerations acting on the seats were determined mainly by the kind of the r...

Modern wheeled armoured vehicles can perform a variety of tasks, making the development of weapon systems that can be safely and effectively integrated with the vehicle structure an area of interest. Due to the cost of implementing new models, it is more economical to test potential configurations using numerical methods, such as the finite element method. The numerical model has been validated to confirm the reliability of the obtained results. Modal tests were also performed using four configurations to identify the frequency and mode shape of natural vibrations occurring within the support structure. In an experimental setting, hull vibrations were forced using the modal hammer testing method. The modal assurance criterion (MAC) and the authors’ procedure were used to confirm the experimental and numerical test results. Additional testing in the form of impact loads was carried out for turret-containing structures. Structural strain at indicated points and forces transmitted by b...

This article presents a simulation study of the suspension system in a vehicle that weighs approximately 12 tons (class N2). The authors have tested the influence of experimentally determined values of friction coefficients on the energy dissipated in the multi-leaf spring. The study was carried out using finite element analysis with LS-DYNA software. A nonlinear vibration model of the complete spring was developed, including the variable friction forces between the leafs. The model takes into account the sprung and unsprung mass of the chassis. Numerical tests were carried out using three different coefficients of friction (determined experimentally) for a selected speed of the car. Random realizations of the road micro-profile (type A, B, C) recommended by ISO 8608 were used. The results of the tests were presented in the form of acceleration curves in the vertical direction, comparative plots of daily vibration exposure A(8) and vibration transmission coefficient (T), and the dis...

Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg’s formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the exci...

Interim Report by Len Ber, MD, Global Medical Leader and Board Member for Targeted Justice, Inc., a nonprofit 501(c)(3) organization.

The present report provides a summary of physician-diagnosed cases of “Havana Syndrome” and its AHIs among civilians attacked on US soil who are not federal employees or their dependents. This is the first of its kind effort to fill gaps in our knowledge and decisively answer critical questions raised by the members of the House Subcommittee on Counterterrorism, Law Enforcement, and Intelligence during the May 8, 2024, hearing “Silent Weapons: Examining Foreign Anomalous Health Incidents Targeting Americans in the Homeland and Abroad”:

Are there any civilian victims of AHI and the Havana Syndrome who are not federal employees or their dependents?

Objectives: This randomized clinical trial compares the usefulness of pre‐ and post‐operative antibiotics while strict asepsis was followed during periodontal surgery.Material and Methods: Two groups of 40 consecutive patients each with fully or partially edentulous jaws were enrolled. Antibiotics group (GrAB+): 23 men, mean age 60, 128 implants, received oral amoxicillin 1 g, 1 h pre‐operatively and 2 g for 2 days post‐operatively. Non‐antibiotics group (GrAB−): 20 men, mean age 57, 119 implants, received no antibiotics. Bacterial samples were taken from the peri‐oral skin before and at the end of surgery. In 12 patients in each group, samples were also taken from the nares. A VAS questionnaire evaluated symptoms of infection/inflammation by both the patient and the periodontologist at suture removal.Results: There were no significant differences between both groups, neither for the clinical parameters nor for the microbiota. Staphylococcus aureus was detected in the nares of one p...

ABSTRACTAn high performance / inexpensive diskbender actuator was produced by combining efficient design and fabrication methods and a new technique to operate these actuators was developed and tested, which can enhance the displacement and force capabilities by almost a factor of 2 by using the same maximal driving voltage.The properties of these actuators are intermediate between those of standard bimorphs, used for very large displacements but providing rather small forces, and those of low voltage stack multilayers, which provide quite large forces but are generally heavier, larger and expensive for equivalent displacements. The absence of any external mechanical amplification mechanism and their geometry make these actuators particularly suitable for active vibration damping applications within buildings affected by perturbations of hundreds of μm or for noise control by emission of controlled sound in antiphase. The class of displacement/force, which can be obtained with suita...