Mechanics and Control covers a wide range of theoretical and applied aspects of mechanics, mechanical engineering, vibration theory, machine dynamics, robotics, mechatronics, vibroacoustics, control of dynamical systems, active noise and vibration control methods, smart technologies, mechanics of materials, fluid mechanics, thermodynamics, operational reliability, problems of computer aided simulations and design and noise and vibration environment protection.
AGH University of Science and Technology Press
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COMPLETE KINEMATIC ANALYSIS OF THE STEWART–GOUGH PLATFORM BY UNIT QUATERNIONS
In this paper, a complete analysis of Stewart–Gough platform kinematics by unit quaternions is proposed. Even when unit quaternions have been implemented in different applications (including a kinematic analysis of the Stewart platform mechanism), the research regarding the application of this approach is limited only to the analysis of some issues related to the kinematic properties of this parallel mechanism. For this reason, a complete analysis of the Stewart–Gough platform is shown. The derivation of the inverse and forward kinematics of the Stewart platform using unit quaternions shows that they are suitable to represent the orientation of the upper platform due to their simplicity, equivalence, and compact representation as compared to rotation matrices. Then, the leg velocities are derived to compute these values under different conditions.
Copyright (c) 2019 Mechanics and Control
ROTOR DYNAMICS AND STATOR VIBRATIONS OF A NOVEL IPM SYNCHRONOUS MOTOR
The paper presents rotor-dynamical computations of a technology demonstrator of an interior permanent magnet (IPM) synchronous motor that was designed at the Research and Technology Centre of Siemens AG in the framework of the European funded project named MotorBrain. The computations were split into parts consisting modal and harmonic analysis performed numerically using FEM algorithms and the post-processing estimation of the amplitudes of rotor displacement and velocity in the whole range of motor rotation speed. Authors determined modal damping ratios of different oscillation modes and found values of resonance frequencies. In a further step forces were applied to the rotor in order to determine oscillation amplitudes of points placed along the rotor geometrical axis in the case of both mechanically and electromagnetically excited rotor. The computations were performed for the excitation of the first and the second flexural vibration. Except of rotor-dynamical computations authors performed vibration analyses of the stator together with the motor housing. The stator resonance frequencies and its modal deformation shapes were determined. In a further step electromagnetic forces acting on stator teeth were numerically found. These forces were then applied on each stator tooth in order to perform harmonic vibration analyses and determined the spatial average velocity of motor housing circumference area.
Copyright (c) 2017 Mechanics and Control
THE USE OF DIGITAL IMAGE CORRELATION IN THE STUDY OF ACHILLES TENDON STRAIN FIELD
The paper presents an application of vision-based measurement method in experimental mechanics of biological materials. The displacement and strain fields of human Achilles tendon specimen under tensile test were computed using digital image correlation method. Different software applications, both commercial as well as open source ones, were compared. The performance of algorithms was tested based on a referential measurement, carried out by a commercial software with affine model of deformation implemented. The root mean square error of a difference between strain obtained using reference measurement and each of the analyzed programs was computed. Additionally, an example of full field computation of displacement and strain field was presented.
THE APPLICATION OF SELF-EXCITED VIBRATIONS FOR DYNAMIC STRAIN MEASUREMENTS CARRIED OUT BY VIBRATING WIRE TENSOMETERS
This study examines the set of vibrating wire extensometer, in which to maintain natural vibrations of the wire Van der Pol generator has been used. Excited in this way, self-exited vibrations allow for uninterrupted strain measurements over time, including fast-changing strains as well as chaotic nature strains. For two typical vibrating wire gages used in the industry, the impact of the wire extension speed on its metrological characteristics and applicability has been analyzed.
GUITAR PLAYING ROBOT, A TOOL ASSISTING INSTRUMENTAL RESEARCH
The article is about use of automatic mechanism able to play an instrument in research about play repeatability. Repeatability in this case refers to the time delays between played notes in the sequences. Subject will be discussed based on a guitar playing robot. During the research with the use of guitar playing robots, some conclusions were made that confirm, that human is unable to play twice sound sequences maintaining high repeatability . It is also proven, that use of robotic musical instrument (RMI) helps to obtain play repeatability of the sound sequences much higher than the one obtained by the human musician.
ON NONLOCAL MODELING IN CONTINUUM MECHANICS
The objective of the paper is to provide an overview of nonlocal formulations for models of elastic solids. The author presents the physical foundations for nonlocal theories of continuum mechanics, followed by various analytical and numerical techniques. The characteristics and range of practical applications for the presented approaches are discussed. The results of numerical simulations for the selected case studies are provided to demonstrate the properties of the described methods. The paper is illustrated with outcomes from peridynamic analyses. Fatigue and axial stretching were simulated to show the capabilities of the developed numerical tools.
Copyright (c) 2018 Mechanics and Control
TIME-VARIANT FREQUENCY RESPONSE FUNCTION FOR ANALYSIS OF TIME-VARYING MECHANICAL SYSTEMS
System Identification is an important and often complex process in many areas of engineering. This process is not easy when parameters of the analysed system vary with time. In such cases classical methods fail to identify parameters properly. The work demonstrated in this paper deals with identification of natural frequencies of time-variant systems. The paper presents the application of the Time-Variant Frequency Response Function for this analysis. Calculation procedure requires division of output spectrum by input spectrum which often leads to division by close to zero values, and that leads to infinite (or undefined) values of resulting transfer function. Additional processing is required for interpretation. The major focus and challenge relate to ridge extraction of the above time-frequency characteristics. The methods presented in the paper are illustrated using experimental multi-degree-of-freedom system. The results show that the proposed method captures correctly the dynamics of the analysed time-variant systems.
EXPERIMENTAL INVESTIGATIONS ON ENERGY HARVESTING FROM MECHANICAL VIBRATIONS OF BUILDINGS USING MACRO FIBER COMPOSITE
The monitoring of a structure (e.g., a building) enables safe utilization of such a structure. A large number of sensors that measure selected parameters are often required in applied monitoring systems. Cables or batteries are used to power such sensors. This leads to an increase in utilization costs, as the cables have to be spatially located in a monitored building structure, or batteries have to be changed periodically. The use of the natural properties of piezoelectric materials that convert mechanical energy into electrical energy in places where sensors are mounted is a promising field of wireless monitoring system development. This article presents the results of an experimental study for an energy harvesting system using a piezoelectric composite – the Macro Fiber Composite (MFC). The device used for energy harvesting has a beam structure that was achieved by gluing steel and MFC together. In laboratory research, the characteristics of generated currents and electrical power were obtained for several values of vibration amplitude. The most important conclusion was that the resonant frequency of a piezoelectric beam generator should be established (by the selection of proper dimension or/and mass) both for the vibration frequency of the monitored mechanical structure and the vibration amplitude of this structure.
CONTROL SYSTEM PREVENTING THERMAL GRADIENT DEVELOPMENT ON FOILS OF FOIL BEARING
This article presents attempts at automating a control system to reduce temperature scatter on the foil of a foil bearing. The control system reads the temperatures at six circumferential locations of the bearing’s foil and distributes control currents to the thermoelectric modules integrated into the bearing’s bushing. Three basic approaches have been proposed and tested: 1) a simple hot-spot tracking algorithm assigning predefined current values to the modules closest to the hot-spot location; 2) a tracking algorithm reducing abrupt changes in the control currents and, in effect, the local heat flux distribution; and 3) a tracking algorithm enhanced with a PID controller. The proposed controller has been implemented and compared to the performance of a temperature controller that does not have tracking capabilities. The implemented control strategies have proven the feasibility of temperature scatter reduction inside the investigated bearing. In most test cases, the instantaneous gradient reduction exceeded 50% (reaching 63% at its best).
SHAPE-MEMORY MATERIALS AS CONTROL ELEMENTS USED IN DOT BRAILLE ACTUATOR
The objective of this paper is to show a designing process for actuators that utilizes shape-memory materials. Analytical studies are carried out to design a dot actuator to be used in an electronic Braille display. Shape-memory materials are a relatively new group of smart materials that exhibit the transformation of their internal structures in solid state phases resulting from external mechanical or thermal excitation. This unique property shows up as three phenomena: one- and two-way memory effects as well as superelasticity, which all significantly influence the change of both the material properties and geometry. Hence, shape-memory materials are used as actuators effectively controlled by the above-mentioned types of excitation. The work presents the design guidelines for a proposed technical solution as well as the phenomenon utilized in the elaborated model of the actuator. The authors derived the mathematical descriptions for the proposed design configuration and an example of the calculations is shown. Moreover, the characteristics of the elaborated configuration are also discussed, taking into account the range of application areas.
PHYSICAL MODEL OF VEHICLE ENGINE MOUNT WITH MAGNETORHEOLOGICAL DAMPER
A physical model of a vehicle engine mount incorporating a magnetorheological (MR) damper in squeeze mode is investigated and the structural design and operating characteristics of the MR damper are provided. The mathematical model of an engine mount is formulated. Kinematic excitations are assumed to be those emulating road profile-chassis (car body) interactions. Simulations of engine vibration are performed to determine the efficiency of the proposed engine mount. Conclusions are drawn concerning the potential applications of the MR damper in vehicle engine mounts.
CONDITIONING ELECTRONICS IN A SELF-POWERED VIBRATION REDUCTION SYSTEM: EXPERIMENTAL TESTING
The paper summarises the results of laboratory testing of a vibration reduction system with energy harvesting capability, implemented in an 2 DOF mechanical application. The vibration reduction system comprises a commercially available RD-1005-3 type magnetorheological (MR) damper and an electromagnetic energy transducer (EPE) executing the reciprocating motion. The aim of the experiment was to compare the performance of the vibration reduction with two types of power conditioning systems and that in which the MR damper coil is fed directly with energy generated by EPE. Frequency characteristics are provided showing the plots of transmissibility coefficients, MR damper force, voltage generated by EPE, current intensity in the MR damper control coil, supplied electric power and mechanical power dissipated by the damper.
Copyright (c) 2016 Mechanics and Control
TEST BED FOR THE SIMULATION OF MAGNETIC FIELD MEASUREMENTS OF LOW EARTH ORBIT SATELLITES
The paper presents a test bed designed to simulate magnetic environment experienced by a spacecraft on low Earth orbit. It consists of a spherical air bearing located inside a Helmholtz cage. The spherical air bearing is used for simulating microgravity conditions of orbiting bodies while the Helmholtz cage generates a controllable magnetic field resembling the one surrounding a satellite during its motion. Dedicated computer software is used to initially calculate the magnetic field on an established orbit. The magnetic field data is then translated into current values and transmitted to programmable power supplies energizing the cage. The magnetic field within the cage is finally measured by a test article mounted on the air bearing. The paper provides a description of the test bed and the test article design. An experimental test proves the good performance of the entire system.
STRENGTH STUDY ON SODA-LIME-SILICATE TOUGHENED GLASS
Toughened soda-lime-silicate glass is a popular material widely used in construction due to its very good functional properties, characterised by high strength, safety in use, fire resistance, and also good thermal insulation. In this study, tests were conducted to describe the dependence between the bending strength of ESG toughened float glass and the thickness of the sample, the state of the sample edge, and the application of security film. Tests were also conducted on the influence of the placement of openings used for mounting glass screens used to secure display cases and other objects of a similar nature. The information obtained was used to design glass security screens and a new type of display case, a closed cassette with a glass screen, intended for use in protecting works of art from acts of vandalism and the destructive influence of environmental conditions.
QUALIFICATION METHODS FOR ASSESSMENT OF ANNOYANCE OF IMPULSIVE SOUNDS
The paper presents the work on the problem of qualification of impulsive sounds for applying the adequate value of impulsive adjustment. Impulsive events must be included in the assessment of noise in Poland. There are no agreement for using the objective methods that could classify impulsive sounds on the basis of measurable physical characteristics of the impulses. Moreover, the arbitrary classification includes only a several specified sources. The paper presents the review of methods and criteria for qualification of the impulses, and provides the results of applying these methods on certain impulsive noise source – collision of the wagons.
FINITE ELEMENT ANALASIS OF ADHESIVE BONDS USING THE COHESIVE ZONE MODELING METHOD
The paper covers the subject of FE modeling of adhesive joints, which is gaining more and more attention in the contemporary industry, especially in the aerospace and automotive sectors. This technique of creating structural connections possesses many advantages over mechanical or welding methods and it seems that it will be exploited extensively in the future mechanical design. Ability of joining dissimilar materials, decreased minimum member cross-section size and corrosion inertness can be considered as its most important features. However, in the era of virtual prototyping, it is necessary to conduct reliable computer assisted analyses of these type of joints. It is because most of the contemporary structures are developed as numerical models first, and only the final product is prototyped physically, to validate the simulation results. The aim of this paper is to demonstrate how to elaborate a reliable and accurate adhesive joint models, using a cohesive zone modeling (CZM) method. The major profitable consequence of using the CZM technique is that it introduces into the model relatively small number of spatial degrees of freedom, and therefore, allows for short computational times.
STUDY OF FLOW-INDUCED VIBRATION PHENOMENA IN AUTOMOTIVE SHOCK ABSORBERS
The purpose of this study was to develop a model of the dynamic behavior of a hydraulic vehicle double-tube shock absorber. The model accounts for the effects of compressibility, valve stiction, inertia, etc. and can be suitable for use in the analyses on flow-induced pressure fluctuations in the device. The author highlights all major variables to influence the output of the shock absorber, and then proceeds by performing a series of simulations using the developed model. The model is demonstrated to operate well in the large amplitude and low frequency range as well as the small amplitude and high frequency excitation operation regimes. The results are presented in the form of time histories of pressures in each fluid volume of the damper, flow rates through the valves, piston rod acceleration and force. Fast Fourier Transform (FFT) graphs are presented, too, in order to identify major components of the pressure fluctuation phenomena in frequency domain.
MICROSTRUCTURE EVALUATION OF Ni-Mn-Ga ALLOY
This paper summarises the applications of MSMA materials, outlines the mechanism of magnetic shape memory effect and provides the procedure for microstructure evaluation of samples as well as the results of microstructure analysis using the example of the Ni-Mn-Ga alloy.
Copyright (c) 2015 Mechanics and Control
PRODUCTION AND STUDY OF POLYETHER AUXETIC FOAM
The article describes the experiment consisting in production and study of auxetic open-cell polyether foam. In the introduction I briefly explain what auxetic materials are and list their main properties together with possible application areas. Next, detailed information about the background of the experiment is given: important material characteristics and extensive description of the procedure. Further, discussion of the results is presented, basing on microscopic imagery of the obtained auxetic foam. The article describes also tensile tests performed on the produced material and cites quantitative results in the form of text and graphs illustrating the Poisson ratio dependence on deformation, as well as stress-strain relations (true and engineering values). In the final part of the article conclusions are enclosed.
TiNi SHAPE MEMORY ALLOY TENSION AT VARIOUS TEMPERATURES - INFRARED IMAGING OF SHAPE MEMORY EFFECT AND PSEUDOELASTICITY
The mechanical characteristics and the infrared imaging of stress-induced martensite transformation developing in TiNi shape memory alloy (SMA) subjected to tension in various conditions with respect to the SMA austenite finish parameter have been presented. Based on the mechanical curves and their related temperature changes it was found that onset of the martensitic transformation appears at the end of the elastic part of the stress-strain curve, since the temperature starts to increase before the knee in the curve. The uniform temperature distribution observed on the specimen surface at this stage confirms that the initial martensite transformation is macroscopi-cally homogeneous. For the shape memory effect behavior the uniform temperature distribution on the specimen surface was observed during the complete process of the SMA loading which means that the transformation process is macroscopically homogeneous. For the shape memory alloy pseudoelasticity behavior bands of higher temperature have been recorded during the specimen loading and bands of lower temperature during its unloading, manifesting localized Luders-like deformation, caused by the transformation process. As the transformation advances, the higher temperature changes have been recorded. Taking advantages from the infrared technique a new results concerning nucleation and development of the martensite forward and reverse transformation have been obtained. Finally, some examples of the SMA new applications due to the SMA shape memory effect have been presented and discussed.
AN APPLICATION OF RESPONSE SURFACE METHOD TO DESIGN OPTIMIZATION OF A MODEL OF RAIL VEHICLE CONSIDERING UNCERTAINTIES
An application of design optimization methodology performed for a multibody model of real-live rail structure stands for the scope of present work. For carried out analyses a model of five-piece tram has been elaborated and then parameterized to allow for an effective and easy change of checked design configuration. There has been assumed the index of travelling comfort as an object of optimization process. Performed analyses have taken into account the uncertainty dealing with the number of passengers on board. The stiffness coefficients of springs of the primary and secondary suspension systems have been chosen as design parameters. Mentioned index has been calculated with virtually measured accelerations in the passengers area for assumed velocity of a run. For modeled rail there has been introduced roughness defined to represent real geometric imperfections. Response surface modeling based on polynomial regression has been applied as a surrogate for the full model to speed up the dynamic analyses. The work has used genetic algorithms for the optimization. Improved values of studied index confirm better comfort of traveling.
Copyright (c) 2011 Mechanics and Control
MODELLING OF AMPLITUDE-SELECTIVE-DAMPING VALVES
The so-called amplitude-selective-damping (ASD) valving is a relatively new approach for modifying the output of a hydraulic shock absorber. In the automotive industry ASD valves are known to improve isolation from road inputs. During more aggressive maneuvers the systems maintains the performance of a standard (non-ASD) shock absorber. In the paper, the author derives and analyzes a fairly complete state-space model of an exemplary piston-side ASD valve. The model includes key geometric and performance characteristics of the valve. The results are shown in the form of phase plane plots of force-displacement diagrams, respectively, for a twin-tube shock absorber configuration of choice.
PREDICTION OF THE PLASTIC COMPONENT PARTS DURABILITY WITH USE OF A DROP TEST SIMULATION
This paper describes the method of performance of a drop test simulation for elements made of polymeric materials. Possible to use material models were described and material model choices were shown. Material tests needed to obtain material model parameters were presented and the results of analysis and measurement data were shown. As an example a drop test of the housing of a car electrical box made of Polypropylene with 20% Talc filler (PPTD20), have been simulated in ABAQUS/Explicit and results have been compared with data registered by a video camera system during the real drop test of this housing.
nonlinear rate dependent elastic-plastic material model
COMPUTATIONAL MODELLING OF LOCALIZED DEFORMATIONS WITH REGULARIZED CONTINUUM MODELS
The paper presents a short overview of selected problems related to the numerical analysis of localized deformations. After defining the localization phenomenon and the class of gradient models, two simulation examples are shown. They are applications of the plasticity theory with a Laplacian of the hardening parameter and of the damage theory with an additional averaging equation for an equivalent strain measure.
LABORATORY STAND FOR TESTING THE ACTIVE VIBRATION CONTROL SYSTEM WITH ENERGY REGENERATION
The paper describes an active vibration control system for a structure of two degrees of freedom. The system comprises two elastically connected bodies moving along vertical guides. The system structure is additionally provided with two electrodynamical linear motors working in energy regeneration and active vibration reduction subsystems. The combination of these subsystems with a special control system creates a self-powered vibration reduction system, allowing active vibration control of the second body using the energy from the motion of the first body, which was regenerated and stored in capacitors.
DESIGN OF THE LABORATORY STAND FOR TESTING VEHICLE SUSPENSIONS
This paper is devoted to the designing of the laboratory stand for testing car vehicle suspensions. Main parts of the laboratory setup are as follows: a frame construction with vehicle suspension elements, an electro-hydraulic shaker, a hydraulic power supply unit and a measurement and control system. This work provides preliminary analysis of the laboratory setup such as static analysis and dynamic simulations of the system. Results of the calculations were used in the designing process of the laboratory setup.
THE USE OF EVOLUTION ALGORITHMS FOR IDENTIFICATION OF TRANSMISSION BACKLASH
Mechanical propulsion system including, inter alia, an electric motor, shaft and transmission is characterized by certain parameters whose values cannot be calculated using mathematical methods (transmission backlash) or may vary during operation time. Such parameters have to be known to ensure proper operation of the system. In this article a method for identification of these parameters is described. The method is based on an evolution algorithm. This algorithm utilizes natural selection methods and natural transformation processes within a population, similar to those in animal world. The least-fit individuals are rejected by applying the fitness function. The population will improve, and in infinite time it will be perfect. That means that the perfect solution can be attained in a very long time. This time can be shortened by defining the termination criteria, e.g. the identification can be stopped if one of the population individuals has a very low error. Such identification requires a transition function (model), as well as reference measurement made on a real system.
RECOGNITION OF AIRCRAFT NOISE IN LONG-TERM ENVIRONMENTAL MONITORING
Continuous acoustical climate monitoring of a particular area raises problems related to large quantities of the recorded data, which often represents information unrelated to the study source. Manual verification of data is time-consuming and costly. Therefore, to develop effective methods for automatic identification of transport noise sources becomes an important task for the proper determination of noise levels. This paper presents a concept of method in automatic detection and classification of air transport noise sources in the acoustic environmental monitoring.
NUMERICAL TESTS OF THE INFLUENCE OF THE ORIENTATION OF STRATIFICATION ON THE PROCESS OF CUTTING OF ROCKS
The paper presents results of the numerical simulation of the crack propagation occurring in the course of chip element formation in case of cutting stratified rock material. As a result of the simulation, it was found that a characteristic, rapid increase of the loosening force of the chip element occurs when stratification is directed in relation to the cutting direction at an angle of ca. 160°.
IN SITU STUDIES OF SOUND INSULATION INDEX OF NOISE BARRIERS
Outdoor noise barrier is roadside noise reducing device, the primary task of which is the protection of a predetermined sound protection area against road traffic noise. The examinations of acoustic properties of the elements used for construction of noise barriers are usually carried out in laboratory conditions according to the PN-EN 1793-1,2 standard. These examination procedures cannot be applied to existing installations. Therefore problems that are usually neglected are the problems related to the acoustic properties that essentially depend on a series of factors unrelated to the building elements themselves, namely: barrier dimensions, quality of workmanship, barrier location and the type and topography of the ground foundation. In the European Research Project "Adrienne" a methodology has been elaborated for in-situ determination of acoustic parameters of noise barriers. The examination, in which analysis of the system's impulse response after MLS signal actuation and a proper numerical algorithm are applied, leads to determination of airborne sound insulation of the existing constructions as well as the single number sound reflection factors and differences of diffraction properties at the top-edge elements of the barriers. The present paper describes the possibilities of determination of the intrinsic characteristics of airborne sound insulation index for the road traffic noise reducing devices in free field conditions and the determination of single number rating of airborne sound insulation to indicate the performance of the noise barrier.