In the paper, the author presents experimental analysis of propagation of plastic zones in two-dimensional models with different stress concentrators. The experimental tests were carried out by photoelastic coating method on duralumin stripes loaded by tensile stresses. For various levels of loading, the photographs of isochromatic pattern were taken under loading and after removing loading. On the basis of isochromatic pattern recorded for loaded models, the boundaries of plastic zones were determined using the Treska-Coulomb yield condition. The isochromatic pattern taken for the unloaded, but previously partly plastified elements, show the picture of the residual strain remaining in the material. A discussion of the results is presented.

In this paper, the authors investigate a cylindrical shell reinforced by carbon nanotubes. The critical buckling load is calculated using analytical method when it is subjected to compressive axial load. The Mori-Tanaka method is firstly utilized to estimate the effective elastic modulus of composites having aligned oriented straight CNTs. The eigenvalues of the problem are obtained by means of an analytical approach based on the optimized Rayleigh-Ritz method. There is presented a study on the effects of CNTs volume fraction, thickness and aspect ratio of the shell, CNTs orientation angle, and the type of supports on the buckling load of cylindrical shells. Furthermore the effect of CNTs agglomeration is investigated when CNTs are dispersed none uniformly in the polymer matrix. It is shown that when the CNTs are arranged in 90 degrees direction, the highest critical buckling load appears. Also, the results are plotted for different longitudinal and circumferential mode numbers. There is a specific value for aspect ratio of the cylinder that minimizes the buckling load. The results reveal that for very low CNTs volume fractions, the volume fraction of inclusions has no important effect on the critical buckling load.

Purpose: The influence of age-hardening solution treatment at temperature 515 degrees centigrade with holding time 4 hours, water quenching at 40 degrees centigrade and artificial aging by different temperature 130, 150, 170 and 210 degrees centigrade with different holding time 2, 4, 8, 16 and 32 hours on changes in morphology of Fe-rich Al15(FeMn)3Si2and Cu-rich (Al2Cu, Al-Al2Cu-Si) intermetallic phases in recycled AlSi9Cu3 cast alloy. Material/Methods: Recycled (secondary) AlSi9Cu3 cast alloy is used especially in automotive industry (dynamic exposed cast, engine parts, cylinder heads, pistons and so on). Microstructure was observed using a combination of different analytical techniques (scanning electron microscopy upon standard and deep etching and energy dispersive X-ray analysis – EDX) which have been used for the identification of the various phases. Quantitative study of changes in morphology of phases was carried out using Image Analyzer software NIS-Elements. The mechanical properties (Brinell hardness and tensile strength) were measured in line with STN EN ISO. Results/Conclusion: Age-hardening led to changes in microstructure include the spheroidization of eutectic silicon, gradual disintegration, shortening and thinning of Fe-rich intermetallic phases and Al-Al2Cu-Si phases were fragmented, dissolved and redistributed within alpha-matrix. These changes led to increase in the hardness and tensile strength in the alloy.

The paper presents a solution of the control system for fatigue test stand MZGS-100 PL, comprising the integrated Real-Time controller based on FPGA (Field-Programmable Gate Array) technology with LabVIEW software. The described control system performs functions such as continuous regulation of speed induction motor, measuring strain of the lever machine and the test specimen, displacement of the polyharmonic vibrator, as well as the elimination of interferences, overload protection and emergency stop of the machine. The fatigue test stand also allows to set the pseudo-random history of energy parameter W(t).

The rigid finite element method (RFEM) has been used mainly for modelling systems with beam-like links. This paper deals with modelling of a single set of electrodes consisting of an upper beam with electrodes, which are shells with complicated shapes, and an anvil beam. Discretisation of the whole system, both the beams and the electrodes, is carried out by means of the rigid finite element method. The results of calculations concerned with free vibrations of the plates are compared with those obtained from a commercial package of the finite element method (FEM), while forced vibrations of the set of electrodes are compared with those obtained by means of the hybrid finite element method (HFEM) and experimental measurements obtained on a special test stand.

The paper presents the idea of a system for controlling the movement of a flowmeter for air velocity profile measurement. In such a system, due to massive amount of data and limitations of the Data Acquisition Equipment, it is necessary to use moveable sensors. The flowmeter sensor is moved with the use of a linear module with a stepper motor and a tooth-belt drive. The location and speed of the sensor are controlled by a program based on the idea of virtual instrument. The proposed structure allows the user to control operation of the stand and provides automatic measurement. A wide range of velocity and step increments of the stepper motor drive, and flexibility of the virtual instrument software, allow one to create effective measurement systems ensuring sufficiently precise location with optimal time duration of measurement. It is shown that the linear module with tooth-belt is an effective alternative for similar modules with micro-screw drives.

Thrust bearing model is developed for fluid flow calculation and for determination of bearing integral characteristics in the presence of sliding surfaces closure and shaft angular displacements. The model is based on the coupled solution of the problem of incompressible fluid flow between the sliding surfaces and the problem of bearing and shaft elements deformation under the action of the fluid film pressure. Verification of the bearing model results is carried out by the comparison versus the fluid flow calculation results obtained by STAR-CD software and the experimental and theoretical results represented in the certain literature. Thrust bearing characteristics are determined versus sliding surfaces closure and rotating disk (runner) angular displacements. The contribution of the sliding surfaces deformations into bearing integral characteristics is estimated.

There exist cases where precise simulations of contact forces do not allow modeling the gears as rigid bodies but a fully elastic description is needed. In this paper, a modally reduced elastic multibody system including gear contact based on a floating frame of reference formulation is proposed that allows very precise simulations of fully elastic gears with appropriately meshed gears in reasonable time even for many rotations. One advantage of this approach is that there is no assumption about the geometry of the gears and, therefore, it allows precise investigations of contacts between gears with almost arbitrary non-standard tooth geometries including flank profile corrections.

This study presents simulation results that show how this modal approach can be used to efficiently investigate the interaction between elastic deformations and flank profile corrections as well as their influence on the contact forces. It is shown that the elastic approach is able to describe important phenomena like early addendum contact for insufficiently corrected profiles in dependence of the transmitted load. Furthermore, it is shown how this approach can be used for precise and efficient simulations of beveloid gears.

The peculiarity of offshore cranes, i. e. cranes based on ships or drilling platforms, is not only a significant motion of their base, but also the taut-slack phenomenon. Under some circumstances a rope can temporarily go completely slack, while a moment later, the force in the rope can increase to nominal or even higher value. Periodic occurrence of such phenomena can be damaging to the supporting structure of the crane and its driver. In the paper, mathematical models of offshore cranes that allow for analysis of the taut-slack phenomenon are presented. Results of numerical calculations show that the method of load stabilization proposed by the authors in their earlier works can eliminate this problem.

In order for a quadruped robot to be able to move on wheels while keeping its platform in horizontal position, and to walk, the kinematic system of its limbs should be so designed that each of the wheels has at least four degrees of freedom. Consequently, the designed system will have many DOFs and many controlled drives. This paper presents a novel solution in which, thanks to a suitable limb kinematic system geometry, the number of drives for the robot travel function, i.e. travelling on an uneven surface with the robot platform kept horizontal, has been reduced by four which are used only for walking. The robot structure, the required geometry of the limb links and the driving torque characteristics are presented. Moreover, an idea of the control system is sketched. Finally, selected results of the tests carried out on the robot prototype are reported.

A backward tucked somersault from the standing position is analyzed in this study. The used computations were based on a three-dimensional model of the human body defined in natural coordinates. The net torques and internal reactions occurring at the ankle, knee, hip, upper trunk-neck and neck-head joints were obtained by inverse dynamics. The achieved results confirmed the significant loads at the joints at the beginning of the landing phase and revealed the way the analyzed stunt was controlled. It was also shown that the natural coordinates provide a useful environment for modeling spatial biomechanical structures.

Complex multi-disciplinary models in system dynamics are typically composed of subsystems. This modular structure of the model reflects the modular structure of complex engineering systems. In industrial applications, the individual subsystems are often modelled separately in different mono-disciplinary simulation tools. The Functional Mock-Up Interface (FMI) provides an interface standard for coupling physical models from different domains and addresses problems like export and import of model components in industrial simulation tools (FMI for Model Exchange) and the standardization of co-simulation interfaces in nonlinear system dynamics (FMI for Co-Simulation), see [10].

The renewed interest in algorithmic and numerical aspects of co-simulation inspired some new investigations on error estimation and stabilization techniques in FMI for Model Exchange and Co-Simulation v2.0 compatible co-simulation environments. In the present paper, we focus on reliable error estimation for communication step size control in this framework.

The paper presents selected methods used for estimation the unknown geometrical parameters of a spatial mechanism model, used to describe the position and orientation of the end-effector, for example the coordinates of the center points of spherical joints, link dimensions etc. These data are necessary when dealing with computer simulation of any mechanism. The parameters are estimated based on coordinate measurements of selected points, located on the real mechanism links, using a portable manipulator with serial structure composed of 6 revolute joints and a spherical probe, but other techniques of acquiring point coordinates are applicable as well. The described methods can be used in the cases of a disassembled link, an assembled mechanism and redundant data sets. The methods are characterized by accuracy and robustness in the presence of different levels of noise, stability with respect to degenerate data sets, and low computation time. Special attention is paid to the case when the wanted parameters are hard to measure directly. Numerical examples are presented dealing with 5-link mechanism used to guide front wheels of a car.

The article presents the issue of calibration and verification of an original module, which is a part of the robotic turbojet engines elements processing station. The task of the module is to measure turbojet engine compressor blades geometric parameters. These type of devices are used in the automotive and the machine industry, but here we present their application in the aviation industry. The article presents the idea of the module, operation algorithm and communication structure with elements of a robot station. The module uses Keyence GT2-A32 contact sensors. The presented information has an application nature. Functioning of the module and the developed algorithm has been tested, the obtained results are satisfactory and ensure sufficient process accuracy. Other station elements include a robot with force control, elements connected to grinding such as electrospindles, and security systems.