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Number of results: 24
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Abstract

The author presents an algorithm of slewing motion control in telescopic crane mounted on a chassis of a truck (mobile crane). The control algorithm allows the crane to carry load to a selected point, and it also ensures suppression of swing at the endpoint of the motion. The attention was focussed mainly on the control of slewing motion of the crane body in the case of non-planar distribution of forces acting on the load during its motion.
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Authors and Affiliations

Jacek Kłosiński
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Abstract

Because of clear trend in the world to design lighter plastic products, the phenomenon of creep buckling of visco-elastic solids becomes increasingly important. This paper reports the intermediate results of the research project on loading capability and buckling of plastic containers, carried out in the Laboratory of Mechanical Reliability (LMB) of TU Delft. Based on the earlier developed non-linear visco-elasticity model for engineering plastics, the FE simulation of the delayed in time buckling of plastic strips have been performed as a first step toward the understanding and predicting creepbuckling behaviour of plastic carriers.
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Authors and Affiliations

Jan L. Spoormaker
Ihor D. Skrypnyk
Taras O. Yasylkevych
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Abstract

The paper presents comparative analysis of the results of low- cycle fatigue experiments on specimens made of 45 steel under uniaxial loading and bending. The analysis involves, among other things, the cyclic properties and the fatigue life of the specimens in a wide range of loading conditions. The experimental techniques used during bending enabled us to estimate the influence of strain distribution on fatigue life. The materials data obtained under the loading conditions mentioned above were employed to estimate the fatigue life of the structural elements. The results of experiments and calculations are presented in the form of fatigue curves. They also show the influence of axial loading and bending on the accuracy of the calculations.
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Authors and Affiliations

Stanisław Mroziński
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Abstract

The helical flow is generated by a jet from a single nozzle inflowing tangentially into a pipe. The effect of the distance travelled by the air in the pipe from its tangential inlet to its axial outlet on the issuing jet is investigated. The axial and tangential velocity distributions were measured at the outlet cross-section of the pipe using the hot-wire probe. It was observed that for a short pipe the strongest asymmetry of the tlow velocity distributions exists for a part of the pipe crosssection near the pipe wall. Contrary to this, for a long pipe, the largest deviations from axisymmetry appear in the middle part. In this result the total effect of asymmetry expressed by RMS of swirl number considerably decreases.
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Authors and Affiliations

Jan Wojciechowski
Andrzej Szumowski
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Abstract

Effects of specimen thickness and stress ratio on fatigue crack growth and crack closure levels under constant amplitude loading and after a single overload have been studied experimentally for a structural steel ( I 8G2A). The corresponding crack growth data from the fatigue tests have been presented and evaluated. The experimental trends have been compared to those reported in the literature for various steels. The ability of the effective stress intensity factor range based on crack closure measurements to correlate the observed crack growth response has been investigated.
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Authors and Affiliations

Małgorzata Skorupa
Andrzej Skorupa
Jaap Schijve
Tomasz Machniewicz
Paweł Korbut
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Abstract

Helical Jet in moving air was used to simulate the flow downstream of a helicopter blade tip or a wing tip. The jet was generated by means of an opened pipe supplied tangentially (tangential nozzle), and placed in a wind tunnel. Flow properties were investigated in several cross-sections downstream of the nozzle. The flow direction and the total pressure were measured in function of the azimuthal angle and the distance from the axis of the system. The flow was visualized using the planar laser scattering technique. The decay of swirl intensity was measured by means of a probe with a rotating plate fixed to a miniature voltage generator.
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Authors and Affiliations

Jan Wojciechowski
Andrzej Szumowski
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Abstract

The Authors present the problems of theoretical analysis and experimental research related to the possibilities of energy recovery in selected phases of operating and running cycles of self-driven crane. Heavy machinery powered by diesel engines is a source of solid toxic emissions. In order to limit these emissions, one install filters and filter regeneration systems. According to the concept presented here, the recovered energy might be utilised for regeneration of these filters by burning off accumulated solid particles (soot). Mechanical energy would be the power source to drive DC generators - the mechanical-into-electric energy converters. Filter's heating resistors, acting as the generators' load, would radiate a power of 3-;-5 MJ to initiate burning of soot in the filter. The calculations of energy consumed during sheave block lowering phase were made for three different lifting capacities taking into account the boom length and crane reach. Three running cycles of the crane: highroad, urban and off-road ones were also analysed. The time functions of variations of crane running speed and power of motion resistance at driving wheels were found. The results provided the background for determination of theoretical values of energy to be regained during braking phase of the analysed cycles. The structure and operation of experimental stands was discussed. The stands contain units that, at proper size factor, represent the processes that occur in real cranes and that are related only to energy recovery. Computer software for system simulation, control and measurement was described. Measurement results and result analysis are presented. The value of energy found theoretically was compared with the energy recovered during experimental tests. The paper also contains simplified kinematic schemes of selected units of crane lifting and driving systems, including an additional DC generator. This concept, however, needs verification in future design solutions.
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Authors and Affiliations

Jerzy Ocioszyński
Przemysław Majewski
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Abstract

The knowledge of performance characteristics of turbine stage groups is still insufficient, particularly in the general case of changes of operating conditions. This situation is caused mainly by the scarcity of experimental data available. In such case, the opportunity to obtain the required data, using mathematical modelling and numerical simulation of the operation of stage groups under off-design conditions instead of physical experiment, seems to be attractive. The application of this idea for impulse type turbine stage groups was presented in [I], [2]. Here we discuss similar results but obtained for reaction type turbine stage groups, that is: - mathematical model for computer simulation of operation of reaction type turbine stage group, under variable regime (based on Ainley's and Mathieson's method with some improvements); - simulation results for a number of stage groups designed according to former BBC and traditional concepts; - more general properties of these groups (in relation to flow capacity and efficiency) obtained from the analysis of simulation data; - comparison of observed properties of impulse and reaction typy turbine stage groups.
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Authors and Affiliations

Andrzej Miller
Janusz Lewandowski
Zofia Trzcińska
Kamal Ahmad Abed
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Abstract

The necessity of empirical determination of impact energy of hydraulic hammers prompted the Author to analyse the methods that had previously been used to determine this quantity. Based on the results of the analysis, the Author developed a new method of measurement of impact energy by means of force converter with an embedded elastic element, Taking into consideration the structural scheme and the principle of measurement, one derived analytical relationship that make it possible to calibrate the measuring system in energy units. A practical example of application of the developed system was in measurements of impact energy of hydraulic hammers used in Polish copper mining industry.
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Authors and Affiliations

Krzysztof Krauze
ORCID: ORCID
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Abstract

The residual stress analysis is discussed in the paper. However, the author has not intended to present, even partially, all aspects of this very broad problem. The aim of this work has been limited to a review of conternporarily used experimental, numerical and hybrid methods, and to outline the directions of possible developments.
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Authors and Affiliations

Marek Bijak-Żochowski
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Abstract

The paper concerns efficiency of active magnetic stabilization in damping of selfexcited vibration of an asymmetric rotor supported on 5-lobe journal bearings with 5 oil gaps. The dependencies describing the pressure distribution in the oil film are presented. The components of the hydrodynamic uplift forces in the bearings are described. Equations of motion are derived using a numerical simulation method. It was found that active magnetic stabilization was effective for symmetric and non-symmetric systems. Exemplary trajectories of the journal bearing motion as well as the time histories are presented.
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Authors and Affiliations

Zbigniew Starczewski
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Abstract

Brittle fracture of the reinforced composite element has been a matter of considerable concern to engineers for many years. It is now generally accepted that the mode of failure is the centerpiece of the problem. The publication presents the experimental and numerical procedure used to determine the state of' the stress in the photoelastic model of reinforced beams. The fracture process of fiber reinforced composite materials is very complicated, and the fracture strength is affected by: matrix cracking, fiber breakage and interfacial debonding between matrix and fibers. The criterion used to calculate the maximum load was derived based on two processes only: matrix cracking and deformation of the rei nforcerncnt. The theoretical ultimate bending moment was calculated using the strain energy release rate Ge and the stress intensity factors (K11 and K1) corresponding to the crack propagation of the matrix and the elastic-plastic deformation or the yield limit of the reinforcement.
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Authors and Affiliations

Mieczysław Jaroniek
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Abstract

Influence of magnetic field on parameters of normal detonation wave and cumulation process of cylindrical detonation wave in gaseous explosive mixture was examined. A review of applications of generalised Chester-Chisnell-Whitham (CCW) method used for analysis of implosion processes of detonation waves is presented.
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Authors and Affiliations

Jerzy Tyl
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Abstract

The essential problem in the process of technological prestressing is the imperfection of web sheets. These elements made of relatively large sheets (about 2 meters high) show significant imperfections of the shape and flatness. Initial deflections have the value equal several times the web thickness, but they tend to grow in the process of straightening. Such a case can particularly occur when stresses that compress the shield of the web sheet between diaphragms are close to the critical buckling stress. Experiments were carried out in a real object. The box girder having I I .Om span and 1.8 m in its height was prestressed by welding the straps on the bottom flange and on the web in the vicinity of the bottom llange. Results of performed investigations are the subject of the paper.
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Authors and Affiliations

Artur Blum
Tomasz Kubiak
ORCID: ORCID
Tadeusz Niezgodziński
Zbigniew Orłoś
Jacek Woliński
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Abstract

The paper discusses an occurrence or latent reactions in the direction perpendicular to the movement of the suspension systems in vibratory machines supported by parallel leaf springs. These reactions occur despite an apparent lack of any forces acting in that direction and may - for long machine bodies - reach values comparable with the exciting force of the vibrator. Analytical relationships allowing for estimation of the value of reactions were derived. The obtained results were verified by means of the Geometric Element Method as well as by the performed experiments.
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Authors and Affiliations

Jerzy Michalczyk
Piotr Czubak
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Abstract

The work presents cycle models of cylinder pressure and models of forces in crank-piston system based on a sample of experimental results. The models make it possible to determine the cycles in an arbitrary state of engine operation. Model limitations and the conditions for model applicability are also discussed. An example simulation of the processes is presented for well identified and verified models pertaining to the engine of Polonez 1,5 GU automobile. The method can also be applied to other types of engines after identification of the model parameters based on a sample of at least six indicator courses measured in different states of engine operation.
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Authors and Affiliations

Krzysztof Paweł Wituszyński
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Abstract

The main aim of this analysis is to consider a mutual interference between aircraft motion and surrounding flow field. Euler flow model for inviscid, compressible gas and aircraft flight dynamics model was used to analyse quick dynamic manoeuvres. For such manoeuvres, aerodynamic hysteresis has a great influence on aircraft dynamics, which cannot be simulated with the assumption of quasi-steady aerodynamics. On the other hand, the aircraft motion as a rigid body strongly influences the flow field around itself. To account for this mutual interference, the Euler flow equations were used to obtain aerodynamic forces and moments acting on a simplified aircraft configuration (main wing+ tailplane only) during pull-out manoeuvre, and the flight dynamics equations of motion were used to describe dynamics of an aircraft. Initial conditions for the flight dynamics equation of motion were settled up coming from the solution of the Euler flow model. As a test case, a weak pull-out manoeuvre was selected. During this manoeuvre, the highest value of angle of attack doesn't exceed 12 degrees - the value which can be obtained from the classical approach based on flight dynamics equations of motion with quasisteady aerodynamics. However, coupled Euler flight dynamic model has much wider applicability, and can be used for the analysis of manoeuvres at high angles of attack, including large scale separation at sharp edges, unsteadiness and flow asymmetries even for symmetrical undisturbed flowficld case. This method, if successfully verified to a number of important flight manoeuvres (such as spin, Cobra manoeuvre, roll at high angles of attack and other) can open a new, very promising field in the analysis of aircraft dynamics.
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Authors and Affiliations

Tomasz Iglewski
Zdobysław Goraj
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Abstract

The paper presents a general idea of the acceleration test method and the design, construction and testing of the inertial dynamorneter test rig developed for small, high performance two-stroke engines. The method is universal and can be also used for four-stroke engines but it is especially useful for the two-stroke ones. The testing procedure is described and the advantages of that type of investigation method are pointed out. It has been proved that the reliability of the method is satisfactory. It was also proven that the individual construction of the inertial dynamorneter of good quality can be performed individually and that it can be a very useful investigation tool in engine tuning practice. The point has been stressed that the major advantage of that method is the possibility of the instantaneous measurement of the engine power characteristic during unsteady engine operation (acceleration) where the time for the single run does not exceed ten seconds.
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Authors and Affiliations

Paweł Mazuro
Tadeusz Rychter
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Abstract

This article presents shortly reasons for improving designs of turboprop and turboshaft engines, and describes aero-thermodynamic aspects of methods or modification of these devices. The theoretical analysis of methods or modification concerns general changes or efficiency, flow, and rating. The influence of the following factors on engine performance is presented: change of efficiency or engine units, increase of compression and flow rate by using a compressor zerostage, change of compressor pressure ratio, changes of gas temperature keeping the gasgenerator rotational speed constant by adjusting the minimal throat area of turbine nozzle guide vanes, turbornachinery modelling, and changes of rotational speed of ratings.
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Authors and Affiliations

Stanisław Antas
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Abstract

The effect of large injection rates on the steady laminar compressible boundary layer in the front stagnation-point region of a rotating sphere with a magnetic field has been studied. The effect of variable gas properties, non-unity Prandtl number and viscous dissipation are included in the analysis. The nonlinear coupled ordinary differential equations governing the flow are first linearized using the quasilinearization technique, and the resulting system of linear equations are then solved using an implicit finite-difference scheme with non-uniform step size. For large injection rates, analytical expressions for the surface shear stresses in the longitudinal and rotating directions and the surface heat transfer are also obtained using an approximate method. For large injection rates, the surface heat transfer tends to zero, but the surface shear stresses in the longitudinal and rotating directions remain finite but small. The surface shear stresses and the surface heat transfer decrease with increasing rate of injection, but they increase with the magnetic field and the rotation parameter. The magnetic field or the rotation parameter induces an overshoot in the longitudinal velocity profile and the magnitude of the velocity overshoot increases significantly with the rotation parameters and the injection parameter. The location of the dividing streamline moves away from the boundary with increasing injection rate, but it moves towards the boundary with increasing magnetic and rotation parameters.
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Authors and Affiliations

Mahesh Kumari
Girishwar Nath
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Abstract

Dynamic stability analysis of the World Class Glider PW-5 has been presented. Glider was assumed to be a rigid body of three degrees of freedom - two linear displacements and one rotation - all in the plane of symmetry. Responses of the glider due to gust and deflection of elevator have been determined. The Laplace transform has been applied to convert the differential equations into algebraic ones. The transformed algebraic equations, after a number of manipulations have been solved for the output variables. Partial-fraction expansions have been performed to obtain the inverse Laplace transforms from the Laplace transform table. Although some restricting assumptions have been made (rigid body, small disturbances) the presented results are original and have not been presented before. The airworthiness regulations (JAR, FAR) do not require performing dynamic analysis in order the glider to be granted a Certificate of Airworthiness by the national aviation authority. To certificate the glider it is sufficient to prove static stability by means of in-flight tests. Flying qualities are qualitatively estimated basing on subjective opinions of the test pilots
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Authors and Affiliations

Zdobysław Goraj
Adam Przekop
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Abstract

In this work, the author implements concepts and methods of analysis of nonlinear elasticity theory in a simplified description of elastic-plastic properties of materials. Taking the principle of conservation of energy as the theoretical basis, the author formulates a criterion that makes it possible to examine the stability of internal equilibrium in deformed material whose nonlinear properties are defined by strain energy density function. The formulae allowing for assessment of complex states of strain in the aspect of material strength were derived on the assumption of small deformation. These formulae can replace mathematical relationships traditionally known as strength hypotheses. The example included in the paper presents the method of determining, in the space of strain state components, the areas where permanent deformation or destruction of material is possible because of strain state stability. Characteristic parameters used in the example are obtained in a static tensile test on specimen 01· constructional carbon steel of ordinary grade. The results of the analysis, based on the formulated strength hypothesis on stability of strain state, are compared with those resulting from the Huber's hypothesis on energy of non-dilatational strain.
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Authors and Affiliations

Tadeusz Michał Wegner
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Abstract

In the paper, a new model of friction coupling in rolling friction is presented. Apart from slips related to elastic and plastic deformation in the area of actual contact of two bodies, the mechanism includes also inertia forces related to tangential deformations. Research concerning a model of coupling mechanism of variable ratio friction wheels is described. The main objective or the investigation was to prove that the force acting along the contact line of friction wheels is significantly affected by the shape of the contact area which had not been taken into account in the relations applied so far. A new model of the coupling mechanism was suggested and verified experimentally.
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Authors and Affiliations

Czesław Koziarski

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