The investigation presented in this work concerned one-dimensional modelling of transient flow in an axial turbine stage. Because of the compound motion in the rotor-blade channels, the model of this flow path element was considered the most difficult to solve. The basic modelling approaches and the usefulness of the Euler and Lagrange methods for mathematical description are discussed. Relevant applied model based on the Lagrange method is described. Results of a successful numerical simulation of transient flow in a turbine stage are presented. This success opens the opportunity to build and solve one-dimensional models of dynamic flows in turbine cascades and entire flow paths.

The paper is devoted to a bolted flanged joint with a flat ring gasket. Simple mathematical models of the flat ring gasket and the flange are formulated. Solutions to the models allowed determining numerically effective shapes of the flat ring and the flange. In the case of the gasket a minimal tension of the bolts was assumed as a criterion, while in the case of the flange the criterion of minimal angle of the flange rotation was applied. Results of the study, shown in the Figures, may serve for practical purposes in designing of pressure vessels and piping.

One of the worst accidents that can take place in industrial presses is related to the risk of generating cracks in the columns. In order to avoid press columns from being subjected to tensile stress in the loading phase, the columns are sometimes assembled precompressed, so that nominal stress maintains negative values throughout the work cycle. Previous researches have considered cracks propagating under cyclic compressive loads in notched specimens. In these cases, the fatigue cracks are initiated at the notch root due to residual tensile stresses and grew at a progressively decreasing speed before arresting. The subject of the present paper is to give a paradigmatic example of crack initiation and propagation also in a general compressive field.

The paper presents the algorithms for kinematic analysis, trajectory planning, dynamics of kinematic chain and driving units elaborated for manipulators and robots with kinematic chains of serial structure with revolute pairs with perpendicular or parallel axes. Elastic deflections of driving units as well as action of external forces on end-effector have been taken into account. The simulating software was created using the modular structure of modeling process. The application of software for testing the robots accuracy and running speed acc. to ISO 9283 is also presented.

The paper presents modelling proposal of the curvilinear scraper arm geometry by means of Bezier' s curve of the third degree. A physical model of scraping process of the unit load with the use of curvilinear arm for the most difficult sorting cases has been worked out. As a result of the performed numerical optimisation, there has been proposed the scraper arm shape geometry that makes it possible to decrease dynamic interaction exerted on the sorted loads.

Finite element simulations of structures and structural details require suitable material models. Today there is still a lack of such constitutive material models in timber engineering. Therefore, a perennial research project at the Institute for Mechanics of Materials and Structures at the Vienna University of Technology was performed. In this paper the testing equipment, the experiments, the developed material model and its implementation in finite element software will be explained. One focus of the mentioned project is the acquisition of the mechanical behaviour of biaxially, oblique to fibre direction loaded spruce wood. This enables a better simulation of multiaxial stress states in real timber structures. The applicability of the implemented constitutive model will be demonstrated by means of a nonlinear finite element analysis of a bone-shaped test specimen.

The application of tuned liquid column dampers (TLCD) for suppressing excessive lateral pedestrian-induced vibrations of footbridges is investigated experimentally and numerically. In order to study the effectiveness of TLCD, a novel three-degree-of-freedom (DOF) bridge model is constructed in the laboratory of the TU-Institute. A single TLCD is attached to the bridge model to counteract the bridge's fundamental vibration mode. Modal tuning of the TLCD is performed using an analogy to tuned mass damper (TMD). A new excitation device has been developed for simulating the time-periodic contact forces due to walking pedestrians. All vibration tests performed indicate a large reduction of the maximum lateral vibration response amplitude. In order to verify the experimental results, numerical simulations of the laboratory model are performed, which show a good agreement. The application ofTLCD at least doubles the effective modal damping coefficient when compared to the original bridge model.

Two semi-circular rods set up in V-shape form were used to generate streamwise vortices in a turbulent boundary layer. The vortices, due to induced helical flow, supplement the streamwise momentum of retarded air particles at the body surface with the momentum of the external flow. In this experimental study it was found that vortices are at their most intensity if the Reynolds number of the flow over generator, based on the diameter of rods is within the range I 04-1.5 · I 04 • Several semi-circular rods set up in a tooth line were examined in delaying the separation of the turbulent boundary layer at a convex cylindrical surface. It has been noted that delay of separation is at its most efficient when the height of the generator is equal to at least half of the boundary layer thickness.

Two different principles of TMF-testing were investigated for the wrought aluminium alloy AlCuBiPb (201 I). In the first testing method the specimens are clamped in a stiff load frame. A cyclic temperature load is applied, which leads to an out-of-phase (OP) TMF loading. The local strain is measured within the parallel cross section of the specimen. The second series of OP-TMF tests are conducted using closed loop strain control on a servo-hydraulic TMF testing system, which guarantees a rigid restraint condition within the parallel section of the specimen. To compare these two principles of TMF-testing, additional experiments were conducted with different mechanical strain amplitudes. The two experiments can be compared well, when the local strains are taken into account. Therefore, the method of the rigid clamped specimen can be used to get experimental data in a wide range of strain amplitudes.

Deflection of balancing disc in a multistage centrifugal pump, being the consequence of pressure forces, causes the change of shape of the axial clearance between the rotating balancing disc and the stationary counterdisc. It results in reduction of axial force acting on the rotating wall of the clearance, and the total balancing force. The final effect is a significant decrease (e.g. of 20%) of disc to counterdisc distance. The approximate formulae for radial pressure distribution in turbulent flow through hydraulically smooth conical axial clearance are derived in the paper and a numerical example is given. The method of integral relations was applied.

The strip yield model from the NASGRO computer software has been applied to predict fatigue crack growth in two different aircraft aluminium alloys under constant amplitude loading and programmed and random variable amplitude load histories. The computation options realized included either of the two different strip yield model implementations available in NASGRO and two types of the input material data description. The model performance has been evaluated based on comparisons between the predicted and observed results. It is concluded that altogether unsatisfactory prediction quality stems from an inadequate constraint factor conception incorporated in the NASGRO models.

The paper discusses the problem of the accuracy of the identification techniques detecting cracks and corroded members in vibrating beam and frame structures. The presence of the fatigue crack usually causes very small changes of the stiffness of the beam elements of the structure. To detect these changes it is necessary to apply the most precisely mathematical detection technique. The identification procedure based on the least squares technique uses finite element models (FEM) of the structure and as the source of information the measured dynamic response and the natural frequencies. The application of the Dynamic Stiffness Matrix (DSM) [I) for the representation of all constraints and modal equations makes it possible to present the identification process in a very accurate and efficient mathematical form. The methoyof d of the detection of structural changes used in the present paper was described in our previous paper (2). The Consistent Mass Matrices (CMM) and Lump Mass Matrices (LMM) are very often used in the identification algorithms. It is shown that application of simplified approaches (CMM and LMM) can result in lower accuracy and poorer convergence of the identification algorithms. However, the application ofCMM mass matrices does not introduce significant errors. The algorithms were tested on simulated numerical data for ten element beam frames.

The objective of this paper is to present a method of dynamic analysis of the steering system of a passenger car with McPherson suspension. The links of the system are modelled as rigid bodies; however, the method enables flexibility of the steering shaft of the car to be taken into account. The geometry of the system is described by using homogenous transformations. Equations of motion are derived on the basis of the Lagrange equations. In the method proposed, the closed loop oflinks is cut at selected joints and suitable reaction forces are introduced. Dry friction occurring in the steering system is reduced to the prismatic joint between the steering rack and guide. The method can be used in design and optimization of steering systems of passenger cars with McPherson suspension.

The authors present the results of experimental rig study on resistance forces in a rack and pinion steering system without power assistance of a small car with MacPherson front suspension. The influence of a harmonic steering angle excitation, with frequency ranging from I to 3 Hz, and different wheel load conditions on self-returnability, sensitivity, and friction forces in the steering system is studied. These characteristics are responsible for the car directional stability at high-speed of cruising or during braking maneuver, and influence comfort, effort, and good feeling of the car driver. On the basis of experimental results, some parameters (equivalent moment of friction forces and stiffness coefficients) of a simplified model are estimated for different excitations and load conditions.

The paper describes a mathematical model of gas flow through crevices between the piston, rings and cylinder in internal combustion engines. The model has been developed to study the influence of numerous. design parameters and engine operation condition on piston ring pack behaviour and the exhaust gases blowby from the combustion chamber to the crankcase. The model integrates the gas flow and axial rings displacements in the grooves, and separately treats lands between piston, cylinder and adjacent rings and regions in the grooves behind the rings. The heat transfer between the gas and the surrounding surfaces is calculated and emphasis is placed on considering the influence of wear and thermal deformations of elements on ring pack performance.

The paper presents a study of Rotary Electrical Discharge Machining (REDM) process. In REDM, simple shaped cylindrical electrodes are used to generate 3D complex shapes. A theoretical model of machining process is described, which takes into consideration the effect of tool electrode wear on machined surface profile. The software for computer simulation of REDM has been developed. In the paper, the effects of machining parameters on shape error of machined surface are discussed. Results of computer simulation have been confirmed in experimental practice. The simulation model for NC contouring REDM may also be applied to solving numerical control problems and optimization of tool electrode path.

The article presents criterion of evaluating energy consumption of water pumping. The lower slope of pump efficiency characteristic curve was plotted for the case of: constant gain of rotational speed and variable gain of rotational speed. The unified form of the lower slope of pump efficiency characteristic curve was defined for variable head. The right-side coefficient of pump efficiency correction was defined.

This paper presents a study of the damping of nonlinear vibrations in a two-mass model of mechanical system containing a torsion damper. The starting of the system by harmonic excitation is considered on the assumption of uniformly varying frequency and constant amplitude of the forced moment. Simultaneous structural friction phenomena (passive damping) and piezoelectric effect (active damping) have been considered as well. The problem is considered on the assumption of a uniform unit pressure distribution between the contacting surfaces of friction discs and plunger. The aim of the analysis is to asses the influence of angular acceleration, unitary pressure, external load and electric parameters on the resonance curves of the starting vibrations. The equations of motion of the tested system were solved by means of the Krylov-Bogolubov-Mitropolski method and digital simulation method.

The paper presents the numerical model of a supply vessel-load-crane-offshore vessel system for simulation of heave motion and dynamic analysis of the system during critical phases of the handling operation: taking the load off from and lowering it to a moving base. The model enables extreme forces in elements and deflection of the structure to be determined. Different operating and emergency conditions can be simulated (e.g. horizontal motion of a supply vessel). The elaborated software can be applied also for determination of derated load charts and ultimate crane capacity (sequence of failure).

The work presents characteristics of the pressure pulsation of the paper stock flowing through its approach system to the paper machine headbox and through the headbox. Theoretical model of the pulsating flow of the stock in the pipelines is described and conditions are suggested for the pipeline system to avoid creation of the wavy resonance. The relationships have been developed determining the effect of the pressure pulsation of the stock on its distribution on a surface of paper web being formed on the paper machine wire. Analysis of these relationships enables proper selection of the damping means of the pressure pulsation of the stock being delivered on the paper machine wire.

The paper presents methodology for calculating optimal drive torques which ensure reduced or minimal fuel consumption and emission of toxic components of exhaust gas during acceleration of a car. Data for fuel consumption and toxic emission in dynamic conditions (for a run with changeable speed) are obtained using experimental measurements during typical drive tests. A dynamic optimization problem for calculating a drive torque has been formulated using dynamic characteristics and a simple mat hematical model a vehicle when travelling in a straight line. The optimization problem has been solved for a drive with petrol and LPG. Results of numerical calculations followed by conclusions are presented.

The authors present a concept of constructing the equations of motion for a single-bucket pulling excavator in terms of generalised Lagrange's variables. The applied model is based on the assumption that the excavator is a system of rigid solids connected with rotational constrains of ten degrees of freedom. The essence of the proposed algorithm consists in reducing the procedure of constructing the system of excavator's motion equations to multiplication of adequate matrices. One avoids analytical or numerical derivation of the consecutive time derivatives of kinetic and potential energy of the system. The algorithm formulated in such a way may constitute a basis for constructing a numerical program for the analysis of excavator system dynamics. The proposed method of generation of Lagrange's equations can be generalised and applied to a wider class of multibody systems.