Over thousands of years, amber has been used for decoration and as a kind of currency, magical substance, and medical cure. Coveted to this very day, amber has now become more than just a pretty stone - it holds sensational secrets for biologists.

The paper presents a plane model of articulated vehicles worked out for the analysis of their dynamics. The dAlambert principle was used for derivation of motion equations for this system. The forces and moments acting on wheels were formulated on the basis of the Dugoff-Uffelmann tyre model. The system consists of any number of vehicles connected by kinematic pair of the 5th class (non friction joint of pivot-bush type) and the fifth wheel (with dry fricton). Since crash calculations usually take into account the impulse of crash force only, and since it is not appropriate for articulated vehicles, a new approach to crash calculation is presented in this paper. The authors propose to calculate the force in crash point both as a function of the relative velocity of vehicles and the stiffness of their bodies. Simulation results of articulated lorry crashes and the attempt to verify the performed simulation are presented in the article.

For an impact fracture test, the influence of Coulomb friction between the specimen and anvil on contact forces and dynamic stress intensity factor (DSIF) has been investigated numerically. It has been shown that friction leads to increasing of the mean tup and anvil forces and decreasing of mean DSIF. Additionally, in most cases, friction leads to increasing of the amplitude of DSIF oscillations and, in consequence, makes interpretation of the test results more complex. Simple formulae for correction of reduced by friction mean DSIF values have been proposed.

Fatigue crack growth for 2024-T3 Alclad aluminium alloy sheet being subjected to two load programs: a constant stress amplitude cyclic tension (R=O. l) (CA) and a variable amplitude tension with either a single or multiple overloads (OVL) periodically repeated is analysed in the paper. The latter load program corresponds to a simple flight simulation spectrum of wing structure of civil aircraft. The investigation was developed in order to learn about interaction between the applied load and formation of fatigue striations. Experimental results of surface crack growth rate provided by optical observations were compared with the rate determined on the basis of microfracture analysis. Good correspondence found under CA loading between the surface growth rate and the growth rate in the sheet depth means that the direction of specimen's cutting does not change essentially the crack growth behaviour. In the case of second loading (OVL) this factor influences the crack growth behaviour. Microfracture analysis revealed either retardation and acceleration of crack growth rate under OL V loading. This behaviour of growth rate results from a plastic zone formed in the front of crack tip and a crack closure effect.

The critical plane orientations determined with account for maximum value of energy density parameters and the weight function method were compared to experimental fatigue fracture plane orientations. Energy density parameters used in two multiaxial fatigue failure criteria, i.e. (i) criterion of the maximum normal strain energy density on the critical plane and (ii) criterion of the maximum shear strain energy density on the critical plane were employed. In the other method, the weight functions were formed on the basis of energy parameters. These two methods were verified by experimental tests of 1802A steel. The material was subjected to cyclic and random bending, torsion and combined bending with torsion with different coefficients of cross correlation between normal and shear stresses. The calculated results are satisfactory for both methods.

The usefulness of elastic compliance measurements to estimate crack closure in structural steel and the validity of the assumption of a constant compliance value for the fully open crack is examined. Based on considering different issues related to the experimental technique and compliance data processing, local compliance measurements and the compliance offset method recommended by the ASTM standard are selected to be most suitable for structural steel. The compliance data generated in fatigue tests on I 8G2A steel conducted under a variety of loading conditions enabled to choose an optimal strain gauge positioning and appropriate offset criterion values for the original compliance offset method and its modified (normalized) version. The adequacy of the closure measurements is assessed through checking the ability of the resulting effective stress intensity factors to account for the observed effects of the loading conditions on fatigue crack growth rates.

The combined fractographic and simple stress analysis showed that there are several mechanisms responsible for a relatively high delamination resistance of laminates reinforced with fabrics. It was concluded that they result from yarn weaves and curvatures produced in the course of weaving.

The authors present the part of research devoted to the "squat" -type crack development in the heads of railway rails. This paper contains description of the results of investigations of the influence of the dynamic interaction, between the railway bogie running along the track on the "squat't-type crack development. The studies are performed by the use of computer simulation technique. The study is divided into two parts. The first part explains, how the vertical displacement of the wheel varies during the quasi-static rolling of the bo gie wheel along the cracked rail. In the second part of the paper, this displacements fluctuation is introduced to dynamic analysis. The histories of the wheel-rail force fluctuation during passage along the rail with the "squat'l-type crack were obtained as the result of dynamic analysis.

The paper presents computer application of the mathematical model of piston- ring-cylinder packing, which was described in detail in the first part of the paper. Methodology of selection of the input data, results of primary calculations and the method of model verification are also shown. The results allow acknowledging the mathematical model as verified.

Fatigue cracks in machine components are subjected to stress fields induced by the external load and residual stresses resulting from the surface treatment. Stress fields in such cases are characterized by non-uniform distributions and handbook stress intensity factor solutions for such configurations are not available. The method presented below is based on the generalized weight function technique enabling the stress intensity factors to be calculated for any Mode I loading applied to arbitrary planar convex crack. The method is particularly suitable for modeling fatigue crack growth in presence of complex stress fields.

The paper presents a method for dimensional synthesis of a five-rod guiding mechanism for the front wheels of a car. The goal is to find some unknown coordinates of joint centers of three suspension rods on the basis of given input data describing selected coordinates of other points, rods lengths and desired suspension characteristics for jounce-rebound and steering displacements. The synthesis problem is formulated as a single-criteria optimization procedure with a few substages solved in hierarchical order. The procedures for position and displacement analysis of the spatial multilink mechanism and for determination of the screw axes are also described. A numerical example for the AUDI A4 front ax.le is given.

The paper presents the most frequently encountered types and mechanism of damage of turbines' flow elements. The methods used nowadays for diagnosis of the damage are presented. A new possibility of localisation of damaged areas of turbine blades based upon the analysis of isotherm layout is proposed.

The paper presents the results of experimental investigations into variations of the stress tensor components due to both the interaction between subsurface fatigue crack faces and rolling contact. The load assumed represents real interaction between the railway wheel and rail. The Grating Holographic Interferometry (GHI) method was employed. The results obtained were compared with those resulting from numerical simulations performed using FEM. The results reveal a strong influence exerted by shape, crack thickness distribution and roughness of the crack faces, respectively, on the distribution of displacement and stress tensor component fields. A new concept consisting in application of the effective crack thickness was proposed. The best agreement between experimental and numerical results was achieved in the case when the real crack shape, effective crack thickness and the friction coefficient of 0.3 were assumed.

In the paper, the assessment of safety of the pipelines elements from the heat and power generating plants of Ukraine made of l 2Kh I MF steel has been presented. The SINT AP procedures for failure assessment have been performed assuming two shapes of hypothetical cracks along the straight segments of pipeline. The thermal stresses during the cooling process have been taken into account in the analysis. The analysis has been performed at the first level of SINT AP procedures. Two stages: a) before pipeline operation and b) after 156000 hours of service work have been analyzed. The comparison of results obtained by other assessment method has been made.

This study presents a forming configuration being an original three-dimensional geometrical model of forming dough pieces into spherical forms. Based on the forming configuration, the description of motion for a formed dough piece was made according to the principles of motion of a rigid body. Kinematic relationships concerning the dough piece material as a rheological fluid were formulated in accordance with the laws of fluid mechanics. Next, the relationships between the kinematic quantities present in both descriptions were defined. Presented in the assumed forming configuration (spherical coordinate system), the components of the deformation velocity tensor describe the velocity distribution over the surface of the formed and deformed dough piece. Determined kinematic quantities, as well as the relationships defined between them, describe the kinematics of forming dough pieces, and can be used to provide a dynamic description of the process of fanning dough pieces into spherical forms.

For reasons of reliability, stability, safety and economy, controlling and monitoring the response of structures during the time of use, either permanently or temporally, is of increasing importance. Experimental methods enable in-situ measuring deformations of any kind of structures and enable drawing conclusions over the actual state of the structures. However, to obtain reliable knowledge of the real internal conditions like the strength of materials and the actual stress-state, as well as of their changes over time, caused by ageing, fatigue and environmental influences, always an inverse problem must be solved. That requires special mathematical algorithms. Especially for time-depending material response it might be quite important to know the material parameters at any time and furthermore the internal stress-state also. Therefore, a method will be presented to solve the inverse problem of parameter identification with reference to linear visco-elastic materials.

Experimental evaluations on interlaminar and intralaminar fracture of multilayered and sandwich epoxy and polyester fabrics show an interesting behaviour at delamination initiation and crack propagation. Mode I and Mode Il tests were done on layered specimens with same type of ani ficial delamination to investigate the material influence on interlaminar fracture toughness and crack propagation. In sandwich specimens with a rigid foam core, the intralaminar damage failure and propagation are monitored.

One of important resistance parameters introduced into engineering calculations for selection of materials and evaluation of their operating properties is material crack resistance. Contrary to the stationary fracture toughness K1c, J," the dynamic fracture toughness K,d, J,d, ~ is also an important parameter. In this paper, the authors have evaluated the relation between the parameters of the dynamical fractures toughness and the structure as well as impact resistance in chosen frictionally welded joints. The above-mentioned joints are made of the following steel parts: N9E-45, 18G2A-St3S, St3S-45, 40H-45, 18G2A-40H. In this experiment, the instrumented bending impact test was used.

The subject of this paper is a new procedure applied for more precise determination of material fatigue characteristics. The proposed approach is based on a special definition of the strain energy density parameter used for material fatigue property descriptions and, in the consequence, on the new algorithm of the fatigue machine control in the feedback loop. On the basis of fatigue tests under uniaxial tension-compression with the strain energy density parameter control it was proved that the fatigue characteristics in energy approach (Wa - N1) determined directly from the tests and indirectly from the Manson-Coffin relation (E,, - Nj) with the strain control for material showing cyclic stability are similar. However, for material cyclic hardening these characteristics differ significantly in high cycle fatigue regime.

In the paper, the authors present a mathematical and numerical model of two-dimensional electrolyte flow in an interelectrode gap. Computer software for flow simulation with the possibility of visualization of distribution of physical conditions during process has been elaborated. The proposed mathematical model of electrolyte flow was verified experimentally by comparing real profiles of machined surface with profiles obtained in computer simulation. For this purpose there was examined a case of machining with a vibrating electrode and without vibrations.

The characteristics of the free gas jet, during its interaction with an upstream moving shock, were investigated experimentally. The initial strength of the shock remained constant and equal to M, = 1.34 whereas the Mach number of the free gas jet M, varied in a wide range of sub- and transonic values from M, = O up to M, = 1.4. It is shown that in the presence of the moving shock the jet characteristic becomes strongly modified. Outside the jet originates a cluster of pressure waves which moves upstream in jet surrounding. Spatial and frequency characteristics, as well as the number of pressure waves in the cluster, depend on the shock amplitude and the exit velocity of the free gas jet.