Cemented carbides are hard materials used in tough materials machining as well as in situations where other tools would wear away. These are one of the most successful composite engineering materials ever produced. The advantage of cemented carbides is that their structure and composition can be engineered to have properties tailored to specific applications and operations. These materials allow faster and more precise machining and will leave a better surface finish. Carbide tools can also withstand higher temperatures than standard high speed steel tools. Considering their application and known range of properties, main disadvantage of cemented carbides is appearance of their sudden fracture during machining process. This is caused by the low toughness at dynamic rates and overcoming this problem is yet to be researched further. In order to understand these limitations and provide suggestions for the improved design of the material, combined experimental and numerical analysis is currently being performed. Cohesive strength values numerically determined using Dugdale cohesive zone model are compared to flexural strength obtained experimentally. Reduction in flexural strength was then analysed and explained, relating it to the flaw size on the tensile surface of the specimen.

This work contains analysis of a dynamic vibration absorber with damping which is exposed to a nonperiodic complex form of excitation. In the beginning an analytical model of the dynamic absorber was developed. After that, the determination of systems main mass dynamics and the corresponding equations of motion for the simple case of harmonic excitation acting on the system were made. A FORTRAN program was developed that counts the basic movement of the mass of a system which is exposed to a non-periodic complex excitation and which is based on the application of Runge - Kutta and Newmark methods. Using this program we have made the necessary analysis and calculations.

Cemented carbides are one of the most successful composite engineering materials ever produced. Their unique combination of strength, hardness and toughness satisfies the most demanding applications. These materials have a unique combination of high hardness and good toughness within a wide range and thus constitute the most versatile hard materials group for engineering and tooling applications. After the fracture tests on notched cemented carbide specimens have been conducted and the relevant properties at initiation determined according to linear elastic fracture mechanics, an appropriate numerical model needs to be developed for the calibration of cohesive laws in order to reproduce the obtained experimental results. Finite volume modelling of three-point bend tests was performed and numerical results obtained. The impact speed and measured material properties were provided as input parameters, and the cohesive strength for each grade of material was determined across the range of loading rates used in the experiments at room temperature. The numerical simulations were compared to the experimental data and very good agreement was obtained, where the computed force-time curves lie very close to the

Vibrations analysis is important part of construction design and possible failure detection. Vibration highly depends on damping characteristics. Damping characteristics must be considered or determined experimentally, which is commonly done by analysis of vibration records. Determination of damping is important due that internal damping of elastic systems sometimes could be controlled to reduce amplitude of vibrations and increase a life of construction. In this paper, simulation of experimental damping determination of elastic systems is presented. Vibrations are simulated by numerical solution of mathematical model of damped vibrations of two d.o.f. system. Waveform obtained by simulation is imported in software for experimental data analysis and analysed as a real waveform. Damping analysis is performed in time domain and tested for different initial condition.

In this paper an analysis of influence of three type of damping on free vibration of elastic systems is presented. Linear viscous, nonlinear viscous and dry friction damping were considered. Special emphasis was on determining of critical damping value for all of three types of considered damping cases. Also, analysis of logarithmic decrement of amplitudes, evaluation and comparison logarithmic decrement for considered damping types is presented. For all types of damping, same features of system were used and then analysed. Since some of types of damping couldn’t be solved in closed form, numerical method was used. In this case, forth-order Runge-Kutta method is used for solving damping proportional to squared velocity of motion. Most important conclusion is that only system

Research of the behavior nonlinear mechanical systems enables finding of the possible states of system stability as well as analysis of stability and processes of system transition from one state of motion stability to another. In this paper, a procedure of energy balance is presented, for the purpose of making a mathematical model of self-excitation oscillations in the system with one degree of freedom and analysis of phase portraits, i.e. existence of stable states of motion for different initial conditions. The procedure was applied in modeling of self-excitation oscillations for high-speed milling and is based on determination of non-linear self-excitation force and non-linear coefficient. The mathematical model is made on the basis of experimentally acquired results that are basis for determination of real parameters of the system.

Mechanism with rotational cam and rotational bar has important application in technique. In target of regular work of this mechanism, contact between plate bar and cam must be provided, in other words, force between cam and bar must exist. For satisfaction this conditions, we often use elastic elements (springs). This paper presents analysis of influential parameters on this conditions.

Flat-faced follower is mechanism with rotational cam and with plate bar. It has important application in technics (motors, tool machines etc.). In target of contact of plate bar and cam in only one point, it is need that profile of cam would be convex on all length. This paper presents analysis of influence of single parameters of motion of this mechanism on value of minimal radius of basic circle of cam,

This study analyses the possibility of applying the Thin Sections Method for calculation for extrusion pressure for combined forward-backward extrusion. It also deals with the possibility of increasing the accuracy of the method. By using this method it is possible to obtain data concerning the pressure distribution along the punch face. The results have been tested experimentally.

This paper presents a comparison of critical loads for trusses, calculated by linear and nonlinear stability analysis. Analyses are provided by using finite elements method. In linear case, critical load is extracted from derived algebraic eigenvalue problem. In case of nonlinear analysis, critical load is determined by construction of postbuckling equilibrium path. Numerical examples for characteristics trusses are given. It is shown that in the case of some perfect trusses, linear approach may produce significant error in the calculation of critical load, and nonlinear analysis should be introduced. The conclusions about conditions for using linear and nonlinear approach to critical load calculation for trusses are derived. 1. INTRODUCTION Stability analysis of engineering constructions requires calculation of buckling load and corresponding buckling shape. Stability problems are almost simplified by neglecting pre-buckling deformation, and considering construction with no imperfection (perfectly straight beams, etc.). This assumptions enables deriving eigenvalue problem, which solutions are critical (buckling) load and corresponding buckling shape. It is known that in case of beam stability analysis, these assumptions are correct and theoretical value of buckling load, if imperfections are sufficiently small, may be in practice closely obtained [1,2]. In case of beams, axial deformation does not change straight-line state of the beam, but, in case of some perfect trusses, prebuckling deformation may change distribution of forces in constitutive bars, and also acts as imperfection. Truss-like structures are widely used as load bearing structures, because of their relatively high stiffness related to low mass. In this paper is considered problem of calculation of critical load of truss structure. Both linear and nonlinear calculation is done using finite element method. Linear stability analysis is provided by solving linear algebraic eigenvalue problem, which derivation is also presented. In linear approach, prebuckling deformations are neglected. Nonlinear analysis is performed using linear expressions for constitutive matrices in equilibrium equation. Because of possible large displacements, analysis is done iteratively, checking does equilibrium of forces at every node is satisfied. Residual forces are used as additional nodal forces, until it reaches sufficiently small value. On this approach to nonlinear analysis, prebuckling deformation are taken into account. Results are compared for the specific two bar truss, commonly used in demonstration of numerical methods [5]. It is shown that in case of trusses, linear approach may lead to large overestimation of critical load, and that control of results using nonlinear analysis should be done.