Zuzana Murčinková

Method of Continuous Source Functions for Modelling of Matrix Reinforced by Finite Fibres

Fibres are the most effective reinforcing material. Simulation of the interaction of matrix with fibres and fibre with other fibres is a most important problem for understanding the behaviour of fibre-reinforced composites (FRC). Large gradients in all displacement, stress and strain fields and their correct simulation for near and far field action are essential for effective computational modelling. Because of the large aspect ratios in fibre type reinforcing particles, methods using volume discretization are not efficient. Source functions (forces, dipoles, dislocations) describe correctly both near and far field activities and thus help to simulate all interactions very precisely. The method of continuous source functions allows us to satisfy the continuity of fields between very stiff fibres and much more flexible matrix by 1D continuous functions along the fibre axis and local 2D functions in the end parts of a fibre with only few parameters. Two types of examples with rows of non-overlapping sheets of fibre and with overlapping fibres show that the interaction of the end parts of fibres is crucial for evaluation of the mutual interaction of fibres in the composite. Correct simulation of all parts is important for evaluation of stiffness and strength of the FRC.

Temperature Fields in Short Fibre Composites

The paper deals with computational models for temperature fields in short fibre composites reinforced by very large aspect ratio fibres. Method of Continuous Source Functions (MCSF) is used for simulation of temperature fields. MCSF is a boundary meshless method reducing the problem considerably. In MCSF the continuity conditions of temperature fields, expressed in collocation (discrete) points of the fibre-matrix interface, are used to compute intensities of continuous source functions of heat sources and heat dipoles located along the fibre axis. Because of large gradients in the intensities of source functions, the NURBS were chosen to define the distribution. Number of unknown intensities is usually much smaller than the number of collocation points and the system of resulting equations is solved in the Least Square (LS) sense. Examples of computational simulations for single fibre, two fibres and regularly distributed fibres in a matrix are presented.

Thermal Properties of Short Fibre Composites Modeled by Meshless Method

Computational model using continuous source functions along the fibre axis is presented for simulation of temperature/heat flux in composites reinforced by short fibres with large aspect ratio. The aspect ratio of short fibres reinforcing composite material is often as large as 103 : 1–106 : 1, or even larger. 1D continuous source functions enable simulating the interaction of each fibre with the matrix and also with other fibres. The developed method of continuous source functions is a boundary meshless method reducing the problem considerably comparing to other methods like FEM, BEM, meshless methods, or fast multipole BEM formulation.

Implementation of Intelligent Elements in Vibration Diagnostics of CNC Machines

The paper deals with system of global monitoring in technological systems through the use of artificial intelligence elements. The holons and agents are the artificial intelligence elements that can be used for creation of systems for active and continuous control of active members of technological equipments.

Material Damping of Fibrous Composites for Devices Driven by Artificial Muscles

The paper dealt with material damping of fibrous composites for devices driven by artificial muscles as non-conventional driver. The composite material is intended mainly for rehabilitation devices, as well as for human artificial limbs, exoskeletons etc. The manipulator (rehabilitation) devices have potential to find usage in different periods of human life. Material properties of composites are suitable for applications with dynamic load, especially for their weight and material damping. On the base of experimental measuring, the material damping of several materials is analyzed.

Computational Simulation Methods for Composites Reinforced by Fibres

Trefftz-FEM (T-FEM), Adaptive Cross Approximation BEM (ACA BEM) and Method of Continuous Source Functions (MCSF) are presented for simulation of Composites Reinforced by Short Fibres (CRSF) with the aim to show possibilities of reduction the problem of complicated and important interac- tions in such composite materials. Fibres are the most effective reinforcing material. Outstanding mechanical, ther- mal and electro-mechanical properties of Carbon Nano-Tubes (CNT), carbon fi- bres and some other fibres are well known. Composites Reinforced by Short Fi- bres/tubes (CRSF) are often defined to be materials of future with excellent elec- tro-thermo-mechanical (ETM) properties. Understanding the behaviour of such composite materials is essential for structural design. Computational simulations play an important role in this process. Usually, strength, stiffness, thermal and electrical conduction of fibres are much larger than those of the matrix material. Very large is also the aspect ratio of the short fibres. Because of these properties very large gradients are localized in all ETM fields along the fibres and in the ma- trix. The fields define the interaction of the fibres with the matrix, with the other fibres, with the boundaries of the domain/structure. Accurate computational simu- lation of the fields is important for correct assessment of the material behaviour. ∗

Research and analysis of stress distribution in multilayers of coated tools

Abstract The paper analyses stress distribution in mono/multi-layers of coated tools. It presents an analysis performed on mono-layer, double-layer and multi-layer coatings using numerical models to detect the developed stress distribution and the most stressed zones in these mostly 1–10 micron layers. With such thin layers, experimental detection of stress distribution would be very difficult. Moreover, coating thickness is distributed differently on flat surfaces from on shaped features in coated tools. This non-uniform coating results solely from the technology applied and such uneven deposition of the coating is critical in terms of how the tools themselves function. The paper provides an analysis of stresses in thinner or accumulated layers of coating on the rounded edge, for example in cutting. This analysis was initiated by ProTech Coating Service, Ltd., which manufactures physical vapour deposition coatings for cutting and forming tools.

Monitoring of processes in component joints by intelligent system

The paper introduces the specific result of solved research project (ITMS 26220220125). The goal of project is to create the research and application base for transfer of new technological innovations of components for better mechanical power transmission to achieve higher quality, operational reliability and service life. The solution is the designing of on-line system for monitoring of dynamic processes. The applied monitoring and measuring system is tested in conditions of mass production factory. The application is available in paper.

Study of the Press Fit Bearing-Shaft Joint Dimensional Parameters by Analytical and Numerical Approach

The study of press fit bearing-shaft joint dimensional parameters by means of analytical and numerical calculations in order to identify those parameters of the press fit joints which significantly influence the life of the bearings fitted by pressing is dealt in this paper. The mounting and conditions of fit joint are the significant factors affecting the operability and life of the bearings and consequently that of rotating machines and the whole technical units. The aim of the analysis and study is to determine the tangential and radial stress, the radial displacement, and the influence of the shape features and the size of the interference on the change of the radii in the press fit bearing-shaft joint, in particular, the ball bearings of 6014 2RSR C3 type. Moreover, on the basis of obtained results, the paper discusses the impact of shaft dimensional and geometrical accuracy on the bearing lifetime.

Turning Tool with Helical Cutting Edge for Optimizing the Machining Time Performance

The paper presents turning with helical cutting edge employing the edge of twist drill and develops the special method of turning and its impact on the quality of machined surface. Finding the approach how to improve the surface quality and optimizing the machining time performance, the theoretical relation among the average maximum height of the machined surface profile Rz, the feed f and the radius of the tool tip re is known. Increasing the feed f, the surface roughness Rz increases quadratically. On the other side, increasing re, the surface roughness Rz decreasing hyperbolically. The limiting case is re = ∞. The specification of such tool function is the cutting edge inclination angle λs. Another option is to use helical cutting edge. In such case, re is curvature angle of helical edge. The experiments applied on different materials (dural and titanium alloys, brass) were performed to confirm the thesis of surface roughness quality improvement by use of helical cutting edge and moreover the significant increase in the productivity of turning were achieved regarding possibility to use several times larger feed rates. Short Research Article Vasilko and Murcinkova; ACRI, 3(4): 1-6, 2016; Article no. ACRI.24801 2