Applied Mechanics and Materials Vols. 809-810

Abstract: In this paper issues of stress analysis of composite materials are presented. The components of composite materials and principles of composition has been discussed. Particular attention was paid to the epoxy resins and the fabrics made from carbon fibers. The article also includes basic information about strain measurements performed on with a resistance strain gauge method. For the purpose of the laboratory tests a series of carbon - epoxy composite samples were made. The main aim of the studies was to compare the results of two different research methods – laboratory and simulation method. During laboratory strain tests described in the paper, a composite samples were loaded with a specified load. Tenmex's delta type strain gauge rosettes were used to measure strain. They were arranged in specific locations on the surface of the samples. Data acquisition procedure were carried out using HBM measurement station. Numerical studies were carried out in a computing environment, Siemens NX 9.0. The results of simulation and laboratory tests were compared and presented in the form of graphs. They allow you to validate the method of laboratory measurements. The results of both research types have shown the percentage difference between them for individual loads applied to each composite.

Abstract: Prediction of a polymer properties, based on its composition, is a complex problem with no easy method to obtain directly and accurately results. Among the tribological properties, the friction coefficient and wear rate are the most interesting ones. The epoxy resin based polymers, with clay as filler, shows different properties following the clay concentration. This paper presents an analysis of the properties variation with filler concentration, for a polymer. Due to tribological processes complexity, mechanical and thermal properties must be taken into account. The aim of the study is to find an optimal concentration value, with minimal influence on polymer properties. All value properties will be used in a neural network model in order to optimize and predict composite properties.

Abstract: The mechanical properties of composite fabrics rely on a fabric made by a textile weaving process. In order to use their special ability of being drapeable, instead of just plain weave fabrics, satin or twill reinforcement can be selected. Although some other advantages of the resulting composite, such as good impact resistance or damage tolerance are similar to all woven reinforcement composites, the superior drapeability of satin is a major reason to favour this type of textile reinforcement. This paper is focused on the modelling procedures of stiffness characteristics, specific to satin reinforced laminated composites, using a semi-discrete approach. This method is a compromise between the continuous and pure discrete approaches and is associated with a mesoscopic analysis of the repetitive unit cell (RUC). The elastic properties of the textile reinforced epoxy composite, namely longitudinal modulus and transverse modulus, in case of carbon and fibre glass based 5-harness satin reinforcement, are determined. The differences between the two resulting composite materials and the influence of the various geometric and material parameters involved are studied.

Abstract: A new FeMnSi metallic alloy is proposed as biodegradable material with applications in medical field. The corrosion behavior in simulated body fluids is evaluated after immersion for 14 days. The metallic biodegradable material surface was analyzed with a SEM (2 and 3D)+EDAX equipment. The effects of the solution on the metallic surface present an area with pitting corrosions, marks around 10 µm in depth, and a different one with new chemical compounds form from biological solution with good stability on the surface. Even if is a new biodegradable material based on iron simmilar results about the surface behavior were obtain by other researchers on different FeMnSi chemical compositions.

Abstract: A new cast iron material with a higher Cr content than usual is analyzed by chemical, micro-structural and friction coefficient point of view. The material was obtained by classical melting and the results compared with the experimental results obtained from a standard cast-iron used for applicative disk brake. Four different mechanical solicitation rates were used on the same material surface and the same load. The solicitation regime can be considered as semi-liquid and similar to a raining day experimental conditions. In this paper no thermal considerations were present or discussed. The results present a bigger friction coefficient of the new material and further considerations are necessary for example in a different friction regime.

Abstract: Bumper beam absorbs the accidental kinetic energy by deflection in low-speed impact and by deformation in high-speed impact. Based on the last years necessity of lighter materials and safer usage of vehicles we try to come with a new class of materials for bumper systems. Analyze of metallic materials is cheaper when the analyze take place on a computer avoiding the metallic loss or energy consume. We present few results obtained in Catia software about the behavior of some metallic materials under external solicitations in function of the mechanical properties of metallic elements, geometry of the element, restrains and solicitation points. Shape memory alloy are smart materials that can use the external mechanical energy damping to thermal energy in bumper applications. In martensite to austenite domain we observe an increase of damping mechanical capacity with possible applications in bumper systems.

Abstract: The present investigation has been conducted in order to study the fatigue and corrosion fatigue behaviour of an aluminium alloy (99,5%Al) substrate coated with a 106 MXC deposited by thermal spraying in electric arc. It has been determined that the deposition of such a coating on the aluminum substrate gives rise to significant gains in fatigue life in comparison with the uncoated substrate, when testing is carried out both in air and in a 3,5 wt.% NaCl solution. It has been shown that during testing in air, the fatigue gain ranges between ~131 and 186%, depending on the maximum alternating stress applied to the material. Larger fatigue gains are associated with low alternating stresses. Also, when fatigue testing is conducted in the NaCl solution, the gain in fatigue resistance varies between ~124 and 159%. Fatigue cracks have been observed to initiate at the coating surface and then grow towards the substrate after propagating through the entire coating thickness. Although in the present work residual stresses were not measured, it is believed that the gain in fatigue life of the coating–substrate system is due to the presence of compressive residual stresses within the coating which hinder fatigue crack propagation. The deposition of the coating does not give rise to significant changes in the static mechanical properties and hardness of the aluminum alloy substrate.

Abstract: An ideal dynamical system should not generate any vibrations, because vibrations mean a loss of energy. Vibration in planetary precessional gear box occurs at bearings, gear wheels, misaligned shafts, imbalance rotating parts, couplings. If damage occurs, not only the dynamic processes change, but also the forces that act on system components. Regarding this aspects, regular vibration measurements on machines provide information about any necessary maintenance. Vibration research was made by using GUNT PT500 Machinery Diagnostic System and vibration signals was evaluated by using GUNT PT500.04 software witch allow to perform correct FFT analysis. Data acquisition was made by using two piezoelectric accelerations sensor type IMI603C01 and one reference photoelectric sensor to record the shaft speed. Sound level was measured by using Brüel & Kjær Sound Level Meter Type 2250 Light that has everything needed to perform high-precision, Class 1 measurement tasks in environmental, occupational and industrial application areas. Obtained and measured results was presented in diagrams and tables to be compared with German standard VDI-2058 Limit value for vibration severity and noise level.

Abstract: The work presents an optimisation method for the rotating cam and knife edge follower mechanism using optimisation restraints required to the cam curvature radius when the follower motion law is provided. Imposing a constraint to the cam curvature radius implies a connection between the constructive mechanism parameters. The optimisation condition is plotted in the plane of constructive parameters and a closed curve corresponds to the case of a law of motion with continuous acceleration. If the “characteristic point” is placed outside this region, automatically conducts to fulfilled condition, for any mechanism’s position. For an analytical study, in the present work, the restraint of strictly positive cam curvature radius was imposed.

Abstract: Studying the diagrams of characteristics of complex subsystem of mechatronic one it has been determined that in case of approximate method the resonance frequencies cover with those which have been determined with exact method. However the values of the characteristic in other areas are different. Therefore there is the mistake of approximate method, which in case of studying the single systems does not have any influence because in resonance areas the characteristic values of the system approach to the infinity. However the difference in values of flexibility within two methods has the great influence on the result of complex systems. The main subject of deliberation was to determine the flexibility of the complex system with constant cross section using the exact and approximate that means Galerkin's method. The mechanical and/or mechatronic system composed from many mechanical subsystems having the same length and variable cross section, loaded by the focused moment was analysed. One case of attachment the complex system that means free torsional vibrating bar were examined. That why it was necessary to correct the results of approximate method. The problems presented in this paper, that means the analysis of subsystem of mechatronic and mechanical complex systems is however the introduction to the synthesis of torsional vibrating mechatronic systems with assumed frequency spectrum.