Materials Engineering - Materiálové inžinierstvo (MEMI - E-Journal)
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Finite element implementation of delamination in composite plates
Get PDFModelling of composite structures is limited by finite element (FE) codes to effectively model certain critical failure modes, such as delamination. Previous efforts to model delamination and debonding failure modes using FE codes have typically relied on ad hoc failure criteria and quasi-static fracture data. Improvements to these modelling procedures can be made by using an approach based on fracture mechanics. A study of modelling delamination using the finite element code ANSYS was conducted. This investigation demonstrates the modelling of composites through improved delamination modelling. Further developments to this approach may be improved
Influence of degradation process on rheological characteristics of polymer materials
No full textRheological properties of thermoplastic polymer materials before and after exposure in chemical solution were evaluated using Frequency sweep test, which monitors changes in viscoelastic properties of polymers with respect to their molecular structure and their behavior in thermoplastic processes. As experimental material thermoplastic polyethylene and polypropylene samples were used and subjected to influence of n‑hexane solution for period of 3 and 6 months. Measurements were performed using oscillating rheometer Physica Rheometer MCR 301 and carried out at the temperature of 160 °C and 180 °C. Degradation process resulted in changes of complex dynamic viscosity, storage and loss modulus, changes in molar mass and its distribution which sufficiently prove the rheological changes
Investigating the joining of PMMA plastic to steel by Nd:YAG laser
Get PDFDue to the effort of weight reduction in the manufacturing of vehicles, the application and therefore the joining of different materials such as plastics and metals play more and more important role in the development of the joining processes nowadays. In this research work, the joining of PMMA plastic sheets and unalloyed steel pins was investigated. The authors applied Nd:YAG laser beam to create the bond, and tensile tests were carried out to analyse how the strength of the joint is influenced by the heating time, the penetration depth of the steel workpieces in the plastic and the surface roughness of steel. The observed bubble formation and the tearing characteristics were also studied
THE ANALYSIS OF CAUSES OF LORRY PISTON COMBUSTION ENGINE DAMAGE
No full textThe article deals with analysis of causes of lorry piston combustion engine damage. For docummentation and analysis of causes was used macroscopical, microscopical and scanning electron microscopy. The analysis showed that the reason of fatal damage resides in production process of lorry combustion pistons which proved in implication of fatigue damage and subsequent burnout in two piston place
Properties of Plasma and HVOF Sprayed Coatings
Get PDFThe work compares the properties of plasma and HVOF thermally sprayed coatings obtained by blending the NiCrBSi and Fe2O3 powders. The deposition was performed by means of the Plancer PN-120 and the Diamond Jet guns for plasma spraying and HVOF spraying respectively. The SEM (EDS) method was employed to study the microstructure of the produced coatings. Although the blended powders differ in particle size, shape, and distribution, it is possible to obtain composite coatings with an NiCrBSi matrix containing iron oxides. Except for a different microstructure, plasma and HVOF coatings have a different phase composition, which was examined using the Bruker D-8 Advance diffractometer. Studies of the coatings wear and scuffing resistance showed that an optimal content of Fe2O3 is about 26 % for plasma sprayed coatings and 22.5 % for HVOF deposited coatings
MEASUREMENT OF QUENCHING INTENSITY, CALCULATION OF HEAT TRANSFER COEFFICIENT AND GLOBAL DATABASE OF LIQUID QUENCHANTS
Get PDFThis paper explains the need for a database of cooling intensities for liquid quenchants, in order to predict the quench hardness, microstructure, stresses and distortion, when real engineering components of complex geometry are quenched. The existing laboratory procedures for cooling intensity evaluation, using small test specimens, and Lumped-Heat-Capacity Method for calculation of heat transfer coefficient, are presented. Temperature Gradient Method for heat transfer calculation in workshop conditions, when using the Liscic/Petrofer probe, has been elaborated. Critical heat flux densities and their relation to the initial heat flux density, is explained. Specific facilities for testing quenching intensity in workshop conditions, are shown. The two phase project of the International Federation for Heat Treatment and Surface Engineering (IFHTSE), as recently approved, is mentioned
SOLUTION TREATMENT EFFECT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AUTOMOTIVE CAST ALLOY
No full textThe contribution describes influence of the heat treatment (solution treatment at temperature 545°C and 565°C with different holding time 2, 4, 8, 16 and 32 hours; than water quenching at 40°C and natural aging at room temperature during 24 hours) on mechanical properties (tensile strength and Brinell hardness) and microstructure of the secondary AlSi12Cu1Fe automotive cast alloy. Mechanical properties were measured in line with EN ISO. A combination of different analytical techniques (light microscopy, scanning electron microscopy (SEM)) were therefore been used for study of microstructure. Solution treatment led to changes in microstructure includes the spheroidization and coarsening of eutectic silicon. The dissolution of precipitates and the precipitation of finer hardening phase further increase the hardness and tensile strength of the alloy. Optimal solution treatment (545°C/4 hours) most improves mechanical properties and there mechanical properties are comparable with mechanical properties of primary AlSi12Cu1Fe alloy. Solution treatment at 565 °C caused testing samples distortion, local melting process and is not applicable for this secondary alloy with 12.5 % Si
Nodular cast iron fatigue lifetime in cyclic plane bending
Get PDFThe fatigue behavior of a component is strongly dependent on the material and its surface condition. Therefore, the manner in which the surface is prepared during component manufacturing (surface roughness, residual stresses etc.) has a decisive role in dictating the initiation time for fatigue cracks. The fatigue behavior of the same material, a nodular cast iron, with three different surface conditions (fine ground, sand blast and as-cast) has been investigated under cyclic plane bending. The results show differences in fatigue strength, which are associated with the surface conditions. The characteristics of the surface layers of the different test specimens were examined by metallography
An Apparatus of increased precision for the Measurement of Electro-Optical parameters of Liquid Crystals
Get PDFThe ferroelectric liquid crystals (FLCs) are demanding high attention now a day, because of their potential applications in many electro-optical devices, particularly in displays. The suitable applications of FLCs in devices are decided by their electro-optical properties like tilt angle, birefringence and spontaneous polarization. In this paper we are presenting a new apparatus for highly accurate measurement of electro-optical parameters of FLCs. The accuracy of the apparatus is the best among the currently available equipments in the market. The accuracy and performance of the apparatus has been confirmed by performing the experiments on standard ferroelectric liquid crystals
MICROSTRUCTURE AND FRACTOGRAPHIC ANALYSIS OF DAMAGE REASONS OF COGWHEEL
No full textThe article provides an analysis of the damaged cogwheel, which was used as the drive wheel (pinion) in the steering gear box of the construction machine. The degradation of the cogwheel arose during the warranty period, after seven months of using of the construction machine. The experimental analysis revealed that the cause of the degradation of the cogwheel was due to high mechanical stress in the operating conditions of construction machine