Papers by Keyword: Chemical Composition

Abstract: The metallography was used for evaluation of fractured elements from different aluminium alloys´ elements applied in Czech transmission system. Although the fractured elements were produced from different aluminium alloys (hypereutectic Al-18%Si, AlSi10Mg, Al0,7MgSi) the main reason of fractures was very similar for all of them – the low quality of casting, inhomogeneous structure and composition of matrix. These analyses were performed on fracture surfaces and on reference matrix. Typical defect evident on fractured areas was dark stains. In some cases, the quartz concentration was ca twice into comparison with standards composition and reference matrix.

Abstract: The metallography was used for evaluation of localised form of corrosion of stainless steel tubes of heat exchangers. The heat exchangers were in service for relative short period from few months to 2 years. The service conditions of these heat exchangers were different (temperature, medium, etc.) and caused penetration of tube walls. The metallography cross sections were used to identified the corrosion mechanisms. For all evaluated cases the different mechanisms were found – pitting corrosion, microbiologically induced corrosion, trans-crystalline corrosion cracking, intercrystallite corrosion cracking. Together with diffraction and elementary analysis of corrosion products the metallography evaluation was used for identification of corrosion mechanisms.

Abstract: Aircraft components have different functions and characteristics, for example, the bolt and nut pressure switch of Cessna Grand Caravan 208B, which functions to determine the pressure of oil and fuel flowing. At the end of the bolt and nut, there is a small hole to press the sensor in the component, then the result of the pressure will be converted to the system and sent to the indicator located in the cockpit, so the pilot sees the actual in the cockpit. The purpose in this research was to determine the characteristics of the bolt and nut pressure switch. This study used chemical composition, Vickers hardness, and metallographic testing methods. The test results of the chemical composition of bolt and nut on the pressure switch of Cessna Grand Caravan 208B, show that the elements, iron (Fe) = 67.58% and chromium (Cr) = 17.04%, are the dominant elements, therefore it is included as an alloying element of Fe-Cr. The test an average hardness value of 254.64 VHN. These values were obtained from the total percentage of iron 67.58% and chromium 17.04%. Chromium (Cr) is an element that can increase the hardness of carbon steel and increase corrosion resistance. Therefore, the hardness of the bolt and nut pressure switch of Cessna Grand Caravan 208B is high due to the addition of Cr which help the main element, Fe, properties. The novelty of this study is the dominant presence of chromium, so the properties of this material are hard, heat resistant, and corrosion resistant

Abstract: This study aims to determine the effect of the mold casting duct variations on shrinkage, porosity defects, density, hardness, and chemical composition of materials. The primary raw material uses melting secondary aluminium through a small-scale smelting furnace. Research study about three kinds of ducts: triangular duct, rectangular duct, and circular duct. The testing chemical composition uses an emission spectrometer. Research founds defects by comparing the dimensions of the original object with the specimen results of each duct variation. The density value calculates porosity defects. ASTM E10 standard Brinell test measures the hardness. Besides, ASTM E3 standard test quantifies the microstructure of the product. The highest average shrinkage is the triangular ducts at 3.68%. The least significant numbers of porosity were in rectangular ducts of 2.964 gr/ml. Higher the density value, the denser the material, and the more negligible the porosity. The density of the material affects the hardness material obtained from the results of the Brinell test. The hardness of the Brinell test brought that the rectangular duct with 102.5 BHN was the most enormous. In addition, the results showed that the chemical composition mainly contained mostly chemical elements (Al) 87.1% as the main chemical ingredient and (Si) 9.51%.

Abstract: Electrochemical discharge machining (ECDM) is a hybrid method used to generate micro-features in hard and brittle materials (glass, ceramics, and composites) in aerospace, microelectromechanical systems (MEMS), and microfluidic applications. A significant improvement was observed in ECDM process but the effect of the process on the health of working operator are rarely investigated. Sustainability in manufacturing is a major concern for a better environment and safety of human operators. In this paper, analysis of fumes mass concentration (FMC), size and morphology of fume particles, and composition of fume particles along with their biological effects are studied during ECDM of CFRP composites. FMC was calculated by varying the concentration of electrolyte from 20 to 50% and duty cycle from 60 to 90% for a fixed sampling duration of 30 minutes. SEM images indicated the presence of spherical, irregular, and loosely packed fumes particles in the fumes generated during machining. EDS was also performed to study the chemical composition of fumes particles.

Abstract: This paper deals with the chemical analysis of the coating on building materials which were used for construction of Mánes bridge in Prague. It is a historical bridge which is more than a hundred years old. Using the method of infrared spectroscopy, we can determine the organic and inorganic compounds in coatings, adhesives, grout, and polymer materials. The organic compounds are added into the concrete and other building materials due to improvement of physical and mechanical properties such as compressive strength, tensile strength, modulus of elasticity or water absorption. The building materials can be covered with the coating for protection against mechanical damage. The chemical analysis of the building material is important to know before reconstruction and remediation of the historical buildings. As a result, the infrared spectrum of the coating was measured and it was determined that the coating was on the acrylate base.

Abstract: The article deals with the use of granite filer as a concrete admixture. It examines the filter in detail not only as a whole (one component in concrete) but separates it into fractions. Since it is a filter produced during cutting, grinding and polishing of granite elements, it is granite slurry. For these reasons, the simplest method of separation - sedimentation in a flowing liquid - was applied to separate the individual fractions. After drying, the individual fractions were examined for their suitability for use in concrete. The most important physical and chemical parameters - bulk density, specific surface area, grain shape and size, chemical composition - were determined. Based on the measured values and in relation to previous in-house investigations, granite filer can be considered as a suitable admixture for cement composites.

Abstract: The work intends to study the microstructure, chemical and phase composition and homogeneity of chemical elements distribution in the Co-Cr-Fe-Mn-Ni high-entropy alloy produced via wire-arc additive manufacturing technology. The study has revealed three structure types in the alloy: (1) a smooth shagreen-type structure (an orange peel), which turns into a stripe-like structure (2) in some areas, and a grain structure (3) to appear as lengthy thin layers with the width of 50-80 μm and an average grain size of 12.5 μm, the most probable size of grains is detected to be in the range from 10 to 15 μm, a preferred number of such grains is 31%. The chemical composition of the produced alloy is assessed using X-ray microspectroscopy. The elements identified rank in descending order of concentration: Fe (38.88 wt. %), Co (26.08 wt. %), Ni (17.34 wt. %), Cr (14.33 wt. %), Mn (3.37 wt. %). The mapping of the alloy structure demonstrates the homogeneous and uniform distribution of chemical elements.

Abstract: The mechanical properties of different classes of titanium alloys have been compared during tensile tests and upset tests in the temperature range of 20-1200 °C. It has been established that at temperatures of 20–500 °C, the maximum strength is observed for the α+β-transition alloys, and at 600–800 °C – for heat-resistant near α-and α+β-alloys. At temperatures exceeding 900 °C and up to the polymorphic transformation point, the softening of titanium alloys is mainly defined by the content of α-stabilizers and neutral hardeners. At temperatures above the polymorphic transformation point, the tensile strength does not depend on the aluminum and molybdenum equivalents.

Abstract: The steelmaking process results in the by-product formation of electric arc furnace slag (EAFS). Slag is recovered at two different stages of the steelmaking process, the first recovery is black and the second is white. The present research focuses on the composition differences between the two types of slag from SONASID-Jorf steel in Morocco. A granular separation of the black and white slag was carried out to monitor the chemical and mineralogical composition. XRD and Fourier Transform Infrared Spectroscopy are performed on the samples in this paper. The slags suggest good hydraulic binder properties. It would be useful for research in the field of building materials to correlate the results of the characterization of EAFS with other types of slag with the aim of improving the potential for partial replacement of cement in the matrix. The slag can also be used as binders in mixtures of bio-based building materials. The electric arc furnace slag (EAFS), exhibiting appropriate cementitious activity, can be utilized as mineral admixture in cement and concrete. Black and white slags are studied in this paper in order to determine their characteristics according to their granularity.