Abstract: In this paper, effect of stress ratio was investigated on macro and micro of fatigue crack growth rates (FCGRs) of Al-alloy 2024 T351. Microscopic fatigue crack growth rate present a change of slope with respect to the macroscopic fatigue crack growth rate. In addition, an increasing in stress ratio increases the fatigue life. Fractographic examination showed the presence of striations in Paris domain and secondary cracks at grain boundaries.
Abstract: The chemical degradation of stainless steel components in sulfur-containing environments is a major concern in oil and gas production. 4130 Cr-Mo alloy steel is widely used as tubing and tubular components in sour services. According to the previous research in aqueous conditions, contact of solid sulfur with alloy steel can initiate catastrophic corrosion problems. This paper discusses elemental sulfur corrosion of Cr-Mo alloy steel in 3.5% sodium chloride solution at pH 2 and 5 during 20 and 30 hours immersion time. The corrosion behavior was monitored by potentiodynamic polarization technique during the experiments. Energy Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscopy (SEM) have been applied to characterize the corrosion products after each experiment.
Abstract: In order to improve the corrosion resistance of Data Matrix (DM) code laser marked on aluminum alloy, the salt spray corrosion resistance was determined. First, the corrosion resistance of DM code laser marked by 3 different processing modes was investigated. Meanwhile, the SEM images and EDS data for modules and substrate of DM code are analyzed, which explains the differences of corrosion resistance for DM code by the 3 processing modes. A kind of laser combined electrochemical marking method for anti-corrosion DM Code mark was put forward, where a bare mark of DM code was created by direct laser marking in advance, and then a uniform, compact and protective oxide film was deposited on the bare mark by electrochemical oxidation to form the corrosion resistant mark. The results show that the corrosion resistance of laser direct marking DM code for different processing modes exist some difference. However, all the DM code samples become failure after at most 15.5 hours salt spray corrosion. The DM Code mark by the proposed method can withstand approximately 42 hours of salt spray corrosion, whose corrosion resistance improved 2-3 times.
Abstract: Perovskite La1-xSrxFe0.7Ni0.3O3-δ with x = 0.0, 0.1 &0.2 denoted LSFNx has been investigated as potential symmetrical electrode in solid fuel cells (SOFCs). The crystal structure is in pure orthorhombic phase for x = 0.0, orthorhombic-cubic phase coexist for x = 0.1 and pure cubic phase for x = 0.2. Structural properties are studied by X-ray powder diffraction (XRPD), refined by Rietveld analysis. SEM images show the morphology of as prepared and calcined samples either the compatibility between those electrodes and LSGM electrolyte in presence of 50% wt of Ce0.8Gd0.2O2-δ, so that, lower chemical reactivity was found. Total conductivity, impedance in high, medium and low frequencies HF, MF and LF respectively, and resistance polarization (Rp) are determined in air. LaFe0.7Ni0.3O3-δ has a good response in all ranges of frequencies but La0.9Sr0.1Fe0.7Ni0.3O3-δ and La0.8Sr0.2Fe0.7Ni0.3O3-δ have response only in HF and MF and exhibit Rp values as low as LaFe0.7Ni0.3O3-δ .
Abstract: Gas sensor performance is strongly influenced by the crystal structure, composition and morphology of the material used. In this paper, structural and morphological analysis of nanocomposite SnO2-Graphene synthesized by Sol-Gel method with the composition of 1:1, 1:2, 1:3 will be described. Analysis of the morphology and structure of nanocomposite SnO2-Graphene is investigated using XRD, SEM and TEM with the purpose of obtaining the crystal structure, morphology, composition and size of the resulting particles. The XRD results showed that the formation of the crystalline phase can be recorded at 2θ = 26.64; 34.2; 51.92, where the results of SEM show that the nanomaterial SnO2 has tetragonal structure while the graphene has hexagonal structure. The nanocomposite SnO2-Graphene has nanorod pattern. Furthermore, the surface analysis using TEM of nanocomposite SnO2-Graphene shows that the surface has the rod diameter in the range of 5-8 nm. The unique nanopattern of SnO2-Graphene will have potential applicability as the sensing material for CO gas sensor.
Abstract: This paper addresses the problem of open thin coatings of constant thickness made from Kevlar composite material.
Kevlar is an organic polymer fiber 5 times stronger than steel taken at the same weight. Therefore, this fiber has been used successfully in producing composite materials. In this paper, the generic name of Kevlar designates the composite material having the following characteristics: E=7,6×104MPa; θ=0,34; ρ=1700kgcm3.
The program COSMOS/M with which the study was conducted and broadcasted was The Structural Research and Analysis Corp.
The analysis was carried out by the finite element method.
Abstract: Ultrasonic-Assisted Milling (UAM) combines the material removal mechanism of grinding and the milling kinematics with ultrasonic assistance. The process is suitable for hard-to-cut materials used in many industrial applications. UAM is a novel process, still under investigation to clarify the product accuracy and the process performance. This paper presents a literature review covering the development of the experimental work related to UAM. A summary of key research problems is concluded and a systematic study using the design of experiments is suggested in order to investigate the effects of the main process parameters on its performance.
Abstract: This study is to investigate the curing of silver conductive ink tracks on fabrics using a combination of direct light projector (DLP) and hot plate since conventional curing process using laser and oven suffer from several weaknesses mainly costly process and warping defect. The fabrics used are made from nylon and polyester while silver conductive inks were used for the entire study. Samples were made by coating the fabrics with rubber dye inks using silkscreen process and conductive inks were manually laid out on top of the rubber dye according to the designated pattern. A Microsoft power point slide is used to shape the light image on top of the hot plate where the sample is located. Variation of curing time and temperature with constant curing distance were investigated. Several mechanical and electrical tests were conducted to determine the cure, hardness, adhesion and resistance level of the ink tracks. The results obtained were as expected which the longer curing time taken and a higher temperature used, a lower resistance is produced. It is proven that a combination of projector and hot plate is capable of curing the ink tracks properly, a cheap process and easy to handle.
Abstract: The engineered nanoparticles are more and more entering in Romanian working places, both in research laboratories and in manufacturing processes. Ever increasingly numerous evidence shows that this materials science revolution can generate significant health, safety and environmental hazards, in addition to the social, economic and ethical challenges involvedBased on the precautionary principle recommended be the European Union and a thorough literature review, this research is intended to introduce a framework for further development of an Occupational Health and Safety risk management foundation in this field of concern. Starting from a systematic approach in terms of occupational exposure, the paper emphasizes certain feasible means aimed at nanoparticle’s risk assessment, particularly in a qualitative manner. Recommendations are provided for the industry in order to meet the safety regulations, which in turn should be adapted to the findings of researches, considering that we are facing emerging risks whose nature is often unknown.