Abstract: This paper treats the design and analysis of an energy absorbing system. Experimental tests were conducted on a prototype, and these tests were used to validate a finite element model of the system. The model was then used to analyze the response of the system under dynamic impact loading. The response was compared with that of a similar system consisting of straight circular tubes, empty and foam-filled conical tubes. Three types of such supplementary devices were included in the energy absorbing system to examine the crush behavior and energy absorption capacity when subjected to axial and oblique impact loadings. The findings were used to develop design guidelines and recommendations for the implementation of tapered tubes in energy absorbing systems. To this end, the system was conceptual in form such that it could be adopted for a variety of applications. Nevertheless, for convenience, the approach in this study is to treat the system as a demonstrator car bumper system used to absorb impact energy during minor frontal collisions.
Abstract: Mono layer graphene (MLG) as a new kind of advanced material is in our focus. MLG indicates a twodimensional structure with quantum confinement effect in its thickness. The MLG based nanomaterial has remarkable potential on electrochemical catalysis and bio-sensing applications. Recently inter sheet sensing systems for graphene sensor have been reported which will be used in our model as well. We provide a new idea of electrochemical sensors based on the graphene application. In this paper carrier the concentration on the sensor as a function of gas concentration is reported. A field effect transistor (FET) base structure as a modeling platform is proposed. Gate voltage representing the gas concentration on the sensor, or in other words the gate voltage as a function of gas concentration can be employed. Finally the proposed model is used in simulation studies and evaluated by experimental result.
Abstract: The paper presents the numerical procedure for modelling the behaviour of steel structures at high temperatures using a newly developed implicit creep model. This implicit creep model uses the calculated creep strains to modify the material stress-strain curves, thus implicitly taking into account the effect of the developed creep strain. The newly calculated stress-strain curves are modified by stretching the initial temperature-dependent stress-strain curves using the calculated values of the creep strain which depend on the level of temperature and stress that the section of structure is being exposed to during fire. The implicit numerical procedure has been implemented in a previously developed numerical model for predicting the behaviour of structures under fire. In order to test the validity of the newly developed implicit creep model, an in-house fire experiment was performed. Results of the experiment have shown a good agreement with the model predictions indicating the validity of the developed implicit numerical procedure.
Abstract: The evaluation of stability of secondary phases in superalloys is of great importance because of its application under high homologue temperatures. The precipitation hardening Inconel 718 superalloy has high stress rupture and creep resistance, good LCF behavior and high corrosion resistance. Those properties can be obtained due to the high stable matrix based on Ni, Fe and Cr, as well as secondary phases promoters elements such as Ti, Al and Nb. This study aims to analyze the phase stability among a range of temperature from 500°C to approximately 1400°C. The thermodynamic modeling has a high importance to predict the behavior of alloys among equilibrium transition. The microstructure of the system was evaluated using Thermo-Calc software and the selected databases: SSOL4 and TTNI6. This analysis made possible the prediction of the phases presented, compositions and amounts. Results from SEM analysis were used to compare the results obtained, showing good coherence between them.
Abstract: A composite containing A356 Al alloy as matrix and ZrB2 particles was made in an induction furnace by mixing Al-15Zr and Al-8B master alloys with Zr:B weight ratio of 9:2. The microstructures and tensile properties of the extruded composite were studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis before and after T6 heat treatment. XRD results showed the presence of ZrB2 phase in the microstructure. Tensile test results showed an increase in ultimate tensile strength (UTS) and elongation values of the extruded composite in comparison with the matrix alloy. Further investigation showed an increase in UTS, but reduction in elongation values of the composite after T6 heat treatment.
Abstract: onic Liquids (ILs) provide an alternative green solvent for separating aromatic from its mixture with aliphatic hydrocarbon. The present work demonstrates the screening of potential IL for separation of benzene (aromatic) from n-hexane (aliphatic) using COSMO-RS. A total of 10 imidazolium based cations and 52 different anions resulting in 520 possible combinations of ILs were studied. The COSMO-RS was used to theoretically calculate the activity coefficient at infinite dilution (γ) for benzene and n-hexane in each of the ILs. Consequently, from the activity coefficient (γ) value, the capacity (C) and selectivity (S) at infinite dilution for each ILs with regards to the benzene/n-heptane separation were calculated. The Performance Index (PI) which is the product of the capacity (C) and selectivity (S) is then determined and compared against sulfolane as the benchmarking solvent, used widely by industry for the separation of benzene and aliphatic hydrocarbon. The result showed 20 ILs with C, S, and PI value higher than sulfolane thus making them as potential candidate for the separation application.
Abstract: This study was conducted to determine if austempered 4340 steel had different mechanical properties compared to step quenched 4340 steel. Tensile strength and impact energy was determined at room temperature under identical test conditions. The specimens were cut from a bar with 25 mm diameter and austenitized at 800°C for 60 min and followed by quenching at 430°C for the high austempering temperature to achieve the upper bainite morphology and at 360°C for the lower austempering temperature to achieve the lower bainite morphology. In the case of step quenched, the specimens were first austempered at 430°C and then austempered at 360°C to achieve the mixed structure of upper bainite and lower bainite morphology. The another set of specimens for step quenching, after austenitization were quenched to below Ms (martensite start temperature), followed by heating at 400°C to achieve the mixed structure of tempered martensite and lower bainite and 500°C to achieve the mixed structure of tempered martensite and upper bainite. It is also shown that the best combination of strength and ductility can be achieved by the mixed structure of tempered martensite and lower bainite that has been suggested in this investigation.
Abstract: To date, efforts forwarding to develop thermal spray coatings technology have been focused on increasing the durability and integrity of the coating. Improvement of mechanical characteristics such as wear resistance of the deposit, minimizing residual stress levels and reducing porosity are the main objectives of these works. The specific aim of this paper is to determine the wear resistance of molybdenum coating thermally sprayed on a steel substrate. This behavior has been determined using a simple ball-on-plate tribometer. Attention was given on the influence of a post-annealing at 850°C for one hour in vacuum and oil lubrication conditions.
Abstract: A new developed formula named the Habashi-Zul formula, based on the Maxwell-Garnett (MG) formula was fabricated and used to calculate the complex permittivity of the Sm-YIG in PVDF composite samples in the frequency range of 10 MHz to 1 GHz. The calculated permittivities results were compared with the measured values of each sample of Sm-YIG in PVDF composite samples and, with calculated results from various theoretical models including the MG, Looyenga, Bruggeman and, Sen Scala and Cohen. The Habashi-Zule formula presented higher accuracy as compared to other models.