Search results for: dual phase 590 steel

Authors: A. A. Azab

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In this work, Sm0.6Sr0.4CoxMn1-xO3 (x=0, 0.1, 0.2 and 0.3) was synthesized by sol-gel method for magnetocaloric effect (MCE) applications. XRD analysis confirmed formation of the required orthorhombic phase of perovskite, and there is crystallographic phase transition as a result of substitution. Maxwell-Wagner interfacial polarisation and Koops phenomenological theory were used to investigate and analyze the temperature and frequency dependency of the dielectric permittivity. The phase transition from the ferromagnetic to the paramagnetic state was demonstrated to be second order. Based on the isothermal magnetization curves obtained at various temperatures, the magnetic entropy change was calculated. A magnetocaloric effect (MCE) over a wide temperature range was studied by determining DSM and the relative cooling power (RCP).

Keywords: magnetocaloric effect, pperovskite, magnetic phase transition, dielectric permittivity

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Authors: M. I. Equbal, R. K. Ohdar, B. Singh, P. Talukdar

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Micro-alloyed steel components are used in automotive industry for the necessity to make the manufacturing process cycles shorter when compared to conventional steel by eliminating heat treatment cycles, so an important saving of costs and energy can be reached by reducing the number of operations. Micro-alloying elements like vanadium, niobium or titanium have been added to medium carbon steels to achieve grain refinement with or without precipitation strengthening along with uniform microstructure throughout the matrix. Present study reports the applicability of medium carbon vanadium micro-alloyed steel in hot forging. Forgeability has been determined with respect to different cooling rates, after forging in a hydraulic press at 50% diameter reduction in temperature range of 900-11000C. Final microstructures, hardness, tensile strength, and impact strength have been evaluated. The friction coefficients of different lubricating conditions, viz., graphite in hydraulic oil, graphite in furnace oil, DF 150 (Graphite, Water-Based) die lubricant and dry or without any lubrication were obtained from the ring compression test for the above micro-alloyed steel. Results of ring compression tests indicate that graphite in hydraulic oil lubricant is preferred for free forging and dry lubricant is preferred for die forging operation. Exceptionally good forgeability and high resistance to fracture, especially for faster cooling rate has been observed for fine equiaxed ferrite-pearlite grains, some amount of bainite and fine precipitates of vanadium carbides and carbonitrides. The results indicated that the cooling rate has a remarkable effect on the microstructure and mechanical properties at room temperature.

Keywords: cooling rate, hot forging, micro-alloyed, ring compression

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Authors: Shalini Menon, K. Girish Kumar

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Norepinephrine (NE) is one of the naturally occurring catecholamines which act both as a neurotransmitter and a hormone. Catecholamine levels are used for the diagnosis and regulation of phaeochromocytoma, a neuroendocrine tumor of the adrenal medulla. The development of simple, rapid and cost-effective sensors for NE still remains a great challenge. Herein, a dual-channel sensor has been developed for the determination of NE. A mixture of AgNO₃, NaOH, NH₃.H₂O and cetrimonium bromide in appropriate concentrations was taken as the working solution. To the thoroughly vortexed mixture, an appropriate volume of NE solution was added. After a particular time, the fluorescence and absorbance were measured. Fluorescence measurements were made by exciting at a wavelength of 400 nm. A dual-channel optical sensor has been developed for the colorimetric as well as the fluorimetric determination of NE. Metal enhanced fluorescence property of nanoparticles forms the basis of the fluorimetric detection of this assay, whereas the appearance of brown color in the presence of NE leads to colorimetric detection. Wide linear ranges and sub-micromolar detection limits were obtained using both the techniques. Moreover, the colorimetric approach was applied for the determination of NE in synthetic blood serum and the results obtained were compared with the classic high-performance liquid chromatography (HPLC) method. Recoveries between 97% and 104% were obtained using the proposed method. Based on five replicate measurements, relative standard deviation (RSD) for NE determination in the examined synthetic blood serum was found to be 2.3%. This indicates the reliability of the proposed sensor for real sample analysis.

Keywords: norepinephrine, colorimetry, fluorescence, silver nanoparticles

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Authors: Nayeli Camacho, Fernanda Lara-Perez, Carolina Ortega-Portilla, Diego G. Espinosa-Arbelaez, Juan M. Alvarado-Orozco, Guillermo C. Mondragon-Rodriguez

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Ultra-high molecular weight polyethylene (UHMWPE) has been the gold standard material for total knee replacements for almost five decades. Wear damage to UHMWPE articulating surface is inevitable due to the natural sliding and rolling movements of the knee. This generates a considerable amount of wear debris, which results in mechanical instability of the joint, reduces joint mobility, increases pain with detrimental biologic responses, and causes component loosening. The presence of wear particles has been closely related to adverse reactions in the knee joint surrounding tissue, especially for particles in the range of 0.3 to 2 μm. Carbon-based materials possess excellent mechanical properties and have shown great promise in tribological applications. In this study, diamond-like carbon coatings (DLC) and carbon nanotubes (CNTs) were used to decrease the wear rate of ultra-high molecular weight polyethylene. A titanium doped DLC (Ti-DLC) was deposited by magnetron sputtering on stainless steel precision spheres while CNTs were used as a second phase reinforcement in UHMWPE at a concentration of 1.25 wt.%. A comparative tribological analysis of the wear of UHMWPE and UHMWPE-CNTs with a stainless steel counterpart with and without Ti-DLC coating is presented. The experimental wear testing was performed on a pin-on-disc tribometer under dry conditions, using a reciprocating movement with a load of 1 N at a frequency of 2 Hz for 100,000 and 200,000 cycles. The wear tracks were analyzed with high-resolution scanning electron microscopy to determine wear modes and observe the size and shape of the wear debris. Furthermore, profilometry was used to study the depth of the wear tracks and to map the wear of the articulating surface. The wear tracks at 100,000 and 200,000 cycles on all samples were relatively shallow, and they were in the range of average roughness. It was observed that the Ti-DLC coating decreases the mass loss in the UHMWPE and the depth of the wear track. The combination of both carbon-based materials decreased the material loss compared to the system of stainless steel and UHMWPE. Burnishing of the surface was the predominant wear mode observed with all the systems, more subtle for the systems with Ti-DLC coatings. Meanwhile, in the system composed of stainless steel-UHMWPE, the intrinsic surface roughness of the material was completely replaced by the wear tracks.

Keywords: CNT reinforcement, self-lubricating materials, Ti-DLC, UHMWPE tribological performance

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Authors: Derkaoui Orkia, Lehireche Ahmed

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The topic of this article is to exploring the potentialities of a powerful optimization technique, namely Semidefinite Programming, for solving NP-hard problems. This approach provides tight relaxations of combinatorial and quadratic problems. In this work, we solve the maximum clique problem using this relaxation. The clique problem is the computational problem of finding cliques in a graph. It is widely acknowledged for its many applications in real-world problems. The numerical results show that it is possible to find a maximum clique in polynomial time, using an algorithm based on semidefinite programming. We implement a primal-dual interior points algorithm to solve this problem based on semidefinite programming. The semidefinite relaxation of this problem can be solved in polynomial time.

Keywords: semidefinite programming, maximum clique problem, primal-dual interior point method, relaxation

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Authors: Shuyuan Lin, Zhaohui Huang, Mizi Fan

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In the majority of previous research into modelling large scale composite floor subjected to fire, the beam-to-column and beam-to-beam connections were assumed to behave either as pinned or rigid for simplicity, and the vertical shear and axial tension failures of the connection were not taken into account. We have recently developed robust two-noded connection models for modeling endplate and partial endplate steel connections under fire conditions. The main objective of this research is to systematically investigate the impact of the connections of protected beams, on the tensile membrane actions of supported floor slabs in which the failures of the connections, such as, axial tension, vertical shear and bending are accounted for. The models developed have very good numerical stability under a static solver condition, and can be used for large scale modelling of composite buildings in fire.

Keywords: fire, steel structure, component-based model, beam-to-column connections

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Authors: Rachid Marzoug, Noureddine Lakouari, Beatriz Castillo Téllez, Margarita Castillo Téllez, Gerardo Alberto Mejía Pérez

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This paper developed a two-lane cellular automata model to explain the relationship between car accidents at a signalized intersection and traffic-related parameters. It is found that the increase of the lane-changing probability P?ₕ? increases the risk of accidents, besides, the inflow α and the probability of accidents Pₐ? exhibit a nonlinear relationship. Furthermore, depending on the inflow, Pₐ? exhibits three different phases. The transition from phase I to phase II is of first (second) order when P?ₕ?=0 (P?ₕ?>0). However, the system exhibits a second (first) order transition from phase II to phase III when P?ₕ?=0 (P?ₕ?>0). In addition, when the inflow is not very high, the green light length of one road should be increased to improve road safety. Finally, simulation results show that the traffic at the intersection is safer adopting symmetric lane-changing rules than asymmetric ones.

Keywords: two-lane intersection, accidents, fatality risk, lane-changing, phase transition

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Authors: Amit Kumar Baghel, Sisir Kumar Nayak

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The proposed metamaterial design help to increase the radiation efficiency at 2.9 GHz by reducing the side and back lobes by making the phase difference of the waves emerging from the phase center of the horn antenna same after passing through metamaterial array. The unit cell of the metamaterial is having concentric ring structure made of copper of 0.035 mm thickness on both sides of FR4 sheet. The inner ring diameter is kept as 3 mm, and the outer ring diameters are changed according to the path and tramission phase difference of the unit cell from the phase center of the antenna in both the horizontal and vertical direction, i.e., in x- and y-axis. In this case, the ring radius varies from 3.19 mm to 6.99 mm with the respective S21 phase difference of -62.25° to -124.64°. The total phase difference can be calculated by adding the path difference of the respective unit cell in the array to the phase difference of S21. Taking one of the unit cell as the reference, the total phase difference between the reference unit cell and other cells must be integer multiple of 360°. The variation of transmission coefficient S21 with the ring radius is greater than -6 dB. The array having 5 x 5 unit cell is kept inside the pyramidal horn antenna (L X B X H = 295.451 x 384.233 x 298.66 mm3) at a distance of 36.68 mm from the waveguide throat. There is an improvement in side lobe level in E-plane by 14.6 dB when the array is used. The front to back lobe ration is increased by 1 dB by using the array. The proposed antenna with metamaterial array can be used in beam shaping for wireless power transfer applications.

Keywords: metamaterial, side lobe level, front to back ratio, beam forming

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Authors: Rezvan Ravanfar Haghighi, S. Chatterjee, Pratik Kumar, V. C. Vani, Priya Jagia, Sanjiv Sharma, Susama Rani Mandal, R. Lakshmy

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The dual energy computed tomography (DECT) aims at noting the HU(V) values for the sample at two different voltages V=V1, V2 and thus obtain the electron densities (ρe) and effective atomic number (Zeff) of the substance. In the present paper, we aim to obtain a numerical algorithm by which (ρe, Zeff) can be obtained from the HU(100) and HU(140) data, where V=100, 140 kVp. The idea is to use this inversion method to characterize and distinguish between the lipid and fibrous coronary artery plaques.With the idea to develop the inversion algorithm for low Zeff materials, as is the case with non calcified coronary artery plaque, we prepare aqueous samples whose calculated values of (ρe, Zeff) lie in the range (2.65×1023≤ ρe≤ 3.64×1023 per cc ) and (6.80≤ Zeff ≤ 8.90). We fill the phantom with these known samples and experimentally determine HU(100) and HU(140) for the same pixels. Knowing that the HU(V) values are related to the attenuation coefficient of the system, we present an algorithm by which the (ρe, Zeff) is calibrated with respect to (HU(100), HU(140)). The calibration is done with a known set of 20 samples; its accuracy is checked with a different set of 23 known samples. We find that the calibration gives the ρe with an accuracy of ± 4% while Zeff is found within ±1% of the actual value, the confidence being 95%.In this inversion method (ρe, Zeff) of the scanned sample can be found by eliminating the effects of the CT machine and also by ensuring that the determination of the two unknowns (ρe, Zeff) does not interfere with each other. It is found that this algorithm can be used for prediction of chemical characteristic (ρe, Zeff) of unknown scanned materials with 95% confidence level, by inversion of the DECT data.

Keywords: chemical composition, dual-energy computed tomography, inversion algorithm

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Authors: T. H. N. Nguyen, A. Khodan, M. Amamra, J-V. Vignes, A. Kanaev

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The ultraporous nanofibrous alumina (NOA, Al2O3·nH2O) was synthesized by oxidation of laminated aluminium plates through a liquid mercury-silver layer in a humid atmosphere ~80% at 25°C. The material has an extremely high purity (99%), porosity (90%) and specific area (300 m2/g). The subsequent annealing of raw NOA permits obtaining pure transition phase (γ and θ) nanostructured materials. In this combination, we report on chemical, structural and phase transformations of pure and modified NOA by an impregnation of trimethylethoxysilane (TMES) and tetraethoxysilane (TEOS) during thermal annealing in the temperature range between 20 and 1650°C. The mass density, specific area, average diameter and specific area are analysed. The 3D model of pure NOA monoliths and silica modified NOA is proposed, which successfully describes the evolution of specific area, mass density and phase transformations. Activation energies of the mass transport in two regimes of surface diffusion and bulk sintering were obtained based on this model. We conclude about a common origin of modifications of the NOA morphology, chemical composition and phase transition.

Keywords: nanostructured materials, alumina (Al₂O₃), morphology, phase transitions

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Authors: Touhami Tahenni

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Excessively wide cracks are harmful to the serviceability of reinforced concrete (RC) beams and may lead to durability problems in the longer term. They also reduce the rigidity of RC sections, rendering the tensile concrete ineffective structurally. To reduce the negative effects of cracks, steel fibers are added to concrete mixes in the same manner as aggregates. In the present work, steel fibers reinforced concrete (SFRC) beams, made of normal strength and high strength concretes, were tested in a four-point bending test using a digital image correlation technique. The beams had different volume fractions of fibres and different aspect ratios (fiber length/fiber diameter). The evaluation of flexural cracking widths was determined using Gom-Aramis software. The experimental crack widths were compared with theoretical values predicted by the technical document of Rilem TC 162-TDF. The model proposed in this document seems to be the only one that considers the efficiency of steel fibres in restraining the crack widths. However, the model of Rilem takes into account only the aspect ratio of steel fibres to predict the crack width of SFRC beams. It has been reported in several pieces of research that the contribution of steel fibres to the limitation of flexural cracking widths is based on three essential parameters namely, the volume fraction, the orientation and the aspect ratio of fibres. Referring to the literature on the flexural cracking behavior of SFRC beams and the experimental observations of the present work, a correction of the Rilem model by the introduction of these parameters in the formula is proposed. The crack widths predicted by the new empirical model were compared with the experimental results and assessed against other test data on SFRC beams taken from the literature. The modified Rilem model gives better results and is found more satisfactory in predicting the crack widths of fibres concrete.

Keywords: stee fibres, reinforced concrete, flexural cracking, tensile strength, crack width

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Authors: E. Mello, C. Ribellato, E. Mohamedelhassan

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This study investigated the improvement in concrete properties with addition of cellulose, steel, carbon and PET fibers. Each fiber was added at four percentages to the fresh concrete, which was moist-cured for 28-days and then tested for compressive, flexural and tensile strengths. Changes in strength and increases in cost were analyzed. Results showed that addition of cellulose caused a decrease between 9.8% and 16.4% in compressive strength. This range may be acceptable as cellulose fibers can significantly increase the concrete resistance to fire, and freezing and thawing cycles. Addition of steel fibers to concrete increased the compressive strength by up to 20%. Increases 121.5% and 80.7% were reported in tensile and flexural strengths respectively. Carbon fibers increased flexural and tensile strengths by up to 11% and 45%, respectively. Concrete strength properties decreased after the addition of PET fibers. Results showed that improvement in strength after addition of steel and carbon fibers may justify the extra cost of fibers.

Keywords: concrete, compressive strength, fibers, flexural strength, tensile strength

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Authors: Neriman Ozada, Ebrahim Karamian, Amirsalar Khandan, Sina Ghafoorpoor Yazdi

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Natural hydroxyapatite, NHA, coatings on the surface of 316 L stainless steel implants has been widely employed in order to achieve better osteoconductivity. For coating, the plasma spraying method is generally used because they ensure adhesion between the coating and the 316 L stainless steel (SS) surface. Some compounds such as zircon (ZrSiO4) is employed as an additive in an attempt to improve HA’s mechanical properties such as wear resistance and hardness. In this study wear resistance has been carried out in different chemical compositions of coating. Therefore, nanocomposites based on NHA containing of 0 wt.%, 5 wt.%, 10 wt.%, and 15 wt.% of zircon were used as a coating on the SS implants. The samples consisted of NHA, derived from calf heated at 850 °C for 3 h. The composite mixture was coated on SS by plasma spray method. The results were estimated using the scanning electron microscopy (SEM), X-ray diffraction (XRD) techniques were utilized to characterize the shape and size of NHA powder. Disc wear test and Vickers hardness were utilized to characterize the coated nanocomposite samples. The prepared NHA powder had nano-scale morphological structure with the mean crystallite size of 30-50 nm in diameter. The wear resistance are almost 320, 380, 415, and 395 m/g and hardness are approximately 376, 391, 420, 410 VHN in ceramic composite materials containing ZrSiO4. The results have been shown that the best wear resistance and hardness occurred in the sample coated by NHA/ZrSiO4 containing of 10 wt.% of zircon.

Keywords: zircon, 316 L stainless steel, wear resistance, orthopedic applications, plasma spray

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Authors: Gaurav Sancheti

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This study presents an impacting approach of Artificial Neural Networks (ANNs) in determining the quantity of High Tensile Steel (HTS) strands required in post-tensioned (PT) slabs. Various PT slab configurations were generated by varying the span and depth of the slab. For each of these slab configurations, quantity of required HTS strands were recorded. ANNs with backpropagation algorithm and varying architectures were developed and their performance was evaluated in terms of Mean Square Error (MSE). The recorded data for the quantity of HTS strands was used as a feeder database for training the developed ANNs. The networks were validated using various validation techniques. The results show that the proposed ANNs have a great potential with good prediction and generalization capability.

Keywords: artificial neural networks, back propagation, conceptual design, high tensile steel strands, post tensioned slabs, validation techniques

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Authors: Mostefa Mimoune

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Test results on concrete-filled steel tubular stub columns under axial compression are presented. The study was mainly focused on square hollow section SHS columns; 27 columns were tested. The main experimental parameters considered were the thickness of the tube, columns length and cross section sizes. Existing design codes and theoretical model were used to predict load-carrying capacities of composite section to compare the accuracy of the predictions by using the recommendations of DTR-BC (Algerian code), CSA (Canadian standard), AIJ, EC4, DBJ, AISC, BS and EC4. Experimental results indicate that the studied parameters have significant influence on both the compressive load capacity and the column failure mode. All codes used in the comparison, provide higher resistance compared to those of tests. Equation method has been suggested to evaluate the axial capacity of the composite section seem to be in agreement with tests.

Keywords: axial loading, composite section, concrete-filled steel tubes, square hollow section

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Authors: Yuksel Akinay, Fatih Hayat

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The influence of the alloying element on mechanical properties and micro structures of the Fe-22Mn-0.6C-0,6Si twinning induced plasticity (TWIP) steel were investigated at different temperatures. This composition was fabricated by a vacuum induction melting method. This steel was homogenized at 1200◦C for 8h. After heat treatment it was hot-rolled at 1100◦C to 6 mm thickness. The hot rolled plates were cold rolled to 3 mm and annealed at 700 800 and 900 °C for 60 and 150 minute and then air-cooled. X-ray diffractometry (XRD), optic microscope and field emission scanning electron microscope (FESEM), hardness and tensile tests were used to analyse the relationship between mechanical properties and micro structure after annealing process. The results show that, the excellent mechanical properties were obtained after heat treatment process. The tensile strength of material was decreased and the ductility of material was improved with increasing annealing temperature. Ni element were increased the mechanical resistance of specimens and because of carbide precipitation the hardness of specimen annealed at 700 C is higher than others.

Keywords: high manganese, heat treatment, SEM, XRD, cold-rolling

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Authors: A. Rabin, G. Mazor, I. Ladizhenski, R. Shneck, Z.

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The hardness and hardenability of AISI D2 cold work tool steel with conventional quenching (CQ), deep cryogenic quenching (DCQ) and rapid deep cryogenic quenching heat treatments caused by temporary porous coating based on magnesium sulfate was investigated. Each of the cooling processes was examined from the perspective of the full process efficiency, heat flux in the austenite-martensite transformation range followed by characterization of the temporary porous layer made of magnesium sulfate using confocal laser scanning microscopy (CLSM), surface and core hardness and hardenability using Vickr’s hardness technique. The results show that the cooling rate (CR) at the austenite-martensite transformation range have a high influence on the hardness of the studied steel.

Keywords: AISI D2, controllable cooling, magnesium sulfate coating, rapid cryogenic heat treatment, temporary porous layer

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Authors: M. H. Kazemi, D. Salac

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A semi-implicit phase field method for droplet evolution is proposed. Using the phase field Cahn-Hilliard equation, we are able to track the interface in multiphase flow. The idea of a semi-implicit finite difference scheme is reviewed and employed to solve two nonlinear equations, including the Navier-Stokes and the Cahn-Hilliard equations. The use of a semi-implicit method allows us to have larger time steps compared to explicit schemes. The governing equations are coupled and then solved by a GMRES solver (generalized minimal residual method) using modified Gram-Schmidt orthogonalization. To show the validity of the method, we apply the method to the simulation of a rising droplet, a leaky dielectric drop and the coalescence of drops. The numerical solutions to the phase field model match well with existing solutions over a defined range of variables.

Keywords: coalescence, leaky dielectric, numerical method, phase field, rising droplet, semi-implicit method

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Authors: Jakub Bartus, Jaroslav Odrobinak

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In general, composite steel and concrete structures present an effective structural solution utilizing the full potential of both materials. As they have numerous advantages on the construction side, they can greatly reduce the overall cost of construction, which has been the main objective of the last decade, highlighted by the current economic and social crisis. The study represents not only an analysis of composite beams’ behavior having web openings but emphasizes the influence of these openings on the total strain distribution at the level of the steel bottom flange as well. The major investigation was focused on a change in structural performance with respect to various layouts of openings. Examining this structural modification, an improvement of load carrying capacity of composite beams was a prime objective. The study is divided into analytical and numerical parts. The analytical part served as an initial step into the design process of composite beam samples, in which optimal dimensions and specific levels of utilization in individual stress states were taken into account. The numerical part covered the discretization of the preset structural issue in the form of a finite element (FE) model using beam and shell elements accounting for material non–linearities. As an outcome, several conclusions were drawn describing and explaining the effect of web opening presence on the structural performance of composite beams.

Keywords: beam, steel flange, total strain, web opening

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Authors: H. Gokdemir

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All structures are subject to vertical and lateral loads. Under these loads, structures make deformations and deformation values of structural elements mustn't exceed their capacity for structural stability. Especially, lateral loads cause critical deformations because of their random directions and magnitudes. Wind load is one of the lateral loads which can act in any direction and any magnitude. Although wind has nearly no effect on reinforced concrete structures, it must be considered for steel structures, roof systems and slender structures like minarets. Therefore, every structure must be able to resist wind loads acting parallel and perpendicular to any side. One of the effective methods for resisting lateral loads is assembling cross steel elements between columns which are called as wind bracing. These cross elements increases lateral rigidity of a structure and prevent exceeding of deformation capacity of the structural system. So, this means cross elements are also effective in resisting earthquake loads too. In this paper; Effects of wind bracing to earthquake resistance of structures are studied. Structure models (with and without wind bracing) are generated and these models are solved under both earthquake and wind loads with different seismic zone parameters. It is concluded by the calculations that; in low-seismic risk zones, wind bracing can easily resist earthquake loads and no additional reinforcement for earthquake loads is necessary. Similarly; in high-seismic risk zones, earthquake cross elements resist wind loads too.

Keywords: wind bracings, earthquake, steel structures, vertical and lateral loads

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Authors: Farhad Abbas Gandomkar, Mona Danesh

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This paper aims to determine Fundamental Natural Frequency (FNF) of a structural composite floor system known as Chromite. To achieve this purpose, FNFs of studied panels are determined by development of Finite Element Models (FEMs) in ABAQUS program. American Institute of Steel Construction (AISC) code in Steel Design Guide Series 11, presents a fundamental formula to calculate FNF of a steel framed floor system. This formula has been used to verify results of the FEMs. The variability in the FNF of the studied system under various parameters such as dimensions of floor, boundary conditions, rigidity of main and secondary beams around the floor, thickness of concrete slab, height of composite joists, distance between composite joists, thickness of top and bottom flanges of the open web steel joists, and adding tie beam perpendicular on the composite joists, is determined. The results show that changing in dimensions of the system, its boundary conditions, rigidity of main beam, and also adding tie beam, significant changes the FNF of the system up to 452.9%, 50.8%, -52.2%, %52.6%, respectively. In addition, increasing thickness of concrete slab increases the FNF of the system up to 10.8%. Furthermore, the results demonstrate that variation in rigidity of secondary beam, height of composite joist, and distance between composite joists, and thickness of top and bottom flanges of open web steel joists insignificant changes the FNF of the studied system up to -0.02%, -3%, -6.1%, and 0.96%, respectively. Finally, the results of this study help designer predict occurrence of resonance, comfortableness, and design criteria of the studied system.

Keywords: Fundamental Natural Frequency, Chromite Composite Floor System, Finite Element Method, low and high frequency floors, Comfortableness, resonance.

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Authors: Marzie Shahini, Alireza Bagheri Sabbagh, Rasoul Mirghaderi, Paul C. Davidson

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The focus of this paper is to incorporating the slotted bolted connection into the cold-formed steel (CFS) beams with aim of increasing inelastic bending capacity through bolt slip. An extensive finite element analysis was conducted on the through plate CFS bolted connections which are equipped with the slotted hole. The studied parameters in this paper included the following: CFS beam section geometry, the value of slip force, CFS beam thickness. The numerical results indicate that CFS slotted bolted connection exhibit higher inelastic capacity in terms of ductility compare to connection with standards holes. Moreover, the effect of slip force was analysed by comparing the moment-rotation curves of different models with different slip force value. As a result, as the slip force became lower, there was a tendency for the plastic strain to extend from the CFS member to the connection region.

Keywords: slip-critical bolted connection, inelastic capacity, slotted holes, cold-formed steel, bolt slippage, slip force

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Authors: Samar Raffoul, Martin Heywood, Dimitrios Moutaftsis, Michael Rowell

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This paper comprises an experimental investigation into the structural performance of cold formed steel (CFS) and timber board composite floor systems. The tests include a series of small-scale pushout tests and full-scale bending tests carried out using a refined loading system to simulate uniformly distributed constant load. The influence of connection details (screw spacing and adhesives) on floor performance was investigated. The results are then compared to predictions from relevant existing models for composite floor systems. The results of this research demonstrate the significant benefits of considering the composite action of the boards in floor design. Depending on connection detail, an increase in flexural stiffness of up to 40% was observed in the floor system, when compared to designing joists individually.

Keywords: cold formed steel joists, composite action, flooring systems, shear connection

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Authors: Juzar Vohra, Ravish Malhotra, Tim Pasang, Mana Azizi, Yuan Tao, Masami Mizutani

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In this paper, dissimilar welding of titanium to stainless steels is reported. Laser Beam Welding (LBW) and Gas Tungsten Arc Welding (GTAW) were employed to join CPTi to SS304. The welds were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). FeTi, Ti2Cr and Fe2Ti dendrites are formed along with beta phase titanium matrix. The hardness values of these phases are high which makes them brittle and leading to cracking along the weld pool. However, it is believed that cracking, hence, fracturing of this weld joint is largely due to the difference in thermal properties of the two alloys.

Keywords: dissimilar metals, fusion welding, intermetallics, brittle

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Authors: Ioannis Binas, Marios Moschakis

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Electrical faults in transmission and distribution networks can have great impact on the electrical equipment used. Fault effects depend on the characteristics of the fault as well as the network itself. It is important to anticipate the network’s behavior during faults when planning a new equipment installation, as well as troubleshooting. Moreover, working backwards, we could be able to estimate the characteristics of the fault when checking the perceived effects. Different transformer winding connections dominantly used in the Greek power transfer and distribution networks and the effects of 1-phase to neutral, phase-to-phase, 2-phases to neutral and 3-phase faults on different locations of the network were simulated in order to present voltage sag characteristics. The study was performed on a generic network with three steps down transformers on two voltage level buses (one 150 kV/20 kV transformer and two 20 kV/0.4 kV). We found that during faults, there are significant changes both on voltage magnitudes and on phase angles. The simulations and short-circuit analysis were performed using the PSCAD simulation package. This paper presents voltage characteristics calculated for the simulated network, with different approaches on the transformer winding connections during symmetrical and asymmetrical faults on various locations.

Keywords: Phase angle shift, power quality, transformer winding connections, voltage sag propagation

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Authors: Mohammad Befkin, Alireza Momtaz

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Structural design is the challenging aspect of every project due to limitations in dimensions, functionality of the structure, and more importantly, the allocated budget for construction. This research study aims to investigate the optimized design for three steel moment frame buildings with different number of stories using genetic algorithm code. The number and length of spans, and height of each floor were constant in all three buildings. The design of structures are carried out according to AISC code within the provisions of plastic design with allowable stress values. Genetic code for optimization is produced using MATLAB program, while buildings modeled in Opensees program and connected to the MATLAB code to perform iterations in optimization steps. In the end designs resulted from genetic algorithm code were compared with the analysis of buildings in ETABS program. The results demonstrated that suggested structural elements by the code utilize their full capacity, indicating the desirable efficiency of produced code.

Keywords: genetic algorithm, structural analysis, steel moment frame, structural design

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Authors: A. Mostafa

Abstract:

This paper presents a numerical study on determination of ballistic limit velocity (V₅₀) of stainless steel 304 (SS 304) used in manufacturing security screens. The simulated ballistic impact tests were conducted on clamped sheets with different thicknesses using ABAQUS/Explicit nonlinear finite element (FE) package. The ballistic limit velocity was determined using three approaches, namely: numerical tests based on material properties, FE calculated residual velocities and FE calculated residual energies. Johnson-Cook plasticity and failure criterion were utilized to simulate the dynamic behaviour of the SS 304 under various strain rates, while the well-known Lambert-Jonas equation was used for the data regression for the residual velocity and energy model. Good agreement between the investigated numerical methods was achieved. Additionally, the dependence of the ballistic limit velocity on the sheet thickness was observed. The proposed approaches present viable and cost-effective assessment methods of the ballistic performance of SS 304, which will support the development of robust security screen systems.

Keywords: ballistic velocity, stainless steel, numerical approaches, security screen

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Authors: Alicia Kamischke, Souhail Elhouar, Yasser Khodair

Abstract:

The American Institute of Steel Construction (AISC) Specification (360-10) provides equations for calculating the capacity of a W-shaped steel member to resist concentrated forces applied to its flange. In the case of flange local bending, the capacity equations were primarily formulated for an interior point along the member, which is defined to be at a distance larger than ten flange thicknesses away from the member’s end. When a concentrated load is applied within ten flange thicknesses from the member’s end, AISC requires a fifty percent reduction to be applied to the flange bending capacity. This reduction, however, is not supported by any research. In this study, finite element modeling is used to investigate the actual reduction in capacity near the end of such a steel member. The results indicate that the AISC equation for flange local bending is quite conservative for forces applied at less than ten flange thicknesses from the member’s end and a new equation is suggested for the evaluation of available flange local bending capacity within that distance.

Keywords: flange local bending, concentrated forces, column, flange capacity

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Authors: Ravi V. Joat, Pravin S. Bodke, Shradha S. Binani, S. S. Wasnik

Abstract:

A phase diagram of the Ag2SO4 - CaSO4 (Silver sulphate – Calcium Sulphate) binaries system using conductivity, XRD (X-Ray Diffraction Technique) and DTA (Differential Thermal Analysis) data is constructed. The eutectic reaction (liquid -» a-Ag2SO4 + CaSO4) is observed at 10 mole% CaSO4 and 645°C. Room temperature solid solubility limit up to 5.27 mole % of Ca 2+ in Ag2SO4 is set using X-ray powder diffraction and scanning electron microscopy results. All compositions beyond this limit are two-phase mixtures below and above the transition temperature (≈ 416°C). The bulk conductivity, obtained following complex impedance spectroscopy, is found decreasing with increase in CaSO4 content. Amongst other binary compositions, the 80AgSO4-20CaSO4 gave improved sinterability/packing density.

Keywords: phase diagram, Ag2SO4-CaSO4 binaries system, conductivity, XRD, DTA

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Authors: Aarushi Agarwal, Tara Singh, I.L Singh, Anju Lata Singh, Trayambak Tiwari

Abstract:

Simple discrimination in near absence of attention has been widely observed. Dual-task studies with natural scenes studies have been claimed as being preattentive in nature that facilitated categorization simultaneously with the attentional demanding task. So in this study, multiple images at the periphery are presented, initiating parallel processing in near absence of attention. For the central demanding task rotated letters were presented in both conditions, while in periphery natural and animal images were presented. To understand the breakpoint of ability to perform in near absence of attention one, two and three peripheral images were presented simultaneously with central task and subjects had to respond when all belong to the same category. Individual participant performance did not show a significant difference in both conditions central and peripheral task when the single peripheral image was shown. In case of two images high-level parallel processing could take place with little attentional resources. The eye tracking results supports the evidence as no major saccade was made in a large number of trials. Three image presentations proved to be a breaking point of the capacities to perform outside attentional assistance as participants showed a confused eye gaze pattern which failed to make the natural and animal image discriminations. Thus, we can conclude attention and awareness being independent mechanisms having limited capacities.

Keywords: attention, dual task pardigm, parallel processing, break point, saccade

Procedia PDF Downloads 219