Sharif Digital Repository

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2 (Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment  

In this investigation, a novel numerical method is proposed for materials selection. This method is based on the well known weighting factor approach while combining non-linear normalization with a modified digital logic method. The proposed mathematical functions and their applicability to the materials selection process is verified by examining two case studies in mechanical design and comparing the results with those obtained from the classical weighted property method. It is concluded that the new approach is capable of providing more reasonable selections as opposed to those obtained from the existing method. © 2005 Elsevier Ltd. All rights reserved  

The impact behavior of aluminum/epoxy laminates was studied by changing the number of layers and the interface strength. It should be noted that although the overall thickness did not changed, the individual layers decreased in thickness when the number of layers increased. The results indicate that the impact resistance of the laminate increases with the number of layers, while the interface strength has a less pronounced influence (50%) on the impact resistance of the laminate. It is also deducted that if the ratio of layer thickness to plastic zone size is smaller than or equal to 1, the impact behavior of the laminates is sensitive to the interface strength. © 2008 Elsevier Ltd. All... 

The effects of Sr additions, heat treatment (T4 and T6), and multi-directional forging on the microstructural evolution, mechanical properties and biodegradability of Mg-4Zn-xSr alloys were investigated. Corrosion behavior of the alloys was evaluated by the polarization and hydrogen evolution tests. Shear punch and hardness tests were employed to determine the mechanical properties. It was found that mechanical properties and corrosion resistance of the as-cast Mg-4Zn alloy increased by 0.3 wt% Sr addition. However, further increasing the Sr content not only did not improve the mechanical strength, but also had detrimental effects on the corrosion resistance, due to the increased size and... 

Tearing energy of AA5010 aluminum alloy sheets has been studied by the single tensile testing (STT) and multiple tensile testing (MTT) methods. The total energy required to tear the specimens was assumed to be composed of two components; one associated with uniform plastic deformation, which occurs in the work-hardening range of the material, and the other with post-uniform deformation and tearing which leads to the failure of the specimens. In the STT method, tearing energy was calculated by subtracting the plastic deformation energy, dissipated in the uniform deformation range, from the total energy absorbed by a single specimen during tension. In the MTT method, which uses different... 

Laminated composites are made using different routes, including adhesive bonding. In this investigation, Aluminum layers are bonded together using epoxy adhesive (neat, rubber-modified and filled-epoxy). In phase one of this investigation, the influence of number of layers and adhesive ductility have been studied on dynamic behavior of composites. The results of impact behavior of laminates indicate that the impact energy increases with the number of layers. Also, it can be concluded that there is much more sensitivity of the impact energy of the composite to the number of the layers than that to the adhesive composition. © 2004 Elsevier B.V. All rights reserved  

The effects of zinc content (2 and 4 wt%), heat treatment (solution-Treated and T6), as well as hot deformation (extrusion and multi-directional forging (MDF)) on the microstructure, mechanical and degradation behavior of Mg-Zn alloys were studied. As the result of microstructure refinement, solid solution and precipitate strengthening (formation of MgZn second phases), the strength of pure Mg was increased after Zn addition. Solution treatment of the Mg-4Zn alloy resulted in 16% softening due to the dissolution of the MgZn second phases and also grain growth, while aging treatment increased the strength value by 8% in comparison to the as-cast material because of the formation of the fine... 

The effects of Sr additions (0.3, 0.6 and 0.9 wt%) on the microstructural evolution, thermal stability, and mechanical properties of a cast Mg–4Zn alloy were investigated. The extent of grain growth and stability of the intermetallic compounds were studied by optical and scanning electron microscopy (SEM), respectively. Mechanical properties of the studied alloys were evaluated by shear punch testing (SPT) method and also the hardness test. Hardness and shear strength of the base alloy were increased by Sr additions in the as-cast condition, due to the grain refinement effect of Sr and also presence of the Sr-containing Mg17Sr2 and Mg70Zn25Sr5 precipitates. However, the optimum amount of Sr... 

The model introduced in this article for neural system describes both physiological and psychological concepts of neural system and is based on the models of individual elements of the system. This model includes psychological characteristics such as; perception, prediction, learning and response planning, and physiological features such as; sensory analysis, memory and motor execution. The model is designed in such a way that it describes the performance of the neural system for a key-pressing test. The key-pressing experiment consists of a screen with numbers from 1 to 9, which is shown to the operator where one of the numbers is specified by a special color and the operator is to push the... 

Material selection for mechanical designs is an important task. Different approaches have been proposed to fulfill this job, so far. However, most of them work well with only quantitatively measurable properties of materials. Also, due to a wide range of materials available, the selection space finds a fuzzy characteristic. Therefore, here a simplified fuzzy logic approach is introduced to provide a powerful tool for easy dealing with the qualitative properties of materials and the corresponding fuzzy space. With this approach the volume of mathematics involved with the conventional methods reduces, considerably. The results show an excellent match with the Manshadi's method. © 2008 Elsevier... 

Hydrothermal method was applied to create a protective coating on the Mg–4Zn–0.3Sr alloy, using de-ionized water (as precursor) for different synthesizing times of 3, 4, 5, and 6 h. XRD and EDS line-scan confirmed formation of Mg(OH)2 coating. Based on the surface morphological appearance, 5 h coating time at 160 °C was found to be the optimum condition. The corrosion current of 2.58 µA/cm2 in the uncoated sample decreased to 0.48 µA/cm2 in the coated condition. Also, the cytotoxicity assessments using Alamar blue test showed that the cell viability and cell attachment to the formed Mg(OH)2 coating are more pronounced in comparison with the uncoated alloy. © 2022 Elsevier B.V  

Coating is an effective approach to address the high corrosion rate of biodegradable Mg alloys, as their main challenge toward their extensive use. In this regard, it was tried to control the degradation process of an Mg-4Zn alloy by Ca addition, equal channel angular pressing (ECAP), and hydrothermal coating. The obtained results indicated that excellent grain refinement induced by Ca incorporation and ECAP simultaneously, improved both mechanical strength and corrosion resistance of the Mg-based substrate. The achieved grain refinement resulted in a thicker, more compact and integrated coating, where the ECAP-processed Mg-4Zn-0.5Ca alloy exhibited the best coating quality with no... 

This study investigated the effects of solution heat treatment and multi-directional forging (MDF) on the microstructure, mechanical, and corrosion properties of an Mg–2Zn–0.2Ag alloy. Microstructural characterization by field emission scanning electron microscopy indicated that the as-cast material consists of some MgZn2 and Ag-rich MgZn precipitates. These silver-rich MgZn precipitates were entirely and partially dissolved after the solution treatment and MDF, respectively. In addition, the grain size of the as-cast alloy increased by 86% and decreased by 43% after solution heat treatment and MDF, respectively. The ultimate shear strength of the as-cast material increased by 25% and... 

Four 5-, 10-, 20- and 30-story moment frames, representing low-, mid-, and two high-rise structures, were subjected to a great number of idealized directivity pulses. The amplitudes and periods of pulses vary from 0.02 g to 1.0 g and 0.5 to 12 sec, respectively. Over 1400 nonlinear dynamic analyses of low- to high-rise moment frames were performed which were feasible through using modified fish-bone model. The distribution of interstory drift along the height was studied and two applied contours were proposed: (i) the maximum interstory drift contour, and (ii) the critical story contour. These contours were demonstrated versus the ratio of natural period of the structure to the pulse period... 

In this article singular points of a parallel manipulator are obtained based on a novel geometrical method. Here we introduce the constrained plain method (CPM) and some of its application in parallel mechanism. Given the definition of constraint plane (CP) and infinite constraint plane (ICP) the dependency conditions of constraints is achieved with the use of a new theorem based on the Ceva geometrical theorem. The direction of angular velocity of a body is achieved by having three ICPs with the use of another theorem. Finally, with the use of the above two novel theorems singularities of the 3UPF_PU mechanism are obtained. It should be emphasized that this method is completely geometrical,... 

An analytical model is proposed to study the effect of particle size on melting enthalpy and entropy of metallic nanoparticles (NPs). The Mott's and Regel's equations for melting entropy in the combination of core average coordination number (CAC) and surface average coordination number (SAC) of freestanding NPs are considered. Clusters of icosahedral (IC), body centered cubic (BCC), and body centered tetragonal (BCT) structure without any vacancies and defects are modeled. Using the variable coordination number made this model to be in good agreement with experimental and molecular dynamic (MD) results of different crystal structures. The model predicts melting entropy and enthalpy of... 

Grinding is widely used for manufacturing of components that require fine surface finish and good dimensional accuracy. In this study a thermo-mechanical finite element analysis is conducted to find out how grinding parameters can affect temperature and residual stress distribution in the workpiece. Results of parametric study presented in this work indicate, by carefully selecting the grinding parameters, minimum thermal and mechanical damage can be achieved. Higher workpiece velocities produce higher surface residual stress. By increasing depths of cut, depth of tensile residual stresses increases. Convection heat coefficient does not have any considerable effect on surface residual stress... 

Adaptive Noise Cancellation (ANC) is a well-known technique for background noise reduction in automobile and vehicular environments. The noise fields in automobile and other vehicle interior obey the diffuse noise field model closely. On the other hand, the ANC does not provide sufficient noise reduction in the diffuse noise fields. In this paper, a new multistage post-filter is designed for ANC as a solution to diffuse noise conditions. The designed post-filter is a single channel Linear Prediction (LP) based speech enhancement system. The LP is performed by an adaptive lattice filter and attempts to extract speech components by using intermediate ANC signals. The post-filter has no... 

Self-Compacting Concrete (SCC) is a unique type of concrete that can flow and fill spaces without the need for vibrating compaction, resulting in a dense and uniform material. This article focuses on estimating the compressive strength of SCC utilizing Artificial Neural Networks. Specifically, the study employs multilayer perceptrons with back-propagation learning algorithms, which are commonly used in various problem-solving scenarios. The study covers essential components such as structure, algorithm, data preprocessing, over-fitting prevention, and sensitivity analysis in MLPs. The input variables considered in the research include water, fine aggregate, super-plasticizer, fly ash, coarse...