Sharif Digital Repository

In recent years, parallel to the development of industrial, the use of organic solvents and the environmental pollution caused by their increasing, more attention to remove these contaminants growing. Among the various absorbents to absorb pollutants from the environment, iron oxide nanoparticles have many applications in absorption and removal of environmental pollutions due to their high specific surface area, magnetic properties and ease of separation. The aim of this research is synthesis of a magnetic gel for absorption of organic solvents which in its structure magnetic nanoparticle and hydrophobic monomer is used. The most important advantages are the ease of isolation of the desired... 

Nowadays adhesives with the development of technology and the numerous benefits they have, are becoming a replacement for traditional joining methods in industries like electronics, automotive, aerospace, and naval. That’s why the need for studying the fracture behavior of adhesive joints becomes vital. So far, many engineers and designers are trying to investigate the behavior of adhesive joints in different conditions that these joints actually deal with. Also, finding solutions to predict the behavior of adhesive joints is the researchers’ other concern. The purpose of this research is to find the effect of factors that are less focused in the literature, on the fracture of adhesive... 

Nowadays adhesives with the development of technology and the numerous benefits they have, are becoming a replacement for traditional joining methods in industries like electronics, automotive, aerospace, and naval. That’s why the need for studying the fracture behavior of adhesive joints becomes vital. So far, many engineers and designers are trying to investigate the behavior of adhesive joints in different conditions that these joints actually deal with. Also, finding solutions to predict the behavior of adhesive joints is the researchers’ other concern. The purpose of this research is to find the effect of factors that are less focused in the literature, on the fracture of adhesive... 

Auxetic materials have a negative Poisson ratio (NPR), which is their most distinguishable characteristic as compared to regular materials. Test specimens were made of conventional polyurethane (PU) foams according to ASTM ; then, with a thermo-mechanical process, the foam was converted to auxetic PU foam. The reproducibility of specimens' fabrication was checked with CoV= for the final foam thickness. With regard to the fact that changing loading conditions can vary Poisson's ratio, in this study, the variations occurred in Poisson's ratio due to changing loading conditions are investigated. The applied strain and strain rate were altered in experiments and statistical analysis was... 

In the past, lead-based solders with homogeneous and isotropic behavior were used in microelectronic packages. But today, due to the environmental concerns of lead, lead-free solders have been developed, which consist of a high weight percentage (more than 90%) of tin. Tin crystal shows significant anisotropic behavior, which leads to an anisotropic joint response in miniature solder joints with a small number of grains. In the first part of this research, using the crystal plasticity model, the anisotropic plastic response of tin grain was extracted from bulk solder stress-strain curve, then it was implemented in Abaqus software using built-in Hill's anisotropic plasticity model to consider... 

Single lap-shear (SLS) specimens of 2.54, 6.35 and 12.7 mm long SAC305 solder joints were prepared with three different adherend thicknesses. The fracture force was measured at a shear strain rate of 0.01 s-1 for different geometries in the lap-shear configuration in which mode ІІ loading is established. Elastic-plastic fracture mechanics (EPFM) theory was considered to find the energy dissipated in each case using a finite element model (FEM). The fracture energy was found by cohesive zone modeling (CZM) using pre-defined parameters. Both 2D and 3D models were used to explain the variations of fracture energy by evaluating the effective factors that demonstrated the level of constraints on... 

Double cantilever beam (DCB) specimens were prepared according to standard surface mount technology (SMT). The samples were stored inside an environmental chamber at two different relative humidity values (i.e. 40 or 100%) for either 2 or 4 hours. Then they were aged at 25ºC, 75ºC or 125℃ for the same time. Finally, after being cooled to room temperature, fracture tests were performed under mode-I loading conditions at a strain rate of 0.03 s-1 at room temperature. Storage time did not have a significant effect on the fracture behavior. The fracture load and energy of the solder joints decreased significantly when the temperature was increased from 25 to 75℃. By further increase in the... 

In this investigation, the mode I fracture behavior of an epoxy adhesive joint has been investigated to probe the combined effects of adherend Young's modulus and thickness, strain rate, and adhesive length. Experimental fracture testing was conducted on double-cantilever beam (DCB) specimens under three various strain rate thresholds, namely, quasi-static (0.0005 s-1), low (0.015 s-1), and intermediate (0.5 s-1). The specimens were constructed with varying adherend materials (i.e., copper, aluminum), thickness (12-20 mm), and adhesive lengths (25-75 mm). The fracture load was measured in each experiment, and the critical strain energy release rate, JCi, was calculated via a finite element... 

The present study examines the mechanical properties of auxetic stents with various types of structures. Geometries was parametrically modeled and the design of experiments (DOE) was developed by defining the elastic properties of the stents and using the response surface method (RSM). Finite element (FE) analysis was performed in order to find a polynomial relationship between the geometric parameters as inputs and the elastic parameters as the outputs. Then, the optimal stent was obtained in terms of elasticity parameters by using RSM and NSGA-II methods and the two-dimensional Pareto front was plotted. For instance, the optimal parameters of the Re-entrant stent including flexural... 

Disorders of the lumbar spine are prevalent within the realm of musculoskeletal issues, emphasizing the importance of investigating contributing factors. This research focuses on assessing how flexible footwear influences the kinematics and dynamics of the vertebral column during drop vertical jump. The study involves mechanical tests on various footwear types, including simple, flexible and re entrant shoes with differing levels of rigidity. Bending tests were performed on simple and flexible shoes with hardness of 50 Asker C and flexible shoes with hardness of 40 Asker C. Additionally, compression tests were carried out on all soles at two different angles. The Bending tests revealed that,... 

Cardiovascular disease is one of the most leading causes of death in the world and one of the common methods for treating such diseases is replacing damaged blood vessels with artificial ones. Electrospinning, which is a method of producing polymer fibers, is one of the best and common methods of producing synthetic vessels. The first goal in this study was to create a suitable structure for fiber production; therefore, first, an electrospinning device and environmental chamber were designed and built. Then, the effect of alternative and uniform flow on the diameter and structure of the fibers was investigated using 15% wt. Polycaprolactone solution. The results of this study showed that the... 

With the increasing use of electronic components in various dimensions, the reliability of solder joints has been widely considered. Predicting the failure force of these connections in various configurations and under different loads has recently been the subject of scientific articles. The aim of this research is to establish a relationship between the parameters of the cohesive zone model and the damage parameter of joints. Initially, 13 unloaded specimens were pulled by a hydraulic tensile machine at a strain rate of 0.0001/sec to obtain the breaking force. By calculating the solder area, an average breaking stress of 49.8 MPa was obtained. To investigate the effect of fatigue loading on...