Sharif Digital Repository

The stirred tank is one of the oldest device that widely used in different industrial. a special kind of stirred tank that clled bioreactor refer to any device which supplies required biological, biochemical and biomechanical engineered product. Since the aim of bioreactor is produce of desired biological product, it is essential to accurate monitoring internal and external transfer of nutrient, heat transfer, fluid velocity, Strain stress and medium PH. good design and application of bioreactor depend on product, organism, conditions for produce desired product and scale of produce. also cost of capital and function cost are important in bioreactor design. one of the most important... 

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... 

Studying the behavior of materials at high strain rate is necessary for design and analysis of structures subjected to impact loading. Therefore, design and construction of apparatuses that enable us for testing various materials under impact loading is very important. The split Hopkinson pressure bar test -one of the most important impact tests- is utilized for dynamic loading at constant strain rates ranging from 100 to 10000 1/s.
In this thesis, first we explain about the behavior of materials at high strain rates and then focus on the behavior of polymers -that are widely used in different industries- under impact loading. Also, basic concepts of polymeric Hopkinson pressure bar and... 

The stiffness rate of the 300 series austenitic stainless steel has long been known to depend on the stability of the austenite and its susceptibility to martensite formation. In this project, the cold deformation of austenitic stainless steel (304L) and the occurrence of martensite deformation during it are studied. Experimental cold rolling experiments under different strain velocities and initial temperatures in the range of -10° C to 25° C; Performed and microstructure, mechanical properties and percentage of martensite generated in rolled steel are determined and evaluated employing different testing techniques. mathematical modeling of cold rolling operation is also performed using... 

Amount of strain has been always considered as the primary parameter affecting the microstructural and strength evolutions during Severe Plastic Deformation (SPD). However, these evolutions unavoidably saturate in large strains under deformation with constant conditions, i.e. constant deformation temperature, strain rate and strain path. In this study, effects of these factors on the microstructural and flow behavior of Ultra-Fine Grain (UFG) aluminum (AA 1050 and AA 5052) processed by Accumulative Roll-Bonding (ARB) are investigated. The flow behavior and its time-dependent aspect are evaluated up to large strains by Plane Strain Compression (PSC) and Stress Relaxation (SR) tests. ... 

Stress whitening is a type of discoloration that can occur in variety of polymers used in automotive and household industries. The current research tries to investigate the effective microstructural parameters such as strain rate, rubber second phase, and branched polypropylene (PP) on the stress whitening in polypropylene in order to propose toughed PP blends with limited stress whitening. It is shown that increasing the strain rate in tensile test results in formation of more visible whitened area within the plastically deformed zone. This is the consequence of further growth of micro-voids at higher strain rates. The results are in accordance with the Mie scattering concepts. Besides, the... 

So far, a lot of research has been done on the hot behavior of different alloys; These studies have generally been performed using tensile, compression and torsion tests and isothermal conditions, which have greatly contributed to the understanding of the mechanisms of deformation at high temperatures. Due to the fact that in real deformation processes, it is less common for the material to experience isothermal conditions during deformation, so in this project, the aim is to investigate the behavior of 2024 aluminum-alloy in non-isothermal hot compression test. In this regard, non-isothermal hot pressure test was performed from 300℃ to 600℃ و temperature range and at different deformation... 

Sheet metal forming is widely being used in the production fields. Improve of quality, production rate and efficiency of this process are important. Temperature and strain rate are the most effective parameters on the formability of sheet metals. Utilizing forming limit diagram is the most common method of determining the formability. In this study, forming limit diagram of AA3003 aluminum alloy is extracted in different temperatures and velocities using simulation of Nakazima test with Abaqus finite element software. The simulation results, indicate that at 250°C formability is about 3 times more than that at room temperature. increasing the velocity of the punch in low strain rates causes... 

Strain rate dependence of plastic yield and failure properties displayed by most metals affects energies, forces and forming limits involved in high speed forming processes. This paper investigates the influence of the strain rate on the forming properties of some industrial sheet metals used in Automotive and Aerospace industries. First, Split Hopkinson Tensile Bar (SHTB) experiments are carried out to determine the influence of the strain rate on the materials’ stress-strain curves. Then, the SHTB results are used to model the constitutive behaviour of the metal sheets using the phenomenological Johnson-Cook (JC) and Voce models. Finally, forming limit diagrams (FLDs) are calculated using... 

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... 

In most of the engineering applications, the mechanical behavior of materials in high strain rate deformations differs from their behavior in quasi-static deformations. In some engineering problems like impact loading on structures, metal forming and explosive forming, the range of strain rate is about . Taylor impact test is one of the experiments used for characterizing the dynamic behavior of materials in high strain rate deformations. In the Taylor impact test a rigid cylindrical projectile is impacted normally onto a hard and massive surface (anvil), the projectile deforms by mushrooming at the impact end. With plastic wave propagation analysis, the plastic deformation of projectile is... 

The orientations which predominate in a final orientation distribution resulted from a specific deformation mode are the ideal orientations. There is a set of ideal orientations for each of crystal structures under a predefined mode of deformation. Ideal orientations are one of the material characteristics in the applied mode of deformation. The material texture strongly influences its final properties and affects the material behaviour in the subsequent forming processes.
In this project, final texture of 1010 steel sheet resulted from simple tension mode of deformation is investigated computationally and experimentally. The calculated texture based on the simulation procedure is... 

Wide applications of elastomeric (rubber-like) materials have led to significant interest of researchers to these materials. Elastomers as a great category of polymeric materials,posses specific properties such as large elastic deformations and energy absorption which make them suitable for aerospace and automotive applications as well as shock and vibration absorbers.In this thesis, an exponential strain energy function (SEF) has been proposed for elastomers which well reproduces the mechanical behavior of these materials and also the material parameters are related to the physical parameters of the material molecular network. This SEF has been concluded from a relation proposed for the... 

In this study, multi directional forging as a severe plastic deformation method is applied on pure aluminum at the different strain of 0.5, 1.5, 2.5, and 3.5. Annealing has been applied to samples at 150 C, 250 C, 350 C, and 450 C for one hour. In the next step, compressive test is carried out on MDFed and annealed MFDed pure aluminum through strain rate of 0.01 1/s, 0.001 1/s, and 0.0001 1/s. Based on experimental data, when the number of MDF is passes increased, because of increasing the dislocation density and grain boundary area, yield stress is increased. As an example, the yield stress of 7 passed MDFed aluminum is 2.25 times of that of 1 passes MDFed aluminum. Annealing would... 

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 Li-ion batteries, large volume changes of electrodes with high capacity, such as silicon electrodes during charging and discharging processes (insertion/extraction of lithium into/from the electrode), lead to restrictions on the use of this type of electrode. Given the very high capacity of silicon, predicting and modeling the behavior of silicon electrodes during electrochemical cycles is important and is also addressed in this thesis. First, using the theory of linear elasticity, relations are proposed that couple the diffusion of particles with small elastic deformation. The effect of hydrostatic stress on diffusion and stresses is investigated in lithiation processes. Then, the... 

In this thesis, experimental and numerical investigations are performed on dynamic behavior of fiber reinforced concrete (FRC) by split Hopkinson pressure bar (SHPB) and penetration tests. In the experimental part, effects of parameters such as quasi-static compressive strength of matrix (36 and 48 MPa), strain rate (3*10-5 up to 100 s-1), type of fibers (crimped steel, hooked-end steel, micro polypropylene and micro polypropylene) and volume fraction of the fibers (0%, 1% and 2%) are studied by employing SHPB apparatus on testing more than 150 specimens. Also, different types of FRC panels with 5 cm thickness were casted to perform 20 penetration tests with compressed gas gun apparatus. The... 

Increasing the application of elastomeric structures in industries has caused an interest in the researchers for nonlinear elasticity and viscoelasticity of solids. Such materials which show large deformation and rate dependent behavior are treated by visco-hyperelastic constitutive equations. Based on visco-hyperelastic constitutive equations, total stress is divided into two parts: quasi-static and viscous stress. The method for determining the visco-hyperelastic constitutive equation is strictly dependent on the chosen rheological model. In this project, a new visco-hyperelasic constitutive equation in the integral form was introduced based on the Zener model. Also, based on the internal... 

A significant number of small-scale sensor sales have been reported in recent years. Strain gauges are one of the most common tools for measuring the length change of a part. Nowadays, 3D printing technology can be used in the fabrication of small-scale sensitive sensors, and metal nanoparticles printing are especially suitable for the production of flexible electronic sensors. Electro-hydrodynamic printer, with micro-scale printing capabilities, can be used as a new invention in fabrication of sensors. This type of printer uses the inkjet printing method and the basis of this type of printer is to apply an electric field to shrink the fluid jet. In the present study, pure ethanol was first...