Sharif Digital Repository

Increasing the lifetime and improving the performance of structures through redesign and optimization are important, especially in marine structures. In general, there are two main groups of marine structures: onshore and offshore structures. Most marine structures are offshore, and these are divided into two categories: floating or sunken. One of the important parameters in the design of sunken structures is the critical load resulting from the buckling of walls, which can cause damage to the structure. In the present paper, three rectangular aluminum and steel compartments of different conditions and sizes were modeled using design analysis methods. Then, different finite element analyses... 

Gonbad-e Qabus, with a height of 52.8 m that makes it the tallest pure-brick tower in the world, located in the northern part of Iran, represents one of the most magnificent structures of the early Islamic centuries. This structure is still standing among the chaos of urban life and construction, catching the eyes of beholders even from far distances. This paper summarizes the historical and architectural background of this monumental structure and the important restorations carried out mainly in the past century. Various types of existing and potential structural and architectural damages are classified and elaborated in detail, and for each problem, a series of proposed solutions are... 

The main aim of the present paper is to assess the fatigue lifetime of ductile cast iron knuckles as one of the critical components of an automotive steering system. To this end, a real driving path, including various maneuvers, such as acceleration, braking, cornering, and moving on various types of road roughness, was considered. Different load histories, which are applied on various joints of the component (i.e., lower control arm, steering linkage, and Macpherson strut), were extracted through Multi-Body Dynamics (MBD) analysis of a full vehicle model. The achievements of previous studies have proved that the steering knuckle fails from the steering linkage and due to the rotational... 

In-stent restenosis (ISR) is one of the main drawbacks of stent implementation which limits the long-term success of the procedure. Morphological changes occurring within the arterial wall due to stent-induced mechanical injury are a major cause for activation of vascular smooth muscle cells (VSMCs), and the subsequent development of ISR. Considering the theory of volumetric mass growth and adopting a multiplicative decomposition of the deformation gradient into an elastic part and a growth part, we present a mechanobiological model for ISR. An evolution equation is developed for mass growth of the neointima, in which the activation of VSMCs due to stent-induced damage (injury) and the... 

Coverage is one of the most important parameters which is always used in practice to characterize a shot peening process. At the same time however, it is the most missing parameter in the finite element simulations of this process. This study aims to relate shot peening simulation to the actual coverage that is developed during the process. Accordingly, two important models from literature are re-simulated and their capability to predict an actual coverage is assessed. Results of this study illustrate that full coverage situation is not captured by these models. Thereafter, a random finite element simulation along with a step by step examination of the treated surface is adopted in order to... 

In this article, the static behavior of micromirrors under the effect of capillary force is studied. The dimensionless equations governing the static behavior and the pull-in state of the micromirror under capillary force are obtained, and the effects of different geometrical parameters on the pull-in angle of micromirrors are investigated. The static behavior of micromirrors is studied both numerically and analytically using the homotopy perturbation method. It is observed that with increasing the instability number defined in this article, the rotation angle of the micromirror is increased and suddenly the pull-in occurs. The results of the presented model are then verified by comparing... 

When properties of the displacing fluid are considered, the rising profile of the penetrating fluid in a capillary tube deviates from its classical Lucas-Washburn profile. Also, shape of capillary tube can affect the rising profile in different aspects. In this article, effect of capillary tube's shape on the vertical capillary motion in presence of gravity is investigated by considering the properties of the displacing fluid. According to the fact that the differential equation of the capillary rising for a non-simple wall type is very difficult to solve analytically, a finite element simulation model is used for this study. After validation of the simulation model with an experiment that... 

In this paper, design, simulation and optimization of a novel electrothermally-activated polymeric microactuator capable of generating combination of bidirectional lateral and rotational motions are presented. The composite structure of this actuator is consisted of a symmetric meandered shape silicon skeleton, a SU8 thermal expandable polymer and a thin film chrome layer heater. This actuator is controlled by applying appropriate voltages on its four terminals. With the purpose of dimension optimization, a numerical parametric study is executed. The modeled actuator which is 1560 ?m long, 156 ?m wide and 30 ?m thick, demonstrates a remarkable lateral displacement of 23 ?m at power... 

Ultrasonic-assisted machining is an advanced method which could improve the process of machining. Besides, simulation modeling process is a method to help the researchers analyze different aspects of the process with more details in a shorter time. Simulation of ultrasonic-assisted machining is also a field of research that is of interest to researchers working in the field of machining processes. In recent years, a variety of papers have been published where cutting forces, chip formation, tool wear and temperature, and microstructure changes were simulated. That being the case, a review paper is required to represent the advances implemented by researchers in the simulation of... 

Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

Flow sensors play a critical role in monitoring flow parameters, including rate, velocity, direction, and rotation frequency. In this paper, inspired by biological hair cells in the human vestibular system, an innovative flow sensor is developed based on polyvinyl alcohol (PVA) hydrogel nanocomposites with a maze-like network of vertically grown graphene nanosheets (VGNs). The VGNs/PVA hydrogel absorbs a copious amount of water when immersed in water, making the sensor highly sensitive to tiny stimuli underwater. The sensor demonstrates a high sensitivity (5.755 mV (mm s−1)−1) and extremely low velocity detection (0.022 mm s−1). It also reveals outstanding performance in detecting... 

Effective diffusion coefficient is an important parameter which needs to be determined in different fields of study, such as cathode catalyst layers of PEM fuel. For this purpose, a Loschmidt diffusion cell can be used. When a porous medium is placed in Loschmidt apparatus, the effective gas diffusion coefficient (EGDC) of this section must be correlated by diffusion coefficient in absence of a porous medium. In the previous researches studying the Loschmidt diffusion cell, a simplifying infinite-length assumption was used in the analytical solution. Therefore, the solution is only applicable for a short time range, and this can result in high error. In order to overcome this challenge, the... 

In this paper, the effect of clamping time on welding distortion is studied. The welding process has been done in austenitic stainless steel 304L butt-welded joint by TIG welding method. The numerical thermo-mechanical analysis is performed using commercial finite element software ABAQUS. The welding simulation is performed using the birth and death of elements technique. The heat source model that used in this study is the Goldak double-ellipsoidal model. At last, for verifying numerical results, a set of experimental tests have been carried out and welding distortion has been measured. The experimental measured data are compared with numerical (FEM) results. The results showed that the...