جستجوی مقالات مرتبط با کلیدواژه « طراحی » در نشریات گروه « مکانیک »

In this research, the design of a can combustion chamber for a ramjet engine, the performance of this chamber and the role of flameholder have been studied. For this purpose, after talking about ramjet engine types, some general information about the combustion chamber has been explained. Then the process of chamber designing and determining its geometry has been discussed. The dimensions of the chamber were determined by using input conditions extracted from GasTurb software as well as applying a calculation code, and the geometry of the chamber have been determined by applying calculation codes. By evaluating the obtained geometry and ensuring the accuracy of the design, simulation of combustion with non-premixed liquid phase was carried out using Fluent software. While presenting the results, the effects of size, distance and number of flameholder have been investigated. It is shown that the use of flameholder in ramjet engines is essential but the use of large flameholder is not recommended.

The smart facade system is known as one of the main elements of the building envelope with optimal efficiency, which is able to respond to environmental stimuli and seeks to improve the comfort of residents and optimize energy consumption. While building design research has addressed the technical aspects and design of smart facades, very limited historical studies have been conducted on the evolution of such systems. Therefore, the current research examines the factors affecting the design and development of smart facades in cities to optimize energy consumption based on a historical period. This article examines and classifies the effective historical components in the evolution of the design and development of the smart facade system using the historical hierarchy method. The effective components in the form of socio-cultural, technical, political, environmental and economic categories are caused by revolutionary changes in art, technology and building construction from the 19th century onwards. The findings showed that the historical timeline presented in this article is considered as a useful resource for researchers and educators in research and educational activities. Based on this table, the current development pattern can be understood and possible future events (trends) can be predicted. The timeline shows that smart facades can be used in the future on an urban scale for all neighborhoods of cities, which helps to improve the comfort of residents and improve energy consumption in cities.

Improving the specialized problem solving skill is necessary for solving specialized problems at work because the correct and timely solution of work problems increases productivity and prevents its possible corresponding damages. Improving this skill is necessary for all people with any job, especially people with academic education in all fields of study. Machine design is one of the most important specializations of mechanical engineering and mechanical engineering of biosystems which students need to learn it well during their studies. Due to the high importance of specialized problem-solving skill, the necessity of proper implementation of the design process to solve various problems, and the effective role of education in improving this skill, the purpose of the present research is to review various materials in the field of teaching the design of machine elements with a focus on problem solving skill. In addition to teaching a suitable textbook, solving the home works of the textbook, and writing tests, teaching the design of machine elements requires five main components including 1. Idea generation, 2. Safety considerations, 3. Design of the day, 4. Improving designers’ responsibility, and 5. Conducting a project. Considering these cases in the educational course, a strong foundation and an important stimulus is provided for students to enter real design and product manufacturing with a problem solving approach.

Non-circular gears for their ability to create cyclic changes in the velocity and torque of the gears in each revolution employed for various purposes such as robotics, textile, and packaging industries. In this paper, the design methodology of a similar pair of plastic square gears is investigated. The design of gear profiles was performed according to complex mathematical calculations and the three-dimensional model of the gears was designed. Then the assembly of the gears was performed in CAD software and their motion was simulated. The laser cutting process was utilized to manufacture square gears. Examination of the results and the absence of special errors such as the gear's inappropriate meshing during rotation, improper backlash, or the impossibility of assembly due to incorrect dimensions design, indicate the accuracy of the design methodology. Moreover, the use of thin plastic sheets as raw material in the laser cutting process has prevented the laser beam from diverging and technical faults of gear samples. Comparing the angular speed of the driver gear with the lobe number also shows the accuracy of the square gear simulation process.

In this paper, a pair of non-circular gear reducers consisting of a triangular driver gear and a pentangle driving gear was designed and fabricated. By determining the design parameters, two-dimensional and three-dimensional models of both gears were drawn using the software. Then, the movement of the gears was simulated and analyzed in the software. With the confirmation of the angular velocity and angular acceleration results, both gears were manufactured by the additive manufacturing process. The results revealed that the design method presented in this paper guarantees the functional accuracy of non-circular gears. The gears were assembled correctly and their movement was correct. Moreover, by selecting precise input parameters the production of non-circular gears using the additive manufacturing process has led to the achievement of a tolerance range ±0.02 mm and has prevented them from stepping along the thickness.

In the nearly six decades, exoskeletons have progressed from the stuff of science fiction to nearly commercialized products. In addition, the main part in usage of these robots in the medical sciences and particularly for the rehabilitation, specially disabled and elderly people is to help them to do their basic routine activities like walking, sitting and etc. This article represents the design process of a lower limb exoskeleton robot for helping disable people in gait cycle. First, the conceptual design of 7 Degrees of Freedom (DoFs) robot, consist of 3-DoFs in each leg and 1-DoF in hip joint, is presented. Then the dynamic modeling of mechanical system is shown by Lagrange Method. In addition to producing an optimized mechanical model of the exoskeleton, it was necessary to ensure the strength of each component. So that after the force analyzing of the robot components which are designed for the lower limb extremities, the physical output information of the modeling software (CATIA) is used as the dynamic model input and also in order to obtain motion equation in the gait cycle always needed to choose an appropriate coordinate for simulating closer to reality. In continuation of discussion a combined controller is designed to investigate its performance. Finally the system results are shown the maximum torque of 1st joint is 32 N.m, the 2nd joint is 13 N.m and the 3rd joint is 3 N.m. The maximum torques lead to select the suitable actuator for each link of robot.

Using renewable energies instead of fossil fuels can reduce environmental problems. In this way, batteries can play an important role as energy storage. Lithium-ion batteries have been very much considered in recent years due to their high energy density and long life time. The use of electric vehicles is increasing to prevent air pollution in various countries. In these cars, electric motors that work with batteries are used instead of internal combustion engines. In this paper, a lithium-ion battery was modeled electrically and thermally. It was indicated the temperature increase and the battery voltage decrease in discharging process. The numerical solution of the energy and electrical equation was made using a finite volume method in computational fluid dynamics. The results showed that when the battery is discharged at a discharge rate of 1c, the battery temperature reaches 54°C and at a discharge rate of 2c, the battery temperature reaches 83°C, which can damage the battery. To avoid this problem, a cooling system was designed which, with a flow rate of 0.2 m / s and 25°C at a discharge rate of 1c cooled battery to 31°C and at a discharge rate of 2c to 40°C. To increase cooling, with a flow rate of 0.2 m / s used a temperature of 15, in this condition the temperature of the battery at discharge rate of 2c reached a discharge temperature of 37°C, which falls within the permissible range.

Due to the problems in the country (Islamic Republic of Iran) for purchasing aircraft and aircraft old fleet, a solution should be proposedfor this problem. One way to address this need is designing and manufacturing the aircraft in the country.According to the previous investigations carried out, 180-seater passenger planes with a range about 5,000 Km are part of the requirements of the country. In this paper, the costs of design, construction and operation of this type of aircraft has been studied. Also, the inventory costs in the United States of America have been investigated and compared with the costs in the Islamic Republic of Iran. There are three main objectives in this research: the first is to estimate the total expenditures in terms of the different phases of the design, construction and operation; the second concerns reducing design costs to much less than the costs of construction and mining; and finally, the third involves an analogy of the costs of design and production in Iran versus the U.S.

In this paper, the features of Ant Colony Optimization Algorithm (ACOA) are used to find optimal size for sewer network. Two different formulations are proposed. In the first formulation, pipes diameters and in the second formulation, nodal elevations of sewer network are taken as decision variables of the problem. In order to evaluate the performance of different ACOAs, four algorithms of Ant System, Elitist Ant System, Ranked Ant System and Max-Min Ant System are used to solve this optimization problem. Different test examples are solved using two proposed formulations for each ACOAs and the results are presented and compared with other available results. The results indicate the efficiency of the proposed methods in the solation of sewer network design optimization problem and the results of Max-Min Ant System are better in comparison with other ACOAs.

Modified atmosphere packaging for fresh products is a dynamic system and depends on modifying the atmosphere inside the package which the result was two process of product respiration and transfer of gases through packaging film and leads to an atmosphere in higher CO2 and lower O2. The challenge is how mathematical models are presented to show product breathing and package permeability is closed in order to simplify the packaging design and reduce expense and time needed for traditional MAP using trial and error. The purpose of this research is to show the application of mathematical models in designing packaging with Modified atmosphere for fresh products. The mathematical models entered and calculated for respiration and product permeability in programming Software of MATLAB. In this designing can be modeled, respiration rate, temperature dependence of respiration and permeability and finally, packaging film, optimum weight within the package , optimum temperature, and amount of gasses can be Revealed.

Parallel manipulators are mechanisms with closed kinematic chains which have been developed in different forms, but these manipulators have several drawbacks such as small workspace, existence of singular points in their workspace, and complex kinematics and dynamics equations that lead to increase of difficulty in their control. In spite of this, this mechanism has been being conventionally used in many different industrial applications such as machining, motion simulators, medical robots, etc. To overcome these drawbacks, design and manufacturing of a manipulator with three translational degrees of freedom are provided. Design of this manipulator was based on the possibility of three translational motions for its end-effector. The manipulator degrees of freedom are obtained via screw theory. Basic features, consisting of forward and inverse kinematics, workspace and singularity analyzes and also velocity analysis, are considered in this paper. A numerical algorithm is implemented to determine the workspace regarding applied joint limitations and the design parameters were extracted based on to achieving to the desired workspace. The robot motion is created by using of pneumatic actuators which receive their command from a pneumatic servo valve. After design steps, the required elements were provided and assembled in a robotic lab. Finally, the simulation results have transparently approved the improved robots.

One of the principles of sustainable and targeted packaging in food packaging in order to prepare consumer needs, is the role of packaging design indicators in the ability to seize it. Food packaging is especially important to consumer and must has high performance and should be opened easily by the consumer at the time of consumption, on the other hand it should observed health and safety issues in it. So one of the sustainable design strategies that should be made by designers in order to needing to existing or new packaging, is satisfying the needs of consumers. To make the package easily available, it should be easy to open without risk to the health of the consumer and also have good and high quality. Producers who do not adhere these factors, they should tolerate the negative effects and consequences of declining sales of their products.

The purpose of this paper is to introduce a design and fabrication procedure for a solid propellant gas generator. Based on this procedure a gas generator was designed to supply the required operating fluid of a controllable flying object’s gaseous actuator of control surface which results of that design is presented in this paper as well. Supplying required pressure during the mission and gas flow rate with expected chemical characteristics are requirements of the design. At first the amount of necessary parameters like flow rate and pressure were specified. Then the design calculations were done according to proposed approach. In order to evaluate the design process and achieved data, a full scale gas generator set was built. Since this study includes specifying a proper formula for solid propellant of gas generator, a lab scale motor was used to qualify the propellant’s characteristics experimentally. After doing tests and comparing the results with output data of gas generator design procedure, convenient consistency was observed. Besides by doing several tests it was found that PSAN as oxidizer, HTPB as binder and chromium oxide as catalyst is a proper composition for solid propellant of gas generator. Finally, covering basic requirements of a solid propellant gas generator such as uniform flow rate and less presence of solid phase and corrosive components in combustion products by means of designed gas generator is an approval to show the validity of presented design method.

Continuum and flexible manipulators have a special role in medical applications. One application is robotic manipulators use for surgery or endoscopic tool use for inspection of body parts like esophagus or colon. In addition to small size, better maneuverability increases the tool performance in real applications. One of the useful actuators in miniaturizing mechatronic systems is shape memory alloys. The material which is usually used as a linear actuator produce high forces in comparison to weight. In this paper, embedding three shape memory springs inside the structure of a flexible module, a two-DOF mechanism is provided. The module has a rigorous usage in modular robotic systems especially flexible manipulators. The developed module produces large deflection in addition to covering a large workspace. Modeling of the module is discussed in this paper for extracting module parameters in design and implementing the simulation. Through the complex behavior of SMA and uncertainty in model, control of SMA is a challenge. In this paper using a novel algorithm, a desired shape for the module is provided. Using the new non model based control approach, the final shape or position is realized. The adequacy of introduced controller is verified through experiments. Large workspace and controllability of module make it feasible for real applications.

In this study, the accuracy of steady and unsteady methods in predicting the required length of air-earth heat exchangers have been compared for cooling application. Also, the impact of different conditions for inlet air temperature (constant, periodic and actual temperature) on unsteady methods have been studied. Results indicated that, steady model cannot provide correct estimation for the required length of channel. In addition, using unsteady method with constant inlet air temperature overestimates the required length of the channel, which can lead to economic and implementation challenges for project. However, using unsteady method with periodic inlet air temperature the required length of the channel can be estimated with acceptable accuracy compared with real situation (unsteady model with actual inlet air temperature).Results showed that after a month of the launch of the system, its thermal behavior reaches to steady state level. During this period effectiveness of the system drops significantly (nearly 50%). Nearly half of the total performance drop of the system occurs during the first working day. It means that the long-term behavior of the system can be determined by monitoring of its behavior in the first day of operation. Results also demonstrated that using common methods of designing usually brings a significant error.

In this paper, a hybrid model which consists of planar parallel robot with a 2-DOF arm is presented. This manipulator is based on cable parallel robots and a kinematic serial chain is utilized and added to a cable parallel chain. The hybrid manipulator can provide features of both serial and parallel mechanism. Understanding the orientability of the end-effector within this workspace gives a measure of the ability of the robot to perform manipulation tasks. Most underactuated parallel manipulators have a low rotational capability. To overcome it, this paper focuses its attention on a new family of serial-parallel manipulators. The initial goal of this design is to increase the orientability capability of a planar two-cable robot. The kinematic and dynamic analysis of this new type hybrid manipulator is presented. The dynamic modeling is performed by using a combination of Lagrange and Newton-Euler methods. This paper conducts the dynamic trajectory planning study to a novel design for the cable robots. In fact, time optimal trajectory planning is a strategy that is used to verify this new design. Two models are considered in the simulation part. A novel hybrid model is compared to a planar parallel cable robot. It is verified that the proposed design allows significantly reduced actuation energy and improved orientability capability compared to the parallel robot.

One of the major pollutant in the nature is greenhouse emisions caused by fossil fuels. Traditional HVAC systems has low efficiency and high pollution and so life on the earth is confronted to the greatest challenge after beginning of civilation. In recent decades, however, sustainable policies and plannings are offered many amendatory ways to change building design process as integrated design process and holistic approach which was profited to rise energy efficiency in equipment. Net zero energy building is a result of common aim and responcible participation of architects, civil and electrical and mechanical engineers in this area. This type of buildings has greatly reduced energy needs through efficiency gains such that the balance of energy needs can supply with renewable technologies. This article was conducted to present this process design to determine intervener factors and the rate of success ultimately. Research method is on descriptional- analytical due to study library's documents and review case studies.

The scope of the current investigation incorporates the entire process involved in design and development of a Shape Memory Alloy (SMA) actuated wing intended to fulfill morphing missions. At the design step, a two Degree-of-Freedom (DOF) mechanism is designed that is appropriate for morphing wing applications. The mechanism is developed in such a way that it can undergo different two DOF, i.e. gull and sweep, so that the wing can have maneuvers that are more efficient. Smart materials commonly are selected as the actuators due to their suitable thermo-mechanical characteristics. Shape Memory Alloy (SMA) actuators are capable of providing more efficient mechanisms in comparison to the conventional actuators due to their large force/stroke generation, smaller size with high capabilities in limited spaces, and lower weight. As SMA wires have nonlinear hysteresis behavior, their modeling should be implemented in a meticulous way. In this work, after proposing a two DOF morphing wing, an aerodynamic analysis of the whole wing for unmorphed and morphed wings is presented. The results show that the performance of the morphed wing in special flight regimes is improved.