Sharif Digital Repository

Tool condition Monitoring is done with the aim of reducing the cost and production time along with protect the quality of the machined product and the life of the tool. In this study, using the PCB333B30 vibration sensor and USB-4431 data logger and MATLAB software, the tool conditions in the milling process was examined. The selected feature is to monitor the status of the chatter. The data extracted from the sensor after processing was sent to a cloud user interface that designed on a website. The purpose of this study is to develop a system in which the user can observe the conditions of the tool (chatter occurrence) in real-time, over time and over place, just by access the... 

Direct metal deposition (DMD) process is an additive manufacturing technology that is rapidly gaining laser importance due to its various capabilities in applications such as coating, repairing high-value damaged parts, rapid prototyping and even production in small quantities. Among the equipment needed for this process, nozzle is perhaps the most important component because its performance affect the efficiency of powders trapped in the molten pool, and is crucial to the quality of the deposited layer. The existing nozzle designs can be categorized in two groups; lateral and coaxial nozzles; and the coaxial ones are divided into continuous and discontinuous types. Coaxial nozzles have... 

Nowadays, there is a focus on developing a propulsion system with higher efficiency and performance in comparison to conventional systems. Many diverse systems have been designed for the vessel propulsion and everyday, utilizing new ideas, their performance and energy consumption are being improved. Direct use of steam energy is a noble and new idea. In this research, the steam jet propulsion system has been explained and current worldwide research on the topic has been investigated. Considering the shortage of primary data in the field and the novelty of subject, required information for the manufacturing of a sample model of this special propulsion system has been gathered and a design for... 

High speed machining is becoming a progressive trend in machining processes. The main part of a high speed machine tool is its spindle. The purpose of this thesis is to design and manufcture a high speed spindle for milling machine that can rotate at speed of 16000 rpm. This spindle can be used as a test bed for experimental parametric study on the effects of spindle design parameters on the performance of spindle bearings. Various components of the spindle is studied and designed. High speed angular contact bearings and roller bearings are used in the spindle to provide high precision as well as good thermal performance. The spindle is built and tested for high precision machining with... 

Cloud Manufacturing (CMfg) is a service-oriented manufacturing (SOM) paradigm that provides a dynamic, scalable, and virtualized working ecosystem. The CMfg collaborative structure can be modeled as a hyper-network-based service-demand matching architecture. It is enriched with quality of service (QoS) characteristics to produce customized products in a stable and reliable network. This stability should be considered in the overall manufacturing network mechanism. This Thesis has developed a multi-dimentional model and improved it by providing absorptive and adaptive strategies utilizing available resources and capacities to enhance the system’s stability and reliability against the... 

The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are easily adaptable with new functions and technologies. In fact, a highly responsive manufacturing system is needed in which, introducing new products, adjusting system capacity with demand fluctuations and integrating new technologies with the existing ones are quickly possible. Reconfigurable Manufacturing systems (RMS) are a relatively new paradigm in industry that enable rapid adjustments of production capacity to changes in product mix and volume through their main characteristics including modularity, scalability and... 

The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are easily adaptable with new functions and technologies. In fact, a highly responsive manufacturing system is needed in which, introducing new products, adjusting system capacity with demand fluctuations and integrating new technologies with the existing ones are quickly possible.Reconfigurable Manufacturing systems (RMS) are a relatively new paradigm in industry that enable rapid adjustments of production capacity to changes in product mix and volume through their main characteristics including modularity, scalability and... 

Today, the additive manufacturing process is one of the most important manufacturing processes. In the additive manufacturing process, the mass of the parts is directly related to the printing duration, in addition to the costs of consumables. On the other hand, the use of lighter parts in industries, such as the aviation, is one of the important requirements of those industries, and topology optimization is needed to reduce the consumables and the mass of the parts. Also, since in the optimal design of engineering parts, more than one design objective is usually considered, the multi-objective optimization of topology is of great importance. The Moving Morphable Components is one of the new... 

Gears are a major component of many transmission systems. nowadays, improving the operating conditions and reducing the weight of the gears is one of the most needed issues in the industry. This dissertation aims to find the optimal structure of gear under different load cases and reduce its weight optimally. In this regard, topology optimization is used to develop the gear structure.In this research, two areas of bio-inspired design and additive manufacturing are used to achieve goals. These two areas can make good use of each other's potentials and achieve results that were not previously possible with traditional methods of design and manufacturing. First, an introduction and history of... 

Hand-launched UAVs are type of unmanned aerial vehicles that due to transportability and geometric specification, are operationally valuable and worthy. reconnaissance & surveillance (aerial mapping, aerial filming, inspection, border protection); health care (blood transport, body organ transport, medicine delivery); agriculture (farm monitoring, fertilization, cloud seeding); payload delivery (envelopes posting); network covering (internet supply, telecommunication relay); crisis management (remote area medical) are some of typical applications and missions of this type of aircrafts. These UAVs have almost low altitude short endurance (below 5000 ft. and less than 2 hrs.). To extend their... 

Direct Metal Deposition is one of the methods of Additive manufacturing that has seen the most spread in recent years. In this method metal powder is directed towards the free surface of the workpiece through a nuzzle, and is simultaneously heated to become molten in a melting pool by a laser beam and begins the deposition process. One of the parts that make up a DMD system is powder feeding nuzzle. These nuzzles usually encounter a similar fundamental problem: that the effect of gravity on the stream of metal powder and the carrier fluid causes this stream to deviate from its intended position. To prevent this, nuzzles are usually designed with a fixed downward angle and the angle of the... 

Fuel cell is a power generator like internal combustion engines, but the first point is that internal combustion engines produce mechanical power while fuel cells produce electrical power. Secondly, internal combustion engines use hydrocarbon derivatives such as gas as fuel and their exhaust fumes are toxic gaseous, but fuel cells use hydrogen as fuel and their exhaust are only water in either vapor or liquid form. One of the most important issues in fuel cells is optimum design of micro channels of bipolar plates which is different regarding the type and application of fuel cells. Optimum designing of micro channels on bipolar plates plays a key role in fluid mass transport through micro... 

One of the major challenges in Additive Manufacturing is the creation of residual stresses due to the high temperature gradient in the solidification zone. This will cause problems such as cracks in the structure, metallurgical defects as well as deformation and dimensional accuracy reduction in the finished product. The purpose of this study is to perform mathematical modeling and computer simulation of the selective laser melting process (SLM) to predict these stresses as well as identify the effective parameters on this phenomenon. The conditions were adjusted in this model with the actual coefficients of the device. Additionally, the powder used in this project is Ti6Al4V material. By... 

In the process of Additive manufacturing for metals, the ability to predict and control the microstructure can reduce the need for subsequent heat treatment and accelerate the component quality assessment process. The ability to predict and control the microstructure of materials in the laser deposition method needs to understand the thermal conditions during the solidification process. For this purpose, the present study investigated the relationship between cooling rate and temperature gradient during local solidification, and control parameters of the laser deposition process such as power, beam radius, scanning speed and strategy of laser, ambient temperature and preheating temperature.... 

Additive manufacturing can be considered as a revolution in the manufacturing industry. The unique capabilities of this technology have led to the removal of many obstacles to the construction of complex and special parts. In this study, with the aim of further understanding how the gradient region is formed, the possibility of detecting the microstructure and finally the properties of the gradient piece made, a solidification process has been simulated in direct metal deposition. The results of this study include calculating the heat distribution during the process and obtaining a thermal history of the fabricated part, calculating the dimensions of the molten pool and the heat affected... 

Integrated design includes CAD, process planning and CNC code generation based on an integrated data structure. To enable different CAD/CAM software solutions to be interoperable, it is required to support data exchange in manufacturing enterprises. To realize interoperability there are two basic approaches: i. to focus on STEP standard to support data exchange between CAD systems as well as CAPP/CAM and CNC machining systems; the use of STEP standard ensures the data integration based on STEP standard. ii. utilizing a platform consists of structures and procedures to enable exchange of data between different CAD/CAM/CAPP software applications seamlessly. In this article, the important... 

Nowadays, as a result of rapid changes of market, it is necessary to reduce the period between design and manufacturing of a new product. Among them, process planning is one of the most difficult elements of production chain and also, there are a few numbers of experts in this field. In addition, this process is time-consuming and costly. So, it is important for companies to reduce the period of new product’s presentation by reduction of process planning duration. On the other hand, it is proved that the lowest level of integration in CIM systems is in CAPP section. Integration provides sharing data in the system, so the other parts of production systems can exchange product information and... 

The synergy of fundamental factors like changes in governmental policies, global expansions of the manufacturing industries and improvements in technology related to reliability of manufacturing information flow have created the global manufacturing revolution in the first years of the twenty-first century. The concept of global manufacturing enterprise potentially brings up benefits and opportunities for today’s manufacturing enterprises like reduction of manufacturing costs by utilizing low labor-cost countries, reduction of business risks and introduction of new markets as a new source for enterprise growth. However, it enforces enterprise to endure costs to adopt the global... 

The per capita income and welfare levels of countries around the world vary significantly from each other. Identifying the factors that lead to differences in the per capita income of countries as well as their welfare levels is a major concern for economists. Studies conducted in this field indicate that one of the main sources of these differences is the significant disparity in the total factor productivity (TFP) across countries. Suboptimal resource allocation is one of the most influential factors affecting TFP in countries. The primary importance of investigating misallocation in the Iranian economy is that, in line with the decrease in economic growth, the growth rate of industrial... 

A decade after discovery of graphene, the unique properties and characteristics of two-dimensional materials, particularly an emerging family of carbides and nitrides (MXenes), have attracted the attention of researchers. MXenes are two-dimensional structures of two or more layers of transition metals, with interstitial carbon and/or nitrogen atoms, with exceptional properties such as high specific surface area, excellent elastic modulus, metallic conductivity, and various termination groups. These properties can be altered by various factors, including chemical composition and synthesis processes, and any changes in these factors significantly affect the properties of MXene sheets. In this...