Sharif Digital Repository

According to development of industry in every field such as nanotechnology and micro electro mechanical system (MEM) fabricating of high speed machining with micro dimension has been expanded. Micro spindles are such a device which is useful in many industries such as air space and electronic field. These machines can work in high speed and production rate with vast variety of features. Their dimensions are in millimeter range. So they can manufacture miniature features. Fabricating and technical science production of a high speed micro spindle with speed of more than 100000 RPM (micro macro milling) is purpose of this project. After to literature review according to science of micro... 

The main scope of this research is developing an impedance control strategy for a six-degree-of-freedom parallel manipulator with the application in the milling process. One of the most common known parallel manipulators is the Stewart platform, which was proposed in 1965. [It evolved into a popular research topic of robotics in the 1980s.] Problems in various aspects of design, kinematics, dynamics, singularity and workspace analysis have been investigated in the literature. Derivation of control strategies taking advantage of the in-parallel structure or catering for the special problems arising out of that is another important field, whichhas been almost untouched till now.
The main... 

Right now, the common standard for programming of CNC machines is ISO6983 which is also called G-code. This standard provides very low level information that only contains information about basic measurements and tool movements. Moreover, it splits the CAD/CAM/CNC chain and makes it difficult to gather feedback from shop floor. A global attempt led to development of a new data model for programming CNC machines. STEP-NC standard which is developing based on STEP is aimed to resolve shortages of G-code. The STEP-NC based controllers, can be categorized into three major groups in terms of programming: indirect, interpreted and adaptable. In this project, in order to develop the third category... 

In this study, an equivalent homogenous material model is proposed for Al6061-T6/Al2O3 metal matrix composite using the hierarchical multi-scale modeling, and the capability of this model in simulation of machining process of this composite is investigated. Molecular dynamic study of the Al/Al2O3 interface is used to obtain the effect of crystallographic orientations and terminations on the tensile and shear strengths at the interface. The Reaxff potential function is employed to estimate the traction-separation relations at Al/Al_2 O_3 interface at temperatures of 300, 400, and 500 K. Next, a cohesive zone model is used at the micro-scale to simulate the interface between the matrix and... 

Machining of Aluminum Metal Matrix Composites faces different problems including adhesive wear, large machining forces, chatter, poor surface quality and therefore low geometric accuracy etc. due to the fact that a ductile matrix is supporting brittle particles. On of the methods used to reduce such difficulties is vibration assisted machining in which a 10 to 20 micron displacement stimulation is applied to the workpiece or tool during machining process. The effect of this method on the milling of the Al/Sic composite is studied through two separate experiments including one and two dimentional vibration assisted milling respectively. Milling forces, tool wear and surface quality are... 

Designing a part of an on site repair system for refurbishing steam turbine high pressure control valve has been done in this project. The main role of this control valve is to control the input flow to the turbine in different working condition . However, due to high temperature and pressure, the seat is exposed to erosion. R epairing this part in workshop requires great amount of time and cost, because the valve is a part of the turbine body and must be cut and rewelded to the turbine body. S o using an on-site repair method is highly needed. In addition, due to the limited visibility and access to the valve seat, and accurate... 

This study investigates the application of ionic liquids as a lubricant in the minimal lubrication system for P20 steel drilling. due to the wide use of cutting fluids in machining processes, it is important to research in this regard to reduce emissions of pollutants, reduce friction, and consequently reduce energy consumption and machining costs. in recent years, ionic liquids have been considered as a new lubricant due to the structure and composition of the special chemical in the fields of: bearings, metal forming, etc. however, in the application of ionic liquids as fluids In the process of machining, very little research has been done. Therefore, deserves that examining the effect of...