95 research outputs found
Effect of finite edge radius on ductile fracture ahead of the cutting tool edge in micro-cutting of Al2024-T3
No full textEvidence of ductile fracture leading to material separation has been reported recently in ductile metal cutting [S. Subbiah, S.N. Melkote, ASME J. Manuf. Sci. Eng. 28(3) (2006)]. This paper investigates the effect of finite edge radius on such ductile fracture. The basic question of whether such ductile fracture occurs in the presence of a finite edge radius is explored by performing a series of experiments with inserts of different edge radii at various uncut chip thickness values ranging from 15 to 105 m. Chip–roots are obtained in these experiments using
a quick-stop device and examined in a scanning electron microscope. Clear evidence of material separation is seen at the interface zone between the chip and machined surface even when the edge radius is large compared to the uncut chip thickness. Failure is seen to occur at the upper, middle, and/or the lower edges of the interface zone. Based on these observations, a hypothesis is presented for the events leading to the occurrence of this failure when cutting with an edge radius tool. Finite element simulations are performed to study the nature of stress state ahead of the tool edge with and without edge radius. Hydrostatic stress is seen to be tensile in front of the tool and hence favors the occurrence of ductile fracture leading to material separation. The stress components are, however lower than those seen with a sharp tool.Accepted versio
Machining of brittle materials using precision crack-off
No full textAt present, a high wasteful and time-consuming method is widely used in silicon fabrication industry for slicing silicon wafers. To minimize the cost as well as shorten lead time, a new fabrication method should be brought out.
The objective of this project is to verify and develop precision crack-off method which can be used for breaking and slicing silicon ingot even all brittle materials.
In this report, the author described preparations and procedures of the experiments, such as 3-point bending test, and precision crack-off method on rods with 1 and 2 notches respectively. Based on the experimental result, the author analyzed parameters that affect the surface finish of cracking surface and proposed improved ideas for further experiments. In addition, due to failure of some experiments, the author also gave possible explanations. Furthermore, since the main purpose of this project is to apply a new method to mass production, the author provided a feasible experimental setup to be examined further. Last but not least, the author discussed whether this method can be applied to crystalline materials.Bachelor of Engineering (Mechanical Engineering
Study on the improvement of silicon wafering using diamond wire process
No full textFinding a means of clean, efficient and environmentally sustainable energy is a
matter of global concern. Of the various forms of clean energy, solar energy has
matured greatly as an industry. The key component of photovoltaic cells is ultra thin
silicon (Si) wafers that are sliced from Si ingots using the multi-wire sawing
technique that uses loose abrasive slurry. However, this method has several
limitations in the form of high consumables cost and low productivity. Technological
advancements and continued research in this field has led to the development of an
innovative technique whereby diamond impregnated wires are used for sawing thus
doing away with the need for loose slurry. However, this technique also needs further
improvements for cost reduction, improved quality yield and high productivity. The
surface quality and damage are also areas of concern, which needs further study.
In this study, the author designed an experiment to investigate the interaction of
diamond with Si surface. The author used diamond tips, with included angle of 42°
and radius of 15-30μm, to perform multiple scratches on n-type single crystal Si(100)
wafers. The tips were vibrated at frequencies, 486Hz and 2kHz, to study the effect of
vibration on the scratch and wafer surface quality. In addition, the effect of varying
the cutting speed of the tool tips and effect of crystallographic orientation on the
extent of damage of the wafer surface was also examined.
The scratched wafer surfaces were analyzed under the Scanning Electron Microscope
(SEM) to study the surface morphologies of the scratches. Quantitative results of the
width and depth of scratches were obtained using the Confocal Imaging Profiler
(CIP) and finally the wafers were analyzed for possible phase transformations using
Raman Spectroscopy. It was concluded that the scratch at resonant frequency showed
maximum brittle damage while the vibration-less scratch showed dominance of
ductile damage and the width and depth of scratches increased with the increase in
cutting speed.Bachelor of Engineering (Mechanical Engineering
Design of a media finishing device for mechanical components
No full textMedia finishing is carried out by the means of media particles which are also known as abrasives to polish the desired surface of a work-piece. The outcome of a media finishing process is mainly based on the selections of the proper media and work-piece and the operating parameters of the machine itself.
In this project, the author focused on the design and development of a media finishing device which functions to polish mechanical components. The media finishing device was attached onto a CETR Tribometer. With the aid of the rotary drive in the CETR Tribometer, mechanical components were then polished by means of abrasive particles.
This report documents on the entire development involved from the initial start-up to the final stage of the project. The report highlights sections on the design and fabrication of the prototype as well as the testing results of the prototype. The designing segment of the prototype emphasizes on several conceptual and embodiment design developments and ideas generation. The subsequent section of the report covers on the various experimental procedures and input parameters. Last but not least, results attained from experiment runs and future work on the design of the prototype as well as the different input parameters will be discussed.Bachelor of Engineering (Mechanical Engineering
Precision crack-off method for silicon wafering
No full textSilicon is widely used in fabricating silicon wafers for electronics which are used in our daily life. However, the current method of using diamond wire-sawing method to fabricate silicon wafer is still too time consuming and produces almost 50% of wastage due to the high kerf loss of the diamond wire.
In this project, an alternative process using the precision crack-off method to wafer silicon block was being studied. With a similar study on glass rod (BK-7) which produced promising results using this method, the author venture further to use the precision crack-off method on silicon block. Modifications were done to the design of the experiment setup and new feature was being explored such as implementing notches all around the silicon block to produce a better surface finishing.
Through the data collected, this project offers exciting possibilities of using precision crack-off method as an alternative process to slice silicon ingot in its single crystalline structure.Bachelor of Engineering (Mechanical Engineering
Experimental investigation of surface modification mechanism in vibratory finishing process
No full textstatus: Publishe
Novel applications of micro-cutting : thin films to nanowires
No full textTraditionally, metal cutting is a process that used to remove unwanted material from a work piece in the form of chips, which are normally considered as scrap. A new method of producing wire by combining the metal cutting and forming process is described. It is targeted to produce micro wires by this new method which is easy for production and requires little capital equipment relative to conventional wire- making processes.
In this project, new designs of cutting tools are fabricated and experiments are carried out to observe the chip formation whether the chip formed can be undergoing a forming process that forms the chip into round wire. Aluminium 6063 T5 tube is used as the work piece and turning operation is chosen for the metal cutting process of this project. Orthogonal cutting process is applied.
Chips produced by different depth of cut and cutting speed are observed to check the feasibility of the cutter to produce continuous chips and direct the chips flow out from the cutter or forming die.
Chip thickness (to ) is measured and calculation is carried out to analyse the strain of the chip. Chip surfaces and cross sectional profile areas of the chip are observed.Bachelor of Engineering (Mechanical Engineering
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