Where is the Great Rift Valley

The Rift Valley, also known as the Great Rift Valley or Eastern Rift Valley, is a geological feature due to the movement of tectonic plates and mantle plumes that runs south from Jordan in southwest Asia, through East Africa and down to Mozambique in southern Africa. In all the Rift Valley is 4000 miles (6,400 km) long and is 35 miles (64 km) wide on average. It is 30 million years old and exhibits extensive volcanism, having produced Mount Kilimanjaro and Mount Kenya. The Great Rift Valley is a series of connected rift valleys. Seafloor spreading at the north end of the system created the Red Sea, separating the Arabian Peninsula on the Arabian Plate from the African continent on the Nubian African Plate and will eventually connect the Red Sea and the  Mediterranean Sea. The rifts on the African continent are in two branches and are slowly splitting the horn of Africa from the continent. It is thought that the rifting on the continent is driven by mantle plumes from deep in the earth, thinning crust so it may eventually form a new mid-ocean ridge as eastern Africa is split from the continent. The thinning of the crust has allowed the formation of volcanoes, hot springs, and deep lakes along the rift valleys. Eastern Rift Valley There are two branches of the complex. The Great Rift Valley or Rift Valley runs for the full extent, from Jordan and the Dead Sea to the Red Sea and across into Ethiopia and the Denakil Plain. Next, it goes through Kenya (particularly Lakes Rudolf (Turkana), Naivasha, and Magadi, into Tanzania (where because of erosion of the eastern edge it is less obvious), along the Shire River Valley in Malawi, and finally into Mozambique, where it reaches the Indian Ocean near to Beira. Western Branch of the Rift Valley The western branch of the Rift Valley, known as the Western Rift Valley, runs in a great arc through the Great Lakes region, passing along lakes Albert (also known as Lake Albert Nyanza), Edward, Kivu, Tanganyika, Rukwa, and to Lake Nyasa in Malawi. Most of these lakes are deep, some with bottoms below sea level. The Rift Valley varies mostly between 2000 and 3000 feet (600 to 900 meters) in depth, with a maximum of 8860 feet (2700 meters) at the Gikuyu and Mau escarpments. Fossils in the Rift Valleys Many fossils showing the progress of human evolution have been found in the Rift Valley. In part, this is due to the conditions being favorable for preserving fossils. The escarpments, erosion, and sedimentation allow bones to be buried and preserved to be discovered in the modern era. The valleys, cliffs, and lakes may have played a role in bringing together different species in a variety of environments which would spur evolutionary change. While early humans likely lived in other locations in Africa and even beyond, the Rift Valley has conditions that allow archaeologists to discover their preserved remains.

Comparing Mary Shelley’s Frankenstein and Kenneth...

Comparing Mary Shelley’s Frankenstein and Kenneth Branaghs Frankenstein Most Americans have some idea of who Frankenstein is, as a result of the many Frankenstein movies. Contrary to popular belief Mary Shelley’s Frankenstein is a scientist, not a monster. The monster is not the inarticulate, rage-driven criminal depicted in the 1994 film version of the novel. Shelley’s original Frankenstein was misrepresented by this Kenneth branagh film, most likely to send a different message to the movie audience than Shelley’s novel shows to its readers. The conflicting messages of technologies deserve being dependent on its creator (address by Shelley) and poetic justice, or triumph over evil (showed by the movie) is best represented by the†¦show more content†¦. . . I was nourished with high thoughts of honor and devotion.† (154) He did not start out as an evil being, but rather was good by nature and exposed early in his life to good things. (Allen, g.s) Frankenstein’s and society’s rejection of the monster, however, drove him to an uneven passionate pursuit for a companion. He forced Frankenstein to create a female monster, and he provided motivation by killing Frankenstein’s loved ones and threatening to kill more of them. The monster recalls in this final scene of Shelley’s novel how his desire drove him to evil. â€Å". . . do you think that I was then dead to agony and remorse?--He . . . suffered not more in the consummation of the deed;--oh! Not the ten-thousandth portion of the anguish that was mine during the lingering detail of its execution. A frightful selfishness hurried me on. . . .† (153) At that point in the novel, the monster has changed from good in nature to evil in nature. His own desires are more important to him than the well-being of others and he is willing to commit murder in order ensure the fulfillment of his desire. The second change the monster makes is becoming totally motivated by revenge. He becomes completely evil, not looking for a companion but only the unhappiness and suffering of Frankenstein, his creator. â€Å"... I was the slave, not the master of an impulse, which I detested, yet could not disobey. ... The contemplation of myShow MoreRelatedA Comparison of Film Techniques of Two Film Versions of Mary Shelleys Frankenstein1861 Words   |  8 PagesComparison of Film Techniques of Two Film Versions of Mary Shelleys Frankenstein Mary Shelley wrote her novel Frankenstein when she was just a young girl of nineteen. She wrote it in 1816, when she went on holiday with her friend, Byron. Byron was already a famous poet, and it was him who suggested that whilst they were away, they should both write a ghost story. At the time it was just a way of passing time and having fun for Mary Shelley, but little did she know that her storyRead More Opening Sequences of Frankenstein by James Whale and Kenneth Branagh5160 Words   |  21 PagesOpening Sequences of Frankenstein by James Whale and Kenneth Branagh Frankenstein Compare the opening sequences of Mary Shelleys novel Frankenstein filmed by James Whale (1931) and Kenneth Branagh (1994). Describe and account for the major differences and similarities between the versions. The gothic horror novel, Frankenstein, was written by Mary Shelley during the Industrial Revolution, which was a period of dramatic change. It was a groundbreaking and controversial novelRead MoreComparison Between Frankenstein And Mary Shelley s Frankenstein1644 Words   |  7 Pagesseen when comparing the creature in Mary Shelley’s original novel Frankenstein to multiple newer representations. The creature is portrayed differently in almost all illustrations; unfortunately, all modern representations of the creature tend to be wrong. The creature’s physical characteristics, intellectual abilities, morals, and actions are all drastically different when comparing modern representations to Shelley’s actual portrayal of the being, and these changes can ruin Shelley’s depiction

Electric Discharge Machining Free Essays

string(230) " EDM Electro Discharge Machining \(EDM\) is an electro-thermal non-traditional machining Process, where electrical energy is used to generate electrical spark and material removal mainly occurs due to thermal energy of the spark\." PROJECT REPORT ON INVESTIGATIONS INTO ELECTRIC DISCHARGE MACHINING USING EN-31 AND HCHCr WORK PIECE GUIDED BY:PROF. RAJESH MADARKAR SUBMITTED BY:ROSE DEE KAMLESH GEHANI SHARDUL AMIN SIDDHESH TIWARI SUVO SUNDAR CHATERJEE VIVEK WARADE DEPARTMENT OF INDUSTRIAL ENGINEERING SHRI RAMDEOBABA COLLEGE OF ENGINEERING AND MANAGEMENT KATOL ROAD,NAGPUR-440013 2011-2012 ABSTRACT The correct selection of manufacturing conditions is one of the most important aspects to take into consideration in the majority of manufacturing processes and, particularly, in processes related to Electrical Discharge Machining (EDM). It is a capable of machining geometrically complex or hard material components, that are precise and difficult-to-machine such as heat treated tool steels, composites, super alloys, ceramics, carbides, heat resistant steels etc. We will write a custom essay sample on Electric Discharge Machining or any similar topic only for you Order Now being widely used in die and mold making industries, aerospace, aeronautics and nuclear industries. The objective of this Project Report is to study the influence of operating parameters of pure copper electrode on the machining characteristics such as, material removal rate for work piece material EN-31 and HCHCr ( hardness 20-22 and 55-56) Keywords: EDM; TON; T ; MRR; IP;EN-31;HCHCr Purpose: In this investigation, the effects of various process parameters of sinker EDM like: †¢ pulse on time (TON), †¢ †¢ peak current (IP), Duty Cycle(T) have been investigated to reveal their impact on material removal rate of materials: †¢ EN 31 (Hardness: 20-22) HCHCR (Hardness:20-22) †¢ HCHCR (Hardness:55-56) using one variable at a time approach. The optimal set of process parameters has also been predicted to maximize the material removal rate. . Design/methodology/approach: The experimental studies were performed on ELECTRONICA SPRINTCUT EDM machine. Findings: The material removal rate (MRR) directly increases with increase in pulse on time (TON) upto a certain leve l after that it shows a declining trend and increases directly with peak current (IP) SHRI RAMDEOBABA COLLEGE OF ENGINEERING AND MANAGEMENT INDUSTRIAL ENGINEERING DEPARTMENT CERTIFICATE This is to certify that Ms. Rose dee (12),Mr. Kamlesh gehani (48),Shardul amin(76),Siddhesh tiwari(78),Suvo sundar chaterjee(81),Vivek warade(86) has submitted the project work on INVESTIGATION OF MACHINING PARAMETERS FOR EDM USING EN-31 AND HCHCr WORK PIECE during academic session 2011-2012 under the guidance of PROF. RAJESH MADARKAR as prescribed by Nagpur university and their work has been satisfactory PROJECT GUIDE PROF. RAJESH MADARKAR HEAD OF DEPARTMENT PROF. K. N. AGRAWAL PRINCIPAL Dr. V. S. DESHPANDE Acknowledgement Hard work, sincerity and proper guidance that’s what on needs to be successful in life, that is what we have realized working on a project No successful work can ever be the effect of a individual effort. We take this opportunity to express our deep gratitude towards everyone who has been of immense help throughout and till completion of this work. We earnestly express our thankfulness to Prof . Rajesh Madarkar , without whose invaluable guidance the present work would not see light of this day. The work would have been impossible without his co-operation and direction. In spite of being our teacher, his friendly approach has been constant source of inspiration and encouragement. We are really honored to have such a wonderful person as our guide. We are also thankful to the director of Dulocos Conveyors And Moulds Pvt. Ltd Mr. Khalid Husain We are also grateful towards everyone who has directly or indirectly contributed with their lively suggestions to make the project a success. CHAPTER 1 INTRODUCTION 1. 1 Background of EDM The history of EDM Machining Techniques goes as far back as the 1770s when it was discovered by an English Scientist. However, Electrical Discharge Machining was not fully taken advantage of until 1943 when Russian scientists learned how the erosive effects of the technique could be controlled and used for machining purposes. When it was originally observed by Joseph Priestly in 1770, EDM Machining was very imprecise and riddled with failures. Commercially developed in the mid 1970s, wire EDM began to be a viable technique that helped shape the metal working industry we see today. In the mid 1980s. The EDM techniques were transferred to a machine tool. This migration made EDM more widely available and appealing over traditional machining processes. The new concept of manufacturing uses non-conventional energy sources like sound, light, mechanical, chemical, electrical, electrons and ions. With the industrial and technological growth, development of harder and difficult to machine materials, which find wide application in aerospace, nuclear engineering and other industries owing to their high strength to weight ratio, hardness and heat resistance qualities has been witnessed. New developments in the field of material science have led to new engineering metallic materials, composite materials and high tech ceramics having good mechanical properties and thermal characteristics as well as sufficient electrical conductivity so that they can readily be machined by spark erosion. Nontraditional machining has grown out of the need to machine these exotic materials. The machining processes are non-traditional in the sense that they do not employ traditional tools for metal removal and instead they directly use other forms of energy. The problems of high complexity in shape, size and higher demand for product accuracy and surface finish can be solved through non-traditional methods. Currently, non-traditional processes possess virtually unlimited capabilities except for volumetric material removal rates, for which great advances have been made in the past few years to increase the material removal rates. As removal rate increases, the cost effectiveness of operations also increase, stimulating ever greater uses of nontraditional process. The Electrical Discharge Machining process is employed widely for making tools, dies and other precision parts. EDM has been replacing drilling, milling, grinding and other traditional machining operations and is now a well established machining option in many manufacturing industries throughout the world. And is capable of machining geometrically complex or hard material components, that are precise and difficult-to-machine such as heat treated tool steels, composites, super alloys, ceramics, carbides, heat resistant steels etc. being widely used in die and mold making industries, aerospace, aeronautics and nuclear industries. Electric Discharge Machininghas also made its presence felt in the new fields such as sports, medical and surgical, instruments, optical, including automotive RD areas. 1. 2 Introduction of EDM Electro Discharge Machining (EDM) is an electro-thermal non-traditional machining Process, where electrical energy is used to generate electrical spark and material removal mainly occurs due to thermal energy of the spark. You read "Electric Discharge Machining" in category "Essay examples" EDM is mainly used to machine difficult-to-machine materials and high strength temperature resistant alloys. EDM can be used to machine difficult geometries in small batches or even on job-shop basis. Work material to be machined by EDM has to be electrically conductive. 1. 3 Principle of EDM In this process the metal is removing from the work piece due to erosion case by rapidly recurring spark discharge taking place between the tool and work piece. Show the mechanical set up and electrical set up and electrical circuit for electro discharge machining. A thin gap about 0. 025mm is maintained between the tool and work piece by a servo system shown in fig 1. 1. Both tool and work piece are submerged in a dielectric fluid . Kerosene/EDM oil/deionized water is very common type of liquid dielectric although gaseous dielectrics are also used in certain cases. Figure1. 1 Set up of Electric discharge machining This fig. 1. 1 is shown the electric setup of the Electric discharge machining. The tool is made cathode and work piece is anode. When the voltage across the gap becomes sufficiently high it discharges through the gap in the form of the spark in interval of from 10 of micro seconds. And positive ions and electrons are ccelerated, producing a discharge channel that becomes conductive. It is just at this point when the spark jumps causing collisions between ions and electrons and creating a channel of plasma. A sudden drop of the electric resistance of the previous channel allows that current density reaches very high values producing an increase of ionization and the creation of a powerful magnetic field. The moment spark occurs sufficiently pressure developed between work and tool as a result of which a very high temperature is reached and at such high pressure and temperature that some metal is melted and eroded. Such localized extreme rise in temperature leads to material removal. Material removal occurs due to instant vaporization of the material as well as due to melting. The molten metal is not removed completely but only partially As the potential difference is withdrawn as shown in Fig. 1. 2, the plasma channel is no longer sustained. As the plasma channel collapse, it generates pressure or shock waves, which evacuates the molten material forming a crater of removed material around the site of the spark. 1. 4 Types of EDM Basically, there are two different types of EDM: 1. 4. 1) Die-sinking 1. 4. 2) wire-cut. 1. 4. 1Die-sinking EDM In the Sinker EDM Machining process, two metal parts submerged in an insulating liquid are connected to a source of current which is switched on and off automatically depending on the parameters set on the controller. When the current is switched on, an electric tension is created between the two metal parts. If the two parts are brought together to within a fraction of an inch, the electrical tension is discharged and a spark jumps across. Where it strikes, the metal is heated up so much that it melts. Sinker EDM, also called cavity type EDM or volume EDM consists of an electrode and workpiece submerged in an insulating liquid such as, more typically, oil or, less frequently, other dielectric fluids. The electrode and workpiece are connected to a suitable power supply. The power supply generates an electrical potential between the two parts. As the electrode approaches the workpiece, dielectric breakdown occurs in the fluid, forming a plasma channel, and a small spark jumps. These sparks usually strike one at a time because it is very unlikely that different locations in the inter-electrode space have the identical local electrical characteristics which would enable a spark to occur simultaneously in all such locations. These sparks happen in huge numbers at seemingly random locations between the electrode and the workpiece. As the base metal is eroded, and the spark gap subsequently increased, the electrode is lowered automatically by the machine so that the process can continue uninterrupted. Several hundred thousand sparks occur per second, with the actual duty cycle carefully controlled by the setup parameters. 1. 4. 2 Wire-cut EDM Wire EDM Machining (also known as Spark EDM) is an electro thermal production process in which a thin single-strand metal wire (usually brass) in conjunction with de-ionized water (used to conduct electricity) allows the wire to cut through metal by the use of heat from electrical sparks. a thin single-strand metal wire, usually brass, is fed through the workpiece, submerged in a tank of dielectric fluid, typically deionized water. Wire-cut EDM is typically used to cut plates as thick as 300mm and to make punches, tools, and dies from hard metals that are difficult to machine with other methods. Wire-cutting EDM is commonly used when low residual stresses are desired, because it does not require high cutting forces for removal of material. If the energy/power per pulse is relatively low (as in finishing operations), little change in the mechanical properties of a material is expected due to these low residual stresses, although material that hasn’t been stress-relieved can distort in the machining process. Due to the inherent properties of the process, wire EDM can easily machine complex parts and precision components out of hard conductive mate 1. 12 Application of EDM 1. The EDM process is most widely used by the mould-making tool and die industries, but is becoming a common method of making prototype and production parts, especially in the aerospace, automobile and electronics industries in which production quantities are relatively low. 2. It is used to machine extremely hard materials that are difficult to machine like alloys, tool steels, tungsten carbides etc. 3. It is used for forging, extrusion, wire drawing, thread cutting. . It is used for drilling of curved holes. 5. It is used for internal thread cutting and helical gear cutting. 6. It is used for machining sharp edges and corners that cannot be machined effectively by other machining processes. 7. Higher Tolerance limits can be obtained in EDM machining. Hence areas that require higher surface accuracy use the EDM machini ng process. 8. Ceramic materials that are difficult to machine can be machined by the EDM machining process. 9. Electric Discharge Machining has also made its presence felt in the new fields such as sports, medical and surgical, instruments, optical, including automotive R areas. 0. It is a promising technique to meet increasing demands for smaller components usually highly complicated, multi-functional parts used in the field of microelectronics. 1. 13 Advantages of EDM (a) Any material that is electrically conductive can be cut using the EDM process. (b) Hardened workpieces can be machined eliminating the deformation caused by heat treatment. (c) X, Y, and Z axes movements allow for the programming of complex profiles using simple electrode. (d) Complex dies sections and molds can be produced accurately, faster, and at lower costs. Due to the modern NC control systems on die sinking machines, even more complicated work pieces can be machined. (e) The high degree of automation and the use of tool and work piece changers allow the machines to work unattended for overnight or during the weekends (f) Forces are produced by the EDM-process and that, as already mentioned, flushing and hydraulic forces may become large for some work piece geometry. The large cutting forces of the mechanical materials removal processes, however, remain absent. (g) Thin fragile sections such as webs or fins can be easily machined without deforming the part. . 14 Limitation of EDM (a) The need for electrical conductivity – To be able to create discharges, the work piece has to be electrically conductive. Isolators, like plastics, glass and most ceramics, cannot be machined by EDM, although some exception like for example diamond is known. Machining of partial conductors like Si semi-conductors, partially conductive ceramics and ev en glass is also possible. (b) Predictability of the gap – The dimensions of the gap are not always easily predictable, especially with intricate work piece geometry. In these cases, the flushing conditions andthe contamination state of differ from the specified one. In the case of die-sinking EDM, the tool wear also contributes to a deviation of the desired work piece geometry and it could reduce the achievable accuracy. Intermediate measuring of the work piece or some preliminary tests can often solve the problems. (c) Low material removal rate- The material removal of the EDM-process is rather low, especially in the case of die-sinking EDM where the total volume of a cavity has to be removed by melting and evaporating the metal. With wire-EDM only the outline of the desired work piece shape has to be machined. Due to the low material removal rate, EDM is principally limited to the production of small series although some specific mass production applications are known. (d) Optimization of the electrical parameters – The choice of the electrical parameters of the EDM-process depends largely on the material combination of electrode and work piece and EDM manufactures only supply these parameters for a limited amount of material combinations. When machining special alloys, the user has to develop his own technology. CHAPTER 2 LITRATURE SURVEY 2. 1 INTRODUCTION Literature review is one of the scope studies. It works as guide to run this analysis. It will give part in order to get the information about electrical discharge machine (EDM) and will give idea to operate the test. From the early stage of the project, various literature studies have been done. Research journals, books, printed or online conference article were the main source in the project guides. Literature review section work as reference, to give information and guide base on journal and other source in the media. 2. Important parameters of EDM (a) Spark On-time (pulse time or Ton): The duration of time (? s) the current is allowed to flow per cycle. Material removal is directly proportional to the amount of energy applied during this on-time. This energy is really controlled by the peak current and the length of the on-time. (b) Spark Off-time (pause time or Toff ): The duration of time (? s) between the sparks (that is to say, on- time). This time allows the molten material to solidify and to be wash out of the arc gap. This parameter is to affect the speed and the stability of the cut. Thus, if the off-time is too short, it will cause sparks to be unstable. (c) Arc gap (or gap): The Arc gap is distance between the electrode and workpiece during the process of EDM. It may be called as spark gap. Spark gap can be maintained by servo system (fig no. -1). (d) Discharge current (current Ip): Current is measured in amp Allowed to per cycle. Discharge current is directly proportional to the Material removal rate. (e) Duty cycle (? ): It is a percentage of the on-time relative to the total cycle time. This parameter is calculated by dividing the on-time by the total cycle time (ontime pulse offtime). f) Voltage (V): It is a potential that can be measure by volt it is also effect to the material removal rate and allowed to per cycle. Voltage is given by in this experiment is 50 V. (g) Diameter of electrode (D): It is the electrode of Cu-tube there are two different size of diameter 4mm and 6mm in this experiment. This tool is used not only as a electrode but also for intern al flushing. (h) Over cut – It is a clearance per side between the electrode and the workpiece after the marching operation. 2. 3 Characteristics of EDM EDM specification by mechanism of process, metal removal rate and other function that shown in this table no . 1 2. 4 Dielectric fluid In EDM, as has been discussed earlier, material removal mainly occurs due to thermal evaporation and melting. As thermal processing is required to be carried out in absence of oxygen so that the process can be controlled and oxidation avoided. Oxidation often leads to poor surface conductivity (electrical) of the work piece hindering further machining. Hence, dielectric fluid should provide an oxygen free machining environment. Further it should have enough strong dielectric resistance so that it does not breakdown electrically too easily but at the same time ionize when electrons collide with its molecule. Moreover, during sparking it should be thermally resistant as well. The dielectric fluid has the following functions: (a) It helps in initiating discharge by serving as a conducting medium when ionised, and conveys the spark. It concentrates the energy to a very narrow region. (b) It helps in quenching the spark, cooling the work, tool electrode and enables arcing to be prevented. c) It carries away the eroded metal along with it. (d) It acts as a coolant in quenching the sparks. The electrode wear rate, metal removal rate and other operation characteristics are also influenced by the dielectric fluid. The dielectric generally fluid used are transformer on silicon oil, EDM oil, kerosene (paraffin oil) and de-ionized water are used as dielectric fluid in EDM. Tap water cannot be used as it ionizes too ear ly and thus breakdown due to presence of salts as impurities occur. Dielectric medium is generally flushed around the spark zone. It is also applied through the tool to achieve efficient removal of molten material. In this experiment using the Commercial grade EDM oil (specific gravity= 0. 763, freezing point= 94 °C) was used as dielectric fluid are used it is using as coolant and medium of workpiece and tool during the process of erosion. 2. 5. Flushing method Flushing is the most important function in any electrical discharge machining operation. Flushing is the process of introducing clean filtered dielectric fluid into the spark gap. There are a number of flushing methods used to remove the metal particles efficiently. 2. 5. Tool Material Tool material should be such that it would not undergo much tool wear when it is impinged by positive ions. Thus the localized temperature rise has to be less by tailoring or properly choosing its properties or even when temperature increases, there would be less melting. Further, the tool should be easily workable as intricate shaped geometric features are machined in EDM. Thus the basic characteristics of electrode materials are: 1. High electrical conductivity – electrons are cold emitted more easily and there is less bulk electrical heating. 2. High thermal conductivity – for the same heat load, the local temperature rise would be less due to faster heat conducted to the bulk of the tool and thus less tool wear. 3. Higher density – for the same heat load and same tool wear by weight there would be less volume removal or tool wear and thus less dimensional loss or inaccuracy. 4. High melting point – high melting point leads to less tool wear due to less tool material melting for the same heat load. 5. Easy manufacturability. 6. Cost – cheap. The followings are the different electrode materials which are used commonly in the industry: 1. Graphite 2. copper 3. Tellurium copper – 99% Cu + 0. 5% tellurium 4. Brass 2. 6. Design variable Design parameter, process parameter and constant parameter are following ones, Design parameters – 1. Material removal rate. 2. Tool wear rate 3. Over cut (OC) Machining parameter – 1. Discharge current (Ip) 2. Pulse on time (Ton) 3. Diameter of U-shaped tool Constant parameter1. Duty cycle 2. Voltage 3. Flushing pressure 4. Polarity 2. 7. Workpiece material It is capable of machining geometrically complex or hard material components, that are precise and difficult-to-machine such as heat treated tool steels, composites, super alloys, ceramics, carbides, heat resistant steels etc. There are different types of tool material are using the EDM method. And the tool steel contains carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures (red-hardness). Tool steel is generally used in a heattreated state. Tool steels are made to a number of grades for different applications. In general, the edge temperature under expected use is an important determinant of both composition and required heat treatment. The higher carbon grades are typically used for such applications as stamping dies, metal cutting tools, etc. 2. 8 MACHINING PARAMETER SELECTION In this project , material removal rate (MRR) is important. This characteristic material removal rate (MRR) is a major influence resulting the machining performance. Among the numerous parameters affecting the EDM performance, the dielectric fluid has a very important role. The physical properties of the fluid influence the breakdown voltage and the ignition delay: however, the debris concentration in the fluid modifies these parameters, decreasing the dielectric strength by many orders of magnitude . But this parameter is neglect due to limitation of scope of studies. Surface roughness is also a very important parameter but is not taken into consideration due to unavailability of perthometer. 2. 9 MACHINING PERFORMANCE EVALUATION Material removal rate (MRR) is used to evaluate machining performance. The material removal rate (MRR) is expressed as the work piece removal rate (WRW) under a period of machining time in minute (T), which is : Ww=Weight loss Pw= Density of material The density of materials was measured on basis of volume displacement method using weighing machine and beaker 2. 10. Objective of the present work From the research papers refered , it is observed that few works has been reported on EDM on the material Al-Sic, EN-19, SKH 57 and various composite materials. The objective of the present work is an attempt to finding the effect of machining parameters on EN-31,HCHCr for material removal rate using a pure copper electrode . The machining parameter selected for experiment are pulse on time ,peak current and duty cycle ,using one variable at a time approach analysis for responses MRR has been carried out. CHAPTER 3 EXPERIMENTAL SETUP 3. 1 LABORATARY USED:1. ENVIRONMENTAL ENGINEERING LAB USED FOR WEIGHING WORKPIECE 2. WORKSHOP USED FOR CONDUCTING EXPERIMENT ON EDM 3. 2 Materials Used 1. 2. 3. 1. HCHCR (55-56) 2. HCHCR (20-22) 3. EN-31 (20-22) ELECTRODE Uses of Workpiece Materials: EN 31: †¢ High tensile strength machine parts. †¢ Gears and pinions. †¢ Axles †¢ Shafts †¢ Connecting rods †¢ Plastic moulds †¢ Forging dies for smaller section of ferrous non-ferrous items. HCHCr: †¢ Plastic moulding †¢ Dies †¢ Hot shearing tools †¢ Hardened rolls †¢ Thread rolling dies HARDNESS DEFINITION : †¢ It’s the ability of the material to resist permanent shape change. †¢ Rockwell scale is a hardness scale based on indentation hardness of material in which resistance of permanent plastic deformation due to a constant compression load from a sharp object †¢ Rockwell intrument used from DULOCOS CONVEYORS AND MOULDS PVT. LTD. DENSITY =Mass/Volume 1. Measured the mass of workpiece from weighing machine. 2. Measured the volume displaced with the help of beaker. 3. 3 EXPERIMENTAL CONDITIONS WORKING PARAMETERS Work piece materials DESCRIPTION EN-31(20-22),HCHCR(2022), HCHCR(55-56) Copper(Cu) Positive Kerosene 4,6,8 amps 35,45,55,65 TYPE CONSTANT Electrode Material Electrode Polarity Dielectric Fluid Peak Current(Ip) Pulse Duration(Ton) CONSTANT CONSTANT CONSTANT VARIABLE VARIABLE Duty Factor Working Time (Ton variable) 9 40 mins CONSTANT CONSTANT CONSTANT Working Time (Ip variable) 30 mins . 4 CALCULATING MRR: FORMULA USED Where: Ww: Weight of the material in gms. ?w : Density of the material in gm/cm3. T : Machining time in mins. CHAPTER 4 OBSERVATIONS AND RESULTS 4. 1 MATERIAL : EN-31 , HARDNESS : 20-22 ON ROCKWELL SCALE DENSITY: 5. 57 g/cm3 CHANGING PARAMETER: PULSE ON TIME(Ti) CHANGING PARAMETER: PEAK CURRENT (Ip) 4. 2 MATERIAL : HCHCr , HARDNESS : 20-22 ON ROCKWELL SCALE DENSITY: 5. 228 g/cm3 CHANGI NG PARAMETER: PULSE ON TIME(Ti) CHANGING PARAMETER: PEAK CURRENT (Ip) 4. 3 MATERIAL : HCHCr , HARDNESS : 55-56 ON ROCKWELL SCALE DENSITY: 8. 47 g/cm3 CHANGING PARAMETER: PULSE ON TIME(Ti) CHANGING PARAMETER: PEAK CURRENT (Ip) CHAPTER 5 RESULT ANALYSIS †¢ The experiments are based on one factor experiment strategy. †¢ In this only one input parameter was varied while keeping all others input parameters at constant values. †¢ During this experimental procedure, 6 sets of experiments were performed varying the Peak current( Ip) and Pulse time on (Ton) for three different materials. After analyzing the results of the experiments performed, various facts came into light. EXPERIMENT SET 1 PULSE ON TIME IS INCREASED The above graphs shows that material removal rate increases with the increase in the pulse on time and decreases after some time. So the pulse on time can be adjusted to get the desired material removal rate. The Declining Trend Of Graph †¢ Ton:- During puls e on time spark erosion takes place and metal is melted/vapourized †¢ Toff:-During pulse off time metal is washed away and solidified †¢ But as the Ton is increased at constant Input parameters, Toff starts to decrease due to which metal is stuck and is not removed properly and MRR decreases EXPERIMENT SET 2 PEAK CURRENT IS INCREASED †¢ The above graphs shows that material removal rate increases with the increase in the peak current. So value of peak current should be high to obtain higher MRR. CHAPTER 6 CONCLUSION The following conclusions are drawn from the experimental study: 1. The parameter PEAK CURRENT (IP) has direct effect on material removal rate as we increase peak current material removal rate increases 2. The PULSE ON TIME parameter has direct effect on the material removal rate with a declining trend, as we increase the pulse on time the material removal rate increases upto a certain level but starts to decrease after certain time. REFERENCES †¢ Saurabh kumar saha, Experimental Investigation of the Dry Electric Discharge Machining (Dry EDM) Process †¢ S. H. Tomadi, M. A. Hassan, Z. Hamedon, IAENG R. Daud, A. G. Khalid, Analysis of the Influence of EDM Parameters on Surface Quality and Electrode Wear of Tungsten Carbide †¢ M. M. Rahman, Md. Ashikur Rahman Khan, K. Kadirgama M. M. Noor and Rosli A. Bakar, Modeling of Material Removal on Machining of Ti-6Al-4V through EDM using Copper Tungsten Electrode and Positive Polarity †¢ Mohd Abd Larif Bin Abd Ghani, Effects Of Surface Roughness Using Different Electrodes On Electrical Discharge Machining (EDM) †¢ Mr. V. D. Patel, Prof. C. P. Patel , Mr. U. J. Patel, Analysis of Different Tool Material On MRR and Surface Roughness of Mild Steel In EDM INDEX 1. INTRODUCTION 2. LITERATURE SURVEY 3. EXPERIMENTAL SETUP 4. OBSERVATIONS AND RESULTS 5. RESULT ANALYSIS 6. CONCLUSION 7. REFERENCES How to cite Electric Discharge Machining, Essay examples Electric Discharge Machining Free Essays ELECTRIC DISCHARGE MACHINING INTRODUCTION * Sometimes it is referred to as spark machining, * Its a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks). * Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. * One of the electrodes – ‘tool-electrode’ or ‘tool’ or ‘electrode’. We will write a custom essay sample on Electric Discharge Machining or any similar topic only for you Order Now * Other electrode – workpiece-electrode or ‘workpiece’. As distance between the two electrodes is reduced, the current intensity becomes greater than the strength of the dielectric (at least in some points) causing it to break. * EDM is a machining method primarily used for hard metals or those that would be very difficult to machine with traditional techniques. * EDM typically works with materials that are electrically conductive, although methods for machining insulating ceramics with EDM have been proposed. * EDM can cut intricate contours or cavities in hardened steel without the need for heat treatment to soften and re-harden them. This method can be used with any other metal or metal alloy such as titanium, hastelloy, kovar, and inconel. EDM – Working Principle * It is a process of metal removal based on the principle of material removal by an interrupted electric spark discharge between the electrode tool and the work piece. * In EDM, a potential di fference is applied between the tool and workpiece. * Essential – Both tool and work material are to be conductors. * The tool and work material are immersed in a dielectric medium. * Generally kerosene or deionised water is used as the dielectric medium. A gap is maintained between the tool and the workpiece. * Depending upon the applied potential difference (50 to 450 V) and the gap between the tool and workpiece, an electric field would be established. * Generally the tool is connected to the negative terminal (cathode) of the generator and the workpiece is connected to positive terminal (anode). * The high speed electrons then impinge on the job and ions on the tool. * The kinetic energy of the electrons and ions on impact with the surface of the job and tool respectively would be converted into thermal energy or heat flux. Such intense localized heat flux leads to extreme instantaneous confined rise in temperature which would be in excess of 10,000oC. * Such localized ex treme rise in temperature leads to material removal. * Material removal occurs due to instant vaporization of the material as well as due to melting. * The molten metal is not removed completely but only partially. EDM – Dielectric * In EDM, material removal mainly occurs due to thermal evaporation and melting. * As thermal processing is required to be carried out in absence of oxygen so that the process can be controlled and oxidation avoided. Oxidation often leads to poor surface conductivity (electrical) of the workpiece hindering further machining. * Hence, dielectric fluid should provide an oxygen free machining environment. * Further it should have enough strong dielectric resistance so that it does not breakdown electrically too easily. * But at the same time, it should ionize when electrons collide with its molecule. * Moreover, during sparking it should be thermally resistant as well. * Generally kerosene and deionised water is used as dielectric fluid in EDM. How to cite Electric Discharge Machining, Papers

Editha Essay Example For Students

Editha Essay EDITHAThis story is about a woman named Editha. Editha was engaged to George and told him it was his duty to his country to sign up and go serve in the war. Editha wanted a hero for a husband and she secretly wanted him to go to war so that she would have that hero. After an argument with him she finally convinces him to go. George dies in the war and his mother blames Editha for his death. Editha is in denial and accepts no responsibility for the death of George or the reasons that he chose to go to war in the first place. Editha was engaged to a man named George Gearson. A war had begun and Editha became excited about the concept of having a hero for a husband. Editha, right away started encouraging George to sign up for the war, she believed it was his patriotic duty as an American. George did not believe in war and was raised to be passive. Georges father had lost his arm in the Civil war and his mother did not want him to suffer the same thing. His father and mother together decided to discourage George from going to any war. George and Editha got in a heated argument about the war and their different opinions and he left to go out. George told her he would come back for dinner. At this point Editha considered their relationship over. She did not see how she could continue to love a man who did not love his country as much as she did. When George left, that was it for Editha. She decided that if he could not believe the way she did then he did not deserve her. She sat down and wrote him a letter a nd gathered all the things he had ever given her and put them all in a box. In the letter, she told him that she could not be with a man who was not loyal to his country first of all. She could not be with a man who did not believe the way she did and therefore she was breaking up with him. After thinking it over, Editha decided that she was jumping the gun and that since George said he would think about what she had said, that she would give him a chance to think her way, which she considered the only way. George went out to a bar that night and had a few too many drinks with his friends. After a few drinks he became a little more patriotic and signed up for the war and even encouraged his friends to do the same. His friends even nicknamed him Captain because of his leadership in encouraging them to sign up. George showed up late that night at Edithas house to tell her that he signed up for the war. Editha was very excited but tried not to show it. She did not want him to think that she was the one who pushed him into signing up. Editha just listened to him and encouraged him and told him that he did the right thing. George asked Editha to do one thing when he was getting ready to leave and that was to take care of his mother if anything should happen to him. He told her that his mother would not be happy with him for signing up for the war but that he wanted to make sure she was taken care of if he dies in the war. Editha said she would be more than happy to check on his mother, but that nothing would happen to him. He would come back to her as a hero.Editha handed George the letter that she had written him earlier before she had learned that the had signed up. Editha told him if he ever doubted his decision to sign up he should just read the letter that she had written him and he would know that he had done the right thing. He got on the train, waived goodbye and that was the last time she saw him. .uda63eace7264a0b5e8291cb7b996fc57 , .uda63eace7264a0b5e8291cb7b996fc57 .postImageUrl , .uda63eace7264a0b5e8291cb7b996fc57 .centered-text-area { min-height: 80px; position: relative; } .uda63eace7264a0b5e8291cb7b996fc57 , .uda63eace7264a0b5e8291cb7b996fc57:hover , .uda63eace7264a0b5e8291cb7b996fc57:visited , .uda63eace7264a0b5e8291cb7b996fc57:active { border:0!important; } .uda63eace7264a0b5e8291cb7b996fc57 .clearfix:after { content: ""; display: table; clear: both; } .uda63eace7264a0b5e8291cb7b996fc57 { display: block; transition: background-color 250ms; webkit-transition: background-color 250ms; width: 100%; opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #95A5A6; } .uda63eace7264a0b5e8291cb7b996fc57:active , .uda63eace7264a0b5e8291cb7b996fc57:hover { opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #2C3E50; } .uda63eace7264a0b5e8291cb7b996fc57 .centered-text-area { width: 100%; position: relative ; } .uda63eace7264a0b5e8291cb7b996fc57 .ctaText { border-bottom: 0 solid #fff; color: #2980B9; font-size: 16px; font-weight: bold; margin: 0; padding: 0; text-decoration: underline; } .uda63eace7264a0b5e8291cb7b996fc57 .postTitle { color: #FFFFFF; font-size: 16px; font-weight: 600; margin: 0; padding: 0; width: 100%; } .uda63eace7264a0b5e8291cb7b996fc57 .ctaButton { background-color: #7F8C8D!important; color: #2980B9; border: none; border-radius: 3px; box-shadow: none; font-size: 14px; font-weight: bold; line-height: 26px; moz-border-radius: 3px; text-align: center; text-decoration: none; text-shadow: none; width: 80px; min-height: 80px; background: url(https://artscolumbia.org/wp-content/plugins/intelly-related-posts/assets/images/simple-arrow.png)no-repeat; position: absolute; right: 0; top: 0; } .uda63eace7264a0b5e8291cb7b996fc57:hover .ctaButton { background-color: #34495E!important; } .uda63eace7264a0b5e8291cb7b996fc57 .centered-text { display: table; height: 80px; padding-left : 18px; top: 0; } .uda63eace7264a0b5e8291cb7b996fc57 .uda63eace7264a0b5e8291cb7b996fc57-content { display: table-cell; margin: 0; padding: 0; padding-right: 108px; position: relative; vertical-align: middle; width: 100%; } .uda63eace7264a0b5e8291cb7b996fc57:after { content: ""; display: block; clear: both; } READ: Two Kinds By Amy Tan EssayThe first skirmish that his battalion was involved in returned a lot of causalities. George was one of the men on the list that was killed. Editha looked and looked at the list hoping that there might be another Gearson, but everything matched up. Just like she promised, Editha got up out of sick and distraught bed and went to check on Georges mother. Edithas father offered to go with her and they traveled from New York to Iowa to Georges funeral. Georges mother blamed Editha for everything. The letter that Editha had given George had made its way back to the states and into the hands of Georges mother. Now Georges mother blamed her for his death and said that she pushed George to go to war. She said that George would have never gone on his own. This shocked Editha and she did not know what to say. In the end, Editha is having her picture painted and the lady doing the painting is commenting on how Georges mother treated Editha. She remarks that it was cruel of the woman to treat Editha that way after Editha got up out of her sick bed to go all that way to comfort her. Up until this point Editha had been depressed about what Georges mother had said to her and maybe was even questioning whether any of it was true. The remarks this lady said made her feel better and she went back to her old self, with no remorse in what she had said or done to cause the death of George. This story is about human emotions with the war looming heavily in the background. Editha wants George to go to war, but not really because she thinks it is his civic duty as she implies. Editha wants George to go to war because she thinks he should prove himself to her. Editha wants George to go to war for the completion of her idea of him. She feels that she deserves the best and that a war hero would be a nice conversation piece to have dinner parties. Editha does things and says things in a round about way so that George can not tell she is actually doing it. She says things that are implied but not said plainly. This way she gets her point across but does not look like she is just pushing him off to war. Human beings depend on other human beings to give them a sense purpose. Sometimes one needs other people to do or say things to make one feel as if we have been on this earth for a reason. In Edithas case, she needed George to prove to her his sense of purpose and to prove to her that he had a reason to be on this earth. Editha felt like George needed to prove to her that he deserved her. If he could not prove to her that he deserved her then she would just dump him. This writer does not think there could have been love in this relationship on the part of Editha. How could you put such conditions on love. How could one send the person they love of to war just to complete their idea of t hat person. This story was tragic because a man lost his life trying to prove his love for a woman who really only wanted him around as a showpiece. Editha does not realize what love really is and what is saddest of all is poor George died for it.