The document summarizes electron beam machining (EBM). EBM uses a focused beam of high-energy electrons to melt and vaporize metal, allowing for precise machining. There are two types - thermal EBM uses the beam's heat to selectively vaporize material, while non-thermal EBM causes surface chemical reactions. The document discusses the generation and control of electron beams, the physical processes involved in thermal EBM, and a phenomenological theory of non-thermal EBM film growth proposed by Christly.
This document discusses heat treatment of steel using microwave energy and compares it to conventional heating. It begins with introducing microwaves and how they can be used to heat materials. Steel grade C30 is then discussed, along with heat treatment of materials generally. Microwave processing of materials is described, noting its advantages over conventional heating like rapid and uniform volumetric heating. How different materials interact with microwaves is explained. While metals do not heat well with microwaves, the document discusses how they can be heated using a susceptor. The objectives of comparing microwave versus conventional heat treatment of C30 steel are then stated. Finally, relevant literature on microwave processing of metals is reviewed.
Electron beam machining by Himanshu VaidHimanshu Vaid
Electron beam machining uses a stream of electrons accelerated to high velocities by a potential difference of around 30kv. The electron beam is focused and directed towards the workpiece, where the kinetic energy of the electrons is transferred as heat to melt or vaporize small areas of the material. This process must occur in a vacuum to prevent energy loss from collisions with air molecules. Electron beam machining is used for cutting narrow slots, drilling fine holes, marking, welding, and other thermal processing applications where precise localized heating is needed.
This document discusses electron beam machining (EBM). EBM uses a focused beam of high-velocity electrons to melt and vaporize material from a workpiece. It operates within a vacuum chamber at pressures of 10^-5 mm Hg. The electron gun generates the beam using a tungsten filament, grid cup, and anode. The beam is focused by electromagnetic lenses and its path is controlled by deflector coils. EBM can machine any material, achieves close tolerances with no tool wear, and concentrates heat at a small spot. However, it requires high vacuum and power while providing a low material removal rate. Applications include microdrilling and machining materials with low thermal conductivity.
This document discusses gas-filled tubes, which contain a small amount of inert gas at low pressure. There are two main types: cold-cathode tubes, which use natural electron emission, and hot-cathode tubes, which have a heated cathode. Gas-filled tubes can conduct more current than vacuum tubes because electron collisions ionize gas molecules, increasing the number of charge carriers. They also have less control over electron flow than vacuum tubes. Common applications include voltage regulation, rectification, switching, and radio frequency detection.
This document discusses different types of electron emission from metal surfaces. Thermionic emission occurs when heat is applied to a metal, increasing the kinetic energy of electrons and allowing them to overcome the surface barrier. Common thermionic emitters discussed are tungsten, thoriated tungsten, and oxide coatings, with their respective work functions and operating temperatures listed. The Richardson-Dushman equation describes how emission current density increases exponentially with temperature but depends on the work function of the emitter material.
Electron beam machining (EBM) is a high-energy beam process invented in 1952 that uses an electron beam to remove material. Electrons are generated and accelerated to high velocities, focusing the beam into a small spot to intensely heat and melt or vaporize material. The process occurs inside a vacuum chamber to prevent electron scattering. Key parameters that control the machining include accelerating voltage, beam current, pulse duration and spot size. EBM can drill small, high aspect ratio holes and cut intricate shapes in a wide range of materials.
Term Paper - Field Assisted Thermionic Emission, Field Emission, and Applicat...Adeagbo Bamise
This document summarizes different types of electron emission from heated metals, including thermionic emission, field emission, and field-assisted thermionic emission (Schottky emission). Thermionic emission occurs when thermal energy from heating overcomes the work function of a metal, allowing electrons to escape. Field emission occurs at room temperature when a strong electric field lowers the potential barrier for electrons. Schottky emission applies an electric field to enhance thermionic emission and lower the barrier at lower temperatures than normal thermionic emission. These emission types find applications in devices like vacuum tubes.
Superconductivity is the ability of certain materials to conduct electric current with practically zero resistance. This capacity produces interesting and potentially useful effects. For a material to behave as a superconductor, low temperatures are required.
This document discusses heat treatment of steel using microwave energy and compares it to conventional heating. It begins with introducing microwaves and how they can be used to heat materials. Steel grade C30 is then discussed, along with heat treatment of materials generally. Microwave processing of materials is described, noting its advantages over conventional heating like rapid and uniform volumetric heating. How different materials interact with microwaves is explained. While metals do not heat well with microwaves, the document discusses how they can be heated using a susceptor. The objectives of comparing microwave versus conventional heat treatment of C30 steel are then stated. Finally, relevant literature on microwave processing of metals is reviewed.
Electron beam machining by Himanshu VaidHimanshu Vaid
Electron beam machining uses a stream of electrons accelerated to high velocities by a potential difference of around 30kv. The electron beam is focused and directed towards the workpiece, where the kinetic energy of the electrons is transferred as heat to melt or vaporize small areas of the material. This process must occur in a vacuum to prevent energy loss from collisions with air molecules. Electron beam machining is used for cutting narrow slots, drilling fine holes, marking, welding, and other thermal processing applications where precise localized heating is needed.
This document discusses electron beam machining (EBM). EBM uses a focused beam of high-velocity electrons to melt and vaporize material from a workpiece. It operates within a vacuum chamber at pressures of 10^-5 mm Hg. The electron gun generates the beam using a tungsten filament, grid cup, and anode. The beam is focused by electromagnetic lenses and its path is controlled by deflector coils. EBM can machine any material, achieves close tolerances with no tool wear, and concentrates heat at a small spot. However, it requires high vacuum and power while providing a low material removal rate. Applications include microdrilling and machining materials with low thermal conductivity.
This document discusses gas-filled tubes, which contain a small amount of inert gas at low pressure. There are two main types: cold-cathode tubes, which use natural electron emission, and hot-cathode tubes, which have a heated cathode. Gas-filled tubes can conduct more current than vacuum tubes because electron collisions ionize gas molecules, increasing the number of charge carriers. They also have less control over electron flow than vacuum tubes. Common applications include voltage regulation, rectification, switching, and radio frequency detection.
This document discusses different types of electron emission from metal surfaces. Thermionic emission occurs when heat is applied to a metal, increasing the kinetic energy of electrons and allowing them to overcome the surface barrier. Common thermionic emitters discussed are tungsten, thoriated tungsten, and oxide coatings, with their respective work functions and operating temperatures listed. The Richardson-Dushman equation describes how emission current density increases exponentially with temperature but depends on the work function of the emitter material.
Electron beam machining (EBM) is a high-energy beam process invented in 1952 that uses an electron beam to remove material. Electrons are generated and accelerated to high velocities, focusing the beam into a small spot to intensely heat and melt or vaporize material. The process occurs inside a vacuum chamber to prevent electron scattering. Key parameters that control the machining include accelerating voltage, beam current, pulse duration and spot size. EBM can drill small, high aspect ratio holes and cut intricate shapes in a wide range of materials.
Term Paper - Field Assisted Thermionic Emission, Field Emission, and Applicat...Adeagbo Bamise
This document summarizes different types of electron emission from heated metals, including thermionic emission, field emission, and field-assisted thermionic emission (Schottky emission). Thermionic emission occurs when thermal energy from heating overcomes the work function of a metal, allowing electrons to escape. Field emission occurs at room temperature when a strong electric field lowers the potential barrier for electrons. Schottky emission applies an electric field to enhance thermionic emission and lower the barrier at lower temperatures than normal thermionic emission. These emission types find applications in devices like vacuum tubes.
Superconductivity is the ability of certain materials to conduct electric current with practically zero resistance. This capacity produces interesting and potentially useful effects. For a material to behave as a superconductor, low temperatures are required.
Electron beam machining (EBM) uses a focused beam of electrons to melt and vaporize small amounts of material. It was invented in 1952 and works by accelerating electrons in a vacuum chamber to generate a small, high-energy spot that precisely removes material through melting and vaporization. Key aspects of EBM include its ability to machine very small, high aspect ratio holes and its minimal heat affected zone. However, it requires expensive equipment and vacuum conditions.
Electron beam machining (EBM) involves directing a high-velocity beam of electrons in a vacuum chamber to melt or vaporize material from a workpiece. The electron beam is generated in a gun and focused onto a small spot on the workpiece using magnetic coils. This localized heating allows for precise material removal with minimal heat effects. EBM can machine nearly any material and produces close tolerances, but requires expensive equipment and vacuum systems. Common applications include machining wire drawing dies and manufacturing semiconductor and optical components.
This document discusses different types of electron emission from metal surfaces. There are four principal types: thermionic emission, where heating provides the energy for electrons to overcome the work function; field emission, where a strong electric field pulls electrons from the surface; photoelectric emission, where light energy is transferred to electrons; and secondary emission, where high-velocity electrons striking the surface knock out more electrons. Thermionic emission is described in more detail, including the Richardson-Dushman equation that relates emission current density to temperature and work function, and examples are provided to calculate emission currents and determine metal work functions.
This document discusses electrical conductivity in various materials. It begins by explaining that metals are good conductors due to their large number of free electrons. Semiconductors have lower conductivity than metals due to their lower concentration of free charge carriers. Conductivity in nonmetals like ionic crystals and glasses depends on mobile charges like electrons and ions. The document then discusses how conductivity varies with temperature in nonmetals. It also covers the skin effect in conductors at high frequencies and conductivity considerations in thin metal films. The document concludes by discussing copper interconnects in microelectronics.
The document summarizes electron beam machining (EBM). EBM works by converting the kinetic energy of high-speed electrons into heat energy when they impinge on a workpiece. This heat energy vaporizes material. The process requires vacuum. An electron gun generates electrons that pass through magnetic lenses to focus the beam on the workpiece. Material removal occurs through melting and vaporization. EBM can machine small, complex holes and is used in aerospace and nuclear industries. It offers good finishes but has low material removal rates and high costs.
The document summarizes various cathode processes and decay processes involved in electrical breakdown in gases. It describes four main ways electrons can be emitted from a cathode surface: 1) photoelectric emission through photon bombardment, 2) electron emission through positive ion or excited atom impact, 3) thermionic emission through heating the cathode, and 4) field emission through very strong electric fields lowering the work function. It also discusses two major decay processes: 1) deionization through recombination of positive and negative ions, and 2) deionization through attachment of free electrons to form stable negative ions, especially in electronegative gases.
This document provides lecture notes on engineering physics for an engineering course. It covers topics on atomic structure, electronic configurations, electrical conduction, and electron theories of metals. The document begins with an introduction to atomic structure, including the components of atoms and Madelung's and Hund's rules for electron configuration. It then discusses electrical conduction, defining terms like resistivity, conductivity, and classifications of materials. The remainder of the document covers electron theories of metals, including classical free electron theory, quantum free electron theory, and band theory. Key concepts from each theory are summarized.
Influence of Interface Thermal Resistance on Relaxation Dynamics of Metal-Die...A Behzadmehr
Nanocomposite materials, including noble metal nanoparticles embedded in a dielectric host medium, are interesting because of their optical properties linked to surface plasmon resonance phenomena. For studding of nonlinear optical properties and/or energy transfer process, these materials may be excited by ultrashort pulse laser with a temporal width varying from some femtoseconds to some hundreds of picoseconds. Following of absorption of light energy by metal-dielectric nanocomposite material, metal nanoparticles are heated. Then, the thermal energy is transferred to the host medium through particle-dielectric interface. On the one hand, nonlinear optical properties of such materials depend on their thermal responses to laser pulse, and on the other hand different parameters, such as pulse laser and medium thermodynamic characterizes, govern on the thermal responses of medium to laser pulse. Here, influence of thermal resistance at particle-surrounding medium interface on thermal response of such material under ultrashort pulse laser excitation is investigated. For this, we used three temperature model based on energy exchange between different bodies of medium. The results show that the interface thermal resistance plays a crucial role on nanoparticle cooling dynamics, so that the relaxation characterized time increases by increasing of interface thermal resistance.
This document provides a question bank on the topic of engineering physics for a bachelor's degree program. It includes 70 questions across three sections - short answer, descriptive, and problems. The short answer section contains multiple choice and short response questions testing concepts like band structure of materials, Hall effect, semiconductors, and superconductors. The descriptive section asks students to explain key theories and differentiate between material types. The problems section provides calculations testing conductivity, mobility, drift velocity, and other quantitative applications of the theoretical concepts.
Thermal size effects in contact metal semiconductor structures are investigated. In thin diodes where the sample size is much smaller than the carrier cooling length, the electron temperature at the contact is much higher than the phonon temperature. Energy is transferred to the environment through electronic thermal conductivity. In thick diodes where the sample size is much larger than the cooling length, the electron and phonon temperatures equalize in the volume. At ohmic contacts in both thin and thick diodes, the temperatures equalize with the environment temperature under ideal heat transfer conditions. The temperatures depend on thermal boundary conditions and sample size, with thermal size effects more pronounced in barrier structures.
The document discusses various welding processes and concepts. It provides information on:
1. Resistance welding which uses force and current through electrodes to generate heat and form a weld nugget between metal parts. No danger of electric shock as low voltage is used.
2. Features of resistance welding including no need for flux, clean worksite, easy automation, high production rates, and less heat affected area. Disadvantages include surface preparation needs and expensive equipment.
3. Ultrasonic welding which uses high frequency vibration to melt and fuse thermoplastic materials. It has a fast process, quick drying time, easy automation, and clean precise joints. Limitations are joint size and high tooling
Laser beam machining uses a high-energy, monochromatic light beam to melt and vaporize material on a workpiece's surface. It can be used to cut, drill, weld and mark materials. The document discusses the key components of laser beam and electron beam machining equipment, including the ruby crystal, xenon flash tube, cooling system, and focusing lens. It also explains the processes of how laser beams and electron beams generate and focus intense heat to remove material through melting and vaporization. Advantages include machining any material and producing precise, force-less cuts, while disadvantages include higher costs and lower removal rates compared to other processes.
Laser beam machining uses a laser to remove material from a workpiece. It works by focusing a laser beam onto the material, causing the surface to rapidly heat up and melt or vaporize. The laser beam is generated using a process called "stimulated emission" where electrons in a lasing medium like ruby crystal absorb energy from an external light source and emit photons. These photons bounce between mirrors inside the laser, stimulating more photons and creating an avalanche effect that results in a coherent, high-powered laser beam. During LBM, the focused laser beam is absorbed by the workpiece, rapidly heating it and allowing precise material removal through melting and evaporation.
Iwt unit 5 electron beam welding sushant bhattSRMUBarabanki
Electron beam welding is a fusion welding process that uses a beam of high-velocity electrons to join materials. The process works by accelerating electrons in an electron gun and focusing them via magnetic lenses to produce heat from kinetic energy. This heat is used to fuse materials in a vacuum chamber. Key advantages are the ability to weld dissimilar metals without filler and produce high quality, low defect welds. However, the process requires expensive equipment and high skill levels.
Engineering Physics - II second semester Anna University lecturer notes24x7house
This document provides an overview of conducting materials and classical free electron theory of metals. It discusses key concepts such as conductors, insulators, semiconductors, free electrons, drift velocity, electric field, current density, Fermi level, density of states, and work function. The classical free electron theory proposes that metals consist of free electrons that move randomly and conduct electricity. It can explain several electrical and thermal properties but has limitations and fails to explain newer phenomena, leading to the development of quantum free electron theory.
Superconducting material and Meissner effectMradul Saxena
The project report gives brief explanation of the phenomenon of superconductivity and also give introduction to superconducting materials and their types, properties and their applications.
Plasma arc machining (PAM) uses a plasma torch to cut metals. It was initially developed to cut difficult metals like stainless steel and aluminum. Recent improvements allow it to cut mild steel with improved cut quality compared to earlier plasma cutting. The plasma is generated by heating gas with an electric arc until it ionizes, producing free electrons and ions that conduct electricity. PAM works by melting metal with the high temperature plasma jet and blowing away the molten metal. Key parameters that affect PAM performance include the plasma torch design, the physical setup configuration, and the operating environment.
Principles of Electronics chapter - IIAmit Khowala
This document discusses electron emission from thermionic emitters. It describes the process of thermionic emission where heating a metal provides electrons with enough energy to overcome the surface barrier and be emitted. Common thermionic emitters mentioned are tungsten, thoriated tungsten, and oxide coated cathodes. Thoriated tungsten has a lower work function than pure tungsten, allowing emission at lower temperatures. Oxide coated cathodes operate at even lower temperatures but cannot withstand high voltages. The Richardson-Dushman equation governs thermionic emission current density as a function of temperature and work function.
Current Advanced Research Development of Electric Discharge Machining (EDM): ...sushil Choudhary
Electrical discharge machining (EDM) process is one of the most commonly used nonconventional
precise material removal processes. Electrical discharge machining (EDM) is a process for
shaping hard metals and forming deep complex shaped holes by arc erosion in all kinds of electroconductive
materials. Erosion pulse discharge occurs in a small gap between the work piece and the
electrode. This removes the unwanted material from the parent metal through melting and vaporizing in
presence of dielectric fluid. In recent years, EDM researchers have explored a number of ways to improve
EDM Process parameters such as Electrical parameters, Non-Electrical Parameters, tool Electrode based
parameters & Powder based parameters. This new research shares the same objectives of achieving more
efficient metal removal rate reduction in tool wear and improved surface quality. This paper reviews the
research work carried out from the inception to the development of die-sinking EDM, Water in EDM, dry
EDM, and Powder mixed electric Discharge Machining. Within the past decade. & also briefly describing the Current Research technique Trend in EDM, future EDM research direction.
Electron-beam welding is a fusion welding process where a beam of high-velocity electrons is used to join materials. Electrons are emitted from a heated filament in a vacuum and accelerated to nearly the speed of light using high voltage. The electron beam is focused onto the workpiece, where its kinetic energy is transferred as heat to melt the materials being welded. Electron-beam welding can achieve very narrow, high-quality welds at high speeds and is often used for joining refractory or dissimilar metals where other welding methods may not be suitable.
Electron beam machining (EBM) uses a focused beam of electrons to melt and vaporize small amounts of material. It was invented in 1952 and works by accelerating electrons in a vacuum chamber to generate a small, high-energy spot that precisely removes material through melting and vaporization. Key aspects of EBM include its ability to machine very small, high aspect ratio holes and its minimal heat affected zone. However, it requires expensive equipment and vacuum conditions.
Electron beam machining (EBM) involves directing a high-velocity beam of electrons in a vacuum chamber to melt or vaporize material from a workpiece. The electron beam is generated in a gun and focused onto a small spot on the workpiece using magnetic coils. This localized heating allows for precise material removal with minimal heat effects. EBM can machine nearly any material and produces close tolerances, but requires expensive equipment and vacuum systems. Common applications include machining wire drawing dies and manufacturing semiconductor and optical components.
This document discusses different types of electron emission from metal surfaces. There are four principal types: thermionic emission, where heating provides the energy for electrons to overcome the work function; field emission, where a strong electric field pulls electrons from the surface; photoelectric emission, where light energy is transferred to electrons; and secondary emission, where high-velocity electrons striking the surface knock out more electrons. Thermionic emission is described in more detail, including the Richardson-Dushman equation that relates emission current density to temperature and work function, and examples are provided to calculate emission currents and determine metal work functions.
This document discusses electrical conductivity in various materials. It begins by explaining that metals are good conductors due to their large number of free electrons. Semiconductors have lower conductivity than metals due to their lower concentration of free charge carriers. Conductivity in nonmetals like ionic crystals and glasses depends on mobile charges like electrons and ions. The document then discusses how conductivity varies with temperature in nonmetals. It also covers the skin effect in conductors at high frequencies and conductivity considerations in thin metal films. The document concludes by discussing copper interconnects in microelectronics.
The document summarizes electron beam machining (EBM). EBM works by converting the kinetic energy of high-speed electrons into heat energy when they impinge on a workpiece. This heat energy vaporizes material. The process requires vacuum. An electron gun generates electrons that pass through magnetic lenses to focus the beam on the workpiece. Material removal occurs through melting and vaporization. EBM can machine small, complex holes and is used in aerospace and nuclear industries. It offers good finishes but has low material removal rates and high costs.
The document summarizes various cathode processes and decay processes involved in electrical breakdown in gases. It describes four main ways electrons can be emitted from a cathode surface: 1) photoelectric emission through photon bombardment, 2) electron emission through positive ion or excited atom impact, 3) thermionic emission through heating the cathode, and 4) field emission through very strong electric fields lowering the work function. It also discusses two major decay processes: 1) deionization through recombination of positive and negative ions, and 2) deionization through attachment of free electrons to form stable negative ions, especially in electronegative gases.
This document provides lecture notes on engineering physics for an engineering course. It covers topics on atomic structure, electronic configurations, electrical conduction, and electron theories of metals. The document begins with an introduction to atomic structure, including the components of atoms and Madelung's and Hund's rules for electron configuration. It then discusses electrical conduction, defining terms like resistivity, conductivity, and classifications of materials. The remainder of the document covers electron theories of metals, including classical free electron theory, quantum free electron theory, and band theory. Key concepts from each theory are summarized.
Influence of Interface Thermal Resistance on Relaxation Dynamics of Metal-Die...A Behzadmehr
Nanocomposite materials, including noble metal nanoparticles embedded in a dielectric host medium, are interesting because of their optical properties linked to surface plasmon resonance phenomena. For studding of nonlinear optical properties and/or energy transfer process, these materials may be excited by ultrashort pulse laser with a temporal width varying from some femtoseconds to some hundreds of picoseconds. Following of absorption of light energy by metal-dielectric nanocomposite material, metal nanoparticles are heated. Then, the thermal energy is transferred to the host medium through particle-dielectric interface. On the one hand, nonlinear optical properties of such materials depend on their thermal responses to laser pulse, and on the other hand different parameters, such as pulse laser and medium thermodynamic characterizes, govern on the thermal responses of medium to laser pulse. Here, influence of thermal resistance at particle-surrounding medium interface on thermal response of such material under ultrashort pulse laser excitation is investigated. For this, we used three temperature model based on energy exchange between different bodies of medium. The results show that the interface thermal resistance plays a crucial role on nanoparticle cooling dynamics, so that the relaxation characterized time increases by increasing of interface thermal resistance.
This document provides a question bank on the topic of engineering physics for a bachelor's degree program. It includes 70 questions across three sections - short answer, descriptive, and problems. The short answer section contains multiple choice and short response questions testing concepts like band structure of materials, Hall effect, semiconductors, and superconductors. The descriptive section asks students to explain key theories and differentiate between material types. The problems section provides calculations testing conductivity, mobility, drift velocity, and other quantitative applications of the theoretical concepts.
Thermal size effects in contact metal semiconductor structures are investigated. In thin diodes where the sample size is much smaller than the carrier cooling length, the electron temperature at the contact is much higher than the phonon temperature. Energy is transferred to the environment through electronic thermal conductivity. In thick diodes where the sample size is much larger than the cooling length, the electron and phonon temperatures equalize in the volume. At ohmic contacts in both thin and thick diodes, the temperatures equalize with the environment temperature under ideal heat transfer conditions. The temperatures depend on thermal boundary conditions and sample size, with thermal size effects more pronounced in barrier structures.
The document discusses various welding processes and concepts. It provides information on:
1. Resistance welding which uses force and current through electrodes to generate heat and form a weld nugget between metal parts. No danger of electric shock as low voltage is used.
2. Features of resistance welding including no need for flux, clean worksite, easy automation, high production rates, and less heat affected area. Disadvantages include surface preparation needs and expensive equipment.
3. Ultrasonic welding which uses high frequency vibration to melt and fuse thermoplastic materials. It has a fast process, quick drying time, easy automation, and clean precise joints. Limitations are joint size and high tooling
Laser beam machining uses a high-energy, monochromatic light beam to melt and vaporize material on a workpiece's surface. It can be used to cut, drill, weld and mark materials. The document discusses the key components of laser beam and electron beam machining equipment, including the ruby crystal, xenon flash tube, cooling system, and focusing lens. It also explains the processes of how laser beams and electron beams generate and focus intense heat to remove material through melting and vaporization. Advantages include machining any material and producing precise, force-less cuts, while disadvantages include higher costs and lower removal rates compared to other processes.
Laser beam machining uses a laser to remove material from a workpiece. It works by focusing a laser beam onto the material, causing the surface to rapidly heat up and melt or vaporize. The laser beam is generated using a process called "stimulated emission" where electrons in a lasing medium like ruby crystal absorb energy from an external light source and emit photons. These photons bounce between mirrors inside the laser, stimulating more photons and creating an avalanche effect that results in a coherent, high-powered laser beam. During LBM, the focused laser beam is absorbed by the workpiece, rapidly heating it and allowing precise material removal through melting and evaporation.
Iwt unit 5 electron beam welding sushant bhattSRMUBarabanki
Electron beam welding is a fusion welding process that uses a beam of high-velocity electrons to join materials. The process works by accelerating electrons in an electron gun and focusing them via magnetic lenses to produce heat from kinetic energy. This heat is used to fuse materials in a vacuum chamber. Key advantages are the ability to weld dissimilar metals without filler and produce high quality, low defect welds. However, the process requires expensive equipment and high skill levels.
Engineering Physics - II second semester Anna University lecturer notes24x7house
This document provides an overview of conducting materials and classical free electron theory of metals. It discusses key concepts such as conductors, insulators, semiconductors, free electrons, drift velocity, electric field, current density, Fermi level, density of states, and work function. The classical free electron theory proposes that metals consist of free electrons that move randomly and conduct electricity. It can explain several electrical and thermal properties but has limitations and fails to explain newer phenomena, leading to the development of quantum free electron theory.
Superconducting material and Meissner effectMradul Saxena
The project report gives brief explanation of the phenomenon of superconductivity and also give introduction to superconducting materials and their types, properties and their applications.
Plasma arc machining (PAM) uses a plasma torch to cut metals. It was initially developed to cut difficult metals like stainless steel and aluminum. Recent improvements allow it to cut mild steel with improved cut quality compared to earlier plasma cutting. The plasma is generated by heating gas with an electric arc until it ionizes, producing free electrons and ions that conduct electricity. PAM works by melting metal with the high temperature plasma jet and blowing away the molten metal. Key parameters that affect PAM performance include the plasma torch design, the physical setup configuration, and the operating environment.
Principles of Electronics chapter - IIAmit Khowala
This document discusses electron emission from thermionic emitters. It describes the process of thermionic emission where heating a metal provides electrons with enough energy to overcome the surface barrier and be emitted. Common thermionic emitters mentioned are tungsten, thoriated tungsten, and oxide coated cathodes. Thoriated tungsten has a lower work function than pure tungsten, allowing emission at lower temperatures. Oxide coated cathodes operate at even lower temperatures but cannot withstand high voltages. The Richardson-Dushman equation governs thermionic emission current density as a function of temperature and work function.
Current Advanced Research Development of Electric Discharge Machining (EDM): ...sushil Choudhary
Electrical discharge machining (EDM) process is one of the most commonly used nonconventional
precise material removal processes. Electrical discharge machining (EDM) is a process for
shaping hard metals and forming deep complex shaped holes by arc erosion in all kinds of electroconductive
materials. Erosion pulse discharge occurs in a small gap between the work piece and the
electrode. This removes the unwanted material from the parent metal through melting and vaporizing in
presence of dielectric fluid. In recent years, EDM researchers have explored a number of ways to improve
EDM Process parameters such as Electrical parameters, Non-Electrical Parameters, tool Electrode based
parameters & Powder based parameters. This new research shares the same objectives of achieving more
efficient metal removal rate reduction in tool wear and improved surface quality. This paper reviews the
research work carried out from the inception to the development of die-sinking EDM, Water in EDM, dry
EDM, and Powder mixed electric Discharge Machining. Within the past decade. & also briefly describing the Current Research technique Trend in EDM, future EDM research direction.
Electron-beam welding is a fusion welding process where a beam of high-velocity electrons is used to join materials. Electrons are emitted from a heated filament in a vacuum and accelerated to nearly the speed of light using high voltage. The electron beam is focused onto the workpiece, where its kinetic energy is transferred as heat to melt the materials being welded. Electron-beam welding can achieve very narrow, high-quality welds at high speeds and is often used for joining refractory or dissimilar metals where other welding methods may not be suitable.
One of the welding processes that used in Engineering field is the electron beam welding. There are several types of welding processes similar to this, but electron beam welding has its unique features.
Thanks for the colleagues who give this slides to publish.
Electron beam machining uses a focused beam of high-velocity electrons to melt and vaporize material. It works similarly to laser beam machining but uses electrons instead of light. The process takes place inside a vacuum chamber to prevent electron scattering. Electrons are generated by a heated cathode and accelerated toward the workpiece, where their kinetic energy transforms to thermal energy on impact. This localized heating allows for precise machining with no tool wear. Applications include drilling small, high-aspect-ratio holes for devices like aircraft engines.
This document describes simulations done using COMSOL Multiphysics to design an optimal extraction tube for an electron beam emitted from a plasma focus device. The simulations aimed to determine a material that would shield the electron beam from electromagnetic forces within the device while maintaining electrical safety. Simulation results showed that a steel tube provided adequate shielding, but steel is not electrically safe. A design using a steel tube with an outer Delrin coating was found to both shield the electron beam and maintain electrical safety, making it the optimum extraction tube design.
This document provides an overview of thermoelectric and thermionic conversions. It begins with an introduction to thermoelectric, magnetohydrodynamic, and thermionic systems that directly convert heat into electricity without moving parts. It then describes the Seebeck, Peltier, and Thomson effects that form the basis of thermoelectric conversion. Diagrams illustrate the working principles of these effects. Requirements for suitable thermoelectric materials are outlined. Advantages of thermoelectric systems include having no moving parts and potential applications in remote areas and waste heat recovery, while disadvantages include low thermal efficiency. Examples of applications are in nuclear reactors, steam power plants, and recovering waste heat from engines.
Electrical Discharge Machining (EDM) is a manufacturing process that uses electrical sparks to remove material from a conductive workpiece. In the EDM process, a tool electrode is moved close to the workpiece and an electric spark is generated via a dielectric fluid between them, vaporizing a small amount of material. This process is repeated many times to gradually shape the workpiece. EDM can machine very hard materials and complex shapes without causing mechanical stress to the workpiece. Common applications include drilling micro holes, cutting intricate profiles, and machining hardened steel dies and molds.
Study Some Parameters of Electrical Discharge in N2 and CO2 Without and With ...IOSRJECE
:We study the breakdown voltage under low pressure for N2, CO2 gases of with a magnetic field to the electrode of iron and aluminum with diameter (8.8cm) cm and distance separation between them is (3cm). by using Passion curve, we measur less effort collapsed, and we notice that less effort is linked to the collapse of a function held cities and when the magnetic field will be reduced to shed breakdown voltage. Since the breakdown voltage for CO2 is greater than breakdown voltage N2. Through curved Passion was calculated (훾) and when to shed the magnetic field will increase in value
The document discusses the principles and physics of welding. It covers topics such as fusion welding processes, characteristics of heat sources like welding arcs, arc structures, and potential drop characteristics. The key points are:
1) In fusion welding, material around the joint is melted to join two parts together. Important factors include the heat source, arc characteristics, filler material deposition, and heat flow.
2) A welding arc is a sustained electrical discharge through an ionized gas that produces heat. It is maintained by thermionic emission and ionization between the electrodes.
3) The voltage drop across a welding arc depends on factors like the electrode material, spacing and current. There is an optimal arc length that produces maximum power
Electrical Discharge Machining (EDM) is a manufacturing process where electrical discharges are used to erode material from a workpiece to achieve a desired shape. In EDM, a potential difference is applied between an electrode tool and the workpiece, which are separated by a dielectric liquid. This causes electric sparks to form that melt and vaporize small amounts of material from both the tool and workpiece. Kerosene or deionized water is typically used as the dielectric liquid to facilitate flushing of debris and prevent oxidation during the process.
Electrical Discharge Machining (EDM) is a manufacturing process where electrical discharges are used to erode material from a workpiece to achieve a desired shape. In EDM, a series of electrical sparks are generated between two electrodes submerged in a dielectric liquid and subject to an electric voltage. This causes material to be removed from both electrodes through localized melting and vaporization due to the extreme heat of the sparks. EDM can be used to machine hard metals and intricate shapes that would be difficult to machine through conventional methods.
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Electron Beam Machining (Modern ManufacturingProcess)
1. 19
Chapter 3
ELECTRON BEAM MACHINING (EBM)
3.1 INTRODUCTION
Electron beams are now used in many industrial types of equipment. They have many
special characteristics which make them most suited for specific applications. The most important
of These characteristics is the high resolution and the long depth of field that is obtained because
of the short wavelength of high energy electrons. Other features of the beams include their extra
ordinary energy (e.g. power densities of 106
kw/cm2
have been achieved) ability to catalyze many
chemical reactions, controllability, and compatibility with high vacuum. Electron beam
machining (EBM) can be classified into two types. In one, which can be termed ‘thermal type’,
the beam is used to heat the material up to the point where it is selectively vaporized. The other,
called ‘non-thermal type’ utilizes the beam to cause a chemical reaction. The ability of electron
beams to cause drastic thermal effects has been known since a long time. In the late 1930s it was
used for drilling the apertures of electron microscopes. In 1950, Steigerwald and his colleagues at
Carl Zeiss A.G. (Germany) developed an electron beam milling machine. E.B. Bas, in 1960,
made fine holes in ruby crystals. In attempting to drill holes in diamond, Steigerwald found that
the electron beam could raise the temperature of diamond to as much as 3000o
C even though
diamond tends to disintegrate into graphite at 2000o
C. by introducing oxygen into the vacuum
system, CO or CO2 could be formed at 300o
C, thus burning away the material which was not
possible to vaporize. The ability of low energy electrons to bring about a surface chemical
reaction was first observed and studied by P.H. Carr. Significant research in both thermal and
non-thermal EBM has since then been done by many researches.
As a metals-processing tool, the electron beam is used mainly for welding, to some extent
for surface hardening, and occasionally for cutting (mainly drilling). Electron beam
machining (EBM) is a thermal process that uses a beam of high-energy electrons focused
on the workpiece to melt and vaporize metal. This process shown in Figure 28-26 is
performed in a vacuum chamber (10-5 torr), The electron beam is produced in the
2. 20
electron gun (also under vaccum) by thermionic emission. In its simplest form, a filament
(tungsten) is heated to temperatures in excess of2ooo°C where a stream (beam) of
electrons (more than 1 billion per second) is emitted from the tip of the filament.
Electrostatic optics are used to focus and direct the beam. The desired beam path can be
programmed with a computer to produce any desired pattern in the workpiece. The
diameter of the beam is on the order of 0.012 to 0.025 mm, and holes or narrow slits with
depth-to-width ratios of 100:1 can be "machined" with great precision in any material.
The interaction of the beam with the surface produces dangerous X-rays; therefore,
electromagnetic shielding of the process is necessary. The layer of recast material and the
depth of the heat damage are very small. For micromachining applications, MRRs can
exceed that of EDM or ECM, Typical tolerances are about 10% of the hole diameter or
slot width. These machines require high voltages (50 to 200 kV) to accelerate the
electrons to speeds of 0,5 to 0.8 the speed of light and should be operated by fully trained
personnel.
A typical electron beam installation for drilling is shown in fig. 1. It consists of five basic units:
1) electron gun which generates and directs a controlled beam of electrons of high energy density
on the work material to change it chemically and physically,
2) Vacuum chamber and a high vacuum pump system,
3) Movable table with in the chamber for mounting the work piece,
4) An electronic system which controls the size and movement of beam and
5) A monitoring instrument.
3.2 GENERATION AND CONTROL OF ELECTRON BEAM
The electron beam is a stream of negatively charged particles which are generated,
accelerated, and to some extent, focused inside a device called an ‘electron gun’. The essential
constituents of an electron gun are:
a) A cathode, which serves as the source of electrons. It may be a current carrying, self
heating filament, or a solid block indirectly heated by radiation from a filament.
b) A grid cup, which is negatively biased with respect to filament.
3. 21
c) An anode which is kept at ground potential, and through which the high velocity
electrons pass.
The beam of electrons is emitted from the tip of the hot cathode. It is accelerated towards the
anode by the high potential applied between the anode and cathode. It passes through the anode at
a speed up to two-third of the velocity of light. The flow of electrons is controlled by the negative
bias applied to the grid cup.
A magnetic deflection coil fitted below the electron gun is used to make the electron beam
circular in cross-section and deflect it anywhere. The beam is generated in a high vacuum for two
reasons:
1) The emitter would rapidly oxidize when incandescent, at anything like atmospheric pressure,
and
2) The electrons would lose energy by collision with air molecules. The electron emitter with its
focusing coils is used at a vacuum of 10-4
or 10-5
torr.
A power density of as high a magnitude as a billion Watts/square cm can be attained in the
beam. This is sufficient to immediately fuse and vaporize any material n which it falls. Thus, in a
thermal type EBM, cutting is, in fact, a precisely controlled vaporization process.
The rate R at which the material is vaporized can be calculated by
R == η P/W (3.1)
Where η is the cutting efficiency, P is the power (J/s), and W is the specific energy required to
vaporize the material (J/cm3
) given as
W == Cp (Tm - 20) + Cp (Tb - Tm) + Hf + Hv
== Cp (Tb - 20) + Hf + Hv (3.2)
in which Cp is the specific heat, Tm is the melting temperature, Tb is the boiling temperature, Hf is
the heat of fusion and Hv is the heat of vaporization. The values of these terms for some metals
are given in table. The cutting efficiency is normally very low (2-20 per cent) and depends on the
cross-sectional area of the cut made.
4. 22
3.3 PHYSICAL AND THERMAL PROPERTIES OF METALS
Property
Metal
Melting
Temp.
Tm
o
C
Boiling
Temp.
Tb
o
C
Specific
Heat
C
cal/g/ o
C
Heat of
Fusion
Ht
cal/g
Heat of
Vaporization
Hv
cal/g
Specific
energy of
vaporization
W/ cm3
Iron 1536 3000 0.11 65 1514.8 06.3 * 104
Molybdenum 2610 5560 0.061 70 1340 07.5 * 104
Tungsten 3410 5930 0.032 44 1006 10.0 * 104
Titanium 1668 3260 0.126 36.7 222.3 05.0 * 104
3.4 THEORY OF ELECTRON BEAM MACHINING
3.4.1Thermal Type
The theory of thermal type of EBM has not yet been completely developed due to many
reasons. First, since the process has shown many practical results, no pressure has been put on the
researchers in the field to develop extensive theories or to make difficult analyses. Second,
although the individual physical processes involved are simple, their number, non-linearity and
complicated geometry, all combine to make a theoretical analysis of the process difficult. Third
the small dimensions, short time intervals, and lack of thermodynamic equilibrium make it
difficult to get the required experimental data for correlation with any theory.
3.4.1.1Forces in Machining
Since the temperature in the vicinity of the electron beam cause the material to be in
molten state, the material is acted upon by forces of surface tension, gravity, electron beam
pressure and the reaction force of the departing vaporized material. In machining non-conducting
materials, electrostatic forces may also be present. A study of these forces (Fig. 2) will be made
and the relationships established to find their magnitudes.
5. 23
(a) Electron Pressure: The pressure due to electron bombardment can be estimated from the
momentum loss suffered by the electron beam as it impinges upon the work surface.
fe= meve i/e
Where fe is the electron pressure (N/m2
), me the electronic mass, Ve the velocity (m/s),i is the
current density (amp/m2
) and e the electron charge. The velocity Ve can be calculated from the
accelerating voltage U as
Ve= (2 e U/me) ½
(3.3)
Thus fe= (2 me U/e)½
i (3.4)
The total force due to electron bombardment is
fe = Л r2
fe
= Л r2
(2 me U/e) ½
i
= (2 me U I2
/e)½
Where r is the radius of the hole and I is the total current.
(b) Back Pressure of Evaporating Atoms: The effect of momentum of the thermally
evaporating material can be studied by considering the conservation of momentum.
pa == mo va (3.5)
Where pa is the back pressure of evaporating atoms, mo the mass of material removed per unit area
of surface per unit time, va the atomic velocity given as
va == (2 k T/mp M)½
(3.6)
Because the average energy of particles evaporating from a surface is 2 kT, of which kT will be
in the direction normal to the surface. In the above equation, k is Boltzmann constant, T the
temperature, mp the proton mass and M the atomic weight. The total force exerted by the back
pressure is
6. 24
Fbp == m1 va (3.7)
Where m1 is the mass of material removed per unit time, provided the surface over which mo is
integrated to get m1 is plane.
(a) Surface Tension: The total force of surface tension, tending to close the cavity formed,
equals tension force (N/m length) times the circumference of the cavity, that is
Fs == fs .2 Л r (3.8)
Where r is the radius of the cavity of the hole produced. A force equal in magnitude will at the
same time resist the formation of a liquid lip at the top of the hole.
Surface tension has not been studied till now for liquid metals at such high temperatures as are
involved in EBM. However, the values are available for many metals near their melting points.
For gold, silver, copper etc, the values are in the range of 500-2000 dynes/cm.
(b) Hydrostatic Pressure of Molten Metal :The hydrostatic pressure due to the molten
surface on the side of the cavity being generated is
Fh == ρ g h (3.9)
and the total force exerted on the bottom of the hole towards the top is
Fh == ρ g h Л r2
(3.10)
Where ρ is the density of the molten metal (kg/m3
) g the acceleration due to gravity, h the depth
of the cavity, and r the radius of the cavity formed.
In the calculation with actual data, the hydrostatic force is normally very small and can be
neglected. The electron pressure force is the largest of all these forces but the other two forces are
also significant. If the surface tension force is larger than the atomic reaction force, molten metal
would tend to flow from the walls into the bottom of the wall, where it would be evaporated by
the beam; otherwise, if the reaction force is larger than the surface tension force (in case of big
holes), molten material would be pushed out of the hole.
7. 25
3.4.2 Non-thermal Type
` Christly, who has made an excellent study in this field, has put forward a phenomenological
theory which predicts the rate of film growth for the polymerization of organic films by electron
bombardment. His theory is summarized here.
Consider a surface on which a film is being deposited as a result of the polymerization of the
molecules arriving at the rate no per unit area per unit time by the action of electrons arriving at
rate ne per unit area per unit time. Further, let a denote the cross-section for reaction, τ the mean
time of stay of an interacted molecule on the surface. It can be assumed that a reacted molecule
remains on the surface permanently. Also, it is assumed that the initial surface is made up of
already polymerized molecules so that no anomalous surface effect takes place for the first layer,
then
dN1/dt == a no No (3.11)
and
dNo/dt == no - No/ τ – dN1/dt (3.12)
By solving these equations for No
No == no/(a ne+ 1/ τ){1 – K [exp – (a no + 1/ τ) t ]} (3.13)
Where K is a dimensionless constant and depends upon the initial surface coverage. K = 0
corresponds to the steady state solution; K≤0 or K>0 to an initial concentration greater or less,
respectively than the steady state condition. The following cases arise.
Case 1: This case corresponds to the condition when surface density of unrelated molecules No is
less than that of one monolayer. This mans that No<1/ao, where ao is the surface area of one
molecule. Thus,
no < (a/ao) ne + 1/ao τ (3.14)
Also from Eqs. 1.12 & 1.14
dN1/dt == no/ (1+1/aneτ) {1 – K [exp – (a no + 1/ τ) t ]} (3.15)
And on integration
8. 26
N1 == no/ (1+1/aneτ) [t + K/ (a ne+ 1/ τ) exp – (a ne + 1/ τ) t] (3.16)
It is assumed that N1 = 0 at t = 0. For K=1 corresponding to the initial coverage and
t < (a ne + 1/ τ), dN1/dt is proportional to t, and N1 is proportional to t2
. In steady state conditions,
the rate of film growth can be written as
Rt == dN1/dt. Vm
Where Vm is the volume of one molecule. Thus
RT == no Vm/ (1+1/ aneτ) (3.17)
Case 2: This is the case when the arrival rate of molecules is sufficient to maintain a monolayer
on the surface at all times. The case is restricted to the situation No = 1/ao, that is, more than one
monolayer is not possible because of a significant lowering of the binding energy of molecules in
the second layer. The condition can be visualized by considering that T approaches zero for the
second layer, thus
no ≥ (a/ao) ne + 1/ aoτ
No == 1/ao
And
Rt == (a/ao ) ne.Vm
Case 3: This case corresponds to the condition when all the arriving molecules stick to the
surface regardless of the surface conditions, that is, τ approaches infinity and a thick film of
unreacted material is formed. Equations (1.14), (1.15), and (1.17) transform to
No = no/a ne + K’ exp (-a ne t)
dN1/dt = no + a ne K’ exp (-a ne t)
N1 =no t – K’ [exp (-a ne t) -1]
9. 27
Where K’ is another dimensionless constant and it has been assumed that the probability of a
given molecule reacting is not dependent upon its depth below the surface. This means that the
total film is quite thin and is transparent to the bombarding electrons. The rate of deposition of
reacted molecules under steady state conditions is given by
Rt == no Vm
Case 4: This case refers to the situation when the unreacted film is completely deposited before
the electron bombardment. In this case we will have x = 0 and
No == K’ exp (-a ne t)
dN1/dt == a ne K’ exp (-a ne t)
N1 == K’ [1- exp (-a ne t)]
The deposition rate calculation in this case has no meaning. It can be seen, however, that to form
a film K’ thick, containing less than 1 percent of unreacted molecules, bombardment is required
for a time of 5/a ne because e-5
== 1/150
Christly has also experimentally studied the formation of polymerized organic films. He has
shown that the product a ne depends exponentially upon the reciprocal temperature dependence of
τ. Ennos also studied this phenomenon. He observed that reaction cross-section remains almost
constant in the electron energy range of 2-74 k eV.
3.5 PROCESS CAPABILITIES AND LIMITATIONS
The main uses of this process today include the cutting and welding of materials. The chief
advantage of cutting from the engineer’s point of view is that the process is not dependent on the
work material properties. The materials which can be cut include aluminum, beryllium, cemented
carbides, ceramics, copper alloys, glass, alloy steels, tantalum, titanium, tungsten, and zirconium.
The process works as effectively on extremely hard and tough alloys as on soft nonferrous metals.
Though the process does not possess the advantage of high material removal rates, it is claimed
that it can be use to cut very accurate slots and shapes in all kind of materials. The electron beam
machining has a promising future in the cutting of delicate and consistent shapes which are
10. 28
needed in certain electronic assemblies. In such applications, it can be a formidable competitor of
ultrasonic and chemical machining processes which are currently used for this type of work.
3.6 COMPARISION OF THERMAL AND NON-THERMAL PROCESSES
The two processes are not as much in competition as the initially may appear to be. For
drilling holes and making slots or other deep constructions, the thermal processes are better
because the high energy density required necessities working on a small area only. Due to the fact
that electrons give up most of their energy at approximately 5 to 15 microns below the surface,
the work surface can not be vaporized without melting the material in this region, and therefore,
the use of this process for machining the top layer of a thick laminar structure is not
recommended. The thermal has reached the technical stage where it can mind immediate
industrial use but the non-thermal process has not. The non-thermal process is particularly useful
for machining large areas of thin films. Greater depth can not be attained due to very low reaction
rates but resolution is comparatively much superior. The material removal rate per unit area in
this process is only 10-20 per cent of that achievable in the thermal process.
SUMMERY OF EBM CHARACTERSTICS
Mechanics of material removal Melting, vaporization Medium Vacuum Tool Beam of
electrons moving at very high velocity
Maximum material removal rate 10 mm3
/min
Specific power consumption 450 W/mm3
-min
(typical)
Critical parameters accelerating voltage, beam current, beam diameter, work speed,
melting temperature
Materials application All materials
Shape application Drilling fine holes, cutting contours in sheets, cutting narrow
slots
Limitations Very high specific energy consumption, necessity of vacuum,
expensive machine