# Current Affairs Railways

#### Materials Science

Materials Science
• Materials science is an interdisciplinary field which deals with the discovery and design of new materials. Though it is a relatively new scientific field that involves studying materials through the materials paradigm its intellectual origins reach back to the emerging fields of chemistry, mineralogy and engineering during the Enlightenment.
• It incorporates elements of physics and chemistry, and is at the forefront of Nano science and nanotechnology research. In recent years, materials science has become more widely known as a specific field of science and engineering.
• It is an important part of forensic engineering (the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property) and failure analysis, the latter being the key to understanding, for example, the cause of various aviation accidents.
• Many of the most pressing scientific problems that are faced today are due to the limitations of the materials that are available and, as a result, breakthroughs in this field are likely to have a significant impact on the future of technology.
• The material of choice of a given era is often a defining point. Phrases such as Stone Age, Bronze Age, Iron Age, and Steel Age are great examples.
• Originally deriving from the manufacture of ceramics and its putative derivative metallurgy, materials science is one of the oldest forms of engineering and applied science.
• Modern materials science evolved directly from metallurgy, which itself evolved from mining and likely) ceramics and the use of fire. A major breakthrough in the understanding of materials occurred in the late 19th century, when the American scientist Josiah Willard Gibbs demonstrated that the thermodynamic properties related to atomic structure in various phases are related to the physical properties of a material.
• Important elements of modem materials science are a product of the space race: the understanding and engineering of the metallic alloys, and silica and carbon materials, used in the construction of space vehicles enabling the exploration of space.
• Materials science has driven, and been driven by, the development of revolutionary technologies such as plastics, semiconductors, and biomaterials.
• A material is defined as a substance (most often a solid, but other condensed phases can be included) that is intended to be used for certain applications. There are a myriad of materials around us-they can be found in anything from buildings to spacecraft. Materials can generally be divided into two classes: crystalline and non-crystalline.
• The traditional examples of materials are metals, ceramics and polymers. [3] New and advanced materials that are being developed include semiconductors, nanomaterial's, biomaterials, etc.
• The basis of materials science involves studying the structure of materials, and relating them to their properties. Once a materials scientist knows about this structure-property correlation, he/she can then go on to study the relative performance of a material in a certain application.
• The major determinants of the structure of a material and thus of its properties are its constituent chemical elements and more...

#### Metal Forming

Metal Forming
• Metal forming is a general term for a large group that includes a wide variety of manufacturing processes. Metal forming processes are characteristic in that the metal being processed is plastically deformed to shape it into a desired geometry.
• In order to plastically deform a metal, a force must be applied that will exceed the yield strength of the material. When low amounts of stress are applied to a metal it will change its geometry slightly, in correspondence to the force that is exerted. Basically it will compress, stretch, and/or bend a small amount.
• The magnitude of the amount will be directly proportional to the*force applied. Also the material will return to its original geometry once the force is released. Think of stretching a rubber band, then releasing it, and having it go back to its original shape. This is called elastic deformation.
• Once the stress on a metal increases past a certain point, it no longer deforms elastically, but starts to undergo plastic deformation. In plastic deformation, the geometric change in the material is no longer directly proportional to stress and geometric changes remain After the stress is released; meaning that the material does not recover its shape.
• The actual level of stress applied to a metal where elastic deformation turns to plastic deformation is called the proportional limit, and is often difficult to determine exactly. The .002 offset convention is usually used to determine the yield point, which is taken for practical purposes as the stress level where plastic deformation, (yielding), begins to occur
• Forming, or metal forming, is the metalworking process of fashioning metal parts and objects through mechanical deformation; the work-piece is reshaped without adding or removing material, and its mass remains unchanged.
• Forming operates on the materials science principle of plastic deformation, where the physical shape of a material is permanently deformed.
• Metal forming tends to have more uniform characteristics across its sub-processes than its contemporary processes, cutting and joining.
• On the industrial scale, forming is characterized by:
$-$Very high required loads and stresses, between 50 and $2500\,\text{N/m}{{\text{m}}^{\text{2}}}$ (7-360 ksi) $-$Large, heavy, and expensive machinery in order to accommodate such high stresses and loads        $-$Production runs with many parts, to maximize the economy of production and compensate for the expense of the machine tools
• Forming processes tend to be typified by differences effective stresses. These categories and descriptions are highly simplified, since the stresses operating at a local level in any given process are very complex and may involve many varieties of stresses operating simultaneously, or it may involve stresses which change over the course of the operation.
• Compressive forming involves those processes where the primary means of plastic deformation is uni-or multiaxial compressive loading.
$-$Rolling, where the material is passed through a pair of rollers                                   $-$Extrusion, where the material is pushed through an orifice                              $-$Die forming, where the material is stamped by a press around or onto a die                    $-$Forging, more...

#### Metal Casting

Metal Casting
• In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify.
• The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods.
• Casting processes have been known for thousands of years, and widely used for sculpture, especially in bronze, jewelry in precious metals, and weapons and tools. Traditional techniques include lost-wax casting, plaster mold casting and sand casting.
• The modem casting process is subdivided into two main categories: expendable and non-expendable casting.
• It is further broken down by the mold material, such as sand or metal, and pouring method, such as gravity, vacuum, or low pressure.
• Sand casting is one of the most popular and simplest types of casting, and has been used for centuries. Sand casting allows for smaller batches than permanent mold casting and at a very reasonable cost.
• Not only does this method allow manufacturers to create products at a low cost, but there are other benefits to sand casting, such as very small-size operations. From castings that fit in the palm of your hand to train beds it can all be done with sand casting.
• Sand casting also allows most metals to be east depending on the type of sand used for the molds.
• Sand casting requires a lead time of days, or even weeks sometimes, for production at high output rates and is unsurpassed for large-part production. Green (moist) sand has almost no part weight limit, whereas dry sand has a practical part mass limit of $2,300-2,700\,kg$ $(5,100-6,000\,lb).$
• Minimum part weight ranges from $0.075-0.1\,kg\,(0.17-0.22\,lb).$ the sand is bonded together using clays, chemical binders, or polymerized oils (such as motor oil). Sand can be recycled many times in most operations and requires little maintenance.
• Plaster casting is similar to sand casting except that plaster of parts is substituted for sand as a mold material. Generally, the form takes less than a week to prepare, after which a production rate of $1-10$ units/hr-mold is achieved, with items as massive as 45 kg (99 Ib) and as small as 30 g (1 oz) with very good surface finish and close tolerances.
• Plaster casting is an inexpensive alternative to other molding processes for complex parts due to the low cost of the plaster and its ability to produce near net shape castings. The biggest disadvantage is that it can only be used with low melting point non-ferrous materials, such as aluminium, copper, magnesium, and zinc.
• Shell molding is similar to sand casting, but the molding cavity is formed by a hardened "shell" of sand instead of a flask filled with sand. The sand used is finer than sand casting sand and is mixed with a resin so that it can be heated by the more...

#### Metal Cutting

Metal Cutting
• Metalworking is the process of working with metals to create individual parts, assemblies, or large-scale structures. The term covers a wide range of work from large ships and bridges to precise engine parts and delicate jewelry. It therefore includes a correspondingly wide range of skills, processes, and tools.
• Metalworking is a science, art, hobby, industry and trade. Its historical roots span cultures, civilizations, and millennia. Metalworking has evolved from the discovery of smelting various ores, producing malleable and ductile metal useful for tools and adornments.
• Modem metalworking processes, though diverse and specialized, can be categorized as forming, cutting, or joining processes. Today's machine shop includes a number of machine tools capable of creating a precise, useful work piece.
• The oldest archaeological evidence of copper mining and working was the discovery of a copper pendant in northern Iraq from 8,700 BC. The earliest substantiated and dated evidence of metalworking in North America was the processing of copper.
• Copper was hammered until brittle then heated so it could be worked some more. This technology is dated to about 4000-5000 BC. The oldest gold artifacts in the world come from the Bulgarian Varna Necropolis and date from 4450 BC.
• Not all metal required fire to obtain it or work it. Isaac Asimov speculated that gold was the "first metal." His reasoning is that gold by its chemistry is found in nature as nuggets of pure gold.
• In other words, gold, as rare as it is, is always found in nature as the metal that it is. There are a few other metals that sometimes occur natively, and as a result of meteors. Almost all other metals are found in ores, a mineral bearing rock, that require heat or some other process to liberate the metal.
• Another feature of gold is that it is workable as it is found, meaning that no technology beyond eyes to find a nugget and a hammer and an anvil to work the metal is needed. Stone hammer and stone anvil will suffice for technology.
• This is the result of gold's properties of malleability and ductility. The earliest tools were stone, bone, wood, and sinew. They sufficed to work gold.
• At some unknown point the connection between heat and the liberation of metals from rock became clear, rocks rich in copper, tin, and lead came into demand. These ores were mined wherever they were recognized. Remnants of such ancient mines have been found all over what is today the Middle East.
• Metalworking was being carried out by the South Asian inhabitants of Mehrgarh between 7000$-$3300 BC. The end of the beginning of metalworking occurs sometime around 6000 BC when copper smelting became common in the Middle East.
• The oxidation potential is important because it is one indicator of how tightly bound to the ore the metal is likely to be. As can be seen, iron is significantly higher than the other six metals while gold is dramatically lower than the more...

#### Fabrication Process

Fabrication Process
• Metal fabrication is the building of metal structures by cutting, bending, and assembling.
• Cutting is done by sawing, shearing, or chiseling torching with hand-held torches and via numerical control (CNC) cutters (using a laser, mill bits, torch, or water jet).
• Bending is done by hammering (manual or powered) or via press brakes and similar tools. Modem metal fabricators utilize press brakes to either coin or air-bend metal sheet into form. CNC-controlled back gauges utilize hard stops to position cut parts in order to place bend lines in the correct position. Off-line programing software now makes programing the CNC-controlled press brakes seamless and very efficient.
• Assembling (joining of the pieces) is done by welding, binding with adhesives, riveting, threaded fasteners, or even yet more bending in the form of a crimped seam. Structural steel and sheet metal are the usual starting materials for fabrication, along with the welding wire, flux, and fasteners that will join the cut pieces. As with other manufacturing processes, both human labor and automation are commonly used.
• The product resulting from fabrication may be called a fabrication. Shops that specialize in this type of metal work are called fab shops. The end products of other common types of metalworking, such as machining, metal stamping, forging, and casting, may be similar in shape and function, but those processes are not classified as fabrication.
• Fabrication shops and machine shops have overlapping capabilities, but fabrication shops generally concentrate on metal preparation and assembly as described above. By comparison, machine shops also cut metal, but they are more concerned with the machining of parts on machine tools. Firms that encompass both fab work and machining are also common.
• Blacksmithing has always involved fabrication, al-though it was not always called by that name.
• The products produced by welders, which are often referred to as weldments, are an example of fabrication.
• Boilermakers originally specialized in boilers, leading to their trade's name, but the term as used today has a broader meaning.
• Similarly, millwrights originally specialized in setting up grain mills and saw mills, but today they may be called upon for a broad range of fabrication work.
• Ironworkers, also known as steel erectors, also engage in fabrication. Often the fabrications for structural work begin as prefabricated segments in a fab shop, then are moved to the site by truck, rail, or barge, and finally are installed by erectors.
• Metal fabrication is a value added process that involves the construction of machines and structures from various raw materials. A fab shop will bid on a job, usually based on the engineering drawings, and if awarded the contract will build the product.
• Large fab shops will employ a multitude of value added processes in one plant or facility including welding, cutting, forming and machining. These large fab shops offer additional value to their customers by limiting the need for purchasing personnel to locate multiple vendors for different services.
• Metal fabrication jobs usually start with shop drawings including more...

#### Tool Engineering

Tool Engineering
• Tool and die makers are a class of machinists in the manufacturing industries who make jigs, fixtures, dies, molds, machine tools, cutting tools, gauges, and other tools used in manufacturing processes.
• Depending on which area of concentration a particular person works in, he or she may be called by variations on the name, including tool maker(toolmaker), die maker ,mold maker, tool fitter etc.
• Tool and die makers work primarily in tool room environments-sometimes literally in one room but more often in an environment with flexible, semipermeable boundaries from production work.
• They are skilled artisans (craftspeople) who typically learn their trade through a combination of academic coursework and hands-on instruction, with a substantial period of on-the-job training that is functionally an apprenticeship.
• Art and science are thoroughly intermixed in their work, as they also are in engineering. Manufacturing engineers and tool and die makers often work in close consultation as part of a manufacturing engineering team.
• There is often turnover between the careers, as one person may end up working in both at different times of their life, depending on the turns of their particular educational and career path.
• Both careers require some level of talent in both artistic/ artisanal/creative areas and math-and-science areas. Job-shop machinists can be any combination of toolmaker and production machinist.
• Some work only as machine operators, whereas others switch fluidly between tool room tasks and production tasks.
• Tool making typically means making tooling used to produce products. Common tooling includes metal forming rolls, cutting tools, fixtures, or even whole machine tools used to manufacture, hold, or test products during their fabrication. Due to the unique nature of a tool maker's work, it is often necessary to fabricate custom tools or modify standard tools.
• Die making is a subgenre of tool making that focuses on making and maintaining dies. This often includes making punches, dies, steel rule dies, and die sets.
• Precision is key in die making; punches and dies must maintain proper clearance to produce parts accurately, and it is often necessary to have die sets machined with tolerances of less than one thousandth of an inch.
• Although the details of training programs vary, many tool and die makers begin an apprenticeship with an employer, possibly including a mix of classroom training and hands-on experience.
• Some prior qualifications in basic mathematics, science, engineering science or design and technology can be valuable. Many tool and die makers attend a 4- to 5-year apprenticeship program to achieve the status of a journeyman tool and die maker.
• Today's employment relationships often differ in name and detail from the traditional arrangement of an apprenticeship, and the terms "apprentice" and "journeyman" are not always used, but the idea of a period of years of on-the-job training leading to mastery of the field still applies.
• The standard differentiation of jigs from fixtures is that a jig is what mounts onto a workpiece, whereas a fixture has the workpiece placed on it, into it, or more...

#### Metrology and Inspection

Metrology and Inspection
• Metrology is the science of measurement. Metrology includes all theoretical and practical aspects of measurement.
• Metrology is defined by the International Bureau of Weights and Measures (BIPM) as "the science of measurement, embracing both experimental and theoretical determinations at any level of uncertainty in any field of science and technology.
• Metrology is a very broad field and may be divided into three basic activities, though there is considerable overlap between the activities:
• Realization of these units of measurement in practice
• Application of chains of traceability linking measurements made in practice to reference standards.
• Metrology also has three basic subfields, all of which make use of the three basic activities, though in varying proportions:
$-$Scientific or fundamental metrology $-$Applied, technical or industrial metrology $-$Legal metrology
• Scientific or fundamental metrology concerns the establishment of quantity systems, unit systems, units of measurement, the development of new measurement methods, realisation of measurement standards and the transfer of traceability from these standards to users in society.
• The BIPM maintains a database of the metrological calibration and measurement capabilities of various institutes around the world. These institutes, whose activities are peer-reviewed, provide the top-level reference points for metrological traceability.
• In the area of measurement the BIPM has identified nine metrology areas including length, mass and time.
• Applied, technical or industrial metrology concerns the application of measurement science to manufacturing and other processes and their use in society, ensuring the suitability of measurement instruments, their calibration and quality control of measurements.
• Although the emphasis in this area of metrology is on the measurements themselves, traceability of the calibration of the measurement devices is necessary to ensure confidence in the measurements.
• Legal metrology "concerns activities which result from statutory requirements and concern measurement, units of measurement, measuring instruments and methods of measurement and which are performed by competent
• Such statutory requirements might arise from, amongst others, the needs for protection of health, public safety, the environment, enabling taxation, protection of consumers and fair trade.
• The OIML was set up to assist in harmonising such regulations across national boundaries to ensure that legal requirements do not inhibit trade. In Europe WELMEC was established to promote cooperation on the field of legal metrology.
• A core concept in metrology is metrological traceability defined by the Joint Committee for Guides in Metrology as "property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty".
• Metrological traceability permits comparison of measurements, whether the result is compared to the previous result in the same laboratory, a measurement result a year ago, or to the result of a measurement performed anywhere else in the world.
• Traceability is most often obtained by calibration, establishing the relation between the indication of a measuring instrument and the value of a measurement standard. These standards are usually coordinated by national metrological institutes.
• Traceability is used to extend measurement from a method that more...

#### Production Planning

Production Planning
• Production planning is the planning of production and manufacturing processes in a company or industry. It utilizes the resource allocation of activities of employees, materials and production capacity, in order to serve different customers.
• Different types of production methods, such as single item manufacturing, batch production, mass production, continuous production etc. have their own type of production planning.
• Production planning can be combined with production control into production planning and control, or it can be combined and or integrated into enterprise resource planning.
• Production planning is used in companies in several different industries, including agriculture, industry, amusement industry, etc.
• Production planning is a plan for the future production, in which the facilities needed are determined and arranged. A production planning is made periodically for a specific time period, called the planning horizon. It can comprise the following activities:
• Determination of the required product mix and factory load to satisfy customers needs.
• Matching the required level of production to the existing resources.
• Scheduling and choosing the actual work to be started in the manufacturing facility.
• Setting up and delivering production orders to production facilities.
• In order to develop production plans, the production planner or production planning department needs to work closely together with the marketing department and sales department. They can provide sales forecasts, or a listing of customer orders.
• The work is usually selected from a variety of product types which may require different resources and serve different customers.
• Therefore, the selection must optimize customer-independent performance measures such as cycle time and customer-dependent performance measures such as on-time delivery.
• A critical factors in production planning is "the accurate estimation of the productive capacity of available resources, yet this is one of the most difficult tasks to perform well."
• Production planning should always take "into account material availability, resource availability and knowledge of future demand."
• Modern production planning methods and tools have been developed since late 19th century. Under Scientific Management, the work for each man or each machine is mapped out in advance. The origin of production planning back goes another century.
• Advanced planning and scheduling refers to a manufacturing management process by which raw materials and production capacity are optimally allocated to meet demand. APS is especially well-suited to environments where simpler planning methods cannot adequately address complex trade-offs between competing priorities.
• Production scheduling is intrinsically very difficult due to the factorial dependence of the size of the solution space on the number of items/products to be manufactured.
• Capacity planning is the process of determining the production capacity needed by an organization to meet changing demands for its products. In the context of capacity planning, design capacity is the maximum amount of work that an organization is capable of completing in a given period.
• Effective capacity is the maximum amount of work that an organization is capable of completing in a given period due to constraints such as quality problems, delays, material handling, etc. The phrase is also used in business more...

#### Fluid Mechanics

Fluid Mechanics
• Fluid mechanics is the branch of physics which involves the study of fluids and the forces on them. Fluid mechanics can be divided into fluid statics, the study of fluids at rest; and fluid dynamics, the study of the effect of forces on fluid motion.
• It is branch of continuum mechanics, a subject which models matter without using the information that it is made out of atoms; that is, it models matter from a macroscopic viewpoint rather than from microscopic.
• Fluid mechanics, especially fluid dynamics, is an active field research with many problems that are partly or wholly unsolved.
• Fluid mechanics can be mathematically complex, and can be solved by numerical methods, typically using computers. A modem discipline, called computational fluid dynamics (CFD), is devoted to this approach to solving fluid mechanics problems.
• Particle image velocimetry, an experimental method for visualizing and analyzing fluid flow, also takes advantage of the highly visual nature of fluid flow.
• The study of fluid mechanics goes back at least to the days of an ancient Greece, when Archimedes investigated fluid statics and buoyancy and formulated his famous law known now as the Archimedes' principle, which was published in his work On Floating Bodies - generally considered to be the first major work on fluid mechanics.
• Fluid statics or hydrostatics is the branch of fluid mechanics that studies fluids at rest. It embraces the study the conditions under which fluids are at rest in stable equilibrium; and is contrasted with fluid dynamics, the study of fluids in motion.
• Hydrostatics is fundamental to hydraulics, the engineering of equipment for storing, transporting and using fluids. It is also relevant to geophysics and astrophysics to meteorology, to medicine and many other fields.
• Hydrostatics offers physical explanations for many phenomena of everyday life, such as why atmospheric pressure changes with altitude, why wood and oil float on water, and why the surface of water is always flat and horizontal whatever the shape of its container.
• Fluid dynamics is a sub discipline of fluid mechanics that deal with fluid flow-the natural science of fluids in motion.
• It has several sub disciplines itself, including aerodynamics and hydrodynamics. Fluid dynamics has a wide range of applications, including calculating force and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation.
• Some of its principles are even used in traffic engineering, where traffic is treated as a continuous fluid, and crowd dynamics.
• Fluid dynamics offers a systematic structure-which underlies these practical disciplines-that embraces empirical and semi-empirical laws derived from flow measurement and used to solve practical problems.
• The solution to a fluid dynamics problem typically involves calculating various properties of the fluid, such as velocity, pressure, density, and temperature, as functions of space and time.
• Like any mathematical model of the real world, fluid mechanics makes some basic assumptions about the materials being studied. These assumptions are turned into equations more...

#### Internal Combustion Engine (ICE)

Internal Combustion Engine (ICE)
• An internal combustion engine (ICE) is an engine where the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit.
• In an internal combustion engine the expansion of the high-temperature and high-pressure gases produced by combustion apply direct force to some component of the engine.
• The force is applied typically to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy. The first commercially successful internal combustion engine was created by Etienne Lenoir around 1859.
• The term internal combustion engine usually refers to an engine in which combustion is intermittent, such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine.
• Internal combustion engines are quite different from external combustion engines, such as steam or Stirling engines, in which the energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products.
• Working fluids can be air, hot water, pressurized water or even liquid sodium, heated in a boiler. ICEs are usually powered by energy-dense fuels such as gasoline or diesel, liquids derived from fossil fuels. While there are many stationary applications, most ICEs are used in mobile applications and are the dominant power supply for cars, aircraft, and boats.
• Typically an ICE is fed with fossil fuels like natural gas or petroleum products such as gasoline, diesel fuel or fuel oil. There's a growing usage of renewable fuels like biodiesel for compression ignition engines and bioethanol for spark ignition engines. Hydrogen is sometimes used, and can be made from either fossil fuels or renewable energy.
• Although various forms of internal combustion engines were developed before the 19th century, their use was hindered until the commercial drilling and production of petroleum began in the mid-1850s. By the late 19th century, engineering advances led to their widespread adoption in a variety of applications.
• Early internal combustion engines were started by hand cranking. Various types of starter motor were later developed. These included:
$-$ An auxiliary petrol engine for starting a larger petrol or diesel engine. The Hucks starter is an example $-$ Cartridge starters, such as the Coffman engine starter, which used a device like a blank shotgun cartridge. These were popular for aircraft engines            $-$ Pneumatic starters $-$ Hydraulic starters $-$ Electric starters
• Electric starters are now almost universal for small and medium-sized engines, while pneumatic starters are used for large engines.
• The first piston engines did not have compression, but ran on an air-fuel mixture sucked or blown in during the first part of the intake stroke. The most significant distinction between modern internal combustion engines and the early designs is the use of compression and, in particular, in-cylinder compression.
• The base of a reciprocating internal combustion engine is the engine block which more...

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