msc miscellanous

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msc miscellanous.txtToughness is the ability of a material to absorb energy and plastically deform without fracturing.[1] One definition of material toughness is the amount of energy per volume that a material can absorb before rupturing. It is alsodefined as the resistance to fracture of a material when stressed.Toughness requires a balance of strength and ductility.

Salt bath heat treatment is a heat treatment process comprising an immersion of the treated part into a molten salt(or salts mixture).

Fiberglass (or fibreglass) (also called glass-reinforced plastic, GRP,[1] glass-fiber reinforced plastic, or GFRP[2]) isa fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK (for German: Glasfaserverstrkter Kunststoff).

Fiberglass is a lightweight, extremely strong, and robust material. Although strength properties are somewhatlower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are muchless expensive. Its bulk strength and weight properties are also very favorable when compared to metals, and itcan be easily formed using molding processes.

The plastic matrix may be epoxy, a thermosetting plastic (most often polyester or vinylester) or thermoplastic.

Common uses of fiberglass include high performance aircraft (gliders), boats, automobiles, baths, hot tubs, water tanks, roofing, pipes, cladding, casts, surfboards and external door skins.

Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physicalproperties.[1] They all have in common their eponymous, asbestiform habit: long (ca. 1:20 aspect ratio), thinfibrous crystals. The prolonged inhalation of asbestos fibers can cause serious illnesses[2] including malignantlung cancer, mesothelioma, and asbestosis (a type of pneumoconiosis).[3] The European Union has banned alluse of asbestos[4], as well as the extraction, manufacture, and processing of asbestos products

Fiber (from the French Fibre[1]) is a rope or string used as a component of composite materials, or matted[disambiguation needed] into sheets to make products such as paper or felt. Fibers are often used in themanufacture of other materials. The strongest engineering materials are generally made as fibers, for examplecarbon fiber and Ultra-high-molecular-weight polyethylene.

Synthetic fibers can often be produced very cheaply and in large amounts compared to natural fibers, but for clothing natural fibers can give some benefits, such as comfort, over their synthetic counterparts.

Natural fibers

Main article: Natural fiber Natural fibers include those produced by plants, animals, and geological processes. They are biodegradable over time. They can be classified according to their origin:

Vegetable fibers are generally based on arrangements of cellulose, often with lignin: examples include cotton,hemp, jute, flax, ramie, sisal and bagasse. Plant fibers are employed in the manufacture of paper and textile(cloth).Wood fiber, distinguished from vegetable fiber, is from tree sources. Forms include groundwood,thermomechanical pulp (TMP) and bleached or unbleached kraft or sulfite pulps. Kraft and sulfite, also called

sulphite, refer to the type of pulping process used to remove the lignin bonding the original wood structure, thusfreeing the fibers for use in paper and engineered wood products such as fiberboard. Animal fibers consist largely of particular proteins. Instances are silkworm silk, spider silk, sinew, catgut, wool, seasilk and hair such as cashmere wool, mohair and angora, fur such as sheepskin, rabbit, mink, fox, beaver, etc.Mineral fibers include the asbestos group. Asbestos is the only naturally occurring long mineral fiber. Six mineralshave been classified as "asbestos" including chrysotile of the serpentine class and those belonging to theamphibole class: amosite, crocidolite, tremolite, anthophyllite and actinolite. Short, fiber-like minerals includewollastonite and palygorskite.Synthetic fibers [edit]

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msc miscellanous.txt

Main article: Synthetic fiber Synthetic generally come from synthetic materials such as petrochemicals but some types of synthetic fibers aremanufactured from natural cellulose, including rayon, modal, and Lyocell. Cellulose-based fibers are of two types,regenerated or pure cellulose such as from the cupro-ammonium process and modified cellulose such as thecellulose acetates.[2]

Fiber classification in reinforced plastics falls into two classes: (i) short fibers, also known as discontinuous fibers,with a general aspect ratio (defined as the ratio of fiber length to diameter) between 20 to 60, and (ii) long fibers,also known as continuous fibers, the general aspect ratio is between 200 to 500.[3]

Metallic fibers [edit]Metallic fibers can be drawn from ductile metals such as copper, gold or silver and extruded or deposited frommore brittle ones, such as nickel, aluminum or iron. See also Stainless steel fibers.

Carbon fiber [edit]Carbon fibers are often based on oxydized and via pyrolysis carbonized polymers like PAN, but the end product isalmost pure carbon.

Silicon carbide fiber [edit]Silicon carbide fibers, where the basic polymers are not hydrocarbons but polymers, where about 50% of thecarbon atoms are replaced by silicon atoms, so-called poly-carbo-silanes. The pyrolysis yields an amorphoussilicon carbide, including mostly other elements like oxygen, titanium, or aluminium, but with mechanical propertiesvery similar to those of carbon fibers.

Fiberglass [edit]Fiberglass, made from specific glass, and optical fiber, made from purified natural quartz, are also man-madefibers that come from natural raw materials, silica fiber, made from sodium silicate (water glass) and basalt fiber made from melted basalt.

Mineral fibers [edit]Mineral fibers can be particularly strong because they are formed with a low number of surface defects, asbestosis a common one.[4]

Cellulose fibers [edit]Cellulose fibers are a subset of man-made fibers, regenerated from natural cellulose. The cellulose comes fromvarious sources. Modal is made from beech trees, bamboo fiber is a cellulose fiber made from bamboo, seacell ismade from seaweed, etc.

Polymer fibers [edit]Polymer fibers are a subset of man-made fibers, which are based on synthetic chemicals (often frompetrochemical sources) rather than arising from natural materials by a purely physical process. These fibers aremade from:polyamide nylonPET or PBT polyester phenol-formaldehyde (PF)polyvinyl alcohol fiber (PVA) vinylon

polyvinyl chloride fiber (PVC) vinyonpolyolefins (PP and PE) olefin fiber acrylic polyesters, pure polyester PAN fibers are used to make carbon fiber by roasting them in a low oxygenenvironment. Traditional acrylic fiber is used more often as a synthetic replacement for wool. Carbon fibers and PFfibers are noted as two resin-based fibers that are not thermoplastic, most others can be melted.aromatic polyamids (aramids) such as Twaron, Kevlar and Nomex thermally degrade at high temperatures and donot melt. These fibers have strong bonding between polymer chainspolyethylene (PE), eventually with extremely long chains / HMPE (e.g. Dyneema or Spectra).Elastomers can even be used, e.g. spandex although urethane fibers are starting to replace spandex technology.

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msc miscellanous.txtpolyurethane fiber ElastolefinCoextruded fibers have two distinct polymers forming the fiber, usually as a core-sheath or side-by-side. Coatedfibers exist such as nickel-coated to provide static elimination, silver-coated to provide anti-bacterial properties andaluminum-coated to provide RF deflection for radar chaff. Radar chaff is actually a spool of continuous glass towthat has been aluminum coated. An aircraft-mounted high speed cutter chops it up as it spews from a movingaircraft to confuse radar signals.Microfibers [edit]Microfibers in textiles refer to sub-denier fiber (such as polyester drawn to 0.5 dn). Denier and Detex are twomeasurements of fiber yield based on weight and length. If the fiber density is known you also have a fiber diameter, otherwise it is simpler to measure diameters in micrometers. Microfibers in technical fibers refer to ultrafine fibers (glass or meltblown thermoplastics) often used in filtration. Newer fiber designs include extruding fiber that splits into multiple finer fibers. Most synthetic fibers are round in cross-section, but special designs can behollow, oval, star-shaped or trilobal. The latter design provides more optically reflective properties. Synthetic textilefibers are often crimped to provide bulk in a woven, non woven or knitted structure. Fiber surfaces can also be dullor bright. Dull surfaces reflect more light while bright tends to transmit light and make the fiber more transparent.

Very short and/or irregular fibers have been called fibrils. Natural cellulose, such as cotton or bleached kraft, showsmaller fibrils jutting out and away from the main fiber structure.[2]

Vulcanization or vulcanisation is a chemical process for converting rubber or related polymers into more durablematerials via the addition of sulfur[1] or other equivalent "curatives" or "accelerators". These additives modify thepolymer by forming crosslinks (bridges) between individual polymer chains.[2][3] Vulcanized materials are lesssticky and have superior mechanical properties.[4] A vast array of products are made with vulcanized rubber including tires, shoe soles, hoses, conveyer belts and hockey pucks. The process is named after Vulcan, Romangod of fire. Hard vulcanized rubber is sometimes sold under the brand names ebonite or vulcanite, and is used tomake hard articles such as bowling balls and saxophone mouth pieces.

Selection of Materials for Engineering PurposesThe selection of a proper material, for

engineering purposes, is one of the most difficultproblem for the designer. The best material is onewhich serve the desired objective at the minimumcost. The following factors should be consideredwhile selecting the material :1. Availability of the materials,2. Suitability of the materials for the working conditions in service, and3. The cost of the material.

Physical Properties of MetalsThe physical properties of the metals include luster, colour, size and shape, density, electric andthermal conductivity, and melting point. The following table shows the important physical propertiesof some pure metals.

Mechanical Properties of MetalsThe mechanical properties of the metals are those which are associated with the ability of thematerial to resist mechanical forces and load. These mechanical properties of the metal include strength,stiffness, elasticity, plasticity, ductility, brittleness, malleability, toughness, resilience, creep andhardness. We shall now discuss these properties as follows:1. Strength. It is the ability of a material to resist the externally applied forces without breakingor yielding. The internal resistance offered by a part to an externally applied force is called *stress.2. Stiffness.It is the ability of a material to resist deformation under stress. The modulus of elasticity is the measure of stiffness.

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msc miscellanous.txt3. Elasticity.It is the property of a material to regain its original shape after deformation whenthe external forces are removed. This property is desirable for materials used in tools and machines.It may be noted that steel is more elastic than rubber.4. Plasticity. It is property of a material which retains the deformation produced under loadpermanently. This property of the material is necessary for forgings, in stamping images on coins andin ornamental work.5. Ductility. It is the property of a material enabling it to be drawn into wire with the application of a tensile force. Aductile material must be both strong and plastic. The ductility is usuallymeasured by the terms, percentage elongation and percentage reduction in area. The ductile materialcommonly used in engineering practice (in order of diminishing ductility) are mild steel, copper,aluminium, nickel, zinc, tin and lead.

6. Brittleness. It is the property of a material opposite to ductility. It is the property of breakingof a material with little permanent distortion. Brittle materials when subjected to tensile loads, snapoff without giving any sensible elongation. Cast iron is a brittle material.7. Malleability. It is a special case of ductility which permits materials to be rolled or hammeredinto thin sheets. A malleable material should be plastic but it is not essential to be so strong. Themalleable materials commonly used in engineering practice (in order of diminishing malleability) arelead, soft steel, wrought iron, copper and aluminium.8. Toughness. It is the property of a material to resist fracture due to high impact loads likehammer blows. The toughness of the material decreases when it is heated. It is measured by theamount of energy that a unit volume of thematerial has absorbed after being stressed uptothe point of fracture. This property is desirablein parts subjected to shock and impact loads.9. Machinability. It is the property of amaterial which refers to a relative case withwhich a material can be cut. The machinabilityof a material can be measured in a number of ways such as comparing the tool life for cuttingdifferent materials or thrust required to removethe material at some given rate or the energy

required to remove a unit volume of thematerial. It may be noted that brass can beeasily machined than steel.10.Resilience. It is the property of amaterial to absorb energy and to resist shockand impact loads. It is measured by the amountof energy absorbed per unit volume withinelastic limit. This property is essential for spring materials.11.Creep. When a part is subjected toa constant stress at high temperature for a longperiod of time, it will undergo a slow andpermanent deformation called creep.Thisproperty is considered in designing internal

combustion engines, boilers and turbines.12.Fatigue.When a material issubjected to repeated stresses, it fails atstresses below the yield point stresses. Suchtype of failure of a material is known as*fatigue. The failure is caused by means of aprogressive crack formation which are usuallyfine and of microscopic size. This property isconsidered in designing shafts, connecting rods, springs, gears, etc.

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msc miscellanous.txt13.Hardness. It is a very important property of the metals and has a wide variety of meanings.It embraces many different properties such as resistance to wear, scratching, deformation andmachinability etc. It also means the ability of a metal to cut another metal.

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