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Material in Mechanical Design ABE 61 – MACHINE DESIGN FOR AB PRODUCTION ABE 61|Machine Design for AB Production Material in Mechanical Design But it is not, in the end, a material that we seek; it is a certain profile of properties. The stu...

Material in Mechanical Design ABE 61 – MACHINE DESIGN FOR AB PRODUCTION ABE 61|Machine Design for AB Production Material in Mechanical Design But it is not, in the end, a material that we seek; it is a certain profile of properties. The student must be confident in the definitions of moduli, strengths, damping capacities, thermal conductivities and the like may wish to skip this, using it for reference, when needed, for the precise meaning and units of the data in the selection charts which come later. ABE 61|Machine Design for AB Production Material in Mechanical Design Materials, one might say, are the food of design. A successful product - one that performs well, is good value for money and gives pleasure to the user - uses the best materials for the job, and fully exploits their potential and characteristics: brings out their flavor, so to speak. The classes of materials - metals, polymers, ceramics, and so forth. ABE 61|Machine Design for AB Production The classes of engineering materials It is conventional to classify the materials of engineering into the six broad classes shown in Figure below : metals, polymers, elastomers, ceramics, glasses and composites. The members of a class have features in common: similar properties, similar processing routes, and, often, similar applications. ABE 61|Machine Design for AB Production The classes of engineering materials ABE 61|Machine Design for AB Production  The Classes of Engineering Materials Metals have relatively high moduli. They can be made strong by alloying and by mechanical and heat treatment, but they remain ductile, allowing them to be formed by deformation processes. Certain high-strength alloys (spring steel, for instance) have ductilities as low as 2%, but even this is enough to ensure that the material yields before it fractures and that fracture, when it occurs, is of a tough, ductile type. Partly because of their ductility, metals are prey to fatigue and of all the classes of material, they are the least resistant to corrosion. ABE 61|Machine Design for AB Production  The Classes of Engineering Materials Ceramics and glasses, too, have high moduli, but, unlike metals, they are brittle. Their ‘strength’ in tension means the brittle fracture strength; in compression it is the brittle crushing strength, which is about 15 times larger. And because ceramics have no ductility, they have a low tolerance for stress concentrations (like holes or cracks) or for high contact stresses (at clamping points, for instance). ABE 61|Machine Design for AB Production The Classes of Engineering Materials Ductile materials accommodate stress concentrations by deforming in a way which redistributes the load more evenly; and because of this, they can be used under static loads within a small margin of their yield strength. Ceramics and glasses cannot. Brittle materials always have a wide scatter in strength and the strength itself depends on the volume of material under load and the time for which it is applied. ABE 61|Machine Design for AB Production The Classes of Engineering Materials So ceramics are not as easy to design with as metals. Despite this, they have attractive features. They are stiff, hard and abrasion-resistant (hence their use for bearings and cutting tools); they retain their strength to high temperatures; and they resist corrosion well. They must be considered as an important class of engineering material ABE 61|Machine Design for AB Production The Classes of Engineering Materials Polymers and elastomers are at the other end of the spectrum. They have moduli which are low, roughly 5O times less than those of metals, but they can be strong - nearly as strong as metals. A consequence of this is that elastic deflections can be large. They creep, even at room temperature, meaning that a polymer component under load may, with time, acquire a permanent set. ABE 61|Machine Design for AB Production The Classes of Engineering Materials And their properties depend on temperature so that a polymer which is tough and flexible at 20°C may be brittle at the 4°C of a household refrigerator, yet creep rapidly at the 100°C of boiling water. None have useful strength above 200°C. If these aspects are allowed for in the design, the advantages of polymers can be exploited. When combinations of properties, such as strength per-unit-weight, are important, polymers are as good as metals. ABE 61|Machine Design for AB Production The Classes of Engineering Materials They are easy to shape: complicated parts performing several functions can be molded from a polymer in a single operation. The large elastic deflections allow the design of polymer components which snap together, making assembly fast and cheap. And by accurately sizing the mold and pre-coloring the polymer, no finishing operations are needed. Polymers are corrosion resistant, and they have low coefficients of friction. Good design exploits these properties. ABE 61|Machine Design for AB Production  The Classes of Engineering Materials Composites combine the attractive properties of the other classes of materials while avoiding some of their drawbacks. They are light, stiff and strong, and they can be tough. Most of the composites at present available to the engineer have a polymer matrix - epoxy or polyester, usually - reinforced by fibers of glass, carbon or Kevlar. ABE 61|Machine Design for AB Production  The Classes of Engineering Materials They cannot be used above 250°C because the polymer matrix softens, but at room temperature their performance can be outstanding. Composite components are expensive and they are relatively difficult to form and join. So despite their attractive properties the designer will use them only when the added performance justifies the added cost ABE 61|Machine Design for AB Production The Classes of Engineering Materials Other Engineering Materials needed in Machine Design. PAES 301 – 320 (Reading Assignment) ABE 61|Machine Design for AB Production  Mechanical Properties of Materials The mechanical properties of materials define the behavior of materials under the action of external forces called loads. There are a measure of strength and lasting characteristics of the material in service and are of good importance in the design of tools, machines, and structures. The mechanical properties of metals are determined by the range of usefulness of the metal and establish the service that is expected. ABE 61|Machine Design for AB Production Mechanical Properties of Materials Mechanical properties are also useful for help to specify and identify the metals. And the most common properties considered are strength, hardness, ductility, brittleness, toughness, stiffness and impact resistance ABE 61|Machine Design for AB Production  List of Mechanical Properties of Materials The following are the mechanical properties of materials. Strength Stiffness Elasticity Ductility Plasticity Malleability Hardness Cohesion Toughness Impact strength Brittleness Fatigue Creep ABE 61|Machine Design for AB Production Mechanical Properties of Materials 1. Strength Strength is the mechanical property that enables a metal to resist deformation load. The strength of a material is its capacity to withstand destruction under the action of external loads. The stronger the materials the greater the load it can withstand ABE 61|Machine Design for AB Production  Mechanical Properties of Materials 2. Elasticity According to dictionary elasticity is the ability of an object or material to resume its normal shape after being stretched or compressed. When a material has a load applied to it, the load causes the material to deform. The elasticity of a material is its power of coming back to its original position after deformation when the stress or load is released. Heat-treated springs, rubber etc. are good examples of elastic materials. ABE 61|Machine Design for AB Production  Mechanical Properties of Materials 3. Plasticity The plasticity of a material is its ability to undergo some permanent deformation without rupture(brittle). Plastic deformation will take place only after the elastic range has been exceeded. Pieces of evidence of plastic action in structural materials are called yield, plastic flow and creep. Materials such as clay, lead etc are plastic at room temperature, and steel plastic when at bright red- heat. ABE 61|Machine Design for AB Production  Mechanical Properties of Materials 4. Hardness The resistance of a material to force penetration or bending is hardness. The hardness is the ability of a material to resist scratching, abrasion, cutting or penetration. Hardness indicates the degree of hardness of a material that can be imparted particularly steel by the process of hardening. It determines the depth and distribution of hardness is introduce by the quenching process. ABE 61|Machine Design for AB Production  Mechanical Properties of Materials Scratch Hardness Scratch Hardness is the ability of materials to the oppose the scratches to outer surface layer due to external force. Indentation Hardness It is the ability of materials to oppose the dent due to punch of external hard and sharp objects. Rebound Hardness Rebound hardness is also called as dynamic hardness. It is determined by the height of “bounce” of a diamond tipped hammer dropped from a fixed height on the material. ABE 61|Machine Design for AB Production Mechanical Properties of Materials 5. Toughness It is the property of a material which enables it to withstand shock or impact. Toughness is the opposite condition of brittleness. The toughness is may be considering the combination of strength and plasticity. Manganese steel, wrought iron, mild steel etc are examples of toughness materials. ABE 61|Machine Design for AB Production  Mechanical Properties of Materials 6. Brittleness The brittleness of a property of a material which enables it to withstand permanent deformation. Cast iron, glass are examples of brittle materials. They will break rather than bend under shock or impact. Generally, the brittle metals have high compressive strength but low in tensile strength. ABE 61|Machine Design for AB Production Mechanical Properties of Materials 7. Stiffness It is a mechanical property. The stiffness is the resistance of a material to elastic deformation or deflection. In stiffness, a material which suffers light deformation under load has a high degree of stiffness. The stiffness of a structure is important in many engineering applications, so the modulus of elasticity is often one of the primary properties when selecting a material ABE 61|Machine Design for AB Production Mechanical Properties of Materials 8. Ductility The ductility is a property of a material which enables it to be drawn out into a thin wire. Mild steel, copper, aluminum are the good examples of a ductile material. ABE 61|Machine Design for AB Production Mechanical Properties of Materials 9. Malleability The malleability is a property of a material which permits it to be hammered or rolled into sheets of other sizes and shapes. Aluminum, copper, tin, lead etc are examples of malleable metals. ABE 61|Machine Design for AB Production  Mechanical Properties of Materials 10. Cohesion It is a mechanical property. The cohesion is a property of a solid body by virtue of which they resist from being broken into a fragment. 11. Impact Strength The impact strength is the ability of a metal to resist suddenly applied loads. ABE 61|Machine Design for AB Production Mechanical Properties of Materials 12. Fatigue The fatigue is the long effect of repeated straining action which causes the strain or break of the material. It is the term ‘fatigue’ use to describe the fatigue of material under repeatedly applied forces. ABE 61|Machine Design for AB Production Mechanical Properties of Materials 13. Creep The creep is a slow and progressive deformation of a material with time at a constant force. The simplest type of creep deformation is viscous flow. Some metals are generally exhibiting creep at high temperature, whereas plastic, rubber, and similar amorphous material are very temperature sensitive to creep. The force for a specified rate of strain at constant temperature is called creep strength. ABE 61|Machine Design for AB Production Classification of Metals and Alloys General properties in all metals Physical Properties: Metals are hard, non-adhesive, cold and smooth,they are very often shiny and strong. They are also ductille and malleable, do not break easily. Metals are very good conductors of electricity, sound and heat. When temperature rises they expand, and when it falls, they always contract. They can be easily welded to other metals. ABE 61|Machine Design for AB Production Classification of Metals and Alloys General properties in all metals Chemical Properties: Metals react with oxygen in water and air. It's known as oxidation or rusting and it's a reddish- or yellowish-brown flaky coating of iron oxide that is formed on iron or steel, especially in the presence of moisture. ABE 61|Machine Design for AB Production Classification of Metals and Alloys General properties in all metals Ecological Properties: Most metal are recyclable and some metals such as lead or mercury are toxic and they are a danger for humans being and for the environment. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Classification of metals Metals can be divided into two main groups: ferrous metals are those which contain iron and non-ferrous metals that are those which contain no iron. ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Ferrous Metals) Ferrous Metals Pure Iron is of little use as an engineering material because it is too soft and ductile. When iron cools and changes from a liquid to a solid, most of the atoms in the metal pack, tightly together in orderly layers. Some, however. become misaligned, creating areas of weaknesses called dislocations. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Ferrous Metals When a piece of iron is put under stress, layers of atoms in these areas slip over one another and the metal deforms. This begins to explain the ductility of soft iron. By adding carbon to the iron however, we can produce a range of alloys with quite different properties. We call these the carbon steels. An alloy is a mixture of two or more chemical elements and the primary element is a metal. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Carbon Steels: their properties and uses Mild Steel: carbon content between 0,1% and 0,3%. Properties: less ductile but harder and tougher than iron, grey colour, corrodes easily. Uses: girders or beams, screws, nut and bolts, nails, scaffolding, car bodies, storage units, oil drums. ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Ferrous Metals) Carbon Steels: their properties and uses Medium carbon steel contains between 0,3% and 0,7% carbon. Properties: harder and less ductile than mild steel, tough and have a high tensile strength. Uses: it's used for the manufacture of products which have to be tough and hard wearing like gears, tools, keys, etc ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Ferrous Metals) Carbon Steels: their properties and uses High carbon steel contains between 0,7% and 1,3% carbon. Properties: Very hard and brittle material. Uses: It's used for cutting tools and products which have to withstand wear such as guillotine, springs, etc. ABE 61|Machine Design for AB Production  Classification of Metals and Alloys (Ferrous Metals) Carbon Steels: their properties and uses Stainless steel are iron and chromium alloys. A wide range of steels are available with chromium content between 13% and 27%. Properties: Chromium prevents rusting with an oxide film. Ductility, hardness and tensile strength. It's also a shiny attractive metal. Uses: Cutlery, sinks, pipes, car pieces, etc. Grey Cast Iron is an alloy of iron (94%), carbon (3%) silicon (2%) and some traces of magnesium, sulphur and phosphorous. Properties: brittle but extremely hard and resistant, it corrodes by rusting, Uses: pistons, machinery parts, streets lamps, drain covers, tools. ABE 61|Machine Design for AB Production  Classification of Metals and Alloys (Ferrous Metals) Other chemical elements can be added to steel, to improve or achieve certain properties. Here you are some examples: Silicon makes the alloy magnetic and improves elasticity. Manganese makes the alloy harder and heat- resistant. It's used to make stainless steel. Nickel improves strenght and prevents corrosion. Tungsten makes the steel harder, more heat- resistant and prevents corrosion. Chromium makes the alloy harder and tougher and more rustproof. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Non-ferrous metals They are metals that don't contain iron. They have a lot of uses but they are often expensive because they are more difficult to extract. ABE 61|Machine Design for AB Production  Classification of Metals and Alloys (Non-ferrous metals) Aluminum It's the most abundant metal in the earth's crust and after steel, is the most widely used of all the metals, today. Properties: Silvery white color, light, highly resistant to corrosion, soft, malleable and ductile, low density, good conductor of both electricity and heat. Uses: high voltage power lines, planes, cars, bicycles, light metal work. roofing and windows and doors units, decoration, kitchen tools and drink cans. ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Non-ferrous metals) Copper It's a pure metal that is the world's third most important metal, in terms of volume of consumption. Properties: a reddish-brown metal, ductile and moderately strong, very good conductor of electricity and heat,It corrodes very easily. Uses: electrical wire, telephone lines, domestic hot water cylinder and pipes, car radiator core, decoration, architecture. ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Non-ferrous metals) Brass This term "brass" covers a wide range of copper-zinc alloys. Properties: It's gold in color. It has very good anticorrosive properties and it's resistant to wear. Uses: Handicrafts, jewelry, plumbing, capacitors and turbine ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Non-ferrous metals) Magnesium It's shiny and silvery white. Properties: It's very light, soft and malleable, but not very ductile. It reacts very strongly with oxygen. Uses: Fireworks, aerospace industry, car industry. ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Non-ferrous metals) Tin It's a shiny white metal. Properties: It doesn't oxidize at room temperatures, it's very soft. Uses: Soft-soldering, tin foil and tin plate. ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Non-ferrous metals) Lead It's a silvery grey metal. Properties: Soft and malleable. It's toxic when its fumes are inhaled. Uses: Batteries, it's use as an additive in glass for giving hardness and weight. ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Non-ferrous metals) Bronze It's an alloy of copper and tin. Properties: High resistant to wear and corrosion. Uses: Boat propellers, filters, church bells, sculpture, bearings and cogs. ABE 61|Machine Design for AB Production Classification of Metals and Alloys (Non-ferrous metals) Zinc It's a bluish grey shiny metal. Properties: Anticorrosive, not very hard, weak at low temperatures. Uses: Roofing, plumbing because it stops corrosion. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Classification of Alloys There are several alloys of various metals, such as alloys of Aluminum, Potassium, Iron, Cobalt, Nickel, Copper, Gallium, Silver, Tin, Gold, Mercury, Lead, Bismuth, Zirconium, and rare earth. Based on the presence or absence of Iron, alloys can be classified into: Ferrous alloys: Contain Iron as a major component. A few examples of ferrous alloys are Stainless Steel, Cobalt, Gallium, Silver, Gold, Bismuth, and Zirconium. Non-ferrous alloys: Do not contain Iron as a major component. For example, Aluminium, Brass, Bronze, Copper, Tin, Nickel, Magnesium, and Titanium are some common non-ferrous alloys. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Different Types of Metal Alloys Copper are essentially commercially pure copper, which ordinarily is very soft and ductile, containing up to about 0.7% total impurities. These materials are used for their electrical and thermal conductivity, corrosion resistance, appearance and color, and ease of working. They have the highest conductivity of the engineering metals and are very ductile and easy to braze, and generally to weld. Typical applications include electrical wiring and fittings, bus bars, heat exchangers, roofs, wall cladding, tubes for water, air and process equipment. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Different Types of Metal Alloys High copper alloys contain small amounts of various alloying elements such as beryllium, chromium, zirconium, tin, silver, sulphur or iron. These elements modify one or more of the basic properties of copper, such as strength, creep resistance, machinability or weldability. Most of the uses are similar to those given above for coppers, but the conditions of application are more extreme. ABE 61|Machine Design for AB Production  Classification of Metals and Alloys Different Types of Metal Alloys Brasses are copper zinc alloys containing up to about 45% zinc, with possibly small additions of lead for machinability, and tin for strength. Copper zinc alloys are single phase up to about 37% zinc in the wrought condition. The single phase alloys have excellent ductility, and are often used in the cold worked condition for better strength. Alloys with more than about 37% zinc are dual phase, and have even higher strength, but limited ductility at room temperature compared to the single phase alloys. The dual phase brasses are usually cast or hot worked. Typical uses for brasses are architecture, drawn & spun containers and components, radiator cores and tanks, electrical terminals, plugs and lamp fittings, locks, door handles, name plates, plumbers hardware, fasteners, cartridge cases, cylinder liners for pumps. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Different Types of Metal Alloys Bronzes are alloys of copper with tin, plus at least one of phosphorus, aluminum, silicon, manganese and nickel. These alloys can achieve high strengths, combined with good corrosion resistance. They are used for springs and fixtures, metal forming dies, bearings, bushes, terminals, contacts and connectors, architectural fittings and features. The use of cast bronze for statuary is well know ABE 61|Machine Design for AB Production Classification of Metals and Alloys Different Types of Metal Alloys Copper nickel are alloys of copper with nickel, with a small amount of iron and sometimes other minor alloying additions such as chromium or tin. The alloys have outstanding corrosion resistance in waters, and are used extensively in sea water applications such as heat exchangers, condensers, pumps and piping systems, sheathing for boat hulls. ABE 61|Machine Design for AB Production Classification of Metals and Alloys Different Types of Metal Alloys Nickel silvers contain 55 – 65% copper alloyed with nickel and zinc, and sometimes an addition of lead to promote machinability. These alloys get their misleading name from their appearance, which is similar to pure silver, although they contain no addition of silver. They are used for jewelry and name plates and as a base for silver plate (EPNS), as springs, fasteners, coins, keys and camera parts. ABE 61|Machine Design for AB Production  Manufacturing Processes Manufacturing processes create finished goods from various raw materials. The manufacturing processes to the transformation of metals and plastics into usable forms. Obviously, this is a gross simplification in that just about every product--from hot dogs to circuit boards—goes through a series of manufacturing steps that transform it from its constituent ingredients. But it offers a good place to start. Generalizing again, manufacturing processes can be thought of in terms of primary and secondary processes, where primary processes are used in creating basic forms and secondary processes are used to alter or add features to these forms. ABE 61|Machine Design for AB Production Manufacturing Processes The major categories are: Metal Casting, Bulk/Metal Deformation, Sheet Metalworking/metal forming, Machining, Polymer Processing, Powder Metallurgy, Finishing and Assembly. Other non-value added processes are inspection, testing, and quality assurance. ABE 61|Machine Design for AB Production  Manufacturing Processes Metal casting Casting creates complex shapes from molten metal. Sand casting creates a two-piece sand mold around a pattern. The resulting mold is then split apart, the pattern removed, and reassembled with risers, gates, and sprues added to direct the flow of the molten metal. After the pour, the metal cools and solidifies, following which the mold is broken away to reveal the finished casting. ABE 61|Machine Design for AB Production  Manufacturing Processes Metal casting Die casting uses permanent molds into which low melt point metals such as zinc are injected under pressure. Investment casting creates intricate wax patterns that are coated with slurry, the wax melted out, then filled with molten metal. The process was originally invented for making jewelry and, sometimes referred to as the lost-wax process, has become a method for casting complex parts such as turbine blades. Other casting methods include permanent mold casting and centrifugal casting ABE 61|Machine Design for AB Production Manufacturing Processes Metal Casting: 1- Expandable molds: sand, plaster, ceramics – 2- Permanent molds: Die, permanent molds, centrifugal – 3- Special processes: investment, shell, vacuum casting ABE 61|Machine Design for AB Production  Manufacturing Processes Die Casting Process similar to injection molding, but used for metals such as zinc, tin, lead, aluminum and copper. Two types of die casting machines: Hot chamber: for low melting metals such as zinc, tin, and lead. Aluminum and copper cannot be die casted in a hot chamber machine. Cold chamber: metal melted in a chamber separated from the machine. Design impact on die casting similar to design impact on injection molding. ABE 61|Machine Design for AB Production  Manufacturing Processes Bulk/Metal deformation Metal deformation is used to transform bulk materials in the form of billets, blooms, and slabs as they come from a mill into other shapes such as pipe or bars. Extrusion is one such process, where ductile metals such as copper and aluminum are forced through dies to produce common shapes such as copper tubing or aluminum angles. Tubing manufacturing typically uses a mandrel in addition to a die to produce a hollow cross-section. Many extrusions are made in 40-ft. lengths to enable their transport by a trailer. ABE 61|Machine Design for AB Production Manufacturing Processes Bulk/Metal deformation Forging uses hydraulic die sets or open dies and hammers to plastically deform usually hot metal into net shapes, oftentimes starting with a rough approximation of the finished shape called a blocked preform. Forging can produce moderately complex shapes in parts that are up to 3 ft. long. Forging can be used to apply beneficial changes to the grain structure of metals. ABE 61|Machine Design for AB Production Manufacturing Processes Bulk/Metal deformation Rolling transforms mill products into finished raw materials such as I-beams, plates, and sheets. The process may be performed hot or cold, with cold rolling achieving higher yield strength and better surface finishes than hot rolling but requiring much more work. Typically, ingots are rolled into blooms, slabs, or billets which are then rolled further to make structural shapes, sheet metal, or bars and rods. ABE 61|Machine Design for AB Production  Manufacturing Processes Bulk/Metal deformation Bar drawing is used to further reduce bar stock and improve surface characteristics and strength through a cold, die puling process. Straight lengths of circular and rectangular bar stock are produced in this manner with cross-sectional sizes up to 6 in. possible. Wire drawing continues the process of bar drawing by pulling ductile materials through increasingly smaller dies to wind up with steel, aluminum, and copper wire. The resulting wire is usually small and ductile enough that it can be wound onto spools of significant capacity. ABE 61|Machine Design for AB Production  Manufacturing Processes Bulk/Metal deformation: Rolling ( plates, sheets, bars, wire, seamless pipes, structural shapes, rails) Forging: Open die (for rough shape transformation) Close die (take up internal shape of dies) Heading (bolt and rivet heads) Swaging or radial forging ( for sizing and pointing) Extrusion and Drawing: Direct (hot and cold) Hydrostatic ABE 61|Machine Design for AB Production  Manufacturing Processes Sheet Metalworking / metal forming Sheet metal operations can be grouped as shearing, blanking, drawing, punching, embossing, and bending. Sheet metal is cut into smaller straight-edged pieces by shearing. Shearing can be done manually by inserting the piece in a metal shear, or, in the case of coiled material, continuously as the material is drawn off a roll. Automated operations will often pull this narrower strip through a progressive forming die where the parts are formed sequentially as they index through each station of the die. ABE 61|Machine Design for AB Production  Manufacturing Processes Sheet Metalworking / metal forming Drawing gradually pushes the material into a die cavity that deepens with each step through the die. Punching creates holes and slots where needed. Bending creates tabs and other features that run perpendicular to the plane of the original material. Blanking shears the finished part from the remaining coil material that has served to carry the forming part through the die. Any of these operations can of course be done individually: parts can be blanked on one press station and loaded into a second press for forming, bending, etc. ABE 61|Machine Design for AB Production  Manufacturing Processes Sheet Metalworking/ metal forming: Shearing operations: Blanking, Punching, Slitting, Steel rules, Nibbling Shaping operations: Drawing (shallow and deep), Bending, Tube bending, Stretching, Ironing, Rubber forming, Spinning, Peening, Explosive forming, Magnetic forming Basic equipment for sheet metalworking: Mechanical presses Hydraulic presses Pneumatic presses ABE 61|Machine Design for AB Production  Manufacturing Processes Machining: Machining uses various cutting tools, abrasive wheels, as well as some unusual media such as water or sparks, to remove material from round and bar stock, castings, etc. to produce accurate finished goods. Machining methods include sawing, turning, boring, reaming, etc. and are oftentimes performed as secondary operations to clean up parts or to create surfaces that are suitable for assembly. ABE 61|Machine Design for AB Production  Manufacturing Processes Machining: In some instances, the part is moved and coordinated with the motion of the tools, such as turning, and in other situations, the part is held stationary and the tool moves over it, such as sawing. Machine tools have come a long way from the days of belt-driven lathes and now almost invariably take the form of multi-axis computer-controlled milling and turning centers. Additional information on machining may be found in our related guides on the Different Machining Processes and the Types of Machining. ABE 61|Machine Design for AB Production  Manufacturing Processes Machining: The major categories are: Cutting, Abrasives, and Nontraditional Cutting: Circular shapes: Turning, Boring, Drilling Various shapes: Milling, Planing, Shaping, Broaching, Sawing, Gear forming, Gear generating. Abrasives: Bonded: Grinding, Honing, Coated abrasives Loose: Ultrasonic, Abrasive-jet, Lapping, Polishing, Buffing ABE 61|Machine Design for AB Production Manufacturing Processes Machining (Continued): Non Traditional: Necessitated by one of the following conditions: High hardness or strength of materials, too flexible, slender or delicate to withstand cutting or grinding forces, complex shapes, very small diameter holes, high surface finish quality, localized stress in workpieces. Processes: Electrical-Discharge, Chemical, Electro- Chemical grinding, Laser-beam, Electron-beam ABE 61|Machine Design for AB Production  Manufacturing Processes Polymer Processing Polymer processing involves the forming of both thermoset and thermoplastic materials usually by molding but also by subtractive methods such as machining. Of the various molding methods, compression, blow, and injection molding are the most common. All three use metal dies whose cavities are shaped in the form of the desired plastic part. In compression molding, an elastomer charge is placed between heated die halves which are subsequently closed to force the material into the shape of the cavity. ABE 61|Machine Design for AB Production  Manufacturing Processes Polymer Processing This is a common method of making tires. Transfer molding is another compression molding technique in which the heated polymer is injected into the closed mold. Blow molding is a common method for making plastic bottles. Here, a softened parison is filled with air to force it against the walls of the closed mold halves. Injection molding uses an auger to soften plastic pellets in a barrel and inject the resulting “shot” under high pressure into a usually multi-cavity mold. ABE 61|Machine Design for AB Production  Manufacturing Processes Polymer Processing Thermoforming is another polymer processing method that shapes sheets or films of thermoplastic into cavities or over plugs usually using vacuum or air to pull or push the softened material against the mold surfaces. Familiar shapes such as food packages and kiddie pools are made in this manner. ABE 61|Machine Design for AB Production  Manufacturing Processes Polymer Processing Rotomolding is used to produce large hollow shapes such as kayaks by relying on the centrifugal force imparted to molten plastic as it spins within a rotating mold. Polyurethane is often cast by pouring it into open silicone rubber molds. ABE 61|Machine Design for AB Production  Manufacturing Processes Polymer Processing The most common processes: – Injection Molding – Compression Molding – Transfer molding Injection Molding: Screw-type injection molding machine. Thermoplastic materials in pellet form Mold features: mold halves, sprue, gate, runners, cooling system, ejector pins Design features that increase cost of production: shape complexity, uneven thicknesses, and undercuts (internal and external). ABE 61|Machine Design for AB Production  Manufacturing Processes Polymer Processing Compression Molding Used for thermoset plastics Raw material is a slug of material called charge Mold is similar to mold used in injection molding, but noted absence of sprue, gate, and runners Design features that increase production costs: complex shapes, and external undercuts Machine is hydraulically driven ABE 61|Machine Design for AB Production  Manufacturing Processes Polymer Processing Transfer Molding Process quite similar to compression molding except for construction of mold Mold has two portion: Upper portion where slug is heated and melted Lower portion where molten slug is force to take up shape of mold ABE 61|Machine Design for AB Production  Manufacturing Processes Finishing Finishing encompasses many final operations that make a part ready for assembly. Finishing steps occur after assembly as well, such as post-weld heat treating. Finishing operations include plating, painting, sprue removing, polishing, deburring, etc., depending upon prior manufacturing operations and the intended application of the finished part. ABE 61|Machine Design for AB Production  Manufacturing Processes Finishing Finishing can range from simple manual polishing to sophisticated surface treatments such as shot peening. Heat treating is an important step in the finishing of many metal parts as the primary manufacturing processes can impart undesirable characteristics such as brittleness which need to be baked out. ABE 61|Machine Design for AB Production  Manufacturing Processes Assembling Assembly is where the different parts that compose a finished product come together. Various forms of fastening are often used, including mechanical forms such as screws and rivets, fusion methods such as welding, bonding techniques such as brazing and gluing, and interference methods such as press and shrink fitting. Some assemblies are more permanent than others, as in weldments, which are often called “fabrications” rather than “assemblies.” ABE 61|Machine Design for AB Production  Manufacturing Processes Assembling Other assembly features may be built into the part itself, for instance, plastic tabs and slots made during molding that allow for parts to be snapped together. Assembly often involves quality control checks which frequently have followed along through the entire manufacturing process of a product’s constituent parts. Good engineering practice takes into account the ease and accuracy with which parts are assembled. ABE 61|Machine Design for AB Production  Standard Sizes of Materials ASTM's steel standards are instrumental in classifying, evaluating, and specifying the material, chemical, mechanical, and metallurgical properties of the different types of steels, which are primarily used in the production of mechanical components, industrial parts, and construction elements, as well as other accessories related to them. The steels can be of the carbon, structural, stainless, ferritic, austenitic, and alloy types. These steel standards are helpful in guiding metallurgical laboratories and refineries, product manufacturers, and other end-users of steel and its variants in their proper processing and application procedures to ensure quality towards safe use. ABE 61|Machine Design for AB Production  Standard Sizes of Materials ASTM's plastics standards are instrumental in specifying, testing, and assessing the physical, mechanical, and chemical properties of a wide variety of materials and products that are made of plastic and its polymeric derivatives. During processing, these synthetic or semisynthetic organic solids have a very malleable characteristic that allows them to be molded into an assortment of shapes, making them very suitable for the manufacture of various industrial products. These plastic standards allow plastic manufacturers and end-users to examine and evaluate their material or product of concern to ensure quality and acceptability towards safe utilization. ABE 61|Machine Design for AB Production  Standard Sizes of Materials These are the standards for steels and plastics based on ASTM. https://www.astm.org/Standards/steel- standards.html https://www.astm.org/Standards/plastics- standards.html For other machine parts, the ASAE standards is used by PAES https://www.asabe.org/Publications- Standards/Standards-Development/National- Standards/Published-Standards ABE 61|Machine Design for AB Production  Material Selection and Specifications Materials Selection Process A flowchart for the materials selection process is shown in Figure. The process consists of the following steps: ABE 61|Machine Design for AB Production Material Selection and Specifications Materials Selection Process ABE 61|Machine Design for AB Production  Material Selection and Specifications Materials Selection Process 1. Identify product design requirements 2. Identify product element design requirements 3. Identify potential materials 4. Evaluate materials 5. Determine whether any of the materials meet the selection criteria 6. Select materials ABE 61|Machine Design for AB Production  Material Selection and Specifications Materials Selection Process During the process of identifying and evaluating materials, a design team may determine that there are no materials that can be considered for use for a product element. In this situation, the design team has the following options: 1. Modify the design of the product element. 2. Modify the design of the product or subassembly that directly uses the product element. 3. Modify the design requirements of the product. 4. Invent a new material. 5. Cancel the product. ABE 61|Machine Design for AB Production  Material Selection and Specifications Materials Selection Process It is critical that design teams determine whether there are no options as soon as possible in the design process because it will give them the option of modifying the design or design requirements of the product element, subassembly, or product when it is still easy and inexpensive to make changes. Waiting too long will force design teams to consider either trying to invent a new material or canceling the product. Inventing a new material adds cost and risk to the development effort. However, the added cost and risk may be worthwhile if there is an invention that provides the product with a competitive advantage compared to products from other companies. Finally, canceling a product may be undesirable; however, it is preferable to spending time and money developing a product that does not meet the customer's wants and needs. ABE 61|Machine Design for AB Production  Material Selection and Specifications Materials Selection Process There is one more option that the flowchart does not show—moving forward with a suboptimum material. This means that the product element will not have the necessary performance or reliability, which reduces the likelihood of having a successful product. Waiting until all the relevant design requirements have been identified is important because doing so will prevent a design team from pursuing suboptimum materials based on incomplete information. Taking the time to make sure that all the relevant requirements have been identified will increase the chances of selecting optimum materials and enabling a successful product. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Factors in process selection Regardless of the material selection process employed, the result will be the selection of a suitable material or materials. The material itself will limit the manufacturing processes that can be used, as not all materials are suitable for all processes. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection For example, when considering joining processes, cast iron cannot be used for resistance welding. However, there are a number of factors common to both the material and process selection decisions: the number of components to be made; the component size; the component weight; the precision required; the surface finish and appearance required. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection All of these factors have already been considered at the material evaluation stage. However, In terms of the material evaluation for process planning, the focus will be firmly on ‘manufacturability’ or ‘processability’, as it is also known. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection This is defined as the ability of a material to be worked or shaped into the finished component (Farag, 1979) and is sometimes referred to as ‘workability’. Thus terms such as ‘weldability’, ‘castability’, ‘formability’, ‘machinability’ are used to describe how easily the material can be used for specific processes. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection The workability will also have a significant influence on the quality of the part, where quality is defined by three factors (Dieter, 1988): freedom from defects; surface finish; dimensional accuracy and tolerances. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Thus, the combination of material and process will have a significant bearing on the quality of the part and thus the process selected must be appropriate for the material. Finally, apart from all of the above technical factors, there are also the economic factors to be considered. Many of the decisions to be made in the design and manufacture of a product will be influenced by the costs involved. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection Therefore, the total cost of the product must be considered as early as possible. Other economic considerations will be based on the quantity required in terms of the production volume, the production rate and the economic batch size. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection Figure below illustrates some of the factors that influence both material and process selection. ABE 61|Machine Design for AB Production  Material Selection and Specifications Materials Selection: Design Requirements This discusses the first step of the process – identify the design requirements for the component or joint. As a reminder, here are the steps for the materials selection process: Identify the design requirements Identify the materials selection criteria. Identify candidate materials. Evaluate candidate materials. Select materials. ABE 61|Machine Design for AB Production Material Selection and Specifications Design Requirements ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection The design requirements Here is a list of the categories of the requirements to consider when selecting a material for a component or a joint between components: Performance requirements Reliability requirements Size, shape, and mass requirements Cost requirements Manufacturing requirements ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection The design requirements Here is a list of the categories of the requirements to consider when selecting a material for a component or a joint between components: Industry standards Government regulations Intellectual property requirements Sustainability requirements Below is an explanation of each category of requirements ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection Performance Requirements The performance requirements describe the attributes that the component or joint must have to function as required. The attributes can be described in terms of mechanical, electromagnetic, thermal, optical, physical, chemical, electrochemical, and cosmetic properties. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Reliability Requirements The reliability of a component or joint refers to its ability to function as required over a specific use period when exposed to a specific set of use conditions. A component or joint fails once the material degrades to the point where the component or joint no longer performs as required. The reliability requirements describe the use conditions to which the materials will be exposed and the expected response of the materials to the use conditions. Examples of use conditions are exposure to high temperatures, salt water (corrosion), and vibration. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Size, shape, and mass requirements The size, shape, and mass requirements for a component or joint will have a huge influence on the materials that can be used. Consider a component that must carry five amperes of current without heating up by more than 15o C above the ambient temperature. The electrical conductivity for a component with a 1 mm diameter must be about four times greater than the electrical conductivity for a component that can be 2 mm in diameter. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Size, shape, and mass requirements A bicycle frame that must weight 10 pounds must have frame tubes made of a lower density material compared to a 20 pound frame. For a component that must support 200 pounds, the yield stress for the material in a component that must be 0.20 inches diameter must be much greater compared to the material in a component that can be 0.50 inches in diameter. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection Cost requirements The cost to form a component or joint or purchase a component depends on 1) the materials that comprise a component or joint, 2) the manufacturing processes used to form a component or joint, 3) whether a component is custom made or purchased “off-the-shelf supplier”, 4) the quantity of materials or components being purchased and 5) quality problems associated with a material or component. If you want to reduce costs, consider what will be required from the materials engineering perspective to make manufacturing process changes that address items 2 and 5. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection Manufacturing requirements Companies may require that specific processes be used for fabricating components and building assemblies or sub-assemblies. Perhaps a company has internal manufacturing capabilities that must be used or a company is familiar and comfortable with component or joints fabricated using a familiar manufacturing process. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Manufacturing requirements Restrictions on the processes that can be used to build a product will restrict the materials that can be used to make components because the materials must be compatible with the processes and other materials used to make the product. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Manufacturing requirements For example, components to be joined using a specific welding, brazing, or soldering process must be made of materials that enable good joints to be formed using the specific joining process. This may exclude off-the-shelf components from one or more suppliers because their components are made of materials that are incompatible with the process. For a custom component, the restriction may require the use of certain materials in order to form a good joint. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Manufacturing requirements Restricting the manufacturing process to only familiar ones will restrict the options of materials that can be used to form a component or joint since many manufacturing processes are limited to processing certain materials. In some respects manufacturing constraints are acceptable, and may in fact be desirable, since the use of familiar processes and materials reduces the risk associated with a change or new product. ABE 61|Machine Design for AB Production  Material Selection and Specifications Material evaluation and process selection Manufacturing requirements However, in cases when a new product is significantly different than older products, the constraints of using specific manufacturing processes may seem to be a burden. ABE 61|Machine Design for AB Production Material Selection and Specifications Material evaluation and process selection ABE 61|Machine Design for AB Production References: MATERIALS SELECTION MECHANICAL DESIGN IN SECOND EDITION MICHAEL F. ASHBY Department of Engineering, Cambridge University, England https://www.theengineerspost.com/mechanical-properties-of-materials/ https://www.electrical4u.com/mechanical-properties-of-engineering-materials/ http://www.edu.xunta.gal/centros/cafi/aulavirtual/pluginfile.php/38297/mod_imscp/cont ent/1/metals_general_properties_extraction_and_classification_of_metals. http://www.mem.odu.edu/~bao/xmodulece3.pdf https://www.azom.com/article.aspx?ArticleID=4386 https://www.thomasnet.com/articles/custom-manufacturing-fabricating/types-of- manufacturing-processes/ https://www.astm.org/Standards/steel-standards.html https://www.astm.org/Standards/plastics-standards.html https://www.asabe.org/Publications-Standards/Standards-Development/National- Standards/Published-Standards https://www.sciencedirect.com/topics/engineering/material-selection-process https://www.imetllc.com/materials-selection-design-requirements/ ABE 61|Machine Design for AB Production END! ABE 61|Machine Design for AB Production