Materials Selection for Mechanical Design: Exploring the World of Materials � Background: the motivation � History – the evolution of materials � Materials and their attributes � The nature of materials data
Introduction � Design is… “…the process of translating a new idea or a market need into detailed information from which a product can be manufactured.” M. F. Ashby, “Materials Selection in Mechanical Design”, Idea or Need Design Product Invention Engineering Design Market need Industrial Design ME 474-674 Winter 2008 Slides 1 Intro -2
Types of Design � Original Design � New idea or working principle � e.g. CD replacing magnetic tape � Adaptive or Development Design � Takes existing product and seeks an incremental advance in performance through a refinement in working principle. � e.g. beverage cans, automobiles,… � Variant Design � Change in scale/dimension without change of function � e.g. desktop to laptop computer ME 474-674 Winter 2008 Slides 1 Intro -3
Vocabulary of Design � Design problems are open ended - no single correct answer � Design is an iterative process � Products are technical systems composed of assemblies and components � The design objective must be formulated as a “need statement” “A device for performing task x is needed” � But must not specify a way of satisfying the need “Must be solution neutral” ME 474-674 Winter 2008 Slides 1 Intro -4
Example Need Design objective: “A device is needed to pull the cork from wine bottle” Not solution neutral – pulling specifies the solution ME 474-674 Winter 2008 Slides 1 Intro -5
Possible solutions Revised Design Objective : “a device is required to allow access to wine in a corked bottle with convenience, at modest cost, without contaminating wine…” � Screw to transmit prescribed load to cork � Slender elastic blade that will not buckle when driven between the cork and the bottle-neck � Thin, hollow needle, stiff and strong enough to penetrate cork Concepts ME 474-674 Winter 2008 Slides 1 Intro -6
Possible solutions � Embodiments of one concept Embodiments Levered pull Spring assisted pull Geared pull Direct pull ME 474-674 Winter 2008 Slides 1 Intro -7
Slides 1 Intro -8 One solution ME 474-674 Winter 2008
Slides 1 Intro -9 ME 474-674 Winter 2008 Other Concepts
Air pressure cork popper Air Pressure Bottle Opener - Automatic Cork Popper No tugs, no pulls, no corkscrews - no groans! This advanced approach to uncorking wines is almost effortless. Just push the needle into the cork, pump and... pop! The injected air causes the cork to lift itself right out of the bottle ME 474-674 Winter 2008 Slides 1 Intro -10
Butler’s friend � This device consists of a pair of thin, narrow, flexible metal blades mounted in parallel to a flattened loop of a handle. � In storage the blades are protected by a metal or plastic sheath. � Remove the sheath, and you'll notice that one blade is slightly longer than the other. � Insert the longer blade first between cork and glass (about 1/4 inch); then insert the shorter blade opposite. � Rocking the handle back and forth, you gently push down each blade in turn about 1/4 inch at a time until the frame of the handle rests on the top of the cork. Then simply twist and lift. � The cork comes out with ease and can be removed from between the puller's blades in one motion--no need to untwist as from a helix. ME 474-674 Winter 2008 Slides 1 Intro -11
Why Materials and Process Selection In Design? Engineers make things to make life better. � They make them out of materials using processes. � Materials have played a role in human life since the beginning of � civilization. The progress of civilization has been recorded by the materials. � Stone age, bronze age, iron age etc. � At this time we have over 160,000 materials available to us. � Materials selection is a systematic elimination of those that are not � suitable to arrive at an optimum material for the particular application. Materials selection is an integral part of any design processes � The transition from the conceptual design to physical reality. � ME 474-674 Winter 2008 Slides 1 Intro -12
Materials and Process Selection In Design � What do engineers need to know to do this successfully? � A perspective of the world of materials and processes � An understanding material properties and their origins � An ability to select those that best meet requirements of a design � Access to information and tools for comparison and selection ME 474-674 Winter 2008 Slides 1 Intro -13
General Classification of Materials � Metals Iron, Copper, Aluminum, Zinc, Nickel, Titanium, Silver, Gold, etc. � and their alloys Steel, Brass, Bronze, etc. � Ceramics Porcelain, China, Glass, Silicon Carbide, Boron Nitride, Aluminum � Oxide, etc. � Polymers Polyethylene, PVC, Teflon , Nylon, Plexiglas, Bakelite , Epoxy, � Polyesters, Melamine, Neoprene , Silicone � Electronic Materials Silicon, Germanium, Gallium-Arsenide � � Composites Concrete, FRP, MMC, CMC, Asphalt, Wood � ME 474-674 Winter 2008 Slides 1 Intro -14
The world of structural materials Steels Cast irons Al-alloys Metals, alloys Cu-alloys Ni-alloys Ti-alloys PE, PP, PC PS, PET, PVC Alumina PA (Nylon) Si-carbide Polymers Ceramics Composites Polyester Sandwiches Si-nitride Phenolic Ziconia Hybrids Epoxy Lattices Segmented Isoprene Soda glass Butyl rubber Borosilicate Elastomers Glasses Natural rubber Silica glass Silicones Glass ceramic EVA ME 474-674 Winter 2008 Slides 1 Intro -15
Slides 1 Intro -16 History – the evolution of materials ME 474-674 Winter 2008
Slides 1 Intro -17 Comparison of Materials ME 474-674 Winter 2008 Metals
Metals Bonding: Metallic bonds – Delocalized electrons Structure: Crystalline Advantages Disadvantages � Relatively high moduli (stiff) � Failure by fatigue � Can be made strong by alloying � Most susceptible to or working environmental attack � (corrosion and oxidation) � Nominally ductile � Relatively high toughness � Paramagnetic or ferromagnetic � Good electrical conductors ME 474-674 Winter 2008 Slides 1 Intro -18
Metals Metal Examples of application Ferrous Metals Carbon Steels Utensils, construction, automotive, transmission towers … Stainless Steels Off shore drilling rigs, naval construction, chemical transport, food preparation, medical instruments Cast Irons Cylinders, pistons, motor blocks, construction, wear resistant materials Light Alloys Aluminum Alloys Aerospace, construction, transport, packaging, electrical conductors Magnesium Alloys Aerospace, automotive, sporting equipment Titanium Alloys Aerospace, chemical industry Copper Alloys Copper Electrical conductors Bronze Heat exchangers, chemical industry, maritime industry Brass Pressure vessels, fittings Nickel Alloys Aerospace, currency ME 474-674 Winter 2008 Slides 1 Intro -19
Slides 1 Intro -20 Ceramics and Glasses ME 474-674 Winter 2008
Ceramics and Glasses Bonding: Ionic & Covalent Bonding – Directional & Strong Structure: Crystalline or amorphous Disadvantages Advantages � Brittle � High moduli (stiff) � High strength � Statistical spread in strength � Abrasion resistant � Strength in compression ~ � High melting point 15x strength in tension � Resist corrosion and � Notch sensitive oxidation � More difficult to design with � Transparent than metals or polymers � Good electrical insulators ME 474-674 Winter 2008 Slides 1 Intro -21
Ceramics and Glasses Ceramics Examples of application Bulk Ceramics Hydrated ceramics Construction (cement, plaster…) Rocks Construction Fired ceramics (pottery, Construction, electrical insulators, bricks …) hygienic applications, household Fibers (glass, carbon …) Reinforcements in polymer composites Ceramic fibers and powders Particles Reinforcements in polymer and metal (alumina, silicon Composites carbide, magnesia) Abrasive Particles Cutting wheels, polishing cloths Industrial Ceramics Alumina, Silicon High temperature furnaces, heat Nitride, Silicon shields Carbide… Glasses Windows, food preparation ME 474-674 Winter 2008 Slides 1 Intro -22
Slides 1 Intro -23 Polymers and Elastomers ME 474-674 Winter 2008
Polymers and Elastomers Bonding: Covalent and secondary bonding Structure: Amorphous or partially crystalline Disadvantages Advantages � Creep at room temp. � Can have high strength � Properties change a great � High elastic deformation deal with temperature (flexible) � Low melting points � Low coefficient of friction � Low moduli � Corrosion resistant � Difficult to recycle � Easy to form � Can be colored ME 474-674 Winter 2008 Slides 1 Intro -24
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