slide1 n.
Skip this Video
Loading SlideShow in 5 Seconds..
MATERIALES II 2012 PowerPoint Presentation
Download Presentation


1 Vues Download Presentation
Télécharger la présentation


- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. MATERIALES II 2012 Docentes: • Prácticas / Visitas: • Talleres/ Laboratorios del CAB: práctica de mecanizado; soldadura (TIG, manual); templabilidad de aceros; metalografía; fundición. • IISA (INVAP Ingeniería) • INVAP Satelital • Locales: • - Dr. (Ing. Nuc.) Graciela BERTOLINO (JTP) • Ing. Mec. Hugo SOUL (Ayd. 1ra) • Dr. Alejandro YAWNY (Prof. Asoc.) Martes 8:30 - 12:30 Horarios*: Viernes8:30 - 12:30 ProfesoresVisitantes*: horarios a definir • Visitantes: • Alberto LUCAIOLI (UNS, Bahía Blanca) ConformadoPlástico • Roberto HADDAD (CNEA, CAC) Corrosión Introduction

  2. ContenidosCurricularesIngenieríaMecánica: 1° CUATRIMESTRE MecánicaRacional Matemática Laboratorio I Introd. al Cómputo 2° CUATRIMESTRE Termodinámica MétodosNuméricos Mecánica de los Sólidos FísicaModerna 4° CUATRIMESTRE Transf. de Energía y Masa Materiales II Sists. Electroméc. y Máq. Eléc Electrónica Electrotecnia 3° CUATRIMESTRE Mecánicade Fluidos Materiales I Dinám. de Sists. y Control Mecanismos 5° CUATRIMESTRE ProyectoIntegrador I Laboratorio II MáquinasTérmicas e Hidráulicas. DiseñoMecánico Seg. e Hig. en Plantas y Labs. Optativa 6° CUATRIMESTRE ProyectoIntegrador II Econ. y Gestión de Proyectos GestiónAmbiental Optativa Introduction

  3. Objetivos de la Materia: Brindarconocimientosquefaciliten el proceso de Selección de un Material para la fabricación de un componentecapaz de cumplir con unadeterminadaFunción Introduction

  4. FUNCTION transmit a load, heat, contain pressure, store energy, etc. at minimum cost, weight, or maximum efficiency, safety The central problem of materials selection in mechanical design: MATERIAL SHAPE interaction between function, material, process and shape PROCESS Formability Machinability Weldability Heat tretability Precision Tolerances Surface quality Defects (pores, cracks) Cost Introduction

  5. * Role of materials in mechanical design Types of Design Original design: (completely new idea) involves new working principles (the ballpoint pen, the CD). - New materials can offer new, unique combination of properties wich enable original design: high purity Si transistor; high purity glass optical fibres. - Sometimes the new material suggest the product but often the product demands development of new materials: turbine technology  Hight Temperature Alloys (Superalloys); nuclear technology  Zr Alloys; space technology  Light Alloys This is the driving force behind the development of new materials. Adaptive or developmental design:takes an existing concept and seeks an incremental advance in performance (the evolution of a product) often possible by developments in materials: polymers for metals in household appliances; carbon fibre for wood in sports goods. Variant design:the change of scale or dimension or shape without change of function. Change of scale may require change of materials scaling up of boilers (cooper to steels), pressure vessels, planes (balsa wood models to Al full-scale planes) Introduction

  6. Market need Design requirements Design Tools Viability Analysis Approximate Analysis Optimization Methods Detailed Analysis Materials data needs Data for ALL materials low precision data Data for a SUBSET of materials higher data precision Data for ONE material highest precision and detail CONCEPTUAL explore working principles EMBODIMENT define general layauot and scale Generic properties Materials Selection Charts ASM Handbooks Smithells: Metals Reference Book DETAIL optimize form, manufacture and assembly Supplier Critical components: run your own test ! PRODUCT SPECIFICATION THE DESIGN PROCESS Introduction

  7. Polymers HYBRIDS (COMPOSITES) Metals Ceramics & Glasses MATERIALS UNIVERSE Introduction

  8. Low carbon (mild) steel • Medium carbon steels • High carbon steels Plain carbon steels • Low alloy steels • Tool steels • Stainless steels Ferrous Alloys Alloy steels • Grey cast irons • White cast irons • Malleable alloys • Nodular cast irons Cast irons • Aluminium alloys • Magnesium alloys • Titanium alloys Light alloys • Copper alloys • Lead alloys • Nickel alloys (incl.Superalloys) Heavy alloys Nonferrous Alloys • Molybdenum alloys • Tantalum alloys • Tungsten alloys Refractory metals • Gold alloys • Silver alloys • Platinum alloys Precious metals METALS Introduction

  9. The most popular structural material CARBON STEELS based on the Fe- Fe3C phase diagram Introduction

  10. Fe-C-Si !! Phase diagram Carbon Steels * to improve hardenability: up to (in total) 7 % Mn, Cr, Ni, Mo in low alloy steels: TTT diagrams “shift” to the right * to provide solution strengthening:alloying elements in low alloy steels in substitutional solution give additional hardening and also W and Co in tool steels * to allow precipitation hardening:carbide formers (Mo2C, W2C, VC) in high speed steels: 1%C, 0.4%Si, 0.4%Mn, 4%Cr, 5% Mo, 6%W, 2% V and 5% Co (traditionally made from 1%C, 0.3%Si, Mn in the quenched plus tempered state to cut mild steel but “run the temper” problem. Above 500-600 C: Fe3C dissolves but Mo2C, W2C and VC form fine precipitates making steels even harder!!, allowing high cutting speeds) Alloying: what for? * to improve corrosion resistance (Cr) and stabilize austenite (Ni): stainless steels (SS 18/8: 18Cr 8Ni wt.% ) Introduction

  11. More on Steels: SteelMATTER Underlying Metallurgy Strength Equilibrium Fe-C diagram Toughness Fe-C phase diagram: Lever rule Hardenability Transformation diagrams Introduction

  12. More on Al Alloys: Generic Aluminium Alloys: Matter Module AluMatter + Phase Diagrams Modules Introduction

  13. Properties of the Generic Metals Structure INSENSITIVE vs. Structure SENSITIVEPROPERTIES SENSITIVE to ….MICROSTRUCTURE  Thermomechanical Condition! Introduction

  14. Poyethylene, PE; partly crystalline; Tubing, films, bottles, cups, electrical insulation, packaging • Polypropylene, PP; partly crystalline; Same uses as PE, but lighter, stiffer, more resistant to sunlight • Polytetrafluorethylene, PTFE; partly crystalline; Teflon; Good high temperature polymer with very low friction and adhesion characteristics; Non-stick saucepans, bearings, seals • Polystyrene, PS; amorphous; Cheap molded objects, toughened with butadiene to make high impact polystyrene (HIPS), foamed with pentane to make common packaging (“Telgopor”, Argentina) • Polyvinylchloride, PVC; amorphous; Architectural uses, tubing, artificial leather, hoses, clothes • Polymethylmethacrylate, PMMA; amorphous; Perspex, lucite, transparent sheet and mouldings, aircraft windows • Nylon 66; partly crystalline when drawn; Textiles, ropes, moldings Thermoplastics • Epoxy; amorphous; matrix in Fibreglass composites, adhesives, expensive! • Polyester; amophous; matrix in Fibreglass composites, laminates, cheaper than epoxy! • Phenol-formaldehyde; amoprphous; Bakelite, Formica; rather brittle • Urea-formaldehyde; amoprphous; replace Bakelite, Electrical fittings • Melamine-formaldehyde;amorphous; replace Bakelite, Tableware Elastomers or rubbers Thermosets or resins • Polyisoprene; amorphous; Natural rubber • Polybutadiene; amophous; Synthetic rubber • Polychloroprene; amoprphous; Neoprene, oil resistant rubber used for seals • Cellulose; crytalline • Lignin; amophous • Protein; partly crystallines Natural polymers POLYMERS Introduction

  15. Introduction

  16. Soda-lime glass; 70SiO2, 10 CaO, 15 Na2O; windows, bottles, easily formed and shaped • Borosilicate glass; 80SiO2, 15 B2O, 5 Na2O; pyrex; cooking and chemical glassware; high temperature strength, low coefficient of thermal expansion, good thermal shock resistance Glasses Vitreous ceramics • Dense alumina;Al2O3 • Silicon carbide, nitride;SiC, Si3N4; • Sialons; Si2AlON3 • Zirconia (PSZ); ZrO2 + 5 wt.% MgO High performance engineering ceramics Electronic materials Cement and concrete Rock and minerals • Limestone (Marble); CaCO3 • Sandstone; SiO2 • Granite; Aluminium silicates • (building, foundations) • Ice; H2O • Ferrites • Ferroelectrics • Semiconductors • Superconductors • Portland cement; CaO + SiO2 + Al2O3 • Porcelain; electrical insulators • China Pottery;artware and tableware tiles • Brick; construction and refractory use • Made form clays: hydrous aluminosilicates such as Al(Si2O5)(OH)4 mixed with other inert minerals. Final State: crystalline phases (sislicates) in a glassy matrix based on SiO2 CERAMICS and GLASSES Introduction

  17. Concrete: cement + aggregates • Macadam: gravel in bitumen • Cemented carbide: Tungsten carbide particles in cobalt matrix (WC +Co) • fillers: usually added to lower costs and increase wear resistance Particulate composites Engineering composites • GFRP: glass fibre reinforced polymers • CFRP: carbon fibre reinforced polymers • MMC: metal matrix composites Fibrous composites • Plywood: uniform properties in the plane of the sheet (contrary to anisotropic wood!) • NEW: FibreMetal laminates • Arall • Glare (used in the Airbus 380 fuselage) Lamellar composites Natural (biological) composites • wood: fibrous chain of cellulose in a matrix of lignin • bone / teeth: hard inorganic crystals (hydroxyapatite) in a tough organic constituent (collagen) COMPOSITES Introduction

  18. difficult to grip in TENSION !: Strength measured in BENDING (MOR: modulus of rupture) Typical Mechanical Behaviours BRITTLE DUCTILE Introduction

  19. How to compare Materials at the Conceptual Design Stage?: Materials Properties Charts Introduction

  20. Materials Selection Charts Selection of materials: - usually dictated by a combination, or several combinations, of properties (E1/n / r, sf / r, E / sf). - Condense a large body of information in a compact form! - Allows comparison /selection of materials at the conceptual design level: guide lines (log-log plot). Example: Velocity of sound: v = (E/r)1/2 - range: 50 to 104 m/s - Al and Glass: high v (low E) - Wood vs. Steel Introduction

  21. Loading geometry affects material selection ! Example: The combination of properties which maximise stiffness-to-weight ratio and the strength-to-weight ratio for various loading geometries Combination of Properties (Merit Index) depends on the mode of loading Introduction

  22. - sf different meanings ! - Strength not so well defined as E (metals!): vertical extensions of the “bubbles” (strength is a structure sensitive property!!!, compare with E) - Metals: dislocations, Peierls stress, metallic bonding; Ceramics: ionic or covalent bonding; Polymers: relative slippage of polymer chains or segments; Glasses: breakage of strong bonds. Use of the Strenght - Density Chart: - lightweight plastic design (minimum weight design of ties, beams, plates and yield - limited design of moving components where low inertial forces are important ) Introduction

  23. The Merit Index is E1/2 / r for Optimun Stiffness design of beams The same for plates (E1/3 / r), etc. Introduction

  24. Optimum stiffness case: For Ties (E/r): Steels: (27) Al: (25) GFRP 50 % uniaxial in polyester: (24) KFRP 60% uniaxial: (54) CFRP 58 % uniaxial C in epoxy: (126) For Beams (E1/2 / r): Steels: (1.8) Al: (3) (principal airframe material!!) GFRP 50 % uniaxial in polyester: (3.5) KFRP 60% uniaxial: (6.2) CFRP 58 % uniaxial C in epoxy: (9) (increasingly being used in aircraft structures) For Plates (E1/3 / r): Steels: (0.76) Al: (1.5) (principal airframe material!!) GFRP 50 % uniaxial in polyester: (1.8) KFRP 60% uniaxial: (3) CFRP 58 % uniaxial C in epoxy: (3.8) (floor panels, flaps, tail planes) Introduction

  25. Optimum strenght case: composites are always better than metals (even for ties) For Ties (sY/ r): Steels: (128) Al: (179) GFRP 50 % uniaxial in polyester: (620) KFRP 60% uniaxial: (886) CFRP 58 % uniaxial C in epoxy: (700) For Beams: …… For Plates: …… composites are always better than metals, even for ties ! Introduction

  26. Combination of Properties (Merit Index) depends on the mode of loading Loading geometry affects material selection ! But we were considering only the material (shape was pre-defined) SHAPE ? ! The combination of properties which maximise stiffness-to-weight ratio and the strength-to-weight ratio for various loading geometries Introduction

  27. FUNCTION transmit a load, heat, contain pressure, store energy, etc. at minimum cost, weight, or maximum efficiency, safety The central problem of materials selection in mechanical design: MATERIAL SHAPE interaction between function, material, process and shape Formability Machinability Weldability Heat tretability Precision: Tolerances Surface quality Defects (pores, cracks) Cost PROCESS Manufacturing Processes Cards We were discussing MATERIAL, then SHAPE, now …. PROCESS Introduction

  28. combining material with macroscopic shape combining material with microscopic shape combining material, microscopic and macroscopic shape Selection of Material and Shape Ways to increase mechanical efficiency Introduction

  29. K: torsional moment of area (K = polar moment of area J for circular cross section): Q: equivalent to Ixx/ym for Torsion Macroscopic Shape A: cross section area Ixx: second moment of area about the axis of bending ym: distance from neutral axis of bending to the outer surface Introduction

  30. Elastic bending and torsion: shape enters through the second moment of area: Material: can be thought of as having properties but no shape. Component or structure: is a SHAPED MATERIAL A SHAPE FACTOR is defined as a dimensionless number which characterises the efficiency of a section shape, regardless of scale, in a given mode of loading Examples of definitions of SHAPE FACTORS Elastic extension: no shape factor is needed! Introduction

  31. Definitions: Stiffness: Bending: Torsion: Strength: Bending: Torsion: Introduction

  32. Performance Index including Shape Introduction

  33. reinforcement matrix strong and stiff constituent embedded in softer constituent Example of Material Development Metal Matrix Composites: MMCs = metallic matrix + ceramic reinforcement Introduction

  34. Aim: reduce thermal distortion of an Al alloy component Candidates: BN and SiC (fibres, particles); both have lower a than Al ! However, the correct Merit Index is the ratio: K / a MMCs design: Composite material: Al + ceramic additions to reduce thermal distortion Conclusion: SiC good but BN not Introduction

  35. Monofilaments Whiskers / Fibres Particulate Usual types of MMCs microstructures continuously reinforced discontinuously reinforced Introduction

  36. Al alloy + Saffil short fibres Reinforcement: Saffil fibres (Al2O3 (d) + 3-4 wt.-% SiO2) 100 mm “Saffil” short fibre reinforced MMCs Saffil: Safe filament Introduction

  37. Squeeze Casting Process Eidgenössische Materialprüfungs und Forschungsanstalt (CH) Introduction

  38. Squeeze Casting Infiltration and pressurization 1750 kN (100 MPa) MMC Casting Dim.: 150 x 115 x 35 mm Weight: approx. 1700 g Introduction

  39. 15 vol.% Applications of Saffil reinforcedAl-alloys SFR in automobiles Creep: Stress vs. Life Stress [MPa] Time to fracture [h] Introduction

  40. additional comments …. USEFUL APPROXIMATE SOLUTIONS TO STANDARD DESIGN PROBLEMS Modelling is a key part of design. In the early stage (conceptual design), approximate modelling establishes whether the concept will work at all, and identifies the combination of material properties which maximise performance. At the embodiment stage, more accurate models brackets the forces, the displacements, the velocities and the dimensions of the components. And in the final stage, modelling gives precise values for the stresses, strains and failure probability in key components. Many simple components have been modelled already and many more-complex components can be modelled approximately by idealising them as one of these. THERE IS NO NEED TO REINVENT THE BEAM OR THE COLUMN OR THE PRESSURE VESSEL; THEIR BEHAVIOUR UNDER ALL COMMON TYPES OF LOADING HAS ALREADY BEEN MODELLED: Many problems of conceptual design can be analysed, with adequate precision, by patching together solutions like those given here; and even the final detailed analysis of non-critical components can be tackled in the same way. Examples of results of modelling of some standard problems: Introduction

  41. Elastic Deflection of Beams Introduction

  42. Failure of Beams Introduction

  43. Torsion of Shafts Introduction

  44. Buckling of Columns Introduction