Coursehero >> Canada >> UBC >> APSC 278

Course Hero has millions of student submitted documents similar to the one below including study guides, homework solutions, papers, exam answer keys and textbook solutions.

APSC278 Review by Warren Poole and Anoush Poursartip 1 Goals of the Course 1. To obtain a basic knowledge on the properties of alloys ceramics polymers composites 2. 3. 4. 5. To examine the effect of loading and temperature on the behaviour of materials To learn the basic techniques for measuring the properties of materials To study the structure of materials in order to understand their properties To learn how to manipulate or engineer the properties of materials 2 APSC278 by Warren Poole and Anoush Poursartip 2 1 Atomic Structure of Materials Identify the Building Blocks Metals crystals: BCC, FCC, HCP, BCT poly-crystalline materials x-ray diffraction Glasses (SiO4)4- tetrahedra Amorphous materials Ceramics NaCl, CsCl, ZnS Poly-crystalline materials Polymers chains of mer units, PE, PVC, etc. average molecular weight, DP sidegroups, branching, co-polymers amorphous, partially crystalline cross-linking, thermosets, elastomers APSC278 by Warren Poole and Anoush Poursartip 3 3 Mechanical Behaviour Stress and Strain Engineering True = F Ao T = F Ai l = L Lo T = ln i l o 4 APSC278 by Warren Poole and Anoush Poursartip 4 2 Mechanical Behaviour Elastic Response E is probably the most important material property in design Must also have a physical understanding stretching of atomic bonds entropy effect in elastomers = E Young's Modulus 5 APSC278 by Warren Poole and Anoush Poursartip 5 Mechanical Testing Cantilever Beam Test Easy technique to measure Young s Modulus FL3 = 3EI where I = moment of inertia, e.g. for rect. X-section = 13 ab 12 6 APSC278 by Warren Poole and Anoush Poursartip 6 3 Mechanical Behaviour Plastic Behaviour Plastic behaviour in metals and ceramics dislocation movement types of dislocation Plastic behaviour in Polymers sliding of chains past one another 7 APSC278 by Warren Poole and Anoush Poursartip 7 Mechanical Testing Necking and Fracture 8 APSC278 by Warren Poole and Anoush Poursartip 8 4 Mechanical Behaviour Brittle Behaviour Controlled by the crack population Griffith Equation K= 1 2 YF a WB 2 E s c = a Or stress intensity approach K = Y a Y is a function of (a/W) 9 APSC278 by Warren Poole and Anoush Poursartip 9 Mechanical Testing Compression Tests Compressive Strength e.g. concrete Higher than the tensile strength Therefore primarily loaded in compression! C C Cracking begins about half the ultimate strength Tips of the flaws experience tension and compression Flaws propagate stably to give general crushing These cracks propagate stably C Compression T T C Resolved shear 10 stress 10 APSC278 by Warren Poole and Anoush Poursartip 5 Mechanical Testing 3-point Bending Load Note the distribution of stress What are the effects of cracks? How does concrete fracture in 3pt bend? What effect does reinforcing steel have on the properties? What is the mechanism of wood fracture? 11 APSC278 by Warren Poole and Anoush Poursartip 11 Mechanical Testing Charpy V-notch Testing Pre-cracked specimen What is the effect of temperature on the samples? Brittle fracture Ductile fracture Ductile Brittle Transition Temperature Do all materials exhibit a DBTT? 12 APSC278 by Warren Poole and Anoush Poursartip 12 6 Mechanical Testing Fatigue and Fluctuating Stresses BEACHMARKS Bad design APSC278 by Warren Poole and Anoush Poursartip Good design 13 13 Strengthening of Metals 1. 2. 3. 4. 5. 6. When we strengthen metals we make dislocation motion more difficult Work hardening Increase the number of dislocations total grain boundary area higher, impedes dislocation motion presence of impurity atoms restricts dislocation motion strengthen by controlling the formation of precipitates, by ageing a solid solution Increase carbon, increase hardness and strength, decrease ductility carbon forms an the Fe3C intermetallic compound (see phase diagram) non-equilibrium microstructure formed in steel, cooled too rapidly for carbon to diffuse out of solid solution to form Fe3C Trapped carbon distorts the lattice 14 APSC278 by Warren Poole and Anoush Poursartip Grain size reduction Solid solution hardening Precipitation hardening Role of carbon in Steels Fe3C Strength of Martensite 14 7 Heat Treatment of Metals 1. Cold Working and Recrystallisation Cold working increases dislocation density increases hardness, strength, decreases ductility Recovery 1st stage of annealing process, restoration some of original properties, relief of some internal strain energy, reduction of dislocation density Recrystallisation deformed crystals are replaced by new generation of strainfree crystals time and temperature dependent Recovery and Recrystallisation 2. Solution Treatment and Precipitation Form solid solution by dissolving precipitate particles Quench to form supersaturated solid solution Age harden (solute atoms diffuse to sites favourable to precipitate out of second phase) Form austenite (heat into austenite range) Quench to form martensite Temper (reheating of hardened steel to decrease hardness) 15 APSC278 by Warren Poole and Anoush Poursartip 3. Austenitisation, quench and tempering 15 Effect of Temperature on Structures Metals and Ceramics Phase diagrams graphically present the relationships between temperature, composition and regions of phase stability under conditions of equilibrium Can achieve two phase microstructures we can determine the composition of those phases and we can calculate the fraction of the phases present Martensite formation Supersaturated solid solutions Non-equilibrium Cooling (Quenching) Polymers and Glasses Formation of Crystalline versus Amorphous phases Melting and Glass transition points Tempering of glass, residual compressive stresses on surface closes cracks 16 APSC278 by Warren Poole and Anoush Poursartip 16 8 Effect of Temperature on Mechanical Behaviour Metals What is the difference between cold working and hot working? creep time dependent deformation Glasses Supercooled liquids, gradual change from liquids to more viscous materials Brittle below the glass transition temperature Polymers Viscoelasticity Glass Transition temperature 17 APSC278 by Warren Poole and Anoush Poursartip 17 Concrete What are the setting and hardening reactions? What is the role of the major constituents? What is the role of water? Why do we use additives? 1. Increase the rate of hardening (Accelerators) Reduce cracking due to water (freeze/thaw cycles) Increase strength C3S C2S C3A C4AF alite belite aluminate ferrite 55 % 20 % 12 % 9% Hardening Setting Characteristic Normal Rapid hardening Low heat evolved Sulfate resistant Moderate IV and V Type* (ASTM) I III IV V II Compositional variation from type I C3S C2S C3A C3S C2S C3A C3A C3S 2. 3. 18 APSC278 by Warren Poole and Anoush Poursartip 18 9 Polymers Types of Polymer Thermoplastic becomes plastic upon heating melted by heat and cooled without appreciable change in properties. Characterisation number average and weight average molecular weights M n = xiMi M w = wiMi degree of polymerisation Thermosetting decompose upon heating chemical reactions (including crosslinking) take place while the resins are being moulded. heat resistant nn = Mn m nw = Mw m Elastomers withstand large elastic strains at ambient temperatures May be lightly crosslinked for stability How does crystallinity and molecular geometry influence the polymer properties? What are the significance of the glass transition, Tg, and melting, Tm, temperatures 19 19 APSC278 by Warren Poole and Anoush Poursartip Polymers Why are polymers sensitive to strain rate? What happens when we deform a semi-crystalline polymer? chain straightening breakdown on crystalline regions & 1 & 2 & 3 && & 3 < 2 < 1 How are polymers processed? What influences the the type of process chosen? Type of polymer thermoplastic etc. Temperature Tg and Tm Number of items that are to be produced, cost APSC278 by Warren Poole and Anoush Poursartip 20 20 10 Wood What is the importance of the microstructure? Natural composite Helically wound cells What is the relationship between cell wall thickness, density, strength and stiffness? 21 APSC278 by Warren Poole and Anoush Poursartip 21 Composites What is the role of the fibre and matrix? Isostress and Isostrain models Critical fibre length in discontinuous fibre composites Stress-Strain response Isostrain c = m = f Fibre Matrix c = m = f Isostress 22 APSC278 by Warren Poole and Anoush Poursartip 22 11 Anisotropy of Properties Isotropic metals Compressive strength > tensile strength Brittle materials glasses, ceramics and concrete Tensile strength > compressive strength Wood, composites Elastic properties depend on orientation of loading Wood, composites 23 APSC278 by Warren Poole and Anoush Poursartip 23 12

Find millions of documents here - Study Guides, Homework Solutions, Papers, Exam Answer Keys and more. Course Hero has millions of course related materials that will enable you to learn better, faster and get an A in all your courses.
Below is a small sample set of documents: