16103 Material Science PDF

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16103 – Material Science

Table of Cont Contents ents Lecture 1 – Introduction ................................................................................................... 4 Types of Materials ...............................................................................................................................4 Common Material: Hot Rolled Steel ....................................................................................................4 Common Material: Cold formed steel..................................................................................................4 Common Material: Stainless Steel .......................................................................................................4 Common Material: Aluminium ............................................................................................................4 Common Material: Concrete................................................................................................................4 Common Material: Timber...................................................................................................................5 Common Material: Masonry................................................................................................................5 Less Common Materials: Glass ............................................................................................................5

Lecture 2 – Timber ........................................................................................................... 6 Natural Variability in Timber ...............................................................................................................6 Type of Tree and Types of Timber ........................................................................................................6 Australian Hardwoods .........................................................................................................................7 Australian Commercial Softwoods.......................................................................................................7 Cross Section of a Tree and Functions .................................................................................................8 Moisture Content .................................................................................................................................8 Seasoning .............................................................................................................................................8 Timber Defects (Natural) – Knots ........................................................................................................8 Timber Defects (Natural) – Shake ........................................................................................................9 Timber Defects (Natural) – Wane ........................................................................................................9 Timber Defects (Natural) – Defect due to poor seasoning ............................................................... 10 Commercial Timber – Sawing Patterns............................................................................................. 10 Identification of Timber .................................................................................................................... 11 Eco Certification Stamps ................................................................................................................... 11 Timber Material Properties............................................................................................................... 12 Stress vs Strain .................................................................................................................................. 12 Hooke’s Law ...................................................................................................................................... 13 Young’s Modulus............................................................................................................................... 13 Creeping Timber................................................................................................................................ 13 Timber and Fire ................................................................................................................................. 14 Timber Under Attack......................................................................................................................... 14 Preservative treatments ................................................................................................................... 14

16103 – Material Science Timber Joints ..................................................................................................................................... 15

Lecture 3 – Steel .............................................................................................................16 Making Steel Alloys ........................................................................................................................... 16 Typed of Steel (Historic) .................................................................................................................... 16 Typed of Steel (Current) .................................................................................................................... 16 Standard Section Sizes ...................................................................................................................... 16 Testing Steel ...................................................................................................................................... 17 Defining Proof Stress......................................................................................................................... 18 Stainless Steel ................................................................................................................................... 18 Durability .......................................................................................................................................... 18 Protecting Steel ................................................................................................................................. 18 Weathering steels ............................................................................................................................. 19 Fatigue .............................................................................................................................................. 19 Steel and Creep/Stress Relaxation .................................................................................................... 19 Fire Protection Steel .......................................................................................................................... 19

Lecture 4 - Metals ...........................................................................................................19 Materials at the Atomic Level ........................................................................................................... 19 Compounds ....................................................................................................................................... 19 Bonding and Materials ..................................................................................................................... 20 Ionic Bonding .................................................................................................................................... 20 Covalent Bonds (CO2, CH4, Ethanol, Iodine) ...................................................................................... 20 Covalent bonds ................................................................................................................................. 20 Metallic Bonds .................................................................................................................................. 21 Aluminium in Structures.................................................................................................................... 21 Notation for Aluminium Alloys ......................................................................................................... 21 Aluminium and Fire ........................................................................................................................... 22

Lecture 5 – Concrete Mortar............................................................................................23 Definitions ......................................................................................................................................... 23 Manufacture of Cement.................................................................................................................... 23 Types of Cement................................................................................................................................ 23 Storage of Cement ............................................................................................................................ 23 Constituents of Concrete................................................................................................................... 24 Setting and hardening ...................................................................................................................... 24 Desired Properties of Hardened Concrete ........................................................................................ 24 Strength of Concrete ......................................................................................................................... 25 Strength of Concrete – Flexural (beam) Testing ............................................................................... 25

16103 – Material Science Factors that Affect Strength of Concrete .......................................................................................... 25 Testing Workability of concrete ........................................................................................................ 25 Shrinkage of concrete ....................................................................................................................... 26 Mixing of Concrete ............................................................................................................................ 26 Defects – Creep and Spalling of Concrete ......................................................................................... 27 Mortars ............................................................................................................................................. 27 GFRP – Glass Fibre Reinforced Polymer (ALTERNATE SOLUTION) .................................................... 27

Lecture 6 – Masonry .......................................................................................................28 Clay Bricks ......................................................................................................................................... 28 Concrete blocks ................................................................................................................................. 28 Geometry .......................................................................................................................................... 28 Bond patterns ................................................................................................................................... 28 Bricks ................................................................................................................................................. 29 Production of Bricks .......................................................................................................................... 29 Brick types ......................................................................................................................................... 29

Lecture 8 – Glass .............................................................................................................30 Glass Properties ................................................................................................................................ 30 Chemical Makeup of Glass (soda-lime glass) ................................................................................... 30 Making glass ..................................................................................................................................... 30 Type of Glass ..................................................................................................................................... 30 Typical Sizes of Fully Tempered Glass (Limited by Toughening Line) ............................................... 31 Other Types of Glass ......................................................................................................................... 31 Engineering Design Considerations .................................................................................................. 31 Cautious ............................................................................................................................................ 32 Glass and Solar Gain / “Greenhouse” Effect ..................................................................................... 32 Single vs Double Glazing ................................................................................................................... 32

16103 – Material Science

Lecture 1 – IIntroduction ntroduction Types of Materials -

Natural – wood, straw, bamboo, stone Manufactured – glass, concrete New – fibre composites, plastics, ETFE Heritage (old) – cast/wrought iron Common materials – Steel (G** - is the guaranteed minimum yield of the steel in MPa)

Common Material: Hot Rolled Steel -

Mild Steel (G250 – G450) (most common steel) – relatively cheap, ductile and easy to weld High Yield Steel (G500+) – used for rebar, harder to source and welding is difficult Very High Strength Steel (G700+) – used for pre-stressing

Common Material: Cold formed steel -

Typical strength grades 450 – 550 MPa Used for lightweight applications – sheds, carpets, purlins, decks

Common Material: Stainless Steel -

Used for special applications, corrosion sensitive areas Typical bolts are 700MPa yield strength Grade 316 for marine Shiny grade 304 Difficult to weld and more brittle than regular steel

Common Material: Aluminium -

Lightweight, corrosion resistant, good strength Special purpose structures, facades Grade 6061-T6 – very high grade, structural elements Grade 6063-T5 – used for curtain walling mullions Expensive + V High embodied energy content Issues: long-term fatigue problems and welding difficulties

Common Material: Concrete -

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Contents of concrete: • Cement • Fine aggregate • Coarse aggregate • Water Strengths of concrete: • 28 days to cure and reach 100% of strength • Slump test – measures the consistency of fresh concrete • Strength range from 20MPa to 60MPa • 7 days = 2/3 of full 28-day strength

16103 – Material Science

Common Material: Timber -

Softwoods (pine, spruce, Douglas fir) are used in most structures Hardwoods (oak, ash, mahogany) less eco-friendly, longer time to grow, more expensive Timber needs to be strength graded visually or by machine Lightweight, attractive and easy to work with Good strength to weight ratio If well sources, very eco-friendly Variable properties – defects, knots High anisotropic – meaning the properties change with direction along the object (grain vs across the grain)

Common Material: Masonry -

Standard brick: 76mm x 230mm x 110mm Block: 200mm x 400mm x 90/140/190mm

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Facing Bricks look nice but strength differs Engineering Bricks not so pretty but guaranteed strength Masonry should always be weaker than bricks to avoid cracking under small movements

Less Common Materials: Glass -

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Contents in glass: • Glass is 60-75% silica • 12-18% soda • 5-12% Lime Classed as amorphous solid (it is in between liquid and solid states) Density 2600kg/m3 Mod. of elasticity 70 to 74 kN/mm2 Brittle and poor tensile strength

16103 – Material Science

Lecture 2 – Ti Timber mber Natural Variability in Timber -

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Moisture content is the measure of available water in a piece of timber, increasing in strength the less the moisture content • Each piece of timber to be used in structures, has to have an average moisture content at the time of fabrication, within 3% of the equilibrium value Equilibrium moisture content value is where the timber neither loses nor gains moisture from the surrounding atmosphere Different strengths (grain vs perpendicular to grain) • Good compression and tension strength performance in the direction of the grain. • Low compression and tension strength perpendicular to the grain Load duration (short-term vs long-term loads) • Duration of load has an impact on strength and stiffness • Strength of a timber member is reduced as the duration of the load increases • Load carrying capacity is higher for members subjected to rapidly applied and very short term • As moisture content is increased, the time to failure for a particular stress level is reduced and creep effects are much greater Defects in growth • Defects includes knots, slope of grain • Defects in timber are determined by testing of in-grade specimens • Location of defects is important as they degrade the strength properties Determining strength of different timbers • A timber’s strength represents the ability of that timber to maintain stress without failure • S1 – S7 for unseasoned timber (green) • S1 – S8 for seasoned timber (dry) • Seasoned and unseasoned timber have different strength groupings due to differences in the mechanical properties of defect-free timber Insect/Rot/Fungal attack • Any piece of timber containing abnormal defects such as insect damage, fungal decay, rot results in significant decrease in strength

Type of Tree and Types of Timber -

Endogenous (inward growing) Exogenous (outward growing)

16103 – Material Science

Australian Hardwoods -

Majority of native timbers harvested in NSW are from hardwood species Hardwood timber is visually attractive, dense, strong and durable Used for – flooring, decks, pergolas, power poles, wharves, bridges

Australian Commercial Softwoods -

NSW produced one third of Australia’s softwood timber Most commonly the Radiata Pine:

16103 – Material Science

Cross Section of a Tree and Functions

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Pith – core of tree about which first wood growth takes place Heart wood – provides mechanical rigidity to tree Sapwood – store food, transports moisture from roots to leaves Cambium Layer – cell division happens increasing girth of tree Inner Bark – conducts food synthesised by leaves to the rest of tree Outer Bark – dry dead tissue provides shield to rest of tree Growth Rings – due to cycles of growth and rest Rays – store and conduct food to layers between pith and bark

Moisture Content -

“Green” timber holds water inside its cells (free water) and within its cell walls (bound water) Fibre Saturation Point (FSP) – all free water removed but cell walls still saturated Above the FSP – most physical and mechanical properties stay constant Below the FSP – variation in MC cause considerable changes to props such as weight, strength elasticity, shrinkage

Seasoning -

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‘the controlled drying of timber is known as seasoning’ Two methods of seasoning: 1. Air seasoning – boards are stacked and divided by narrow pieces of wood so that the air can circulate freely about each board. Stack is slanted to facilitate drainage of rain 2...