Lecture 4: Basic Material Properties

Lecture 4: Basic Material Properties

• Teacher: Dr. HaoTian Harvey Shi

• Subject: Mechanical & Materials Engineering

• Class: MME3348 – Manufacturing Processes 1

What We'll Learn

• Sort Materials: We'll put engineering materials into their six main groups.

• Design Needs: We'll learn what facts about materials are important when designing things.

• Main Material Traits: We'll understand central features of materials and how they fit with the material groups.

• How Materials Break: We'll look at the main ways materials can fail, like bending too much (yield), breaking apart (fracture), or wearing out over time (fatigue).

• Materials and Making Things: We'll connect material features to choosing the best ways to make products.

How to Make Things Well (Manufacturing Principles)

• Pick the Best Method: Choose the right way to make something based on:

  • How much it costs.

  • How many you need to make.

  • Things specific to the product.

• Make and Test Early Versions: Build and try out trial designs to check if they work right and meet safety rules.

• Check and Improve: Regularly meet with different teams to review the design and keep making changes until it's perfect.

• Rules for Easy Manufacturing (DFM):

  • Where it's Used: Design products for the place they will be used.

  • Keep it Simple: Make designs easy but still get the job done.

  • Putting it Together: Make sure parts can be easily lined up and connected.

  • Use Standard Parts: Use common parts and materials whenever you can.

  • Choosing Materials: Pick materials that are easy to get, not too expensive, and good for the making process.

  • Size Control: Control how exact the sizes need to be so parts fit together well.

Groups of Engineering Materials

• What Groups Have in Common: Materials in the same group tend to have similar features, like how they behave, how they are made, and what they are used for.

Main Ways Atoms Connect in Materials

• Types of Connections:

  • Ionic Bonding: Where one atom (metal) gives an electron to another atom (nonmetal), making them both charged and stick together.

    • Example: Sodium (NaNa^+}) and Fluorine (F$F^−$).

  • Covalent Bonding: Where atoms share electrons with each other.

    • Example: Hydrogen gas ($H_2$), or the way atoms are connected in a diamond.

  • Metallic Bonding: Where electrons are shared freely among many metal atoms, like a 'sea' of electrons. This makes metals good at carrying electricity and easy to shape.

What Each Material Group is Like

Metals

• What they are like: They can conduct heat and electricity really well, even at super cold temperatures.

  • They are tough (hard to break) and stiff (hard to bend). We measure toughness with fracture toughness ($K_{IC}$) and stiffness with Young's modulus ($E$).

  • Metals can be stretched into wires (ductile) or hammered into shapes (malleable). Their strength can vary a lot depending on what they're made of and how they're processed.

  • They can react with other things, which means they can rust or corrode easily.

Ceramics and Glasses

Ceramics

• What they are like: These are non-metal solids that are very stiff, hard, and don't wear down easily.

  • They stay strong in hot conditions and don't rust.

  • They block electricity (insulators) and usually break easily (brittle).

Glasses

• What they are like: These materials are not ordered like crystals (amorphous) and change from a stiff, glass-like state to a softer, rubber-like state at a certain temperature (glass transition temperature).

Polymers

• What they are and do: Made of long chains of molecules, which can be natural or man-made.

  • They are light with a low density ($<br>ho$).

  • Easy to mold and strong for their weight ($\frac{ au}{<br>ho}$).

  • They are less stiff than metals (Young's modulus, $E$, is much lower) and change properties with temperature.

  • They can slowly stretch or deform under constant weight over time (creep).

  • They can be partly or fully ordered (crystalline).

Elastomers (Rubbers)

• Key Features: - These are a type of polymer that feel rubbery at room temperature because their glass transition temperature is lower.

  • They can stretch a lot (5-700%) and snap back to their original form.

  • They are not stiff; their $E$ values are 500-5000 times less than metals.

  • Example: Rubber used in tires (vulcanized rubber).

Hybrids (Combined Materials)

• What they are: These are made by mixing two or more different materials to create strong, light, and stiff products.

  • They are usually costly, behave differently depending on the direction (anisotropic), and are hard to shape and connect.

  • Their features change a lot based on exactly what materials are combined, and we'll learn more about this later.

Important Note About Material Groups

• Keep in Mind: The features we talk about for each material group are general rules, and there can always be exceptions.

What Material Information You Need for Design

1. Guaranteed Values: These are reliable numbers for material features that are proven to be true.

2. How-to Guides: This includes instructions on how to shape, connect, and finish materials, ideas from what they've been used for before, and explanations for why things broke in the past (using words, pictures, charts).

3. Price and Market Details.

Example: Acrylonitrile-Butadiene-Styrene (ABS)

• Basic Features:

  • Density: 1200 $kg/m^3$ (how heavy it is for its size)

  • Young's Modulus: 1.1-2.9 GPa (how stiff it is)

  • Yield Strength: 19-51 MPa (how much force before it permanently deforms)

  • Tensile Strength: 28-55 MPa (how much force before it breaks when pulled)

  • Elongation: 15-40% (how much it can stretch before breaking)

  • Hardness (Vickers scale): 5.6-15 HV (how resistant it is to scratching or denting)

  • Fatigue strength: 11-22 MPa (how much force it can handle repeatedly before failing)

  • Glass Transition Temperature: 360-400°C (temperature where it becomes rubbery)

  • Price: About $1.10 per kilogram</p></li></ul></li><li><p><strong>What makes it special:</strong> It's tough, can bounce back, and is easy to shape. It's usually not see-through, but some clear types exist.</p><ul><li><p>Used in things like safety helmets and car parts.</p></li></ul></li><li><p><strong>Other names:</strong> Claradex, Cycolac, Lustran ABS, and more.</p></li></ul><h5 id="f362dd7e-fced-436a-873f-bb38f4f674fe" data-toc-id="f362dd7e-fced-436a-873f-bb38f4f674fe" collapsed="false" seolevelmigrated="true">Quick Review of Material Groups</h5><ul><li><p><strong>Why Material Groups Matter:</strong> The six main types of materials used in engineering are:</p><ul><li><p><strong>Metals:</strong> Can be stretched and are strong, good at conducting heat and electricity.</p></li><li><p><strong>Ceramics and Glasses:</strong> Hard, break easily, resist heat and rust.</p></li><li><p><strong>Polymers:</strong> Light, easy to shape, and block electricity.</p></li><li><p><strong>Elastomers (Rubbers):</strong> Can stretch a lot and return to shape.</p></li><li><p><strong>Hybrids:</strong> Mixes of materials with combined features.</p></li></ul></li><li><p><strong>What Info is Needed for Design:</strong> When designing, you need to look at how-to guides, reliable material values, and think about costs and what's available in the market.</p></li></ul><h5 id="5fe49783-5837-4881-a8e6-b7ef997022a3" data-toc-id="5fe49783-5837-4881-a8e6-b7ef997022a3" collapsed="false" seolevelmigrated="true">How Heavy Materials Are (Density)</h5><ul><li><p><strong>Measuring Density:</strong> You can find out how dense a material is using Archimedes' method. This involves measuring the weight of the material and how much liquid it displaces.</p></li><li><p><strong>Different Density Numbers:</strong> Materials have very different densities. For example, heavy metals like osmium are 22.5 grams per cubic centimeter ($g/cm^3$), while light materials like lithium are only 0.5$g/cm^3$$.

  How Much Materials Cost

  • Cost Differences: Prices for materials vary a lot, from very expensive ones like gold and platinum, to much cheaper ones like concrete, wood, and simple plastics.

  • Past Prices: Looking at how prices of metals and other resources have changed