Topic 1 Engineering Materials & Properties v1.1
Page 1: Engineering Materials and Properties
1. Topic Overview
1.1 Types of engineering materials
1.2 Introduction to atomic structure of solids
1.3 Basic Structure and bonding of materials
1.4 Properties of materials
1.5 Mechanical properties
Page 2: Types of Engineering Materials
1.1 Types of Engineering Materials
1.1.1 Metals
Metals are sourced from the earth's crust, which contains minerals that hold a high percentage of specific metals.
Key categories of engineering materials include: Metals, Polymers, Ceramics, and Composites.
Page 3: Metals Characteristics
1.1.1 Metals
Characterized as crystalline in structure.
Properties:
Opaque and lustrous.
Able to permanently change shape under external forces.
Excellent electrical and thermal conductivity.
Page 4: Metal Strength and Alloys
1.1.1 Metals (cont.)
Additional characteristics:
High strength, stiffness, and ductility.
Alloys are formed when two or more metals are combined.
Examples include copper, steel, aluminum, gold, brass, bronze, super alloys.
Common applications: car bodies, tin cans, conducting wires.
Page 5: Polymers
1.1.2 Polymers
Characteristics:
Light, low electrical and thermal conductivity.
Resistant to atmospheric attacks.
Low strength and unsuitable for high-temperature applications.
Structure: Long molecular chains formed on a backbone of carbon atoms.
Applications: Carrier bags, plumbing pipes, hoses, tires.
Page 6: Polymer Repeat Unit and Applications
1.1.2 Polymers (cont.)
Polymer | Applications |
|---|---|
Polyethylene (PE) | Electrical wire insulation, flexible tubing, squeeze bottles |
Polypropylene (PP) | Carpet fibers, ropes, liquid containers (cups, buckets), pipes |
Page 7: Ceramics
1.1.3 Ceramics
Composition: Combination of one or more metals with non-metallic elements (e.g., oxygen, nitrogen, carbon).
Properties:
Hard, porous, brittle with good thermal and insulating properties.
High compressive strength, poor plasticity.
Examples: Refractories, glasses, concrete, silica.
Applications: Glassware, electrical insulators, cutting tools.
Page 8: Composites
1.1.4 Composites
Description: Made from two or more materials combined, each differing significantly in properties.
Functionality: One material acts as a matrix to hold another material, acting as reinforcement.
Examples: Plywood (light and strong), cermets (hard and abrasive-resistant).
Page 9: Example of Composites
Example of Composites
Straw + Mud = Brick
Page 10: Topic Overview
1. Topic Overview Repeat
1.1 Types of engineering materials
1.2 Introduction to atomic structure of solids
1.3 Basic Structure and bonding of materials
1.4 Properties of materials
1.5 Mechanical properties
Page 11: Atomic Structure Overview
1.2 Introduction to Atomic Structure
An atom: Smallest unit of matter, retains all chemical properties of an element.
Molecules form when atoms combine and interact, creating solids, gases, or liquids.
Example: Water is formed from hydrogen and oxygen atoms.
Page 12: Atomic Particles
1.2.1 Atomic Structure
Atoms consist of:
Protons: Positively charged particles in the nucleus.
Neutrons: Uncharged particles in the nucleus.
Electrons: Negatively charged particles in outer electron shells.
Properties vary based on the arrangement of these particles.
Page 13: Atomic Examples
1.2.1 Atomic Structure (cont.)
Example: Hydrogen atom (H) has one proton, one electron, and no neutrons.
Atomic number and mass number help determine atomic structure.
Structure of elements (like helium) consists of protons and neutrons in the nucleus; electrons orbit the nucleus.
Page 14: Protons, Neutrons, and Electrons
1.2.2 Atomic Mass
Protons and neutrons have similar mass; protons are positively charged.
Neutrons do not influence charge but increase atomic mass.
Electrons have negligible mass, typically ignored when calculating atomic mass.
Page 15: Electron Contribution to Charge
1.2.2 Atomic Mass (cont.)
Electrons contribute to the atom's charge, creating balance with protons' positive charge.
Page 16: Topic Overview Repeat
1. Topic Overview Repeat
1.1 Types of engineering materials
1.2 Introduction to atomic structure of solids
1.3 Basic Structure and bonding of materials
1.4 Properties of materials
1.5 Mechanical properties
Page 17: Valence Electrons
1.3.1 Valence Electrons
Definition: Located in the outermost energy level (valence shell) of an atom.
These electrons are loosely held compared to others and dictate the chemical behavior of elements in reactions.
Page 18: Atomic Bonding
1.3.2 Bonding of Atoms
Ionic Bonds: Occur through electron transfer between atoms, creating ions that bond via coulombic attraction.
Three primary atomic bonds:
Ionic bonds
Covalent bonds
Metallic bonds
Page 19: Ionization
An atom loses electrons to become positively charged, while gaining electrons results in a negative charge.
Example: Sodium chloride (NaCl) is formed through ionic bonding.
Ionization: Atoms with few valence electrons tend to lose them, becoming unstable.
Page 20: Covalent Bonds
1.3.2 Bonding of Atoms (cont.)
Covalent Bonds: Form between atoms near each other in the periodic table; they share electrons to form bond pairs.
Multiple bonds can form if electrons are shared with other atoms or themselves.
Page 21: Metallic Bonds
1.3.2 Bonding of Atoms (cont.)
Metallic bonds arise when metals have one or more valence electrons that create a negative electron cloud.
This cloud is mobile and holds metal atoms together through mutual attraction to positively charged metal ions.
Page 22: Bond Characteristics
A regular arrangement of metal ions occurs due to mutual repulsion and attraction to the electron cloud, forming strong metallic bonds.
Page 23: Videos on Bonding
Videos on Bonding
Ionic and Covalent Bonds (9.54 mins)
Metallic Bond (4.40 mins)
Properties illustrated:
Electronic movement in copper when a voltage is applied.
Ductility of copper explained through its atomic arrangement.
Page 24: Topic Overview Repeat
1. Topic Overview Repeat
1.1 Types of engineering materials
1.2 Basic Structure and bonding of materials
1.3 Introduction to atomic structure of solids
1.4 Properties of materials
1.5 Mechanical properties
Page 25: Properties of Materials
1.4 Properties of Materials
Selection Considerations
Match material properties to service conditions:
Physical Properties: Density, melting point, thermal conductivity, etc.
Mechanical Properties: Strength, toughness, durability, etc.
Technological Properties: Machinability, formability, etc.
Page 26: Types of Properties
Types of Properties (cont.)
Chemical Properties: Resistance to oxidation and solvents.
Economic Properties: Cost and availability.
Aesthetic Properties: Appearance and finishing.
Page 27: Physical Properties
1.4 Physical Properties
Density: Mass per unit volume, higher density with closely packed atoms.
Melting Point: Temperature where solids turn to liquids, influenced by atomic bonding strength.
Thermal Conductivity: Ability to conduct heat effectively.
Page 28: Mechanical Properties Overview
1.4 Mechanical Properties
Mechanical properties reflect how a material interacts under applied forces, resulting in elastic or plastic deformation.
Page 29: Subcategories of Mechanical Properties
1.4 Mechanical Properties (cont.)
Key mechanical properties include:
Strength: Tensile strength, yield point, etc.
Rigidity: Modulus of elasticity.
Durability: Toughness, hardness, fatigue resistance, etc.
Page 30: Topic Overview Repeat
1. Topic Overview Repeat
1.1 Types of engineering materials
1.2 Introduction to atomic structure of solids
1.3 Basic Structure and bonding of materials
1.4 Properties of materials
1.5 Mechanical properties
Page 31: Mechanical Properties Defined
1.5 Mechanical Properties
1.5.1 Tensile Properties
1.5.2 Malleability
1.5.3 Hardness
1.5.4 Impact Strength
Page 32: Tensile Properties
1.5.1 Tensile Properties
Extracted from stress-strain curves during applying pulling force.
Page 33: Key Metrics in Tensile Properties
1.5.1 Tensile Properties (cont.)
Modulus of Elasticity
Yield Stress
Tensile Strength
Percentage Elongation
Reduction in Area
Page 34: Tension and Compression
Tension/Compression feedback
External forces can stretch (tension) or squeeze (compression) materials.
For example, gold is highly malleable, can be hammered into gold leaf.
Page 35: Engineering Stress
Engineering Stress
Formula:[ \sigma = \frac{F}{A_o} ]Where F = Applied Load, ( A_o ) = original cross-sectional area.
Page 36: Engineering Strain
Engineering Strain
Formula:[ \epsilon = \frac{L_o - L_f}{L_o} ]Strain represents the change in length relative to original length.
Page 37: Work Example of Engineering Stress/Strain
Engineering Stress/Strain Example
Utilizes formulas to calculate stress and strain based on initial and final measurements.
Page 38: Work Example Continuation
Engineering Stress/Strain Example Continuation
Further examples illustrating the application of formulas for engineering stress and strain.
Page 39: Topic Overview Repeat
1. Topic Overview Repeat
1.1 Types of engineering materials
1.2 Basic Structure and bonding of materials
1.3 Introduction to atomic structure of solids
1.4 Properties of materials
1.5 Mechanical properties
Page 40: Tensile Test Overview
Tensile Test Overview
Conducted on a test piece subjected to increasing tensile force using a tensile machine.
Page 41: Tensile Test Process
Tensile Test Process (cont.)
During the test piece elongates, experiencing localized deformation, leading to fracture while measuring stress and strain.
Page 42: Stress-Strain Curve
A Typical Stress-Strain Curve
Represents the relationship between stress and strain experienced by a material.
Page 43: Elastic and Plastic Deformation
Elastic and Plastic Deformation
Elastic Limit: Material returns to original shape when stress is removed.
Plastic Deformation: Results in permanent material changes beyond the elastic limit.
Page 44: Maximum Tensile Stress
Maximum Tensile Stress and Fracture
Points of fracture are indicated on the stress-strain curve, demonstrating material failure under stress.
Page 45: Modulus of Elasticity
Modulus of Elasticity and Calculation
Calculating the elasticity ratio of applied stress to strain within the material's elastic limit.
Page 46: Yield Point
Yield Stress and Proof Stress
Describes conditions of material yielding during the stress-strain relationship, determining defined stress points.
Page 47: Yield Point Continuation
Upper and Lower Yield Points
An explanation of yield points and how they contribute to material behavior during stress tests.
Page 48: Proof Stress vs Yield Stress
Proof Stress Explained
Proof stress measured at specified strain; commonly used when yield point isn't clearly defined.
Page 49: 0.2% Proof Stress
0.2% Proof Stress Calculations
Methodology for calculating proof stress as a measure of material strength.
Page 50: Proof Stress Calculation Continued
Accurate Proof Stress Measurement
Steps for calculating proof stress with relevant formulas based on strain measurements.
Page 51: Maximum Load
Maximum Load and Local Deformation
Describing the maximum tensile load supported by the material before fracture occurs.
Page 52: Percentage Elongation
Ductility Measures
Percentage elongation used as a measure of ductility in materials prior to fracture.
Page 53: Percentage Reduction in Area
Percentage Reduction in Area
Another ductility measure based on changes in cross-sectional area during stress.
Page 54: Topic Overview Repeat
1. Topic Overview Repeat
1.1 Types of engineering materials
1.2 Basic Structure and bonding of materials
1.3 Introduction to atomic structure of solids
1.4 Properties of materials
1.5 Mechanical properties
Page 55: Mechanical Properties Defined Repeat
1.5 Mechanical Properties
1.5.1 Tensile Properties
1.5.2 Malleability and Ductility
1.5.3 Hardness
1.5.4 Impact Strength
Page 56: Malleability and Ductility
1.5.2 Malleability and Ductility
Malleability: Ability to deform permanently without fracture from compressive forces.
Ductility: Ability to deform permanently without fracture from tensile forces.
Page 57: Malleability Overview
Malleability and Ductility (cont.)
Malleability allows for deformation in multiple directions; ductility allows stretching, twisting, or bending.
Not all malleable materials display ductility; for instance, clay can be shaped but breaks easily.
Page 58: Topic Overview Repeat
1. Topic Overview Repeat
1.1 Types of engineering materials
1.2 Basic Structure and bonding of materials
1.3 Introduction to atomic structure of solids
1.4 Properties of materials
1.5 Mechanical properties
Page 59: Mechanical Properties Defined Repeat
1.5 Mechanical Properties
1.5.1 Tensile Properties
1.5.2 Malleability
1.5.3 Hardness
1.5.4 Impact Strength
Page 60: Hardness Definition
1.5.3 Hardness
Hardness: Material's ability to resist plastic deformation, scratching, and wear.
Example: Diamond is the hardest known material.
Page 61: Hardness Testing Methods
Hardness Testing Methods
Multiple scales: Rockwell, Vickers, Brinell hardness tests.
Each method offers unique measurements based on applied loads and indentation methodologies.
Page 62: Brinell Hardness Scale
1.5.3 Hardness (cont.)
Brinell Hardness Scale: Utilizes a tungsten carbide ball indentation method.
Page 63: Brinell Hardness Calculation
Brinell Hardness Calculation
Calculating Brinell Hardness Number (BHN) based on the indentation diameter against load applied.
Page 64: Brinell Test Considerations
Considerations in Brinell Testing
Advantages: Applicable to a range of materials, accuracy despite imperfections.
Limitations: May damage material on harder samples.
Page 65: Vickers Hardness Scale
1.5.3 Hardness (cont.)
Vickers Hardness Scale: Involves a diamond pyramid indenter.
Page 66: Vickers Hardness Calculation
Vickers Hardness Calculation
Hardness calculated using the mean diagonal of the indentation made by the diamond pyramid.
Page 67: Vickers Hardness Advantages
Vickers Hardness Advantages
Results are geometrically consistent and applicable on various materials, including thin components.
Page 68: Rockwell Hardness Scale
Rockwell Hardness Scale
Hardness measurement based on the depth of indentation made under varying loads with steel balls or diamond cones.
Page 69: Rockwell Hardness Methodology
Rockwell Hardness Methodology (cont.)
Steps include applying a minor load, then a major load, taking readings from the indicator.
Page 70: Rockwell Hardness Advantages
Rockwell Hardness Advantages
Quick, simple testing with direct readings, appropriate for a range of materials.
Page 71: Topic Overview Repeat
1. Topic Overview Repeat
1.1 Types of engineering materials
1.2 Basic Structure and bonding of materials
1.3 Introduction to atomic structure of solids
1.4 Properties of materials
1.5 Mechanical properties
Page 72: Mechanical Properties Defined Repeat
1.5 Mechanical Properties
1.5.1 Tensile Properties
1.5.2 Malleability and Ductility
1.5.3 Hardness
1.5.4 Impact Strength
Page 73: Impact Strength Overview
1.5.4 Impact Strength
Defined as the energy a material can absorb before fracturing, indicating toughness.
Tough materials can absorb more energy compared to brittle ones.
Page 74: Impact Tests Comparison
Comparison of Impact Tests
Izod Test: 135-160 J of energy; specimen held in cantilever manner.
Charpy Test: 150-300 J; specimen supported at ends, typically hit in the center.
Page 75: Fracture Surface Observation
Fracture Surface Characteristics
Brittle Material: Sudden breakdown, granular texture.
Ductile Material: Fibrous fracturing, damping before complete break.
Page 76: Fracture Surfaces Examination
Fracture Surfaces Examination (cont.)
Analysis of fracture surfaces can help identify material behavior under stress.
Page 77: Crystal Behavior in Fractures
Fracture Surface Appearance
Distinguishing between brittle and ductile fractures based on crystal deformation patterns.
Page 78: Specific Material Behavior
Material Behavior Examples
Copper shows no transition between ductile to brittle failure.
Austenitic stainless steel demonstrates high toughness, maintaining ductility across temperatures.